Targeting integrin αVβ3–Ptgs2–mTOR signaling rescues bone formation in osteoporosis: from molecular mechanism toward therapy

Integrin αVβ3, a key ECM receptor, is essential for bone metabolism, yet its role in postmenopausal osteoporosis (PMOP) remains unclear. This study investigates the molecular mechanisms by which integrin αVβ3 regulates osteoblast function and bone homeostasis in PMOP. Using clinical samples, OVX mice, and in vitro models, we analyzed integrin αVβ3 expression and its impact on osteogenesis. Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated knockout, multi-omics profiling, and protein interaction assays (Co-IP, BLI, and structural modeling) were employed to dissect the underlying pathway. An AAV9-based in vivo overexpression system was developed to evaluate therapeutic potential. Integrin αVβ3 was downregulated in PMOP patients and OVX mice, correlating with osteoblast dysfunction and reduced bone formation. Mechanistically, integrin αVβ3 deficiency upregulated Ptgs2, which directly bound to mammalian target of rapamycin (mTOR) via a hydrogen bond between Ptgs2-Glu52 and mTOR-Ser2159, inhibiting mTOR phosphorylation. This suppression disrupted mTORC1-S6K/4EBP1 signaling, impairing osteoblast proliferation and survival. Notably, AAV9-mediated integrin αVβ3 overexpression rescued bone loss in OVX mice. Our findings unveil a novel integrin αVβ3–Ptgs2–mTOR axis in PMOP pathogenesis: estrogen deficiency reduces integrin αVβ3, enabling Ptgs2-mediated mTOR inhibition and osteogenic decline. This study identifies integrin αVβ3 as a potential therapeutic target to restore bone formation in osteoporosis.