Tracing the origin of alveolar stem cells in lung repair and regeneration

Alveolar type 2 (AT2) cells are stem cells of the alveolar epithelia. Previous genetic lineage tracing studies reported multiple cellular origins for AT2 cells after injury. However, conventional lineage tracing based on Cre-loxP has the limitation of non-specific labeling. Here, we introduced a dual recombinase-mediated intersectional genetic lineage tracing approach, enabling precise investigation of AT2 cellular origins during lung homeostasis, injury, and repair. We found AT1 cells, being terminally differentiated, did not contribute to AT2 cells after lung injury and repair. Distinctive yet simultaneous labeling of club cells, bronchioalveolar stem cells (BASCs), and existing AT2 cells revealed the exact contribution of each to AT2 cells post-injury. Mechanistically, Notch signaling inhibition promotes BASCs but impairs club cells’ ability to generate AT2 cells during lung repair. This intersectional genetic lineage tracing strategy with enhanced precision allowed us to elucidate the physiological role of various epithelial cell types in alveolar regeneration following injury. [Display omitted] •AT1 cells do not contribute to AT2 cells during lung homeostasis and injury•Intersectional genetics enables distinctive tracing of BASCs, club cells, and AT2 cells•Club cells can contribute to the majority of alveoli after severe lung injuries•Notch signaling distinctly regulates the cell fates of club cells and BASCs Using dual recombinase-mediated intersectional genetic approaches, Liu et al. find that alveolar stem cells (AT2 cells) are derived from existing AT2 cells, club cells, and BASCs but not from terminally differentiated AT1 cells during lung repair and regeneration.