Iron oxide nanoparticles-driven mitochondrial renewal rejuvenates the aged bone marrow niche

With the aging population, treating age-related osteoporosis remains challenging due to the dysfunctional bone marrow microenvironment characterized by chronic inflammation, metabolic dysregulation, and impaired mitochondrial function in senescent cells. While mitochondrial transfer from macrophages to bone marrow mesenchymal stem cells (BMSCs) offers a promising therapeutic avenue, its efficacy is limited in aged niches where donor mitochondria exhibit functional deficits and poor recipient compatibility. We engineered KGM-PEG-SPIONs, functionalized Fe₃O₄ nanoparticles that enhance donor mitochondrial quality via autophagy activation and Fe-S cluster biogenesis, promote M2 macrophage polarization, and improve compatibility with the oxidative and inflammatory environment of senescent BMSCs. These M2-like mitochondria are transferred through connexin 43 gap junctions, restoring membrane potential, ATP production, calcium homeostasis, and osteogenic differentiation in recipient cells. In aged osteoporotic models, KGM-PEG-SPION-functionalized scaffolds remodel immune niches and promote bone formation. By integrating organelle quality control with environment-adapted mitochondrial transfer, this strategy surpasses approaches focusing solely on transfer quantity or polarization, establishing a programmable nanoplatform for organelle-based regeneration.