The critical cellular transitions that govern pancreas development in the human are largely unknown. Using a combination of single-cell RNA-sequencing, single-nucleus ATAC-sequencing, multiplexed RNA in situ hybridization and immunofluorescence validation in tissue, and functional validation in human pluripotent stem cell-derived beta cells, we have generated an extensive and validated multi-omic roadmap of human pancreatic development.

This map serves as a guidebook for human endocrine development, identifying novel intermediate progenitor states and lineage relationships, and characterizing cellular dynamics across developmental time. These results have critical implications for the field of regenerative medicine and for the implantation of human stem cell-derived beta cells as a treatment for diabetes. Our work shows that the current gold standard differentiation protocols are likely generating predominantly beta cell progenitors (rather than mature or even immature beta cells, as previously believed), in addition to a variety of cell states not well represented in the normal developing pancreas.

To improve protocols for differentiation of stem cell-derived beta cells, we need a roadmap of the critical factors and transitions in normal human development that we as a field are attempting to emulate. Our data indicate that the lineage trajectories taken by beta cells in human development demonstrate key differences from those in the better characterized mouse. We also identify key transcription factors that are aberrantly expressed or missing in stem cell-derived beta cells versus endogenous developing beta cells. Refinement of our differentiation protocols based upon this human-specific developmental roadmap will be critical in understanding what our goals should be with regards to purity and identity of stem cell-derived beta cells and their progenitors.