MicroRNA miR-1 is up-regulated in remote myocardium in patients with myocardial infarction.

MicroRNAs are small regulatory RNA molecules that mediate regulation of gene expression, thus affecting a variety of physiological, developmental and pathological conditions. They are believed to be new promising therapeutic targets. In recent studies two muscle-specific microRNAs were discovered to contribute to heart diseases and development: miR-1 and miR-133, but there is little data on their expression patterns in human myocardial infarction. We performed simultaneous expression analysis of miR-1, miR-133a, miR-133b in samples of infarcted tissue and remote myocardium from twenty- four patients with acute myocardial infarction. MicroRNA expression was analysed using quantitative real-time PCR and compared to the expression patterns in myocardium of eight healthy adults who died in accidents. We found ~3.8-fold miR-1 up-regulation in remote myocardium when compared to infarcted tissue or healthy adult hearts. As miR-1 has been shown in animal models and clinical studies to contribute to arrhythmogenesis by regulating pacemaker channel genes, our finding of miR-1 up-regulation in patients with myocardial infarction indicates that it might be responsible for the higher risk for arrhythmias in these patients. In addition, miR-133a/b down-regulation in infarcted tissue and remote myocardium was observed, indicating miR-133a/b involvement in the heart response to myocardial infarction. We conclude that miR-1 and miR-133 seem to be important regulators of heart adaptation after ischaemic stress.