Chitosan thermosensitive hydrogel-based sustained-release system of Netrin-1 overexpressing macrophage exosomes: synergistic enhancement of angiogenesis and nerve regeneration

Abstract Peripheral nerve injury (PNI) affects over 20 million individuals globally each year, with incomplete nerve regeneration presenting a significant socioeconomic burden, particularly in diabetic patients. M2 macrophages play a crucial role in nerve regeneration by promoting tissue remodeling and repair. However, the post-injury microenvironment impedes the stabilization of the M2 phenotype, limiting their therapeutic potential. In vitro experiments demonstrate that macrophages modified with Netrin-1 can be polarized toward the M2 phenotype. Exosomes secreted by these Netrin-1-modified macrophages (N-Exos) significantly enhance endothelial cell proliferation, migration, tube formation, and survival under hyperglycemic conditions. The underlying mechanism is likely mediated by the activation of the PI3K/AKT/mTOR pathway through Unc5b. To further enhance the therapeutic effects of N-Exos, we incorporated these exosomes into a berberine-modified chitosan-based hydrogel (NE@CSB), thereby developing an innovative synergistic therapeutic approach. The NE@CSB hydrogel demonstrates favorable injectability, thermoresponsive sol-gel transition, strong tissue adhesion, and sustained release of exosomes. In the sciatic nerve injury model of diabetic mice, blood flow perfusion and histological analysis of injured nerves demonstrated that NE@CSB hydrogel could effectively enhanced angiogenesis and sciatic nerve regeneration. Overall, NE@CSB presents a promising and safe therapeutic strategy for the clinical treatment of diabetic PNI.