Fibroblast-epithelial cell interactions drive epithelial-mesenchymal transition differently in cells from normal and COPD patients.

David H Eidelman,Qutayba Hamid,Ting-Yu Lin,Shigenori Kyoh,Mara S Ludwig,Parameswaran Nair,Michiyoshi Nishioka,Andrea Mogas,Kevin Dessalle,Narayanan Venkatesan,Carolyn J Baglole

doi:10.1186/s12931-015-0232-4

Abstract

BackgroundEpithelial-to-mesenchymal transition (EMT), which involves changes in cellular morphology of highly polarized epithelial cells and the gain of mesenchymal cell phenotype with migratory and invasive capacities, is implicated in smoking-related chronic obstructive pulmonary disease (COPD). However, the interactions of fibroblasts and epithelial cells and the participation of fibroblasts in the EMT processes in COPD are poorly understood. Here, we investigated the hypothesis that EMT is active in human bronchial epithelial (HBE) cells of COPD patients, and that mediators secreted by lung fibroblasts from COPD patients induce EMT.MethodsPrimary HBE cells from normal subjects and COPD patients were purchased from LONZA. HLFs were derived from resected lung obtained from normal (N) and COPD (D) subjects and their conditioned medium (CM) was collected after 2-day culture in serum-free medium. The expression of epithelial and mesenchymal markers as well as EMT-related transcription factors in lung biopsies, and in HBE cells following stimulation with CM from both normal human lung fibroblasts (NHLF) and COPD human lung fibroblasts (DHLF) was evaluated by immunohistochemistry, qRT-PCR and western blot.ResultsBasal mRNA expression of mesenchymal markers and EMT-related transcription factors were increased in DHBE cells compared to normal human bronchial epithelial cells (NHBE) cells as well as in COPD lungs. CM from NHLF significantly induced vimentin expression in both NHBE and COPD human bronchial epithelial cells (DHBE) cells, but only increased N-cadherin expression in DHBE cells. CM from NHLF significantly induced Twist1 and Twist2 expression in NHBE cells and increased Snai2 (Slug) expression in DHBE cells. While CM from NHLF had no effect on such EMT markers, CM from DHLF significantly increased the protein expression of E-cadherin and vimentin in NHBE cells compared to control. N-cadherin expression was upregulated to a greater degree in NHBE cells than DHBE cells. Only CM from DHLF significantly increased E-/N-cadherin ratio in DHBE cells.ConclusionsOur results suggest that DHBE cells have partially undergone EMT under baseline conditions. DHLF-CM promoted EMT in NHBE, suggesting that interactions between fibroblast and epithelial cells may play an important role in the EMT process in COPD.

Highlights

Epithelial-to-mesenchymal transition (EMT), which involves changes in cellular morphology of highly polarized epithelial cells and the gain of mesenchymal cell phenotype with migratory and invasive capacities, is implicated in smoking-related chronic obstructive pulmonary disease (COPD)
Basal expression of EMT markers and EMT-related transcription factors are increased in COPD bronchial epithelial cells and COPD lung tissues To determine the basal expression of EMT-related markers in human bronchial epithelial (HBE) cells, we examined the mRNA expression of epithelial cells derived from normal subjects (NHBE) and COPD patients (DHBE)
While basal expression of Ecadherin in DHBE cells was not different from that of normal human bronchial epithelial cells (NHBE) cells (Fig. 1a), DHBE cells showed a significant increase in mRNA expression of typical mesenchymal markers including N-cadherin and vimentin (Fig. 1b,c)

Summary

Introduction

Epithelial-to-mesenchymal transition (EMT), which involves changes in cellular morphology of highly polarized epithelial cells and the gain of mesenchymal cell phenotype with migratory and invasive capacities, is implicated in smoking-related chronic obstructive pulmonary disease (COPD). Cigarette smoking is the main risk factor for COPD contributing to structural changes in the airways during COPD progression [1]. One of the mechanisms implicated in remodeling events associated with COPD pathogenesis is that fibroblastic cells arise from local conversion of epithelial cells by epithelial-mesenchymal transition (EMT) induced by cigarette smoking [2]. EMT is mainly characterized by the loss of epithelial markers such as cytokeratins, tight junction proteins and E-cadherin, the acquisition of mesenchymal markers such as vimentin and N-cadherin, and increased expression of the transcription factors Snail, Twist and Zeb [3]

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Conclusion