Transgenic porcine model reveals two distinct LGR5-positive cell populations during lung development and homeostasis

LGR5 stem cells play a pivotal role in homeostasis, repair, and regeneration in multiple organs including skin and gastrointestinal tract, yet little is known about their role in the lung. Furthermore, findings from mice, a widely used animal model, suggest that LGR5 expression differs drastically from that of humans. In this work, using a new transgenic pig model, we identify two populations of LGR5+ cells in the lung that are conserved in human, but not mouse lungs. Using RNA sequencing, 3D imaging, organoid models, and differentiation assays, we determine that in the fetal lung, epithelial LGR5 expression is transient in a subpopulation of SOX9/SFTPC-expressing lung tip cells. In contrast, epithelial LGR5 expression is absent from postnatal lung, but is reactivated in bronchioalveolar organoids derived from basal airway cells. We also describe a separate population of mesenchymal LGR5+ cells that surrounds developing and mature airways, lies adjacent to airway basal cells, and is closely associated with nerve fibers. Transcriptionally, mesenchymal LGR5+ cells are a subset of peribronchial fibroblasts populations and express unique patterns of WNT and TGF-β signaling pathway genes. These results support two distinct roles for LGR5+ cells in the lung and describe a physiologically relevant animal model for further studies on the function of these populations in repair and regeneration. ### Competing Interest Statement The authors have declared no competing interest.