Bone repair by stem cells

Human multipotent stromal cells were first characterized by Alexander Friedenstein as fibroblastic colony-forming cells from the nonhematopoietic,culture vessel-adherent fraction of bone marrow. Bone marrow transplants had provided circumstantial evidence for the presence of precursor cells of the various components of bone marrow stroma: osteoblasts, adipocytes, chondrocytes, among others, while in vitro culture and differentiation of these colony-forming units provided more direct evidence of their existence.