Non-Pharmacological Therapies

*Spinal Cord Injury Therapy*

[130] Hall ED, Wolf DL. A pharmacological analysis of the pathophysiological mechanisms of posttraumatic spinal cord ischemia. Journal of Neurosurgery. 1986;**64**:951- 961. DOI: 10.3171/jns.1986.64.6.0951

[129] Liu XZ, Xu XM, Hu R, Du C, Zhang SX, McDonald JW, et al. Neuronal and glial apoptosis after traumatic spinal cord injury. The Journal of Neuroscience. 1997;**17**:5395-5406

[131] Young W, Koreh I. Potassium and calcium changes in injured spinal cord.

transplantation of olfactory ensheathing glia promotes sparing/regeneration of supraspinal axons in the contused adult rat spinal cord. Journal of Neurotrauma. 2003;**20**:1-16. DOI: 10.1089/08977150360517146

[133] Verdu E, Garcia-Alias G, Fores J, Lopez-Vales R, Navarro X. Olfactory ensheathing cells transplanted in lesioned spinal cord prevent loss of spinal cord parenchyma and promote functional recovery. Glia. 2003;**42**: 275-286. DOI: 10.1002/glia.10217

[134] Ahmad M, Abo Shaiqah A,

Alshehri AS, Alotaibi AM. Accentuated rehabilitation recovery from spinal cord injury in rats through increased behavioral activity besides minocycline treatment: A nursing care perspective. JOJ Nurse Health Care. 2018;**5**:555674. DOI: 10.19080/JOJNHC.2018.05.555674

Brain Research. 1986;**365**:42-53

[132] Plant GW, Christensen CL, Oudega M, Bunge MB. Delayed

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**95**

**Chapter 6**

**Abstract**

Noninvasive Modalities Used in

*Filipe O. Barroso, Alejandro Pascual-Valdunciel,* 

*Jozsef Laczko and José L. Pons*

meet specific needs of SCI patients.

**1. Introduction**

the nervous system [5].

Spinal Cord Injury Rehabilitation

*Diego Torricelli, Juan C. Moreno, Antonio Del Ama-Espinosa,* 

In the past three decades, research on plasticity after spinal cord injury (SCI)

has led to a gradual shift in SCI rehabilitation: the former focus on learning compensatory strategies changed to functional neurorecovery, that is, promoting restoration of function through the use of affected limbs. This paradigm shift contributed to the development of technology-based interventions aiming to promote neurorecovery through repetitive training. This chapter presents an overview of a range of noninvasive modalities that have been used in rehabilitation after SCI. Among others, we present repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), surface electrical stimulation tools such as transcutaneous electrical spinal cord stimulation (tcSCS), transcutaneous electrical nerve stimulation (TENS), and functional electrical stimulation (FES), as well as its integration with cycling training and assistive robotic devices. The most recent results attained and the potential relevance of these new techniques to strengthen the efficacy of the residual neuronal pathways and improve spasticity are also presented. Future efforts toward the widespread clinical application of these modalities include more advances in the technology, together with the knowledge obtained from basic research and clinical trials. This can ultimately lead to novel customized interventions that

**Keywords:** spinal cord injury, rehabilitation, noninvasive modalities, functional

Spinal cord injury (SCI) is an event that affects the quality of life of patients as a consequence of affected sexual function, impaired sensory and motor function, including bowel and bladder control, walking, eating, grasping, pain, and spasticity [1–3]. For many years, SCI has been considered irreversible [4]. However, research on plasticity after SCI has opened new paths and generated a shift in rehabilitation of SCI patients in the past three decades: its former focus on learning compensatory movements to regain function gradually changed to restoration of function through repetitive movement training combined with the stimulation of

electrical stimulation, transcranial magnetic stimulation, exoskeletons

#### **Chapter 6**

## Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation

*Filipe O. Barroso, Alejandro Pascual-Valdunciel, Diego Torricelli, Juan C. Moreno, Antonio Del Ama-Espinosa, Jozsef Laczko and José L. Pons*

#### **Abstract**

In the past three decades, research on plasticity after spinal cord injury (SCI) has led to a gradual shift in SCI rehabilitation: the former focus on learning compensatory strategies changed to functional neurorecovery, that is, promoting restoration of function through the use of affected limbs. This paradigm shift contributed to the development of technology-based interventions aiming to promote neurorecovery through repetitive training. This chapter presents an overview of a range of noninvasive modalities that have been used in rehabilitation after SCI. Among others, we present repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), surface electrical stimulation tools such as transcutaneous electrical spinal cord stimulation (tcSCS), transcutaneous electrical nerve stimulation (TENS), and functional electrical stimulation (FES), as well as its integration with cycling training and assistive robotic devices. The most recent results attained and the potential relevance of these new techniques to strengthen the efficacy of the residual neuronal pathways and improve spasticity are also presented. Future efforts toward the widespread clinical application of these modalities include more advances in the technology, together with the knowledge obtained from basic research and clinical trials. This can ultimately lead to novel customized interventions that meet specific needs of SCI patients.

**Keywords:** spinal cord injury, rehabilitation, noninvasive modalities, functional electrical stimulation, transcranial magnetic stimulation, exoskeletons

#### **1. Introduction**

Spinal cord injury (SCI) is an event that affects the quality of life of patients as a consequence of affected sexual function, impaired sensory and motor function, including bowel and bladder control, walking, eating, grasping, pain, and spasticity [1–3]. For many years, SCI has been considered irreversible [4]. However, research on plasticity after SCI has opened new paths and generated a shift in rehabilitation of SCI patients in the past three decades: its former focus on learning compensatory movements to regain function gradually changed to restoration of function through repetitive movement training combined with the stimulation of the nervous system [5].

The term neural plasticity describes the ability of the nervous system to adapt a new functional or structural state in response to intrinsic or extrinsic factors [6]. Thus, plasticity encompasses the underlying mechanisms that lead to a spontaneous return or recover of motor, sensory and autonomic functions to different degrees. The concept of plasticity at the cellular level can be tracked back to Ramon y Cajal's work, who suggested that modification of synaptic connections could play a very important role in memory [7]. After that, the work of Donald Hebb was very important to the concept of long-term potentiation (LTP), namely by suggesting that two neurons that fire together and are close enough may grow some connections or undergo metabolic changes that increase their ability to communicate [8]. This happens because chemical synapses have the ability to change their strength [9].

Sensory information from Ia afferent fibers (transmitting information about muscle activity and movement) play an essential role in inducing functional and morphological changes that lead to the maturation of the brain and the spinal cord [9], independently of the SCI level and whether it is complete or incomplete [10]. Thus, activity-dependent plasticity refers to the changes in the central nervous system (CNS) associated with movement [9] and reflects one of the basic forms of learning in humans [11]. These neural changes happen throughout the life span at both the brain and spinal cord level. However, not all plasticity is beneficial: adverse changes may also appear [12]. This is known as maladaptive plasticity and encompasses events such as excessive plasticity associated with some disease symptoms like focal dystonia, spasticity, and chronic pain. Current SCI rehabilitation is based on task-specific programs aiming at promoting neurorecovery through beneficial activity-dependent plasticity and avoiding maladaptive plasticity [6].

This chapter summarizes the main effects on motor and functional recovery, as well as spasticity and pain, when using noninvasive modalities in the rehabilitation of SCI patients, either in the research or the clinical setting. Some of these techniques aim at stimulating different levels of the central (brain or spinal cord) and peripheral nervous system, while others combine some sort of stimulation with devices that may assist and allow for repetitive motor training (e.g., hybrid exoskeletons and FES driven cycling).

#### **2. Brain stimulation**

Recent research has shown that even complete SCI patients may preserve some residual pathways connecting supraspinal and spinal circuits [13]. Given that these patients may preserve muscle activity below the level of injury, target rehabilitation for SCI also includes modalities that stimulate the brain. This might strengthen the efficacy of the residual neural pathways and, therefore, improve volitional control after SCI [14]. This section describes two different types of noninvasive brain stimulation (NIBS): repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS). Both techniques have been used in the research and clinical setting aiming at improving motor and functional recovery, as well as spasticity and pain after SCI [4].

#### **2.1 Repetitive transcranial magnetic stimulation (rTMS)**

Transcranial magnetic stimulation (TMS) is a form of noninvasive brain stimulation in which short magnetic fields are generated by a coil in order to induce electric current pulses in the brain, which can then elicit depolarization and action potentials in cortical neurons (see **Figure 1**). Since its first application in humans in 1985, TMS has become a standard electrophysiological technique to

**97**

*Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation*

assess the excitability of the corticospinal circuitry, due to its usability and ability to directly activate brain structures without causing harm to the subject. The most extended protocol applies single TMS pulses to activate motor cortex at a specific area where topographic projections of a group of muscles are represented. This cortical activation elicits action potentials that propagate until reaching the muscles, inducing a motor evoked potential (MEP), which can be measured by

*The magnetic field generated by the TMS coil will induce electric current pulses in the brain, which can* 

Repetitive transcranial magnetic stimulation (rTMS) is a form of TMS where several TMS pulses are applied sequentially in order to induce long-term changes in the targeted neural pathways. The underlying physiological mechanism of rTMS lies in the repeated activation of a network of synapses that may lead to long-term potentiation (LTP) or long-term depression (LTD) of those synapses [4]. The induction of long-term changes in neural circuits using rTMS can be applied to revert the effects of neurological disorders. For instance, rTMS received FDA

Due to its ability to induce long-term changes in neural systems, rTMS has been also applied in patients with motor disorders as a modality to modulate the activity of residual (cortical, subcortical, and corticospinal) pathways and thus promote functional recovery [2]. Moreover, rTMS has been applied in a wide range of protocols, with varying frequencies and intensities of stimulation, or even the number of pulses and sessions, among others. The main stimulation protocols explored so far

• Theta burst stimulation (TBS) consists of three 50 Hz pulses delivered in

blocks at 200-ms interval (5 Hz). Intermittent TBS (iTBS) involves the delivery of TBS for 2 s, followed by a resting period of 8 seconds, for a total of 3 min; this is hypothesized to facilitate LTP [15]. On the other hand, continuous TBS

• QuadroPulse (qQPS) applies four high-frequency pulses repeated every 5 s. The facilitator or inhibitory excitability effects depend on the inter-pulse intervals.

approval and has become a promising treatment for major depression.

*DOI: http://dx.doi.org/10.5772/intechopen.83654*

electromyography (EMG) [2].

*elicit depolarization and action potentials in cortical neurons.*

**Figure 1.**

may be encompassed in the following:

(cTBS) applied in 40 s blocks promote LTD.

*Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation DOI: http://dx.doi.org/10.5772/intechopen.83654*

#### **Figure 1.**

*Spinal Cord Injury Therapy*

etons and FES driven cycling).

well as spasticity and pain after SCI [4].

**2.1 Repetitive transcranial magnetic stimulation (rTMS)**

**2. Brain stimulation**

The term neural plasticity describes the ability of the nervous system to adapt a new functional or structural state in response to intrinsic or extrinsic factors [6]. Thus, plasticity encompasses the underlying mechanisms that lead to a spontaneous return or recover of motor, sensory and autonomic functions to different degrees. The concept of plasticity at the cellular level can be tracked back to Ramon y Cajal's work, who suggested that modification of synaptic connections could play a very important role in memory [7]. After that, the work of Donald Hebb was very important to the concept of long-term potentiation (LTP), namely by suggesting that two neurons that fire together and are close enough may grow some connections or undergo metabolic changes that increase their ability to communicate [8]. This happens because chemical synapses have the ability to change their strength [9]. Sensory information from Ia afferent fibers (transmitting information about muscle activity and movement) play an essential role in inducing functional and morphological changes that lead to the maturation of the brain and the spinal cord [9], independently of the SCI level and whether it is complete or incomplete [10]. Thus, activity-dependent plasticity refers to the changes in the central nervous system (CNS) associated with movement [9] and reflects one of the basic forms of learning in humans [11]. These neural changes happen throughout the life span at both the brain and spinal cord level. However, not all plasticity is beneficial: adverse changes may also appear [12]. This is known as maladaptive plasticity and encompasses events such as excessive plasticity associated with some disease symptoms like focal dystonia, spasticity, and chronic pain. Current SCI rehabilitation is based on task-specific programs aiming at promoting neurorecovery through beneficial

activity-dependent plasticity and avoiding maladaptive plasticity [6].

This chapter summarizes the main effects on motor and functional recovery, as well as spasticity and pain, when using noninvasive modalities in the rehabilitation of SCI patients, either in the research or the clinical setting. Some of these techniques aim at stimulating different levels of the central (brain or spinal cord) and peripheral nervous system, while others combine some sort of stimulation with devices that may assist and allow for repetitive motor training (e.g., hybrid exoskel-

Recent research has shown that even complete SCI patients may preserve some residual pathways connecting supraspinal and spinal circuits [13]. Given that these patients may preserve muscle activity below the level of injury, target rehabilitation for SCI also includes modalities that stimulate the brain. This might strengthen the efficacy of the residual neural pathways and, therefore, improve volitional control after SCI [14]. This section describes two different types of noninvasive brain stimulation (NIBS): repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS). Both techniques have been used in the research and clinical setting aiming at improving motor and functional recovery, as

Transcranial magnetic stimulation (TMS) is a form of noninvasive brain stimulation in which short magnetic fields are generated by a coil in order to induce electric current pulses in the brain, which can then elicit depolarization and action potentials in cortical neurons (see **Figure 1**). Since its first application in humans in 1985, TMS has become a standard electrophysiological technique to

**96**

*The magnetic field generated by the TMS coil will induce electric current pulses in the brain, which can elicit depolarization and action potentials in cortical neurons.*

assess the excitability of the corticospinal circuitry, due to its usability and ability to directly activate brain structures without causing harm to the subject. The most extended protocol applies single TMS pulses to activate motor cortex at a specific area where topographic projections of a group of muscles are represented. This cortical activation elicits action potentials that propagate until reaching the muscles, inducing a motor evoked potential (MEP), which can be measured by electromyography (EMG) [2].

Repetitive transcranial magnetic stimulation (rTMS) is a form of TMS where several TMS pulses are applied sequentially in order to induce long-term changes in the targeted neural pathways. The underlying physiological mechanism of rTMS lies in the repeated activation of a network of synapses that may lead to long-term potentiation (LTP) or long-term depression (LTD) of those synapses [4]. The induction of long-term changes in neural circuits using rTMS can be applied to revert the effects of neurological disorders. For instance, rTMS received FDA approval and has become a promising treatment for major depression.

Due to its ability to induce long-term changes in neural systems, rTMS has been also applied in patients with motor disorders as a modality to modulate the activity of residual (cortical, subcortical, and corticospinal) pathways and thus promote functional recovery [2]. Moreover, rTMS has been applied in a wide range of protocols, with varying frequencies and intensities of stimulation, or even the number of pulses and sessions, among others. The main stimulation protocols explored so far may be encompassed in the following:


Regardless of its incipient stage and current limitations, rTMS has become a promising approach for SCI rehabilitation, not only to improve motor function but also to decrease spasticity and neuropathic pain. This technique enables targeting and promoting long-term changes in neural pathways, by exploiting the plastic properties that may facilitate function recovery. Improvements seem to be present when higher rTMS stimulus intensities are used [2]. On the other hand, the few studies that investigated the effects of rTMS on spasticity in iSCI patients reported some reduction in the clinical symptoms of spasticity [2]. Moreover, the few studies that tested the effect of rTMS on neuropathic pain reported some reductions in the clinical symptoms of pain [2].

Notwithstanding, these results hold a great variability, are not reproducible in all patients, and are limited to certain clinical assessment scales or neurophysiological measurements. Several constraints can explain current limitations of the rTMS application in SCI patients. First, there is a shortage of studies providing evidences of sustained benefits of rTMS therapy beyond conventional treatments. Besides the different stimulation protocols and parameters applied, type of lesion and nonuniform assessment methodologies hamper the development of consistent evidences. Although evidences so far do not suggest any harm to the subjects, safety issues should be also considered when using rTMS in SCI patients, especially because of the high threshold needed to evoke motor responses in the impaired pathways [16].

More research is needed to provide robust evidence that can support the use of rTMS as an alternative to standard therapies. In addition to bigger sample sizes used in each study, researchers should also test the same (or very similar) stimulation parameters and protocols to provide reproducible results. Finally, it is critical to better understand the pathophysiology of neural structures affected by rTMS to design optimal and customized protocols that might boost beneficial neural changes coupled with functional recovery after SCI [2].

#### **2.2 Transcranial direct current stimulation (tDCS)**

Transcranial direct current stimulation (tDCS) is a technology that delivers continuous low current stimulation (1–2 mA) via paired anode and cathode electrodes over the scalp [4, 14, 17] (see **Figure 2**). This modality is usually combined with motor training to promote activity-dependent plasticity [14]. tDCS may change brain function by causing neurons resting potential to depolarize or hyperpolarize. Depolarization happens when positive stimulation (anodal tDCS) is delivered, which increases neural excitability and, therefore, neural firing. Cathodal tDCS (negative stimulation) causes hyperpolarization and, thus, decreases neural firing [4].

**99**

motor function.

**Figure 2.**

combined with robotic gait training [22].

*Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation*

This technique is still in the early stage. To our knowledge, just seven studies have examined improvements in motor function after SCI related to the use of tDCS: four studies evaluated its effect on upper limb function [18–21] and three studies evaluated the tDCS effect on lower limb function and gait [22–24]. All these studies used anodal stimulation and showed improvements in upper and lower limb

*Transcranial direct current stimulation delivers continuous low current stimulation by applying a positive* 

*(anodal) or negative (cathodal) current via paired electrodes over the scalp.*

The use of tDCS has led to improvements in pinch force, manual dexterity, and force modulation when combined with repetitive practice [18]. Other study reported that stimulation intensity affects functional outcomes when tDCS was delivered at rest: increased corticospinal excitability to affected muscles was obtained when using 2 mA stimulation, but not 1 mA, in nine chronic SCI patients [19]. Another study also reported gains in hand motor function after a single session of 2mA tDCS, though no improvements were described in clinical scales [20]. When combining tDCS with robot-assisted arm training, SCI patients improved arm and hand function post-treatment and at the 2-month follow-up [21].

The three studies that evaluated the tDCS effect on lower limb function and gait showed improved motor function [22–24]. However, one of these studies combined tDCS with robotic gait training and also showed no significant differences between these improvements and those verified in the group who received sham stimulation

tDCS is an attractive noninvasive modality option for the treatment after SCI: it is affordable and does not present substantial adverse events (when present, they included redness of the skin, sleepiness, headache, and neck pain [4]). However, further research is still needed to provide robust evidence that support the use of tDCS to improve motor

In the recent years, spinal cord electrical stimulation (SCS) has arisen as a promising tool to modulate corticospinal excitability and modify the motor output in

function and to be used in the clinical setting as a long-term strategy after SCI.

**3. Transcutaneous spinal cord stimulation (tcSCS)**

*DOI: http://dx.doi.org/10.5772/intechopen.83654*

*Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation DOI: http://dx.doi.org/10.5772/intechopen.83654*

#### **Figure 2.**

*Spinal Cord Injury Therapy*

clinical symptoms of pain [2].

impaired pathways [16].

decreases neural firing [4].

coupled with functional recovery after SCI [2].

**2.2 Transcranial direct current stimulation (tDCS)**

• I-wave protocol involves the repetitive stimulation of the motor cortex at 1.5 ms rate, seeking to mimic the indirect waves (I-waves) of corticospinal

• Paired associative stimulation (PAS) relies on the Hebb's theory, which states that a synaptic connection is enhanced when two stimuli converge in time repeatedly. PAS protocol combines a peripheral nerve stimulus with a TMS pulse over the motor cortex, aiming to pair both stimuli in time at the cortex, which will promote corticospinal excitability. PAS can present different variants, in which the TMS pulse can be replaced by physiological activation of the motor cortex (e.g., imaginary movement), or the pairing site targets of TMS

and peripheral stimulus are the motoneurons at the spinal cord.

Regardless of its incipient stage and current limitations, rTMS has become a promising approach for SCI rehabilitation, not only to improve motor function but also to decrease spasticity and neuropathic pain. This technique enables targeting and promoting long-term changes in neural pathways, by exploiting the plastic properties that may facilitate function recovery. Improvements seem to be present when higher rTMS stimulus intensities are used [2]. On the other hand, the few studies that investigated the effects of rTMS on spasticity in iSCI patients reported some reduction in the clinical symptoms of spasticity [2]. Moreover, the few studies that tested the effect of rTMS on neuropathic pain reported some reductions in the

Notwithstanding, these results hold a great variability, are not reproducible in all patients, and are limited to certain clinical assessment scales or neurophysiological measurements. Several constraints can explain current limitations of the rTMS application in SCI patients. First, there is a shortage of studies providing evidences of sustained benefits of rTMS therapy beyond conventional treatments. Besides the different stimulation protocols and parameters applied, type of lesion and nonuniform assessment methodologies hamper the development of consistent evidences. Although evidences so far do not suggest any harm to the subjects, safety issues should be also considered when using rTMS in SCI patients, especially because of the high threshold needed to evoke motor responses in the

More research is needed to provide robust evidence that can support the use of rTMS as an alternative to standard therapies. In addition to bigger sample sizes used in each study, researchers should also test the same (or very similar) stimulation parameters and protocols to provide reproducible results. Finally, it is critical to better understand the pathophysiology of neural structures affected by rTMS to design optimal and customized protocols that might boost beneficial neural changes

Transcranial direct current stimulation (tDCS) is a technology that delivers continuous low current stimulation (1–2 mA) via paired anode and cathode electrodes over the scalp [4, 14, 17] (see **Figure 2**). This modality is usually combined with motor training to promote activity-dependent plasticity [14]. tDCS may change brain function by causing neurons resting potential to depolarize or hyperpolarize. Depolarization happens when positive stimulation (anodal tDCS) is delivered, which increases neural excitability and, therefore, neural firing. Cathodal tDCS (negative stimulation) causes hyperpolarization and, thus,

neurons and to increase their excitability [4].

**98**

*Transcranial direct current stimulation delivers continuous low current stimulation by applying a positive (anodal) or negative (cathodal) current via paired electrodes over the scalp.*

This technique is still in the early stage. To our knowledge, just seven studies have examined improvements in motor function after SCI related to the use of tDCS: four studies evaluated its effect on upper limb function [18–21] and three studies evaluated the tDCS effect on lower limb function and gait [22–24]. All these studies used anodal stimulation and showed improvements in upper and lower limb motor function.

The use of tDCS has led to improvements in pinch force, manual dexterity, and force modulation when combined with repetitive practice [18]. Other study reported that stimulation intensity affects functional outcomes when tDCS was delivered at rest: increased corticospinal excitability to affected muscles was obtained when using 2 mA stimulation, but not 1 mA, in nine chronic SCI patients [19]. Another study also reported gains in hand motor function after a single session of 2mA tDCS, though no improvements were described in clinical scales [20]. When combining tDCS with robot-assisted arm training, SCI patients improved arm and hand function post-treatment and at the 2-month follow-up [21].

The three studies that evaluated the tDCS effect on lower limb function and gait showed improved motor function [22–24]. However, one of these studies combined tDCS with robotic gait training and also showed no significant differences between these improvements and those verified in the group who received sham stimulation combined with robotic gait training [22].

tDCS is an attractive noninvasive modality option for the treatment after SCI: it is affordable and does not present substantial adverse events (when present, they included redness of the skin, sleepiness, headache, and neck pain [4]). However, further research is still needed to provide robust evidence that support the use of tDCS to improve motor function and to be used in the clinical setting as a long-term strategy after SCI.

#### **3. Transcutaneous spinal cord stimulation (tcSCS)**

In the recent years, spinal cord electrical stimulation (SCS) has arisen as a promising tool to modulate corticospinal excitability and modify the motor output in

SCI individuals. The most extended form of SCS is epidural SCS, which consists on delivering electrical currents through arrays of electrodes implanted in the epidural space of the spinal cord, in order to modify the excitatory output of the spinal cord. It has been widely studied as an application for chronic pain relief [14]. Promising results from a recent research showed its potential to improve neurological recovery and support the activities of daily living (including walking) after SCI [25].

Transcutaneous spinal cord stimulation (tcSCS) is a novel form of SCS that delivers superficial stimulation, usually over the skin that overlies the lower thoracic and/or lumbosacral vertebrae [26]. The principles underlying tcSCS rely on the physiology of the corticospinal pathways in the spinal cord that can produce excitability changes in the different neural populations of the spinal circuitry [27, 28]. Central pattern generators (CPGs) are pools of neurons able to elicit rhythmic and coordinated movements without the contribution of supraspinal centers. CPGs use proprioceptive information to provide real-time and coordinated control of motor output. The propriospinal system serves as an integratory interface between supraspinal and spinal centers, modulating motor activity. tcSCS is able to modulate the excitability properties of these systems by means of different stimulation protocols, in which the surface array placement along the spinal cord, direction of the current, intensity, frequency, and timing of stimulation result in different modulation outcomes. tcSCS was able to activate GPGs in healthy volunteers, eliciting coordinated and synchronized nonvoluntary movements of the lower limb [28]. These findings have been reproduced in SCI individuals, namely by reactivating damaged spinal circuitries that were previously considered as nonfunctional. When tcSCS was applied over several training sessions in SCI patients, there was improved voluntary modulation of movement of the lower limbs [29]. Moreover, combining tcSCS training with pharmacology therapy and exoskeletons increased motor control enhancement [26].

tcSCS overcomes the invasiveness and costs of epidural SCS with the trade-off of poor spatial stimulation resolution. Although the number of studies using this technique is considerably low, and the exact physiological mechanisms behind the improvements shown are still yet to be fully understood, tcSCS is already a promising tool to be considered in future SCI rehabilitation. Multi-approach therapies including tcSCS, pharmacological, active movement, and robotic-assisted training should be considered to exploit the combination of different physiological effects produced by each modality and maximize motor recovery [26].

#### **4. Peripheral stimulation and assistive devices**

Motor control and the execution of voluntary movements require the interaction between afferent feedback and supraspinal input to accurately plan and execute movements. This interplay induces activity-dependent plasticity at both the brain and spinal cord level [30, 31]. After SCI, afferent feedback is impaired and becomes essential to reorganize spinal circuits below the lesion area [30]. Therefore, noninvasive modalities that apply surface electrical stimulation at the peripheral level (either alone or combined with assisted training) to augment or modify neural function are very appealing and have been applied in SCI rehabilitation.

This section overviews two forms of surface stimulation that are user friendly and can be easily administered by a therapist during SCI rehabilitation: transcutaneous electrical nerve stimulation (TENS) and functional electrical stimulation (FES). The second part of this section reports the main results attained when using cycling driven by electrical stimulation and the combination of electrical stimulation with external robotic devices.

**101**

*Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation*

**4.1 Transcutaneous electrical nerve stimulation (TENS)**

(below motor threshold) surface electrical current [33].

TENS is the most common noninvasive modality used in physical therapy [32]. This type of stimulation delivers high-frequency (50–150 Hz) and low-intensity

Though TENS has been commonly used in pain control and to reduce muscle stiffness/tone, there are also some reports on decreased spasticity due to the use of this modality. For instance, TENS has recently reduced spasticity in SCI patients and the effects outlasted up to several hours after treatment [34]. This is because TENS activates sensory nerves that in turn may activate inhibitory interneurons that will inhibit the spastic muscle activity [34]. More specifically, these anti-spastic effects are due to the release of gamma-aminobutyric acid (GABA) that acts as inhibitory neurotransmitters, achieving similar anti-spastic effects to those of baclofen [32], which is a first-line treatment for spasticity, especially in adults who suffered a SCI [35]. Results of spasticity treatment using TENS seem to improve

Given its low cost, lack of adverse event effects, and ease to use, TENS seems to be a very good solution to treat spasticity after SCI. Moreover, since TENS alleviates pain and fatigue and can be used for periods of several hours, it seems to be appropriate for the beginning of the rehabilitation after SCI, when training is not

**4.2 Functional electrical stimulation (FES) and brain-machine interfaces** 

FES is another modality of electrical stimulation that has become very popular in the clinical setting. FES is similar to TENS in the sense that the two modalities use electrodes on the skin to provide electrical stimulation to a desired location of the body; but they differ in the settings and especially in the purpose of their use. Unlike TENS, FES delivers trains of electrical stimulation above motor threshold to stimulate a muscle or the efferent nerve supplying a muscle in order to attain a muscle contraction [14]. The higher the amplitude of this stimulation, the bigger is the number of recruited efferent fibers and, therefore,

FES has been used to restore bladder and bowel control, as well as sexual function, which are ranked among the most important functions to regain among SCI patients [37]. FES has also been widely used for the treatment of muscle weakness, gait training, and muscle reeducation [34]. In the case of SCI, it is well known that artificially induced contraction of weak or paralyzed muscles brings several therapeutic benefits, such as prevention of lower limb muscle atrophy, increased muscle strength, endurance, and cardiovascular fitness [38, 39]. In addition to these benefits, the coordinated stimulation of efferent nerves (usually to stimulate agonist-antagonist muscles of a joint) can be paired with a functional activity to produce a given biomechanical task and, thus, restore motor function [34].

On the other hand, there is evidence that peripheral stimulation, if synchronized with patients' voluntary effort, can further promote recovery [14]. In fact, improved modulation together with volitional control seems to be key factors to reinforce connectivity during rehabilitation of SCI patients, presumably through synaptic enhancement [14]. In this sense, brain-machine interfaces (BMIs) are currently the most sophisticated neuromodulation tools to restore voluntary limb movements after SCI. In the context of the noninvasive modalities described in this chapter, BMIs can be used to stimulate the peripheral nervous system by use of

decoded brain signals recorded with electroencephalography (EEG) [14].

*DOI: http://dx.doi.org/10.5772/intechopen.83654*

when combined with physical therapy [36].

the higher the muscle contraction.

very intensive.

**(BMIs)**

*Spinal Cord Injury Therapy*

SCI individuals. The most extended form of SCS is epidural SCS, which consists on delivering electrical currents through arrays of electrodes implanted in the epidural space of the spinal cord, in order to modify the excitatory output of the spinal cord. It has been widely studied as an application for chronic pain relief [14]. Promising results from a recent research showed its potential to improve neurological recovery

Transcutaneous spinal cord stimulation (tcSCS) is a novel form of SCS that delivers superficial stimulation, usually over the skin that overlies the lower thoracic and/or lumbosacral vertebrae [26]. The principles underlying tcSCS rely on the physiology of the corticospinal pathways in the spinal cord that can produce excitability changes in the different neural populations of the spinal circuitry [27, 28]. Central pattern generators (CPGs) are pools of neurons able to elicit rhythmic and coordinated movements without the contribution of supraspinal centers. CPGs use proprioceptive information to provide real-time and coordinated control of motor output. The propriospinal system serves as an integratory interface between supraspinal and spinal centers, modulating motor activity. tcSCS is able to modulate the excitability properties of these systems by means of different stimulation protocols, in which the surface array placement along the spinal cord, direction of the current, intensity, frequency, and timing of stimulation result in different modulation outcomes. tcSCS was able to activate GPGs in healthy volunteers, eliciting coordinated and synchronized nonvoluntary movements of the lower limb [28]. These findings have been reproduced in SCI individuals, namely by reactivating damaged spinal circuitries that were previously considered as nonfunctional. When tcSCS was applied over several training sessions in SCI patients, there was improved voluntary modulation of movement of the lower limbs [29]. Moreover, combining tcSCS training with pharmacology

and support the activities of daily living (including walking) after SCI [25].

therapy and exoskeletons increased motor control enhancement [26].

produced by each modality and maximize motor recovery [26].

**4. Peripheral stimulation and assistive devices**

tcSCS overcomes the invasiveness and costs of epidural SCS with the trade-off of poor spatial stimulation resolution. Although the number of studies using this technique is considerably low, and the exact physiological mechanisms behind the improvements shown are still yet to be fully understood, tcSCS is already a promising tool to be considered in future SCI rehabilitation. Multi-approach therapies including tcSCS, pharmacological, active movement, and robotic-assisted training should be considered to exploit the combination of different physiological effects

Motor control and the execution of voluntary movements require the interaction

This section overviews two forms of surface stimulation that are user friendly and can be easily administered by a therapist during SCI rehabilitation: transcutaneous electrical nerve stimulation (TENS) and functional electrical stimulation (FES). The second part of this section reports the main results attained when using cycling driven by electrical stimulation and the combination of electrical stimula-

between afferent feedback and supraspinal input to accurately plan and execute movements. This interplay induces activity-dependent plasticity at both the brain and spinal cord level [30, 31]. After SCI, afferent feedback is impaired and becomes essential to reorganize spinal circuits below the lesion area [30]. Therefore, noninvasive modalities that apply surface electrical stimulation at the peripheral level (either alone or combined with assisted training) to augment or modify neural function are very appealing and have been applied in SCI rehabilitation.

**100**

tion with external robotic devices.

#### **4.1 Transcutaneous electrical nerve stimulation (TENS)**

TENS is the most common noninvasive modality used in physical therapy [32]. This type of stimulation delivers high-frequency (50–150 Hz) and low-intensity (below motor threshold) surface electrical current [33].

Though TENS has been commonly used in pain control and to reduce muscle stiffness/tone, there are also some reports on decreased spasticity due to the use of this modality. For instance, TENS has recently reduced spasticity in SCI patients and the effects outlasted up to several hours after treatment [34]. This is because TENS activates sensory nerves that in turn may activate inhibitory interneurons that will inhibit the spastic muscle activity [34]. More specifically, these anti-spastic effects are due to the release of gamma-aminobutyric acid (GABA) that acts as inhibitory neurotransmitters, achieving similar anti-spastic effects to those of baclofen [32], which is a first-line treatment for spasticity, especially in adults who suffered a SCI [35]. Results of spasticity treatment using TENS seem to improve when combined with physical therapy [36].

Given its low cost, lack of adverse event effects, and ease to use, TENS seems to be a very good solution to treat spasticity after SCI. Moreover, since TENS alleviates pain and fatigue and can be used for periods of several hours, it seems to be appropriate for the beginning of the rehabilitation after SCI, when training is not very intensive.

#### **4.2 Functional electrical stimulation (FES) and brain-machine interfaces (BMIs)**

FES is another modality of electrical stimulation that has become very popular in the clinical setting. FES is similar to TENS in the sense that the two modalities use electrodes on the skin to provide electrical stimulation to a desired location of the body; but they differ in the settings and especially in the purpose of their use. Unlike TENS, FES delivers trains of electrical stimulation above motor threshold to stimulate a muscle or the efferent nerve supplying a muscle in order to attain a muscle contraction [14]. The higher the amplitude of this stimulation, the bigger is the number of recruited efferent fibers and, therefore, the higher the muscle contraction.

FES has been used to restore bladder and bowel control, as well as sexual function, which are ranked among the most important functions to regain among SCI patients [37]. FES has also been widely used for the treatment of muscle weakness, gait training, and muscle reeducation [34]. In the case of SCI, it is well known that artificially induced contraction of weak or paralyzed muscles brings several therapeutic benefits, such as prevention of lower limb muscle atrophy, increased muscle strength, endurance, and cardiovascular fitness [38, 39]. In addition to these benefits, the coordinated stimulation of efferent nerves (usually to stimulate agonist-antagonist muscles of a joint) can be paired with a functional activity to produce a given biomechanical task and, thus, restore motor function [34].

