**4.4 Bone marrow aspiration anatomical sites**

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


**13**

paragraph.

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

source of MSCs [10]. These findings were confirmed in a clinical study, where MSCs were found in BM acquired from the metaphysis of the distal femur, the proximal tibia, and iliac crest. A similar MSC immunophenotype and differentiation potential (into the bone, fat, and cartilage) were seen in BMA from all sites. However, in their study the concentration of MSCs in the iliac crest was significantly higher than in samples from the distal femur and proximal tibia. More specifically, the literature indicates high yields of BM-MSCs acquired from the posterior superior iliac spine (PSIS) [50, 54]. Noteworthy, the group of Narbona-Carceles commented on the relative easiness and safety of lower extremity aspiration techniques [55].

The literature pronounces BMAs as a heterogenous mix of cells, referring in most instances to MSCs, HSCs, and mononuclear cells. Platelets, megakaryocytes,

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

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

and RBCs are seldomly mentioned, let be subject to BM research [24].

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

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

**5.1 Hematopoietic stem cells**

processes [56].

*5.1.1 Hematopoiesis*

#### **Table 2.**

*Bone marrow aspiration sites in humans.*

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

source of MSCs [10]. These findings were confirmed in a clinical study, where MSCs were found in BM acquired from the metaphysis of the distal femur, the proximal tibia, and iliac crest. A similar MSC immunophenotype and differentiation potential (into the bone, fat, and cartilage) were seen in BMA from all sites. However, in their study the concentration of MSCs in the iliac crest was significantly higher than in samples from the distal femur and proximal tibia. More specifically, the literature indicates high yields of BM-MSCs acquired from the posterior superior iliac spine (PSIS) [50, 54]. Noteworthy, the group of Narbona-Carceles commented on the relative easiness and safety of lower extremity aspiration techniques [55].
