Stage-Associated Efficacy of Systemically Administered Neural Stem Cell-Derived Exosomes in Ischemic Stroke through the Prevention of Cx43 Degradation

Ischemic stroke pathology is highly dynamic, making the optimal timing for biological interventions highly elusive. This study investigated the stage-associated therapeutic efficacy of neural stem cell-derived exosomes (NSC-Exos) for cerebral ischemia–reperfusion. The in vivo evaluations identified a restricted therapeutic window closely associated with the temporal evolution of the ischemic microenvironment. Early exosome intervention (4 or 24 h post-ischemia) significantly reduced infarct volume, restored blood–brain barrier integrity, and improved neurological functional recovery. In contrast, delayed administration (48 h) failed to reduce the mortality rate and provide meaningful neuroprotection. To examine the molecular basis of this time dependence, we integrated temporal proteomic profiling of the ischemic penumbra with small RNA sequencing of NSC-Exos. The analytical and functional data suggest that early NSC-Exo delivery transfers miR-9-5p to suppress Nedd4 expression, thereby restoring the Connexin 43 protein pool and stabilizing the astrocytic network to halt initial microenvironmental collapse. Collectively, this study underscores the critical importance of intervention timing and provides a potential translational strategy for utilizing NSC-Exos as a targeted, stage-specific therapy in acute ischemic stroke.