Utilization of IL-11 induced miRNA-27b-5p and miRNA-497-5p as potential biomarkers of cardiac fibrosis

Background—Cardiac fibrosis is a global health problem. It can be triggered, among other causes, by ischemic cardiomyopathy following infarction as well as by pressure-overload induced by aortic valve stenosis. Pathological fibrosis is brought about mostly by myofibroblasts, which cause uncontrolled extracellular matrix deposition. Interleukin-11 (IL-11) has been firmly demonstrated to be a major trigger of fibrosis. However, the mechanism underling the IL-11- mediated fibrotic response needs clarification. MicroRNAs (miRNAs) have been shown to play a central role in the pathogenesis of cardiac fibrosis. In this study we aimed to characterize the molecular mechanisms of miRNAs as downstream effectors of IL-11 and test their potential as biomarkers of cardiac fibrosis. It is extremely important for asymptomatic aortic valve stenosis (AVS) patients with preserved ejection fraction who exhibited low survival rates in 5-years time. Methods and Results—Using a bioinformatic approach, assisted by target prediction tools, we identified miRNA-497-5p and miRNA-27b-5p as potential downstream effectors of IL-11. We found an increased expression of miRNA-497-5p and miRNA-27b-5p in rat cardiac fibroblasts when exposed to exogenous IL-11 in vitro or when isolated from infarcted hearts. Moreover, transfection of each miRNA mimic was sufficient to induce fibroblast-to-myofibroblast transition and to increase the expression of collagen 1 (Col1a1), a major extracellular matrix component. Conversely, inhibition of the endogenous miRNAs attenuated Col1a1 and α-smooth muscle actin gene expression in cultured fibroblasts. We also investigated the targets of the identified miRNAs. By a dual luciferase assay, we found EGLN1 is regulated by miRNA-27b-5p. The clinical relevance of our findings was confirmed by the analysis of samples derived from AVS patients. Left ventricle specimens of these patient displayed increased fibrosis, revealed by increased collagen area and connective tissue growth factor expression. These parameters were directly associated with higher expression of miRNA-27b-5p and miRNA-497-5p in the left ventricle, peripheral blood plasma (PBP) and PBP-derived extracellular vesicles. Conclusions— miRNA-27b-5p and miRNA-497-5p mediate the profibrotic response of cardiac fibroblasts to IL-11, they are also increased in cardiac diseases which are associated with fibrosis. We believe that there is a potential to develop these miRNAs as biomarkers to guide clinical decisions.