Dental Tissue–Derived Mesenchymal Stem Cells Modulate Mitochondrial and OPG/RANKL Signaling in Obesity-Associated Osteoporosis Under Estrogen-Deficient and Intact Conditions

Background: /Objectives: Obesity and menopause are major determinants of skeletal deterioration; however, their combined effects on bone remodeling and associated cellular bioenergetics remain incompletely understood. This study aimed to determine whether obesity induces osteoporotic alterations under both estrogen-replete and estrogen-deficient conditions and to evaluate the therapeutic potential of dental tissue–derived mesenchymal stem cells (D-MSCs). Methods: Female mice were subjected to ovariectomy (OVX) and/or high-fat diet (HFD) feeding for 16 weeks to establish obesity-associated osteoporosis models. D-MSCs were administered intraperitoneally at defined intervals. Body weight and serum leptin levels were measured to assess metabolic status. Femoral tissues were analyzed by quantitative real-time PCR for estrogen receptors (ERα, ERβ), inflammatory markers (Il-1β, Tnf-α), mitochondrial regulators (Pgc1α, Pgc1β), and the OPG/RANKL ratio. Histological analysis was performed to evaluate bone marrow adiposity. Results: HFD significantly increased body weight and serum leptin levels in both intact and OVX mice. Obesity was associated with reduced expression of ERα and ERβ, decreased Pgc1α levels, and a lower OPG/RANKL ratio, accompanied by increased Il-1β, Tnf-α, and Pgc1β expression. D-MSC administration attenuated body weight gain and reduced leptin levels, particularly in OVX mice. In femoral tissue, D-MSC treatment restored estrogen receptor expression, increased Pgc1α, decreased Pgc1β, and normalized the OPG/RANKL ratio. In addition, inflammatory marker expression and bone marrow adiposity were reduced following MSC administration. Conclusions: Obesity induces bone remodeling dysregulation under both intact and estrogen-deficient conditions, characterized by altered estrogen signaling, inflammatory activation, and mitochondrial imbalance. D-MSC administration was associated with partial restoration of these alterations, suggesting a potential role in modulating metabolic and skeletal homeostasis in obesity-associated bone loss.