Basic fibroblast growth factor induces osteoclast formation in murine bone marrow cultures.

We determined the effect of basic fibroblast growth factor (bFGF) on osteoclast-like cell (OCL) formation in bone marrow cultures using C57BL/6 mice. Cells were cultured for 7 days with or without bFGF at various concentrations or 10(-8) mol/L 1,25(OH)2 vitamin D3 [1,25(OH)2D3]. bFGF dose-dependently increased OCL formation per well (10(-10) mol/ L = 40 +/- 2; 10(-9) mol/L = 146 +/- 13; 10(-8) mol/L = 156 +/- 12) compared with control (< 7 per well). The effects of bFGF at 10(-9) and 10(-8) mol/L were similar to that of 10(-8) mol/L 1,25(OH)2D3 (154 +/- 11 per well). OCLs formed by bFGF were multinuclear, tartrate-resistant acid phosphatase (TRAP)-positive, expressed calcitonin receptors, and formed characteristic resorption pits. We also determined whether bFGF enhanced OCL formation during the early proliferative or late differentiating phases of the cultures. When bFGF (10(-8) mol/L) was added only on days 1-2 or days 3-4 of 6 day cultures, there was a significant increase in OCL formation. In contrast, when bFGF was added only on days 5-6 few OCLs formed. Addition of bFGF at days 1-6 or days 1-2 and days 5-6 caused similar increases in OCL formation, which were greater than OCL formation induced by treatment for days 1-2 or days 1-4. We examined the production of prostaglandin E2 (PGE2) in the cultures because bFGF is a potent stimulator of PGE2 synthesis in bone, and PGE2 stimulates OCL formation. bFGF treatment significantly increased PGE2 levels in 7 day cultures (controls = 1.4 +/- 0.1 nmol/L, 10(-8) mol/L bFGF = 132.5 +/- 0.7 nmol/L). In addition, treatment of marrow cultures with the prostaglandin synthesis inhibitors, indomethacin or NS-398 (both at 10(-6) mol/L), completely blocked bFGF-induced OCL formation. We conclude that bFGF stimulates OCL formation in C57BL/6 bone marrow cultures by mechanisms that require prostaglandin synthesis. This pathway is likely to be one mechanism by which bFGF stimulates resorption.