**5. MSCs in the clinic**

The promising results of MSCs in preclinical studies encouraged their use in humans; however, the results obtained in the clinical trials still remain controversial

#### *Mesenchymal Stem Cells for Clinical Use after Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.91839*

and do not replicate what was previously reported in experimental animal studies. In this section we will review the results obtained from the main clinical trials involving MSC transplantation as well as their type of application, properties, limitations, and future directions.

Most of the first clinical studies describing reporting the application of MSCs were focused on describing the transplantation technique, the safety, and the evidence of any adverse reactions. Moviglia et al. conducted a preliminary report that described the intra-arterial administration of bone marrow (BM) MSCs (BM-MSCs) in two patients with chronic SCI in combination with neurorehabilitation programs. Patient 1 presented paraplegia at the eighth thoracic vertebra (T8) with a sensitive level corresponding to T6, while patient 2 presented severe quadriplegia with a lesion that extended from his third to fifth cervical vertebrae (C3–C5) and a sensitive level corresponding to C2. After 6 months, both patients improved their motor and sensory functions without having any secondary effects. The motor level of patient 1 now corresponds to his first sacral metamere (S1) and his sensitive level to the fourth sacral metamere (S4), while sensory and motor functions from patient 2 reached T1–T2 [74]. Similar results, in terms of the safety, were obtained in a pilot study conducted by Pal et al., where 30 patients with complete cervical or thoracic SCI (ASIA scale rating system class A) received intrathecal injections of MSCs via lumbar puncture and none of them presented any adverse effects in the following 1–3 years [75]. However, only the patients with less than 6 months of thoracic-level injury experienced improvement in their quality of life and degree of independence according to Barthel's Index (BI). Despite these improvements, there was no significant change in the ASIA score and in magnetic resonance imaging (MRI). Furthermore, due to the homing abilities of the MSCs, Ra et al*.* also tested the toxicity, tumorigenicity, and therapeutic potential of the intravenous administration of adipose tissue-derived MSCs in eight patients with more than 12 months of SCI. After 3 months the therapy demonstrated to be safe and not promoting tumor growth [76]. In addition, this study described limited motor recovery where only one patient with ASIA A demonstrated improvement to ASIA grade C. Lastly, other studies have also demonstrated the safety and lack of evidence of any severe adverse reactions with the intrathecal administration of MSCs [77, 78].

Moving forward, Sykova et al. conducted a nonrandomized phase I/phase II clinical trial comparing the functional improvement and safety of intra-arterial versus intravenous administration of BM-MSCs in 20 patients with SCI at the cervical or thoracic level. The clinical characterization described 15 patients with ASIA grade A and 5 patients with ASIA grade B (incomplete SCI). Both intraarterial group (n=7) and the intravenous group (n=13) contained patients with acute and chronic phases of SCI. The study found significant functional improvements (motor and sensory) in five acute patients and only in one chronic patient. In the intra-arterial group, all four subacute patients exhibited a significant improvement in their ASIA score or Frankel score as well as a marked recovery of motor and somatosensory evoked potentials (MEPs and SEPs). However, in the intravenous group, only one patient demonstrated an improved ASIA score as well as electrophysiology results. Interestingly most of the patients who had functional improvements received the administration of the MSCs close to the injury site suggesting that the administration route through the vertebral artery or into the cerebrospinal fluid might lead to the best outcome. This study also describes that 3–4 weeks after the injury appears to be the best therapeutic window to administer the cells [79]. These results are also supported by another study carried out by Park et al*.* where they showed improved motor and sensory function in 5 out of 6 patients who received intraspinal implantation of BM-MSCs 7 days post-injury in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF)

[80]. Four patients demonstrated a significant improvement in their American Spinal Injury Association Impairment Scale (AIS) grades from A to C, while one patient improved to AIS B from A. Lastly this study also describes those 3–4 weeks after the injury appears to be the best therapeutic window to administer the cells [79].

