Basic fibroblast growth factor inhibits osteoclast formation induced by 1 alpha,25-dihydroxyvitamin D-3 through suppressing the production of osteoclast differentiation factor

Basic fibroblast growth factor (bFGF) inhibited osteoclast-like cell (OCL) formation in cocultures of mouse spleen cells with either osteoblasts or a stromal cell line, ST2, in the presence of 1 alpha,25-dihydroxyvitamin D-3 [1,25(OH)(2)D-3]. bFGF directly acted on osteoblasts/stromal cells, but not osteoclast progenitors, to inhibit 1,25(OH)(2)D-3-induced OCL formation, b FGF suppressed the mRNA expression of osteoclast differentiation factor (OD F) but did not affect that of osteoclastogenesis inhibitory factor (OCIF) i n ST2 cells treated with 1,25(OH)(2)D-3 and dexamethasone. Enzyme-linked im munosorbent assay showed that bFGF :hardly affected OCIF production in the treated ST2 cells. A genetically engineered soluble form of ODF, but not an ti-OCIF neutralizing antibody, abolished bFGF-mediated inhibition of OCL fo rmation, bFGF suppressed the binding of I-125-labeled OCIF to both ST2 cell s and osteoblasts treated with 1,25(OH)(2)D-3. These findings indicate that bFGF inhibits 1,25(OH)(2)D-3-induced OCL formation via suppression of ODF production by osteoblasts/stromal cells. (C) 1999 Academic Press.