Lung extracellular matrix modulates KRT5 + basal cell activity in pulmonary fibrosis.

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.