Abstract:

BACKGROUND: Animal experiment has demonstrated that adiponectin affected proliferation and differentiation of osteoblasts and osteoclasts. The clinical research found that adiponectin has certain correlation to bone density, however, the mechanisms remains poorly understood. 
OBJECTIVE: To evaluate the effect of direct injection of recombinant rat adiponectin into the hip joint on steroid-induced avascular necrosis of femoral head in rats.
METHODS: Sprague Dawley female rats were randomly divided into 4 groups. All rats were established the early steroid-induced avascular necrosis of femoral head models by peritoneal injecting prednisolone acetate except those in the control group, which were received isodose physiological saline. Then, the rats in the low dose group and high dose group were injected with 1 μg or 10 μg of recombinant adiponectin into the right hip, respectively; those in the saline group were injected with isodose physiological saline. The right femoral head of all rats were examined by X-ray at 4 weeks after the injection. The extent of necrosis and repair were observed under a light microscope. Trabecular bone area, empty bone lacuna rate, vascular number were analyzed and the expression of tumor necrosis factor α (TNF-α) of the femoral head was detected by immunohistochemical method.
RESULTS AND CONCLUSION: The results of X-ray examination showed that control group and high dose group were normal, bone density of femoral head was uneven and trabecular bone was fuzzy in the saline group and low dose group. Bones of control group were hard, bones of saline group were significantly osteoporosis, bone hardness of low dose group and high dose group were between control group and saline group. Light microscopy showed that trabecular bone, bone lacunae, vascular number of control group were normal, and saline group were significantly abnormal compared with control group (P < 0.01); High dose group was significantly superior to the results of saline group (P < 0.01), the differences between low dose group and saline group were not significant (P > 0.05), the expression of TNF-α in the saline group was higher than the other groups (P < 0.01). The results demonstrated that, direct injection of recombinant rat adiponectin into hip joint can promote the repair of steroid-induced avascular necrosis of femoral head in rats in a dose-dependent correlation.