MicroRNAs in cardiac disease.

MicroRNAs (miRs) are transcriptionally regulated single-strand RNAs that depress protein expression through posttranscriptional mRNA silencing. A host of recent studies have established essential roles for miRs in cardiac development and cardiac health. Regulated myocardial miR expression is observed in a variety of cardiac syndromes, and serum miR levels are being evaluated as disease biomarkers. The manipulation of miR levels in mouse hearts using genetic techniques or engineered miR mimetics and antagonists is elucidating the roles of specific cardiac miRs in cardiac development, and in the cardiac response to injury or stress, and heart disease. The ability to target multiple factors within a single biological response pathway by a given miR has prompted the development of small miR-targeting molecules that can be readily delivered and have sustained in vivo effects. These advances establish a foundation for novel diagnostics and new therapeutic approaches for myocardial infarction, cardiac hypertrophy, and heart failure.