Dexamethasone inhibits formation of osteoclast-like cells in bone-marrow cultures

Our observations confirm the previously reported observation that multinucleated cells develop within a two-week period in cat bone-marrow cultures. Calcitonin induces cytoplasmic contraction in these multinucleated cells, which indicates that they resemble osteoclasts. After seven days of culture, cat bone-marrow cultures contain both non-attached mononuclear cells and attached mononuclear and polynuclear cells. We have cultured the attached and non-attached cell populations separately from day 7 onward and have observed the appearance of multinucleated cells in both culture systems. In both types of cultures, dexamethasone (10(-9)-10(-7) mol/L) reduced the number of multinucleated cells. This effect of dexamethasone was more rapid in the cultures derived from non-attached cells (seven days) than in cultures derived from attached cells (14 days), suggesting that two different mechanisms are involved. Dexamethasone had no effect on the survival of multinucleated cells already formed.