Murine bone marrow stromally derived BMS2 adipocytes support differentiation and function of osteoclast-like cells in vitro.

Stromal cells are required for in vitro osteoclast differentiation and maturation. The murine bone marrow stromally derived BMS2 cell line exhibits adipocytic and osteoblastic features as well as the ability to support lymphopoiesis and myelopoiesis. This work examined the ability of the BMS2 cell in either the preadipocyte or adipocyte state to support the formation of osteoclast-like cells. BMS2 cells can be induced to undergo adipogenic differentiation in response to treatment with glucocorticoids or thiazolidinedione compounds. Primary bone marrow cells, enriched for hematopoietic progenitors and depleted of their adherent stromal and macrophage populations, were stimulated with vitamin D3 (vitamin D; 10(-8) M) to undergo osteoclast differentiation and maturation when cocultured with BMS2 cells. In both preadipocyte and adipocyte-enriched BMS2 stromal layers, comparable numbers of tartrate-resistant acid phosphatase-positive osteoclast-like cells, characterized by their response to salmon calcitonin with an increase in cAMP and formation of resorption pits on bovine bone slices, were formed. The gene expression and protein levels of macrophage colony-stimulating factor produced by preadipocyte and adipocyte-rich BMS2 layers were comparable. However, adipocyte-rich stromal layers supported osteoclast-like cell formation longer in culture than preadipocytes, independent of the agent used to induce adipocyte differentiation. These studies demonstrate for the first time that fully differentiated adipocyte stromal cells can support osteoclast-like cell formation and function in vitro.