Club cell functions as a Wnt-responsive progenitor for tissue repair in COPD

Introduction: Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide that is characterized by progressive loss of alveolar tissue. Endogenous lung stem cells and tissue repair pathways are thought be dysfunctional and their reactivation is a promising therapeutic approach for COPD. Wnt/β-catenin signaling is critical for stem cell function and is reduced in human COPD lungs. We previously demonstrated that therapeutic Wnt/β-catenin initiated tissue repair in COPD patient-derived lung tissue ex vivo. Recently, we identified an epithelial progenitor population enriched with club cells, which were activated by Wnt/β-catenin signaling to form alveolar organoids. Thus, we hypothesize that club cells represent a novel Wnt-responsive epithelial progenitor for tissue repair in COPD. Methods: Single cell RNA sequencing (scRNA seq), organoid assay, fate tracing studies, flow cytometry, immunofluorescence, FACS sorting, porcine pancreatic elastase (PPE) induced mouse COPD model. Results: 1) Using scRNA seq, we identified club cells as the major progenitor cells in the Wnt-responsive epithelial progenitor cell population. 2) We perform fate tracing studies using a Scgb1a1Cre-ERT;Rosa-Tomato;TCF/Lef:H2B-GFP mouse line combined with lung organoid assays to demonstrate that activation of the Wnt/β-catenin signaling using the GSK3 inhibitor CHIR9920 increased the number of alveolar organoids formed by club cells. 3) In a PPE-induced mouse COPD model, we identified an impaired organoid forming capacity of club cells, which could be restored by activation of the Wnt/β-catenin signaling. Importantly, the alveolar organoid formation was largely increased. Conclusion: Our study reveals a novel mechanism of club cell activation by Wnt/β-catenin signaling in COPD.