Targeting ferroptosis to rescue osteogenic differentiation in BRONJ-affected jawbone mesenchymal stem cells: the role of miR-145-3p and exosome-mediated therapy

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BACKGROUND: Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a severe, therapy-refractory condition driven by ferroptotic disruption of jawbone-derived mesenchymal stem cells (MSCs) biology. We dissect this mechanism to validate ferroptosis as a therapeutic target. METHODS: We first demonstrated that miR-145-3p is mechanistically coupled to ferroptosis and osteogenesis in BRONJ model by gain- and loss-of-function studies. To evaluate therapeutic efficacy under pathologically relevant conditions, we designed three models: (i) Local BRONJ repair model: miR-145-3p-enriched exosomes were encapsulated in an injectable hydrogel scaffold and grafted into necrotic alveolar bone to assess direct BRONJ resolution. After local BRONJ treatment, endogenous MSCs were re-isolated, and both cellular and exosomal miR-145-3p levels were quantified. (ii) Osteoporosis treatment model: The reprogrammed MSCs derived from treated BRONJ rats were then administered intravenously to osteoporotic littermates to evaluate whether these MSCs retain systemic osteogenic competence. (iii) Critical-sized calvarial defect repair model: To further dissect the intrinsic osteogenic capacity, reprogrammed MSCs derived from treated BRONJ rats were fabricated into cell-sheet/HA-TCP “sandwich” constructs and transplanted into calvarial defects. RESULTS: BRONJ markedly compromised MSCs viability while elevating hallmarks of ferroptosis that were reversed by the ferroptosis inhibitor. Concomitantly, osteogenic capacity declined, as shown by reduced ALP activity, mineralized nodules, new bone formation and expression of RUNX2 and OCN. Mechanistically, we identified a miR-145-3p/IREB2 regulatory circuit that governs ferroptosis in BRONJ-derived MSCs; exosome-mediated delivery of miR-145-3p reinstated this axis, thereby reactivating the MSCs osteogenesis and driving in situ bone regeneration. Critically, after local BRONJ therapy, the reprogrammed MSCs were (i) infused via tail vein into osteoporotic rats, significantly elevating bone mass, and (ii) engineered into cell-sheet/HA-TCP “sandwich” constructs that achieved robust repair of critical-sized calvarial defects. These data establish exosomal miR-145-3p as a therapeutic that mitigates ferroptosis and restores the osteogenic competence of jawbone-derived MSCs for bone regeneration. CONCLUSION: Collectively, our findings establish the miR-145-3p/IREB2/ferroptosis axis as an important regulator of BRONJ pathology and demonstrate that exosomal delivery of miR-145-3p not only ameliorates localized BRONJ but also substantially reinstates the systemic osteogenic potential of jawbone-derived MSCs, offering a pre-clinical promising strategy to combat both BRONJ and associated bone loss disorders.

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