Bone Quality of the Femoral Mid-Shaft of Ovariectomized Rats Fed a Low-Mineral Diet

Ovariectomized (OVX) rats are accepted models for screening potential therapeutic agents for osteoporosis. A low-mineral diet accelerates bone loss in OVX rats. This study aimed to determine changes in bone quality caused by ovariectomy or by combined ovariectomy and a mineral-deficient diet. Forty-eight female Wistar rats, aged 19 weeks, were distributed into 3 groups (n = 16 per group): Group 1: (control) subjected to a sham operation and administered a normal diet, Group 2: OVX rats fed a normal diet, and Group 3: OVX rats fed a low-mineral diet. The rats were sacrificed after 4, 8, 16, and 24 weeks. The density distribution and volume of the femur mid-shaft were evaluated to assess bone quality using micro-computed tomography and polarized microscopy. Bone strength was evaluated using a 3-point bending test. Bone density distribution, bone volume, and strength were the lowest for Group 3 and the highest for Group 1 at all times. Using a polarized microscope, we found that the tubular structures of the Haversian and Volkmann’s canals were decreased in Group 3 compared with those of Groups 1 and 2. Positive correlations were noted between fracture load and bone density, fracture load and bone volume, and bone volume and bone density in Group 3, and between bone density and volume, and bone volume and fracture load in Groups 2 and 3. We conclude that estrogen deficiency (ovariectomy) and mineral deficiency had separate as well as combined effects on bone quality.