Cellular profiling identifies an early profibrotic alveolar type 2 cell signature in lung fibrosis

RATIONALE: Idiopathic pulmonary fibrosis (IPF) is a progressive, age-associated lung disease characterized by short telomeres in alveolar type 2 (AT2) cells, epithelial remodeling, and fibrosis. OBJECTIVES: This study investigated how telomere dysfunction in AT2 cells lacking telomere repeat binding factor 1 (TRF1) drives lung remodeling in SPC-creTRF1flox/flox mice and its relevance to IPF. METHODS: A mouse model of telomere dysfunction was used to conditionally delete TRF1 in AT2 cells. SPC-creTRF1flox/flox mouse lung epithelial cells were used to perform single-cell RNA sequencing. AT2 cells from IPF lungs were analyzed by single-cell RNA sequencing in an organoid model. MEASUREMENTS AND MAIN RESULTS: Single-cell RNA sequencing revealed distinct pathologic AT2 cells enriched in DNA damage, senescence, oxidative stress, and profibrotic genes, along with fewer "normal" AT2 cells and increased club cells in SPC-creTRF1flox/flox mice. Pathologic AT2 cells showed different early- and late-stage gene signatures, with a prominent p53 signature at both time points. Genetic deletion of p53 in SPC-creTRF1flox/flox AT2 cells improved survival and prevented lung fibrosis. p53 deletion or inhibition improved organoid formation and surfactant protein C expression, as well as reduced profibrotic gene expression in AT2 cells isolated from SPC-creTRF1flox/flox mice or IPF lungs. CONCLUSIONS: These data suggest that the DNA damage response to AT2 cell telomere dysfunction, driven by enhanced p53 activity, mediates early AT2 cell transdifferentiation and senescence, leading to epithelial cell remodeling and fibrosis, and that reversing this reprogramming is a potential therapeutic approach for managing IPF.