Squamous metaplasia amplifies pathologic epithelial-mesenchymal interactions in COPD patients
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
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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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 4

Paracrine secretion of IL-1β by P3 human bronchial epithelial cells increases β8 expression and αvβ8-mediated TGF-β activation of adjacent airway fibroblasts in a coculture model of the epithelial-mesenchymal trophic unit.

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Paracrine secretion of IL-1β by P3 human bronchial epithelial cells incr...
Normal adult airway fibroblasts were cultured alone (Mono) or cocultured (Co) with P3 human bronchial epithelial cells grown on filter inserts. (A) Total fibroblast RNA was harvested and RT-PCR performed using primers specific for β8 or β-actin, as a control. Shown is a representative experiment of 3 with similar results. No cDNA indicates a no template control. (B) Fibroblasts (n = 3) in mono- or coculture were stained with anti-β8 and analyzed by flow cytometry. Shown is mean fluorescence in arbitrary units. (C) Monocultured fibroblasts or fibroblasts after 48-hour coculture with P0 or P3 human bronchial epithelial cells (n = 6) were cocultured with TGF-β reporter cells in the presence of neutralizing anti-β8, or no antibody (none). Shown is fold increase in TGF-β activation relative to untreated fibroblasts in monoculture. (D) Airway fibroblasts (n = 3) were cocultured with P0 or P3 conditioned medium (CM) in the presence of no antagonist or different concentrations (5, 50, or 500 ng/ml) of IL-1RA, a naturally occurring soluble antagonist of IL-1α and IL-1β. The fibroblasts were stained with anti-β8 and analyzed using flow cytometry. Shown is the fold increase in β8 expression compared with matched airway fibroblasts grown without conditioned medium. **P < 0.001.