Smad gene expression in pulmonary fibroblasts: indications for defective ECM repair in COPD

Andre Zandvoort,Johannes Twm Vos,Dirkje S Postma,Marnix R Jonker,Jacobien A Noordhoek,Wim Timens

doi:10.1186/1465-9921-9-83

Andre Zandvoort, Johannes Twm Vos + Show 4 more

Open Access

https://doi.org/10.1186/1465-9921-9-83

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Abstract

BackgroundChronic Obstructive Pulmonary Disease (COPD) is characterized by defective extracellular matrix (ECM) turnover as a result of prolonged cigarette smoking. Fibroblasts have a central role in ECM turnover. The TGFβ induced Smad pathway provides intracellular signals to regulate ECM production. We address the following hypothesis: fibroblasts have abnormal expression of genes in the Smad pathway in COPD, resulting in abnormal proteoglycan modulation, the ground substance of ECM.MethodsWe compared gene expression of the Smad pathway at different time points after stimulation with TGFβ, TNF or cigarette smoke extract (CSE) in pulmonary fibroblasts of GOLD stage II and IV COPD patients, and controls.ResultsWithout stimulation, all genes were similarly expressed in control and COPD fibroblasts. TGFβ stimulation: downregulation of Smad3 and upregulation of Smad7 occurred in COPD and control fibroblasts, indicating a negative feedback loop upon TGFβ stimulation. CSE hardly influenced gene expression of the TGFβ-Smad pathway in control fibroblasts, whereas it reduced Smad3 and enhanced Smad7 gene expression in COPD fibroblasts. Furthermore, decorin gene expression decreased by all stimulations in COPD but not in control fibroblasts.ConclusionFibroblasts of COPD patients and controls differ in their regulation of the Smad pathway, the contrast being most pronounced under CSE exposure. This aberrant responsiveness of COPD fibroblasts to CSE might result in an impaired tissue repair capability and is likely important with regard to the question why only a subset of smokers demonstrates an excess ECM destruction under influence of cigarette smoking.

Highlights

Chronic Obstructive Pulmonary Disease (COPD) is a severe, slowly progressive and disabling disease associated with accelerated lung function decline
Study design To answer the question whether genes of the Smad pathway are differentially expressed in COPD and controls, we stimulated primary fibroblasts of patients with stage II and stage IV COPD and controls with Transforming Growth Factor β (TGFβ), Tumor Necrosis Factor (TNF) and cigarette smoke extract (CSE) for 1, and 24 hours
Influence of TGFβ, TNF, and CSE on Smad pathway related gene expression in fibroblasts Healthy individuals TGFβ stimulation Downregulation of Smad3 gene expression occurred at 24-hour stimulation, while Smad2, Smad4, biglycan and versican gene expression were upregulated

Summary

Introduction

Chronic Obstructive Pulmonary Disease (COPD) is a severe, slowly progressive and disabling disease associated with accelerated lung function decline. Emphysema is due to an extensive extracellular matrix (ECM) destruction of lung parenchyma [1,2,3,4,5]. Emphysema can coincide with fibrosis of the airways as observed in chronic bronchitis and small airways disease [1,6,7,8]. The generally held hypothesis is that cigarette smoke induces an excess in extracellular matrix (ECM) degrading enzymes and reactive oxygen species that subsequently lead to ECM destruction of lung parenchyma [1]. Chronic Obstructive Pulmonary Disease (COPD) is characterized by defective extracellular matrix (ECM) turnover as a result of prolonged cigarette smoking. We address the following hypothesis: fibroblasts have abnormal expression of genes in the Smad pathway in COPD, resulting in abnormal proteoglycan modulation, the ground substance of ECM

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