Should we expect novel biomarkers of myocardial infarction?

Recent studies have revealed important roles for microRNAs (miRNAs) in cardiovascular disease, including acute myocardial infarction (AMI). miRNAs are small, 20–25 nucleotides long, non-coding RNA molecules, which inhibit gene expression by promoting mRNA degradation or preventing translation (1,2). Although the biological functions of miRNAs are not fully understood, numerous studies have shown that some miRNAs have unique expression profiles in certain tissues or cell types (3). Recent discoveries have revealed the existence of freely circulating, stably expressed miRNAs in human blood cells or plasma/serum (4,5). The circulating miRNAs have been shown to be sensitive and informative biomarkers in the diagnosis of cardiovascular diseases. The article by Yao and colleagues (6) describes circulating miRNA-122-5p as a potential novel biomarker for diagnosis of acute myocardial infarction. In that study, the authors investigated the level of miRNA-122-5p by quantitative real-time PCR (RT-qPCR) and found that its expression was up-regulated at 4, 8, 12, and 24 h in AMI patients compared to non-AMI controls, and displayed similar trends to the cTnI concentrations. A high correlation was observed between the circulating miR-122-5p and cTnI concentrations. The receiver operating characteristic (ROC) curve analysis showed that miRNA-122-5p in plasma had considerable diagnostic accuracy for AMI with an area under curve (AUC) of 0.855. The results suggest that miRNA-122-5p could leak from cardiac myocytes into the circulation during the early stages of AMI