Hedgehog signaling in the airway epithelium of patients with chronic obstructive pulmonary disease

A Tam,D Nickle,T L Hackett,M Obeidat,P D Paré,D D Sin,G K Singhera,T Shaipanich,J C Hogg,C W T Yang,D R Dorscheid,K M Mcnagny,J M Leung,M Hughes

doi:10.1038/s41598-019-40045-3

Abstract

Genome-wide association studies have linked gene variants of the receptor patched homolog 1 (PTCH1) with chronic obstructive pulmonary disease (COPD). However, its biological role in the disease is unclear. Our objective was to determine the expression pattern and biological role of PTCH1 in the lungs of patients with COPD. Airway epithelial-specific PTCH1 protein expression and epithelial morphology were assessed in lung tissues of control and COPD patients. PTCH1 mRNA expression was measured in bronchial epithelial cells obtained from individuals with and without COPD. The effects of PTCH1 siRNA knockdown on epithelial repair and mucous expression were evaluated using human epithelial cell lines. Ptch1+/− mice were used to assess the effect of decreased PTCH1 on mucous expression and airway epithelial phenotypes. Airway epithelial-specific PTCH1 protein expression was significantly increased in subjects with COPD compared to controls, and its expression was associated with total airway epithelial cell count and thickness. PTCH1 knockdown attenuated wound closure and mucous expression in airway epithelial cell lines. Ptch1+/− mice had reduced mucous expression compared to wildtype mice following mucous induction. PTCH1 protein is up-regulated in COPD airway epithelium and may upregulate mucous expression. PTCH1 provides a novel target to reduce chronic bronchitis in COPD patients.

Highlights

GOLD STAGE 2, and (E) chronic obstructive pulmonary disease (COPD) GOLD STAGE 3 were stained with patched homolog 1 (PTCH1) antibody
Airway epitheliumspecific PTCH1 protein expression was normalized to the length of basement membrane in (F) nonCOPD, COPD GOLD STAGE 2 and GOLD STAGE 3/4, and (G) with COPD stratified by smoking status. (H) PTCH1 mRNA expression was normalized to GAPDH and expressed as ∆∆ct in human bronchial brushings from subjects with or without COPD. (I) Airway epithelial thickness and (J) total airway epithelial cell counts were quantified in subjects without COPD, COPD GOLD STAGE 2 and GOLD STAGE 3/4
PTCH1 mRNA expression was significantly increased in epithelial cells obtained by bronchial-brushings from patients with COPD compared to subjects without COPD (Fig. 1H)

Summary

Introduction

GOLD STAGE 2, and (E) COPD GOLD STAGE 3 were stained with PTCH1 antibody. Airway epitheliumspecific PTCH1 protein expression was normalized to the length of basement membrane (μm) in (F) nonCOPD, COPD GOLD STAGE 2 and GOLD STAGE 3/4, and (G) with COPD stratified by smoking status (current vs ex-smokers). (H) PTCH1 mRNA expression was normalized to GAPDH and expressed as ∆∆ct in human bronchial brushings from subjects with or without COPD. (I) Airway epithelial thickness and (J) total airway epithelial cell counts were quantified in subjects without COPD, COPD GOLD STAGE 2 and GOLD STAGE 3/4. Airway epitheliumspecific PTCH1 protein expression was normalized to the length of basement membrane (μm) in (F) nonCOPD, COPD GOLD STAGE 2 and GOLD STAGE 3/4, and (G) with COPD stratified by smoking status (current vs ex-smokers). We hypothesize that hedgehog signalling is dysregulated in COPD patients which, in turn, may lead to increased cell proliferation and mucous expression in the airways. These endpoints are of great interest in COPD as currently there are no therapies that reduce mucous production and cough, which are symptoms of great importance to patients[15]. We assessed the protein expression levels and cell types in which PTCH1 is expressed in the airway epithelium of patients with and without COPD, and the biological role of PTCH1 on cell proliferation and mucous expression in vitro and in vivo

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