On the other hand, there is evidence that peripheral stimulation, if synchronized with patients' voluntary effort, can further promote recovery [14]. In fact, improved modulation together with volitional control seems to be key factors to reinforce connectivity during rehabilitation of SCI patients, presumably through synaptic enhancement [14]. In this sense, brain-machine interfaces (BMIs) are currently the most sophisticated neuromodulation tools to restore voluntary limb movements after SCI. In the context of the noninvasive modalities described in this chapter, BMIs can be used to stimulate the peripheral nervous system by use of decoded brain signals recorded with electroencephalography (EEG) [14].

Finally, FES has also been used to reduce spasticity in SCI patients, usually by stimulating the spastic muscle. This is hypothesized to modulate recurrent inhibition via Renshaw cells [34]. These inhibitory interneurons are excited by collaterals of the axons of motoneurons and make inhibitory synaptic connections with several populations of motoneurons, including those that excite them [40]. This reciprocal inhibition is important to prevent overshooting muscle contraction induced by FES.

Despite all the benefits here described, FES presents several challenges for tasks that are executed for long periods of time. Limited muscle force generation, rapid onset of muscle fatigue, and nonlinear, time-dependent mechanical responses, as well as the redundancy of the musculoskeletal system are the main challenges of this technology that traditionally hamper generalized use for rehabilitation and/or motor compensation of walking. However, multi-electrode techniques are showing promising results [41] and should be explored.

#### **4.3 FES driven cycling**

Physical activity of SCI people whose limbs are paralyzed is very important to maintain their physiological well-being. A promising approach is the application of FES during cycling movements. This technique, called FES cycling, is a noninvasive training protocol used in medical rehabilitation, mostly addressed to individual affected by SCI. This method can be applied continuously for tens of minutes, with direct benefits on muscle strength. Besides muscle strengthening, FES cycling is beneficial for cardiovascular and respiratory functions [42].

FES training for lower limb muscles can be performed on stationary cycle ergometers or mobile tricycles. As shown in **Figure 3**, FES is managed by a controller, which receives signals from a crank angle sensor and, depending on the actual crank position, transfers sequences of electrical impulses to surface electrodes to stimulate muscles and generate active muscle force. The power output produced by the application of FES depends on three main aspects. The first is the number of muscle groups stimulated. The second is the parameters of the stimulating current, that is, amplitude, pulse width, and frequency. The third is the timing of the stimulating signal sent to the individual muscles.

FES cycling is usually applied on several lower limb muscles simultaneously [43]. The main muscle groups considered are the hamstrings and quadriceps and, in

#### **Figure 3.**

*FES driven cycling: a controller sends electrical signals (stimulation current) to selected muscles. The actual muscle forces depend on the actual crank angle value transferred to the controller and on the parameters and timing of the stimulation signals sent to individual muscles.*

**103**

*Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation*

more efficient, natural, and adaptable stimulation protocols.

research works in this direction [54, 55].

**4.4 Exoskeletons and hybrid exoskeletons**

Cadence is another important variable in FES-cycling rehabilitation. In the case of ergometer-based training, cadence is on average set to 45–50 rpm, in most of the stimulating conditions. To adapt the treatment to patient residual motor ability, cadence can be changed in combination with various crank resistances during the rehabilitation process. Tricycles have been proposed as an alternative to stationary cycle ergometers [48]. A recent study reported that the series of FES trainings on a tricycle resulted in increased speed of cycling of paraplegics with denervated muscles [49], which is normally not observed in similar ergometer-based protocols. FES-driven tricycling is gaining relevance, as testified by several competitions organized during the last couple of years [50–53]. However, these competitions are only targeting people with SCI. We expect that wider range of participants, for example, stroke, will also be addressed in the near future, as supported by recent promising

Repetitive and intensive task-specific training drives beneficial neuroplasticity, thus enhancing functional recovery [56]. Therefore, exoskeletons for motor rehabilitation purposes have emerged in the last decade as a convenient technology that allow multiple, intensive, and more effective sessions of gait training, allowing SCI patients to ameliorate their performance in daily life [56]. Moreover, a study reported that spasticity and pain intensity of SCI patients decreased after one single

A paradigmatic development of a stationary rehabilitation robot for gait training is the Lokomat system, which combines body-weight supported treadmill-training (BWSTT) with the assistance of a robotic gait orthosis. These robotic systems are able to provide guidance forces to the lower limb segments to induce a consisting stepping pattern with adjustable guidance. It has been shown that although the mechanical coupling and added guidance may change the task constraints and in

session of walking assisted by a powered robotic exoskeleton [56].

some cases, the gluteus maximus. The quadriceps are stimulated either as a whole, that is, using only one pair of electrodes, or more selectively, in which three muscles composing them—that is, the vastus medialis, vastus lateralis, and rectus femoris—are stimulated individually. This more selective stimulation has demonstrated, in a recent pilot study, to improve up to 27% the power output in one patient with spastic muscles [44]. In this case, while the total stimulation current (the sum of the amplitude of currents applied in all of the channels) was higher, lower stimulation current amplitudes per muscle groups were sufficient to generate the required movement. The average current amplitude applied in FES cycling in SCI individuals is around 50–70 mA per muscles and it varies in a wide range. In some protocols, the current amplitude is increased until 120–140 mA to achieve power output around 10 W [45] and in extreme cases 20 W [46]. Others stimulated muscles with a frequency of 30 Hz, current amplitude of 70–90 mA, and pulse width of 500 μs, reaching a power output around 30 W [47]. The timing of stimulation is usually set according to recorded and processed muscle activities of able-bodied persons and/or on physiological, biomechanical parameters of the muscles and limbs of the participants. Nevertheless, these approaches are either not adaptive to the patientspecific musculoskeletal conditions, or very difficult to calibrate. For instance, when applying selective stimulation of the three quadriceps muscles separately [44], we found that the participant, even reaching higher power output, preferred to cycle for a shorter time, possibly due to a nonphysiological stimulation strategy. In our opinion, more studies are needed to explore these control combinations, in particular considering the case of selective stimulation. This will likely lead to new

*DOI: http://dx.doi.org/10.5772/intechopen.83654*

#### *Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation DOI: http://dx.doi.org/10.5772/intechopen.83654*

*Spinal Cord Injury Therapy*

**4.3 FES driven cycling**

promising results [41] and should be explored.

beneficial for cardiovascular and respiratory functions [42].

stimulating signal sent to the individual muscles.

*timing of the stimulation signals sent to individual muscles.*

Finally, FES has also been used to reduce spasticity in SCI patients, usually by stimulating the spastic muscle. This is hypothesized to modulate recurrent inhibition via Renshaw cells [34]. These inhibitory interneurons are excited by collaterals of the axons of motoneurons and make inhibitory synaptic connections with several populations of motoneurons, including those that excite them [40]. This reciprocal inhibition is important to prevent overshooting muscle contraction induced by FES. Despite all the benefits here described, FES presents several challenges for tasks that are executed for long periods of time. Limited muscle force generation, rapid onset of muscle fatigue, and nonlinear, time-dependent mechanical responses, as well as the redundancy of the musculoskeletal system are the main challenges of this technology that traditionally hamper generalized use for rehabilitation and/or motor compensation of walking. However, multi-electrode techniques are showing

Physical activity of SCI people whose limbs are paralyzed is very important to maintain their physiological well-being. A promising approach is the application of FES during cycling movements. This technique, called FES cycling, is a noninvasive training protocol used in medical rehabilitation, mostly addressed to individual affected by SCI. This method can be applied continuously for tens of minutes, with direct benefits on muscle strength. Besides muscle strengthening, FES cycling is

FES training for lower limb muscles can be performed on stationary cycle ergometers or mobile tricycles. As shown in **Figure 3**, FES is managed by a controller, which receives signals from a crank angle sensor and, depending on the actual crank position, transfers sequences of electrical impulses to surface electrodes to stimulate muscles and generate active muscle force. The power output produced by the application of FES depends on three main aspects. The first is the number of muscle groups stimulated. The second is the parameters of the stimulating current, that is, amplitude, pulse width, and frequency. The third is the timing of the

FES cycling is usually applied on several lower limb muscles simultaneously [43]. The main muscle groups considered are the hamstrings and quadriceps and, in

*FES driven cycling: a controller sends electrical signals (stimulation current) to selected muscles. The actual muscle forces depend on the actual crank angle value transferred to the controller and on the parameters and* 

**102**

**Figure 3.**

some cases, the gluteus maximus. The quadriceps are stimulated either as a whole, that is, using only one pair of electrodes, or more selectively, in which three muscles composing them—that is, the vastus medialis, vastus lateralis, and rectus femoris—are stimulated individually. This more selective stimulation has demonstrated, in a recent pilot study, to improve up to 27% the power output in one patient with spastic muscles [44]. In this case, while the total stimulation current (the sum of the amplitude of currents applied in all of the channels) was higher, lower stimulation current amplitudes per muscle groups were sufficient to generate the required movement. The average current amplitude applied in FES cycling in SCI individuals is around 50–70 mA per muscles and it varies in a wide range. In some protocols, the current amplitude is increased until 120–140 mA to achieve power output around 10 W [45] and in extreme cases 20 W [46]. Others stimulated muscles with a frequency of 30 Hz, current amplitude of 70–90 mA, and pulse width of 500 μs, reaching a power output around 30 W [47]. The timing of stimulation is usually set according to recorded and processed muscle activities of able-bodied persons and/or on physiological, biomechanical parameters of the muscles and limbs of the participants. Nevertheless, these approaches are either not adaptive to the patientspecific musculoskeletal conditions, or very difficult to calibrate. For instance, when applying selective stimulation of the three quadriceps muscles separately [44], we found that the participant, even reaching higher power output, preferred to cycle for a shorter time, possibly due to a nonphysiological stimulation strategy. In our opinion, more studies are needed to explore these control combinations, in particular considering the case of selective stimulation. This will likely lead to new more efficient, natural, and adaptable stimulation protocols.

Cadence is another important variable in FES-cycling rehabilitation. In the case of ergometer-based training, cadence is on average set to 45–50 rpm, in most of the stimulating conditions. To adapt the treatment to patient residual motor ability, cadence can be changed in combination with various crank resistances during the rehabilitation process. Tricycles have been proposed as an alternative to stationary cycle ergometers [48]. A recent study reported that the series of FES trainings on a tricycle resulted in increased speed of cycling of paraplegics with denervated muscles [49], which is normally not observed in similar ergometer-based protocols. FES-driven tricycling is gaining relevance, as testified by several competitions organized during the last couple of years [50–53]. However, these competitions are only targeting people with SCI. We expect that wider range of participants, for example, stroke, will also be addressed in the near future, as supported by recent promising research works in this direction [54, 55].

#### **4.4 Exoskeletons and hybrid exoskeletons**

Repetitive and intensive task-specific training drives beneficial neuroplasticity, thus enhancing functional recovery [56]. Therefore, exoskeletons for motor rehabilitation purposes have emerged in the last decade as a convenient technology that allow multiple, intensive, and more effective sessions of gait training, allowing SCI patients to ameliorate their performance in daily life [56]. Moreover, a study reported that spasticity and pain intensity of SCI patients decreased after one single session of walking assisted by a powered robotic exoskeleton [56].

A paradigmatic development of a stationary rehabilitation robot for gait training is the Lokomat system, which combines body-weight supported treadmill-training (BWSTT) with the assistance of a robotic gait orthosis. These robotic systems are able to provide guidance forces to the lower limb segments to induce a consisting stepping pattern with adjustable guidance. It has been shown that although the mechanical coupling and added guidance may change the task constraints and in

turn alter voluntary leg movements, the basic neuromuscular pattern is preserved when intact humans walk assisted by this robot [57]. Robot-assisted gait training with the Lokomat after SCI has been shown in some studies to improve outcomes related to mobility when compared to conventional overground training [58, 59]. For example, it was shown improved gait distance, strength, and functional level of mobility and independence of acute SCI patients receiving robotic-assisted gait training than the group of patients receiving conventional overground training [60]. Also, it has been demonstrated that robot-assisted gait training combined with conventional physiotherapy could yield more improvement in ambulatory function of SCI patients than conventional therapy alone. However, the impact of such complementary tools to provide neuromuscular education is still not well established for a convincing penetration of these systems in the clinical rehabilitation environments. Some limitations of such stationary robotic tools are that robotic-assisted training can be limited in the range of gait speed at which the exoskeleton robot can provide a comfortable gait pattern. Also, the stationary machine imposes restrictions to the user movements to the sagittal plane, significantly preventing motion in the frontal and transversal plane that are required for overground walking.

Wearable robots (WR) for overground untethered assisted walking are emerging devices that have the potential to overcome some of the above-mentioned constraints and opening a range of clinical application scenarios. Through wearable mechanical actuation and sensing, WRs are proliferating for their use as assistive and rehabilitation technologies due to their ability to replicate the complex motions involved in human movement. As a result, the past few decades have seen an increasing amount of research focused on developing robotic systems intended to interact with the neurologically impaired human body. This interaction (of the human body) with WRs has been established in foundational literature [61] as dual, bidirectional physical (pHRi), and cognitive (cHRi) interactions. While these systems have been proven to be useful for specific applications, such as in-clinic rehabilitation, current research in the area of pHRi for WRs is focusing more on developing lightweight and flexible force interactions with hardware solutions that might be more suitable to a broader range of applications (by adding compliance to rigid exoskeletons [62, 63] or developing "soft exosuits" [64]). However, these soft exoskeletons are in early stage and the majority of clinical evidence of their efficacy for treatment of SCI is in studies with motorized powered exoskeletons. A systematic review of the literature on powered WRs for overground gait rehabilitation pointed out that, although current technology is still under development, and hence its ultimate impact remains still unclear, a number of revised studies report positive changes in outcome variables and suggest that training time and improvements in gait speed using powered WRs are correlated in SCI population [65].

On the cHRi side, efforts are focused on developing means for interpretation of mechanical and neural signals to establish adequate control methods that integrate WRs as parts of human functioning. In this regard, a scheme for "symbiotic interaction" between humans and WRs has been recently developed in the FET Project BioMot (FP7-ICT-2013-10-611695), yielding new technologies to interface human neuromechanics with robot-control algorithms to guide assistance; the point of increasing their proficiency is to make them more capable of sophisticated interdependent joint activity with the human wearer. Under this approach, a tacit adaptability is provided to modulate the compliance in the robot torque controller, to automatically modulate in turn the difficulty of the task [66].

There is currently no agreement on the optimal robot-mediated treatment programs to induce plasticity and promote recovery of motor function following SCI, and the understanding of recovery mechanisms is still an open matter [67]. Whatever the robot hardware and patient's functional status, a WR-mediated

**105**

*Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation*

neurorehabilitation model could pave the way for effective restoration of mobility after major neurological conditions. In the last few years, the development of computational neurorehabilitation models is becoming a relevant topic in the domain of neural repair, as these computational models can be expected to provide the basis for future clinical robot software that suggests timing, dosage, and content of therapy. For example, an analytical modeling approach has been applied to robot-mediated rehabilitation data of a group of SCI subjects, providing insights with regard to patient grouping and gait recovery prognosis and also providing predictive quantitative measures to consider before starting the treatment [68]. This, together with the fact that in the past years we are witnessing an unprecedented number of wearable interactive robotics products that will populate even more the clinic environments, a reasonable long-term vision is to gather multicenter clinical data to equip rehabilitation WRs with computational neurorehabilitation modeling tools that will in turn provide enriched data to establish scientific bases of

On the other hand, the combination of FES with external orthotic devices that provide joint support and mechanical constraint to undesired movements was early proposed [69], but the challenges associated with the rapid onset of muscle fatigue and movement control still remained. In an attempt to further diminish the energy demand from the muscle while providing better joint control, FES systems were combined with lower limb exoskeletons, also called hybrid exoskeletons [70]. The combination of the lower limb robotic exoskeleton and the FES system can be shaped in different ways, depending on the configuration of the FES system and/or the exoskeleton. Regarding the former, the FES can be implanted [71] or superficial [72] and can be found either under open [71, 73] or closed-loop [72, 74] control of stimulation. With regards to the exoskeleton joints, it can provide means of dissipating energy, via the use of clutches or brakes [75, 76], or can feature active joints, which can also provide

The hybrid configuration presents some advantages with respect to the FES or exoskeleton applications alone. First, the exoskeleton structure provides passive control to the joints, constraining undesirable movements. The actuators can provide support to the joints, diminishing or eliminating the need for stimulation of certain muscles (e.g., quadriceps muscles during the stance phases of walking). In the case of active actuators, the movement produced by the FES is supported by the actuator, improving the control of the joint trajectory while delaying muscle fatigue [77]. On the other hand, the sensors of the exoskeleton provide information for closing the control loop of the FES system, which may further help on optimizing the performance of the muscle in terms of either force production or muscle

Despite hybrid exoskeletons show several advantages, the field is not mature. There is a markedly low activity in this field, and most of the groups working on this technology have discontinued their research on this topic. The rationale for this may come from the bottlenecks of each technology. First, hybrid exoskeletons share drawbacks with lower limb robotic exoskeletons, in which the combination with a FES system add complexity on the control and wearing aspects. Besides, although alleviated by the exoskeleton, the nonlinear muscle response of the stimulated muscles and the muscle fatigue is not adequately solved yet, and eventually all hybrid exoskeletons still have to be designed to function as conventional robotic

Lastly, there is a need of conducting clinical studies that can demonstrate the benefits of using hybrid exoskeleton with respect to exoskeleton alone that actually

justify the extra complexity, cost, and cumbersomeness of the FES system.

*DOI: http://dx.doi.org/10.5772/intechopen.83654*

exoskeleton-guided recovery.

energy to the joints.

fatigue [72].

exoskeletons once muscle fatigue appears.

#### *Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation DOI: http://dx.doi.org/10.5772/intechopen.83654*

*Spinal Cord Injury Therapy*

turn alter voluntary leg movements, the basic neuromuscular pattern is preserved when intact humans walk assisted by this robot [57]. Robot-assisted gait training with the Lokomat after SCI has been shown in some studies to improve outcomes related to mobility when compared to conventional overground training [58, 59]. For example, it was shown improved gait distance, strength, and functional level of mobility and independence of acute SCI patients receiving robotic-assisted gait training than the group of patients receiving conventional overground training [60]. Also, it has been demonstrated that robot-assisted gait training combined with conventional physiotherapy could yield more improvement in ambulatory function of SCI patients than conventional therapy alone. However, the impact of such complementary tools to provide neuromuscular education is still not well established for a convincing penetration of these systems in the clinical rehabilitation environments. Some limitations of such stationary robotic tools are that robotic-assisted training can be limited in the range of gait speed at which the exoskeleton robot can provide a comfortable gait pattern. Also, the stationary machine imposes restrictions to the user movements to the sagittal plane, significantly preventing motion in the frontal

Wearable robots (WR) for overground untethered assisted walking are emerg-

ing devices that have the potential to overcome some of the above-mentioned constraints and opening a range of clinical application scenarios. Through wearable mechanical actuation and sensing, WRs are proliferating for their use as assistive and rehabilitation technologies due to their ability to replicate the complex motions involved in human movement. As a result, the past few decades have seen an increasing amount of research focused on developing robotic systems intended to interact with the neurologically impaired human body. This interaction (of the human body) with WRs has been established in foundational literature [61] as dual, bidirectional physical (pHRi), and cognitive (cHRi) interactions. While these systems have been proven to be useful for specific applications, such as in-clinic rehabilitation, current research in the area of pHRi for WRs is focusing more on developing lightweight and flexible force interactions with hardware solutions that might be more suitable to a broader range of applications (by adding compliance to rigid exoskeletons [62, 63] or developing "soft exosuits" [64]). However, these soft exoskeletons are in early stage and the majority of clinical evidence of their efficacy for treatment of SCI is in studies with motorized powered exoskeletons. A systematic review of the literature on powered WRs for overground gait rehabilitation pointed out that, although current technology is still under development, and hence its ultimate impact remains still unclear, a number of revised studies report positive changes in outcome variables and suggest that training time and improvements in

and transversal plane that are required for overground walking.

gait speed using powered WRs are correlated in SCI population [65].

to automatically modulate in turn the difficulty of the task [66].

On the cHRi side, efforts are focused on developing means for interpretation of

mechanical and neural signals to establish adequate control methods that integrate WRs as parts of human functioning. In this regard, a scheme for "symbiotic interaction" between humans and WRs has been recently developed in the FET Project BioMot (FP7-ICT-2013-10-611695), yielding new technologies to interface human neuromechanics with robot-control algorithms to guide assistance; the point of increasing their proficiency is to make them more capable of sophisticated interdependent joint activity with the human wearer. Under this approach, a tacit adaptability is provided to modulate the compliance in the robot torque controller,

There is currently no agreement on the optimal robot-mediated treatment programs to induce plasticity and promote recovery of motor function following SCI, and the understanding of recovery mechanisms is still an open matter [67]. Whatever the robot hardware and patient's functional status, a WR-mediated

**104**

neurorehabilitation model could pave the way for effective restoration of mobility after major neurological conditions. In the last few years, the development of computational neurorehabilitation models is becoming a relevant topic in the domain of neural repair, as these computational models can be expected to provide the basis for future clinical robot software that suggests timing, dosage, and content of therapy. For example, an analytical modeling approach has been applied to robot-mediated rehabilitation data of a group of SCI subjects, providing insights with regard to patient grouping and gait recovery prognosis and also providing predictive quantitative measures to consider before starting the treatment [68]. This, together with the fact that in the past years we are witnessing an unprecedented number of wearable interactive robotics products that will populate even more the clinic environments, a reasonable long-term vision is to gather multicenter clinical data to equip rehabilitation WRs with computational neurorehabilitation modeling tools that will in turn provide enriched data to establish scientific bases of exoskeleton-guided recovery.

On the other hand, the combination of FES with external orthotic devices that provide joint support and mechanical constraint to undesired movements was early proposed [69], but the challenges associated with the rapid onset of muscle fatigue and movement control still remained. In an attempt to further diminish the energy demand from the muscle while providing better joint control, FES systems were combined with lower limb exoskeletons, also called hybrid exoskeletons [70]. The combination of the lower limb robotic exoskeleton and the FES system can be shaped in different ways, depending on the configuration of the FES system and/or the exoskeleton. Regarding the former, the FES can be implanted [71] or superficial [72] and can be found either under open [71, 73] or closed-loop [72, 74] control of stimulation. With regards to the exoskeleton joints, it can provide means of dissipating energy, via the use of clutches or brakes [75, 76], or can feature active joints, which can also provide energy to the joints.

The hybrid configuration presents some advantages with respect to the FES or exoskeleton applications alone. First, the exoskeleton structure provides passive control to the joints, constraining undesirable movements. The actuators can provide support to the joints, diminishing or eliminating the need for stimulation of certain muscles (e.g., quadriceps muscles during the stance phases of walking). In the case of active actuators, the movement produced by the FES is supported by the actuator, improving the control of the joint trajectory while delaying muscle fatigue [77]. On the other hand, the sensors of the exoskeleton provide information for closing the control loop of the FES system, which may further help on optimizing the performance of the muscle in terms of either force production or muscle fatigue [72].

Despite hybrid exoskeletons show several advantages, the field is not mature. There is a markedly low activity in this field, and most of the groups working on this technology have discontinued their research on this topic. The rationale for this may come from the bottlenecks of each technology. First, hybrid exoskeletons share drawbacks with lower limb robotic exoskeletons, in which the combination with a FES system add complexity on the control and wearing aspects. Besides, although alleviated by the exoskeleton, the nonlinear muscle response of the stimulated muscles and the muscle fatigue is not adequately solved yet, and eventually all hybrid exoskeletons still have to be designed to function as conventional robotic exoskeletons once muscle fatigue appears.

Lastly, there is a need of conducting clinical studies that can demonstrate the benefits of using hybrid exoskeleton with respect to exoskeleton alone that actually justify the extra complexity, cost, and cumbersomeness of the FES system.

#### **5. Conclusions and future directions**

This chapter presents an overview of the main effects on motor and functional recovery, as well as spasticity and pain, when using a wide range of noninvasive modalities in the rehabilitation of SCI patients, either in the research or the clinical setting. According to the level of stimulation, these modalities were divided into three different sections: brain, spinal cord, and peripheral stimulation. Regarding the last one, stimulation of the peripheral nervous system can also be combined with external devices that assist and allow repetitive motor training (e.g., hybrid exoskeletons and FES driven cycling).

Noninvasive brain stimulation (NIBS) techniques such as rTMS and tDCS have the potential to improve motor function recovery and spasticity after SCI. Moreover, NIBS techniques are safe and relatively easy to administer, presenting infrequent mild effects. Very few studies have investigated motor function after delivery of rTMS on SCI patients. Improvements seem to be present when higher rTMS frequencies are used. On the other hand, the few studies that investigated the effects of rTMS on spasticity in iSCI reported some reduction in the clinical symptoms of spasticity [2]. There are less studies of the application of tDCS in motor function or spasticity than those of rTMS [4], though they all showed improvements in upper or lower limb motor function. Thus, more research is needed to address the full potential and incorporate NIBS techniques into SCI rehabilitation [4].

At the spinal level stimulation, tcSCS has irrupted in the last years as a neurorehabilitation tool in SCI. It overcomes the limitation of invasiveness and costs of epidural stimulation at the expense of poor spatial stimulation resolution. The few evidences suggest that tsSCS alone improves voluntary modulation of lower limb movement [29] and increases motor control enhancement when combined with pharmacology therapy and exoskeletons [26].

Noninvasive modalities that deliver different types of surface stimulation at the peripheral level (either alone or combined with cycling or robotic-assisted training, for example) are very appealing and have been applied in SCI rehabilitation. Surface electrical stimulation can modulate afferent and efferent pathways in order to induce corticospinal plasticity. For instance, TENS and FES have reduced spasticity in SCI patients and the effects outlasted up to several hours after treatment, though the two techniques target different nerve groups in order to reduce spasticity: TENS activates afferents that in turn activate inhibitory interneurons that will inhibit the spastic muscle activity; FES induces muscle contraction and is oriented to the spastic muscle [34]. The development of fatigue and discomfort produced by the intensity of stimulation of FES is a drawback for long sessions. Thus, TENS may be appropriate for the beginning of the rehabilitation, while FES may have better effects on those SCI patients presenting spasmodic behavior [34]. On the other hand, BMIs may enhance brain and spinal cord neurorecovery through activity dependent plasticity. Future advances in wireless devices may potentiate the widespread use of BMIs in the clinical setting.

FES cycling is another modality that presents direct benefits on muscle strength, as well as cardiovascular and respiratory functions of SCI patients. However, more research on this technique is needed in order to design more efficient, natural, and adaptable stimulation protocols, which will likely improve motor function outcomes during SCI rehabilitation.

Robotic devices, such as exoskeletons, are other solutions that have been used for rehabilitation purposed after SCI. These devices can provide intensive, long lasting repetitive task specific training to SCI patients, which is the principle behind motor rehabilitation and beneficial neuroplasticity [78]. These devices have allowed SCI patients to ameliorate their performance in daily life [56]. The hybrid configuration

**107**

*Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation*

(exoskeleton combined with FES) presents some advantages with respect to the FES or exoskeleton applications alone: actuators can provide support to the joints, diminishing or eliminating the need for stimulation of certain muscles; the sensors of the exoskeleton provide information for closing the control loop of the FES system, which may further help on optimizing the performance of the muscle in terms of either force production or muscle fatigue. However, the field is not mature and there is a need of conducting clinical studies that can demonstrate the benefits of using hybrid exoskeleton with respect to exoskeleton alone that actually justify

Part of the current SCI rehabilitation research uses the modalities described in

Some of these modalities are already being widely introduced into the clinical rehabilitation of SCI, such as TENS and FES. However, the actual uptake of technology in the clinical setting, especially for SCI rehabilitation, has been very low [5]. There are still some barriers to the clinical implementation of these techniques. Three of those barriers are the feasibility, appropriateness, and the cost. While the research here described is practical for SCI rehabilitation, some of these techniques are less practicable: they require specialized equipment and knowledge, which make them less feasible [5]. Despite the scientific evidence in favor of these technologies, the expertise required to operate and repair emerging technology is usually not found in the clinical setting, which makes it less appropriate. A third barrier that deserves attention is the economic cost, given the fact that most of the clinical centers cannot afford the maintenance of these technologies. To overcome these barriers, it is essential to develop a proactive dialog between researchers and clinicians in order to properly examine each of the emerging modalities that can

This work was funded by the European Union's Horizon 2020 research and innovation programme (Project EXTEND—Bidirectional Hyper-Connected Neural System) under grant agreement No 779982 and by the EFOP-3.6.1-16-2016-00004

The authors declare that this work was conducted in the absence of any commercial or financial relationships that could be considered as a potential conflict of

the extra complexity, cost, and cumbersomeness of the FES system.

maximize the outcomes for each individual that suffered a SCI.

**Acknowledgements**

**Conflict of interest**

grant.

interest.

this chapter and has presented promising results including neurorecovery.

*DOI: http://dx.doi.org/10.5772/intechopen.83654*

#### *Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation DOI: http://dx.doi.org/10.5772/intechopen.83654*

*Spinal Cord Injury Therapy*

**5. Conclusions and future directions**

exoskeletons and FES driven cycling).

pharmacology therapy and exoskeletons [26].

widespread use of BMIs in the clinical setting.

comes during SCI rehabilitation.

This chapter presents an overview of the main effects on motor and functional recovery, as well as spasticity and pain, when using a wide range of noninvasive modalities in the rehabilitation of SCI patients, either in the research or the clinical setting. According to the level of stimulation, these modalities were divided into three different sections: brain, spinal cord, and peripheral stimulation. Regarding the last one, stimulation of the peripheral nervous system can also be combined with external devices that assist and allow repetitive motor training (e.g., hybrid

Noninvasive brain stimulation (NIBS) techniques such as rTMS and tDCS have the potential to improve motor function recovery and spasticity after SCI. Moreover, NIBS techniques are safe and relatively easy to administer, presenting infrequent mild effects. Very few studies have investigated motor function after delivery of rTMS on SCI patients. Improvements seem to be present when higher rTMS frequencies are used. On the other hand, the few studies that investigated the effects of rTMS on spasticity in iSCI reported some reduction in the clinical symptoms of spasticity [2]. There are less studies of the application of tDCS in motor function or spasticity than those of rTMS [4], though they all showed improvements in upper or lower limb motor function. Thus, more research is needed to address the full

At the spinal level stimulation, tcSCS has irrupted in the last years as a neurorehabilitation tool in SCI. It overcomes the limitation of invasiveness and costs of epidural stimulation at the expense of poor spatial stimulation resolution. The few evidences suggest that tsSCS alone improves voluntary modulation of lower limb movement [29] and increases motor control enhancement when combined with

Noninvasive modalities that deliver different types of surface stimulation at the peripheral level (either alone or combined with cycling or robotic-assisted training, for example) are very appealing and have been applied in SCI rehabilitation. Surface electrical stimulation can modulate afferent and efferent pathways in order to induce corticospinal plasticity. For instance, TENS and FES have reduced spasticity in SCI patients and the effects outlasted up to several hours after treatment, though the two techniques target different nerve groups in order to reduce spasticity: TENS activates afferents that in turn activate inhibitory interneurons that will inhibit the spastic muscle activity; FES induces muscle contraction and is oriented to the spastic muscle [34]. The development of fatigue and discomfort produced by the intensity of stimulation of FES is a drawback for long sessions. Thus, TENS may be appropriate for the beginning of the rehabilitation, while FES may have better effects on those SCI patients presenting spasmodic behavior [34]. On the other hand, BMIs may enhance brain and spinal cord neurorecovery through activity dependent plasticity. Future advances in wireless devices may potentiate the

FES cycling is another modality that presents direct benefits on muscle strength, as well as cardiovascular and respiratory functions of SCI patients. However, more research on this technique is needed in order to design more efficient, natural, and adaptable stimulation protocols, which will likely improve motor function out-

Robotic devices, such as exoskeletons, are other solutions that have been used for rehabilitation purposed after SCI. These devices can provide intensive, long lasting repetitive task specific training to SCI patients, which is the principle behind motor rehabilitation and beneficial neuroplasticity [78]. These devices have allowed SCI patients to ameliorate their performance in daily life [56]. The hybrid configuration

potential and incorporate NIBS techniques into SCI rehabilitation [4].

**106**

(exoskeleton combined with FES) presents some advantages with respect to the FES or exoskeleton applications alone: actuators can provide support to the joints, diminishing or eliminating the need for stimulation of certain muscles; the sensors of the exoskeleton provide information for closing the control loop of the FES system, which may further help on optimizing the performance of the muscle in terms of either force production or muscle fatigue. However, the field is not mature and there is a need of conducting clinical studies that can demonstrate the benefits of using hybrid exoskeleton with respect to exoskeleton alone that actually justify the extra complexity, cost, and cumbersomeness of the FES system.

Part of the current SCI rehabilitation research uses the modalities described in this chapter and has presented promising results including neurorecovery.

Some of these modalities are already being widely introduced into the clinical rehabilitation of SCI, such as TENS and FES. However, the actual uptake of technology in the clinical setting, especially for SCI rehabilitation, has been very low [5]. There are still some barriers to the clinical implementation of these techniques. Three of those barriers are the feasibility, appropriateness, and the cost. While the research here described is practical for SCI rehabilitation, some of these techniques are less practicable: they require specialized equipment and knowledge, which make them less feasible [5]. Despite the scientific evidence in favor of these technologies, the expertise required to operate and repair emerging technology is usually not found in the clinical setting, which makes it less appropriate. A third barrier that deserves attention is the economic cost, given the fact that most of the clinical centers cannot afford the maintenance of these technologies. To overcome these barriers, it is essential to develop a proactive dialog between researchers and clinicians in order to properly examine each of the emerging modalities that can maximize the outcomes for each individual that suffered a SCI.

#### **Acknowledgements**

This work was funded by the European Union's Horizon 2020 research and innovation programme (Project EXTEND—Bidirectional Hyper-Connected Neural System) under grant agreement No 779982 and by the EFOP-3.6.1-16-2016-00004 grant.

#### **Conflict of interest**

The authors declare that this work was conducted in the absence of any commercial or financial relationships that could be considered as a potential conflict of interest.

*Spinal Cord Injury Therapy*

#### **Author details**

Filipe O. Barroso1 \*, Alejandro Pascual-Valdunciel1 , Diego Torricelli1 , Juan C. Moreno1 , Antonio Del Ama-Espinosa2 , Jozsef Laczko3,4 and José L. Pons1

1 Neural Rehabilitation Group, Cajal Institute, Spanish National Research Council (CSIC), Madrid, Spain

2 Biomechanics and Assistive Technology Unit, National Hospital for Paraplegics, Toledo, Spain

3 Department of Information Technology and Biorobotics, Faculty of Science, University of Pecs, Hungary

4 Hungarian Academy of Sciences, Wigner Research Centre for Physics, Hungary

\*Address all correspondence to: filipe.barroso@cajal.csic.es

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**109**

*Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation*

nervioso. Madrid: Imprenta de Hijos de

[8] Hebb DO. The Organization of Behavior: A Neuropsychological Theory.

