ATP2A2 and miRNA in human myocardial infarction

Cardiac sarco(endo)plasmic reticulum calcium ATPase-2 (SERCA2) plays one of the central roles in myocardial contractility. Both, SERCA2 mRNA and protein are reduced in myocardial infarction (MI), but the correlation has not been always observed. MicroRNAs (miRNAs) act by targeting 3'-UTR mRNA, causing translational repression in physiological and pathological conditions, including cardiovascular diseases. The aim of our study was to identify miRNAs that could influence SERCA2 expression in human MI. The protein SERCA2 was decreased and 43 miRNAs were deregulated in infarcted myocardium compared to remote myocardium. miRNAs binding prediction to SERCA2 identified 213 putative miRNAs. TAM and miRNApath identified 18 functional and 21 diseased states related to heart diseases. Combing all results, we identified certain miRNAs as potential regulators of SERCA2. All the samples were stored as FFPE tissue and in RNAlater. Expression of SERCA2 was analyzed by western blot and miRNA expression was analyzed by microarrays and qPCR in samples of remote and infarcted myocardium from 6 patients who died of MI. Bioinformatic analysis including six prediction programmes (TargetScan, PicTar, miRBase, miRDB, Human MicroRNA Targets, and microrna.org), TAM and miRNApath annotation, and free-energy of binding (RNA22, RNAfold), was performed. Nine up-regulated miRNAs were analyzed for free-energy of binding and flanking regions, and nine miRNAs were used for validation with qPCR. Based on qPCR the comparison between FFPE and RNAlater as well as different reference genes was also performed.