Early period of fracture healing in ovariectomized rats

To evaluate the effect of osteoporosis on fracture healing through observing the histomorphological changes, bone mineral density of callus and expression and distribution of transforming growth factor beta 1 (TGF-beta1), basic fibroblast growth factor (bFGF) and bone morphogenetic protein-2 (BMP-2) in ovariectomized rats.

Sixty female Sprague-Dawley rats (aged 12 weeks and weighing 235 g on average) were randomly divided into an ovariectomized (OVX) group (n=30) and a sham-operated (SO) group (n=30). Ovariectomy was performed in the OVX rats and same incision was made in the SO rats. Three months later, fracture of femoral shaft was made on all the rats. Then they were killed at different time points. Callus formation was observed with histological and immunohistochemical methods.

A reduction in callus and bone mineral density in the healing femur and a decrease of osteoblasts expressing TGF-beta1 near the bone trabecula were observed in the OVX rats 3-4 weeks after fracture. Histomorphological analysis revealed a higher content of soft callus in the OVX rats than that in the SO rats. Immunohistochemistry results showed that no remarkable difference in expression and distribution of BMP-2 and bFGF between the OVX and SO groups was found.

Osteoporosis influences the quantity and quality of callus during the early period of fracture healing. The effect of osteoporosis on fracture healing has no relationship with the expression of BMP-2 or bFGF. The decreased expression of TGF-beta1 in osteoblasts may cause a decrease in quality of fracture healing after osteoporosis.