[9] Tahayori B, Koceja DM. Activitydependent plasticity of spinal circuits in the developing and mature spinal cord. Neural Plasticity. 2012;**2012**. DOI:

[10] Onifer SM, Smith GM, Fouad K. Plasticity after spinal cord injury: Relevance to recovery and approaches to facilitate it. Neurotherapeutics. 2011;**8**(2):283-293. DOI: 10.1007/

[11] Mawase F, Uehara S, Bastian AJ, Celnik P. Motor learning enhances use-dependent plasticity. The Journal of Neuroscience. 2017;**37**(10):2673-2685. DOI: 10.1523/JNEUROSCI.3303-16.2017

[12] Barroso FO, Torricelli D, Moreno JC. Emerging techniques for assessment of sensorimotor impairments after spinal cord injury. In: Fuller H, Gates M, editors. Recovery of Motor Function Following Spinal Cord Injury. London: IntechOpen; 2016. pp. 305-322. DOI:

[13] Squair JW, Bjerkefors A, Inglis JT, Lam T, Carpenter MG. Cortical and vestibular stimulation reveal preserved

individuals with motor-complete spinal cord injury. Journal of Rehabilitation Medicine. 2016;**48**(7):589-596. DOI:

[14] James ND, McMahon SB, Field-Fote EC, Bradbury EJ. Neuromodulation in the restoration of function after spinal cord injury. Lancet Neurology. 2018;**17**(10):905-917. DOI: 10.1016/

descending motor pathways in

10.2340/16501977-2101

S1474-4422(18)30287-4

Nicolás Moya; 1913

New York: Wiley; 1949

10.1155/2012/964843

s13311-011-0034-4

10.5772/64182

*DOI: http://dx.doi.org/10.5772/intechopen.83654*

[1] Barroso FO, Torricelli D, Bravo-Esteban E, Taylor J, Gómez-Soriano J, Santos C, et al. Muscle synergies in cycling after incomplete spinal cord injury: Correlation with clinical measures of motor function and spasticity. Frontiers in Human Neuroscience. 2016;**9**(706). DOI: 10.3389/fnhum.2015.00706

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10.1016/j.apmr.2014.07.418

sc.2015.199

[3] van Middendorp JJ, Allison HC, Ahuja S, Bracher D, Dyson C, Fairbank J, et al. Top ten research priorities for spinal cord injury: The methodology and results of a British priority setting partnership. Spinal Cord. 2016;**54**(5):341-346. DOI: 10.1038/

[4] Gunduz A, Rothwell J, Vidal J, Kumru H. Non-invasive brain stimulation to promote motor and functional recovery following spinal cord injury. Neural Regeneration Research. 2017;**12**(12):1933-1938. DOI:

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*Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation DOI: http://dx.doi.org/10.5772/intechopen.83654*

#### **References**

*Spinal Cord Injury Therapy*

**108**

**Author details**

Filipe O. Barroso1

(CSIC), Madrid, Spain

University of Pecs, Hungary

Juan C. Moreno1

Toledo, Spain

provided the original work is properly cited.

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

1 Neural Rehabilitation Group, Cajal Institute, Spanish National Research Council

2 Biomechanics and Assistive Technology Unit, National Hospital for Paraplegics,

3 Department of Information Technology and Biorobotics, Faculty of Science,

4 Hungarian Academy of Sciences, Wigner Research Centre for Physics, Hungary

\*, Alejandro Pascual-Valdunciel1

, Antonio Del Ama-Espinosa2

\*Address all correspondence to: filipe.barroso@cajal.csic.es

, Diego Torricelli1

, Jozsef Laczko3,4 and José L. Pons1

,

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[2] Tazoe T, Perez MA. Effects of repetitive transcranial magnetic stimulation on recovery of function after spinal cord injury. Archives of Physical Medicine and Rehabilitation. 2015;**96**(4 Suppl):S145-S155. DOI: 10.1016/j.apmr.2014.07.418

[3] van Middendorp JJ, Allison HC, Ahuja S, Bracher D, Dyson C, Fairbank J, et al. Top ten research priorities for spinal cord injury: The methodology and results of a British priority setting partnership. Spinal Cord. 2016;**54**(5):341-346. DOI: 10.1038/ sc.2015.199

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[11] Mawase F, Uehara S, Bastian AJ, Celnik P. Motor learning enhances use-dependent plasticity. The Journal of Neuroscience. 2017;**37**(10):2673-2685. DOI: 10.1523/JNEUROSCI.3303-16.2017

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[13] Squair JW, Bjerkefors A, Inglis JT, Lam T, Carpenter MG. Cortical and vestibular stimulation reveal preserved descending motor pathways in individuals with motor-complete spinal cord injury. Journal of Rehabilitation Medicine. 2016;**48**(7):589-596. DOI: 10.2340/16501977-2101

[14] James ND, McMahon SB, Field-Fote EC, Bradbury EJ. Neuromodulation in the restoration of function after spinal cord injury. Lancet Neurology. 2018;**17**(10):905-917. DOI: 10.1016/ S1474-4422(18)30287-4

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[19] Murray LM, Edwards DJ, Ruffini G, Labar D, Stampas A, Pascual-Leone A, et al. Intensity dependent effects of transcranial direct current stimulation on corticospinal excitability in chronic spinal cord injury. Archives of Physical Medicine and Rehabilitation. 2015;**96** (4 Suppl):S114-S121. DOI: 10.1016/j. apmr.2014.11.004

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[15] Rossini PM, Burke D, Chen R, Cohen LG, Daskalakis Z, Di Iorio R, et al. Non-invasive electrical and magnetic stimulation of the brain, spinal cord, roots and peripheral nerves: Basic principles and procedures for routine clinical and research application. An updated report from an I.F.C.N. Committee. Clinical Neurophysiology. 2015;**126**(6):1071- 1107. DOI: 10.1016/j.clinph.2015.02.001

[21] Yozbatiran N, Keser Z, Davis M, Stampas A, O'Malley MK, Cooper-Hay C, et al. Transcranial direct current stimulation (tDCS) of the primary motor cortex and robot-assisted arm training in chronic incomplete cervical spinal cord injury: A proof of concept sham-randomized clinical study. NeuroRehabilitation. 2016;**39**(3): 401-411. DOI: 10.3233/NRE-161371

[22] Kumru H, Murillo N, Benito-Penalva J, Tormos JM, Vidal J.

Letters. 2016;**620**:143-147. DOI: 10.1016/j.neulet.2016.03.056

Westgate PM, Chelette Ii KC, Lee K, et al. Non-invasive brain stimulation and robot-assisted gait training after incomplete spinal cord injury: A randomized pilot study. NeuroRehabilitation. 2016;**38**(1):15-25.

DOI: 10.3233/NRE-151291

Transcranial direct current stimulation is not effective in the motor strength and gait recovery following motor incomplete spinal cord injury during Lokomat(®) gait training. Neuroscience

[23] Raithatha R, Carrico C, Powell ES,

[24] Yamaguchi T, Fujiwara T, Tsai YA, Tang SC, Kawakami M, Mizuno K, et al. The effects of anodal transcranial direct current stimulation and patterned

electrical stimulation on spinal inhibitory interneurons and motor function in patients with spinal cord injury. Experimental Brain Research. 2016;**234**(6):1469-1478. DOI: 10.1007/

[25] Wagner FB, Mignardot JB, Le Goff-Mignardot CG, Demesmaeker R, Komi S, Capogrosso M, et al. Targeted neurotechnology restores walking in humans with spinal cord injury. Nature. 2018;**563**(7729):65-71. DOI: 10.1038/

[26] Gerasimenko Y, Gorodnichev R, Moshonkina T, Sayenko D, Gad P, Reggie Edgerton V. Transcutaneous electrical spinal-cord stimulation in humans. Annals of Physical

s00221-016-4561-4

s41586-018-0649-2

[16] Ellaway PH, Vásquez N, Craggs M. Induction of central nervous system plasticity by repetitive transcranial magnetic stimulation to promote sensorimotor recovery in incomplete spinal cord injury. Frontiers in Integrative Neuroscience. 2014;**8**(42). DOI: 10.3389/fnint.2014.00042

[17] Nitsche MA, Liebetanz D, Lang N,

[18] Gomes-Osman J, Field-Fote EC. Cortical vs. afferent stimulation as an adjunct to functional task practice training: A randomized, comparative pilot study in people with cervical spinal cord injury. Clinical Rehabilitation. 2015;**29**(8):771-782. DOI: 10.1177/0269215514556087

[19] Murray LM, Edwards DJ, Ruffini G, Labar D, Stampas A, Pascual-Leone A, et al. Intensity dependent effects of transcranial direct current stimulation on corticospinal excitability in chronic spinal cord injury. Archives of Physical Medicine and Rehabilitation. 2015;**96** (4 Suppl):S114-S121. DOI: 10.1016/j.

[20] Cortes M, Medeiros AH, Gandhi A,

NeuroRehabilitation. 2017;**41**(1):51-59.

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[44] Mravcsik M, Klauber A, Laczko J. FES driven lower limb cycling by four and eight channel stimulations—A comparison in a case study. In: 12th Vienna International Workshop on Functional Electrical Stimulation. Proceedings Book. 2016. pp. 89-93

[45] Theisen D, Fornusek C, Raymond J, Davis GM. External power output changes during prolonged cycling with electrical stimulation. Journal of Rehabilitation Medicine. 2002;**34**(4):171-175

[46] Eser PC, Donaldson Nde N, Knecht H, Stüssi E. Influence of different stimulation frequencies on power output and fatigue during FES-cycling in recently injured SCI people. IEEE Transactions on Neural Systems and Rehabilitation Engineering. 2003;**11**(3):236-240. DOI: 10.1109/ TNSRE.2003.817677

[47] Szecsi J, Straube A, Fornusek C. A biomechanical cause of low

power production during FES cycling of subjects with SCI. Journal of Neuroengineering and Rehabilitation. 2014;**11**:123. DOI: 10.1186/1743-0003-11-123

[48] Mayr W, Hofer C, Bijak M, Rafolt D, Unger E, Reichel M, et al. Functional electrical stimulation (FES) of denervated muscles: Existing and prospective technological solutions. Basic and Applied Myology. 2002;**12**(6):287-290

[49] Mravcsik M, Kast C, Vargas Luna JL, Aramphianlert W, Hofer C, Malik SZ, et al. FES driven cycling by denervated muscles. In: 22th Annual Conference of the Functional Electrical Stimulation Society. 2018. pp. 134-136

[50] Azevedo Coste C, Wolf P. FEScycling at cybathlon 2016: Overview on teams and results. Artificial Organs. 2018;**42**(3):336-341. DOI: 10.1111/ aor.13139

[51] Berkelmans R, Woods B. Strategies and performances of functional electrical stimulation cycling using the BerkelBike with spinal cord injury in a competition context (CYBATHLON). European Journal of Translational Myology. 2017;**27**(4):255-258. DOI: 10.4081/ejtm.2017.7189

[52] Metani A, Popović-Maneski L, Mateo S, Lemahieu L, Bergeron V. Functional electrical stimulation cycling strategies tested during preparation for the First Cybathlon Competition—A practical report from team ENS de Lyon. European Journal of Translational Myology. 2017;**27**(4):279-288. DOI: 10.4081/ejtm.2017.7110

[53] Fattal C, Sijobert B, Daubigney A, Fachin-Martins E, Lucas B, Casillas JM, et al. Training with FES-assisted cycling in a subject with spinal cord injury: Psychological, physical and physiological considerations. The Journal of Spinal Cord

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actuator with reconfigurable stiffness for a knee exoskeleton: Design and modeling. In: Advances in

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[63] Bortole M, Venkatakrishnan A, Zhu F, Moreno JC, Francisco GE, Pons JL, et al. The H2 robotic exoskeleton for gait rehabilitation after stroke: Early findings from a clinical study. Journal of Neuroengineering and Rehabilitation. 2015;**12**(54). DOI: 10.1186/s12984-015-0048-y

[64] Polygerinos P, Galloway KC, Savage E, Herman M, O'Donnell K, Walsh CJ. Soft robotic glove for hand rehabilitation and task specific training. In: 2015 IEEE International Conference on Robotics and Automation (ICRA). 2015. pp. 2913-2919. DOI: 10.1109/

[65] Contreras-Vidal JL, Bhagat NA, Brantley J, Cruz-Garza JG, He Y, Manley Q, et al. Powered exoskeletons for bipedal locomotion after spinal cord injury. Journal of Neural Engineering. 2016;**13**(3). DOI: 10.1088/1741-2560/13/3/031001

ICRA.2015.7139597

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[54] Peri E, Ambrosini E, Pedrocchi A, Ferrigno G, Nava C, Longoni V, et al. Can FES-augmented active cycling training improve locomotion in post-acute elderly stroke patients? European Journal of Translational Myology. 2016;**26**(3):187-192. DOI:

[55] Wang X, Leung KW, Fang Y, Chen S, Tong RK. Design of functional electrical stimulation cycling system for lower-limb rehabilitation of stroke patients. Conference Proceedings— IEEE Engineering in Medicine and Biology Society. 2018:2337-2340. DOI:

[56] Stampacchia G, Rustici A, Bigazzi S, Gerini A, Tombini T, Mazzoleni S. Walking with a powered robotic exoskeleton: Subjective experience, spasticity and pain in spinal cord injured persons. NeuroRehabilitation. 2016;**39**(2):277-283. DOI: 10.3233/

[57] Moreno JC, Barroso FO, Farina D, Gizzi L, Santos C, Molinari M, et al. Effects of robotic guidance on the coordination of locomotion. Journal of Neuroengineering and Rehabilitation. 2013;**10**:79. DOI: 10.1186/1743-0003-10-79

[58] Hornby TG, Zemon DH, Campbell D. Robotic-assisted, body-weightsupported treadmill training in

individuals following motor incomplete spinal cord injury. Physical Therapy.

comparison of robotic walking therapy and conventional walking therapy in individuals with upper versus lower motor neuron lesions: A randomized

[59] Esclarín-Ruz A, Alcobendas-Maestro M, Casado-Lopez R, Perez-Mateos G, Florido-Sanchez MA, Gonzalez-Valdizan E, et al. A

Medicine. 2018:1-12. DOI: 10.1080/10790268.2018.1490098

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10.1109/EMBC.2018.8512869

NRE-161358

2005;**85**(1):52-66

*Noninvasive Modalities Used in Spinal Cord Injury Rehabilitation DOI: http://dx.doi.org/10.5772/intechopen.83654*

Medicine. 2018:1-12. DOI: 10.1080/10790268.2018.1490098

*Spinal Cord Injury Therapy*

Education/Medical; 2013

of Neural Science. 5h ed. McGraw-Hill

power production during FES cycling of subjects with SCI. Journal

Rehabilitation. 2014;**11**:123. DOI: 10.1186/1743-0003-11-123

[48] Mayr W, Hofer C, Bijak M, Rafolt D, Unger E, Reichel M, et al. Functional electrical stimulation (FES) of denervated muscles: Existing

and prospective technological

2002;**12**(6):287-290

Society. 2018. pp. 134-136

10.4081/ejtm.2017.7189

10.4081/ejtm.2017.7110

aor.13139

[50] Azevedo Coste C, Wolf P. FEScycling at cybathlon 2016: Overview on teams and results. Artificial Organs. 2018;**42**(3):336-341. DOI: 10.1111/

[51] Berkelmans R, Woods B. Strategies and performances of functional electrical stimulation cycling using the BerkelBike with spinal cord injury in a competition context (CYBATHLON). European Journal of Translational Myology. 2017;**27**(4):255-258. DOI:

[52] Metani A, Popović-Maneski L, Mateo S, Lemahieu L, Bergeron V. Functional electrical stimulation cycling strategies tested during preparation for the First Cybathlon Competition—A practical report from team ENS de Lyon. European Journal of Translational Myology. 2017;**27**(4):279-288. DOI:

[53] Fattal C, Sijobert B, Daubigney A, Fachin-Martins E, Lucas B, Casillas JM, et al. Training with FES-assisted cycling in a subject with spinal cord injury: Psychological, physical and physiological considerations. The Journal of Spinal Cord

solutions. Basic and Applied Myology.

[49] Mravcsik M, Kast C, Vargas Luna JL, Aramphianlert W, Hofer C, Malik SZ, et al. FES driven cycling by denervated muscles. In: 22th Annual Conference of the Functional Electrical Stimulation

of Neuroengineering and

[41] Koutsou AD, Moreno JC, Del Ama AJ, Rocon E, Pons JL. Advances in selective activation of muscles for non-invasive motor neuroprostheses. Journal of Neuroengineering and Rehabilitation. 2016;**13**(56). DOI: 10.1186/s12984-016-0165-2

[42] Hunt KJ, Ferrario C, Grant S, Stone B, McLean AN, Fraser MH, et al. Comparison of stimulation patterns for FES-cycling using measures of oxygen cost and stimulation cost. Medical Engineering & Physics. 2006;**28**(7):710-718. DOI: 10.1016/j.

[43] Laczko J, Mravcsik M, Katona P. Control of cycling limb movements: Aspects for rehabilitation. Advances in Experimental Medicine and Biology. 2016;**957**:273-289. DOI: 10.1007/978-3-319-47313-0\_15

[44] Mravcsik M, Klauber A, Laczko J. FES driven lower limb cycling by four and eight channel stimulations—A comparison in a case study. In: 12th Vienna International Workshop on Functional Electrical Stimulation. Proceedings Book. 2016. pp. 89-93

[45] Theisen D, Fornusek C, Raymond J, Davis GM. External power output changes during prolonged cycling with electrical stimulation. Journal

[46] Eser PC, Donaldson Nde N, Knecht H, Stüssi E. Influence of different stimulation frequencies on power output and fatigue during FES-cycling in recently injured SCI people. IEEE Transactions on Neural Systems and Rehabilitation Engineering. 2003;**11**(3):236-240. DOI: 10.1109/

[47] Szecsi J, Straube A, Fornusek C. A biomechanical cause of low

of Rehabilitation Medicine.

2002;**34**(4):171-175

TNSRE.2003.817677

medengphy.2005.10.006

**112**

[54] Peri E, Ambrosini E, Pedrocchi A, Ferrigno G, Nava C, Longoni V, et al. Can FES-augmented active cycling training improve locomotion in post-acute elderly stroke patients? European Journal of Translational Myology. 2016;**26**(3):187-192. DOI: 10.4081/ejtm.2016.6063

[55] Wang X, Leung KW, Fang Y, Chen S, Tong RK. Design of functional electrical stimulation cycling system for lower-limb rehabilitation of stroke patients. Conference Proceedings— IEEE Engineering in Medicine and Biology Society. 2018:2337-2340. DOI: 10.1109/EMBC.2018.8512869

[56] Stampacchia G, Rustici A, Bigazzi S, Gerini A, Tombini T, Mazzoleni S. Walking with a powered robotic exoskeleton: Subjective experience, spasticity and pain in spinal cord injured persons. NeuroRehabilitation. 2016;**39**(2):277-283. DOI: 10.3233/ NRE-161358

[57] Moreno JC, Barroso FO, Farina D, Gizzi L, Santos C, Molinari M, et al. Effects of robotic guidance on the coordination of locomotion. Journal of Neuroengineering and Rehabilitation. 2013;**10**:79. DOI: 10.1186/1743-0003-10-79

[58] Hornby TG, Zemon DH, Campbell D. Robotic-assisted, body-weightsupported treadmill training in individuals following motor incomplete spinal cord injury. Physical Therapy. 2005;**85**(1):52-66

[59] Esclarín-Ruz A, Alcobendas-Maestro M, Casado-Lopez R, Perez-Mateos G, Florido-Sanchez MA, Gonzalez-Valdizan E, et al. A comparison of robotic walking therapy and conventional walking therapy in individuals with upper versus lower motor neuron lesions: A randomized

controlled trial. Archives of Physical Medicine and Rehabilitation. 2014;**95**(6):1023-1031. DOI: 10.1016/j. apmr.2013.12.017

[60] Nam KY, Kim HJ, Kwon BS, Park JW, Lee HJ, Yoo A. Robot-assisted gait training (Lokomat) improves walking function and activity in people with spinal cord injury: A systematic review. Journal of Neuroengineering and Rehabilitation. 2017;**14**(1). DOI: 10.1186/s12984-017-0232-3

[61] Pons JL. Wearable Robots: Biomechatronic Exoskeletons. John Wiley & Sons; 2008

[62] Karavas NC, Tsagarakis NG, Saglia J, Galdwell DG. A novel actuator with reconfigurable stiffness for a knee exoskeleton: Design and modeling. In: Advances in Reconfigurable Mechanisms and Robots I. Springer; 2012. pp. 411-421. DOI: 10.1007/978-1-4471-4141-9\_37

[63] Bortole M, Venkatakrishnan A, Zhu F, Moreno JC, Francisco GE, Pons JL, et al. The H2 robotic exoskeleton for gait rehabilitation after stroke: Early findings from a clinical study. Journal of Neuroengineering and Rehabilitation. 2015;**12**(54). DOI: 10.1186/s12984-015-0048-y

[64] Polygerinos P, Galloway KC, Savage E, Herman M, O'Donnell K, Walsh CJ. Soft robotic glove for hand rehabilitation and task specific training. In: 2015 IEEE International Conference on Robotics and Automation (ICRA). 2015. pp. 2913-2919. DOI: 10.1109/ ICRA.2015.7139597

[65] Contreras-Vidal JL, Bhagat NA, Brantley J, Cruz-Garza JG, He Y, Manley Q, et al. Powered exoskeletons for bipedal locomotion after spinal cord injury. Journal of Neural Engineering. 2016;**13**(3). DOI: 10.1088/1741-2560/13/3/031001

[66] Asín-Prieto G, Martínez-Expósito A, Alnajjar F, Shimoda S, Pons JL, Moreno JC. Feasibility of submaximal force control training for robot– mediated therapy after stroke. In: Converging Clinical and Engineering Research on Neurorehabilitation III; 2019. pp. 256-260. DOI: 10.1007/978-3-030-01845-0\_51

[67] Gassert R, Dietz V. Rehabilitation robots for the treatment of sensorimotor deficits: A neurophysiological perspective. Journal of Neuroengineering and Rehabilitation. 2018;**15**(1). DOI: 10.1186/s12984-018-0383-x

[68] Niu X, Varoqui D, Kindig M, Mirbagheri MM. Prediction of gait recovery in spinal cord injured individuals trained with robotic gait orthosis. Journal of Neuroengineering and Rehabilitation. 2014;**11**:42. DOI: 10.1186/1743-0003-11-42

[69] Andrews BJ, Baxendale RH, Barnett R, Phillips GF, Yamazaki T, Paul JP, et al. Hybrid FES orthosis incorporating closed loop control and sensory feedback. Journal of Biomedical Engineering. 1988;**10**(2):189-195

[70] del-Ama AJ, Koutsou AD, Moreno JC, de-los-Reyes A, Gil-Agudo A, Pons JL. Review of hybrid exoskeletons to restore gait following spinal cord injury. Journal of Rehabilitation Research and Development. 2012;**49**(4):497-514

[71] Kobetic R, Marsolais EB, Triolo RJ, Davy DT, Gaudio R, Tashman S. Development of a hybrid gait orthosis: A case report. The Journal of Spinal Cord Medicine. 2003;**26**(3):254-258

[72] del-Ama AJ, Gil-Agudo A, Pons JL, Moreno JC. Hybrid FES-robot cooperative control of ambulatory gait rehabilitation exoskeleton. Journal of Neuroengineering and Rehabilitation. 2014;**11**:27. DOI: 10.1186/1743-0003-11-27

[73] Ha KH, Murray SA, Goldfarb M. An approach for the cooperative control of FES with a powered exoskeleton during level walking for persons with paraplegia. IEEE Transactions on Neural Systems and Rehabilitation Engineering. 2016;**24**(4):455-466. DOI: 10.1109/ TNSRE.2015.2421052

[74] Kurokawa N, Yamamoto N, Tagawa Y, Yamamoto T, Kuno H. Development of hybrid FES walking assistive system—Feasibility study. In: The 2012 International Conference on Advanced Mechatronic Systems. 2012. pp. 93-97

[75] Goldfarb M, Durfee WK. Design of a controlled-brake orthosis for FES-aided gait. IEEE Transactions on Rehabilitation Engineering. 1996;**4**(1):13-24

[76] Gharooni S, Heller B, Tokhi MO. A new hybrid spring brake orthosis for controlling hip and knee flexion in the swing phase. IEEE Transactions on Neural Systems and Rehabilitation Engineering. 2001;**9**(1):106-107

[77] Goldfarb M, Korkowski K, Harrold B, Durfee W. Preliminary evaluation of a controlled-brake orthosis for FESaided gait. IEEE Transactions on Neural Systems and Rehabilitation Engineering. 2003;**11**(3):241-248. DOI: 10.1109/ TNSRE.2003.816873

[78] Barroso FO, Santos C, Moreno JC. Influence of the robotic exoskeleton Lokomat on the control of human gait: An electromyographic and kinematic analysis. In: 2013 IEEE 3rd Portuguese Meeting in Bioengineering (ENBENG). 2013. DOI: 10.1109/ ENBENG.2013.6518442

**115**

**Chapter 7**

**Abstract**

chapter of this book.

**1. Introduction**

**Keywords:** spinal cord injury, cultured cells, therapy

Transplantation or Transference of

Cultured Cells as a Treatment for

*Roxana Rodríguez-Barrera, Karla Soria-Zavala,* 

*Julián García-Sánchez, Lisset Karina Navarro-Torres,* 

*Estefanía de la Cruz Castillo and Elisa García-Vences*

Spinal cord injury (SCI) involves damage to the spinal cord causing both structural and functional changes, which can lead to temporary or permanent alterations. Even though there have been many advances in its treatment, the results of clinical trials suggest that the current therapies are not sufficiently effective. Recently, there has been a lot of interest in regulating this harmful environment by transplanting cultured cells and boosting their antiinflammatory cytokines and growth factors production. Several types of cells have been studied for SCI therapy including, Schwann cells (SC's), olfactory ensheathing cells (OECs), choroid plexus epithelial cells (CPECs), and immune cells (ICs) (lymphocytes, dendritic cells and alternative macrophage and microglia phenotypes). These treatments have shown to be promising and in this chapter, we will review the general aspects of transplanting these cells for SCI therapy as well as the neuroprotective and regenerative responses that different types of cells have reached in different SCI models. The mesenchymal stem cells (MSC) are one of the most well studied cell types; however, they were not included in this section because they will be reviewed in another

SCI is a catastrophic condition that goes through two successive stages, which involves disturbances on ionic homeostasis, local edema, ischemia, focal hemorrhage, free radicals stress and inflammatory response [1]. SCI also causes partial or complete loss of sensory, motor and autonomic functions below the injury level, due to the interruption of the neural pathways. Nevertheless, cultured cells have successfully proved to achieve neuroprotective effects, by replacing or repairing damaged tissue, by neuronal survival, axonal growth, regulation of cytokine profiles and inflammation and motor recovery in animal models [2]. Cultured cells are promising strategies due to high variety of autologous cells that can be isolated and transplanted to patients; neural cells can up-regulate neurotrophic, growth and vascular factors to enhance the repair process in the spinal cord (SC). Also,

Spinal Cord Injury

#### **Chapter 7**

*Spinal Cord Injury Therapy*

[66] Asín-Prieto G, Martínez-Expósito A, Alnajjar F, Shimoda S, Pons JL, Moreno JC. Feasibility of submaximal force control training for robot– mediated therapy after stroke. In: Converging Clinical and Engineering Research on Neurorehabilitation III; 2019. pp. 256-260. DOI: 10.1007/978-3-030-01845-0\_51

[73] Ha KH, Murray SA, Goldfarb M. An approach for the cooperative control of FES with a powered exoskeleton during level walking for persons with paraplegia. IEEE Transactions on Neural Systems and Rehabilitation Engineering. 2016;**24**(4):455-466. DOI: 10.1109/

[74] Kurokawa N, Yamamoto N, Tagawa Y, Yamamoto T, Kuno H. Development of hybrid FES walking assistive

system—Feasibility study. In: The 2012 International Conference on Advanced Mechatronic Systems. 2012. pp. 93-97

[75] Goldfarb M, Durfee WK. Design of a controlled-brake orthosis for FES-aided gait. IEEE Transactions on Rehabilitation Engineering.

[76] Gharooni S, Heller B, Tokhi MO. A new hybrid spring brake orthosis for controlling hip and knee flexion in the swing phase. IEEE Transactions on Neural Systems and Rehabilitation Engineering. 2001;**9**(1):106-107

[77] Goldfarb M, Korkowski K, Harrold B, Durfee W. Preliminary evaluation of a controlled-brake orthosis for FESaided gait. IEEE Transactions on Neural Systems and Rehabilitation Engineering. 2003;**11**(3):241-248. DOI: 10.1109/

[78] Barroso FO, Santos C, Moreno JC. Influence of the robotic exoskeleton Lokomat on the control of human gait: An electromyographic and kinematic analysis. In: 2013 IEEE 3rd Portuguese Meeting in Bioengineering (ENBENG). 2013. DOI: 10.1109/

TNSRE.2015.2421052

1996;**4**(1):13-24

TNSRE.2003.816873

ENBENG.2013.6518442

[67] Gassert R, Dietz V. Rehabilitation robots for the treatment of sensorimotor

perspective. Journal of Neuroengineering and Rehabilitation. 2018;**15**(1). DOI:

deficits: A neurophysiological

10.1186/s12984-018-0383-x

10.1186/1743-0003-11-42

[69] Andrews BJ, Baxendale RH, Barnett R, Phillips GF, Yamazaki T, Paul JP, et al. Hybrid FES orthosis incorporating closed loop control and sensory feedback. Journal of Biomedical

Engineering. 1988;**10**(2):189-195

[70] del-Ama AJ, Koutsou AD, Moreno JC, de-los-Reyes A, Gil-Agudo A, Pons JL. Review of hybrid exoskeletons to restore gait following spinal cord injury. Journal of Rehabilitation Research and Development. 2012;**49**(4):497-514

[71] Kobetic R, Marsolais EB, Triolo RJ, Davy DT, Gaudio R, Tashman S. Development of a hybrid gait orthosis: A case report. The Journal of Spinal Cord Medicine. 2003;**26**(3):254-258

[72] del-Ama AJ, Gil-Agudo A, Pons JL,

Moreno JC. Hybrid FES-robot cooperative control of ambulatory gait rehabilitation exoskeleton. Journal of Neuroengineering and Rehabilitation. 2014;**11**:27. DOI: 10.1186/1743-0003-11-27

[68] Niu X, Varoqui D, Kindig M, Mirbagheri MM. Prediction of gait recovery in spinal cord injured individuals trained with robotic gait orthosis. Journal of Neuroengineering and Rehabilitation. 2014;**11**:42. DOI:

**114**

## Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury

*Roxana Rodríguez-Barrera, Karla Soria-Zavala, Julián García-Sánchez, Lisset Karina Navarro-Torres, Estefanía de la Cruz Castillo and Elisa García-Vences*

### **Abstract**

Spinal cord injury (SCI) involves damage to the spinal cord causing both structural and functional changes, which can lead to temporary or permanent alterations. Even though there have been many advances in its treatment, the results of clinical trials suggest that the current therapies are not sufficiently effective. Recently, there has been a lot of interest in regulating this harmful environment by transplanting cultured cells and boosting their antiinflammatory cytokines and growth factors production. Several types of cells have been studied for SCI therapy including, Schwann cells (SC's), olfactory ensheathing cells (OECs), choroid plexus epithelial cells (CPECs), and immune cells (ICs) (lymphocytes, dendritic cells and alternative macrophage and microglia phenotypes). These treatments have shown to be promising and in this chapter, we will review the general aspects of transplanting these cells for SCI therapy as well as the neuroprotective and regenerative responses that different types of cells have reached in different SCI models. The mesenchymal stem cells (MSC) are one of the most well studied cell types; however, they were not included in this section because they will be reviewed in another chapter of this book.

**Keywords:** spinal cord injury, cultured cells, therapy

#### **1. Introduction**

SCI is a catastrophic condition that goes through two successive stages, which involves disturbances on ionic homeostasis, local edema, ischemia, focal hemorrhage, free radicals stress and inflammatory response [1]. SCI also causes partial or complete loss of sensory, motor and autonomic functions below the injury level, due to the interruption of the neural pathways. Nevertheless, cultured cells have successfully proved to achieve neuroprotective effects, by replacing or repairing damaged tissue, by neuronal survival, axonal growth, regulation of cytokine profiles and inflammation and motor recovery in animal models [2]. Cultured cells are promising strategies due to high variety of autologous cells that can be isolated and transplanted to patients; neural cells can up-regulate neurotrophic, growth and vascular factors to enhance the repair process in the spinal cord (SC). Also,

non-neural cells can be polarized in vitro to evoke antiinflamatory responses in order to modulate SCI microenvironment. This still requires intensive investigation because cells from neural tissues such as OECs could only be retrieved by craniotomy with general anesthesia, which needs, optimized chirurgical practices and excellent preclinical and clinical cares [3]. However, mononuclear cells such as macrophages or lymphocytes isolated from peripheral blood, become a less invasive strategy [4, 5]. Although the current treatments for SCI have proven to have certain improvement effects, there is no actual cure for SCI [6]. That is why in recent years cell transplantation has become one of the most investigated approaches to treat this kind of disorder [7, 8].

#### **2. Cultured cells**

In this section, we will review each cell type separately because there are many differences and similarities among them which are worth mentioning.

#### **2.1 Schwann cells**

Numerous cell types have been studied and proposed for transplantation, however, SC's have always been considered as one of the best candidates for this treatment [9–11].

SC's are the principal glia of the peripheral nervous system (PNS) [12]. SC's wrap around long segments of peripheral nerves and produce myelin, forming a multilayered membranous sheath that allows axons to propagate action potentials at a high speed [12, 13]. The myelination of the axons by glial cells (oligodendrocytes in the central nervous system (CNS) and SC's in the PNS) is believed to be the last evolutionary step in the vertebrae nervous system and it's key in understanding neurophysiology [12, 14]. There are two types of SC's, the myelinating and nonmyelinating both come from the neural crest cells in early development stages [15]. SC's precursors migrate along with growing axons in peripheral nerves where they receive specific signaling such as Neuregulin 1 (NRG 1) in order to survive and later on differentiate into myelinating SC's [15, 16].

SC's are essential for normal motor and cognitive functions, long-time integrity of the axons and they play a crucial role in axonal regeneration in the PNS after injury [6, 14, 17]. SC's regeneration role is more evident when you compare the outcome of a blunt injury in the SC with a similar injury in a peripheral nerve in rodents [18]. In several studies, it was seen that after sciatic nerve crush, the axons were able to rapidly grow back to their targets, also redundant myelin was removed and replaced with new myelin surrounding the regenerated axons, resulting in a generally normal tissue at an impressive speed (3–4 weeks) [14, 19]. On the other hand, crushing the SC results in the formation of a lesion filled with fluid or matrix leading to axonal retraction, permanency of myelin debris and absence of axonal regeneration [20]. In the PNS, the injury triggers a broad set of changes in the differentiation of both injured neurons and SC's, causing neurons to switch their function from cell to cell signaling to axonal growth and SC's change their function from axonal maintenance to support axonal regeneration [18, 21, 22]. This means that the glia in CNS does not suffer the same remarkable transformation as the PNS to repair the nervous tissue after the injury [19].

Those are some characteristic that have led them to become one of the biggest proposed treatments in cell transplants seeking to recover motor functions after SCI [9, 11].

