Effects of ERα gene overexpression on bone mineral density and calcium and phosphorus metabolism inovariectomized osteoporosis mice

Abstract

Objective: To investigate the effects of estrogen receptor α (ERα) gene overexpression on bone metabolism and calcium and phosphorus metabolism in ovariectomized osteoporosis mice, and to provide experimental basis for targeted gene therapy of osteoporosis. Methods: Thirty SPF female mice were randomly divided into sham operation group, model group and ERα overexpression group with 10 mice in each group. After the model was established, the ERα overexpression group was transfected with recombinant adenovirus vector carrying mouse ERα gene by intraspinal injection. The model group was transfected with empty virus, and the sham operation group was not treated. The expression of ERα gene in bone tissue of mice was detected by quantitative Real-time PCR (qRT-PCR). Bone mineral density (BMD) of mouse femur was measured after modeling. Trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular segregation (Tb.Sp), bone volume fraction (BV/TV) and biomechanical strength of femur were measured by micro-CT scanning. Serum levels of calcium (Ca), phosphorus (P), osteocalcin (BGP) and alkaline phosphatase (ALP) were measured by automatic biochemical analyzer. The expressions of tissue inhibitor of metalloproteinases 1 (TIMP-1) and monocyte chemotactic protein 1 (MCP-1) in bone homogenate were detected by Immunohistochemistry. Results: Compared with sham operation group, the expression level of ERα gene in bone tissue of model group was decreased significantly, the levels of BMD, BV/TV, Tb. Th, maximum load, rigidity coefficient, Ca and P were decreased, while the levels of Tb. Sp, BGP and ALP were increased significantly (P＜0.05). Compared with the sham operation group, the expression level of TIMP-1 protein in the bone tissue of the model group was significantly decreased, while that of MCP-1 protein was increased, while that of the ERα overexpression group was increased while that of MCP-1 was decreased (P＜0.05).The levels of ERα gene expression, BMD, BV/TV, TB. Th, maximum load, rigidity coefficient, Ca and P in the ERα overexpression group were significantly higher than those in the model group, while Tb. Sp, BGP and ALP were significantly lower (P＜0.05). Compared with the sham operation group, mean optical density of TIMP-1 in the bone tissue of the model group was significantly decreased, while that of MCP-1 was significantly increased, and that of the ERα overexpression group was significantly increased while that of MCP-1 was significantly decreased (P＜0.05). Conclusion: ERα gene overexpression can improve osteoporosis by regulating bone mineral density, bone parameters, bone metabolism, calcium and phosphorus metabolic indicators and the expression levels of TIMP-1 and MCP-1 in tissues.