MicroRNAs challenge the status quo of therapeutic targeting.

MicroRNAs (miRNAs) are recently discovered posttranscriptional regulators of gene expression that have become a cause célèbre. There are currently more than 600 miRNAs identified in humans that are estimated to regulate about one third of all messenger RNA (mRNA). Because miRNA levels were found widely deregulated in diseases, they have been implicated in the underlying pathogenesis. In addition, the changes in their expression patterns are proving to be reliable diagnostic and prognostic measures. But the specific mRNA targets and, hence, function of each miRNA is still work-in-progress. This information would be necessary before fully exploiting miRNA for therapeutic purposes. In this review we will discuss why miRNAs are considered major posttranscriptional regulators and how they impact gene expression and cell function during cardiac hypertrophy and failure. In addition, we will highlight their potential for therapeutic targeting.