**117**

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury*

Even though axonal degeneration in the distal stump takes about 2–4 days, SC's response to axonal damage can be detected within hours of the injury, suggesting there is some communication between injured axons and SC's which needs further investigation [23]. As said before, right after de injury, SC's and undergo a large series of changes in gene expression to dedifferentiate into a non-myelinating immature type of SC's and proliferate extensively [24]. In this process myelin associated molecules such as the key myelin transcription factor Egr2 (Krox20), cholesterol synthesis enzymes, structural proteins, including P0, myelin basic protein (MBP), and membrane-associated proteins like myelin-associated glycoprotein (MAG) and periaxin are down-regulated, whereas molecules that characterize SC's in their immature stage (before myelination) are up-regulated [25]. These include L1, Neural cell adhesion molecule (NCAM), neurotrophin receptor p75NTR, and

Another process in this response is the presence of phenotypes which are not associated neither with immature SCs nor with the SCs of an undamaged nerve. The appearance of these cells is critical, and since their main function is repairing, we refer to them as repair SC's or Bungner cells (BC's) [24]. The repair process includes, first, the up-regulation of neurotrophic factors such as, Glial cell-derived neurotrophic factor (GDNF), artemin, Brain-derived neurotrophic factor (BDNF), Neurotrophin-3 (NT3), Nerve growth factor (NGF), Vascular endothelial growth factor (VEGF), and pleiotrophin which promotes the survival of injured neurons and axonal regeneration [26]. Second, the BC's up-regulates the expression of inflammatory cytokines including tumor necrosis factor (TNF)-a, interleukin (IL)-1a,IL-1b, Leukemia inhibitory factor (LIF), and Monocyte chemoattractant protein-1 (MCP-1), in order to recruit macrophages that will eliminate redundant

One of the first clues implicating that SC's transplantation could serve as a treatment for SCI was found in a set of experiments held by David and Aguayo in 1981. The experiments demonstrated that peripheral neurons (PN) lose their ability to regenerate over long distances in the PNS when they are submitted within the environment of a CNS graft and contrariwise the limited ability of CNS neurons to regenerate after an injury was enhanced within the environment of a PNS graft [19, 28]. Thanks to those landmark studies and decades of research, we now know that the introduction of SC's after a SCI can promote axonal regeneration, reduce tissue loss, and facilitate myelination of axons in order to improve sensory motor

One of the best-known mechanisms by which SC's promotes axonal regeneration

The PN-auto graft was one of the first techniques to promote axonal regeneration in the CNS after SCI. The nerve graft, besides providing supportive SCs it also endorses the survival of axotomized SC neurons by upregulating the expression of neuronal nitric oxide synthase (eNOS), furtherly activating the NO- dependent

cyclic-GMP pathway, which enhances survival in these neurons [32, 33].

is by the formation of bridges across the lesion site. The bridge is a multicellular structure that crosses the lesion rostrally to caudally, providing an environment in which axons can grow and also covering the glial scar which limits axonal regeneration [31]. Furthermore, the transplantation of SCs provides a neuroprotective effect preventing neuronal death from the continuous inflammatory reaction involved in

*DOI: http://dx.doi.org/10.5772/intechopen.84645*

glial fibrillary acidic protein (GFAP) [24].

myelin that inhibit axonal growth [27].

function [11, 29, 30].

the SCI [10, 11].

*2.1.2 Schwann cell transplantation in spinal cord injury*

*2.1.1 Schwann cell response to injury*

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.84645*

#### *2.1.1 Schwann cell response to injury*

*Spinal Cord Injury Therapy*

this kind of disorder [7, 8].

**2. Cultured cells**

**2.1 Schwann cells**

treatment [9–11].

on differentiate into myelinating SC's [15, 16].

non-neural cells can be polarized in vitro to evoke antiinflamatory responses in order to modulate SCI microenvironment. This still requires intensive investigation because cells from neural tissues such as OECs could only be retrieved by craniotomy with general anesthesia, which needs, optimized chirurgical practices and excellent preclinical and clinical cares [3]. However, mononuclear cells such as macrophages or lymphocytes isolated from peripheral blood, become a less invasive strategy [4, 5]. Although the current treatments for SCI have proven to have certain improvement effects, there is no actual cure for SCI [6]. That is why in recent years cell transplantation has become one of the most investigated approaches to treat

In this section, we will review each cell type separately because there are many

Numerous cell types have been studied and proposed for transplantation, however, SC's have always been considered as one of the best candidates for this

SC's are the principal glia of the peripheral nervous system (PNS) [12]. SC's wrap around long segments of peripheral nerves and produce myelin, forming a multilayered membranous sheath that allows axons to propagate action potentials at a high speed [12, 13]. The myelination of the axons by glial cells (oligodendrocytes in the central nervous system (CNS) and SC's in the PNS) is believed to be the last evolutionary step in the vertebrae nervous system and it's key in understanding neurophysiology [12, 14]. There are two types of SC's, the myelinating and nonmyelinating both come from the neural crest cells in early development stages [15]. SC's precursors migrate along with growing axons in peripheral nerves where they receive specific signaling such as Neuregulin 1 (NRG 1) in order to survive and later

SC's are essential for normal motor and cognitive functions, long-time integrity of the axons and they play a crucial role in axonal regeneration in the PNS after injury [6, 14, 17]. SC's regeneration role is more evident when you compare the outcome of a blunt injury in the SC with a similar injury in a peripheral nerve in rodents [18]. In several studies, it was seen that after sciatic nerve crush, the axons were able to rapidly grow back to their targets, also redundant myelin was removed and replaced with new myelin surrounding the regenerated axons, resulting in a generally normal tissue at an impressive speed (3–4 weeks) [14, 19]. On the other hand, crushing the SC results in the formation of a lesion filled with fluid or matrix leading to axonal retraction, permanency of myelin debris and absence of axonal regeneration [20]. In the PNS, the injury triggers a broad set of changes in the differentiation of both injured neurons and SC's, causing neurons to switch their function from cell to cell signaling to axonal growth and SC's change their function from axonal maintenance to support axonal regeneration [18, 21, 22]. This means that the glia in CNS does not suffer the same remarkable transformation as the PNS to repair the nervous tissue after

Those are some characteristic that have led them to become one of the biggest proposed treatments in cell transplants seeking to recover motor functions after SCI

differences and similarities among them which are worth mentioning.

**116**

[9, 11].

the injury [19].

Even though axonal degeneration in the distal stump takes about 2–4 days, SC's response to axonal damage can be detected within hours of the injury, suggesting there is some communication between injured axons and SC's which needs further investigation [23]. As said before, right after de injury, SC's and undergo a large series of changes in gene expression to dedifferentiate into a non-myelinating immature type of SC's and proliferate extensively [24]. In this process myelin associated molecules such as the key myelin transcription factor Egr2 (Krox20), cholesterol synthesis enzymes, structural proteins, including P0, myelin basic protein (MBP), and membrane-associated proteins like myelin-associated glycoprotein (MAG) and periaxin are down-regulated, whereas molecules that characterize SC's in their immature stage (before myelination) are up-regulated [25]. These include L1, Neural cell adhesion molecule (NCAM), neurotrophin receptor p75NTR, and glial fibrillary acidic protein (GFAP) [24].

Another process in this response is the presence of phenotypes which are not associated neither with immature SCs nor with the SCs of an undamaged nerve. The appearance of these cells is critical, and since their main function is repairing, we refer to them as repair SC's or Bungner cells (BC's) [24]. The repair process includes, first, the up-regulation of neurotrophic factors such as, Glial cell-derived neurotrophic factor (GDNF), artemin, Brain-derived neurotrophic factor (BDNF), Neurotrophin-3 (NT3), Nerve growth factor (NGF), Vascular endothelial growth factor (VEGF), and pleiotrophin which promotes the survival of injured neurons and axonal regeneration [26]. Second, the BC's up-regulates the expression of inflammatory cytokines including tumor necrosis factor (TNF)-a, interleukin (IL)-1a,IL-1b, Leukemia inhibitory factor (LIF), and Monocyte chemoattractant protein-1 (MCP-1), in order to recruit macrophages that will eliminate redundant myelin that inhibit axonal growth [27].

#### *2.1.2 Schwann cell transplantation in spinal cord injury*

One of the first clues implicating that SC's transplantation could serve as a treatment for SCI was found in a set of experiments held by David and Aguayo in 1981. The experiments demonstrated that peripheral neurons (PN) lose their ability to regenerate over long distances in the PNS when they are submitted within the environment of a CNS graft and contrariwise the limited ability of CNS neurons to regenerate after an injury was enhanced within the environment of a PNS graft [19, 28]. Thanks to those landmark studies and decades of research, we now know that the introduction of SC's after a SCI can promote axonal regeneration, reduce tissue loss, and facilitate myelination of axons in order to improve sensory motor function [11, 29, 30].

One of the best-known mechanisms by which SC's promotes axonal regeneration is by the formation of bridges across the lesion site. The bridge is a multicellular structure that crosses the lesion rostrally to caudally, providing an environment in which axons can grow and also covering the glial scar which limits axonal regeneration [31]. Furthermore, the transplantation of SCs provides a neuroprotective effect preventing neuronal death from the continuous inflammatory reaction involved in the SCI [10, 11].

The PN-auto graft was one of the first techniques to promote axonal regeneration in the CNS after SCI. The nerve graft, besides providing supportive SCs it also endorses the survival of axotomized SC neurons by upregulating the expression of neuronal nitric oxide synthase (eNOS), furtherly activating the NO- dependent cyclic-GMP pathway, which enhances survival in these neurons [32, 33].

In addition, the PN-grafts promote the expression of growth factors in the host SC such as NGF and BDNF, delaying the formation of the glial scar, which is key for successful regeneration [34]. Another studied strategy is transplanting dissociated SCs alone into the injury. After transplantation, dissociated SCs are able to elicit axonal in-growth and align to secrete substrates, serving as guidance for axonal regeneration [35]. Moreover, when it comes to transplanting, the SCs alone have an advantage over the PN-graft, which is that purified SCs have the potential of being engineered to overexpress growth-promoting factors and/or adhesion molecules to enhance axon growth [36]. Even though several studies indicate that they cannot migrate into the host tissue, therefore regeneration outside the injury/graft site was limited [37].

However, their repair effect is not enough to induce an axonal response that leads to a full recovery of the locomotor function [38]. This could be due to the fact that a high percentage of SCs are lost in apoptotic or necrotic processes in the first 3 weeks after transplant [39]. This low survival rate post transplantation may be attributed to the prejudicial environment of the SCI in which low oxygen levels, inflammatory cytokines, reactive oxygen species (ROS) and cell-mediated immune reactions predominate [10, 39]. Also, after the injury reactive astrocytes, meningeal cells, and microglia form the glial scar which becomes a physical and chemical barrier for axons to grow. The glial scar induces the secretion of axonal growth and myelin-associated inhibitors such as chondroitin sulfate proteoglycans (CSPGs), semaphorins, and myelin-associated proteins which limits the regenerative capacity of SCs when transplanted alone [37]. This suggests that SC transplantation needs to be combined with additional interventions in order to ensure successful axonal regeneration and sufficient functional recovery after SCI [29].

Because of the multiple mechanisms and complex pathophysiology involved in SCI, a significant therapeutic effect on functional recovery may not occur with the transplantation of SCs alone, meaning that a combinational therapy strategy is most likely to be the best option [9]. There are many different strategies that have been studied and have shown to have beneficial results. First, the suspension of SCs in bioactive matrices promotes their survival and enhances their capacity for supporting axonal regeneration. Second, the complementary administration of neuroprotective agents, growth factors and other molecules improves the effects of SCs at the lesion site. Third, the inhibition of the glial scar formation and/or the reduction of its inhibitory cues to obtain axonal growth from grafts into the adjacent SC. Fourth, the co-transplantation of SCs with other cell types such as OECs, neural stem cells (NSCs), MSC and others. The different types of combinations as well as their characteristics and outcomes are described in **Table 1**.

The use of another cell population like OECs in the combinatory cell therapy had demonstrated to boost the SCs effects.

#### **2.2 Olfactory ensheathing cells**

OECs are a population of glia cells that are residents in the PNS and CNS, which are commonly located in the central olfactory bulb (OB) and the nasal olfactory mucosa (OM) [56]. They are accompanied by the envelope of olfactory nerve fibroblasts (ONFs), so they can embrace the bundles of olfactory nerve fibers from the nasal mucosa to allow the synapsis in the OB [57]. Recent studies have demonstrated that OB transplants could be differentiated to create relationships with the periphery and brain [56].

OECs express a lot of neurotrophic factors, including BDNF, GDNF, and NGF which are relevant for the propagations and guidance of axons, sharing properties with astrocytes and SC's [2]. Neurotrophic factors secreted by them is capable

**119**

and CNS.

**Table 1.**

and inhibitory factors.

implicated in that process (**Table 2**) [2, 59].

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury*

Matrigel (BD) Significantly enhances long-term cell survival as well as graft

astrogliosis and locomotor impairment.

PuraMatrix (BD) Promotes their survival in the injured SC and reduces

function.

Alginic acid hydrogel Reduces SC apoptosis and enhances recovery of locomotor

GDNF Reduces astrogliosis and promotes axon regeneration, synapse

NRG1 + MSC Reduce the size of cystic cavities, promotes axonal regeneration and locomotor recovery.

sparing/regeneration and myelination.

and significantly improves locomotion.

formation below the lesion/implant.

ChABC Compared grafts treatment, it also improves forelimb and

Polysialic acid This leads to improved SC migration, axon regeneration, and

MSC Reduction of the size the size of cystic cavities, promotes axonal

MSC transplantation alone.

NSC Promotes neuronal differentiation and functional recovery in

OECs Regeneration of both proprio- and supra-spinal axons beyond

myelination, and reduces neuronal loss.

locomotion.

after SCI in rats.

the SC bridge.

locomotion.

*Combination of SCs transplantation with novel molecules/materials.*

formation, and locomotor recovery after SCI

Promote significant supraspinal and proprioceptive axon

Increases the size of SC grafts, the number of serotonergic fibers in the grafts, and the number of axons from the reticular

hindlimb movements as well as open-field locomotion. Decreases CSPGs both outside and within the SC transplant.

regeneration and locomotor recovery compared with SCs or

Improves locomotion, increases axonal regeneration/

Significantly promotes axonal regeneration and improves

Promotes growth of serotonergic fibers into and beyond grafts,

vascularization and the amount of axonal ingrowth

**Outcome Reference**

[40]

[41]

[42]

[43, 44]

[45]

[6] [6] [46]

[47] [5, 48],

[49, 50]

[45]

[51] [52, 53]

[54] [55]

of protecting neurons, due to its faculty to inhibit scar formation and promote regeneration of axons (see **Table 2**) [58]. They also have an important ability in neural regeneration that consists in their proliferation and migration from PNS

This attribute explains that enhancement of axonal extension after injury is possible and it can help neural regeneration, as a result of the expression of molecules

OECs phenotypes are different depending on their location in CNS or PNS. It has been shown that they express different types of molecules implicated in neuroregeneration, such as adhesion molecules, neurotrophic factors, proteases, cytokines

*DOI: http://dx.doi.org/10.5772/intechopen.84645*

Suspension matrices

Growth factors and other molecules

Inhibition of the glial scar formation

Rolipram + SCs grafts/ analog of cyclic AMP/

Combination cells

D15A

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.84645*


#### **Table 1.**

*Spinal Cord Injury Therapy*

limited [37].

In addition, the PN-grafts promote the expression of growth factors in the host SC such as NGF and BDNF, delaying the formation of the glial scar, which is key for successful regeneration [34]. Another studied strategy is transplanting dissociated SCs alone into the injury. After transplantation, dissociated SCs are able to elicit axonal in-growth and align to secrete substrates, serving as guidance for axonal regeneration [35]. Moreover, when it comes to transplanting, the SCs alone have an advantage over the PN-graft, which is that purified SCs have the potential of being engineered to overexpress growth-promoting factors and/or adhesion molecules to enhance axon growth [36]. Even though several studies indicate that they cannot migrate into the host tissue, therefore regeneration outside the injury/graft site was

However, their repair effect is not enough to induce an axonal response that leads to a full recovery of the locomotor function [38]. This could be due to the fact that a high percentage of SCs are lost in apoptotic or necrotic processes in the first 3 weeks after transplant [39]. This low survival rate post transplantation may be attributed to the prejudicial environment of the SCI in which low oxygen levels, inflammatory cytokines, reactive oxygen species (ROS) and cell-mediated immune reactions predominate [10, 39]. Also, after the injury reactive astrocytes, meningeal cells, and microglia form the glial scar which becomes a physical and chemical barrier for axons to grow. The glial scar induces the secretion of axonal growth and myelin-associated inhibitors such as chondroitin sulfate proteoglycans (CSPGs), semaphorins, and myelin-associated proteins which limits the regenerative capacity of SCs when transplanted alone [37]. This suggests that SC transplantation needs to be combined with additional interventions in order to ensure successful axonal

Because of the multiple mechanisms and complex pathophysiology involved in SCI, a significant therapeutic effect on functional recovery may not occur with the transplantation of SCs alone, meaning that a combinational therapy strategy is most likely to be the best option [9]. There are many different strategies that have been studied and have shown to have beneficial results. First, the suspension of SCs in bioactive matrices promotes their survival and enhances their capacity for supporting axonal regeneration. Second, the complementary administration of neuroprotective agents, growth factors and other molecules improves the effects of SCs at the lesion site. Third, the inhibition of the glial scar formation and/or the reduction of its inhibitory cues to obtain axonal growth from grafts into the adjacent SC. Fourth, the co-transplantation of SCs with other cell types such as OECs, neural stem cells (NSCs), MSC and others. The different types of combinations as well as their

The use of another cell population like OECs in the combinatory cell therapy had

OECs are a population of glia cells that are residents in the PNS and CNS, which are commonly located in the central olfactory bulb (OB) and the nasal olfactory mucosa (OM) [56]. They are accompanied by the envelope of olfactory nerve fibroblasts (ONFs), so they can embrace the bundles of olfactory nerve fibers from the nasal mucosa to allow the synapsis in the OB [57]. Recent studies have demonstrated that OB transplants could be differentiated to create relationships with the

OECs express a lot of neurotrophic factors, including BDNF, GDNF, and NGF which are relevant for the propagations and guidance of axons, sharing properties with astrocytes and SC's [2]. Neurotrophic factors secreted by them is capable

regeneration and sufficient functional recovery after SCI [29].

characteristics and outcomes are described in **Table 1**.

demonstrated to boost the SCs effects.

**2.2 Olfactory ensheathing cells**

periphery and brain [56].

**118**

*Combination of SCs transplantation with novel molecules/materials.*

of protecting neurons, due to its faculty to inhibit scar formation and promote regeneration of axons (see **Table 2**) [58]. They also have an important ability in neural regeneration that consists in their proliferation and migration from PNS and CNS.

This attribute explains that enhancement of axonal extension after injury is possible and it can help neural regeneration, as a result of the expression of molecules implicated in that process (**Table 2**) [2, 59].

OECs phenotypes are different depending on their location in CNS or PNS. It has been shown that they express different types of molecules implicated in neuroregeneration, such as adhesion molecules, neurotrophic factors, proteases, cytokines and inhibitory factors.


#### **Table 2.**

*OECs molecules implicated in neuroregeneration.*

Otherwise, many studies have proved that OECs are capable of replacing apoptotic or necrotic neural cells, secreting numerous neurotrophins, and contributing to remyelination. Although they do not do the last function in the individual olfactory sensory axons, they enwrap abundant bundles of them, to assemble the nerve fascicles [60]. Recent findings have shown that neuroblasts recently generated in the subventricular zone, migrate into the OB [56].

#### *2.2.1 Olfactory ensheating cells in response to injury*

Studies showed that OECs have a significant therapeutic importance because they [47] interact with astrocytes from the CNS and establish connections with the second neurons. They have the aptitude to guide transected axons of the corticospinal tract throughout the focus of injury that causes the restoration of paw movements, supraspinal control of breathing and improvements in climbing after transplantation into high cervical SC injuries [47, 60].

It is well known that the SC enclose the long motor tracts descending from the brain and the long sensory tracts ascending to the brain. Therefore, it is essential to reconstruct them, and if it is not possible, it is necessary to at least establish a new circuitry with the ability to provide access to the information which was cut off by the injury [61].

#### *2.2.2 Olfactory ensheating cells transplantation in spinal cord injury*

Studies showed that OECs have a significant therapeutic importance because they interact with astrocytes from the CNS and establish connections with the second neurons. The implantation of these cells into the injured SC can intensify neurite growths into the distal part, promoting functional recovery. They have the aptitude to guide transected axons of the corticospinal tract throughout the focus of injury which causes the restoration of paw movements, supraspinal control of breathing, bladder and improvements in climbing after transplantation into high cervical SC injuries [55, 60, 62, 63]. Likewise, OECs transplanted from rats, dogs, pigs and humans into the lesion site in the SC of the rat, promote remyelination of injured axons and restore impulse conduction [48].

In normal conditions, OECs do not form myelin, but when are transplanted into the demyelinated SC, they have the capacity to form a peripheral pattern of myelin reminiscent of SC's myelin [40] There is also evidence that they reduce proteoglycans expression in reactive astrocytes after the injury [63]. Otherwise, microenvironment and culture conditions have an important influence on OECs behaviors in vitro and in vivo [41].

It has been demonstrated that OECs transplants can reduce posttraumatic cavity size, increase the sprouting of neurofilaments and serotonin axons, improve

**121**

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury*

expression, which provide ICs environment for SCI repair [65].

functionality and have neuroprotective effects [42, 64]. Due to these facts, several studies have ranked these cells as the second most commonly used cell type after SCI. Recent studies have investigated the effect of co-transplantation of OECs and SCs at the injured site 7 days after contusion, demonstrating they significantly reduce the number of astrocytes, microglia/macrophage infiltration, and expression of chemokines (CCL2 and CCL3) at the injured site. These results suggest that OECs and SC's co-transplantation can promote the change of the macrophage phenotype from M1 secreting IFN-γ, to M2 secreting IL-4. The induction to M2 reduces ICs infiltration in the damaged site, regulates inflammatory factors and chemokine

The Choroid Plexus (CP) has a relatively simple structure. They consist of single layer of cuboidal to low cylindrical epithelial cells that reside on a basement membrane [43]. The main function is to form the cerebrospinal fluid (CSF). Approximately two thirds of this CSF is produced and secreted by the CP, the remainder produced by other areas such as the ependymal cells (ECs) of the ventricular surface and those cells lining the subarachnoid space. This fluid circulates in the ventricular system, subarachnoid spaces and spinal canal [44]. The CP, is not only implicate in CSF production also is a physical barrier to impede entrance of toxic metabolites to the brain [45]. Besides maintaining CNS homeostasis, CP and CSF have proven to be present in repairing processes after disease or damage [44]. The CP is located in the ventricular system of the brain. The ventricles consists

of epithelial tissue which is highly vascularized by fenestrated blood vessels [46, 66]. Within the lateral ventricles, it propels from the choroidal fissure and extends from the interventricular foramen to the end of the temporal horn. It projects into the third and fourth ventricles from the ventricular roof. Grossly, the CP is lobulated with a single continuous layer of cells derived from the ependymal lining of the ventricles. Despite it, these cells possess epithelial cell characteristics and are

CPECs are the prolongation of ECs of the ventricular wall, and the underlying connective tissue corresponds to the pia mater covering the brain surface. CPECs and ECs are of ectodermal origin and develop from the neuroepithelium in the roof plate [49]. However, unlike ECs, CPECs are directly attached via basal laminae to the connective tissue, a feature characteristic of general epithelial cells pertain to a small group of polarized cells, where the Na-K-ATPase is expressed in the luminal membrane [50]. Ultrastructurally, the CPECs contain numerous mitochondria needed to maintain their metabolic work capability for both secretory activities and maintaining ionic gradients across blood-CSF barriers [54]. Underlying the epithelial cells and basal lamina is a dense vascular bed that provides a blood flow four to seven times greater than the rest of the brain [54]. Elsewhere, the cells have tight junctions closest to the luminal membrane to separate the ventricle lumen from the lateral intercellular and basal spaces. Adherence junctions are situated below the tight junctions, and desmosomes appear further below the adherence junctions [67]. The luminal surface is characterized by microvilli, both primary cilia and motile cilia [43]. The capillaries are large with thin fenestrated endothelial walls and bridging diaphragms overlying the fenestrations. An extensive array of adrenergic, cholinergic, peptidergic and serotoninergic nerve fibers innervate the blood vessels and the epithelium [67]. In addition, CP secrete many trophic factors such as Hepatocyte Growth Factor (HGF), Basic fibroblast growth factor (bFGF), insulinlike growth factor-II (IGF-II), NGF, and Transforming growth factor (TGF) [68].

often referred to as CP epithelial cells (CPECs) [66].

*DOI: http://dx.doi.org/10.5772/intechopen.84645*

**2.3 Choroid plexus epithelial cells**

#### *Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.84645*

functionality and have neuroprotective effects [42, 64]. Due to these facts, several studies have ranked these cells as the second most commonly used cell type after SCI.

Recent studies have investigated the effect of co-transplantation of OECs and SCs at the injured site 7 days after contusion, demonstrating they significantly reduce the number of astrocytes, microglia/macrophage infiltration, and expression of chemokines (CCL2 and CCL3) at the injured site. These results suggest that OECs and SC's co-transplantation can promote the change of the macrophage phenotype from M1 secreting IFN-γ, to M2 secreting IL-4. The induction to M2 reduces ICs infiltration in the damaged site, regulates inflammatory factors and chemokine expression, which provide ICs environment for SCI repair [65].

#### **2.3 Choroid plexus epithelial cells**

*Spinal Cord Injury Therapy*

receptors

**Table 2.**

Neurotrophic (diffusible) factors/

*OECs molecules implicated in neuroregeneration.*

Otherwise, many studies have proved that OECs are capable of replacing apoptotic or necrotic neural cells, secreting numerous neurotrophins, and contributing to remyelination. Although they do not do the last function in the individual olfactory sensory axons, they enwrap abundant bundles of them, to assemble the nerve fascicles [60]. Recent findings have shown that neuroblasts recently generated in

Adhesion molecules L1, E-NCAM, Laminin, Fibronectin, Type-V collagen

ErbB

Cytokines IL-6/IL-6R, CX3CL1/Fractalkine, TGF-β3

Proteases (digest CSPG and PNN) MMP2, MMP9, Serpine-1

Inhibitory factors/receptors Nogo/NgR, Sema3A, EphrinA

NGF/p75, BDNF/TrkB, GDNF/GFRα-1, NTN/GFRα-2, NRG-1/

Studies showed that OECs have a significant therapeutic importance because they [47] interact with astrocytes from the CNS and establish connections with the second neurons. They have the aptitude to guide transected axons of the corticospinal tract throughout the focus of injury that causes the restoration of paw movements, supraspinal control of breathing and improvements in climbing after

It is well known that the SC enclose the long motor tracts descending from the brain and the long sensory tracts ascending to the brain. Therefore, it is essential to reconstruct them, and if it is not possible, it is necessary to at least establish a new circuitry with the ability to provide access to the information which was cut off by

Studies showed that OECs have a significant therapeutic importance because they interact with astrocytes from the CNS and establish connections with the second neurons. The implantation of these cells into the injured SC can intensify neurite growths into the distal part, promoting functional recovery. They have the aptitude to guide transected axons of the corticospinal tract throughout the focus of injury which causes the restoration of paw movements, supraspinal control of breathing, bladder and improvements in climbing after transplantation into high cervical SC injuries [55, 60, 62, 63]. Likewise, OECs transplanted from rats, dogs, pigs and humans into the lesion site in the SC of the rat, promote remyelination of

In normal conditions, OECs do not form myelin, but when are transplanted into the demyelinated SC, they have the capacity to form a peripheral pattern of myelin reminiscent of SC's myelin [40] There is also evidence that they reduce proteoglycans expression in reactive astrocytes after the injury [63]. Otherwise, microenvironment and culture conditions have an important influence on OECs behaviors

It has been demonstrated that OECs transplants can reduce posttraumatic cavity size, increase the sprouting of neurofilaments and serotonin axons, improve

the subventricular zone, migrate into the OB [56].

*2.2.1 Olfactory ensheating cells in response to injury*

transplantation into high cervical SC injuries [47, 60].

injured axons and restore impulse conduction [48].

*2.2.2 Olfactory ensheating cells transplantation in spinal cord injury*

**120**

in vitro and in vivo [41].

the injury [61].

The Choroid Plexus (CP) has a relatively simple structure. They consist of single layer of cuboidal to low cylindrical epithelial cells that reside on a basement membrane [43]. The main function is to form the cerebrospinal fluid (CSF). Approximately two thirds of this CSF is produced and secreted by the CP, the remainder produced by other areas such as the ependymal cells (ECs) of the ventricular surface and those cells lining the subarachnoid space. This fluid circulates in the ventricular system, subarachnoid spaces and spinal canal [44]. The CP, is not only implicate in CSF production also is a physical barrier to impede entrance of toxic metabolites to the brain [45]. Besides maintaining CNS homeostasis, CP and CSF have proven to be present in repairing processes after disease or damage [44].

The CP is located in the ventricular system of the brain. The ventricles consists of epithelial tissue which is highly vascularized by fenestrated blood vessels [46, 66]. Within the lateral ventricles, it propels from the choroidal fissure and extends from the interventricular foramen to the end of the temporal horn. It projects into the third and fourth ventricles from the ventricular roof. Grossly, the CP is lobulated with a single continuous layer of cells derived from the ependymal lining of the ventricles. Despite it, these cells possess epithelial cell characteristics and are often referred to as CP epithelial cells (CPECs) [66].

CPECs are the prolongation of ECs of the ventricular wall, and the underlying connective tissue corresponds to the pia mater covering the brain surface. CPECs and ECs are of ectodermal origin and develop from the neuroepithelium in the roof plate [49]. However, unlike ECs, CPECs are directly attached via basal laminae to the connective tissue, a feature characteristic of general epithelial cells pertain to a small group of polarized cells, where the Na-K-ATPase is expressed in the luminal membrane [50]. Ultrastructurally, the CPECs contain numerous mitochondria needed to maintain their metabolic work capability for both secretory activities and maintaining ionic gradients across blood-CSF barriers [54]. Underlying the epithelial cells and basal lamina is a dense vascular bed that provides a blood flow four to seven times greater than the rest of the brain [54]. Elsewhere, the cells have tight junctions closest to the luminal membrane to separate the ventricle lumen from the lateral intercellular and basal spaces. Adherence junctions are situated below the tight junctions, and desmosomes appear further below the adherence junctions [67]. The luminal surface is characterized by microvilli, both primary cilia and motile cilia [43]. The capillaries are large with thin fenestrated endothelial walls and bridging diaphragms overlying the fenestrations. An extensive array of adrenergic, cholinergic, peptidergic and serotoninergic nerve fibers innervate the blood vessels and the epithelium [67]. In addition, CP secrete many trophic factors such as Hepatocyte Growth Factor (HGF), Basic fibroblast growth factor (bFGF), insulinlike growth factor-II (IGF-II), NGF, and Transforming growth factor (TGF) [68].

#### *Spinal Cord Injury Therapy*

CP recently have been recognized as an important immunological compartment in maintaining and restoring brain homeostasis. It has been reported that the CP is the primary gate for trafficking ICs from the vascular system to the CSF in CNS impairment [69]. In the healthy brain, T lymphocytes are mainly found at the CSF or at the "borders" of the CNS: the CP at the brain's ventricles, and the meningeal membranes that cover the brain [69].

#### *2.3.1 Choroid plexus epithelial cells in response to injury*

The evidence that the CP can instantly respond to signals coming from either the CNS itself or circulating immunity, suggests the possibility of controlling brain plasticity by affecting CP function [69], and identifies the cultured cells like CPECs as a novel target for neuroinflammatory conditions may involve a common underlying mechanism of CP immunomodulation.

CSF recirculation within the CNS happens through numerous various pathways. Recent revelations about a previously unappreciated meningeal lymphatic system of the CNS [51, 52]. Although ICs (excluding microglia) have no access to the brain parenchyma under homeostatic conditions, the meninges around the brain are populated by a lot of immune-cell types, which not only provide immune surveillance but also affect brain function [53].

T lymphocytes and their cytokines not only do harm but may also display homeostasis-restoring functions in the CNS [70]. ICs are also found within the CP epithelium, and during inflammatory events their numbers increase [71, 72], giving rise to the hypothesis that the CP is one of the points of immune-cell entry into the CSF [73].

#### *2.3.2 Choroid plexus epithelial cells transplantation in spinal cord injury*

When was examined the role of the CPCEs on inflammation after acute SCI: IL-1β, TNF-α, and hsp70 proved that the CPCEs may serve as an important source of these inflammatory mediators after SCI. There was also an inverse correlation between IL-1β and hsp70 staining and duration of clinical signs in acute SCI, suggesting that the expression increasing of these proteins by the CPECs could be of particular importance in the immediate-early inflammatory response after acute SCI [52].

Certain studies with CPECs showed that they are capable of promoting neurite extension as well as neuronal survival in vitro: in coculture with CPECs, neurons derived from the dorsal root ganglia or hippocampus presented extensions of long numerous neurites with elaborated branches on the surface of CPECs [74, 75].

Researcher indicating that CPCEs can promote nerve regeneration when grafted into SC lesions, the outcomes indicate by electron microscopy and immunofluorescence that CPECs labelling with green fluorescent protein (GFP) before transplantation closely interacted with growing axons, serving to support the massive growth of regenerating axons. Also, in this study Horseradish peroxidase (HRP) injection at the sciatic nerve showed that many HRP-labeled regenerating fibers from the fasciculus gracilis (FG) elongated into the graft 7 days after grafting. Furthermore, these regenerating axons from the FC were preserved for at least 10 months, with some axons elongating rostrally into the dorsal funiculus [76]. Recently, a study on CPECs transplantation, in which cultured CPECs were directly injected into the SC lesion, engrafted CPECs were located in the astrocyte devoid areas of the SCI; these data suggest that in rat, during the process of cavitation, reactive astrocytes may be reducted. In adittion, GAP-43-positive axons were found at the border of the lesion 2 days after transplantation [50] . Other study demonstrated that transplantation of

**123**

CD8+

[87]. CD4+

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury*

astrocyte-devoid area formed in the epicenter of the lesion [77].

CPECs and MSC promotes axonal regeneration and enhances locomotor improvements. Overall this evidence suggests that they do not survive long term after transplantation into the SC. These date propose that some neurotrophic factors are released from those transplants to accelerate axonal regeneration through the

Lymphocytes and dendritic cells (DCs) are ICs that are found in many different tissues within the body and work together achieved immunosurveillance and host defense against infection and injury. DCs are professional antigen presenting cells (APC) that capture, process antigens to initiate immune responses and express lymphocyte co-stimulatory molecules not only for activating lymphocytes, but, tolerizing T lymphocytes to antigens [78]. Indeed, lymphocytes are the mediators of the adaptative response by focus release growth factors and cytokine to the target cell, but only an efficient host defense is achieved through coordination of complex signals between innate and adaptative ICs: interaction between APC such as DCs

Lymphocytes and DCs are derived from a hematopoietic stem cell in the bone marrow (BM); however, after certain cytokine secretion and transcription factors (TFs) expression, a common myeloid progenitor and common lymphoid progenitor are developed [80]. The first one differentiates into monocytes and DCs phenotype

and a small population of CD8α− DCs. DCs can be classified into myeloid or conventional DCs and plasmacytoid DCs. On the on hand, conventional can be divided into nonlymphoid tissue resident and lymphoid tissue residents and are well known for having a superior antigen processing, presentation machinery and ability to prime naive T lymphocytes responses; while plasmacytoid DCs express low levels of major histocompatibility complex class II (MHC-II) and costimulatory molecules [83]. In the case of lymphocytes, the bone marrow is where B lymphocytes maturation take place, while T lymphocytes development is generated in the thymus, by positive and negative selection to prevent potentially autoimmune reactions; only lymphocytes whose receptors interact weakly with self-antigens, and express a large repertoire of receptors capable of responding to a unlimited variety of non-self structures receive survival signals and are capable of migrating into peripheral lymphoid tissues as αβ naïve T helper (Th), thymic regulatory T (Treg), (CD4<sup>+</sup>

natural killer and γδ T lymphocytes, which play role in initial host response and

When traumatic insult is carried out, an immune response is triggered in order to contain the damaged tissue but avoiding a negative impact in the host. That is why a cellular response most be properly balance by regulatory T lymphocytes [86].

