Circulating micro-RNAs as biomarkers of coronary artery disease: is it ready for primetime or still a work in progress?

MicroRNAs (miRs) are small non-coding RNAs that play a significant role in epigenetic regulation of gene expression (1,2). Several miRs have been established to play crucial roles in a spectrum of different cardiovascular diseases (3,4). Since the initial identification of detectable levels of circulating miRs in plasma (5-7), circulating miRs have become the spotlight of investigation as potential biomarkers for several diseases. Micro-RNAs in circulation have two important features of ideal biomarkers: they are remarkably stable and safe from degradation by RNases, and they are easily measured in the circulation using sensitive and specific quantitative PCR techniques. Thus, circulating miRs can be linked to specific disease processes or to specific tissue and/or cell types.