Mesenchymal Stem Cells

Adult bone marrow contains both hematopoietic and nonhematopoietic stem cells, also termed mesenchymal stem cells (MSCs), or mesenchymal progenitor cells. MSCs are cells capable of differentiating into cells of the mesenchymal lineage (1 –3 ). These cells were previously referred to as “marrow stromal cells” or “colony-forming unit-fibroblast” (CFU-F), reflecting their origin and morphology in culture (4 ,5 ). Bone marrow stroma is the main source of these multipotent nonhematopoietic mesenchymal stem cells (6 ,7 ). MSCs derived from bone marrow can be readily isolated and expanded in vitro. Due to their ability of self-renewal and their potential to differentiate into terminal osteocytes, chondrocytes, myocytes, tenocytes, adipocytes, and neural cells in vivo and in vitro (8 –11 ), bone marrow-derived MSCs have attracted considerable attention as potential tools for therapeutic gene transfer.