A109-24 Extracellular Matrix Protein 1 Activates The Hypoxia Inducible Factor Pathway Through Interaction With Transforming Growth Factor Beta Induced Integrin Beta 3 To Promote Lung Fibrogenesis

Abstract

Idiopathic pulmonary fibrosis (IPF) is characterised by relentless extracellular matrix remodelling and loss of lung compliance. Hypoxia-inducible factor signalling has been linked to fibroblast-driven matrix changes, but how macrophage-derived signals engage this pathway in fibroblasts is unclear. We investigated whether extracellular matrix protein 1 (ECM1), a macrophage-secreted factor under hypoxic regulation, promotes fibroblast activation and defined the mechanism connecting ECM1 to hypoxia and TGFβ signalling. Transcriptomic datasets from patients with fibrotic lung disease and bronchoalveolar lavage (BAL) samples were analysed to assess ECM1 expression and clinical association. Hypoxia models including in vivo hypoxic exposure and DMOG treatment were used to test HIF regulation of ECM1 in macrophages. Primary human lung fibroblasts were exposed to ECM1-conditioned media or recombinant ECM1 with or without TGFβ. RNA sequencing with gene set analysis profiled pathway activity, and HIF targets were quantified by immunoblotting. Hypoxia-responsive element luciferase assays measured HIF transcriptional activity. Co-immunoprecipitation assessed ECM1–integrin interactions, and ITGB3 silencing tested functional necessity. ECM1 was markedly elevated in fibrotic lung tissue and across independent BAL cohorts, and higher ECM1 associated with poorer survival independent of GAP stage. HIF activation in macrophages increased ECM1 expression and secretion. In fibroblasts, ECM1 alone had limited effect, but in the presence of TGFβ it markedly increased HIF activity, with transcriptomic analysis showing enrichment of hypoxia-related signatures. ECM1 and TGFβ also upregulated collagen-modifying enzymes consistent with enhanced pathological crosslinking. TGFβ induced integrin β3 in fibroblasts, ECM1 bound integrin β3, and ITGB3 knockdown abolished ECM1-driven HIF activation, demonstrating that ECM1 requires integrin β3 to activate hypoxic signalling in fibroblasts. These findings identify macrophage-derived ECM1 as a key mediator of macrophage–fibroblast crosstalk in pulmonary fibrosis. By engaging TGFβ-induced integrin β3 on fibroblasts, ECM1 amplifies hypoxic signalling and profibrotic matrix remodelling. ECM1 therefore represents both a mechanistic node and a potential biomarker and therapeutic target in fibrotic lung disease.

This abstract is funded by: University of Southampton