Circulating miRNAs: reflecting or affecting cardiovascular disease?

MicroRNAs are a class of small, noncoding RNAs encoded by the metazoan genome that regulate protein expression. A collection of studies point to vital roles for microRNAs in the onset and development of cardiovascular diseases. So far, microRNAs have been considered as important intracellular mediators in maintaining proper cardiac function and hemostasis, and have been proposed as potential therapeutic targets in cardiovascular disease. The recent discovery that microRNAs circulate in a stable form in many body fluids, including blood, suggests that circulating microRNAs can serve as a new generation of biomarkers for cardiovascular diseases. In this review, we summarize the findings of studies focusing on circulating microRNAs present in human blood cells or plasma/serum, where they potentially could serve as diagnostic or prognostic markers for a variety of cardiovascular pathologies, including acute myocardial infarction, heart failure, coronary artery disease, stroke, diabetes and hypertension. The significance and limitations of microRNAs as the new biomarker generation for cardiovascular disease are also discussed.