Abstract
Rationale Chronic obstructive pulmonary disease (COPD) is a devastating and mostly irreversible lung disease. In COPD, the bronchial epithelium displays several structural and functional abnormalities affecting barrier integrity, cell polarity, and differentiation, as well as epithelial-to-mesenchymal transition and inflammation. Although COPD displays mostly irreversible changes, the (ir)reversible nature of epithelium pathology ex vivo remains poorly known and was the aim of this study.
Methods The persistence of COPD epithelium abnormalities was addressed in long-term (10 weeks) primary cultures of air/liquid interface-reconstituted airway epithelium from non-smoker controls, smoker controls, and COPD patients. Barrier function, epithelial polarity, cell commitment, epithelial-to-mesenchymal transition and inflammation were assessed in vitro, and certain features were compared in situ to the native epithelium. The role of inflammation was explored by stimulating cultures with a cytokine mix consisting of TNF-α, IL-6 and IL-1β.
Measurements and main results Almost all epithelial defects (barrier dysfunction, impaired polarity, lineage abnormalities) observed in cells from smokers and COPD patients persisted in vitro up to week 10, except IL-8/CXCL-8 release and epithelial-to-mesenchymal transition which declined over time. Cell lineage and polarity impairments matched abnormalities observed in situ in the surgical samples from which the in vitro epithelium was derived. Cytokine treatment induced COPD-like changes and, in COPD cells, reactivated epithelial-to-mesenchymal transition.
Conclusions The airway epithelium from smokers and COPD patients displays a memory of its native state and previous injuries by cigarette smoking, which is multidimensional and sustained for extended periods of time.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Author contributions
F.M.C. performed experiments, most data analysis, co-supervised the experimental design and wrote the manuscript. B.D. helped with cell cultures and samples collection. M.L. processed samples, designed PCR primers, and performed some PCR. T.P.B., W.J. and B.M.V. revised the manuscript. S.E.V., C.M.S. and B.R. collected and provided samples. J.A. helped with statistical analyses. A.M.C. helped with cell cultures. S.G. helped with manuscript redaction and revision. C.P. supervised the design of the study and the writing of the manuscript.
Sources of support. This work was supported by the Fondation Mont-Godinne, Belgium, grant to FC (N°FMG-2015-BC01, FMG-2016-BC01, and FMG-2017-BC01) and by the Fonds National de Recherche Scientifique (FNRS), Belgium, grant to FC (N°1.L505.18) and to CP (N°1.R016.16 and 1.R016.18). Funders were not involved in study design, data collection, data analysis, interpretation, or writing of the manuscript.
Main text modifications to highlight the memory of tobacco smoking. Figure modifications (all figures were revised and modified to depict all subjects results). Enrichment of supplementary data (particularly statistics)