HMGA1 drives EMT in obliterative bronchiolitis through epigenetic regulation of chromatin accessibility in pulmonary epithelial cells.

BACKGROUND: Post-transplant obliterative bronchiolitis (OB) is a major cause of lung graft dysfunction and failure, with the epithelial-mesenchymal transition (EMT) process playing a pivotal role in driving extracellular matrix (ECM) deposition and fibrosis. METHODS: A mouse heterotopic tracheal allograft model was established to replicate the clinical manifestations of post-transplant OB. Histopathological alterations of tracheal grafts were assessed using Hematoxylin and Eosin (HE) staining. Gene expression was quantified through enzyme-linked immunosorbent assay (ELISA), immunofluorescence (IF), immunohistochemistry (IHC), reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and Western blot assays. Differentially expressed genes (DEGs) in heterotopic tracheal grafts were identified by RNA sequencing (RNA-Seq). Chromatin accessibility was evaluated using assay for transposase-accessible chromatin with sequencing (ATAC-Seq). RESULTS: Histological analysis revealed progressive luminal occlusion (7-14 days), with significant inflammatory infiltration at day 7 and ECM deposition at day 14. Elevated IL-1β/IL-6 levels and reduced IL-10 confirmed immune activation. High mobility group at-hook 1 (HMGA1) was upregulated in allografts and mediated TGF-β1-driven EMT in vitro. Integration of ATAC-seq and RT-qPCR in pulmonary epithelial cells demonstrated that HMGA1 orchestrates extensive chromatin remodeling during OB pathogenesis. HMGA1 directly enhanced chromatin accessibility at EMT-promoting loci, including specificity protein 1 (SP1), dedicator of cytokinesis 4 (DOCK4), serum response factor (SRF), and anillin (ANLN). Epigenetic reprogramming of these regulatory regions induced TGF-β1-mediated EMT. CONCLUSIONS: HMGA1 promotes EMT in OB by facilitating chromatin accessibility at EMT-associated loci, highlighting its potential as a therapeutic target for post-transplant intervention.