As many studies supported the safety of this therapy, more scientists focused on comparing and trying to find different types of MSC transplantation. Geffner et al*.* reported eight thoracic SCI cases (four acute and four chronic) with the administration of BM-MSCs through many different administration routes such as intravenous, intraspinal, and directly into the spinal canal in order to assure that the cells will reach their target. Over the course of 2 years, patients showed significant improvements in their quality of life measured by the BI score as well as certain motor recovery measured by the ASIA, Ashworth, and Frankel scores. All four patients of the acute group experienced an improvement in the ASIA score from A to C, while chronic patients had a lesser recovery improving from an ASIA score of B–C to C–D. Improvement of bladder control was the most important aspect in augmenting their quality of life; however, there were also many other important motor improvements, which cannot be correctly represented in the ASIA score [81]. In addition, other studies furtherly support the therapeutic potential of MSCs in improving the urinary functions of SCI patients which majorly contributes to increasing their self-care ability [82, 83]. This study also demonstrated the feasibility and safety of multiple administration routes. Moreover, the study conducted by Jeon et al. discussed the effectiveness of the intraspinal application of BM-MSCs in 10 patients with complete cervical SCI. After 6 months 6 patients demonstrated motor improvements in the upper limbs by measuring electrophysiological parameters (electromyography, nerve conduction velocity, SEP, MEP) as well as morphological changes described by magnetic resonance imaging (MRI) at the site of the lesion. In addition, three out of those six patients exhibited a significant increase in the performance of daily tasks. However, the ASIA/Frankel motor grade remained the same and did not reflect these motor improvements. This study also reported the absence of any major adverse effect or neoplasm growth over the course of 3 years, furtherly supporting the safety of this therapy [84].

Karamouzian et al*.* conducted one of the first studies to introduce a control group in the field of MSCs and SCI. This nonrandomized clinical trial discussed their therapeutic potential by comparing the outcome of 11 patients (7 males and 4 females with mean age of 33.3 ± 8.9 years) with complete subacute SCI who received BM-MSC transplantation via lumbar puncture with a control group (n=20). Five patients in the study group and 12 patients in the control group presented spinal fracture at T12 and L1 levels, while the remaining patients presented a lesion between T1 and T11. After almost 3 years of follow-up, five patients of the experimental group and three patients of the control group exhibited noticeable recovery (a two-grade improvement from baseline, i.e., from ASIA A to C); however, the results were statistically borderline, and there is no clear evidence of the therapeutic potential of these MSCs [85]. In a similar study, Dai et al*.* discussed the effectiveness of BM-MSCs in complete and chronic SCI. This study randomly assigned 40 patients with complete and chronic SCI into a treatment group (n=20) and a control group (n=20). After 6 months of follow-up, 50% of the treatment group demonstrated significant motor recovery as well as an improvement in ASIA score and in electrophysiological examinations. In addition, most of the patients in the treatment group exhibited a significant clinical improvement in terms of the amount of residual urinary volume, pinprick sensory, and light touch, while the control group did not exhibit any significant motor or sensorial improvements [82]. Both of these studies suggest that BM-MSCs might help improve neurological function

#### *Mesenchymal Stem Cells for Clinical Use after Spinal Cord Injury DOI: http://dx.doi.org/10.5772/intechopen.91839*

in complete and chronic SCI, and they present no evidence of any severe complications or major adverse events in any of the patients.

Although stem cell therapy has demonstrated that they possess the therapeutic potential to be combined with neurorehabilitation, Cheng et al. analyzed the effect of UC-MSCs in comparison with neurorehabilitation and self- healing in 34 patients with thoracolumbar SCI and AIS A grading. Patients were divided into three groups: the UC-MSC treatment group, the rehabilitation group, and the control group. After 6 months around 70% of the patients in the treatment group experienced a significant motor recovery and noticeable improvement in muscle tension and self-care ability which involves an increase in the strength of the abdomen, waist, and lower limbs. Meanwhile, only 36% of the patients treated with neurorehabilitation exhibited certain improvements in these aspects, and the control group showed no significant changes in motor recovery, sensation, or self-care ability. In terms of bladder functions, the treatment group showed a decrease in residual urinary volume and maximum detrusor pressure as well as an increase in bladder capacity and urinary flow in comparison with the other two groups [86]. Later on, El-Kheir et al. decided to compare the use of BM-MSCs in combination with physical therapy with the use of physical therapy alone in 70 chronic cervical and thoracic SCI patients (25 AIS A and 45 AIS B) in a phase I/phase II controlled single-blind clinical trial. After 18 months of follow-up, 46% of the stem cell therapy group exhibited functional improvement and an increase in both motor and dermatome scores by the ASIA and AIS scoring as well as a significant improvement in motor, pinprick, and light touch sensory and functional independence scores over the treated group with physical therapy alone [87]. These studies suggest that BM-MSCs can be combined with additional therapies in order to boost their therapeutic potential.

