Anabolic effects of basic fibroblast growth factor in the tibial diaphysis of ovariectomized rats

The purpose of this study was to determine the effects of basic fibroblast growth factor (bFGF) on cortical bone in ovariectomized (ovx) rats. Female Sprague-Dawley rats were subjected to sham surgery or ovariectomy at 3 months of age and maintained untreated for 2 months after surgery. Polyurethane catheters were then inserted in the jugular veins of all rats for daily intravenous treatments with vehicle or bFGF at doses of 100 or 200 microg/kg for 7 or 14 days. Other groups of ovx rats were killed at 7 or 14 days after withdrawal of treatment with the higher dose of bFGF. Quantitative bone histomorphometry was performed in undecalcified cross sections of the tibial diaphysis. Cortical bone area was nearly the same in vehicle-treated control and ovx rats, but a small, statistically significant increase in this structural variable was observed in ovx rats treated with both doses of bFGF. This small increase in cortical bone area was maintained at 7 days after withdrawal of bFGF treatment. Fluorochrome-based analyses of periosteal and endocortical bone formation were inconclusive due to an inhibitory effect of bFGF on bone mineralization. However, a marked increase in fluorescent bone area was observed within the marrow cavity of bFGF-treated OVX rats during the withdrawal period. The results indicate that treatment of OVX rats with bFGF for only 7 to 14 days augments cortical bone mass and induces formation of bone spicules within the marrow cavity of the tibial diaphysis. These bone anabolic effects of the growth factor support its consideration as a potential osteoporosis therapy.