Cigarette Smoke Specifically Affects Small Airway Epithelial Cell Populations and Triggers the Expansion of Inflammatory and Squamous Differentiation Associated Basal Cells.

Christian T Wohnhaas,Yang Shen,Jürgen Schymeinsky,Patrick Baum,Florian Gantner,Birgit Stierstorfer,Coralie Viollet,Germán G Leparc,Heiko Stahl,Tobias Kiechle,Julia A Gindele

doi:10.3390/ijms22147646

Abstract

Smoking is a major risk factor for chronic obstructive pulmonary disease (COPD) and causes remodeling of the small airways. However, the exact smoke-induced effects on the different types of small airway epithelial cells (SAECs) are poorly understood. Here, using air–liquid interface (ALI) cultures, single-cell RNA-sequencing reveals previously unrecognized transcriptional heterogeneity within the small airway epithelium and cell type-specific effects upon acute and chronic cigarette smoke exposure. Smoke triggers detoxification and inflammatory responses and aberrantly activates and alters basal cell differentiation. This results in an increase of inflammatory basal-to-secretory cell intermediates and, particularly after chronic smoke exposure, a massive expansion of a rare inflammatory and squamous metaplasia associated KRT6A+ basal cell state and an altered secretory cell landscape. ALI cultures originating from healthy non-smokers and COPD smokers show similar responses to cigarette smoke exposure, although an increased pro-inflammatory profile is conserved in the latter. Taken together, the in vitro models provide high-resolution insights into the smoke-induced remodeling of the small airways resembling the pathological processes in COPD airways. The data may also help to better understand other lung diseases including COVID-19, as the data reflect the smoke-dependent variable induction of SARS-CoV-2 entry factors across SAEC populations.

Highlights

IntroductionAirway epithelial cells are a community of diverse cell types that constitute a physical barrier to the environment and contribute to homeostasis in the airways by regulating immune responses, mucociliary clearance and response to inhaled toxins [1,2,3]
In order to investigate the cellular composition of the small airway epithelium, isolated small airway epithelial cells from healthy non-smokers and chronic obstructive pulmonary disease (COPD) donors (n = 3 per group) were differentiated under air–liquid interface conditions into a pseudostratified epithelium [34]
A single cell suspension was generated of the differently treated air–liquid interface (ALI) cultures and a total of 34,690 cells were sequenced to investigate cell-specific heterogeneity and response to smoke on the transcriptomic level

Summary

Introduction

Airway epithelial cells are a community of diverse cell types that constitute a physical barrier to the environment and contribute to homeostasis in the airways by regulating immune responses, mucociliary clearance and response to inhaled toxins [1,2,3] These functions are managed by an interplay of the different epithelial cell types including basal, ciliated and secretory (club and goblet) cells, which constitute the main cell types as well as rare epithelial cells such as pulmonary ionocytes [1]. Dysfunction of the dynamic airway epithelium, including cellular alterations and altered molecular signaling, in response to inhaled toxins such as cigarette smoke (CS) has been linked to lung diseases

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