Early-apoptotic membrane engineering of M2 macrophage-derived nanovesicles enables osteoimmunomodulatory bone repair

Critical-sized bone defects remain difficult to repair because persistent inflammation, insufficient osteogenesis, and excessive osteoclast activity collectively compromise regenerative progression. Herein, an apoptotic reparative nanovesicle platform is developed by combining M2 macrophage polarization with early apoptotic membrane remodeling. Membrane-derived nanovesicles prepared from these donor cells (M2-Apo-NVs) retain the pro-repair imprint of M2 macrophages while displaying enhanced surface phosphatidylserine exposure. Relative to M2-derived nanovesicles, M2-Apo-NVs exhibit stronger cellular internalization, more effectively reprogram inflammatory macrophages toward a pro-resolution phenotype, promote osteogenic differentiation of bone marrow mesenchymal stem cells, and suppress RANKL-induced osteoclastogenesis through inhibition of the NF-κB/NFAT axis. For local delivery, M2-Apo-NVs are incorporated into a photocrosslinkable methacrylated hyaluronic acid hydrogel, enabling sustained presentation within a murine critical-sized calvarial defect. In vivo, the composite hydrogel markedly improves bone regeneration, accompanied by reduced inflammatory signaling, enhanced osteogenic activity, and restrained osteoclast-associated remodeling. These findings establish donor-membrane state engineering as an effective strategy for upgrading cell-derived nanovesicles and identify M2-Apo-NVs as a promising osteoimmunomodulatory therapeutic for bone defect repair.