 T lymphocytes can differentiate principally in to regulatory and cytotoxic subsets, like the one that takes out Tc1 through the IL-12 influence, Tc2 differentiation from IL-4 and IL-6 plus TGFB can develop Tc17 with low cytotoxic activity

ing to their cytokine pattern TFs, except for Th1 and Th2 subsets discovered by Mosmann and Coffman in the 1980s; who found that clonal population from Th1

phocytes have diversified into a great number: Th9, Th17, T follicular helper (Thf)

principally secret IFNy and IL-4 in the Th2 subset [88]. Since that, CD4+

T lymphocytes can differentiate into many classified subsets accord-

) [81, 82], while the second one give rise to different lymphocytes subsets,

) T lymphocytes [84]. Also, a distinct lineage of T lymphocytes:

),

T lym-

*DOI: http://dx.doi.org/10.5772/intechopen.84645*

**2.4 Lymphocytes and dendritic cells**

with antigen and T lymphocytes [79].

(CD8α<sup>+</sup>

cytotoxic (CD8<sup>+</sup>

exhibit limited plasticity [79, 85].

*2.4.1 T lymphocytes in response to injury*

CPECs and MSC promotes axonal regeneration and enhances locomotor improvements. Overall this evidence suggests that they do not survive long term after transplantation into the SC. These date propose that some neurotrophic factors are released from those transplants to accelerate axonal regeneration through the astrocyte-devoid area formed in the epicenter of the lesion [77].

#### **2.4 Lymphocytes and dendritic cells**

*Spinal Cord Injury Therapy*

membranes that cover the brain [69].

ing mechanism of CP immunomodulation.

lance but also affect brain function [53].

CSF [73].

SCI [52].

*2.3.1 Choroid plexus epithelial cells in response to injury*

CP recently have been recognized as an important immunological compartment in maintaining and restoring brain homeostasis. It has been reported that the CP is the primary gate for trafficking ICs from the vascular system to the CSF in CNS impairment [69]. In the healthy brain, T lymphocytes are mainly found at the CSF or at the "borders" of the CNS: the CP at the brain's ventricles, and the meningeal

The evidence that the CP can instantly respond to signals coming from either the CNS itself or circulating immunity, suggests the possibility of controlling brain plasticity by affecting CP function [69], and identifies the cultured cells like CPECs as a novel target for neuroinflammatory conditions may involve a common underly-

CSF recirculation within the CNS happens through numerous various pathways. Recent revelations about a previously unappreciated meningeal lymphatic system of the CNS [51, 52]. Although ICs (excluding microglia) have no access to the brain parenchyma under homeostatic conditions, the meninges around the brain are populated by a lot of immune-cell types, which not only provide immune surveil-

T lymphocytes and their cytokines not only do harm but may also display homeostasis-restoring functions in the CNS [70]. ICs are also found within the CP epithelium, and during inflammatory events their numbers increase [71, 72], giving rise to the hypothesis that the CP is one of the points of immune-cell entry into the

When was examined the role of the CPCEs on inflammation after acute SCI: IL-1β, TNF-α, and hsp70 proved that the CPCEs may serve as an important source of these inflammatory mediators after SCI. There was also an inverse correlation between IL-1β and hsp70 staining and duration of clinical signs in acute SCI, suggesting that the expression increasing of these proteins by the CPECs could be of particular importance in the immediate-early inflammatory response after acute

Certain studies with CPECs showed that they are capable of promoting neurite extension as well as neuronal survival in vitro: in coculture with CPECs, neurons derived from the dorsal root ganglia or hippocampus presented extensions of long numerous neurites with elaborated branches on the surface of CPECs [74, 75].

Researcher indicating that CPCEs can promote nerve regeneration when grafted into SC lesions, the outcomes indicate by electron microscopy and immunofluorescence that CPECs labelling with green fluorescent protein (GFP) before transplantation closely interacted with growing axons, serving to support the massive growth of regenerating axons. Also, in this study Horseradish peroxidase (HRP) injection at the sciatic nerve showed that many HRP-labeled regenerating fibers from the fasciculus gracilis (FG) elongated into the graft 7 days after grafting. Furthermore, these regenerating axons from the FC were preserved for at least 10 months, with some axons elongating rostrally into the dorsal funiculus [76]. Recently, a study on CPECs transplantation, in which cultured CPECs were directly injected into the SC lesion, engrafted CPECs were located in the astrocyte devoid areas of the SCI; these data suggest that in rat, during the process of cavitation, reactive astrocytes may be reducted. In adittion, GAP-43-positive axons were found at the border of the lesion 2 days after transplantation [50] . Other study demonstrated that transplantation of

*2.3.2 Choroid plexus epithelial cells transplantation in spinal cord injury*

**122**

Lymphocytes and dendritic cells (DCs) are ICs that are found in many different tissues within the body and work together achieved immunosurveillance and host defense against infection and injury. DCs are professional antigen presenting cells (APC) that capture, process antigens to initiate immune responses and express lymphocyte co-stimulatory molecules not only for activating lymphocytes, but, tolerizing T lymphocytes to antigens [78]. Indeed, lymphocytes are the mediators of the adaptative response by focus release growth factors and cytokine to the target cell, but only an efficient host defense is achieved through coordination of complex signals between innate and adaptative ICs: interaction between APC such as DCs with antigen and T lymphocytes [79].

Lymphocytes and DCs are derived from a hematopoietic stem cell in the bone marrow (BM); however, after certain cytokine secretion and transcription factors (TFs) expression, a common myeloid progenitor and common lymphoid progenitor are developed [80]. The first one differentiates into monocytes and DCs phenotype (CD8α<sup>+</sup> ) [81, 82], while the second one give rise to different lymphocytes subsets, and a small population of CD8α− DCs. DCs can be classified into myeloid or conventional DCs and plasmacytoid DCs. On the on hand, conventional can be divided into nonlymphoid tissue resident and lymphoid tissue residents and are well known for having a superior antigen processing, presentation machinery and ability to prime naive T lymphocytes responses; while plasmacytoid DCs express low levels of major histocompatibility complex class II (MHC-II) and costimulatory molecules [83]. In the case of lymphocytes, the bone marrow is where B lymphocytes maturation take place, while T lymphocytes development is generated in the thymus, by positive and negative selection to prevent potentially autoimmune reactions; only lymphocytes whose receptors interact weakly with self-antigens, and express a large repertoire of receptors capable of responding to a unlimited variety of non-self structures receive survival signals and are capable of migrating into peripheral lymphoid tissues as αβ naïve T helper (Th), thymic regulatory T (Treg), (CD4<sup>+</sup> ), cytotoxic (CD8<sup>+</sup> ) T lymphocytes [84]. Also, a distinct lineage of T lymphocytes: natural killer and γδ T lymphocytes, which play role in initial host response and exhibit limited plasticity [79, 85].

#### *2.4.1 T lymphocytes in response to injury*

When traumatic insult is carried out, an immune response is triggered in order to contain the damaged tissue but avoiding a negative impact in the host. That is why a cellular response most be properly balance by regulatory T lymphocytes [86]. CD8+ T lymphocytes can differentiate principally in to regulatory and cytotoxic subsets, like the one that takes out Tc1 through the IL-12 influence, Tc2 differentiation from IL-4 and IL-6 plus TGFB can develop Tc17 with low cytotoxic activity [87]. CD4+ T lymphocytes can differentiate into many classified subsets according to their cytokine pattern TFs, except for Th1 and Th2 subsets discovered by Mosmann and Coffman in the 1980s; who found that clonal population from Th1 principally secret IFNy and IL-4 in the Th2 subset [88]. Since that, CD4+ T lymphocytes have diversified into a great number: Th9, Th17, T follicular helper (Thf)

#### *Spinal Cord Injury Therapy*

lymphocytes, induced regulatory T (iTreg) lymphocytes and Th22. Each CD4+ T lymphocytes subset can be defined by their capacity to sense specific cytokines and function to control pathogens, prevent immune pathologies and contain damage in trauma such as SCI [89].

#### *2.4.1.1 Lymphocytes as double-edged sword in spinal cord injury*

T lymphocytes the arrival of T lymphocytes is crucial for the development of an autoreactive response and parenchyma destruction, due to unique anatomophysiology of CNS through the release of proinflammatory cytokine entailing to more axon and cell bodies demyelination [90–92]. During acute phase, SC expresses high amounts of Th1 phenotype which is mainly regulated by IL-2, IL-12 and IFNy. Moreover, in subacute phases IL-4, IL-13, IL-10, IL-17 and IL-23 cytokines are found in plasma and spleen, indicating the presence of Th2, Treg and Th17 profiles as an inefficient compensatory mechanism [93, 94]. Accordingly to this, for the last 10 years experimental findings have shown that T lymphocytes are not just pathogenic but beneficial. Schwartz and coworkers suggested that T lymphocytes play an important role in plasticity and in injured CNS by a still debated mechanism termed "protective autoimmunity" which it established that under certain physiological circumstances, autoimmune T lymphocytes specific to myelin basic protein (MBP), mostly CD4<sup>+</sup> can exert positive effect by protecting injured neurons [95].

#### *2.4.1.2 Lymphocyte transferring after SCI*

Lymphocytes that play complex role in SCI after antigen priming; the epitopes from neural proteins, can be considered beneficial, and Tregs can secret growth factors, shown neurotrophic factor receptors and promote progenitor differentiation and remyelination in damaged CNS [36, 96], authors have proposed T lymphocytes against MBP transfer as a therapeutic approach after SCI [97]. However, the only limiting factors are that in order to have a positive response, a genetic background and permissive microenvironment must be needed; susceptible individuals or strains don't possess control mechanism such as appropriate antigen presentation, ability to evoke regulatory T lymphocytes and neuroendocrine effect on ICs regulation [4, 98, 99]. Yoles and cols proved that T lymphocytes evoke a neuroprotective response after injury when animals that received T lymphocytes against MBP from injured animals improves hindlimbs locomotor activity, recovery from optic nerve injury, and mostly evoke an anti-inflammatory cytokine profile in the SC, suggesting that a physiological and beneficial response is developed after trauma [100]. In addition, it has been corroborated in different studies; IL-4-deficient animals enhance neuronal survival and increase functional after trauma when CD4+ T lymphocytes from wild-type mice are transferred, but not from IL-4-deficient mice.

Inclusive, adoptive transfer of producing- IL-4, IL-10 and IL-3 CNS activated lymphocytes balance local inflammatory microenvironment by increasing protective cell populations like CD4<sup>+</sup> /Foxp3+ and CD68+ /Arg1+ cells and in situ, proving that an increment of Th2 subset is beneficial to CNS repair [97, 101, 102]. But, increasing Treg population most be taking in consideration, due to injection of Treg can increase suppressive functions and limit effector T lymphocytes, which is negative to injured tissue in an optic nerve injury model [103]. Also, other studies proposed that Th1 profile is necessary for neuroprotection in SCI model [104], but not Th2 neither Th17. Only mice with Th1-conditioned cell transfer show motor recovery and present axon arbors extending from the main corticoespinal tract into the gray matter rostral to the lesion site; however, T lymphocytes were never primed with an specific antigen, or isolated from immunized animals [105].

**125**

5 × 105

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury*

In addition, to boost the restorative response, and reduce the risk of developing an autoimmune disease neural modified peptide (NMP) has been tasted by active and passive immunization. A91 is a peptide derived from an encephalitogenic epitope, amino acids 87–99 of MBP, by replacing the lysine residue 91 with alanine, which has evidence neural tissue preservation and paralysis reduction in rat model [106–109]. Also, passive p472 (Nogo-A derived peptide) immunization, promotes a T lymphocytes neuroprotective response, and no significant IgM antibody response, revealing that the design of this therapeutic cell strategies does not depend on humoral response and reduce the possibility of promoting clinical changes in CNS, like myelin oligodendrocyte glycoprotein in resistant and non-

Other studies support the idea that T lymphocytes response can be controlled from APCs transplantation into the traumatized mice and in non-human primates. Perhaps, APC must be primed first with NMP or SC homogenate (SHC), because, even mature DCs can evoke antigen-specific T lymphocyte response, it is not efficient enough to promote motor recovery [112]. Studies support the idea that only pulsed DCs can influence the secretion of neurotrophic factors like BDNF and neurotrophin-3 (NT3) in culture supernatants and at the SC lesion site via CD4+

lymphocyte, motoneuron survival, NSCs proliferation and functional recovery [113–115]. Also, A91 has been used to pulse DCs, proving that motor recovery increase since the eleven days in comparison with control rats and an autoimmune response is not developed when Lewis strain is used but apparently a T lymphocyte response is involved, because when neonatally thymectomized rats are injected DCs treatment has no effect on recovery [116]. Furthermore, to promote regeneration, genetically modified fibroblasts to express BDNF have been tasted too. Cell therapy avoids secondary damage such as bleeding or infection that can be caused by growth

In the early 1990s, macrophages and microglia were thought to arise from the same myeloid progenitor cell [118], however multiple sophisticated methods have discarded the bone marrow origin hypothesis, and it is proposed that microglia derives from primitive myeloid precursors that arise in the yolk sac early during embryonic development, maintaining it apart from the rest myeloid lineage [119]. Moreover, it was proved that Tgfb is needed for its differentiation in comparison with other myeloid cells [120], implicating, ontogenically, that microglia are not resident macrophages but, the authentic sentinels of CNS. In healthy CNS and during early post-natal period, microglia possess a resting phenotype with round and ameboid characteristics [121] however, lately, microglia develops into a ramified phenotype, which is equipped to keep CNS homeostasis in the developing and adulthood brain by phagocytic properties, trophic factors release for developing neurons and guidance of new vasculature [122]. Also, to keep a steady state, microglia maintains interaction between neurons by fraktalkine (CXCL1) and CD200 receptors to control inflammatory response and cell death [123, 124].

In respect of macrophage participation in CNS, it seems to be from monocytes which migrate from different sites during embryogenesis and in the adulthood [125]. Nevertheless, mostly are present in normal CSF [118], which contains about

 ICs in blood ratio of 1:2000 for monocytes (23%) [119]. Then, macrophages reside in the perivascular space, meninges and within the stromal matrix of CP, but

T

*DOI: http://dx.doi.org/10.5772/intechopen.84645*

resistant strains [107, 110, 111].

*2.4.2.1 Macrophage vs. microglia*

*2.4.2 Pulsed dendritic cells in spinal cord injury*

factors or cytokine delivery in the site of injury [117].

#### *Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.84645*

In addition, to boost the restorative response, and reduce the risk of developing an autoimmune disease neural modified peptide (NMP) has been tasted by active and passive immunization. A91 is a peptide derived from an encephalitogenic epitope, amino acids 87–99 of MBP, by replacing the lysine residue 91 with alanine, which has evidence neural tissue preservation and paralysis reduction in rat model [106–109]. Also, passive p472 (Nogo-A derived peptide) immunization, promotes a T lymphocytes neuroprotective response, and no significant IgM antibody response, revealing that the design of this therapeutic cell strategies does not depend on humoral response and reduce the possibility of promoting clinical changes in CNS, like myelin oligodendrocyte glycoprotein in resistant and nonresistant strains [107, 110, 111].

#### *2.4.2 Pulsed dendritic cells in spinal cord injury*

*Spinal Cord Injury Therapy*

trauma such as SCI [89].

mostly CD4<sup>+</sup>

*2.4.1.2 Lymphocyte transferring after SCI*

tive cell populations like CD4<sup>+</sup>

lymphocytes, induced regulatory T (iTreg) lymphocytes and Th22. Each CD4+

*2.4.1.1 Lymphocytes as double-edged sword in spinal cord injury*

lymphocytes subset can be defined by their capacity to sense specific cytokines and function to control pathogens, prevent immune pathologies and contain damage in

T lymphocytes the arrival of T lymphocytes is crucial for the development of an autoreactive response and parenchyma destruction, due to unique anatomophysiology of CNS through the release of proinflammatory cytokine entailing to more axon and cell bodies demyelination [90–92]. During acute phase, SC expresses high amounts of Th1 phenotype which is mainly regulated by IL-2, IL-12 and IFNy. Moreover, in subacute phases IL-4, IL-13, IL-10, IL-17 and IL-23 cytokines are found in plasma and spleen, indicating the presence of Th2, Treg and Th17 profiles as an inefficient compensatory mechanism [93, 94]. Accordingly to this, for the last 10 years experimental findings have shown that T lymphocytes are not just pathogenic but beneficial. Schwartz and coworkers suggested that T lymphocytes play an important role in plasticity and in injured CNS by a still debated mechanism termed "protective autoimmunity" which it established that under certain physiological circumstances, autoimmune T lymphocytes specific to myelin basic protein (MBP),

can exert positive effect by protecting injured neurons [95].

Lymphocytes that play complex role in SCI after antigen priming; the epitopes from neural proteins, can be considered beneficial, and Tregs can secret growth factors, shown neurotrophic factor receptors and promote progenitor differentiation and remyelination in damaged CNS [36, 96], authors have proposed T lymphocytes against MBP transfer as a therapeutic approach after SCI [97]. However, the only limiting factors are that in order to have a positive response, a genetic background and permissive microenvironment must be needed; susceptible individuals or strains don't possess control mechanism such as appropriate antigen presentation, ability to evoke regulatory T lymphocytes and neuroendocrine effect on ICs regulation [4, 98, 99]. Yoles and cols proved that T lymphocytes evoke a neuroprotective response after injury when animals that received T lymphocytes against MBP from injured animals improves hindlimbs locomotor activity, recovery from optic nerve injury, and mostly evoke an anti-inflammatory cytokine profile in the SC, suggesting that a physiological and beneficial response is developed after trauma [100]. In addition, it has been corroborated in different studies; IL-4-deficient animals enhance neuronal survival and increase functional after trauma when CD4<sup>+</sup>

phocytes from wild-type mice are transferred, but not from IL-4-deficient mice. Inclusive, adoptive transfer of producing- IL-4, IL-10 and IL-3 CNS activated lymphocytes balance local inflammatory microenvironment by increasing protec-

that an increment of Th2 subset is beneficial to CNS repair [97, 101, 102]. But, increasing Treg population most be taking in consideration, due to injection of Treg can increase suppressive functions and limit effector T lymphocytes, which is negative to injured tissue in an optic nerve injury model [103]. Also, other studies proposed that Th1 profile is necessary for neuroprotection in SCI model [104], but not Th2 neither Th17. Only mice with Th1-conditioned cell transfer show motor recovery and present axon arbors extending from the main corticoespinal tract into the gray matter rostral to the lesion site; however, T lymphocytes were never primed

and CD68+

/Arg1+

/Foxp3+

with an specific antigen, or isolated from immunized animals [105].

T

T lym-

cells and in situ, proving

**124**

Other studies support the idea that T lymphocytes response can be controlled from APCs transplantation into the traumatized mice and in non-human primates. Perhaps, APC must be primed first with NMP or SC homogenate (SHC), because, even mature DCs can evoke antigen-specific T lymphocyte response, it is not efficient enough to promote motor recovery [112]. Studies support the idea that only pulsed DCs can influence the secretion of neurotrophic factors like BDNF and neurotrophin-3 (NT3) in culture supernatants and at the SC lesion site via CD4+ T lymphocyte, motoneuron survival, NSCs proliferation and functional recovery [113–115]. Also, A91 has been used to pulse DCs, proving that motor recovery increase since the eleven days in comparison with control rats and an autoimmune response is not developed when Lewis strain is used but apparently a T lymphocyte response is involved, because when neonatally thymectomized rats are injected DCs treatment has no effect on recovery [116]. Furthermore, to promote regeneration, genetically modified fibroblasts to express BDNF have been tasted too. Cell therapy avoids secondary damage such as bleeding or infection that can be caused by growth factors or cytokine delivery in the site of injury [117].

#### *2.4.2.1 Macrophage vs. microglia*

In the early 1990s, macrophages and microglia were thought to arise from the same myeloid progenitor cell [118], however multiple sophisticated methods have discarded the bone marrow origin hypothesis, and it is proposed that microglia derives from primitive myeloid precursors that arise in the yolk sac early during embryonic development, maintaining it apart from the rest myeloid lineage [119]. Moreover, it was proved that Tgfb is needed for its differentiation in comparison with other myeloid cells [120], implicating, ontogenically, that microglia are not resident macrophages but, the authentic sentinels of CNS. In healthy CNS and during early post-natal period, microglia possess a resting phenotype with round and ameboid characteristics [121] however, lately, microglia develops into a ramified phenotype, which is equipped to keep CNS homeostasis in the developing and adulthood brain by phagocytic properties, trophic factors release for developing neurons and guidance of new vasculature [122]. Also, to keep a steady state, microglia maintains interaction between neurons by fraktalkine (CXCL1) and CD200 receptors to control inflammatory response and cell death [123, 124].

In respect of macrophage participation in CNS, it seems to be from monocytes which migrate from different sites during embryogenesis and in the adulthood [125]. Nevertheless, mostly are present in normal CSF [118], which contains about 5 × 105 ICs in blood ratio of 1:2000 for monocytes (23%) [119]. Then, macrophages reside in the perivascular space, meninges and within the stromal matrix of CP, but

#### *Spinal Cord Injury Therapy*

not in neural parenchyma [126]. So, their principal function is the CNS immunosurveillance, that means, macrophages are one of the first APCs in interacting with antigens and T lymphocytes located in CFS, meninges and subarachnoid space, and thus, quickly phagocyte it or also optimize T lymphocytes reactivation and evoke a deleterious response such as autoimmune disease [127].

#### **2.5 Alternative macrophage and microglia**

Macrophages and microglia are both APCs that can be found in CNS under different functional phenotypes depending on the microenvironmental signals they received. In inflammation, microglia and macrophages express morphological changes, upregulate different cell markers and transcription factors. Microglia acquires a shape with shorter and thicker processes, increases CD45 expression and molecules for antigen presentation like MHCII, CD80 and CD86; also some miRNAs are related [128]. However, it is well known that activated macrophages and microglia can encompass two different functions. The first one is the classically activated M1 phenotype that is induced by IFNy or TNFa and secretes 1 l-12 and reactive oxygen intermediates. And the second one is an alternative subtype triggered by IL-4 and IL-13 cytokines and secretes TGFb and express arginase 1 [129]. To date, is not well stablished the appropriate cell markers to differentiate activated microglia from macrophages in CNS, but some populations have been proposed to differentiate the alternative phenotypes in monocytes: C3XCR1lo CCR2hi LY6Chi correspond to an inflammatory phenotype, while CX3CR1hi CCR2lo LY6Clo is found in the tissue remodeling phenotype [130, 131] and it has been corroborated in SCI studies; Shechter and cols. Proved that alternative M2 macrophages (Ly6cloCX3CR1hi) derived from monocytes traffic through CSF to provide an inflammatory response in SC [132].

Due to the important role that macrophages can play, several immunomodulatory therapies have been developed to control CNS response to pathological insults [123].

#### *2.5.1 Macrophage and microglia in response to injury*

Typically, damage stimulus triggers the activation of the microglia provoking the secretion of several cytokines like interferon gamma-induced protein 10, C-C motif chemokine ligand 1 (CCL1), C-C motif chemokine ligand 2 (CCL2) and C-C motif chemokine ligand 5 (CCL5) which recruit peripheral cells like macrophages. Microglia also participates in the adaptive immune response through the precise chemoattraction of T lymphocytes demonstrated in studies where the inhibition or stimulation of the resident microglia population resulted in abnormal recruitment [133].

These cells are considered essential screening damage monitoring constantly the microenvironment. Another important cell subgroup is the perivascular microglia which is replaced during 3 month period from bone marrow; its function is safeguarding the blood-brain barrier (BBB) through the recruitment of activated cell to BBB and parenchyma [134, 135].

#### *2.5.2 Macrophage and microglia trafficking in response to injury*

After a SCI take place an uncontrolled immune response that depends on the severity, level and mechanism of injury [136]. This cascade processes are characterized by pro-inflammatory and antiinflammatory alternatively activated cells [135]. The activation of phenotype M1 provokes neurotoxicity while type M2 promotes

**127**

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury*

Adoptive transfer of M2 in rats M2 phenotype reduces inflammation by increasing

injured SC.

in the study.

macrophages.

Activated cultured microglia Reduce the size of liquefaction necrosis area.

Recruitment of M2 macrophages CP provide a route of macrophages derived

Anti- IL6-receptor (MR16–1 Ab) Increased the area of spared myelin.

**Therapy Treatment outcome Reference**

GATA3+

The clinical trial can be implemented in patients, however many factors contribute to a funnel effect

Increase M2 activation. Decrease M1 macrophage gene expression and potentiate M2 macrophage gene expression. Also, potentiate microglia vs. monocyte derived M2 macrophage activation. AZM improved locomotor function and coordination of mice recovering.

Promoted functional recovery by promoting the formation of alternatively activated M2

the hind limb motor function recovery.

Activated antiinflammatory mechanisms. Promote

Decrease of IL-1 participates in both the classical and alternative activation of microglia.

monocyte (Ly6cloCX3CR1hi) to entry into the CNS to evoke an inflammatory response.

The study provides a preliminary evidence of safety and electrophysiological results. Also some patients present beneficial effects showing the

Th2 cells in the

[144]

[145]

[5]

[146]

[143]

[147]

[148]

[132]

the number of CD4+

efficacy of cell therapy.

axon growth and remyelination [137]. This lead the efforts to develop immuno-

The activation of the glia occurs the first 24 hours after trauma [138]; while the peripheral monocytes migrate into the injury within the following 2 or 3 days postinjury, then they differentiate into macrophages that become phenotypically and

The proinflammatory M1 macrophages vary along early stages releasing high levels of ROS to increase phagocytosis and cell recruitment removing foreign microbes and wound debris [140]; meanwhile M2 macrophages have some tissue repair properties through the release of immunosuppressive cytokines like IL-10 and C-C motif chemokines ligand 17, 18 and 22 to attract antiinflammatory leucocytes that increase the phagocytic receptors and upregulate growth factors [141]. There are three important chronological stages in the inflammatory response: the inflammatory, proliferative and remodeling phase and each one is characterized by certain cytokines and events. In the first one are present both M1 and M2a phenotypes, M1 secrete IL-1β, IL-12, TNF- α and IL-6 and M2a express high levels of IL-4, arginase-1 and Ym1 [142]. Comparative analysis of lesion development and intraspinal inflammation in four strains of mice following spinal contusion injury); during the second stage, keep going secreting proinflammatory cytokines but transition toward the expression of IL-10 and other antiinflammatory markers distinguished by the M2b macrophages followed by the M2c; in the third stage, the

modulatory therapies to modify phenotypic and functional properties.

morphologically indistinguishable [139].

*Immunomodulatory strategies for the microglia/macrophages response.*

*DOI: http://dx.doi.org/10.5772/intechopen.84645*

Incubated autologous macrophages in complete SCI: Phase I study

Autologous macrophages delivery in

Microglia/Macrophages activated

patients with SCI

Azithromycin (AZM)

with IL-1

**Table 3.**


*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.84645*

#### **Table 3.**

*Spinal Cord Injury Therapy*

not in neural parenchyma [126]. So, their principal function is the CNS immunosurveillance, that means, macrophages are one of the first APCs in interacting with antigens and T lymphocytes located in CFS, meninges and subarachnoid space, and thus, quickly phagocyte it or also optimize T lymphocytes reactivation and evoke a

Macrophages and microglia are both APCs that can be found in CNS under different functional phenotypes depending on the microenvironmental signals they received. In inflammation, microglia and macrophages express morphological changes, upregulate different cell markers and transcription factors. Microglia acquires a shape with shorter and thicker processes, increases CD45 expression and molecules for antigen presentation like MHCII, CD80 and CD86; also some miRNAs are related [128]. However, it is well known that activated macrophages and microglia can encompass two different functions. The first one is the classically activated M1 phenotype that is induced by IFNy or TNFa and secretes 1 l-12 and reactive oxygen intermediates. And the second one is an alternative subtype triggered by IL-4 and IL-13 cytokines and secretes TGFb and express arginase 1 [129]. To date, is not well stablished the appropriate cell markers to differentiate activated microglia from macrophages in CNS, but some populations have been proposed to differentiate the alternative phenotypes in monocytes: C3XCR1lo CCR2hi LY6Chi correspond to an inflammatory phenotype, while CX3CR1hi CCR2lo LY6Clo is found in the tissue remodeling phenotype [130, 131] and it has been corroborated in SCI studies; Shechter and cols. Proved that alternative M2 macrophages (Ly6cloCX3CR1hi) derived from monocytes traffic through CSF to provide an inflammatory response

Due to the important role that macrophages can play, several immunomodulatory therapies have been developed to control CNS response to pathological

Typically, damage stimulus triggers the activation of the microglia provoking the secretion of several cytokines like interferon gamma-induced protein 10, C-C motif chemokine ligand 1 (CCL1), C-C motif chemokine ligand 2 (CCL2) and C-C motif chemokine ligand 5 (CCL5) which recruit peripheral cells like macrophages. Microglia also participates in the adaptive immune response through the precise chemoattraction of T lymphocytes demonstrated in studies where the inhibition or stimulation of the resident microglia population resulted

These cells are considered essential screening damage monitoring constantly the microenvironment. Another important cell subgroup is the perivascular microglia which is replaced during 3 month period from bone marrow; its function is safeguarding the blood-brain barrier (BBB) through the recruitment of activated cell to

After a SCI take place an uncontrolled immune response that depends on the severity, level and mechanism of injury [136]. This cascade processes are characterized by pro-inflammatory and antiinflammatory alternatively activated cells [135]. The activation of phenotype M1 provokes neurotoxicity while type M2 promotes

deleterious response such as autoimmune disease [127].

**2.5 Alternative macrophage and microglia**

*2.5.1 Macrophage and microglia in response to injury*

*2.5.2 Macrophage and microglia trafficking in response to injury*

in abnormal recruitment [133].

BBB and parenchyma [134, 135].

**126**

in SC [132].

insults [123].

*Immunomodulatory strategies for the microglia/macrophages response.*

axon growth and remyelination [137]. This lead the efforts to develop immunomodulatory therapies to modify phenotypic and functional properties.

The activation of the glia occurs the first 24 hours after trauma [138]; while the peripheral monocytes migrate into the injury within the following 2 or 3 days postinjury, then they differentiate into macrophages that become phenotypically and morphologically indistinguishable [139].

The proinflammatory M1 macrophages vary along early stages releasing high levels of ROS to increase phagocytosis and cell recruitment removing foreign microbes and wound debris [140]; meanwhile M2 macrophages have some tissue repair properties through the release of immunosuppressive cytokines like IL-10 and C-C motif chemokines ligand 17, 18 and 22 to attract antiinflammatory leucocytes that increase the phagocytic receptors and upregulate growth factors [141].

There are three important chronological stages in the inflammatory response: the inflammatory, proliferative and remodeling phase and each one is characterized by certain cytokines and events. In the first one are present both M1 and M2a phenotypes, M1 secrete IL-1β, IL-12, TNF- α and IL-6 and M2a express high levels of IL-4, arginase-1 and Ym1 [142]. Comparative analysis of lesion development and intraspinal inflammation in four strains of mice following spinal contusion injury); during the second stage, keep going secreting proinflammatory cytokines but transition toward the expression of IL-10 and other antiinflammatory markers distinguished by the M2b macrophages followed by the M2c; in the third stage, the M2c release high concentrations of IL-10, IGF1 [138]. Macrophage activation and its role in repair and pathology after SCI. TGF-β and a mannose receptor (CD206) with the decrease of arginase-1 and IL-12. At the end, the macrophages are deactivated and the inflammation resolves, this process can last several months. In brief, this sequence will provoke the axon dieback (classical macrophages) and remyelination, axon regeneration and the reduction of the dieback [143].

#### *2.5.3 Macrophage and microglia in spinal cord injury*

The manipulating macrophages facilitate maturation events typical of normal healing, for this reason it has been studied several methods to activate alternative macrophages and another strategy is better to improve the normal healing response by blocking certain pro-inflammatory mechanisms (**Table 3**).

#### **3. Conclusions**

The beneficial effects of cultured cells transplantation or transference in SCI have been demonstrated by numerous investigators and they are one of the main hopes for developing an effective treatment for SCI. This may be due to their great potential to amplify and genetically manipulate them in vitro, as well as all the complicated functions in axonal regeneration they possess. Furthermore, the development of cell transplantation derived from precursors show a higher ability to survive, integrate well with host tissue and support brainstem axon growth into and beyond the graft. However, the optimal source needs further investigation.

Recently, several clinical studies suggest their safety and feasibility, meaning that the transplantation of cultured cells have a significant therapeutic potential in persons with SCI. Nowadays, they are currently at an early stage of clinical testing following preclinical development.

#### **Acknowledgements**

We gratefully acknowledge to Universidad Anáhuac México Norte for your support to this project.

#### **Author details**

Roxana Rodríguez-Barrera, Karla Soria-Zavala, Julián García-Sánchez, Lisset Karina Navarro-Torres, Estefanía de la Cruz Castillo and Elisa García-Vences\* Centro de Investigación en Ciencias de la Salud (CICSA), Universidad Anáhuac México Campus Norte, Mexico

\*Address all correspondence to: edna.garcia@anahuac.mx

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**129**

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury*

[8] Sahni V, Kessler JA. Stem cell therapies for spinal cord injury. Nature Reviews. Neurology. 2010;**6**(7):363-372

[9] Kanno H, Pearse DD, Ozawa H, Itoi E, Bunge MB. Schwann cell transplantation for spinal cord injury repair: Its significant therapeutic

potential and prospectus. Reviews in the Neurosciences. 2015;**26**(2):121-128

[10] Pearse DD, Pereira FC, Marcillo AE, Bates ML, Berrocal YA, Filbin MT, et al. cAMP and Schwann cells promote axonal growth and functional recovery after spinal cord injury. Nature

Medicine. 2004;**10**(6):610-616

[11] Takami T, Oudega M, Bates ML, Wood PM, Kleitman N, Bunge MB. Schwann cell but not olfactory ensheathing glia transplants improve hindlimb locomotor performance in the moderately contused adult rat thoracic spinal cord. The Journal of Neuroscience. 2002;**22**(15):6670-6681

[12] Nave KA. Myelination and support of axonal integrity by glia. Nature.

