C71-31 Human Alveolar Type 2 Epithelium Undergoes Dysplastic Basal Transdifferentiation via Tgfβ1-induced Cytokeratin Remodeling

Abstract Aberrant epithelial regeneration is a defining feature of chronic lung diseases such as idiopathic pulmonary fibrosis (IPF), where alveolar type 2 epithelial cells (AT2s), traditionally viewed as the resident alveolar stem cells, fail to regenerate functional alveolar epithelium and instead transdifferentiate into dysplastic cell types via aberrant transitional cells. Using multiomic sequencing of human AT2s (hAT2s) from organoids, normal lungs, and IPF lungs, we explore normal euplastic regenerative trajectories and aberrant dysplastic regenerative trajectories of hAT2s. We interrogate gene regulatory networks along these trajectories and identify canonical TGFβ1 signaling as a primary driver of AT2 to basal cell transdifferentiation. Ligand-receptor analysis of organoid and IPF single cell sequencing using NICHES also revealed the role of TGFβ1 signaling in dysplastic transitional cells. Using CUT&RUN, we establish canonical TGFβ1/SMAD signaling as a direct transcriptional activator of KRT17, a marker of dysplastic transitional cells. Furthermore, TGFβ1 signaling induced interaction of KRT17 with Stratifin, an adapter protein. Disruption of scaffolding activity of Stratifin abrogated its interaction with KRT17 and inhibited TGFβ1-mediated AT2 migration, suggesting their functional role in AT2 to basal cell transdifferentiation observed in the distal lungs of IPF patients. Collectively, our data defines the cellular and molecular framework of hAT2 fate decisions in human lungs and organoid models, emphasizing the critical role of temporally regulated mesenchymal signals. Our computational strategy provides new insights into the mechanisms of alveolar remodeling in fibrosis and opens avenues for therapeutic targeting of epithelial plasticity to promote regenerative outcomes. This abstract is funded by: NHLBI, CIRM