MicroRNA-101 Inhibited Postinfarct Cardiac Fibrosis and Improved Left Ventricular Compliance via the FBJ Osteosarcoma Oncogene/Transforming Growth Factor-β1 Pathway

Background-Cardiac interstitial fibrosis is a major cause of the deteriorated performance of the heart in patients with chronic myocardial infarction. MicroRNAs (miRs) have recently been proven to be a novel class of regulators of cardiovascular diseases, including those associated with cardiac fibrosis. This study aimed to explore the role of miR-101 in cardiac fibrosis and the underlying mechanisms. Methods and Results-Four weeks after coronary artery ligation of rats, the expression of miR-101a and miR-101b (miR-101a/b) in the peri-infarct area was decreased. Treatment of cultured rat neonatal cardiac fibroblasts with angiotensin II also suppressed the expression of miR-101a/b. Forced expression of miR-101a/b suppressed the proliferation and collagen production in rat neonatal cardiac fibroblasts, as revealed by cell counting, MTT assay, and quantitative reverse transcription-polymerase chain reaction. The effect was abrogated by cotransfection with AMO-101a/b, the antisense inhibitors of miR-101a/b. c-Fos was found to be a target of miR-101a because overexpression of miR-101a decreased the protein and mRNA levels of c-Fos and its downstream protein transforming growth factor-beta 1. Silencing c-Fos by siRNA mimicked the antifibrotic action of miR-101a, whereas forced expression of c-Fos protein canceled the effect of miR-101a in cultured cardiac fibroblasts. Strikingly, echocardiography and hemodynamic measurements indicated remarkable improvement of the cardiac performance 4 weeks after adenovirus-mediated overexpression of miR-101a in rats with chronic myocardial infarction. Furthermore, the interstitial fibrosis was alleviated and the expression of c-Fos and transforming growth factor-beta 1 was inhibited. Conclusion-Overexpression of miR-101a can mitigate interstitial fibrosis and the deterioration of cardiac performance in postinfarct rats, indicating the therapeutic potential of miR-101a for cardiac disease associated with fibrosis. (Circulation. 2012;126:840-850.)