Down-regulation of miR-133a/b in patients with myocardial infarction correlates with the presence of ventricular fibrillation

MicroRNAs (miRNAs) are important regulators of physiologic and pathologic conditions of the heart. Animal models of heart diseases have shown that miRNAs may contribute to the development of arrhythmias. However, little is known about the expression of muscle-and cardiac-specific miRNAs in patients with myocardial infarction (MI) who have developed ventricular fibrillation (VF). Our study included 47 patients who had died from myocardial infarction (MI), 23 with clinically proven VF and 24 without VF. Autopsy samples of infarcted tissue and remote myocardium were available (n=94). Heart tissue from 8 healthy trauma victims was included as control. Expression of miR-1, miR-133a/b and miR-208 was analyzed using real-time PCR (qPCR). In patients with MI with VF, we observed down-regulation of miR-133a/b, and this down-regulation was even stronger 2-7 days after MI. miR-208 was up-regulated in remote myocardium irrespective of the presence of VF. Deregulation of miR-1 and miR-208 was not related to the presence of VF. Our results suggest that down-regulation of miR-133a/b might contribute to the development of VF in patients with MI. However, up-regulation of miR-1 and miR-208 in remote myocardium might play a role in cardiac remodeling after MI, at least to certain degree.