PJ. Mechanisms of axon ensheathment and myelin growth. Nature Reviews. Neuroscience. 2005;**6**(9):683-690

[15] Jessen KR, Mirsky R. The origin and development of glial cells in peripheral nerves. Nature Reviews. Neuroscience.

regulation of myelination by neuregulin 1. Current Opinion in Neurobiology.

[14] Glenn TD, Talbot WS. Signals regulating myelination in peripheral nerves and the Schwann cell response

to injury. Current Opinion in Neurobiology. 2013;**23**(6):1041-1048

[16] Nave KA, Salzer JL. Axonal

2005;**6**(9):671-682

2006;**16**(5):492-500

2010;**468**(7321):244-252

[13] Sherman DL, Brophy

*DOI: http://dx.doi.org/10.5772/intechopen.84645*

[1] Zhou Y, Wang Z, Li J, Li X, Xiao J. Fibroblast growth factors in the management of spinal cord injury. Journal of Cellular and Molecular Medicine. 2018;**22**(1):25-37

[2] Gomez RM, Sanchez MY, Portela-Lomba M, Ghotme K, Barreto GE, Sierra J, et al. Cell therapy for spinal cord injury with olfactory ensheathing glia cells (OECs). Glia.

[3] Tabakow P, Jarmundowicz W, Czapiga B, Fortuna W, Miedzybrodzki R, Czyz M, et al. Transplantation of autologous olfactory ensheathing cells in complete human spinal cord injury. Cell Transplantation. 2013;**22**(9):1591-1612

[4] Jones TB, Ankeny DP, Guan Z, McGaughy V, Fisher LC, Basso DM, et al. Passive or active immunization with myelin basic protein impairs neurological function and exacerbates neuropathology after spinal cord injury in rats. The Journal of Neuroscience.

2018;**66**(7):1267-1301

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2004;**24**(15):3752-3761

2010;**48**(11):798-807

2011;**32**(30):7454-7468

2011;**8**(4):668-676

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[5] Jones LA, Lammertse DP, Charlifue SB, Kirshblum SC, Apple DF, Ragnarsson KT, et al. A phase 2 autologous cellular therapy trial in patients with acute, complete spinal cord injury: Pragmatics, recruitment, and demographics. Spinal Cord.

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*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.84645*

#### **References**

*Spinal Cord Injury Therapy*

**128**

**Author details**

port to this project.

**Acknowledgements**

**3. Conclusions**

México Campus Norte, Mexico

following preclinical development.

provided the original work is properly cited.

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Lisset Karina Navarro-Torres, Estefanía de la Cruz Castillo and Elisa García-Vences\* Centro de Investigación en Ciencias de la Salud (CICSA), Universidad Anáhuac

We gratefully acknowledge to Universidad Anáhuac México Norte for your sup-

M2c release high concentrations of IL-10, IGF1 [138]. Macrophage activation and its role in repair and pathology after SCI. TGF-β and a mannose receptor (CD206) with the decrease of arginase-1 and IL-12. At the end, the macrophages are deactivated and the inflammation resolves, this process can last several months. In brief, this sequence will provoke the axon dieback (classical macrophages) and remyelination,

The manipulating macrophages facilitate maturation events typical of normal healing, for this reason it has been studied several methods to activate alternative macrophages and another strategy is better to improve the normal healing response

The beneficial effects of cultured cells transplantation or transference in SCI have been demonstrated by numerous investigators and they are one of the main hopes for developing an effective treatment for SCI. This may be due to their great potential to amplify and genetically manipulate them in vitro, as well as all the complicated functions in axonal regeneration they possess. Furthermore, the development of cell transplantation derived from precursors show a higher ability to survive, integrate well with host tissue and support brainstem axon growth into and beyond the graft. However, the optimal source needs further investigation. Recently, several clinical studies suggest their safety and feasibility, meaning that the transplantation of cultured cells have a significant therapeutic potential in persons with SCI. Nowadays, they are currently at an early stage of clinical testing

axon regeneration and the reduction of the dieback [143].

by blocking certain pro-inflammatory mechanisms (**Table 3**).

*2.5.3 Macrophage and microglia in spinal cord injury*

Roxana Rodríguez-Barrera, Karla Soria-Zavala, Julián García-Sánchez,

\*Address all correspondence to: edna.garcia@anahuac.mx

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[10] Pearse DD, Pereira FC, Marcillo AE, Bates ML, Berrocal YA, Filbin MT, et al. cAMP and Schwann cells promote axonal growth and functional recovery after spinal cord injury. Nature Medicine. 2004;**10**(6):610-616

[11] Takami T, Oudega M, Bates ML, Wood PM, Kleitman N, Bunge MB. Schwann cell but not olfactory ensheathing glia transplants improve hindlimb locomotor performance in the moderately contused adult rat thoracic spinal cord. The Journal of Neuroscience. 2002;**22**(15):6670-6681

[12] Nave KA. Myelination and support of axonal integrity by glia. Nature. 2010;**468**(7321):244-252

[13] Sherman DL, Brophy PJ. Mechanisms of axon ensheathment and myelin growth. Nature Reviews. Neuroscience. 2005;**6**(9):683-690

[14] Glenn TD, Talbot WS. Signals regulating myelination in peripheral nerves and the Schwann cell response to injury. Current Opinion in Neurobiology. 2013;**23**(6):1041-1048

[15] Jessen KR, Mirsky R. The origin and development of glial cells in peripheral nerves. Nature Reviews. Neuroscience. 2005;**6**(9):671-682

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modifies reactive astrogliosis allowing robust axonal regeneration through Schwann cell-seeded guidance channels after spinal cord injury. Experimental Neurology. 2011;**229**(2):238-250

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[38] Fouad K, Schnell L, Bunge MB, Schwab ME, Liebscher T, Pearse DD. Combining Schwann cell bridges and olfactory-ensheathing glia grafts with chondroitinase promotes locomotor recovery after complete transection of the spinal cord. The Journal of Neuroscience.

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Transplantation of olfactory

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.84645*

modifies reactive astrogliosis allowing robust axonal regeneration through Schwann cell-seeded guidance channels after spinal cord injury. Experimental Neurology. 2011;**229**(2):238-250

*Spinal Cord Injury Therapy*

Biology. 1997;**7**(7):R406-R410

[19] Brosius Lutz A, Barres

2014;**28**(1):7-17

[18] Jessen KR, Mirsky R. The repair Schwann cell and its function in regenerating nerves. The Journal of Physiology. 2016;**594**(13):3521-3531

BA. Contrasting the glial response to axon injury in the central and peripheral nervous systems. Developmental Cell.

[20] Dalamagkas K, Tsintou M, Seifalian

regenerative therapies for chronic spinal cord injury. International Journal of Molecular Sciences. 2018;**19**(6):1776

A, Seifalian AM. Translational

[21] Blesch A, Lu P, Tsukada S, Alto LT, Roet K, Coppola G, et al. Conditioning lesions before or after spinal cord injury recruit broad genetic mechanisms that sustain axonal regeneration: Superiority to camp-mediated effects. Experimental Neurology. 2012;**235**(1):162-173

[22] Barrette B, Hebert MA, Filali M, Lafortune K, Vallieres N, Gowing G, et al. Requirement of myeloid cells for axon regeneration. The Journal of Neuroscience. 2008;**28**(38):9363-9376

[23] Rotshenker S. Wallerian degeneration: The innate-immune response to traumatic nerve injury. Journal of Neuroinflammation.

[24] Jessen KR, Mirsky R, Arthur-Farraj P. The role of cell plasticity in tissue repair: Adaptive cellular reprogramming. Developmental Cell.

[25] Jessen KR, Mirsky R. Negative

Relevance for development, injury, and demyelinating disease. Glia.

regulation of myelination:

2008;**56**(14):1552-1565

2011;**8**:109

2015;**34**(6):613-620

[17] Waxman SG. Axon-glia interactions: Building a smart nerve fiber. Current

[26] Brushart TM, Aspalter M, Griffin JW, Redett R, Hameed H, Zhou C, et al. Schwann cell phenotype is regulated by axon modality and central-peripheral location, and persists in vitro. Experimental Neurology.

[27] Jessen KR, Mirsky R, Lloyd AC. Schwann cells: Development and role in nerve repair. Cold Spring Harbor Perspectives in Biology.

[28] Aguayo AJ, David S, Bray

GM. Influences of the glial environment on the elongation of axons after injury: Transplantation studies in adult rodents. The Journal of Experimental Biology.

[29] Kanno H, Pressman Y, Moody A, Berg R, Muir EM, Rogers JH, et al. Combination of engineered Schwann cell grafts to secrete neurotrophin and chondroitinase promotes axonal regeneration and locomotion after spinal cord injury. The Journal of Neuroscience. 2014;**34**(5):1838-1855

[30] Pearse DD, Sanchez AR, Pereira FC, Andrade CM, Puzis R, Pressman Y, et al. Transplantation of Schwann cells and/or olfactory ensheathing glia into the contused spinal cord: Survival, migration, axon association,

and functional recovery. Glia.

[31] Assinck P, Duncan GJ, Hilton BJ, Plemel JR, Tetzlaff W. Cell transplantation therapy for spinal cord injury. Nature Neuroscience.

2007;**55**(9):976-1000

2017;**20**(5):637-647

2015;**1619**:104-114

[32] Deng LX, Walker C, Xu

[33] Deng LX, Hu J, Liu N, Wang X, Smith GM, Wen X, et al. GDNF

XM. Schwann cell transplantation and descending propriospinal regeneration after spinal cord injury. Brain Research.

2013;**247**:272-281

2015;**7**(7):a020487

1981;**95**:231-240

**130**

[34] Kuo HS, Tsai MJ, Huang MC, Chiu CW, Tsai CY, Lee MJ, et al. Acid fibroblast growth factor and peripheral nerve grafts regulate Th2 cytokine expression, macrophage activation, polyamine synthesis, and neurotrophin expression in transected rat spinal cords. The Journal of Neuroscience. 2011;**31**(11):4137-4147

[35] Murray M, Fischer I. Transplantation and gene therapy: Combined approaches for repair of spinal cord injury. The Neuroscientist. 2001;**7**(1):28-41

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Matsumoto N, Taketomi M, Kimura K, Ide C. Choroid plexus ependymal cells enhance neurite outgrowth from dorsal root ganglion neurons in vitro. Journal of Neurocytology. 2000;**29**(10):707-717

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[80] Kondo M. Lymphoid and myeloid lineage commitment in multipotent

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HH. Transport across the choroid plexus epithelium. American Journal of Physiology. Cell Physiology. 2017;**312**(6):C673-C686

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[69] Baruch K, Schwartz M. CNSspecific T cells shape brain function via the choroid plexus. Brain, Behavior, and

[70] Ellwardt E, Walsh JT, Kipnis J, Zipp F. Understanding the role of T cells in CNS homeostasis. Trends in Immunology. 2016;**37**(2):154-165

[71] Giunti D, Borsellino G, Benelli R, Marchese M, Capello E, Valle MT, et al. Phenotypic and functional analysis of T cells homing into the CSF of subjects with inflammatory diseases of the CNS. Journal of Leukocyte Biology.

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*Spinal Cord Injury Therapy*

2016;**34**(3):347-366

2015;**212**(7):991-999

2018;**21**(10):1380-1391

2016;**353**(6301):766-771

1997;**116**(3):399-405

[55] Moore SA, Oglesbee

Experimental Brain Research.

[49] Dziegielewska KM, Ek J, Habgood MD, Saunders NR. Development of the choroid plexus. Microscopy Research and Technique. 2001;**52**(1):5-20

and meta-analysis. European Spine

[57] Tabakow P, Raisman G, Fortuna W, Czyz M, Huber J, Li D, et al.

Functional regeneration of supraspinal connections in a patient with transected spinal cord following transplantation of bulbar olfactory ensheathing cells with peripheral nerve bridging. Cell Transplantation. 2014;**23**(12):1631-1655

[58] Tang YY, Guo WX, Lu ZF, Cheng MH, Shen YX, Zhang YZ. Ginsenoside Rg1 promotes the migration of olfactory ensheathing cells via the PI3K/Akt pathway to repair rat spinal cord injury. Biological & Pharmaceutical Bulletin.

[59] Anna Z, Katarzyna JW, Joanna C, Barczewska M, Joanna W, Wojciech M. Therapeutic potential of olfactory ensheathing cells and mesenchymal stem cells in spinal cord injuries. Stem Cells International. 2017;**2017**:3978595

[60] Ekberg JA, St John JA. Olfactory

[61] Li Y, Li D, Raisman G. Interaction of olfactory ensheathing cells with astrocytes may be the key to repair of tract injuries in the spinal cord: The 'pathway hypothesis'. Journal of Neurocytology. 2005;**34**(3-5):343-351

[62] Woodhall E, West AK, Vickers JC, Chuah MI. Olfactory ensheathing cell phenotype following implantation in the lesioned spinal cord. Cellular and Molecular Life Sciences. 2003;**60**(10):2241-2253

[63] Wewetzer K, Verdu E, Angelov DN, Navarro X. Olfactory ensheathing glia and Schwann cells: Two of a kind? Cell and Tissue Research.

2002;**309**(3):337-345

ensheathing cells for spinal cord repair: Crucial differences between subpopulations of the glia. Neural Regeneration Research.

2015;**10**(9):1395-1396

2017;**40**(10):1630-1637

Journal. 2015;**24**(5):919-930

[50] Kanekiyo K, Nakano N, Noda T, Yamada Y, Suzuki Y, Ohta M, et al. Transplantation of choroid plexus epithelial cells into contusion-injured spinal cord of rats. Restorative Neurology and Neuroscience.

[51] Aspelund A, Antila S, Proulx ST, Karlsen TV, Karaman S, Detmar M, et al. A dural lymphatic vascular system that drains brain interstitial fluid and macromolecules. The Journal of Experimental Medicine.

[52] Louveau A, Herz J, Alme MN, Salvador AF, Dong MQ, Viar KE, et al. CNS lymphatic drainage and neuroinflammation are regulated by meningeal lymphatic vasculature. Nature Neuroscience.

[53] Kipnis J. Multifaceted interactions between adaptive immunity and the central nervous system. Science.

[54] Cornford EM, Varesi JB, Hyman S, Damian RT, Raleigh MJ. Mitochondrial content of choroid plexus epithelium.

MJ. Involvement of the choroid plexus in the inflammatory response after acute spinal cord injury in dogs: An immunohistochemical study. Veterinary Immunology and Immunopathology. 2012;**148**(3-4):

[56] Li L, Adnan H, Xu B, Wang J, Wang C, Li F, et al. Effects of transplantation of olfactory ensheathing cells in chronic spinal cord injury: A systematic review

**132**

348-352

[65] Zhang J, Chen H, Duan Z, Chen K, Liu Z, Zhang L, et al. The effects of co-transplantation of olfactory ensheathing cells and Schwann cells on local inflammation environment in the contused spinal cord of rats. Molecular Neurobiology. 2017;**54**(2):943-953

[66] Emerich DF, Skinner SJ, Borlongan CV, Vasconcellos AV, Thanos CG. The choroid plexus in the rise, fall and repair of the brain. BioEssays. 2005;**27**(3):262-274

[67] Praetorius J, Damkier HH. Transport across the choroid plexus epithelium. American Journal of Physiology. Cell Physiology. 2017;**312**(6):C673-C686

[68] Chodobski A, Szmydynger-Chodobska J. Choroid plexus: Target for polypeptides and site of their synthesis. Microscopy Research and Technique. 2001;**52**(1):65-82

[69] Baruch K, Schwartz M. CNSspecific T cells shape brain function via the choroid plexus. Brain, Behavior, and Immunity. 2013;**34**:11-16

[70] Ellwardt E, Walsh JT, Kipnis J, Zipp F. Understanding the role of T cells in CNS homeostasis. Trends in Immunology. 2016;**37**(2):154-165

[71] Giunti D, Borsellino G, Benelli R, Marchese M, Capello E, Valle MT, et al. Phenotypic and functional analysis of T cells homing into the CSF of subjects with inflammatory diseases of the CNS. Journal of Leukocyte Biology. 2003;**73**(5):584-590

[72] Young KG, Maclean S, Dudani R, Krishnan L, Sad S. CD8+ T cells primed in the periphery provide time-bound immune-surveillance to the central nervous system. Journal of Immunology. 2011;**187**(3):1192-1200

[73] Marin IA, Kipnis J. Central nervous system: (Immunological) ivory tower or not? Neuropsychopharmacology. 2017;**42**(1):28-35

[74] Kimura K, Matsumoto N, Kitada M, Mizoguchi A, Ide C. Neurite outgrowth from hippocampal neurons is promoted by choroid plexus ependymal cells in vitro. Journal of Neurocytology. 2004;**33**(4):465-476

[75] Chakrabortty S, Kitada M, Matsumoto N, Taketomi M, Kimura K, Ide C. Choroid plexus ependymal cells enhance neurite outgrowth from dorsal root ganglion neurons in vitro. Journal of Neurocytology. 2000;**29**(10):707-717

[76] Ide C, Kitada M, Chakrabortty S, Taketomi M, Matsumoto N, Kikukawa S, et al. Grafting of choroid plexus ependymal cells promotes the growth of regenerating axons in the dorsal funiculus of rat spinal cord: A preliminary report. Experimental Neurology. 2001;**167**(2):242-251

[77] Ide C, Nakano N, Kanekiyo K. Cell transplantation for the treatment of spinal cord injury - bone marrow stromal cells and choroid plexus epithelial cells. Neural Regeneration Research. 2016;**11**(9):1385-1388

[78] Banchereau J, Steinman RM. Dendritic cells and the control of immunity. Nature. 1998;**392**(6673):245-252

[79] Charles A Janeway J, Travers P, Walport M, Shlomchik MJ. General properties of armed effector T cells. 2001;**8**:343-400

[80] Kondo M. Lymphoid and myeloid lineage commitment in multipotent

hematopoietic progenitors. Immunological Reviews. 2010;**238**(1):37-46

[81] Onai N, Obata-Onai A, Schmid MA, Manz MG. Flt3 in regulation of type I interferon-producing cell and dendritic cell development. Annals of the New York Academy of Sciences. 2007;**1106**:253-261

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[86] Zhou L, Chong MM, Littman DR. Plasticity of CD4<sup>+</sup> T cell lineage differentiation. Immunity. 2009;**30**(5):646-655

[87] Huber M, Heink S, Grothe H, Guralnik A, Reinhard K, Elflein K, et al. A Th17-like developmental process leads to CD8(+) Tc17 cells with reduced cytotoxic activity. European Journal of Immunology. 2009;**39**(7):1716-1725

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[94] Mukhamedshina YO, Akhmetzyanova ER, Martynova EV, Khaiboullina SF, Galieva LR, Rizvanov AA. Systemic and local cytokine profile following spinal cord injury in rats: A multiplex analysis. Frontiers in Neurology. 2017;**8**:581

[95] Moalem G, Leibowitz-Amit R, Yoles E, Mor F, Cohen IR, Schwartz M. Autoimmune T cells protect neurons from secondary degeneration after central nervous system axotomy. Nature Medicine. 1999;**5**(1):49-55

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2002;**130**(1):78-85

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[98] Kipnis J, Yoles E, Schori H, Hauben E, Shaked I, Schwartz M. Neuronal survival after CNS insult is determined by a genetically encoded autoimmune response. The Journal of Neuroscience.

[99] Mestre H, Ramirez M, Garcia E, Martiñón S, Cruz Y, Campos MG, et al. Lewis, Fischer 344, and Sprague-Dawley rats display differences in lipid peroxidation, motor recovery, and rubrospinal tract preservation after spinal cord injury. Frontiers in

2001;**108**:591-599

2001;**21**(13):4564-4571

Neurology. 2015;**6**:108

2001;**21**(11):3740-3748

MHCII-independent CD4+

2015;**125**(6):2547

2016;**277**:190-201

[100] Yoles E, Hauben E, Palgi O, Agranov E, Gothilf A, Cohen A, et al. Protective autoimmunity is a physiological response to CNS trauma. The Journal of Neuroscience.

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protect injured CNS neurons via IL-4.

[102] Hu JG, Shi LL, Chen YJ, Xie XM, Zhang N, Zhu AY, et al. Differential effects of myelin basic protein-activated Th1 and Th2 cells on the local immune microenvironment of injured spinal cord. Experimental Neurology.

T cells

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.84645*

factor and nerve growth factor receptor tyrosine kinase Trk in activated CD4 positive T-cell clones. Proceedings of the National Academy of Sciences of the United States of America. 1993;**90**(23):10984-10988

*Spinal Cord Injury Therapy*

2007;**1106**:253-261

2001;**97**(11):3333-3341

hematopoietic progenitors. Immunological Reviews. 2010;**238**(1):37-46

[89] DuPage M, Bluestone

[90] Popovich PG, Wei P, Stokes BT. Cellular inflammatory response after spinal cord injury in Sprague-Dawley and Lewis rats. The

Journal of Comparative Neurology.

[91] Trivedi A, Olivas AD, Noble-Haeusslein LJ. Inflammation and spinal cord injury: Infiltrating leukocytes as determinants of injury and repair processes. Clinical Neuroscience Research. 2006;**6**(5):283-292

[92] Beck KD, Nguyen HX, Galvan MD, Salazar DL, Woodruff TM, Anderson AJ. Quantitative analysis of cellular inflammation after traumatic spinal cord injury: Evidence for a multiphasic inflammatory response in the acute to chronic environment. Brain.

[93] Zong S, Zeng G, Fang Y, Peng J, Tao Y, Li K, et al. The role of IL-17 promotes spinal cord neuroinflammation via activation of the transcription factor STAT3 after spinal cord injury in the rat. Mediators of Inflammation.

2016;**16**(3):149-163

1997;**377**(3):443-464

2010;**133**:433-447

2014;**2014**:2014:786947

Neurology. 2017;**8**:581

Medicine. 1999;**5**(1):49-55

[94] Mukhamedshina YO,

Akhmetzyanova ER, Martynova EV, Khaiboullina SF, Galieva LR, Rizvanov AA. Systemic and local cytokine profile following spinal cord injury in rats: A multiplex analysis. Frontiers in

[95] Moalem G, Leibowitz-Amit R, Yoles E, Mor F, Cohen IR, Schwartz M. Autoimmune T cells protect neurons from secondary degeneration after central nervous system axotomy. Nature

[96] Ehrhard PB, Erb P, Graumann U, Otten U. Expression of nerve growth

JA. Harnessing the plasticity of CD4(+) T cells to treat immune-mediated disease. Nature Reviews. Immunology.

[81] Onai N, Obata-Onai A, Schmid MA, Manz MG. Flt3 in regulation of type I interferon-producing cell and dendritic cell development. Annals of the New York Academy of Sciences.

[82] Manz MG, Traver D, Miyamoto T, \Weissman IL, Akashi K. Dendritic cell potentials of early lymphoid and myeloid progenitors. Blood.

[83] Merad M, Sathe P, Helft J, Miller J, Mortha A. The dendritic cell lineage: Ontogeny and function of dendritic cells and their subsets in the steady state and the inflamed setting. Annual Review of

Immunology. 2013;**31**:563-604

[84] Charles A Janeway J, Travers P, Walport M, Shlomchik MJ. The development and survival of lymphocytes. 2001;**7**:258:342

[85] Jensen KDC, Su X, Shin S, Li L, Youssef S, Yamasaki S, et al. Lymphoid γδ T cells that develop in the absence of ligand produce IL-17 rapidly. Immunity.

[86] Zhou L, Chong MM, Littman

lineage differentiation. Immunity.

[87] Huber M, Heink S, Grothe H, Guralnik A, Reinhard K, Elflein K, et al. A Th17-like developmental process leads to CD8(+) Tc17 cells with reduced cytotoxic activity. European Journal of Immunology.

[88] Mosmann TR, Coffman RL. TH1 and TH2 cells: Different patterns of lymphokine secretion lead to different functional properties. Annual Review of

Immunology. 1989;**7**:145-173

T cell

2008;**29**(1):90-100

DR. Plasticity of CD4<sup>+</sup>

2009;**30**(5):646-655

2009;**39**(7):1716-1725

**134**

[97] Hauben E, Agranov E, Gothilf A, Nevo U, Cohen A, Smirnov I, et al. Posttraumatic therapeutic vaccination with modified myelin self-antigen prevents complete paralysis while avoiding autoimmune disease. The Journal of Clinical Investigation. 2001;**108**:591-599

[98] Kipnis J, Yoles E, Schori H, Hauben E, Shaked I, Schwartz M. Neuronal survival after CNS insult is determined by a genetically encoded autoimmune response. The Journal of Neuroscience. 2001;**21**(13):4564-4571

[99] Mestre H, Ramirez M, Garcia E, Martiñón S, Cruz Y, Campos MG, et al. Lewis, Fischer 344, and Sprague-Dawley rats display differences in lipid peroxidation, motor recovery, and rubrospinal tract preservation after spinal cord injury. Frontiers in Neurology. 2015;**6**:108

[100] Yoles E, Hauben E, Palgi O, Agranov E, Gothilf A, Cohen A, et al. Protective autoimmunity is a physiological response to CNS trauma. The Journal of Neuroscience. 2001;**21**(11):3740-3748

[101] Walsh JT, Hendrix S, Boato F, Smirnov I, Zheng J, Lukens JR, et al. MHCII-independent CD4+ T cells protect injured CNS neurons via IL-4. 2015;**125**(6):2547

[102] Hu JG, Shi LL, Chen YJ, Xie XM, Zhang N, Zhu AY, et al. Differential effects of myelin basic protein-activated Th1 and Th2 cells on the local immune microenvironment of injured spinal cord. Experimental Neurology. 2016;**277**:190-201

[103] Walsh JT, Zheng J, Smirnov I, Lorenz U, Tung K, Kipnis J. Regulatory T cells in central nervous system injury: A double-edged sword. Journal of Immunology. 2014;**193**(10):5013-5022

[104] Kipnis J, Yoles E, Mizrahi T, Ben-Nur A, Schwartz M. Myelin specific Th1 cells are necessary for posttraumatic protective autoimmunity. Journal of Neuroimmunology. 2002;**130**(1):78-85

[105] Ishii H, Jin X, Ueno M, Tanabe S, Kubo T, Serada S, et al. Adoptive transfer of Th1-conditioned lymphocytes promotes axonal remodeling and functional recovery after spinal cord injury. Cell Death & Disease. 2012;**3**:e363

[106] Ibarra A, Hauben E, Butovsky O, Schwartz M. The therapeutic window after spinal cord injury can accommodate T cell-based vaccination and methylprednisolone in rats. The European Journal of Neuroscience. 2004;**19**(11):2984-2990

[107] Hauben E, Ibarra A, Mizrahi T, Barouch R, Agranov E, Schwartz M. Vaccination with a Nogo-A-derived peptide after incomplete spinal-cord injury promotes recovery via a T-cellmediated neuroprotective response: Comparison with other myelin antigens. Proceedings of the National Academy of Sciences of the United States of America. 2001;**98**:15173-15178

[108] Martinon S, Garcia-Vences E, Toscano-Tejeida D, Flores-Romero A, Rodriguez-Barrera R, Ferrusquia M, et al. Long-term production of BDNF and NT-3 induced by A91-immunization after spinal cord injury. BMC Neuroscience. 2016;**17**(1):42

[109] Karin N, Mitchell DJ, Brocke S, Ling N, Steinman L. Reversal of experimental autoimmune encephalomyelitis by a soluble peptide variant of a myelin basic protein epitope: T cell receptor antagonism and reduction of interferon gamma and tumor necrosis factor alpha production. The Journal of Experimental Medicine. 1994;**180**(6):2227-2237

[110] Stefferl A, Brehm U, Storch M, Lambracht-Washington D, Bourquin C, Wonigeit K, et al. Myelin oligodendrocyte glycoprotein induces experimental autoimmune encephalomyelitis in the "resistant" Brown Norway rat: Disease susceptibility is determined by MHC and MHC-linked effects on the B cell response. Journal of Immunology. 1999;**163**(1):40-49

[111] Wang L, Winnewisser J, Federle C, Jessberger G, Nave KA, Werner HB, et al. Epitope-specific tolerance modes differentially specify susceptibility to proteolipid proteininduced experimental autoimmune encephalomyelitis. Frontiers in Immunology. 2017;**8**:1511

[112] Wang Y, Wang K, Chao R, Li J, Zhou L, Ma J, et al. Neuroprotective effect of vaccination with autoantigenpulsed dendritic cells after spinal cord injury. The Journal of Surgical Research. 2012;**176**(1):281-292

[113] Mikami Y et al. Implantation of dendritic cells in injured adult spinal cord results in activation of endogenous neural stem/progenitor cells leading to de novo neurogenesis and functional recovery. Journal of Neuroscience Research 2004;**76**(4):453-65

[114] Yaguchi M, Tabuse M, Ohta S, Ohkusu-Tsukada K, Takeuchi T, Yamane J, et al. Transplantation of dendritic cells promotes functional recovery from spinal cord injury in common marmoset. Neuroscience Research. 2009;**65**(4):384-392

[115] Wang K, Chao R, Guo Q-N, Liu M-Y, Liang H-P, Liu P, et al. Expressions of some neurotrophins and neurotrophic cytokines at

site of spinal cord injury in mice after vaccination with dendritic cells pulsed with homogenate proteins. Neuroimmunomodulation. 2018;**20**(2):87-98

[116] Hauben E, Gothilf A, Cohen A, Butovsky O, Nevo U, Smirnov I, et al. Vaccination with dendritic cells pulsed with peptides of myelin basic protein promotes functional recovery from spinal cord injury. The Journal of Neuroscience. 2003;**23**(25):8808-8819

[117] Liu Y, Kim D, Himes BT, Chow SY, Schallert T, Murray M, et al. Transplants of fibroblasts genetically modified to express BDNF promote regeneration of adult rat rubrospinal axons and recovery of forelimb function. The Journal of Neuroscience. 1999;**19**(11):4370-4387

[118] Theele DP, Streit WJ. A chronicle of microglial ontogeny. Glia. 1993;**7**(1):5-8

[119] Greter M, Lelios I, Croxford AL. Microglia versus myeloid cell nomenclature during brain inflammation. Frontiers in Immunology. 2015;**6**:249

[120] Butovsky O, Jedrychowski MP, Moore CS, Cialic R, Lanser AJ, Gabriely G, et al. Identification of a unique TGF-beta-dependent molecular and functional signature in microglia. Nature Neuroscience. 2014;**17**(1):131-143

[121] Ling EA, Wong WC. The origin and nature of ramified and amoeboid microglia: A historical review and current concepts. Glia. 1993;**7**(1):9-18

[122] Kierdorf K, Prinz M. Microglia in steady state. 2017;**127**(9):3201-3209

[123] Cardona AE, Pioro EP, Sasse ME, Kostenko V, Cardona SM, Dijkstra IM, et al. Control of microglial neurotoxicity by the fractalkine receptor. Nature Neuroscience. 2006;**9**(7):917-924

**137**

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury*

macrophages to injured spinal cord is orchestrated by remote brain choroid plexus. Immunity. 2013;**38**(3):555-569

[133] Mrass P, Weninger W. Immune cell migration as a means to control immune privilege: Lessons from the CNS and tumors. Immunological Reviews.

[134] Hickey WF, Vass K, Lassmann H. Bone marrow-derived elements in the central nervous system: An immunohistochemical and ultrastructural survey of rat

chimeras. Journal of Neuropathology

and Experimental Neurology.

[135] Stoll G, Jander S. The role of microglia and macrophages in the pathophysiology of the CNS. Progress in Neurobiology. 1999;**58**(3):233-247

[136] David S, Kroner A. Repertoire of microglial and macrophage responses after spinal cord injury. Nature Reviews. Neuroscience. 2011;**12**(7):388-399

[138] Gensel JC, Zhang B. Macrophage activation and its role in repair and pathology after spinal cord injury. Brain

[139] Novak ML, Koh TJ. Phenotypic transitions of macrophages orchestrate tissue repair. The American Journal of Pathology. 2013;**183**(5):1352-1363

JE. Neuroprotection and acute spinal cord injury: A reappraisal. NeuroRx.

Barrandon Y, Longaker MT. Wound

[137] Shechter R, Schwartz M. Harnessing monocyte-derived macrophages to control central nervous system pathologies: No longer 'if' but 'how. The Journal of Pathology.

2013;**229**(2):332-346

Research. 2015;**1619**:1-11

[140] Hall ED, Springer

[141] Gurtner GC, Werner S,

2004;**1**(1):80-100

1992;**51**(3):246-256

2006;**213**:195-212

*DOI: http://dx.doi.org/10.5772/intechopen.84645*

interaction with OX2 (CD200). Science.

[125] Guillemin GJ, Brew BJ. Microglia,

macrophages, and pericytes: A review of function and identification. Journal of Leukocyte Biology. 2004;**75**(3):388-397

[126] Bechmann I, Priller J, Kovac A, Bontert M, Wehner T, Klett FF, et al. Immune surveillance of mouse brain perivascular spaces by blood-borne macrophages. The European Journal of Neuroscience. 2001;**14**(10):1651-1658

[127] Kivisäkk P, Imitola J, Rasmussen S, Elyaman W, Zhu B, Ransohoff RM, et al. Localizing CNS immune surveillance: Meningeal APCs activate T cells during EAE. Annals of Neurology.

[128] Ponomarev ED, Veremeyko T, Weiner HL. MicroRNAs are universal regulators of differentiation, activation, and polarization of microglia and macrophages in normal and diseased

CNS. Glia. 2013;**61**(1):91-103

[129] Chazaud B. Macrophages: Supportive cells for tissue repair and regeneration. Immunobiology.

[130] Shi C, Pamer EG. Monocyte recruitment during infection and inflammation. Nature Reviews. Immunology;**11**(11):762-774

[131] Geissmann F, Jung S, Littman DR. Blood monocytes consist of two principal subsets with distinct migratory properties. Immunity.

[132] Shechter R, Miller O, Yovel G, Rosenzweig N, London A, Ruckh J, et al. Recruitment of beneficial M2

2009;**65**(4):457-469

2014;**219**(3):172-178

2003;**19**(1):71-82

[124] Hoek RM, Ruuls SR, Murphy CA, Wright GJ, Goddard R, Zurawski

SM, et al. Down-regulation of the macrophage lineage through

2000;**290**(5497):1768-1771

macrophages, perivascular

*Transplantation or Transference of Cultured Cells as a Treatment for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.84645*

[124] Hoek RM, Ruuls SR, Murphy CA, Wright GJ, Goddard R, Zurawski SM, et al. Down-regulation of the macrophage lineage through interaction with OX2 (CD200). Science. 2000;**290**(5497):1768-1771

*Spinal Cord Injury Therapy*

1994;**180**(6):2227-2237

reduction of interferon gamma and tumor necrosis factor alpha production. The Journal of Experimental Medicine.

site of spinal cord injury in mice after vaccination with dendritic cells pulsed with homogenate proteins. Neuroimmunomodulation.

[116] Hauben E, Gothilf A, Cohen A, Butovsky O, Nevo U, Smirnov I, et al. Vaccination with dendritic cells pulsed with peptides of myelin basic protein promotes functional recovery from spinal cord injury. The Journal of Neuroscience. 2003;**23**(25):8808-8819

[117] Liu Y, Kim D, Himes BT, Chow SY, Schallert T, Murray M, et al. Transplants of fibroblasts genetically modified to express BDNF promote regeneration of adult rat rubrospinal axons and recovery of forelimb function. The Journal of Neuroscience. 1999;**19**(11):4370-4387

[118] Theele DP, Streit WJ. A chronicle of microglial ontogeny. Glia. 1993;**7**(1):5-8

inflammation. Frontiers in Immunology.

