Abstract
BACKGROUND: Cardiac fibrosis can be triggered by several pathologies, including ischemic heart disease and aortic stenosis. Cardiac fibrosis is brought about by uncontrolled ECM (extracellular matrix) deposition by myofibroblasts. IL (interleukin)-11 (Il11) has been demonstrated as a trigger of multiorgan fibrosis. However, the molecular mechanisms underpinning IL-11-induced fibrosis require further characterization. Recent studies indicate that microRNA dysregulation contributes to the pathogenesis of cardiac fibrosis and can be targeted therapeutically. This study explored the hypothesis that microRNAs act as downstream effectors of IL-11-induced cardiac fibrosis. Moreover, we investigated the translational potential of IL-11-regulated microRNAs as circulating biomarkers of cardiac fibrosis in patients with aortic stenosis. METHODS: A bioinformatic microRNA target prediction analysis was used to identify candidate microRNAs regulated by IL-11. Experimental validation was performed in cardiac fibroblasts from postinfarction failing and healthy rat hearts, after IL-11 stimulation. Functional studies assessed the effects of microRNA modulation on fibrotic gene expression in cardiac fibroblasts using microRNA inhibitor-based and mimic-based transfection. Bioinformatic analysis and luciferase assay identified candidate microRNA targets downstream of IL-11. Findings were further evaluated in transverse aortic constriction and cardiomyocyte-specific Il11-overexpression (Tg-Il11 [transgenic mouse model with cardiomyocyte-specific Il11 overexpression]) mouse models and in left ventricular tissue, peripheral plasma, and plasma extracellular vesicles from patients with aortic stenosis. RESULTS: MicroRNA-27b-5p and microRNA-497-5p were identified as novel downstream effectors of IL-11 signaling. IL-11 increased the expression of both microRNAs in cardiac fibroblasts; transfection with either microRNA inhibitor reduced, whereas microRNA mimics increased, profibrotic mRNA levels. Furthermore, microRNA-27b-5p and microRNA-497-5p converged on HIF (hypoxia-inducible factor)-1 signaling by targeting its regulator EGLN (Egl-9 family hypoxia-inducible factor). Increased microRNA levels were observed alongside reduced expression of Egln1 and Egln2 in 2 mouse models. In patients with aortic stenosis, myocardial and circulating levels of these microRNAs correlated with the severity of left ventricular fibrosis, indicating these microRNAs' potential as new circulating biomarkers of cardiac fibrosis. CONCLUSIONS: In this study, we have newly identified the potential value of microRNA-27b-5p and microRNA-497-5p as actionable biomarkers of the profibrotic response to IL-11 in the heart. Future studies should validate the translational potential of the microRNAs as new clinical biomarkers and therapeutic targets.