Comparative effects of ovariectomy and chemically induced menopause on alveolar bone healing in zoledronate-treated female mice

Alveolar socket is a highly dynamic site of bone remodeling and a clinically relevant model for studying healing disturbances associated with antiresorptive therapy. The present study aimed to investigate how different models of premature ovarian failure - ovariectomy (OVX) and chemically induced follicular depletion using 4-vinylcyclohexene diepoxide (VCD) - influence post-extraction alveolar bone repair in female mice, particularly when combined with zoledronic acid (ZL). Fifty C57Bl/6J female mice (4-6 months old) were assigned to six experimental groups: control (CT), OVX, chemically induced estropause using VCD, and their respective groups treated with ZL (CT + ZL, OVX + ZL, VCD + ZL). ZL (500 μg/kg/week, intraperitoneally) was administered for four weeks before maxillary incisor extraction and continued until euthanasia. Bone healing was evaluated at 7 and 21 days post-extraction using microCT, histology, birefringence, and immunohistochemistry for OPG and TRAP. At 21 days, ZL-treated groups exhibited reduced BV/TV compared to their untreated counterparts. The VCD + ZL group showed delayed healing, with disorganized trabeculae, persistent inflammatory infiltrates, and immature collagen matrix. In contrast, the OVX + ZL and CT + ZL groups showed improved bone quality and increased collagen maturation. No significant differences were observed in TRAP or OPG immunostaining across groups. The effects of ovarian failure were evident in the microarchitectural analysis of the 5L vertebrae. These findings suggest that while estrogen deprivation alone (via OVX or VCD) does not impair alveolar bone healing, the combination of VCD-induced premature ovarian failure and ZL treatment negatively impacts the healing process. This highlights a potential vulnerability in patients undergoing bisphosphonate therapy during premature menopause.