A human lung organoid platform for studying radiation-induced pulmonary fibrosis and antifibrotic drug screening.

Radiation-induced pulmonary injury and fibrosis (RIPI/RIPF) is a major complication following thoracic radiotherapy, characterized by persistent inflammation and excessive extracellular matrix deposition leading to irreversible lung disease. The development of antifibrotic drugs has been limited by the lack of physiologically relevant in vitro models that mimic the complex lung microenvironment. In this study, we established a human embryonic stem cells-derived human lung organoids (hLOs) model, comprising major epithelial cell types, including AT1, AT2, goblet, basal, club, and ciliated cells. Following repeated irradiation, hLOs exhibited key features of RIPF, including impaired proliferation, epithelial barrier disruption, epithelial-mesenchymal transition, upregulation of profibrotic cytokines, and extensive collagen deposition. Single-cell RNA sequencing revealed a marked reduction in proliferative AT2 cells and shifts in epithelial subpopulations, mimicking cellular dynamics observed in vivo. Importantly, Pirfenidone, an antifibrotic drug, significantly reduced the expression of TGF-β, α-SMA, and COL1A2 in irradiated hLOs. These findings demonstrate that our hESC-derived hLO model recapitulates key molecular and structural features of RIPF and offers a human-relevant, scalable platform for mechanistic studies and antifibrotic drug screening. This organoid system provides a time-efficient alternative to conventional animal models, enabling fibrosis-like responses, and may serve as a valuable tool for advancing therapeutic strategies against RIPI/RIPF.