Abstract: Ischemic stroke remains a leading cause of disability and death, with mesenchymal stem cell–derived exosomes emerging as a promising therapeutic avenue. However, the optimal timing and underlying therapeutic mechanisms of exosome treatment require further elucidation. In this study, we used a murine model of middle cerebral artery occlusion to investigate the therapeutic efficacy of human umbilical cord mesenchymal stem cell–derived exosomes administered intravenously at an early (6 hours) or delayed (3 days) time point post-ischemia. Compared with delayed treatment, early administration of exosomes resulted in significantly superior efficacy, as evidenced by improved neurological function scores and reduced infarct volumes. Transcriptomic analysis of brain tissues from mice receiving early exosome treatment revealed marked downregulation of inflammation-related genes, including Ccl2, Ccl5, Cxcl10, Il-1β , Il-6, Itgam, Itgax, and Tnf-α. Metabolomic profiling of these brain tissues further identified modulation of key metabolites, including trimethylamine N-oxide, glutathione, 1-stearoyl-rac-glycerol, and phosphatidylcholine, suggesting that alteration of metabolic pathways contributes to the therapeutic effect. Integrated transcriptomic and metabolomic analysis pinpointed significant modulation of pathways involving metabolism of eicosapentaenoic acid, lysine, propanoate, and tyrosine. These findings suggest that umbilical cord mesenchymal stem cell–derived exosomes, particularly when administered early post-ischemia, exert their neuroprotective effects by broadly suppressing inflammatory pathways and modulating key metabolic processes in the ischemic brain, highlighting their potential as a therapeutic intervention for ischemic stroke.

Key words: exosomes, ischemic stroke, mesenchymal stem cells, metabolomics, middle cerebral artery occlusion, stroke, transcriptomics