Small changes can make a big difference - microRNA regulation of cardiac hypertrophy.

Cardiac hypertrophy is a thickening of the heart muscle that results in enlargement of the ventricles, which is the primary response of the myocardium to stress or mechanical overload. Cardiac pathological and physiological hemodynamic overload causes enhanced protein synthesis, sarcomeric reorganization and density, and increased cardiomyocyte size, all culminating into structural remodeling of the heart. With clinical evidence demonstrating that sustained hypertrophy is a key risk factor in heart failure development, much effort is centered on the identification of signals and pathways leading to pathological hypertrophy for future rational drug design in heart failure therapy. A wide variety of studies indicate that individual microRNAs exhibit altered expression profiles under experimental and clinical conditions of cardiac hypertrophy and heart failure. Here we review the recent literature, illustrating how single microRNAs regulate cardiac hypertrophy by classifying them by their prohypertrophic or antihypertrophic properties and their specific effects on intracellular signaling cascades, ubiquitination processes, sarcomere composition and by promoting inter-cellular communication.