Aged alveolar epithelium contributes to inflammaging and reduced stem cell function in the lung

Abstract

<b>Introduction:</b> Aging is a major risk factor for the development of Idiopathic Pulmonary Fibrosis (IPF), and several aging mechanisms, such as inflammaging and cellular senescence contribute to IPF pathogenesis. However, it remains unknown which mechanisms drive cellular senescence and inflammaging and how these processes are linked. <b>Methods:</b> Single Cell RNA Sequencing (scRNAseq) was performed on EpCAM-enriched cells from IPF and donor lungs, RNAseq, qPCR, flow cytometry and organoid assays were applied to characterize ATII cells from 3 months and 18 months old wild-type or WNT-reporter mice. ATII cells were induced to senescence monitored by qPCR and senescence-associated ß-Galactosidase activity. Inflammatory mediators were analyzed by ELISA. <b>Results:</b> ScRNAseq revealed a concomitant enrichment of senescence and inflammaging in distinct cell populations in IPF. Bulk RNAseq of aged ATII cells exposed overlapping inflammaging and senescence signatures as well as increased WNT/β-catenin activity. Treatment of primary ATII cells with DNA damage (X-ray or bleomycin) or chronic canonical (but not non-canonical) WNT activation induced senescence and the secretion of inflammaging-related mediators such as Interleukin-6. Notably, induction of senescence in ATII cells reduced their progenitor cell function in a dose-dependent manner as assessed by their capacity to form organoids. <b>Conclusions:</b> These results suggest a potential impact of cellular senescence and WNT signaling on inflammaging and progenitor cell function. Further analysis of single cell data from IPF patients will give insight into senescence-driven molecular mechanisms to induce inflammaging in aberrant cell types in IPF.