[An experimental study on the influence of osteoporosis to bone repairing with bone matrix gelatin in ovariectomized rats].

OBJECTIVE: To study the influence of experimentally osteoporosis to osteogenic efficiency of bone matrix gelatin(BMG) implanted into the calvarial defects of rats. METHODS: Sixty-eight female SD rats of 12 +/- 1 weeks were randomly divided into two groups with 34 rats in each group. The ovaries were excised in the ovariectomized group (VG). The control group underwent sham surgery. Ninety days after ovariectomy, 10 rats from each group were examined to ensure the formation of postmenopausal osteoporosis by measuring bone density of the femur with single photon absorptiometric measurements. A critical-sized (8 mm in diameter) calvarial defect was created on the rest of 48 rats. Bone matrix gelatin was implanted to the defect. The rats were scarified at the 21st and 56th day after surgery respectively. The new bone forming capability of BMG was evaluated with undecalcified histological observation, tetracycline fluorescence marker, quantitative bone histomorphometry, At 90th day after ovariectomy, bone density of scanning electron microscopy and X-ray spectrometry. RESULTS: OVG showed very significant difference compared with the control group (0.315 +/-.015) g/cm2 vs [(0.347 +/- 0.017) g/cm2, P < 0.01 ]. At the 21st day following the implantation operation, new bone formed within the bone defects in both groups. The amount of new bone in OVG was lower than the control group. The tetracycline-labeled region in the bone defect was sparser in the OVG. At the 56th day, the bone defects healed mostly in the control group but fibrous tissue filled parts of bone defect in the OVG. The distance between two fluorescent lines of incorporated tetracycline and the mean mineralization deposition were significantly lower in the OVG than the control at the 21st day and 56th day. Mineralization of callus in OVG was inferior. Significant difference was found between the OVG and the control group in the calcium to phosphate ratio of callus in bone defects at the two time-points. CONCLUSIONS: Experimentally induced osteoporosis depressed osteogenic efficiency of BMG, suggesting that estrogen could play an important role in bone remodeling with bone substitute participating.

[Effects of stilbestrol on bone growth and metabolism in ovariectomized rats].

OBJECTIVE: To study the effects of stilbestrol on bone growth and metabolism in ovariectomized rats. METHODS: Twenty-seven 3-month-old female SD rats were randomly divided into 3 equal groups, namely the control group, ovariectomized group (OEG), and OEG+estrogen (OEG+E) group. After ovariectomy, the rats in the third group were given stilbestrol 0.022 5 mg/d x kg x b x w by intragastric gavage for 90 d. A digital image analysis system was used for the measurement of histomorphometric parameters in the proximal tibial metaphysis of the rats. The three-dimensional structure of the femur was observed with scanning electron microscope, with the blood cholesterol level determined and the main viscera weighted. RESULTS: In comparison with the control rats, the trabecular bone area (TbAr) of ovariectomized rats was significantly reduced (-65%), trabecular bone space (TbSp) enlarged (+189%), and the bone formation rate (BFR) accelerated (+91%). The cancellous bone of the femurs manifested obvious signs of thinning, roughening and resorption lacunae to cause trabecular bone discontinuance, and osteoporosis occurred. The rats treated with stilbestrol, in contrast, had increased TbAr (by 128%), reduced TbSp (by 63%), lowered BFR (by 49%), and reduced osteoclasts (by 32%). The cancellous bone of the femurs was well arranged in close connection with each other, and the high cholesterol level and endocrinic changes in response to ovariectomy was corrected by stilbestrol, which also caused the increase of the uterine weight. CONCLUSION: Stilbestrol may help prevent primary osteoporosis but may increase the risk of female genital cancer.