Implantable Microsphere-Mediated Targeted Delivery of Mesenchymal Stem Cell-Derived Extracellular Vesicles Attenuates Neuroinflammation and Promotes Recovery After Cerebral Ischemia.
BACKGROUND Ischemic stroke is a major cause of death and disability, in which neuroinflammation exacerbates injury. Mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) offer therapeutic potential but face translational hurdles in scalable production, rapid systemic clearance, and inefficient targeted delivery. METHODS We engineered an implantable alginate-microsphere system encapsulating EV-secreting MSCs and displaying the RGD-4C peptide (ACDCRGDCFC) on its surface. This platform functions as a bioreactor that sustains the release of functionalized EVs with enhanced targeting to the ischemic brain. Proteomics analyses compared EVs derived from 3D-microsphere cultures and conventional 2D cultures. Efficacy was evaluated in a mouse stroke model with intraperitoneal microsphere implantation, assessing biodistribution, neuroinflammation, microglial polarization, and recovery. RESULTS The system sustained the release of targeted EVs, demonstrating proteomic enrichment of anti-inflammatory cargo. In vivo, the platform enhanced EV accumulation in the ischemic brain, reduced neuroinflammation, shifted microglia toward a reparative phenotype, and significantly improved neuronal survival and functional recovery. CONCLUSION This integrated platform represents a promising preclinical strategy for treating ischemic stroke and has potential applications in other neuroinflammatory diseases. This system circumvents the need for EV extraction and storage while eliminating the peak-and-trough kinetics of bolus injections, and suggests potential for future translation pending further validation.