miR-543 in human mesenchymal stem cell-derived exosomes promotes cardiac microvascular endothelial cell angiogenesis after myocardial infarction through COL4A1.

OBJECTIVE To explore the impact and mechanism of human mesenchymal stem cells (hMSCs) on the angiogenesis of cardiac microvascular endothelial cells (CMECs) after ischemia insult. METHODS Exosomes derived from hMSCs (hMSCs-Exo) were identified by Western blotting and labeled by PHK-67. CMECs were isolated from rat myocardial tissues. After hypoxic treatment, CMECs were cultured with hMSCs and exosome inhibitor (GW4869), or transfected with si-COL4A1 + miR-543 inhibitor. CMEC proliferation, migration, invasion and angiogenesis were examined. Target genes of miR-543 were predicted and then were identified by dual luciferase assay. Myocardial infarction (MI) rat model established by suture occlusion was intravenously injected with hMSCs-Exo. Fluorescence microscope was applied to visualize exosomes in myocardial tissues. Infarction volume and pathologies of myocardial tissues were observed. Ki-67 and miR-543 expressions were detected. RESULTS The isolated hMSC-Exo expressed TSG101, HSP70 and CD63. Hypoxia-treated CMECs cultured with hMSCs exhibited high proliferation, migration, invasion and angiogenesis ability, while incubation with exosome inhibitor GW4969 offset the promoting effects of hMSCs on the proliferation, migration, invasion and angiogenesis of CMECs. hMSCs transfected with miR-543 inhibitor brought CMECs weak viability and angiogenesis ability. CMECs transfected with si-COL4A1 and miR-543 inhibitor showed low proliferation, migration, invasion and angiogenesis compared to those transfected with si-COL4A1 alone. hMSCs-Exo entered the myocardial tissues of MI rats. Injection of hMSCs-Exo in MI rats diminished infarction size, attenuated MI-induced injuries and increased Ki-67 expression. CONCLUSION hMSCs-Exo facilitates the proliferation, migration, invasion and angiogenesis of CMECs through transferring miR-543 and downregulating COL4A1 expression.