Abstract 14713: SIRT6 Blocks Differentiation of Cardiac Fibroblasts into Myofibroblasts by Inactivation of the TGFβ1 Signaling
Introduction: Cardiac fibrosis contributes to adverse cardiac remodeling which is precursor to heart failure. At the cellular level, fibrosis occurs because of differentiation of quiescent cardiac fibroblasts (CF) into myofibroblasts (myoFB), an activated fibroblast-like cell-type capable of synthesizing excessive extracellular matrix. Activation of TGFβ-signaling is considered to be a major contributor of this process. This study was undertaken to examine the role of SIRT6, an anti-aging molecule, on the differentiation of CF to myoFB and the development of cardiac fibrosis.
Methods and Results: Cardiac fibroblasts obtained from human failing hearts were analyzed for expression levels of SIRT6 and myoFB markers like, smooth muscle α-actin (SMA), fibronectin and collagen1 (Col1) by western blotting. Expression levels of SMA, fibronectin and Col1 were increased, whereas SIRT6 levels were decreased in CF prepared from failing hearts, compared to control hearts. To test whether SIRT6 deficiency contributed to activation of myoFB markers, we analyzed hearts of SIRT6 (+/-) mice. There was robust activation of myoFB markers and Mason-trichome blue positive staining for fibrosis in SIRT6 (+/-) hearts, compared to controls. To understand the mechanism involved, we analyzed different components of TGFβ-Smad3 signaling in SIRT6 deficient hearts. Expression levels of both pro- and mature-TGFβ1 and Smad3 were significantly elevated in SIRT6 (+/-) hearts, compared to controls. By using siRNA approach we also knocked down SIRT6 (SIRT6-KD) levels in human control CF, and analyzed sensitivity of these fibroblasts to pro-fibrotic agonists, Ang-II. SIRT6-KD fibroblasts had significantly higher levels of TGFβ1, and they were highly sensitive to Ang-II stimulation in terms of synthesizing myoFB markers. Over expression of SIRT6 blocked the synthesis of TGFβ1 and the fibrotic response to Ang-II, both in control and in SIRT6-KD fibroblasts, thus demonstrating anti-fibrotic activity of SIRT6.
Conclusions: These data indicate that SIRT6 is capable of blocking fibroblast differentiation into myofibroblasts by suppressing the synthesis of TGFβ1, and signify that SIRT6 could serve as a therapeutic target for the treatment of cardiac fibrosis and heart failure.
Author Disclosures: N.R. Sundaresan: None. M. Gupta: None. M.P. Gupta: None.
- © 2014 by American Heart Association, Inc.