MiR-154 directly suppresses DKK2 to activate Wnt signaling pathway and enhance activation of cardiac fibroblasts.

Abstract

Excessive proliferation of cardiac fibroblasts (CFs) and their transdifferentiation into myofibroblasts leads to expression of α-smooth muscle actin (α-SMA), as well as excessive synthesis and secretion of collagens. This process represents an important pathological basis for myocardial fibrosis (MF). MicroRNA (miR)-154 and the Wnt signaling pathway play key roles in the above process, although their specific interactions are poorly understood. After transfecting CFs with miR-154 mimics or inhibitors, miR-154 was found to inhibit the expression of Dickkopf-related protein 2 (DKK2), while miR-154 inhibitors upregulated DKK2 expression in a Western blot analysis. In a subsequent dual-luciferase activity assay, direct binding of miR-154 to DKK2 was detected. Further experiments demonstrated that transfection of DKK2 siRNA or miR-154 resulted in increased levels of β-catenin, α-SMA, and collagens I and III. Moreover, these changes were observed in association with increases in CF proliferation and migration, and reduced apoptosis. Conversely, transfection of miR-154 inhibitors or DKK2 overexpression vector resulted in lower expression levels of β-catenin, α-SMA, and collagens I and III, suppressed cell proliferation and migration, and enhanced apoptosis. Furthermore, in each assay, when the DKK2 overexpression vector and miR-154 mimics were co-transfected, the functions of each component were counteracted by the other. Therefore, in CFs, targeting of DKK2 by miR-154 leads to upregulation of β-catenin expression and activation of the classical Wnt signaling pathway and CFs. These results suggest new targets for the clinical treatment of MF and ischemic heart disease.