Squamous metaplasia amplifies pathologic epithelial-mesenchymal interactions in COPD patients
Jun Araya, … , David J. Erle, Stephen L. Nishimura
Jun Araya, … , David J. Erle, Stephen L. Nishimura
Published October 25, 2007
Citation Information: J Clin Invest. 2007;117(11):3551-3562. https://doi.org/10.1172/JCI32526.
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Research Article Pulmonology

Squamous metaplasia amplifies pathologic epithelial-mesenchymal interactions in COPD patients

Abstract

Squamous metaplasia (SM) is common in smokers and is associated with airway obstruction in chronic obstructive pulmonary disease (COPD). A major mechanism of airway obstruction in COPD is thickening of the small airway walls. We asked whether SM actively contributes to airway wall thickening through alteration of epithelial-mesenchymal interactions in COPD. Using immunohistochemical staining, airway morphometry, and fibroblast culture of lung samples from COPD patients; genome-wide analysis of an in vitro model of SM; and in vitro modeling of human airway epithelial-mesenchymal interactions, we provide evidence that SM, through the increased secretion of IL-1β, induces a fibrotic response in adjacent airway fibroblasts. We identify a pivotal role for integrin-mediated TGF-β activation in amplifying SM and driving IL-1β–dependent profibrotic mesenchymal responses. Finally, we show that SM correlates with increased severity of COPD and that fibroblast expression of the integrin αvβ8, which is the major mediator of airway fibroblast TGF-β activation, correlated with disease severity and small airway wall thickening in COPD. Our findings have identified TGF-β as a potential therapeutic target for COPD.

Authors

Jun Araya, Stephanie Cambier, Jennifer A. Markovics, Paul Wolters, David Jablons, Arthur Hill, Walter Finkbeiner, Kirk Jones, V. Courtney Broaddus, Dean Sheppard, Andrea Barzcak, Yuanyuan Xiao, David J. Erle, Stephen L. Nishimura

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Figure 7

αvβ6-mediated TGF-β activation forms a self-amplifying loop of increasing TGF-β activation in human bronchial epithelial cells, which drives SM.

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αvβ6-mediated TGF-β activation forms a self-amplifying loop of increasin...
Normal human bronchial epithelial cells in 2D culture (n = 3) were assessed during serial passage (P0–P3) for integrin αvβ6 and αvβ8 expression by (A, upper panel) RT-PCR using primers specific for β8, β6, or β-actin, as a control or (A, lower panel) flow cytometry using no antibody, anti-β6, or anti-β8 (± SEM). (B) Human bronchial epithelial cells (n = 5) were tested for changes in integrin-mediated TGF-β activation during serial passage using TGF-β bioassay (± SEM). TGF-β activation was determined using pan–anti–TGF-β. (C) P2 human bronchial epithelial cells in 2D culture were treated for 4 days with no primary antibody, neutralizing anti–TGF-β, anti-β8, or anti-β6. RT-PCR was performed using primers to β8, β6, or β-actin, as a control (n = 5). Densitometry values were normalized to β-actin, and the results were expressed as fold decrease (± SE) relative to control antibody–treated cells where a value of 1 represents no change from control antibody–treated cells. *P < 0.05 (D) P2 human bronchial epithelial cells in 2D culture were treated with control antibody or neutralizing anti-β6, and total RNA was harvested and assessed for the EDC genes (42, 43), involucrin (IVL), desmocollin-2 (DSC2), small proline rich protein-1A (SPRR1A), -1B (SPRR1B) (n = 3), -3 (SPRR3), or S100A7 (n = 2) using real-time PCR. Shown is the fold reduction (log 10) in expression of EDC genes after treatment with anti-β6 compared with control antibody–treated samples.