Prolonged WNT/ß-catenin signaling induces cellular senescence in aging and pulmonary fibrosis

Introduction: Idiopathic Pulmonary Fibrosis (IPF) is an age-related disease, which displays several hallmarks of aging, such as cellular senescence. The lung epithelium represents a major site of tissue injury in IPF resulting in functional changes including aberrant activity of the developmental WNT/β-catenin pathway. The potential impact of WNT/β-catenin signaling on epithelial senescence in aging and IPF remains elusive. Methods: Single Cell RNA Sequencing (scRNAseq) from EpCAM-enriched cell populations was performed from IPF and donor lungs. RNAseq, qPCR and flow cytometry was applied to characterize ATII cells from young (3 months) and old (18 months) wild-type or WNT-reporter mice, respectively. Progenitor cell potential was investigated by organoid assay. ATII cells were treated with WNT3A for up to 7 days. Cellular senescence was monitored by qPCR and senescence-associated s-Galactosidase activity. Results: ScRNAseq revealed a concomitant enrichment of both WNT/β-catenin signaling and cellular senescence in distinct cell populations in IPF. Similarly, aged ATII cells showed increased cellular senescence and increased WNT/β-catenin activity. Moreover, aged ATII cells exhibit an impaired organoid forming capacity. Bulk RNA sequencing revealed 416 differentially expressed genes in aged ATII cells, many of which are further known to be dysregulated in fibrosis. Chronic WNT/β-catenin activation induced cellular senescence in primary ATII cells. Simultaneously, chronic but not acute WNT activation induced a profibrotic state with increased expression of the impaired ATII cell marker Keratin8. Conclusions: These results suggest that WNT/β-catenin signaling contributes to progenitor cell dysfunction and impaired lung repair in the aged lung, which is further enhanced in IPF.