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Basic fibroblast growth factor has rapid bone anabolic effects in ovariectomized rats.
R A Power1, U T Iwaniec, K A Magee
1Department of Transgenics, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA. powerra@pbrc.edu
Summary
Basic fibroblast growth factor (bFGF) rapidly stimulates bone formation in ovariectomized rats within 24 hours. This anabolic effect increases over time, suggesting bFGF directly impacts bone cells rather than relying on early IGF-I or TGF-beta gene upregulation.
Area of Science:
- Bone biology
- Endocrinology
- Regenerative medicine
Background:
- Basic fibroblast growth factor (bFGF) exhibits potent bone anabolic effects.
- Growth factors like IGF-I and TGF-beta are potential mediators of bFGF's action.
- Ovariectomy (OVX) in rats leads to increased bone turnover and decreased bone mass.
Purpose of the Study:
- To investigate the early effects of bFGF on bone formation and gene expression in OVX rats.
- To determine if IGF-I and/or TGF-beta gene upregulation precedes or coincides with bFGF's bone anabolic effects.
- To elucidate the temporal relationship between bFGF treatment and bone formation markers.
Main Methods:
- Ovariectomy or sham surgery was performed on Sprague Dawley rats.
- OVX rats were treated with bFGF (200 microg/kg/day IV) or vehicle for up to 10 days.
- Lumbar vertebrae were analyzed for cancellous bone histomorphometry and gene expression (IGF-I, TGF-beta1).
Main Results:
- bFGF treatment significantly increased bone formation markers (osteoblast surface, osteoid surface, osteoid volume) starting at 24 hours.
- IGF-I gene expression increased significantly after 2 days of bFGF treatment.
- TGF-beta1 gene expression showed a modest increase only after 10 days of bFGF treatment.
Conclusions:
- bFGF exerts rapid bone anabolic effects in OVX rats, initiating within 24 hours of treatment.
- The early bone formation response to bFGF is not primarily mediated by early upregulation of IGF-I or TGF-beta gene expression.
- bFGF may induce bone lining cells to differentiate into osteoblasts, driving the rapid increase in bone formation.