Dynamic Regulation of MicroRNAs in Cardiac Fibroblasts upon Activation

Abstract

Remodeling is a common feature in cardiac disease, which entails fibroblast activation and often leads to fibrosis. MicroRNAs (miRs) are novel regulators in cardiac remodeling. In contrast to myocytes, very little is known about miRs in cardiac fibroblasts. In this study, we established the miR expression profile in adult rat ventricular fibroblasts and assessed their dynamic changes upon fibroblast activation, using high throughput TaqMan miR arrays and a culture model that mimics the phenotypic and functional changes of cardiac fibroblasts in the diseased heart. Among 518 miRs included in the arrays, 180 miRs were detected and 52 miRs were more than 4‐fold up‐ or down‐regulated upon fibroblast activation. Cardiomyocyte‐restricted miR‐208 was undetectable, indicating lack of myocyte contamination. MiR‐21, a well‐studied miR in cardiac fibroblasts and fibrosis development, was increased 3.1‐fold upon fibroblast activation, which is consistent with a 5‐fold up‐regulation reported in fibroblasts from failing hearts. We identified several previously unidentified miRs in cardiac fibroblasts. One of them is miR‐1, which has been extensively studied in myocytes. Using gain‐ and loss‐of function approaches and 3′UTR luciferase assays, we detected a novel role for miR‐1 as negative regulator of fibroblast proliferation via a mechanism that involves direct targeting of key cell cycle regulators (cyclin D1, cyclin D2 and CDK6). Together, our data suggest dynamic regulation of miR‐1 and other miRs in cardiac fibroblasts that regulate fibroblast activation and function. (The work is supported by an IDeA grant P20GM103652 from the NIH/NIGMS)