Regeneration of the lung alveolus by an evolutionarily conserved epithelial progenitor [ATAC-seq]

The lung alveolus is the primary site of gas exchange in mammals. Within the alveolus, the alveolar type 2 (AT2) epithelial cell population generates surfactant to maintain alveolar structure and harbors a regenerative capacity to repair the alveolus after injury. We show that a Wnt-responsive alveolar epithelial progenitor (AEP) lineage within the AT2 cell population is critical for regenerating the alveolar niche. AEPs are a stable lineage during alveolar homeostasis but expand rapidly to regenerate a majority of the alveolar epithelium after acute lung injury. AEPs exhibit a distinct transcriptome, epigenome, and functional phenotype with specific responsiveness to Wnt and FGF signaling that modulates differentiation and self-renewal, respectively. Importantly, human AEPs (hAEPs) can be isolated and characterized through a conserved surface marker and are required for human alveolar self-renewal and differentiation using alveolar organoid assays. Together, our findings show that AEPs are an evolutionarily conserved alveolar progenitor lineage essential for regenerating the alveolar niche in the mammalian lung.