CBSCs Derived Extracellular Vesicles Modify the Immune Response After Cardiac Ischemic Injury to Enhance Repair

Introduction: Few therapies have produced significant improvement in cardiac function after ischemic cardiac injury (ICI). The activation of local inflammatory responses is critical to cardiac repair after ICI. Our previous studies showed that cortical bone derived stem cells (CBSCs) possess can enhance repair after ICI. Beneficial effects of CBSCs appear to be mediated by paracrine factors including extracellular vesicles (EVs). This study explored if and how these EVs enhance cardiac repair by modulating the ICI immune response. Hypothesis: CBSCs derived extracellular vesicles (CBSC-EV) modulate immune response after ICI. Methods and Results: Both CBSCs and CBSC-EV were transplanted into mice after myocardial infarction (MI). CBSCs and CBSC-EV treated animals had better ICI repair compared with Saline, with reduced scar size, attenuated structural remodeling, improved cardiac function, and reduced cell apoptosis. These effects were linked to alteration of immune response. Plasma analysis of CBSCs and CBSC-EV treated animals showed significantly lower level of pro-inflammatory cytokines such as TNFα 24 hours after MI. CBSCs and CBSC-EV treatment induced significant polarization from CD86+ M1 macrophages towards CD206+ M2 macrophages phenotype 5 days post-MI, with subsequent reduction of CD8+ T cells and increase of CD4+ T cells, especially the FoxP3+ Treg population, from 7 days to 14 days post-MI. RNA sequencing analysis revealed that CBSC-EV contained a distinct transcriptome compared with endothelial progenitor cells and cardiosphere-derived cells. Gene Ontology analysis suggested the differentially expressed genes in CBSC-EV significantly enriched in immune cell receptor binding. MiR-182 and miR-183, which ranked top of the most significantly upregulated genes in CBSC-EV, attenuated M1 macrophage polarization after LPS treatment and promote CD25+ FoxP3+ Treg differentiation in vitro. Conclusions: CBSC-EV enhance cardiac repair by modulating the immune response after injury and highlight the molecular bases of into the beneficial effects of cell-free therapy after ICI.