Defining the role of oxygen tension in cell fate decision making of human neural progenitors
Human pluripotent stem cells (hPSCs) have opened up numerous avenues, including regenerative medicine and modeling development and disease. However, when compared to the fetal tissue-derived counterparts, in vitro derived hPSC progenies reflect very early human development (<6 weeks). Therefore, it is vital to understand the mechanisms of early human development to facilitate maturation of hPSCs in vitro. Low oxygen tension is important for maintaining the pluripotency of in vitro cultured human embryonic stem cells. However, the influence of oxygen tension on fidelity of PSC differentiation had not been studied extensively until now. In fact, embryogenesis before 10 weeks of gestation occurs under low oxygen (<2.5% O2). We hypothesized that manipulating oxygen tension to a physiological level in vitro would facilitate the transcriptional and functional maturity of hPSC derivatives by more faithfully mimicking in vivo conditions. We discovered that physiological oxygen tension (2% O2) promotes astrogliogenesis upon NPC differentiation and determined that hypoxia inducible factors (HIFs) are key transcription factors involved in this process. Activating HIF with small molecules facilitated astrogliogenesis, whereas silencing HIF delayed this process. Even transient changes in oxygen concentration affected cell fate through HIF by regulating the activity of MYC, a regulator of LIN28/let-7 that is critical for fate decisions in neural progenitors. Taking advantage of RNA-seq, metabolomics, and ChIP-seq techniques, we uncovered evidence of an early coherent response of neural progenitors to physiological oxygen at the transcriptional, metabolic and epigenetic levels. This response correlates with a persistent cell fate change, namely, the neuroepithelial cell (NEC) to radial glial cell (RGC) transition, which may contribute to astrogliogenesis upon differentiation. Taken together, physiological oxygen and HIF signaling play a key role in regulating cell fate decision in human neural progenitors. Furthermore, small molecules that activate HIF signaling can be simple tools to quickly and efficiently promote the development of mature cell types.