The relationship between myocardial fibrosis and myocardial microRNAs in dilated cardiomyopathy: A link between mir‐133a and cardiovascular events

It is unknown whether fibrosis-associated microRNAs: miR-21, miR-26, miR-29, miR-30 and miR-133a are linked to cardiovascular (CV) outcome. The study evaluated the levels of extracellular matrix (ECM) fibrosis and the prevalence of particular microRNAs in patients with dilated cardiomyopathy (DCM) to investigate any correlation with CV events. METHODS Seventy DCM patients (48 ± 12 years, EF 24.4 ± 7.4%) underwent right ventricular biopsy. The control group was comprised of 7 patients with CAD who underwent CABG and intraoperative biopsy. MicroRNAs were measured in blood and myocardial tissue via qPCR. The end-point was a combination of CV death and urgent HF hospitalization at the end of 12 months. There were differential levels of circulating and myocardial miR-26 and miR-29 as well as myocardial miR-133a when the DCM and CABG groups were compared. Corresponding circulating and myocardial microRNAs did not correlate with one another. There was no correlation between microRNA and ECM fibrosis. By the end of the 12-month period of the study, CV death had occurred in 6 patients, and a further 19 patients required urgent HF hospitalization. None of the circulating microRNAs was a predictor of the combined end-point; however, myocardial miR-133a was an independent predictor in unadjusted models (HR 1.53; 95% CI 1.14-2.05; P < .004) and adjusted models (HR 1.57; 95% CI 1.14-2.17; P < .005). The best cut-off value for the miR-133a level for the prediction of the combined end-point was 0.74 ΔCq, with an AUC of 0.67. The absence of a correlation between the corresponding circulating and myocardial microRNAs calls into question their cellular source. This study sheds new light on the role of microRNAs in ECM fibrosis in DCM, which warrants further exploration.