**5. Major type of cells in bone marrow**

The literature pronounces BMAs as a heterogenous mix of cells, referring in most instances to MSCs, HSCs, and mononuclear cells. Platelets, megakaryocytes, and RBCs are seldomly mentioned, let be subject to BM research [24].

### **5.1 Hematopoietic stem cells**

*Regenerative Medicine*

post-procedural pain.

**Figure 5.**

*G. Flanagan II).*

Anterior superior iliac spine (ASIS) Posterior superior iliac spine (PSIS)

*Bone marrow aspiration sites in humans.*

Proximal tibia Distal tibia Distal femur Proximal humerus Vertebral body Calcaneus Sternum

**4.4 Bone marrow aspiration anatomical sites**

techniques, the parallel approach technique allows for a safe deeper marrow penetration. However, at all times, regardless of the approach, avoid increased manipulation and tissue trauma using the sharp trocar, as this will increase the risk for neurovascular injury, bleeding, tearing of lateral gluteal muscle origins, and

*Fluoroscopy imaging of the PSIS. General prone position of the patient on a fluoroscopic table for BMA. The* parallel fluoroscopic approach *results in viewing down the PSIS table, at a 25° contralateral oblique beam position. This results in a classic view of the "teardrop," referring to the outline of the medial and lateral borders, as shown in the monitor. The tip of a needle (black circle), in the numbed skin, is marking the entry site of the bone marrow trocar to be placed in the marrow cavity, while the physician is on the ipsilateral side of the fluoroscope, viewing the correct position on the monitor (red circle) (courtesy of* 

As MSCs represent a small population of BM cells [7], it is of critical importance to choose a BMA site that will yield the most MSCs. BM is relatively easy to harvest, largely available, and dispensable. Obviously, it is important that the BMA procedure is performed impeccably to obtain an optimal quality of viable BM tissue [5, 53]. In humans, the most common anatomical location to obtain BM is the iliac crest, but other BMA sites have been utilized (**Table 2**). Recently, McDaniel and co-workers, using a porcine model, reported that all studied anatomical bone marrow harvesting locations contained MSCs but the iliac crest was the most abundant

**12**

**Table 2.**

The major function of the bone marrow is to generate blood cells. In particular in adults, marrow-derived HSCs are the principle cells of origin of all mature hematopoietic cell phenotypes. HSCs are adult stem cells with extensive self-renewal capabilities and are able to differentiate into specialized blood cells with key roles in some biological activities: control homeostasis balance, immune functions, and response to microorganisms and inflammation. Most HSCs are in a quiescent state within the BM niches. They respond to the signals after the balance of blood cells, or HSC pool, is disturbed from either intrinsic or extrinsic stimuli and signaling processes [56].

### *5.1.1 Hematopoiesis*

Hematopoiesis—the process by which mature blood cells are formed—has been studied intensely for over a century. The vast majority of hematopoiesis occurs in the bone marrow where it must balance enormous production needs. More than 500 billion blood cells are produced every day, with precise regulation of the number of each blood cell type released in the circulation [57]. Hematopoiesis is considered as a pyramidal/hierarchical process with cells of greatest maturation potential or primitiveness sitting at the top of the hierarchy and cells that have undergone terminal differentiation at the bottom. Terminally differentiated blood cells are classified into one of the two major lineages: those derived from myeloid lineages and from lymphoid progenitors. Myeloid cells include erythrocytes, platelets, and cells responsible for cellular immunity, such as macrophages and granulocytes (**Figure 6**). Cells derived from lymphoid progenitors are major participants in coordinating humeral and cellular immunity. Experimental data suggested that HSCs differentiate into hematopoietic progenitor cells that are capable of exponential proliferation as well as continuing the process of differentiation. Alternatively, HSCs are capable of self-replicating activities, which may give rise to one or two identical daughter cells. As a result, HSC activity must be tightly regulated to meet physiologic demands but also to protect HSCs from oncogenic, physical, and chemical damage to occur. The site or physical location that regulates self-renewal, proliferation, and differentiation of HSCs has been discussed in the HSC niche paragraph.

