DEXAMETHASONE STIMULATES OSTEOCLAST-LIKE CELL-FORMATION BY INHIBITINGGRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR PRODUCTION IN MOUSE BONE-MARROW CULTURES

We investigated the effect of glucocorticoid on the generation of oste oclasts. In mouse bone marrow culture systems, dexamethasone, a synthe tic glucocorticoid analog, enhanced osteoclast-like cell formation ind uced by 1,25-dihydroxyvitamin D-3 [1,25-(OH)(2)D-3] in a dose-dependen t manner. Conversely, dexamethasone inhibited the endogenous productio n of granulocyte-macrophage colony-stimulating factor (GM-CSF) in bone marrow cultures. GM-CSF, when added exogenously, suppressed not only the osteoclast-like cell formation induced by 1,25-(OH)(2)D-3. but als o the stimulatory effect of dexamethasone, and addition of anti-GM-CSF neutralizing antibody to the cultures significantly increased the ost eoclast-like cell formation induced by 1,25-(OH)(2)D-3. These observat ions suggest that dexamethasone directly affects bone marrow cells and enhances osteoclast generation by inhibiting the endogenous productio n of GM-CSF, which may function as a negative regulator of osteoclast formation.