The Validation of an Experimental Model in Wistar Female Rats to Study Osteopenia and Osteoporosis.

Background: Osteoporosis is a systemic disease characterized by a progressive decrease in bone density and deterioration of the tissue's microarchitecture. This results in greater structural fragility and a higher risk of fractures. Osteopenia represents the beginning of the process of decreasing bone density and, if left untreated, can lead to osteoporosis. The objective of this study was to validate an experimental model for establishing cases of decreased bone density that allows for the creation of different levels of severity of mineral loss and changes in bone microstructure. Materials and Methods: Twenty female Wistar rats, 12 weeks old and with a body weight ranging from 300 to 400 g, were used in this study. The animals were randomly distributed into five groups (n = 5 per group): a control group (CG), where the animals were not ovariectomized (OVX), and four experimental groups, where the animals were OVX and euthanized at different times: 30 days (G30), 40 days (G40), 60 days (G60), and 80 days (G80). The animals in the experimental groups underwent bilateral ovariectomy to induce mineral loss. The femurs were collected after the periods established for each group and analyzed using microcomputed tomography (μCT) to determine bone density and count the number of trabeculae. Furthermore, the T-score was calculated for each group. Results: There were significant differences in bone density when comparing all groups, with GC > G30 > G40 > G60 > G80. For the number of trabeculae, GC presented more trabeculae than all other groups. More trabeculae were also observed in G30 when compared to G40, G60, and G80; however, there were no differences between G40, G60, and G80. Regarding the calculation of the T-score by group, osteopenia was observed in G30 (T-score: -2.42) and osteoporosis was observed in G40, G60, and G80 (T-scores: -4.38, -6.34, and -7.71, respectively). Conclusions: The results demonstrate that ovariectomy induces progressive changes in bone structure, with the onset of osteopenia 30 days after ovariectomy and osteoporosis after 40 days in this experimental model. These results may aid future investigations that seek to focus on the specific treatment of osteopenia and/or osteoporosis.