Purification and ex vivo expansion of postnatal human marrow mesodermal progenitor cells

It is here reported that mesenchymal stem cells known to give rise to limb- bud mesoderm can, at the single-cell level, also differentiate into cells o f visceral mesoderm and can be expanded extensively by means of clinically applicable methods. These cells were named mesodermal progenitor cells (MPC s). MPCs were selected by depleting bone marrow mononuclear cells from more than 30 healthy human donors of Cp45(+)/glycophorin-A (GlyA)(+) cells. Cel ls were cultured on fibronectin with epidermal growth factor and platelet-d erived growth factor BB and 2% or less fetal calf serum. It was found that 1/5 x 10(3) CD45(-)GlyA(-) cells, or 1/10(6) bone marrow mononuclear cells, gave rise to clusters of small adherent cells. Cell-doubling time was 48 t o 72 hours, and cells have been expanded in culture for more than 60 cell d oublings. MPCs are CD34(-), CD44(low), CD45(-), CD117 (cKit)(-), class I-HL A(-), and HLA-DR-. MPCs differentiated into cells of limb-bud mesoderm (ost eoblasts, chondrocytes, adipocytes, stroma cells, and skeletal myoblasts) a s well as visceral mesoderm (endothelial cells). Retroviral marking was use d to definitively prove that single MPCs can differentiate into cells of li mb bud and visceral mesoderm. Thus, MPCs that proliferate without obvious s enescence under clinically applicable conditions and differentiate at the s ingle-cell level not only into mesenchymal cells but also cells of visceral mesoderm may be an ideal source of stem cells for treatment of genetic or degenerative disorders affecting cells of mesodermal origin. (C) 2001 by Th e American Society of Hematology.