Equally important, El-Kheir et al. described that thoracic SCI patients with smaller lesions and lower duration of the injury had a higher increase of functional improvement in comparison with patients with cervical SCI [87]. Similar results were obtained in the study carried out by Mendonca et al. which demonstrated a statistically significant correlation between the neurological recovery and both the level and size of the injury in patients with chronic (>6 months) thoracic or lumbar SCI. In addition, after the intra-lesion administration of BM-MSCs, all of the 14 patients demonstrated certain improvements in tactile sensitivity and 8 subjects showed some improvement in the motor functions of the lower limbs reflected by an improvement in their ASIA grading from A to B or C [88].

As the amount of beneficial but limited results grew, the amount of the transplanted MSCs and number of administrations started to gain attention. Vaquero et al*.* conducted a series of clinical trials involving different numbers of MSC administrations in SCI. The first study consisted of a clinical trial involving 12 patients with complete (ASIA A) and chronic thoracic SCI who received two separate transplantations of BM-MSCs in the subarachnoid space. All patients exhibited certain degree of sensorial improvement (pinprick sensitivity and light touch sensitivity), and 50% of the patients showed motor activity below the injury level according to clinical and neurophysiological studies (SEPs and MEPs). More than 30% of the patients improved their AIS A score from A to B or C, and 83% of the patients presented improvement in urodynamic function including possibility of voluntary micturition (5 patients), increased bladder capacity at filling in (8 patients), decreased detrusor pressure at bladder filling in (9 patients), and increased bladder compliance (10 patients). In addition, they hypothesize that the clinical improvement was dose-dependent [89]. The second study consisted of 10 patients with incomplete (ASIA B and C) cervical, thoracic, and lumbar SCI who received 4 subarachnoid administrations of MSCs. Besides the variable degree of sensorial and motor improvement, after 12 months of the first dosage almost all the patients showed noticeable improvements in bowel and bladder control as well as evidence of muscle reinnervation in electromyographic studies. Furthermore, half of them demonstrated a decrease in spasticity by the Penn and Ashworth scales, and after the third dosage of MSCs, all the patients exhibited an increase in the values of neurotrophic factors such as brain-derived neurotrophic factor (BDNF), glialderived neurotrophic factor (GDNF), ciliary neurotrophic factor (CNF), and neurotrophin 3 (NT-3) and neurotrophin 4 (NT-4). However, the difference with the basal mean concentration was not statistically significant [90]. Lastly, their third study consisted of a phase II clinical trial with the administration of three intrathecal injections of MSCs in nine patients with chronic SCI. However, this time 44.4% of the patients demonstrated important improvements in voluntary muscle contraction, motor power, spasm, spasticity, neuropathic pain, and sexual function (IANR-SCIFRS scale) along with evidence of muscle reinnervation. In addition, more than half of the patients showed improved somatosensory and motor evoked potentials [91]. Taken all together, Vaquero and colleagues demonstrate that the subarachnoid administration of MSCs is a safe procedure and that the clinical improvement may increase in a dose-dependent manner. These results were furtherly supported by a study carried out by Oh et al. where a single intramedullary administration of MSC in 16 patients with chronic SCI ASIA B demonstrated very limited therapeutic efficacy. Only two patients demonstrated enhanced motor recovery [92].
