Xun Hu

Accumulating evidence has shown that endothelial progenitor cell‐derived exosomes (EPC‐Exos) can ameliorate myocardial fibrosis. The purpose of the present study was to investigate the effects of EPC‐Exos‐derived microRNAs (miRNAs) on myocardial infarction (MI). A miRNA‐Seq dataset of miRNAs differentially expressed between EPCs and exosomes was collected. Quantitative real‐time polymerase chain reaction (qRT‐PCR) was used to validate the miRNA expression indicated by miRNA‐Seq. Immunofluorescence, cell proliferation, and angiogenesis assays were employed to investigate the effects of miRNAs on cardiac fibroblasts (CFs) in vitro. Interactions between miRNAs and their respective targets were examined via immunoblotting, qRT‐PCR, and luciferase reporter assays. An MI rat model was constructed, and various staining and immunohistochemical assays were performed to explore the mechanisms underlying the miRNA‐mediated effects on MI. miR‐363‐3p and miR‐218‐5p were enriched in EPC‐Exos, and miR‐218‐5p and miR‐363‐3p mimic or inhibitor enhanced or suppressed CF proliferation and angiogenesis, respectively. miR‐218‐5p and miR‐363‐3p regulated p53 and junction‐mediating and regulatory protein (JMY) by binding to the promoter region of p53 and the 3 ^′ untranslated region of JMY. Additionally, treatment of CFs with Exo‐miR‐218‐5p or Exo‐miR‐363‐3p upregulated p53 and downregulated JMY expression, promoted mesenchymal‐endothelial transition, and inhibited myocardial fibrosis. Administration of exosomes containing miR‐218‐5p mimic or miR‐363‐3p mimic ameliorated left coronary artery ligation‐induced MI and restored myocardial tissue integrity in the MI model rats. In summary, these results show that the protective ability of EPC‐Exos against MI was mediated by the shuttled miR‐218‐5p or miR‐363‐3p via targeting of the p53/JMY signaling pathway.

Myocardial fibrosis is a common pathophysiological change in cardiovascular disease, which can cause cardiac dysfunction and even sudden death. Excessively activated fibroblasts proliferate and secret excessive extracellular matrix (ECM) components, resulting in normal cardiac structural damage and cardiac fibrosis. We previously found that human endothelial progenitor cell (EPC)-derived exosomes, after hypoxia/reoxygenation (H/R) induction, could significantly increase the mesenchymal-endothelial transition (MEndoT) compared to normal culture EPC-derived exosomes. Exosomes have been shown to carry different nucleic acids, including microRNAs. However, the effects of microRNAs in EPC-derived exosomes on MEndoT and myocardial fibrosis remain unknown. EPCs were isolated from human peripheral blood, and fibroblasts were isolated from rat hearts, then transfected with miR-133 inhibitor, si-YBX-1, and ov-YBX-1 into EPCs. After H/R induction for 48 h, isolation and characterization of exosomes derived from human EPCs were performed. Finally, fibroblasts were treated by exosome at 48 h. The expression of miR-133 was measured by qRT-PCR; YBX-1 expression was measured by qRT-PCR and western blot. Angiopoiesis was measured by tube formation assay. Endothelial markers and fibrosis markers were measured by western blot. H/R treatment promoted miR-133 expression in EPCs and EPC-derived exosomes. miR-133 could be incorporated into exosomes and transmitted to cardiac fibroblasts, increasing the angiogenesis and MEndoT of cardiac fibroblasts. miR-133 silencing in H/R-induced EPCs could inhibit miR-133 expression in EPCs and EPCs-derived exosomes. miR-133 silencing in H/R-induced EPCs could inhibit the angiogenesis and MEndoT of cardiac fibroblasts and reverse the effect of H/R treatment. Additionally, miR-133 was specially sorted into H/R-induced EPC-derived exosomes via YBX-1. YBX-1 silencing inhibited miR-133 transfer and reduced fibroblast angiogenesis and MEndoT. miR-133 was specially sorted into H/R-induced EPC-derived exosomes via YBX-1 to increase fibroblast angiogenesis and MEndoT.