Generation and expansion of transitional lung organoids from human pluripotent stem cells.

Several novel distal lung populations were recently identified that may be involved in regeneration after injury. 1-3 As these are absent in rodents, a deeper understanding of their roles and lineage relations requires availability of equivalent cells in vitro . Here we report the generation of expandable, clonal spheres, called 'transitional lung organoids' (TLOs), from human pluripotent stem cells. TLOs consist mainly of previously identified type 0 alveolar epithelial (AT0) cells, terminal respiratory bronchiole stem cells and distal basal cells (BCs). 3 Velocity analysis of single cell RNAseq data suggests that distal BCs are the most undifferentiated progenitors in the TLOs and give rise to AT0 cells. TLOs will be an important resource for studies in human lung regeneration, and potentially for regenerative approaches for human lung disease.