[119] Greter M, Lelios I, Croxford AL. Microglia versus myeloid cell nomenclature during brain

[120] Butovsky O, Jedrychowski MP, Moore CS, Cialic R, Lanser AJ, Gabriely G, et al. Identification of a unique TGF-beta-dependent molecular and functional signature in microglia. Nature Neuroscience.

[121] Ling EA, Wong WC. The origin and nature of ramified and amoeboid microglia: A historical review and current concepts. Glia. 1993;**7**(1):9-18

[122] Kierdorf K, Prinz M. Microglia in steady state. 2017;**127**(9):3201-3209

[123] Cardona AE, Pioro EP, Sasse ME, Kostenko V, Cardona SM, Dijkstra IM, et al. Control of microglial neurotoxicity by the fractalkine receptor. Nature Neuroscience. 2006;**9**(7):917-924

2015;**6**:249

2014;**17**(1):131-143

2018;**20**(2):87-98

[110] Stefferl A, Brehm U, Storch M, Lambracht-Washington D, Bourquin C, Wonigeit K, et al. Myelin oligodendrocyte glycoprotein induces experimental autoimmune encephalomyelitis in the "resistant"

Brown Norway rat: Disease

[111] Wang L, Winnewisser J, Federle C, Jessberger G, Nave KA, Werner HB, et al. Epitope-specific tolerance modes differentially specify susceptibility to proteolipid proteininduced experimental autoimmune encephalomyelitis. Frontiers in Immunology. 2017;**8**:1511

[112] Wang Y, Wang K, Chao R, Li J, Zhou L, Ma J, et al. Neuroprotective effect of vaccination with autoantigenpulsed dendritic cells after spinal cord injury. The Journal of Surgical Research.

[113] Mikami Y et al. Implantation of dendritic cells in injured adult spinal cord results in activation of endogenous neural stem/progenitor cells leading to de novo neurogenesis and functional recovery. Journal of Neuroscience Research 2004;**76**(4):453-65

[114] Yaguchi M, Tabuse M, Ohta S, Ohkusu-Tsukada K, Takeuchi T, Yamane J, et al. Transplantation of dendritic cells promotes functional recovery from spinal cord injury in common marmoset. Neuroscience Research.

[115] Wang K, Chao R, Guo Q-N, Liu M-Y, Liang H-P, Liu P, et al. Expressions of some neurotrophins and neurotrophic cytokines at

1999;**163**(1):40-49

2012;**176**(1):281-292

2009;**65**(4):384-392

susceptibility is determined by MHC and MHC-linked effects on the B cell response. Journal of Immunology.

**136**

[125] Guillemin GJ, Brew BJ. Microglia, macrophages, perivascular macrophages, and pericytes: A review of function and identification. Journal of Leukocyte Biology. 2004;**75**(3):388-397

[126] Bechmann I, Priller J, Kovac A, Bontert M, Wehner T, Klett FF, et al. Immune surveillance of mouse brain perivascular spaces by blood-borne macrophages. The European Journal of Neuroscience. 2001;**14**(10):1651-1658

[127] Kivisäkk P, Imitola J, Rasmussen S, Elyaman W, Zhu B, Ransohoff RM, et al. Localizing CNS immune surveillance: Meningeal APCs activate T cells during EAE. Annals of Neurology. 2009;**65**(4):457-469

[128] Ponomarev ED, Veremeyko T, Weiner HL. MicroRNAs are universal regulators of differentiation, activation, and polarization of microglia and macrophages in normal and diseased CNS. Glia. 2013;**61**(1):91-103

[129] Chazaud B. Macrophages: Supportive cells for tissue repair and regeneration. Immunobiology. 2014;**219**(3):172-178

[130] Shi C, Pamer EG. Monocyte recruitment during infection and inflammation. Nature Reviews. Immunology;**11**(11):762-774

[131] Geissmann F, Jung S, Littman DR. Blood monocytes consist of two principal subsets with distinct migratory properties. Immunity. 2003;**19**(1):71-82

[132] Shechter R, Miller O, Yovel G, Rosenzweig N, London A, Ruckh J, et al. Recruitment of beneficial M2

macrophages to injured spinal cord is orchestrated by remote brain choroid plexus. Immunity. 2013;**38**(3):555-569

[133] Mrass P, Weninger W. Immune cell migration as a means to control immune privilege: Lessons from the CNS and tumors. Immunological Reviews. 2006;**213**:195-212

[134] Hickey WF, Vass K, Lassmann H. Bone marrow-derived elements in the central nervous system: An immunohistochemical and ultrastructural survey of rat chimeras. Journal of Neuropathology and Experimental Neurology. 1992;**51**(3):246-256

[135] Stoll G, Jander S. The role of microglia and macrophages in the pathophysiology of the CNS. Progress in Neurobiology. 1999;**58**(3):233-247

[136] David S, Kroner A. Repertoire of microglial and macrophage responses after spinal cord injury. Nature Reviews. Neuroscience. 2011;**12**(7):388-399

[137] Shechter R, Schwartz M. Harnessing monocyte-derived macrophages to control central nervous system pathologies: No longer 'if' but 'how. The Journal of Pathology. 2013;**229**(2):332-346

[138] Gensel JC, Zhang B. Macrophage activation and its role in repair and pathology after spinal cord injury. Brain Research. 2015;**1619**:1-11

[139] Novak ML, Koh TJ. Phenotypic transitions of macrophages orchestrate tissue repair. The American Journal of Pathology. 2013;**183**(5):1352-1363

[140] Hall ED, Springer JE. Neuroprotection and acute spinal cord injury: A reappraisal. NeuroRx. 2004;**1**(1):80-100

[141] Gurtner GC, Werner S, Barrandon Y, Longaker MT. Wound repair and regeneration. Nature. 2008;**453**(7193):314-321

[142] Kigerl KA, McGaughy VM, Popovich PG. Comparative analysis of lesion development and intraspinal inflammation in four strains of mice following spinal contusion injury. The Journal of Comparative Neurology. 2006;**494**(4):578-594

[143] Guerrero AR, Uchida K, Nakajima H, Watanabe S, Nakamura M, Johnson WE, et al. Blockade of interleukin-6 signaling inhibits the classic pathway and promotes an alternative pathway of macrophage activation after spinal cord injury in mice. Journal of Neuroinflammation. 2012;**9**:40

[144] Ma SF, Chen YJ, Zhang JX, Shen L, Wang R, Zhou JS, et al. Adoptive transfer of M2 macrophages promotes locomotor recovery in adult rats after spinal cord injury. Brain, Behavior, and Immunity. 2015;**45**:157-170

[145] Knoller N, Auerbach G, Fulga V, Zelig G, Attias J, Bakimer R, et al. Clinical experience using incubated autologous macrophages as a treatment for complete spinal cord injury: Phase I study results. Journal of Neurosurgery. Spine. 2005;**3**(3):173-181

[146] Zhang B, Bailey WM, Kopper TJ, Orr MB, Feola DJ, Gensel JC. Azithromycin drives alternative macrophage activation and improves recovery and tissue sparing in contusion spinal cord injury. Journal of Neuroinflammation. 2015;**12**:218

[147] Yu TB, Cheng YS, Zhao P, Kou DW, Sun K, Chen BH, et al. Immune therapy with cultured microglia grafting into the injured spinal cord promoting the recovery of rat's hind limb motor function. Chinese Journal of Traumatology. 2009;**12**(5):291-295

[148] Sato A, Ohtaki H, Tsumuraya T, Song D, Ohara K, Asano M, et al. Interleukin-1 participates in the classical and alternative activation of microglia/macrophages after spinal cord injury. Journal of Neuroinflammation. 2012;**9**:65

**139**

**Chapter 8**

*and Vivek Nair*

**Abstract**

**1. Introduction**

significantly [4].

novel neurorestorative strategies.

Neuroregenerative-Rehabilitative

Spinal cord injury is one of the leading causes of disability worldwide. Current mainstay treatment strategies consist of surgical and medical management in acute and subacute stage. Rehabilitative management in the chronic stage. None of the existing strategies can repair the damage to the spinal cord and recover neurological functioning. Stem cells have promising results in pre-clinical and clinical studies. Various pre-clinical studies have evidenced neuro-regenerative capabilities of stem cells and shown neural recovery. Clinical studies have also shown improvements in neurological functions and quality of life. This chapter discusses about different types of cells available, routes of administration available to transplant these cells, dosages of cell and optimum time after injury at which cells should be transplanted based on world-wide literature. We have also discussed results following our protocol of intrathecal transplantation of autologous bone marrow mononuclear cells. Although, not a cure, stem cell therapy further improves quality of life, functional independence and reduces secondary complications when combined with existing

Therapy for Spinal Cord Injury

*Alok Sharma, Hemangi Sane, Nandini Gokulchandran,* 

*Prerna Badhe, Amruta Paranjape, Pooja Kulkarni* 

treatment strategies; neuroregenerative rehabilitative therapy.

spinal cord injury, paracrine effect, neurorestoration

**Keywords:** stem cell therapy, autologous, bone marrow mononuclear cells,

Spinal cord injury (SCI) is a disabling neurologic disorder that can lead to motor and sensory impairment causing, paraplegia or tetraplegia. It can also exhibit bladder and bowel impairment, respiratory impairment and autonomic dysfunction [1]. The incidence of the disease is estimated to be 223–755 per million worldwide [2, 3]. The healing and recovery process during different phases since the time of injury differ

Current treatment options consist of surgical management complimented by administration of methylprednisolone in the acute stage; prevention of secondary injury in the sub-acute stage and multidisciplinary rehabilitation management in the chronic stage. Due to insufficient neuroregenerative capabilities of these treatments, they fail to reverse the damage to neurons and symptoms of neurological deficit [5–8]. Therefore, there is an unmet medical need which warrants exploring

#### **Chapter 8**

*Spinal Cord Injury Therapy*

2008;**453**(7193):314-321

2006;**494**(4):578-594

repair and regeneration. Nature.

Interleukin-1 participates in the classical and alternative activation of microglia/macrophages after spinal cord injury. Journal of Neuroinflammation.

2012;**9**:65

[142] Kigerl KA, McGaughy VM, Popovich PG. Comparative analysis of lesion development and intraspinal inflammation in four strains of mice following spinal contusion injury. The Journal of Comparative Neurology.

[143] Guerrero AR, Uchida K, Nakajima H, Watanabe S, Nakamura M, Johnson WE, et al. Blockade of interleukin-6 signaling inhibits the classic pathway and promotes an alternative pathway of macrophage activation after spinal cord injury in mice. Journal of Neuroinflammation. 2012;**9**:40

[144] Ma SF, Chen YJ, Zhang JX, Shen L, Wang R, Zhou JS, et al. Adoptive transfer of M2 macrophages promotes locomotor recovery in adult rats after spinal cord injury. Brain, Behavior, and

Immunity. 2015;**45**:157-170

Spine. 2005;**3**(3):173-181

[145] Knoller N, Auerbach G, Fulga V, Zelig G, Attias J, Bakimer R, et al. Clinical experience using incubated autologous macrophages as a treatment for complete spinal cord injury: Phase I study results. Journal of Neurosurgery.

[146] Zhang B, Bailey WM, Kopper TJ, Orr MB, Feola DJ, Gensel JC. Azithromycin drives alternative macrophage activation and improves recovery and tissue sparing in

contusion spinal cord injury. Journal of Neuroinflammation. 2015;**12**:218

[147] Yu TB, Cheng YS, Zhao P, Kou DW, Sun K, Chen BH, et al. Immune therapy with cultured microglia grafting into the injured spinal cord promoting the recovery of rat's hind limb motor function. Chinese Journal of Traumatology. 2009;**12**(5):291-295

[148] Sato A, Ohtaki H, Tsumuraya T, Song D, Ohara K, Asano M, et al.

**138**

## Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury

*Alok Sharma, Hemangi Sane, Nandini Gokulchandran, Prerna Badhe, Amruta Paranjape, Pooja Kulkarni and Vivek Nair*

#### **Abstract**

Spinal cord injury is one of the leading causes of disability worldwide. Current mainstay treatment strategies consist of surgical and medical management in acute and subacute stage. Rehabilitative management in the chronic stage. None of the existing strategies can repair the damage to the spinal cord and recover neurological functioning. Stem cells have promising results in pre-clinical and clinical studies. Various pre-clinical studies have evidenced neuro-regenerative capabilities of stem cells and shown neural recovery. Clinical studies have also shown improvements in neurological functions and quality of life. This chapter discusses about different types of cells available, routes of administration available to transplant these cells, dosages of cell and optimum time after injury at which cells should be transplanted based on world-wide literature. We have also discussed results following our protocol of intrathecal transplantation of autologous bone marrow mononuclear cells. Although, not a cure, stem cell therapy further improves quality of life, functional independence and reduces secondary complications when combined with existing treatment strategies; neuroregenerative rehabilitative therapy.

**Keywords:** stem cell therapy, autologous, bone marrow mononuclear cells, spinal cord injury, paracrine effect, neurorestoration

#### **1. Introduction**

Spinal cord injury (SCI) is a disabling neurologic disorder that can lead to motor and sensory impairment causing, paraplegia or tetraplegia. It can also exhibit bladder and bowel impairment, respiratory impairment and autonomic dysfunction [1].

The incidence of the disease is estimated to be 223–755 per million worldwide [2, 3]. The healing and recovery process during different phases since the time of injury differ significantly [4].

Current treatment options consist of surgical management complimented by administration of methylprednisolone in the acute stage; prevention of secondary injury in the sub-acute stage and multidisciplinary rehabilitation management in the chronic stage. Due to insufficient neuroregenerative capabilities of these treatments, they fail to reverse the damage to neurons and symptoms of neurological deficit [5–8]. Therefore, there is an unmet medical need which warrants exploring novel neurorestorative strategies.

Stem cell therapy has emerged as a promising regimen to bring about neuroregeneration and neural functional benefits, hence can be termed as neuroregenerative therapy. Various cell types being explored for their effectiveness are bone mesenchymal stem cells (BMSCs), bone marrow mononuclear cells (BMMNCs), umbilical cord-derived mesenchymal stem cells (UCMSCs), adipose-derived stem cells (ADSCs), olfactory ensheathing cells (OECs), and fetal brain-derived neural stem/progenitor cell (FB-DNS/PCs), induced pluripotent stem cells (iPSCs) and others [9–12].

The earliest attempt in translational research were by Geron Corporation who had announced a clinical trial using human embryonic stem cell (ESC)-derived oligodendrocyte progenitor cells (OPCs) in patients with spinal cord injury at the site of the lesion [13]. Due to ethical and safety risks involved in ESC they were not widely accepted for clinical use. Advent of knowledge of the role of adult stem cells in natural repair processes of the body lead to clinical exploration of these cells. Some of the earliest published work was by Geffner et al. in 2008, by transplantation of adult bone marrow stem cells through multiple routes, that is, intraspinal, intrathecal and intravenous in patients with SCI [14]. The study demonstrated that these cells and routes were safe and feasible. Many adult stem cell types, routes and clinical protocols have since been tested clinically [14–33].

Clinical outcome and effectiveness of cell transplantation remains variable due to the heterogenicity of cell types, dosages, route of transplantation, level of manipulation and treatment regimens followed thereafter. This chapter provides a detail review about different stem cell therapies available for the management of spinal cord injury and their clinical outcomes as seen in published literature.

#### **2. What are stem cells?**

Stem cell is an undifferentiated cell, which can self-renew to replicate itself as well as give rise to the specialized cells under appropriate conditions [34].

Stem cells are the undifferentiated cells that can give rise to progeny identical to themselves (de-differentiation) or specialized cells different from them (transdifferentiation). All regenerative processes in the human body during developmental pre-natal stages as well as post-natal and adult stages follow these two routes. Recently, the technological advances have given rise to another route, reprogramming cells to acquire properties of trans-differentiation [35].

Depending upon their ability to de-differentiate or transdifferentiate, the source of cells, processing required to harvest the cells and host in which cells are transplanted; the cells can be categorized into various types which are described in detail in the next section.

#### **3. Types of stem cells**

#### **3.1 Based on the potency of cells**

Depending upon their differentiation potential, cells are classified as unipotent, multipotent, pluripotent and totipotent (**Figure 1**).

Totipotent cells can differentiate into embryonic as well as extraembryonic and placental cells [36]. Pluripotent cells can differentiate into embryonic cells only.

**141**

tissue [37].

**Figure 1.**

**4.1 Remyelination**

*Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury*

These possess the property of de-differentiation as well as trans-differentiation into cell types of all three germ layers [36]. Cells that can be harvested after birth are called 'adult stem cells'. Most of the adult stem cells are multipotent or unipotent. Multipotent cells possess the property of trans-differentiation into cells of different tissues whereas unipotent cells can only de-differentiate to create progeny identical to themselves or a differentiated cell type of only one specific

If the cells are harvested from and transplanted to the same person, these are called autologous cells; but if the cells are harvested from a host different from that

The immediate impact of injury to spinal cord is on the ascending and descending pathways and blood vessels in the spinal cord. Disrupted circulation leads to infarction of the local tissue due to hypoxia and ischemia causing neuronal loss and demyelination. This is clinically presented as spinal shock, systemic hypotension, vasospasm, ischemia, ionic imbalance and neurotransmitter accumulation [38]. Transplantation of cells can remyelinate damaged tissue and aid in symptom recovery. Human ESC-derived OPCs transplanted into the rats with spinal cord injury showed enhanced remyelination and locomotor ability when transplanted in the sub-acute phase as opposed to chronic phase after spinal cord injury [39]. Neural precursor cells also showed differentiation into oligodendrocytes ensheathing the

**3.2 Based on the host in whom cells are transplanted**

**4. Mechanism of action of stem cells in spinal cord injury**

of the recipient these are called allogenic cells.

*Different types of cells based on their potency.*

*DOI: http://dx.doi.org/10.5772/intechopen.88808*

*Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.88808*

*Spinal Cord Injury Therapy*

others [9–12].

cally [14–33].

literature.

**2. What are stem cells?**

in the next section.

**3. Types of stem cells**

**3.1 Based on the potency of cells**

multipotent, pluripotent and totipotent (**Figure 1**).

Stem cell therapy has emerged as a promising regimen to bring about neuroregeneration and neural functional benefits, hence can be termed as neuroregenerative therapy. Various cell types being explored for their effectiveness are bone mesenchymal stem cells (BMSCs), bone marrow mononuclear cells (BMMNCs), umbilical cord-derived mesenchymal stem cells (UCMSCs), adipose-derived stem cells (ADSCs), olfactory ensheathing cells (OECs), and fetal brain-derived neural stem/progenitor cell (FB-DNS/PCs), induced pluripotent stem cells (iPSCs) and

The earliest attempt in translational research were by Geron Corporation who had announced a clinical trial using human embryonic stem cell (ESC)-derived oligodendrocyte progenitor cells (OPCs) in patients with spinal cord injury at the site of the lesion [13]. Due to ethical and safety risks involved in ESC they were not widely accepted for clinical use. Advent of knowledge of the role of adult stem cells in natural repair processes of the body lead to clinical exploration of these cells. Some of the earliest published work was by Geffner et al. in 2008, by transplantation of adult bone marrow stem cells through multiple routes, that is, intraspinal, intrathecal and intravenous in patients with SCI [14]. The study demonstrated that these cells and routes were safe and feasible. Many adult stem cell types, routes and clinical protocols have since been tested clini-

Clinical outcome and effectiveness of cell transplantation remains variable due to the heterogenicity of cell types, dosages, route of transplantation, level of manipulation and treatment regimens followed thereafter. This chapter provides a detail review about different stem cell therapies available for the management of spinal cord injury and their clinical outcomes as seen in published

Stem cell is an undifferentiated cell, which can self-renew to replicate itself as

Stem cells are the undifferentiated cells that can give rise to progeny identical to themselves (de-differentiation) or specialized cells different from them (transdifferentiation). All regenerative processes in the human body during developmental pre-natal stages as well as post-natal and adult stages follow these two routes. Recently, the technological advances have given rise to another route, reprogram-

Depending upon their ability to de-differentiate or transdifferentiate, the source of cells, processing required to harvest the cells and host in which cells are transplanted; the cells can be categorized into various types which are described in detail

Depending upon their differentiation potential, cells are classified as unipotent,

Totipotent cells can differentiate into embryonic as well as extraembryonic and placental cells [36]. Pluripotent cells can differentiate into embryonic cells only.

well as give rise to the specialized cells under appropriate conditions [34].

ming cells to acquire properties of trans-differentiation [35].

**140**

**Figure 1.** *Different types of cells based on their potency.*

These possess the property of de-differentiation as well as trans-differentiation into cell types of all three germ layers [36]. Cells that can be harvested after birth are called 'adult stem cells'. Most of the adult stem cells are multipotent or unipotent. Multipotent cells possess the property of trans-differentiation into cells of different tissues whereas unipotent cells can only de-differentiate to create progeny identical to themselves or a differentiated cell type of only one specific tissue [37].

#### **3.2 Based on the host in whom cells are transplanted**

If the cells are harvested from and transplanted to the same person, these are called autologous cells; but if the cells are harvested from a host different from that of the recipient these are called allogenic cells.

#### **4. Mechanism of action of stem cells in spinal cord injury**

#### **4.1 Remyelination**

The immediate impact of injury to spinal cord is on the ascending and descending pathways and blood vessels in the spinal cord. Disrupted circulation leads to infarction of the local tissue due to hypoxia and ischemia causing neuronal loss and demyelination. This is clinically presented as spinal shock, systemic hypotension, vasospasm, ischemia, ionic imbalance and neurotransmitter accumulation [38]. Transplantation of cells can remyelinate damaged tissue and aid in symptom recovery. Human ESC-derived OPCs transplanted into the rats with spinal cord injury showed enhanced remyelination and locomotor ability when transplanted in the sub-acute phase as opposed to chronic phase after spinal cord injury [39]. Neural precursor cells also showed differentiation into oligodendrocytes ensheathing the

axons, these cells expressed myelin suggesting the remyelination potential of these cells. Rat models, both in sub-acute and chronic phase of spinal cord injury showed improved functional outcome. Remyelination was better in sub-acute as compared with chronic phase [40]. Human UCB cells transplanted 7 days after spinal cord injury in the rats also showed remyelination of axons improving functional outcome [41]. Similar results were observed using adult bone marrow mononuclear cells [42].

#### **4.2 Anti-inflammatory effect**

Inflammation in response to the injury is both protective and damaging to the tissue. Secondary injury is perpetrated by uncontrolled inflammatory response proinflammatory cytokine release [43–46]. Various studies have explored anti-inflammatory effect of MSCs, NPCs, BMMNCs, ESCs and UCB cells. Cell transplantation reduces the expression of pro-inflammatory cytokines TNFα, IL-4, IL-1β, IL-2, IL-6, IL-7, IL-12 and interferon gamma [47–50].

#### **4.3 Neoangiogenesis**

Transplanted cells have been shown to secrete various growth factors and stimulate the resident cells to secret these factors through their paracrine effect. One of the growth factors secreted is vascular endothelial growth factor (VEGF) which stimulates neoangiogenesis. This proangiogenic effect has been evidenced by increased vascularization of the lesion area in various preclinical studies [51–54].

#### **4.4 Neuro-regeneration**

Transplanted cells of various cells possess neurogenic potential. Cells have been shown to differentiate into neuronal as well as non-neuronal tissues. Axon sprouting is noticed in the transplanted regions. Endogenous neurogenetic processes are also catalyzed by the growth factors like brain-derived neurotrophic factor (BDNF) secreted by these cells. Synaptic pruning is also observed. These changes are further reinforced by the functional locomotor recovery seen post transplantation [55, 56].

#### **4.5 Neurotrophic and antiapoptotic effect**

Cells secret and facilitate endogenous secretion of various growth factors like fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), neural growth factor (NGF), glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor (BDNF). These wield neurotrophic effect protecting the neurons from secondary injury and apoptosis (**Figure 2**) [54, 57].

**143**

*Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury*

enhancing neuronal survival post SCI in mice [61–63].

**5. Literature review of published evidence for efficacy of stem cells**

These cells can be harvested from preimplantation blastocyst after immunosurgical removal of trophectoderm to access the inner cells mass [58]. hESCs are pluripotent and can differentiate into cells of ectodermal origin, that is, neuronal and glial cells. hESCs derived oligodendrocyte progenitor cells (OPCs) have shown neuronal recovery more effectively in the acute phase as compared to chronic phase of spinal cord injury [39, 59, 60]. Neural stem cells (NSCs) have the potential to differentiate into neural and non-neural tissue. Neuroregenerative potential of these exhibited as remyelination of damaged axons and secretion of neurotrophic factors

Despite promising results in pre-clinical studies, clinical translation of these is limited due to ethical concerns, risk of immune rejection and tumorigenicity [64].

Adult stem cells like bone marrow stromal cells (BMSCs), mesenchymal stem cells (MSCs), umbilical cord stromal cells (UCSCs), umbilical cord mesenchymal cells (UC-MSCs), adipose-derived stem cells and dental pulp-derived stem cells are examples of multipotent stem cells [51]. MSCs and BMSCs are easy to harvest as they are available in the bone marrow. However, MSCs are available in a small number and therefore need to be expanded in-vitro before transplantation. These cells can migrate and home onto the site of injury therefore can be administered through a less invasive route distant from the site of injury. Unlike pluripotent cells, these cells show better functional recovery in chronic SCI [41, 42, 65]. Transplantation of these cells has shown functional and motor recovery in rats after SCI in several studies. These benefits are postulated to be due to neurotrophic, immunomodulatory and neoangiogenic effect of these cells in addition to their ability to differenti-

Last decade has seen rise in efforts to develop technologies to improve quality and efficiency of reprogramming of cells to induce pluripotency. iPSCs are also pluripotent and give rise to neuronal as well as non-neuronal tissue. Transplantation of progenitors derived from iPSCs have shown ability for remyelination of damaged neurons and improved nerve conduction. These cells can migrate long distances and therefore can be administered at a remote site which is less invasive. Apart from neuroregeneration, the cells are also capable of immunomodulation and synaptic

The technology is still in its nascent stage, although promising, successful clini-

One of the earliest studies used cells from the fetal nervous and hemopoietic tissues in 15 SCI patients with no side effects [73]. However, due to various ethical

*DOI: http://dx.doi.org/10.5772/intechopen.88808*

*5.1.1 Human embryonic stem cells (hESCs)*

**5.1 Pre-clinical**

*5.1.2 Multipotent stem cells*

ate neural cells [66].

reconstruction [67–72].

**5.2 Clinical**

cal translation has barriers.

*5.2.1 Embryonic stem cells (ESCs)*

*5.1.3 Induced pluripotent stem cells (iPSCs)*

**Figure 2.** *Bone marrow aspiration.*

#### **5. Literature review of published evidence for efficacy of stem cells**

#### **5.1 Pre-clinical**

*Spinal Cord Injury Therapy*

**4.2 Anti-inflammatory effect**

**4.3 Neoangiogenesis**

**4.4 Neuro-regeneration**

transplantation [55, 56].

**4.5 Neurotrophic and antiapoptotic effect**

[51–54].

IL-6, IL-7, IL-12 and interferon gamma [47–50].

cells [42].

axons, these cells expressed myelin suggesting the remyelination potential of these cells. Rat models, both in sub-acute and chronic phase of spinal cord injury showed improved functional outcome. Remyelination was better in sub-acute as compared with chronic phase [40]. Human UCB cells transplanted 7 days after spinal cord injury in the rats also showed remyelination of axons improving functional outcome [41]. Similar results were observed using adult bone marrow mononuclear

Inflammation in response to the injury is both protective and damaging to the tissue. Secondary injury is perpetrated by uncontrolled inflammatory response proinflammatory cytokine release [43–46]. Various studies have explored anti-inflammatory effect of MSCs, NPCs, BMMNCs, ESCs and UCB cells. Cell transplantation reduces the expression of pro-inflammatory cytokines TNFα, IL-4, IL-1β, IL-2,

Transplanted cells have been shown to secrete various growth factors and stimulate the resident cells to secret these factors through their paracrine effect. One of the growth factors secreted is vascular endothelial growth factor (VEGF) which stimulates neoangiogenesis. This proangiogenic effect has been evidenced by increased vascularization of the lesion area in various preclinical studies

Transplanted cells of various cells possess neurogenic potential. Cells have been shown to differentiate into neuronal as well as non-neuronal tissues. Axon sprouting is noticed in the transplanted regions. Endogenous neurogenetic processes are also catalyzed by the growth factors like brain-derived neurotrophic factor (BDNF) secreted by these cells. Synaptic pruning is also observed. These changes are further reinforced by the functional locomotor recovery seen post

Cells secret and facilitate endogenous secretion of various growth factors like fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), neural growth factor (NGF), glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor (BDNF). These wield neurotrophic effect protecting the

neurons from secondary injury and apoptosis (**Figure 2**) [54, 57].

**142**

**Figure 2.**

*Bone marrow aspiration.*

#### *5.1.1 Human embryonic stem cells (hESCs)*

These cells can be harvested from preimplantation blastocyst after immunosurgical removal of trophectoderm to access the inner cells mass [58]. hESCs are pluripotent and can differentiate into cells of ectodermal origin, that is, neuronal and glial cells. hESCs derived oligodendrocyte progenitor cells (OPCs) have shown neuronal recovery more effectively in the acute phase as compared to chronic phase of spinal cord injury [39, 59, 60]. Neural stem cells (NSCs) have the potential to differentiate into neural and non-neural tissue. Neuroregenerative potential of these exhibited as remyelination of damaged axons and secretion of neurotrophic factors enhancing neuronal survival post SCI in mice [61–63].

Despite promising results in pre-clinical studies, clinical translation of these is limited due to ethical concerns, risk of immune rejection and tumorigenicity [64].

#### *5.1.2 Multipotent stem cells*

Adult stem cells like bone marrow stromal cells (BMSCs), mesenchymal stem cells (MSCs), umbilical cord stromal cells (UCSCs), umbilical cord mesenchymal cells (UC-MSCs), adipose-derived stem cells and dental pulp-derived stem cells are examples of multipotent stem cells [51]. MSCs and BMSCs are easy to harvest as they are available in the bone marrow. However, MSCs are available in a small number and therefore need to be expanded in-vitro before transplantation. These cells can migrate and home onto the site of injury therefore can be administered through a less invasive route distant from the site of injury. Unlike pluripotent cells, these cells show better functional recovery in chronic SCI [41, 42, 65]. Transplantation of these cells has shown functional and motor recovery in rats after SCI in several studies. These benefits are postulated to be due to neurotrophic, immunomodulatory and neoangiogenic effect of these cells in addition to their ability to differentiate neural cells [66].

#### *5.1.3 Induced pluripotent stem cells (iPSCs)*

Last decade has seen rise in efforts to develop technologies to improve quality and efficiency of reprogramming of cells to induce pluripotency. iPSCs are also pluripotent and give rise to neuronal as well as non-neuronal tissue. Transplantation of progenitors derived from iPSCs have shown ability for remyelination of damaged neurons and improved nerve conduction. These cells can migrate long distances and therefore can be administered at a remote site which is less invasive. Apart from neuroregeneration, the cells are also capable of immunomodulation and synaptic reconstruction [67–72].

The technology is still in its nascent stage, although promising, successful clinical translation has barriers.

#### **5.2 Clinical**

#### *5.2.1 Embryonic stem cells (ESCs)*

One of the earliest studies used cells from the fetal nervous and hemopoietic tissues in 15 SCI patients with no side effects [73]. However, due to various ethical and medical concerns the use of these cells in clinical trials and application is restricted worldwide.

#### *5.2.2 Multipotent stem cells*

Various studies have explored and demonstrated safety and feasibility of multipotent stem cells [15, 17, 74–83].

#### *5.2.2.1 Bone marrow mononuclear cells*

In a comparison between transplantation of autologous bone marrow cells directly into the SCI sites administered with subcutaneous injections of granulocyte macrophage colony stimulating factor (GM-CSF) {n = 5} and only administration of GM-CSF {n = 1}, combination group showed better improvements. Improvements were noted during 3–7 months post procedure, 1 patient from the combination group showed change in the AIS grade as well. There were mild side effects associated with GM-CSF administration like Fever, myalgia and leukocytosis; however, there were no irreversible adverse events noted, neither was there any neurological deterioration [16]. Kumar et al. studied the effect of bone marrow mononuclear cells and noted that there was perceptible improvement in 32.6% of the patients with no major irreversible adverse effects. Outcome did not vary with the time taken from the injury till intervention [35]. Al-Zoubi et al. demonstrated the positive effect of purified autologous leukapheresis-derived CD34+ and CD133+ stem cells in 19 cases of chronic SCI [29]. Our published results with mononuclear cells are discussed in detail in the later part of the chapter [84, 85].

#### *5.2.2.2 Mesenchymal cells*

In a novel method, using combination of bone marrow mesenchymal stem cells (BM-MSC) and patient's autoimmune T cells, Moviglia et al. demonstrated the neuro-regeneration phenomenon-based changes in the inflammatory processes at the site of injury. Both the patients showed motor and sensory recovery with no adverse effects [17]. Peripheral stem cells and macrophages have also been reported to show improvements of motor and sensory functions without any adverse effects [18, 19]. Cheng et al. in a controlled study including 34 cases of thoracolumbar spinal cord injury, stated that umbilical cord mesenchymal stem cells effectively improve neurological functional recovery after spinal cord injury, and its efficacy is superior to that of rehabilitation therapy and selfhealing [30].

#### *5.2.2.3 Others*

Other sources such as cord blood, olfactory ensheathing cells and adipose tissue derived stem cells also showed improvement in sensory-motor functional improvements [20–24]. Saberi et al. studied the safety of intramedullary Schwann cell transplantation in 33 patients over the period of 2 years, there were no tumor formation or other adverse events recorded [25].

#### *5.2.2.4 Co-transplantation of multiple cell types*

Co-transplantation of cells has also been explored. Combined use of olfactory ensheathing cells and Schwann cells enhanced functional recovery [27]. Similarly,

**145**

(**Figure 3**).

marrow.

*Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury*

Chen et al. in their study of 28 cases showed beneficial effects of OECs, SCs, or a

Multipotent adult stem cells are safe to use clinically and have demonstrated

Several comparative studies have been carried out to determine the optimum route of administration. Geffner et al. reported administration of BMSCs intravenous, into the spinal canal and into the spinal cord to be safe and feasible. They also demonstrated improved ASIA, Barthel Index. Ashworth and Frenkel scores suggesting improved quality of life in most patients [14]. While intra-arterial transplantation of autologous bone marrow stem cells showed more improvements as compared with that of intravenous route, intravenous transplantation showed better neurological outcome as compared to the site of injury [31–33]. Systemic routes show considerable dilution of cells at various cells like kidneys, liver, spleen and lungs. Several intraspinal approaches like intraparenchymal, intralesional and intramedullary approaches have been explored. Although no serious adverse events were noted; some patients complained of transient increase in paresthesia and muscle cramps. Intraspinal approaches are associated with increased risk of procedure related adverse effect due to invasive nature of the procedure [86–88]. Saito et al. [89], Pal et al. [90] and Kumar et al. [91] reported intrathecal administration to be the optimum route of administration. Although in this approach cells are transplanted away from the lesion area, MRI studies of radiolabeled cells have shown successful homing of cells at the site of

**6. Published clinical results of NeuroGen Brain and Spine Institute**

All the patients are thoroughly assessed clinically to rule out presence of active infections, HIV or HBsAg positive status and malignancies. Routine serological tests and chest X-ray are performed to ensure medical fitness. Neuroimaging using functional MRI brain and MRI of spine is performed. Various clinical outcome measures are marked before procedure assessing muscle tone, strength, ambulation and sensations. Granulocyte colony stimulating factor injections are given 48 and 24 h prior to the transplantation to enhance proliferation of cells in the bone

Our protocol has been designed after careful review of available literature. The protocol for harvesting and transplanting the cells is minimally invasive with no

80–120 ml of bone marrow is aspirated from anterior superior iliac spine

*DOI: http://dx.doi.org/10.5772/intechopen.88808*

combination of them in SCI [28].

improved neurological outcome.

