UCLA

Human pluripotent stem cells (hPSCs) are derived from the developing blastocyst or through transcription factor based reprogramming. hPSCs have the capacity to self-renew and give rise to all cell types of the human body. These two defining characteristics make them attractive for a variety of uses including regenerative medicine and modeling human development and disease. While it is clear that hPSCs can differentiate into all cell types, it is unknown how similar hPSC derivatives are to cells that have undergone development in vivo. Using previously established differentiation protocols we demonstrated that both types of hPSCs could generate functional motor neurons that displayed repetitive action potentials characteristic of mature motor neurons. Furthermore, these motor neurons differentiated through a progressive and predictable induction of developmental stages, suggesting hPSC differentiation appears to obey normal developmental progression. In a comprehensive comparison of hPSC derivatives and tissue-derived counterparts, we determined that the progeny of hPSCs are most similar to a cell type found prior to 6 weeks of gestation. These hPSC derivatives continued to express genes normally found at 3-5 weeks of gestation, including LIN28; while tissue derived counterparts had already silenced these genes. In vitro function demonstrated that hPSC derivatives also acted like developmentally primitive cells. These findings suggest that developmental timing is conserved in vitro and perhaps even innate to the differentiating cell. Finally, we explored the role of the LIN28/let-7 pathway on the developmental maturity of hPSC-derived neural progenitor cells (hPSC-NPCs) as measured by their ability to generate neurons or glia. We determined that addition of let-7s into hPSC-NPCs can correct a significant number of the genes differentially expressed between hPSC derivatives and tissue-derived counterparts. Furthermore, the manipulation has a modest, but significant effect on the functional maturity of PSC-NPCs. Taken together, these data demonstrate that hPSCs can serve as an excellent and tractable model of human development.