Inhibition of autophagy inhibits the conversion of cardiac fibroblasts to cardiac myofibroblasts.

Shivika S Gupta,Ian M.C Dixon,Saeid Ghavami,Natalie M Landry,Jeffrey T Wigle,Matthew R Zeglinski,Thomas Klonisch,Sunil G Rattan,Andrew J Halayko

doi:10.18632/oncotarget.12392

Shivika S Gupta, Ian M.C Dixon + Show 7 more

Open Access

https://doi.org/10.18632/oncotarget.12392

Copy DOI

Abstract

The incidence of heart failure with concomitant cardiac fibrosis is very high in developed countries. Fibroblast activation in heart is causal to cardiac fibrosis as they convert to hypersynthetic cardiac myofibroblasts. There is no known treatment for cardiac fibrosis. Myofibroblasts contribute to the inappropriate remodeling of the myocardial interstitium, which leads to reduced cardiac function and ultimately heart failure. Elevated levels of autophagy have been linked to stress-induced ventricular remodeling and other cardiac diseases. Previously, we had shown that TGF-β1 treatment of human atrial fibroblasts both induced autophagy and enhanced the fibrogenic response supporting a linkage between the myofibroblast phenotype and autophagy. We now demonstrate that with in vitro culture of primary rat cardiac fibroblasts, inhibition of autophagy represses fibroblast to myofibroblast phenoconversion. Culturing unpassaged cardiac fibroblasts for 72 hours on plastic tissue culture plates is associated with elevated α-smooth muscle actin (α-SMA) expression. This activation parallels increased microtubule-associated protein 1A/1B-light chain 3 (LC-3β II) protein expression. Inhibition of autophagy with bafilomycin-A1 (Baf-A1) and chloroquine (CQ) in cardiac fibroblasts significantly reduces α-SMA and extracellular domain A fibronectin (ED-A FN) protein vs untreated controls. Myofibroblast cell migration and contractility were significantly reduced following inhibition of autophagy. These data support the possibility of a causal link between cardiac fibroblast-to-myofibroblast phenoconversion and autophagy.

Highlights

In response to the loss of heart muscle following myocardial infarction (MI), the cardiac interstitium is significantly remodeled and contributes to the pathogenesis of heart failure [1,2,3]
As we found that TGF-β1 treatment of human atrial fibroblasts caused a parallel induction of fibrogenesis and autophagy [14], we have investigated the effect of autophagy inhibition on rat cardiac fibroblasts and its conversion to myofibroblasts
To estimate the extent of fibroblast to myofibroblast phenocoversion of unpassaged cardiac fibroblasts over time, we tracked the expression of α-smooth muscle actin (α-SMA) over 72 hours post-plating

Summary

Introduction

In response to the loss of heart muscle following myocardial infarction (MI), the cardiac interstitium is significantly remodeled and contributes to the pathogenesis of heart failure [1,2,3]. Following MI, the infarct zone heals, but continued, excessive activation of resident cardiac fibroblasts eventually culminates in global cardiac fibrosis with both impaired lusitropic and inotropic function [4]. While cardiac fibroblasts are relatively quiescent cells that contribute little to matrix remodeling or wound healing, phenoconverted myofibroblasts persist within the infarcted myocardium and contribute to excessive ECM deposition [7,8,9]. Myofibroblasts are contractile cells that express α-smooth muscle actin (α-SMA), which, in combination with the appearance of stress fibres, is a reliable marker for the myofibroblast phenotype [5, 10]. Understanding the mechanisms that activate the conversion of cardiac fibroblasts into hypersecretory, contractile cardiac myofibroblasts is an important topic for investigation [11, 12]

Methods

Results

Conclusion