*5.2.3 Routes of transplantation*

injury [92].

**6.1 Our protocol**

*6.1.1 Pre-intervention protocol*

*6.1.2 Intervention protocol*

*6.1.2.1 Aspiration of bone marrow*

major adverse effects. It consists of three steps.

Chen et al. in their study of 28 cases showed beneficial effects of OECs, SCs, or a combination of them in SCI [28].

Multipotent adult stem cells are safe to use clinically and have demonstrated improved neurological outcome.

#### *5.2.3 Routes of transplantation*

*Spinal Cord Injury Therapy*

restricted worldwide.

chapter [84, 85].

healing [30].

*5.2.2.3 Others*

*5.2.2.2 Mesenchymal cells*

*5.2.2 Multipotent stem cells*

potent stem cells [15, 17, 74–83].

*5.2.2.1 Bone marrow mononuclear cells*

and medical concerns the use of these cells in clinical trials and application is

Various studies have explored and demonstrated safety and feasibility of multi-

In a comparison between transplantation of autologous bone marrow cells directly into the SCI sites administered with subcutaneous injections of granulocyte macrophage colony stimulating factor (GM-CSF) {n = 5} and only administration of GM-CSF {n = 1}, combination group showed better improvements. Improvements were noted during 3–7 months post procedure, 1 patient from the combination group showed change in the AIS grade as well. There were mild side effects associated with GM-CSF administration like Fever, myalgia and leukocytosis; however, there were no irreversible adverse events noted, neither was there any neurological deterioration [16]. Kumar et al. studied the effect of bone marrow mononuclear cells and noted that there was perceptible improvement in 32.6% of the patients with no major irreversible adverse effects. Outcome did not vary with the time taken from the injury till intervention [35]. Al-Zoubi et al. demonstrated the positive effect of purified autologous leukapheresis-derived CD34+ and CD133+ stem cells in 19 cases of chronic SCI [29]. Our published results with mononuclear cells are discussed in detail in the later part of the

In a novel method, using combination of bone marrow mesenchymal stem cells (BM-MSC) and patient's autoimmune T cells, Moviglia et al. demonstrated the neuro-regeneration phenomenon-based changes in the inflammatory processes at the site of injury. Both the patients showed motor and sensory recovery with no adverse effects [17]. Peripheral stem cells and macrophages have also been reported to show improvements of motor and sensory functions without any adverse effects [18, 19]. Cheng et al. in a controlled study including 34 cases of thoracolumbar spinal cord injury, stated that umbilical cord mesenchymal stem cells effectively improve neurological functional recovery after spinal cord injury, and its efficacy is superior to that of rehabilitation therapy and self-

Other sources such as cord blood, olfactory ensheathing cells and adipose tissue derived stem cells also showed improvement in sensory-motor functional improvements [20–24]. Saberi et al. studied the safety of intramedullary Schwann cell transplantation in 33 patients over the period of 2 years, there were no tumor

Co-transplantation of cells has also been explored. Combined use of olfactory ensheathing cells and Schwann cells enhanced functional recovery [27]. Similarly,

formation or other adverse events recorded [25].

*5.2.2.4 Co-transplantation of multiple cell types*

**144**

Several comparative studies have been carried out to determine the optimum route of administration. Geffner et al. reported administration of BMSCs intravenous, into the spinal canal and into the spinal cord to be safe and feasible. They also demonstrated improved ASIA, Barthel Index. Ashworth and Frenkel scores suggesting improved quality of life in most patients [14]. While intra-arterial transplantation of autologous bone marrow stem cells showed more improvements as compared with that of intravenous route, intravenous transplantation showed better neurological outcome as compared to the site of injury [31–33]. Systemic routes show considerable dilution of cells at various cells like kidneys, liver, spleen and lungs. Several intraspinal approaches like intraparenchymal, intralesional and intramedullary approaches have been explored. Although no serious adverse events were noted; some patients complained of transient increase in paresthesia and muscle cramps. Intraspinal approaches are associated with increased risk of procedure related adverse effect due to invasive nature of the procedure [86–88]. Saito et al. [89], Pal et al. [90] and Kumar et al. [91] reported intrathecal administration to be the optimum route of administration. Although in this approach cells are transplanted away from the lesion area, MRI studies of radiolabeled cells have shown successful homing of cells at the site of injury [92].

### **6. Published clinical results of NeuroGen Brain and Spine Institute**

#### **6.1 Our protocol**

#### *6.1.1 Pre-intervention protocol*

All the patients are thoroughly assessed clinically to rule out presence of active infections, HIV or HBsAg positive status and malignancies. Routine serological tests and chest X-ray are performed to ensure medical fitness. Neuroimaging using functional MRI brain and MRI of spine is performed. Various clinical outcome measures are marked before procedure assessing muscle tone, strength, ambulation and sensations. Granulocyte colony stimulating factor injections are given 48 and 24 h prior to the transplantation to enhance proliferation of cells in the bone marrow.

#### *6.1.2 Intervention protocol*

Our protocol has been designed after careful review of available literature. The protocol for harvesting and transplanting the cells is minimally invasive with no major adverse effects. It consists of three steps.

#### *6.1.2.1 Aspiration of bone marrow*

80–120 ml of bone marrow is aspirated from anterior superior iliac spine (**Figure 3**).

**Figure 3.** *Separation of BMMNCs.*

*6.1.2.2 Separation of BMMNCs*

Density gradient method is used to separate the bone marrow mononuclear cell fraction which is then analyzed under microscope using Trypan blue to check for viability of the mononuclear cells. FACS analysis is used to identify CD34+ cells and viability, cell count and percentage of CD34+ cells are calculated (**Figure 4**).

**Figure 4.** *Injection of BMMNCs.*

#### *6.1.2.3 Injection*

Separated cell fraction is transplanted intrathecally in the space between L4 and L5 lumbar vertebrae by lumbar puncture. This is performed under local anesthesia and sterile conditions in the operation theatre (**Figure 5**).

**147**

*Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury*

required. Patients are regularly followed up every 3 months.

After the cell transplantation a home program of rigorous rehabilitation is prescribed Many of the patients show deficiencies due to prolonged immobility and poor nutrition, therefore nutritional supplements are prescribed as and when

Autologous cells are used to reduce the risk of immune rejection. Bone marrow mononuclear cells (BMMNCs) fraction consists of various cells types including mesenchymal cells, hematopoietic progenitor cells, side population cells, stromal cells and very small embryonic like cells. BMMNCs have demonstrated neurogenic potential and exhibit various paracrine effects like angiogenesis, upregulation of anti-inflammatory cytokines, secreting neurotrophic factors and growth factors, bring about immune modulation and stimulate resident stem cells. While the less invasive systemic routes, lead to dilution of the cells reaching the target organ, due to filtration of cells in various organs like liver, spleen, kidneys and lungs; more invasive routes like intra-spinal routes pose risk of procedure related adverse effect. Intra-thecal delivery therefore ensures delivery of maximum cells at the site of the

It is important that regenerative therapies are complimented with rehabilitative therapies like physiotherapy, occupational therapy, aquatic therapy, speech therapy, psychological intervention and nutritional advice. Regular goal-oriented rehabilitation provides neuroprotective, my protective, anti-inflammatory, antioxidant and neoangiogenic effects on a systemic level which resonate with the paracrine effects of cell therapy and compliment the effect of cell therapy. It is also believed that exercise can contribute to sub-granular and sub-ventricular neurogenesis. Neurogenesis consists of various processes. While differentiation, migration and axonal guidance are independent of physical activity synaptic pruning and plasticity is dependent of physical activity and therefore rehabilitation plays a pivotal role in enhancing this. Therefore, we prescribe a regime of multidisciplinary rehabilita-

This protocol is safe without any major adverse effects. We have so far treated more than 800 patients with spinal cord injury and none of the patients have exhibited any major irreversible adverse effects. A small percentage of patients have shown some minor procedure related adverse effects in SCI which are headache, pain at the site of injection, nausea and vomiting. These are usually self-limiting or

A detailed analysis of chronic thoracolumbar SCI patients who underwent intrathecal administration of autologous bone marrow mononuclear cells followed by neurorehabilitation was conducted [84]. The study sample included 110 thoracolumbar SCI patients. The outcome was recorded at a mean follow up of

injury with relatively reduced risk of procedure related adverse effects.

tion to be followed at home after the cell transplantation (**Figure 2**).

can be completely relieved with minor medical intervention.

*DOI: http://dx.doi.org/10.5772/intechopen.88808*

*6.1.3 Post intervention protocol*

*6.1.4 Rationale for the protocol*

*6.1.4.1 Role of rehabilitation*

*6.1.5 Adverse effects*

**6.2 Published results**

*6.2.1 Thoracolumbar spinal cord injury*

**Figure 5.** *Mechanism of action of stem cells for the treatment of spinal cord injury.*

#### *6.1.3 Post intervention protocol*

*Spinal Cord Injury Therapy*

*6.1.2.2 Separation of BMMNCs*

Density gradient method is used to separate the bone marrow mononuclear cell fraction which is then analyzed under microscope using Trypan blue to check for viability of the mononuclear cells. FACS analysis is used to identify CD34+ cells and

Separated cell fraction is transplanted intrathecally in the space between L4 and L5 lumbar vertebrae by lumbar puncture. This is performed under local anesthesia

and sterile conditions in the operation theatre (**Figure 5**).

*Mechanism of action of stem cells for the treatment of spinal cord injury.*

viability, cell count and percentage of CD34+ cells are calculated (**Figure 4**).

**146**

**Figure 5.**

*6.1.2.3 Injection*

*Injection of BMMNCs.*

**Figure 4.**

**Figure 3.**

*Separation of BMMNCs.*

After the cell transplantation a home program of rigorous rehabilitation is prescribed Many of the patients show deficiencies due to prolonged immobility and poor nutrition, therefore nutritional supplements are prescribed as and when required. Patients are regularly followed up every 3 months.

#### *6.1.4 Rationale for the protocol*

Autologous cells are used to reduce the risk of immune rejection. Bone marrow mononuclear cells (BMMNCs) fraction consists of various cells types including mesenchymal cells, hematopoietic progenitor cells, side population cells, stromal cells and very small embryonic like cells. BMMNCs have demonstrated neurogenic potential and exhibit various paracrine effects like angiogenesis, upregulation of anti-inflammatory cytokines, secreting neurotrophic factors and growth factors, bring about immune modulation and stimulate resident stem cells. While the less invasive systemic routes, lead to dilution of the cells reaching the target organ, due to filtration of cells in various organs like liver, spleen, kidneys and lungs; more invasive routes like intra-spinal routes pose risk of procedure related adverse effect. Intra-thecal delivery therefore ensures delivery of maximum cells at the site of the injury with relatively reduced risk of procedure related adverse effects.

#### *6.1.4.1 Role of rehabilitation*

It is important that regenerative therapies are complimented with rehabilitative therapies like physiotherapy, occupational therapy, aquatic therapy, speech therapy, psychological intervention and nutritional advice. Regular goal-oriented rehabilitation provides neuroprotective, my protective, anti-inflammatory, antioxidant and neoangiogenic effects on a systemic level which resonate with the paracrine effects of cell therapy and compliment the effect of cell therapy. It is also believed that exercise can contribute to sub-granular and sub-ventricular neurogenesis. Neurogenesis consists of various processes. While differentiation, migration and axonal guidance are independent of physical activity synaptic pruning and plasticity is dependent of physical activity and therefore rehabilitation plays a pivotal role in enhancing this. Therefore, we prescribe a regime of multidisciplinary rehabilitation to be followed at home after the cell transplantation (**Figure 2**).

#### *6.1.5 Adverse effects*

This protocol is safe without any major adverse effects. We have so far treated more than 800 patients with spinal cord injury and none of the patients have exhibited any major irreversible adverse effects. A small percentage of patients have shown some minor procedure related adverse effects in SCI which are headache, pain at the site of injection, nausea and vomiting. These are usually self-limiting or can be completely relieved with minor medical intervention.

#### **6.2 Published results**

#### *6.2.1 Thoracolumbar spinal cord injury*

A detailed analysis of chronic thoracolumbar SCI patients who underwent intrathecal administration of autologous bone marrow mononuclear cells followed by neurorehabilitation was conducted [84]. The study sample included 110 thoracolumbar SCI patients. The outcome was recorded at a mean follow up of

2 years ± 1 month. The outcome measures were functional independence measure (FIM) score, American Spinal Injury Association scale (ASIA) and detailed neurological assessment. Data were statistically analyzed using McNemar's Test to establish significance between the change in symptoms and the intervention.

A total of 100 out of 110 (91%) patients showed improvements. Improvement in trunk control was observed in 95.6% cases, bladder management in 33% with respect to shift from indwelling and condom catheter to self-intermittent catheterization, partial sensory recovery in 27% and reduction of spasticity in 26%. All the patients showed improvement in postural hypotension. 38% wheelchair bound patients started walking with assistance. Functionally, 27% showed improved activities of daily living (ADLs) and 53.6% showed a positive change in FIM score. About 10% cases showed a shift in ASIA scale. A statistically significant association of these symptomatic improvements with the cell therapy intervention was established using McNemar's Test. On electrophysiological studies, 2 showed improvement and 1 showed change in functional MRI [79] (**Figure 6**, **Tables 1** and **2**).

#### **Figure 6.**

*Symptomatic improvements in patients with spinal cord injury after stem cell therapy. The X-axis denotes symptoms presented in the patient population and the Y-axis denotes the number of patients. (ADLs activities of daily living) (Tables 1 and 2).*


**149**

**Table 3.**

*using McNemar's test.*

*Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury*

significant clinical and functional outcome (**Figure 7**).

A detailed analysis of chronic cervical SCI patients who underwent intrathecal administration of autologous bone marrow mononuclear cells followed by neurorehabilitation was conducted [85]. This study includes 50 patients of chronic cervical SCI. The outcome was recorded at a mean follow up of 2 years ± 1 month. The outcome measures were functional independence measure (FIM) score, American Spinal Injury Association scale (ASIA) and detailed neurological assessment. Data were statistically analyzed using McNemar's Test to establish significance between the change in symptoms and the intervention. 37 out of 50 (74%) showed improvements. Sensation recovery was observed in 26% cases, improved trunk control in 22.4%, spasticity reduction in 20% and bladder sensation recovery in 14.2%. All the 50 cases had improvement in postural hypotension. 12.24% wheelchair bound patients started walking with assistance. Functionally, 20.4% patients showed improved ADLs and 48% showed a positive change in FIM score. 6% cases showed a shift in ASIA scale. A statistical analysis using McNemar's test established a significant association of these symptoms with the intervention [89]. No major side effects were noted in the duration of 2 years in both the studies. A better outcome was observed in thoracolumbar injury as compared to the cervical injury suggesting that the level of SCI greatly influences the recovery of the patient (**Tables 3**–**5**). Both studies demonstrated statistically

*McNemar's test: table demonstrating the statistical analysis for each symptomatic improvement in cervical SCI* 

*Objective improvements evident on electromyography (A) and functional magnetic resonance imaging* 

*DOI: http://dx.doi.org/10.5772/intechopen.88808*

*6.2.2 Cervical SCI*

*(B) after stem cell therapy in selected patients.*

**Table 2.**

#### **Table 1.**

*Statistical significance for each symptomatic/functional change using McNemar's test.*

*Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.88808*


#### **Table 2.**

*Spinal Cord Injury Therapy*

2 years ± 1 month. The outcome measures were functional independence measure (FIM) score, American Spinal Injury Association scale (ASIA) and detailed neurological assessment. Data were statistically analyzed using McNemar's Test to establish significance between the change in symptoms and the intervention.

A total of 100 out of 110 (91%) patients showed improvements. Improvement in trunk control was observed in 95.6% cases, bladder management in 33% with respect to shift from indwelling and condom catheter to self-intermittent catheterization, partial sensory recovery in 27% and reduction of spasticity in 26%. All the patients showed improvement in postural hypotension. 38% wheelchair bound patients started walking with assistance. Functionally, 27% showed improved activities of daily living (ADLs) and 53.6% showed a positive change in FIM score. About 10% cases showed a shift in ASIA scale. A statistically significant association of these symptomatic improvements with the cell therapy intervention was established using McNemar's Test. On electrophysiological studies, 2 showed improvement and 1 showed change in functional MRI [79] (**Figure 6**, **Tables 1** and **2**).

**148**

**Table 1.**

**Figure 6.**

*activities of daily living) (Tables 1 and 2).*

*Statistical significance for each symptomatic/functional change using McNemar's test.*

*Symptomatic improvements in patients with spinal cord injury after stem cell therapy. The X-axis denotes symptoms presented in the patient population and the Y-axis denotes the number of patients. (ADLs—* *Objective improvements evident on electromyography (A) and functional magnetic resonance imaging (B) after stem cell therapy in selected patients.*

#### *6.2.2 Cervical SCI*

A detailed analysis of chronic cervical SCI patients who underwent intrathecal administration of autologous bone marrow mononuclear cells followed by neurorehabilitation was conducted [85]. This study includes 50 patients of chronic cervical SCI. The outcome was recorded at a mean follow up of 2 years ± 1 month. The outcome measures were functional independence measure (FIM) score, American Spinal Injury Association scale (ASIA) and detailed neurological assessment. Data were statistically analyzed using McNemar's Test to establish significance between the change in symptoms and the intervention. 37 out of 50 (74%) showed improvements. Sensation recovery was observed in 26% cases, improved trunk control in 22.4%, spasticity reduction in 20% and bladder sensation recovery in 14.2%. All the 50 cases had improvement in postural hypotension. 12.24% wheelchair bound patients started walking with assistance. Functionally, 20.4% patients showed improved ADLs and 48% showed a positive change in FIM score. 6% cases showed a shift in ASIA scale. A statistical analysis using McNemar's test established a significant association of these symptoms with the intervention [89]. No major side effects were noted in the duration of 2 years in both the studies. A better outcome was observed in thoracolumbar injury as compared to the cervical injury suggesting that the level of SCI greatly influences the recovery of the patient (**Tables 3**–**5**). Both studies demonstrated statistically significant clinical and functional outcome (**Figure 7**).


#### **Table 3.**

*McNemar's test: table demonstrating the statistical analysis for each symptomatic improvement in cervical SCI using McNemar's test.*


#### **Table 4.**

*Percentage analysis of improvements: table demonstrating a detailed analysis of various factors and the improvements.*


#### **Table 5.**

*Comparison between cervical SCI and thoracolumbar SCI: table comparing the outcome of cell transplantation in cervical SCI and thoracolumbar SCI.*

**Figure 7.**

*Graph demonstrating symptomatic improvements in chronic cervical SCI patients after cell therapy.*

**151**

**Figure 9.**

*Clinical outcome in patients with SCI post cell treatment.*

**6.3 Unpublished data**

**Figure 8.**

*Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury*

A case study of a 32-year-old man with chronic thoracic complete spinal cord injury treated with intrathecal administration of autologous bone marrow mononuclear cells with standard rigorous neurorehabilitation showed improved clinical outcome without any adverse effect [93]. Follow up assessment conducted at 3- and 7-months post treatment showed improvements in motor activities, ambulation, bed mobilities, transfers and bladder management. Spinal cord independence measure (SCIM) improved from 27 to 64/100 and functional improvement measure

Brain functional magnetic resonance imaging (fMRI) shows patterns of cortical activation in response to attempted motor task. In chronic spinal cord injury corticospinal tract neurons undergo retrograde degeneration. Therefore, the activation of the cortical areas is reduced in response to injury. Brain fMRI can thus be used to assess the outcome of the therapy. Post treatment fMRI in these patients showed activation of multiple regions in the sensory and associated areas, which was absent pre-treatment providing evidence for improved neural activation (**Figure 8**).

We analyzed 300 patients with chronic thoracic and cervical spinal cord injury and noted that 96.2% of the patients showed clinical improvements. The improvements were classified as mild, moderate or significant based on how many

*fMRI images showing improved activation of sensorimotor and associated areas post transplantation.*

(FIM) improved from 64 to 83 suggesting significant functional gain.

*DOI: http://dx.doi.org/10.5772/intechopen.88808*

*6.2.3 Objective assessment using neuroimaging*

*Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.88808*

#### *6.2.3 Objective assessment using neuroimaging*

*Spinal Cord Injury Therapy*

**150**

**Figure 7.**

**Table 5.**

**Table 4.**

*improvements.*

*in cervical SCI and thoracolumbar SCI.*

*Comparison between cervical SCI and thoracolumbar SCI: table comparing the outcome of cell transplantation* 

*Percentage analysis of improvements: table demonstrating a detailed analysis of various factors and the* 

*Graph demonstrating symptomatic improvements in chronic cervical SCI patients after cell therapy.*

A case study of a 32-year-old man with chronic thoracic complete spinal cord injury treated with intrathecal administration of autologous bone marrow mononuclear cells with standard rigorous neurorehabilitation showed improved clinical outcome without any adverse effect [93]. Follow up assessment conducted at 3- and 7-months post treatment showed improvements in motor activities, ambulation, bed mobilities, transfers and bladder management. Spinal cord independence measure (SCIM) improved from 27 to 64/100 and functional improvement measure (FIM) improved from 64 to 83 suggesting significant functional gain.

Brain functional magnetic resonance imaging (fMRI) shows patterns of cortical activation in response to attempted motor task. In chronic spinal cord injury corticospinal tract neurons undergo retrograde degeneration. Therefore, the activation of the cortical areas is reduced in response to injury. Brain fMRI can thus be used to assess the outcome of the therapy. Post treatment fMRI in these patients showed activation of multiple regions in the sensory and associated areas, which was absent pre-treatment providing evidence for improved neural activation (**Figure 8**).

#### **6.3 Unpublished data**

We analyzed 300 patients with chronic thoracic and cervical spinal cord injury and noted that 96.2% of the patients showed clinical improvements. The improvements were classified as mild, moderate or significant based on how many

**Figure 9.** *Clinical outcome in patients with SCI post cell treatment.*

#### *Spinal Cord Injury Therapy*

symptoms showed improvements (3 symptoms—mild improvement, 4–6 symptoms—moderate improvement and more than 6 symptoms—significant improvement) majority of the patients showed moderate improvements (**Figure 9**).

Symptomatic analysis of these patients showed reduction in spasticity, sensory motor recovery, recovery of bladder sensation, increased functional independence while performing ADLS, improved balance and ambulation (**Figure 10**).

**Figure 10.** *Symptomatic improvements in patients with SCI post cell therapy.*

#### **7. Limitations and future directions**

Currently little objective evidence is available to show the regeneration of spinal cord and increased connectivity of spinal tracts. Enhanced radio imaging tools are required for better visualization of the outcome.

Although various cells and routes of administration have been explored an optimum cell type and route of administration remain elusive due to heterogeneity of research protocols, sample size, treatment regimen and lack of multi-centric high-quality studies. Comparison between different protocols is required to be carried out using rigorous methodology to identify an optimum clinical protocol that yields maximum recovery.

It takes about 6 months to generate iPSCs from autologous somatic cells and almost a year to test the safety of cells for transplantation, this combines with risks associated with iPSCs including genetic and epigenetic abnormalities, tumorigenicity and immunogenicity related to cell trans-plantation has prevented their clinical translation so far [94–96]. Advent in iPSC technology and its clinical translation is the future direction for medical sciences.

#### **8. Conclusion**

Spinal cord injury is a devastating and disabling neurological disorder with no definite cure. Several treatment strategies are being explored for improved clinical

**153**

**Author details**

improvement.

Alok Sharma, Hemangi Sane, Nandini Gokulchandran, Prerna Badhe,

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: amrutap.neurogen@gmail.com

Amruta Paranjape\*, Pooja Kulkarni and Vivek Nair NeuroGen Brain and Spine Institute, Navi Mumbai, India

provided the original work is properly cited.

*Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury*

outcome especially for chronic injuries. Stem cell therapy is a promising treatment modality. Use of stem cells for the treatment of spinal cord injury is safe and improves neurological as well as functional outcome. With the available evidence autologous multipotent stem cells like bone marrow derived mononuclear cells show positive clinical outcomes with no adverse effects. Factors like level of injury, time since injury, concomitant disorders and rigor of neurorehabilitation can influ-

Lot of evidence has been generated over the last decade demonstrating the benefits of using stem cells to improve sensory-motor function, functional independence of the patients and quality of life. Stem cell therapy helps to reduce the complications post spinal cord injury due to their positive effect. Although it does not provide a complete cure at the moment, it certainly holds the potential to improve functional independence and quality of life. It is important to supplement stem cell therapy with current treatments and rehabilitation for optimum clinical

*DOI: http://dx.doi.org/10.5772/intechopen.88808*

ence the outcome of the cell treatment.

#### *Neuroregenerative-Rehabilitative Therapy for Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.88808*

*Spinal Cord Injury Therapy*

**7. Limitations and future directions**

the future direction for medical sciences.

yields maximum recovery.

required for better visualization of the outcome.

*Symptomatic improvements in patients with SCI post cell therapy.*

(**Figure 10**).

**Figure 10.**

symptoms showed improvements (3 symptoms—mild improvement, 4–6 symptoms—moderate improvement and more than 6 symptoms—significant improvement) majority of the patients showed moderate improvements (**Figure 9**). Symptomatic analysis of these patients showed reduction in spasticity, sensory motor recovery, recovery of bladder sensation, increased functional independence while performing ADLS, improved balance and ambulation

Currently little objective evidence is available to show the regeneration of spinal cord and increased connectivity of spinal tracts. Enhanced radio imaging tools are

Although various cells and routes of administration have been explored an optimum cell type and route of administration remain elusive due to heterogeneity of research protocols, sample size, treatment regimen and lack of multi-centric high-quality studies. Comparison between different protocols is required to be carried out using rigorous methodology to identify an optimum clinical protocol that

It takes about 6 months to generate iPSCs from autologous somatic cells and almost a year to test the safety of cells for transplantation, this combines with risks associated with iPSCs including genetic and epigenetic abnormalities, tumorigenicity and immunogenicity related to cell trans-plantation has prevented their clinical translation so far [94–96]. Advent in iPSC technology and its clinical translation is

Spinal cord injury is a devastating and disabling neurological disorder with no definite cure. Several treatment strategies are being explored for improved clinical

**152**

**8. Conclusion**

outcome especially for chronic injuries. Stem cell therapy is a promising treatment modality. Use of stem cells for the treatment of spinal cord injury is safe and improves neurological as well as functional outcome. With the available evidence autologous multipotent stem cells like bone marrow derived mononuclear cells show positive clinical outcomes with no adverse effects. Factors like level of injury, time since injury, concomitant disorders and rigor of neurorehabilitation can influence the outcome of the cell treatment.

Lot of evidence has been generated over the last decade demonstrating the benefits of using stem cells to improve sensory-motor function, functional independence of the patients and quality of life. Stem cell therapy helps to reduce the complications post spinal cord injury due to their positive effect. Although it does not provide a complete cure at the moment, it certainly holds the potential to improve functional independence and quality of life. It is important to supplement stem cell therapy with current treatments and rehabilitation for optimum clinical improvement.

#### **Author details**

Alok Sharma, Hemangi Sane, Nandini Gokulchandran, Prerna Badhe, Amruta Paranjape\*, Pooja Kulkarni and Vivek Nair NeuroGen Brain and Spine Institute, Navi Mumbai, India

\*Address all correspondence to: amrutap.neurogen@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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with physical therapy induces functional improvement in chronic spinal cord injury patients. Cell Transplantation. 2014;**23**(6):729-745

2004;**24**(10):1207-1209

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[77] Jarocha D, Milczarek O, Kawecki Z, Wendrychowicz A, Kwiatkowski S, Majka M. Preliminary study of autologous

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[80] Deda H, Inci MC, Kürekçi AE, Kayihan K, Ozgün E, Ustünsoy GE, et al. Treatment of chronic spinal cord injured patients with autologous bone marrow-derived hematopoietic stem cell transplantation: 1-year follow-up. Cytotherapy. 2008;**10**(6):565-574

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[61] Salewski RP, Mitchell RA, Shen C, Fehlings MG. Transplantation of neural of human induced pluripotent stem cell-derived long-term self-renewing neuroepithelial-like stem cells. Stem

[69] Kobayashi Y, Okada Y, Itakura G, Iwai H, Nishimura S, Yasuda A, et al. Pre-evaluated safe human iPSCderived neural stem cells promote functional recovery after spinal cord injury in common marmoset without tumorigenicity. PLoS ONE.

[70] Nutt SE, Chang EA, Suhr ST, Schlosser LO, Mondello SE, Moritz CT, et al. Caudalized human iPSC-derived neural progenitor cells produce neurons and glia but fail to restore function in an early chronic spinal cord injury model. Experimental Neurology. 2013;**248**:491-503

[71] Amemori T, Ruzicka J,

& Therapy. 2015;**6**:257

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2003;**57**(9):428-433

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[74] Feron F, Perry C, Cochrane J, Licina P, Nowitzke A, Urquhart S, et al. Autologous olfactory ensheathing cell transplantation in human spinal cord injury. Brain. 2005;**128**(12):2951-2960

[72] Hayashi K, Hashimoto M,

Romanyuk N, Jhanwar-Uniyal M, Sykova E, Jendelova P. Comparison of intraspinal and intrathecal implantation of induced pluripotent stem cell-derived neural precursors for the treatment of spinal cord injury in rats. Stem Cell Research

Koda M, Naito AT, Murata A, Okawa A et al. Increase of sensitivity to mechanical stimulus after transplantation of murine induced pluripotent stem cell-derived astro astrocytes in a rat spinal cord injury model. Journal of Neurosurgery Spine.

Cells. 2012;**30**:1163-1173

2012;**7**:e52787

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[63] Zhang YW, Denham J, Thies RS. Oligodendrocyte progenitor cells derived from human embryonic stem cells express neurotrophic factors. Stem

[64] Tetzlaff W, Okon EB, Karimi-Abdolrezaee S, Hill CE, Sparling JS, Plemel JR, et al. A systematic review of cellular transplantation therapies for spinal cord injury. Journal of Neurotrauma. 2011;**28**:1611-1682

[65] Salewski RP, Mitchell RA, Li L, Shen C, Milekovskaia M, Nagy A, et al. Transplantation of induced pluripotent stem cell-derived neural stem cells mediate functional recovery following thoracic spinal cord injury through remyelination of axons. Stem Cells Translational Medicine. 2015;**4**:743-754

[66] Shende P, Subedi M.

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of induced pluripotent stem cell technologies in spinal cord injury. Journal of Neurochemistry.

embryonic stem cell-derived oligodendrocyte progenitors for the treatment of spinal cord injury. Transplant Immunology.

2005;**15**:131-142

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stem cells clonally derived from

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[77] Jarocha D, Milczarek O, Kawecki Z, Wendrychowicz A, Kwiatkowski S, Majka M. Preliminary study of autologous bone marrow nucleated cells transplantation in children with spinal cord injury. Stem Cells Translational Medicine. Mar 2014;**3**(3):395-404

[78] Ha Y, Yoon SH, Park SR. Treatment of complete spinal cord injury patients receiving autologous bone marrow cell transplantation and bone marrow stimulation with granulocyte macrophage-colony stimulating factor—Report of three cases. Journal of Korean Neurosurgical Association. 2004;**35**:459-464

[79] Park HC, Shim YS, Ha Y, et al. Treatment of complete spinal cord injury patients by autologous bone marrow cell transplantation and Administration of granulocytemacrophage colony stimulating factor. Tissue Engineering. 2005;**11**(5-6):913-922

[80] Deda H, Inci MC, Kürekçi AE, Kayihan K, Ozgün E, Ustünsoy GE, et al. Treatment of chronic spinal cord injured patients with autologous bone marrow-derived hematopoietic stem cell transplantation: 1-year follow-up. Cytotherapy. 2008;**10**(6):565-574

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[82] Dai G, Liu X, Zhang Z, Yang Z, Dai Y, Xu R. Transplantation of autologous bone marrow mesenchymal stem cells in the treatment of complete and chronic cervical spinal cord injury. Brain Research. 2013;**1533**:73-79

[83] Jiang PC, Xiong WP, Wang G, Ma C, Yao WQ, Kendell SF, et al. A clinical trial report of autologous bone marrow-derived mesenchymal stem cell transplantation in patients with spinal cord injury. Experimental and Therapeutic Medicine. 2013;**6**(1):140-146

[84] Sharma A, Gokulchandran N, Sane H, Badhe P, Kulkarni P, Lohia M, et al. Detailed analysis of the clinical effects of cell therapy for thoracolumbar spinal cord injury: An original study. Journal of Neurorestoratology. 2013;**1**:13-22

[85] Sharma A, Sane H, Gokulchandran N, Kulkarni P, Thomas N, et al. Role of autologous bone marrow mononuclear cells in chronic cervical spinal cord injury—A Long-term follow up study. Journal of Neurological Disorders. 2013;**1**:138

[86] Abdelaziz OS. Feasibility, safety, and efficacy of directly transplanting autologous adult bone marrow stem cells in patients with chronic traumatic dorsal cord injury: A pilot clinical study. Neurosurgery Quarterly. 2010;**20**(3):216-226

[87] Saberi H, Moshayedi P, Aghayan H-R, et al. Treatment of chronic thoracic spinal cord injury patients with autologous Schwann cell transplantation: An interim report on safety considerations and possible outcomes. Neuroscience Letters. 2008;**443**(1):46-50

[88] Park JH, Kim DY, Sung IY, et al. Long-term results of spinal cord injury therapy using mesenchymal stem cells derived from bone marrow in humans. Neurosurgery. 2012;**70**(5):1238-1247

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**160**

### *Edited by Antonio Ibarra, Elisa García-Vences and Gabriel Guízar-Sahagún*

Spinal cord injury (SCI) is one of the main pathologies causing significant loss of neurological function. Therefore, a variety of pharmacological and nonpharmacological therapies are the aims of several studies. To provide the best care, it is important to know and understand the therapeutic approaches that have shown important progress in this topic.

This book contains eight chapters that are divided into three sections: Introduction, Pharmacological Therapies, and Non-Pharmacological Therapies. The authors of the chapters deal with the pathophysiology of SCI, the effect of antioxidant and immunosuppressive agents, stem cell-based therapies, the use of cultured cells for transference or transplantation, and the application of non-invasive modalities (transcutaneous electrical spinal cord stimulation, etc.) for SCI rehabilitation.

Published in London, UK © 2019 IntechOpen © wildpixel / iStock

Spinal Cord Injury Therapy

Spinal Cord Injury Therapy

*Edited by Antonio Ibarra,* 

*Elisa García-Vences and Gabriel Guízar-Sahagún*