Expression of MicroRNA-208 is Associated with Adverse Clinical Outcomes in Human Dilated Cardiomyopathy

Background: Recently, microRNA-208 (miR-208) encoded by the alpha-myosin heavy chain (MHC) gene, has been shown to be involved in pathological cardiac growth, fibrosis, and up-regulation of beta-MHC expression. A recent study has also reported 2 additional myosin-expressed miRNAs (miR-208b and miR-499). The aim of this study was to determine whether miR-208, miR-208b, and miR-499 are expressed with MHC mRNA in human dilated cardiomyopathy (DCM), and whether these levels are related to left ventricular (LV) function and to clinical outcomes.

Methods And Results: Endomyocardial biopsy tissues were obtained from 82 patients with DCM and 21 subjects without LV dysfunction as controls. Levels of miR-208, miR-208b, and miR-499 were higher in DCM patients than in controls. Levels of alpha-MHC mRNA were lower in patients with DCM than in controls, whereas beta-MHC mRNA levels were higher in patients with DCM compared with controls. Levels of miR-208 were correlated with beta-MHC mRNA levels and myocardial collagen volume, whereas levels of miR-208b and miR-499 showed no correlation. After a mean follow-up of 517 days, an increase in miR-208 levels was shown to be a strong predictor of clinical outcomes (RR 3.4, 95% CI 1.1-11.2).

Conclusions: This study suggests that myocardial expression of miR-208 is associated with MHC mRNA expression and with poor clinical outcomes in patients with DCM. We conclude that miR-208 may therefore be involved in the progression of human DCM.