MicroRNA-145 Regulates Vascularity By Directly Targeting EIF4B After Myocardial Infarction

BackgroundEarly reperfusion strategy after acute myocardial infarction?AMI?is able to save the ischemic myocardium.But it may also lead to coronary microcirculation dysfunction,including reduction of cardiac microvascular density?CMD?.ObjectiveTo investigate the role of micro RNA-145?miR-145?in angiogenesis after AMI and its underlying mechanism.MethodsFirstly,miR-145 in human umbilical vein endothelial cells?HUVECs?under CoCl₂-induced hypoxia was detected by miRNA qRT-PCR.After miR-145 transfection,endothelial cell proliferation,migration,survival and angiogenesis was respectively evaluated by EdU incoporation assay,Scratch assay or Transwell chamber,Annexin V/PI immunostaining and Tube Formation on Matrigel.MiR-145 binding site at eukaryotic translation initiation factor 4B?eIF4B?3'UTR was predicted by bioinformatic softwares,then validated by dual Luciferase reporter assay.Following eIF4B siRNA,as well as miR-145 transfection in hypoxia,eIF4B and downstream c-Myc,Hif1?,Vegfa and anti-apoptotic factor,Bcl2were assessed by Western blot.AMI mice were intramyocardially injected with purified miR-145 interfering adenoviruses for 2 weeks,then cardiac function was measured by M-mode echocardiography.Finally,cardiac microvascular density,endothelial cell?CMEC?proliferation and survival were detected by immunofluorescence staining.ResultsThe endothelial small noncoding RNA miR-145 was persistently down-regulated in 200?M CoCl₂-induced hypoxia?P<0.05?.Compared to scrRNA,agomi R-145 inhibited endothelial cell proliferation,migration,survival and network formation on Matrigel,while antagomi R-145 showed the opposite effect?P<0.05?.MiR-145 directly targeted eIF4B 3'UTR,which was identified by bioinformatic prediction and validated by dual Luciferase reporter assay?P<0.05?.After eIF4B siRNA,as well as agomi R-145 transfection,eIF4B and downstream c-Myc,Hif1?,Vegfa and Bcl2 proteins were decreased,while antagomiR-145 upregulated all of them?P<0.05?.Meanwhile,CMEC proliferation,capillary and arteriolar densities of miR-145 knockdown mice were apparently increased,and cardiac function was ameliorated when compared to control group?P<0.05?.ConclusionMi R-145 regulates endothelial cell proliferation,migration,survival and angiogenesis through modulating eIF4B and downstream c-Myc/Hif1?signaling and anti-apoptosis factor Bcl2,which may provide a suitable and promising intervention for ischemic heart disease.