Mechanosensing by the α6-integrin confers an invasive fibroblast phenotype and mediates lung fibrosis

Huaping Chen,Ashish Kurundkar,Naiheng Yang,Lanyan Zhu,Veena B Antony,Victor J Thannickal,Xiangwei Huang,Qiang Ding,Yong Zhou,Jing Qu,Gang Liu,Aida Venado

doi:10.1038/ncomms12564

Abstract

Matrix stiffening is a prominent feature of pulmonary fibrosis. In this study, we demonstrate that matrix stiffness regulates the ability of fibrotic lung myofibroblasts to invade the basement membrane (BM). We identify α6-integrin as a mechanosensing integrin subunit that mediates matrix stiffness-regulated myofibroblast invasion. Increasing α6-expression, specifically the B isoform (α6B), couples β1-integrin to mediate MMP-2-dependent pericellular proteolysis of BM collagen IV, leading to myofibroblast invasion. Human idiopathic pulmonary fibrosis lung myofibroblasts express high levels of α6-integrin in vitro and in vivo. Genetic ablation of α6 in collagen-expressing mesenchymal cells or pharmacological blockade of matrix stiffness-regulated α6-expression protects mice against bleomycin injury-induced experimental lung fibrosis. These findings suggest that α6-integrin is a matrix stiffness-regulated mechanosensitive molecule which confers an invasive fibroblast phenotype and mediates experimental lung fibrosis. Targeting this mechanosensing α6(β1)-integrin offers a novel anti-fibrotic strategy against lung fibrosis.

Highlights

Matrix stiffening is a prominent feature of pulmonary fibrosis
We explore mechanotransductive mechanisms for a6-integrin expression and demonstrate that the expression of this integrin subunit by lung myofibroblasts is increased in both human idiopathic pulmonary fibrosis (IPF) and bleomycin injury-induced experimental lung fibrosis
To determine whether matrix stiffness regulates the expression of cell adhesion and extracellular matrix (ECM) molecules, we performed a qPCR array analysis that contains 84 genes, including 16 integrin subunits in primary lung myofibroblasts isolated from patients with IPF (Supplementary Fig. 1)

Summary

Results

A6 Is a matrix stiffness-regulated mechanosensitive gene. To determine whether matrix stiffness regulates the expression of cell adhesion and ECM molecules, we performed a qPCR array analysis that contains 84 genes, including 16 integrin subunits in primary lung myofibroblasts isolated from patients with IPF (Supplementary Fig. 1). Lung myofibroblasts isolated from bleomycin-treated mice respond to matrix stiffening with increased a6-expression (Supplementary Fig. 2b,c) These results identify, for the first time, the a6-integrin subunit as a matrix stiffness-regulated mechanosensitive gene/protein. Quantitative chromatin immunoprecipitation assay demonstrated that stiff matrix significantly increased the constitutive enrichment of a6-promoter DNA in phospho c-Fos antibody-immunoprecipitated chromatin of IPF lung myofibroblasts at both the proximal ( À 2,873/ À 2,879 nt) and distal ( À 4,848/ À 4,854 nt) TRE sites (Fig. 1g) These data suggest that the c-Fos/c-Jun complex of AP-1 transcription factor family mediates stiff matrix-dependent transactivation of a6-gene. Similar findings were observed when cells were cultured on soft (2 kPa) and stiff (30 kPa) polydimethylsiloxane hydrogels (Supplementary Fig. 3a) These data suggest that stiff matrix promotes IPF lung myofibroblasts to invade the BM. These results provide strong support for a critical pro-fibrotic role for the mechanosensitive a6-integrin subunit, at least in part, by its capacity to mediate myofibroblast invasion

Discussion

Methods