Long Noncoding RNA H19 Acts as a Competing Endogenous RNA to Mediate CTGF Expression by Sponging miR-455 in Cardiac Fibrosis.

Cardiac fibrosis is closely related to multiple cardiovascular system diseases, and noncoding RNAs (ncRNAs), including long noncoding RNA (lncRNA) and microRNA (miRNA), have been reported to play a vital role in fibrogenesis. The present study aims to investigate the potential regulatory mechanism of lncRNA H19 and miR-455 on fibrosis-associated protein synthesis in cardiac fibroblasts (CFs). miRNA microarray assay revealed 34 significantly dysregulated miRNAs, including 13 upregulated miRNAs and 21 downregulated miRNAs. Among these aberrantly expressed miRNAs, we paid attention to miR-455, which was significantly downregulated in diabetic mouse myocardium and Ang II-induced CFs. Loss- and gain-of-function experiments showed that miR-455 expression levels were negatively correlated with collagen I and III expression in Ang II-induced CFs. Bioinformatic prediction programs (TargetScan, miRanda, starBase) predicted that miR-455 targeted connective tissue growth factor (CTGF) and H19 with complementary binding sites at the 3'-untranslated region, which was validated by luciferase reporter assay. Functional validation assay demonstrated that H19 knockdown could enhance the antifibrotic role of miR-455 and attenuate the CTGF expression and further decrease fibrosis-associated protein synthesis (collagen I, III, and α-SMA). The present study reveals a novel function of the H19/miR-455 axis targeting CTGF in cardiac fibrosis, suggesting its potential therapeutic role in cardiac diseases.