title: Overexpression of microRNA-99a attenuates heart remodelling and improves cardiac performance after myocardial infarction.
abstract: MicroRNAs are involved in the regulation of various cellular processes, including cell apoptosis and autophagy. Expression of microRNA-99a (miR-99a) is reduced in apoptotic neonatal mice ventricular myocytes (NMVMs) subjected to hypoxia. We hypothesize that miR-99a might restore cardiac function after myocardial infarction (MI) by up-regulation of myocyte autophagy and apoptosis. We observed down-regulated miR-99a expression in NMVMs exposed to hypoxia using TaqMan quantitative reverse transcriptase-polymerase chain reaction analysis (RT-PCR). We also observed that miR-99a overexpression decreased hypoxia-mediated apoptosis in cultured NMVMs. To investigate whether overexpression of miR-99a in vivo could improve cardiac function in ischaemic heart, adult C57/BL6 mice undergoing MI were randomized into two groups and were intra-myocardially injected with lenti-99a-green fluorescent protein (GFP) or lenti-GFP (control). Four weeks after MI, lenti-99a-GFP group showed significant improvement in both left ventricular (LV) function and survival ratio, as compared to the lenti-GFP group. Histological analysis, western blotting analysis and electron microscopy revealed decreased cellular apoptosis and increased autophagy in cardiomyocytes of lenti-99a-GFP group. Furthermore, western blotting analysis showed inhibited mammalian target of rapamycin (mTOR) expression in the border zones of hearts in miR-99a-treated group. Our results demonstrate that miR-99a overexpression improves both cardiac function and survival ratio in a murine model of MI by preventing cell apoptosis and increasing autophagy via an mTOR/P70/S6K signalling pathway. These findings suggest that miR-99a plays a cardioprotective role in post-infarction LV remodelling and increased expression of miR-99a may have a therapeutic potential in ischaemic heart disease.
authors.affiliation: Department of Cardiology, Drum Tower Clinical Medical Hospital, Nanjing Medical University, Nanjing, China.
authors.forename: Qiaoling
authors.initials: Q
authors.lastname: Li
authors.forename: Jun
authors.initials: J
authors.lastname: Xie
authors.forename: Ruotian
authors.initials: R
authors.lastname: Li
authors.forename: Jian
authors.initials: J
authors.lastname: Shi
authors.forename: Jiayin
authors.initials: J
authors.lastname: Sun
authors.forename: Rong
authors.initials: R
authors.lastname: Gu
authors.forename: Liang
authors.initials: L
authors.lastname: Ding
authors.forename: Lian
authors.initials: L
authors.lastname: Wang
authors.forename: Biao
authors.initials: B
authors.lastname: Xu
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000235:genetics; D001343:Autophagy / Q000235:genetics; D015687:Cell Hypoxia / Q000235:genetics; D048429:Cell Size; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005822:Genetic Vectors / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006352:Heart Ventricles / Q000473:pathology / Q000503:physiopathology; D016086:Lentivirus / Q000378:metabolism; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000235:genetics* / Q000503:physiopathology* / Q000601:surgery; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology; D009210:Myofibrils / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D016019:Survival Analysis; D014463:Ultrasonography; D020257:Ventricular Remodeling / Q000235:genetics*
chemical_list: D035683:MicroRNAs; C573158:Mirn99 microRNA, mouse; D049452:Green Fluorescent Proteins
keywords: apoptosis; autophagy; gene therapy; ischaemic heart disease; microRNA