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.