Effects of Ovariectomy and Low-Calcium Diet on Six Different Sites of the Rat Skeleton

The aim of this study was to evaluate structural and micro-architectural changes in the mandible, parietal bone, femur, and tibia in OVX rats at different time periods after ovariectomy. Forty-two 11-month-old female Wistar rats were used. Six rats without surgery were euthanized to serve as a baseline. Eighteen rats were ovariectomized and fed with a calcium-deficient diet, and eighteen animals were used as controls (Ctrls) and fed with a standard diet. Six OVX rats and six Ctrls were euthanized at 3, 6, and 9 months. Qualitative histology and dual-energy X-ray absorptiometry (DXA) were performed. Histological evaluation of bones harvested from the OVX groups revealed trabecular bone reduction, while no significant differences in the cortical bone of OVX and Ctrls were observed. DXA measurements of (1) femoral diaphysis showed a significant decrease in the OVX group compared to the Ctrl groups at 3 (p = 0.041), 6 (p < 0.001), and 9 months (p < 0.001); (2) the proximal tibia showed a significant decrease in the OVX group compared to the Ctrl groups (p < 0.001); (3) parietal bone showed a significant difference between OVX and Ctrls at 6 months (p = 0.012); and (4) the mandible showed no significant differences between the OVX and Ctrl groups. OVX aged rats might present reductions in the density of the femoral diaphysis, proximal tibia, parietal bone, and mandible at different time points. These findings contribute to the field of biomimetics by providing more details for the understanding of age- and hormone-related bone changes in the osteoporotic-like rat model. Such data are critical for the development of biomimetic materials and structures that attempt to simulate natural bone adaptation and deterioration, especially in the context of postmenopausal or osteoporotic conditions.