**Abstract**

Autologously prepared bone marrow aspirate concentrates, have the potential to play an adjunctive role in various patient pathologies that have not been able to heal with conventional treatment modalities. The use of bone marrow aspirate (BMA) and concentrates in regenerative medicine treatment plans and clinical applications is based on the fact that bone marrow cells, including progenitor and nucleated cells, platelets, and other cytokines, support in tissue healing and tissue regenerative processes. The use of concentrated BMA cells focuses primarily on mesenchymal stem cells (MSCs), with the ability to self-renew and differentiate into multiple cell types. Concentrated bone marrow cells can be retrieved from harvested BMA and ensuing minimal manipulative cell processing techniques, executed at point of care (POC). The application of bone marrow biological therapies may offer solutions in musculoskeletal pathologies, spinal disorders, chronic wound care, and critical limb ischemia (CLI), to effectively change the local microenvironment to support in tissue healing and facilitate tissue regeneration. This chapter will address the cellular content of bone marrow tissue, harvesting and preparation techniques, and discuss the biological characteristics of individual marrow cells, their inter-connectivity, and deliberate on the effects of BMA concentration.

**Keywords:** regenerative medicine, bone marrow aspiration, niche microenvironment, bone marrow concentrate, centrifugation, hematopoietic stem cells, mesenchymal stem cells, differentiation, immunomodulation

#### **1. Introduction**

The objectives of regenerative medicine applications are to support the body to form new functional tissues to replace degenerative or defective ones and to provide therapeutic treatment for conditions where conventional therapies are inadequate. The human body has an endogenous system of regeneration through stem cells,

as they are found almost in every type of tissue. Regenerative medicine treatment options using autologous stem cells can be safely executed by well-trained physicians at point of care (POC). This review is not meant to be exhaustive, but our aims are to shed light on the bone marrow progenitor and stem cell mechanisms and highlight present and future applications of autologous bone marrow-derived stem cells in this exciting new regenerative medicine discipline.

In this chapter a definition is provided on embryotic and non-embryotic stem cells, followed by an intensive review of non-embryotic autologous adult stem cells. The use of allogeneic MSCs, the fabrication of engineered constructs by seeding of natural or synthetic scaffolds with cells, released from autologous tissues will not be presented in this chapter, as only relatively few of these cell-based approaches have entered the clinical arena. In particular, we deliberate on the biology and clinical application of mesenchymal stem cells originating from freshly harvested bone marrow. We portray on the techniques of a marrow harvesting procedure using ultrasound and fluoroscopic techniques. Explicit scientific information is provided on the bone marrow aspirate cellular content, their specific biological functions and intercellular interactions, as these, among others, contribute to tissue regeneration following clinical regenerative medicine applications. Furthermore, we underline the differences between bone marrow aspirate and, centrifugated, bone marrow aspirate concentrate injectates, both prepared at point of care from freshly aspirated marrow.

Finally, a condensed literature review addressing a variety of clinical orthobiological indications, spinal disorders, chronic wounds, and critical limb ischemia is provided. Regenerative medicine technologies, using marrow-derived mesenchymal stem cell-based therapies, as part of the regenerative medicine treatment armamentarium, offer solutions to a number of undeniable clinical conditions that have not been able to adequately result in a solution through the use of medicines or surgeries.

## **2. What are stem cells?**

Becker, McCulloch, and Till first conducted experiments that lead to the discovery of stem cells in 1963. After injecting bone marrow cells into irradiated mice, nodules developed in proportion to the number of bone marrow cells injected, and they concluded that each nodule arose from a single marrow cell. At a later stage, they produced evidence that these cells were capable of endless self-renewal, which is as we know now, a fundamental feature of stem cells [1]. A stem cell is a type of cell that is non-specific/specialized in its function; in contrast, for instance, a heart or brain cell is functionally specific.

Generally, we recognize two types of stem cells, embryonic and non-embryonic, with two defining properties. Firstly, they have the capacity of self-renewal, therefore giving rise to more stem cells. Secondly, they are capable of differentiating into different lineages under appropriate conditions.

Embryonic stem cells (ESCs) are obtained from 5- to 12-day-old embryos, and they are pluripotent and have a high plasticity as they can differentiate into ectoderm, mesoderm, and endoderm layers, whereas non-embryonic stem cells (non-ESCs) are multipotent, and it appears that they are able to form multiple cell lineages which form an entire tissue, usually specific to one germ layer, e.g., adult stem cells [2].

The capability for stem cell potency, in combination with the relative ease to prepare bone marrow stem cell injectates, is an invaluable property for

**3**

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

regenerative medicine cell-based therapies in general and more specifically to treat, e.g. musculoskeletal disorders (MSK-D), chronic wounds, and critical limb

Non-ESCs are undifferentiated, and their proliferation potential compared to embryogenic stem cells is limited, as they have lost their pluripotent capability, placing them lower in the stem cell hierarchy. Nonetheless, it has been suggested that non-ESCs maintain their multipotent differentiation potential. Since they are categorized as allogenic products, they are commercially prepared from several allogenic sources, like amniotic fluid, umbilical cord, and Wharton's jelly [3]. In this chapter we will only deliberate on non-embryotic, autologous adult bone marrow aspirate (BMA)-derived progenitor/stem cells and other bone marrow (BM) stromal cells, prepared at POC with dedicated and approved centrifuges for BM

Friedenstein and colleagues reported first on the isolation of bone marrowderived stem cells from BM stroma and incubated it in plastic culture dishes and identified mesenchymal stem cells as colony-forming unit fibroblasts (CFU-Fs) [4]. The BM stroma is made up of a network of fibroblast-like cells and includes a subpopulation of multipotent cells which are able to generate the mesenchyme, known as the mass of tissue, that develops mainly from the mesoderm of the embryo subpopulation. The cells are referred to as mesenchymal stem cells (MSCs) [5]. The *Friedenstein* culture method revealed that MSCs are capable of differentiating into several connective tissue cell types [6], described first by

The bone is an organ composed of cortical and trabecular bone, cartilage, and

We recognize two categories of bone marrow tissue: the red and yellow marrow. Depending on age, teh red marrow is replaced by the yellow marrow. In adults, the

hematopoietic and connective tissues. The bone tissue has an essential role in the structure and protection of the human body. Spongy, or trabecular bone, is composed of a lattice of fine bone plates filled with hematopoietic marrow, fatcontaining marrow, and arterial-venous sinusoidal blood vessels. Furthermore, it consists of bone cells at different developmental stages (including pre-osteoblasts, osteoblasts, and osteocytes), collagen fibrils, and calcium and phosphate deposits [8]. Arterial vessels enter the marrow through foramina nutricia and then divide into several arterioles. Small arterioles and capillaries from these vessels span throughout the bone marrow and supply sinusoids, which are interconnected by inter-sinusoidal capillaries [9]. The BM tissue is soft, similar to the peripheral blood, flexible connective tissue comprising the center and the epiphysis of bones, referred to as the BM cavity. In this place a variety of new blood cells are produced

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

**2.2 Bone marrow-derived stromal cells**

Pittenger and associates [7].

**3. Bone marrow anatomical structure**

and ultimately released to the peripheral circulation.

**3.1 Red and yellow bone marrow**

**2.1 Non-embryotic autologous adult stem cells**

ischemia.

concentration.

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

regenerative medicine cell-based therapies in general and more specifically to treat, e.g. musculoskeletal disorders (MSK-D), chronic wounds, and critical limb ischemia.
