Apelin overexpression remodels aged mesenchymal stem cells to generate miR-486a-5p-enriched exosomes that drive cardiac repair

Abstract Background Mesenchymal stem cell (MSC)-based therapy has shown promising cardioprotective effects in myocardial infarction (MI), yet the therapeutic utility of aged MSCs (AMSCs) is substantially compromised by replicative senescence and functional decline during in vitro expansion. Apelin is implicated in cardiovascular homeostasis and stem cell maintenance. However, whether sustained Apelin signaling can preserve the proliferative capacity and paracrine functionality of AMSCs during extended culture remains incompletely understood. Methods Mouse AMSCs were genetically modified to overexpress Apelin (AMSCs Apelin ) or an empty control vector (AMSCs NC ). Cellular proliferation, senescence, and multipotent differentiation were assessed across passages. Single-cell RNA sequencing (scRNA-seq) was performed to characterize Apelin -associated changes in cellular composition. Exosomes derived from these cells (Exo-AMSCs Apelin , Exo-AMSCs NC , and Exo-AMSCs) were isolated and characterized, and their uptake and cytoprotective effects were evaluated in H9c2 cells and HUVECs under hypoxia/serum deprivation in vitro. Therapeutic efficacy was further assessed in a mouse MI model. Exosomal miRNA sequencing and functional assays were used to identify and validate key miRNAs mediating the therapeutic effects. Results Apelin overexpression preserved the proliferative capacity and differentiation potential of AMSCs while attenuating replicative senescence during extended culture. scRNA-seq analysis revealed that Apelin selectively expanded subpopulations enriched for proliferative features and exosome biogenesis–associated gene programs in AMSCs Apelin . Correspondingly, exosomes derived from AMSCs Apelin displayed increased secretion yields, enhanced uptake efficiency and superior cytoprotective effects in vitro. In vivo, administration of Exo-AMSCs Apelin significantly improved cardiac function, reduced fibrotic remodeling, and enhanced neovascularization following MI. miRNA profiling identified miR-486a-5p as the most enriched miRNA in Exo-AMSCs Apelin , and functional assays demonstrated that miR-486a-5p modulated cardiomyocyte survival and endothelial angiogenic responses, at least in part through suppressing Pten . Conclusion Apelin reprograms the cellular composition of aged MSCs and enhances the quantitative and qualitative properties of their secreted exosomes. This coordinated regulation promotes the generation of miR-486a-5p–enriched exosomes with augmented cardioprotective capacity. These findings identify Apelin as a key regulator of the cellular–paracrine axis in aged MSCs and provide a rationale for optimizing MSC-derived exosome–based strategies for cardiac repair.