Summary
The bud tip epithelium of the branching mouse and human lung contains multipotent progenitors that are able to self-renew and give rise to all mature lung epithelial cell types. The current study aimed to understand the developmental signaling cues that regulate bud tip progenitor cells in the human fetal lung, which are present during branching morphogenesis, and to use this information to induce a bud tip progenitor-like population from human pluripotent stem cells (hPSCs) in vitro. We identified that FGF7, CHIR-99021 and RA maintained isolated human fetal lung bud tip progenitor cells in an undifferentiated state in vitro, and led to the induction of a 3-dimensional lung-like epithelium from hPSCs. 3-dimensional hPSC-derived lung tissue was initially patterned, with airway-like interior domains and bud tip-like progenitor domains at the periphery. Bud tip-like domains could be isolated, expanded and maintained as a nearly homogeneous population by serial passaging. Comparisons between human fetal lung bud tip cells and hPSC-derived bud tip-like cells were carried out using immunostaining, in situ hybridization and transcriptome-wide analysis, and revealed that in vitro derived tissue was highly similar to native lung. hPSC-derived bud tip-like structures survived in vitro for over 16 weeks, could be easily frozen and thawed and maintained multi-lineage potential. Furthermore, hPSC-derived bud tip progenitors had successful short-term engrafment into the proximal airways of injured immunocompromised NSG mouse lungs, where they began to express markers of proximal airway cells.
Author Contributions AJM and JRS conceived the study. AJM, MSN, BRD, SH, YA, AMC, and ESW conducted experiments. AJM, DRH, BRD, SH, MSN, YA, AMC, FZ, VL and JRS analyzed and interpreted results. ESW also provided critical materials and reagents. AJM and JRS wrote the manuscript. All authors read, edited and approved the final content of the manuscript.
Conflicts of Interest The authors have no conflicts to declare.
- BMP
- Bone Morphogenic Protein
- FGF
- Fibroblast Growth Factor
- RA
- All-Trans Retinoic Acid
- HLO
- Human Lung Organoid