Exosomes from CD133(+)CD271(+) human urine-derived stem cells combined with a novel photosensitive hydrogel promote repair after spinal cord injury.

BACKGROUND: Failed regeneration following severe spinal cord injury (SCI) results from both the limited intrinsic regenerative capacity of adult neurons and an inhibitory local microenvironment. Exosome-based cell-free therapy derived from stem cells is a safer and more promising regenerative strategy. In this study, we isolated extracellular vesicles from a urine-derived stem cell subpopulation and incorporated them into an injectable, photosensitive, and highly biocompatible methacrylated carboxymethyl chitosan (CMCSMA) hydrogel to investigate their therapeutic potential for promoting functional recovery after SCI and to elucidate the underlying mechanisms. METHODS: Human urine-derived stem cells (hUSCs) were initially isolated and cultured from human urine samples. The CD133(+)CD271(+) subpopulation (CD133(+)CD271(+)hUSCs) was identified and sorted using flow cytometry. Exosomes derived from this stem cell subpopulation (hUSC-sExos) were subsequently isolated from cell culture supernatants and characterized by transmission electron microscopy (TEM), nanoparticle size analysis, and Western blotting. To achieve localized sustained delivery, we developed a novel CMSCMA-sExo hydrogel composite scaffold using a photosensitive CMSCMA hydrogel as the carrier matrix and systematically evaluated its therapeutic efficacy through integrated in vivo and in vitro studies to assess microvascular regeneration, blood‒spinal cord barrier functional restoration, neural remodeling, and ultimately neurological functional recovery. RESULTS: The hUSCs were positive for CD29, CD44, CD73 and CD90 but negative for CD34 and CD45. Compared with hUSCs, the CD133(+)CD271(+)hUSC subpopulation exhibited significantly enhanced proliferative capacity and trilineage differentiation potential, indicating greater stemness characteristics. Further investigation revealed that the novel CMSCMA-sExo hydrogel composite scaffold significantly improved the tube formation and migration capacity of spinal cord microvascular endothelial cells, promoted microvascular regeneration, enhanced axonal regeneration and synaptic remodeling, and ultimately led to functional neurological recovery. CONCLUSION: The novel injectable CMSCMA-sExo hydrogel composite scaffold may represent a promising therapeutic approach for treating SCI using urine-derived stem cell subpopulation exosomes.