GRAMD2+alveolar type I cell plasticity facilitates cell state transitions in organoid culture

Abstract

SUMMARYAlveolar epithelial regeneration is critical for normal lung function and becomes dysregulated in disease. While alveolar type 2 (AT2) and club cells are known distal lung epithelial progenitors, determining if alveolar epithelial type 1 (AT1) cells also contribute to alveolar regeneration has been hampered by lack of highly specific mouse models labeling AT1 cells. To address this, theGramd2CreERT2transgenic strain was generated and crossed toRosamTmGmice. Extensive cellular characterization, including distal lung immunofluorescence and cytospin staining, confirmed that GRAMD2+AT1 cells are highly enriched for green fluorescent protein (GFP). Interestingly,Gramd2CreERT2GFP+cells were able to form organoids in organoid co-culture with Mlg fibroblasts. Temporal scRNAseq revealed thatGramd2+AT1 cells transition through numerous intermediate lung epithelial cell states including basal, secretory and AT2 cell in organoids while acquiring proliferative capacity. Our results indicate thatGramd2+AT1 cells are highly plastic suggesting they may contribute to alveolar regeneration.