The emerging role of microRNA in stroke.

MicroRNAs (miRNAs) are small non-coding RNAs approximately 22 nucleotides in length that play a pivotal role in post-transcriptional gene regulation by binding to complementary sites in the 3'-untranslated region of messenger RNAs. In the past decade, their role in several human diseases, from cancer to cardiovascular disease, has been established by a wealth of evidence. Stroke is responsible for 10% of deaths worldwide and is one of the leading causes of disability. MiRNAs are involved in stroke risk factors including hypertension, atherosclerosis, atrial fibrillation, diabetes and dyslipidemia. The role of miRNAs in the pathophysiology of stroke has been the subject of more recent investigations. Animal studies, which dominate the field, have demonstrated the differential expression of miRNAs in brain and blood following ischemic or hemorrhagic insult and the potential use of miRNA antagonists to reduce focal cerebral damage. In particular, antagomirs to miR-145, -497, -181a, -1 and let-7f have been found to be neuroprotective in vivo. The discovery of circulating miRNAs in peripheral blood, which are unexpectedly stable, has allowed the recent completion of several studies in human stroke patients that have confirmed the differential expression of specific miRNAs following stroke and have addressed their potential use as diagnostic and prognostic markers. With miRNA research in stroke still in its infancy, it is anticipated that in the next few years significant discoveries that may have important therapeutic implications will emerge.