A quadripotential mesenchymal progenitor cell isolated from the marrow of an adult mouse

Adult marrow contains mesenchymal progenitor cells (MPCs) that have multipl e differentiation potentials. A conditionally immortalized MPC clone, BMC9, has been identified that exhibits four mesenchymal cell phenotypes: chondr ocyte, adipocyte, stromal (support osteoclast formation), and osteoblast. T he BMC9 clone, control brain fibroblasts and another marrow-derived clone, BMC10, were isolated from a transgenic mouse (H-2K(b)-tsA58) containing a g ene for conditional immortality. To test for chondrogenic potential, cells were cultured in defined medium containing 10 ng/ml transforming growth fac tor beta and 10(-7) M dexamethasone in 15-ml polypropylene tubes ("aggregat e cultures"). Adipogenic potential was quantitated by flow cytometry of Nil e Red-stained cells cultured for 1 and 2 weeks in medium containing isobuty l methylxanthine, indomethacin, insulin, and dexamethasone. Support of oste oclast formation was measured by quantitating multinucleated tartrate-resis tant acid phosphatase-positive cells in spleen cell cocultures of test clon es (immortomouse clones and positive control ST2 cells) cultured in the pre sence of 10(-7) M vitamin D-3 and 150 mM ascorbate-2-phosphate. In vivo ost eogenic potential was assayed by histologic examination of bone formation i n subcutaneous implants, into athymic mouse hosts, of a composite of cells combined with porous calcium phosphate ceramics. The bone marrow-derived cl one BMC9 has the potential to express each of the four mesenchymal characte ristics tested, while brain fibroblasts, tested under identical conditions, did not exhibit any of these four mesenchymal characteristics. BMC10 cells exhibited osteogenic and chondrogenic phenotypes, but showed only minimal expression of adipocytic or osteoclast-supportive phenotypes, Clone BMC9 is , minimally, a quadripotential MPC isolated from the marrow of an adult mou se that can differentiate into cartilage and adipose, support osteoclast fo rmation, and form bone. The BMC9 clone is an example of an adult-derived mu ltipotential progenitor cell that is situated early in the mesenchymal line age.