3D‐cultured BMSC exosomes improve cerebral ischemia/reperfusion injury‐induced neuronal apoptosis by regulating the microglia polarization

Abstract Microglial activation is a key driver of neuroinflammation following cerebral ischemic reperfusion injury (CIRI). Exosomes (Exo) derived from bone marrow mesenchymal stem cells (BMSCs) can regulate microglia, causing a transition from the pro‐inflammatory M1 phenotype to the anti‐inflammatory M2 phenotype, thereby reducing neuronal apoptosis in post‐reperfusion injuries. However, the generation of superior‐quality exosomes remains a significant hurdle in this field. We performed three‐dimensional (3D) cultivation of BMSCs using a gelatin methacryloyl (GelMA) hydrogel and collected the released exosomes. We conducted experiments using lipopolysaccharide (LPS)‐induced BV2 cells, oxygen‐glucose deprivation/reoxygenation (OGD/R)‐ induced HT22 cells, and CIRI mice to verify the effects of 3D‐cultured exosomes in regulating microglial activation and alleviating neuronal apoptosis. Based on the cellular and animal experiments, we successfully demonstrated the remarkable efficacy of exosomes derived from 3D‐cultured BMSC using a GelMA hydrogel in the context of CIRI. These exosomes effectively mitigated the conversion of microglia to the inflammatory phenotype and facilitated their transition to the anti‐inflammatory phenotype, thereby reducing aseptic inflammatory reactions and neuronal apoptosis. This study demonstrated the effectiveness of GelMA‐based 3D‐cultured exosomes in treating CIRI and introduced innovative concepts and opportunities for addressing this condition with clinical applications.