3. Mesenchymal stem/stromal cells (MSCs)

#### 3.1. History

The concept of mesenchymal stem/stromal cells (MSCs) was first introduced about half a century ago. In the 1970s, [12] Alexander Friedenstein described a population of bone marrow-derived cells of mesodermal origin. These MSCs were shown to have the ability to self-renew and to differentiate into a multitude of mesodermal cell types [13–15]. Bone marrow MSCs represent a heterogeneous population derived from the nonblood-forming fraction of bone marrow, but have the ability to regulate hematopoietic cell development. In vitro, adult mesenchymal stem cells resident in this bone marrow fraction differentiate into bone, cartilage and fat [16]. Recently, a standardized nomenclature for MSCs has been proposed and the term "multipotent mesenchymal stromal cells" has been introduced [15] to refer to this population of fibroblast-like, plasticadherent cells [17]. Their asymmetric division produces one identical daughter stem cell and a second progenitor cell that becomes committed to a lineage-specific differentiation program [18].