#### **Figure 6.**

*Hematopoietic stem cell hierarchy. Self-renewing HSCs give rise to common myeloid progenitors and common lymphoid progenitors, producing different types of progenitor cells and ultimately fully differentiated cells. The myeloid progenitors produce granulocyte-macrophage progenitors giving rise to differentiated leukocytic cells and mast cells. The megakaryocyte/erythrocyte progenitors give rise to megakaryocytes, platelets, and erythrocytes. The lymphoid progenitors differentiate ultimately in lymphocytic cell variances.*

#### *5.1.2 HSC and angiogenesis*

Emerging evidence suggests that BM-derived endothelial cells and HSCs, including their progenitor cells, contribute to tissue vascularization. HSCs deliver specific angiogenetic factors, facilitating the incorporation of endothelial progenitor cells into newly sprouting vessels. Several clinical studies have shown that BM-derived cells contribute to neo-angiogenesis during wound healing [44], critical limb ischemia [45], and postmyocardial infarction [58]. This should contribute to the clinical discussion of the value of BM-derived HSC and vascular progenitor as they are able to contribute to tissue restoration by accelerating tissue vascularization and regeneration [15, 59].

#### **5.2 Mesenchymal stem cells**

In recent decades, physicians performing regenerative medicine applications have been more interested in the potential of BM-MSCs than of HSCs. Imaginable reasons for this particular interest in MSCs might be recent published expert opinions: the *in vivo* ability of MSCs to migrate into tissues, their sturdy regenerative and reparative properties, and the MSC-mediated immunomodulatory actions.

**15**

**Figure 7.**

*Corporation, Fort Myers, FL, USA).*

*The Rationale of Autologously Prepared Bone Marrow Aspirate Concentrate for use…*

These typical characteristics and particular mode of actions enable conceivable BM cell-based treatment options [60, 61]. In particular, MSCs do not express significant histocompatibility complexes and immune-stimulating molecules, leading to graft rejection. Likewise, a rapid development in clinical outcome reporting, with a better understanding of BM tissue molecular biology, improved bone marrow aspiration techniques and, at POC BM concentration and preparation methods, has increased the interest and demand for autologous BM stem and progenitor cell

An effective BM-MSC injection is reliant on the performance of the marrow aspiration procedure, minimizing cellular trauma, while maximizing cellular yields and simultaneously avoiding peripheral RBC infiltration [62]. BM aspiration procedures, and not diagnostics, are routinely performed to collect bone marrow tissue to be processed using dedicated BM-MSC concentration kits for regenerative medicine applications. Kits may include a harvesting needle system and/or BM concentration device (**Figure 7**). These at POC MSC isolation techniques are a streamlined method to concentrate marrow cells, including MSCs, HSCs, and progenitor cells. These MSC centrifugation procedures demand less time and attention than laboratory preparation and culturing methodologies which are technically demanding. Double-spin centrifugation protocols create a layered BMC buffy coat stratum, based on different centrifugal forces that accomplish density cellular separation, as a result of the specific cellular gravity of the individual marrow components, as shown in **Figure 8**. Furthermore, BMA concentration-based technologies provide an economic and clinical/patient advantage when compared

*Bone marrow preparation essential components. In bone marrow concentration and preparation kits, the foremost components are a bone marrow harvesting needle and a concentration device (courtesy of EmCyte* 

*DOI: http://dx.doi.org/10.5772/intechopen.91310*

*5.2.1 MSC isolation procedure from bone marrow aspirates*

therapies.

to the culturing technologies.

*The Rationale of Autologously Prepared Bone Marrow Aspirate Concentrate for use… DOI: http://dx.doi.org/10.5772/intechopen.91310*

These typical characteristics and particular mode of actions enable conceivable BM cell-based treatment options [60, 61]. In particular, MSCs do not express significant histocompatibility complexes and immune-stimulating molecules, leading to graft rejection. Likewise, a rapid development in clinical outcome reporting, with a better understanding of BM tissue molecular biology, improved bone marrow aspiration techniques and, at POC BM concentration and preparation methods, has increased the interest and demand for autologous BM stem and progenitor cell therapies.
