Aberrant expansion of KRT5⁺ basal cells in the distal lung accompanies progressive alveolar epithelial cell loss and tissue remodelling during fibrogenesis in idiopathic pulmonary fibrosis (IPF). The mechanisms determining activity of KRT5⁺ cells in IPF have not been delineated. Here, we reveal a potential mechanism by which KRT5⁺ cells migrate within the fibrotic lung, navigating regional differences in collagen topography. In vitro, KRT5⁺ cell migratory characteristics and expression of remodelling genes are modulated by extracellular matrix (ECM) composition and organisation. Mass spectrometry- based proteomics revealed compositional differences in ECM components secreted by primary human lung fibroblasts (HLF) from IPF patients compared to controls. Over-expression of ECM glycoprotein, Secreted Protein Acidic and Cysteine Rich (SPARC) in the IPF HLF matrix restricts KRT5⁺ cell migration in vitro. Together, our findings demonstrate how changes to the ECM in IPF directly influence KRT5⁺ cell behaviour and function contributing to remodelling events in the fibrotic niche. Idiopathic pulmonary fibrosis has been associated with aberrant expansion of KRT5-expressing basal cells. Here the authors show how changes in the ECM glycoprotein SPARC restrict the movement of KRT5+ cells, affecting their retention within fibrotic tissue. [ABSTRACT FROM AUTHOR]

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