Bone Marrow Stroma
The bone marrow forms a suitable environment for stem cell survival, self‐renewal and formation of differentiated progenitor cells. It is composed of stromal cells and a microvascular network (Fig. 1.4). The stromal cells include mesenchymal stem cells, adipocytes, fibroblasts, osteoblasts, endothelial cells and macrophages and they secrete extracellular molecules such as collagen, glycoproteins (fibronectin and thrombospondin) and glycosaminoglycans (hyaluronic acid and chondroitin derivatives) to form an extracellular matrix. In addition, stromal cells secrete several growth factors necessary for stem cell survival.