Effects of basic fibroblast growth factor on bone formation in vitro.

Basic fibroblast growth factor (bFGF) was studied for its effects on bone formation in cultured rat calvariae. bFGF at 0.1-100 ng/ml stimulated [3H]thymidine incorporation into DNA by up to 4.4-fold. bFGF also increased the number of colcemid-induced metaphase arrested cells and the DNA content. Transient (24 h) treatment with bFGF enhanced [3H]-proline incorporation into collagen 24-48 h after the factor was removed; this effect was DNA synthesis dependent and blocked by hydroxyurea. The collagen stimulated by bFGF was type I, and this effect was observed primarily in the periosteum-free bone. In contrast, continuous treatment with bFGF for 24-96 h inhibited [3H]proline incorporation into type I collagen. bFGF did not alter collagen degradation. In conclusion, bFGF stimulates calvarial DNA synthesis, which causes an increased number of collagen-synthesizing cells, but bFGF has a direct inhibitory effect on collagen synthesis.