Effects of hypoxia on pluripotency in murine iPS cells.
Retroviral transduction of four transcription factors (Oct4, Sox2, Klf4 and c-Myc) or three factors, excluding c-Myc, has been shown to initiate a reprogramming process that results in the transformation of murine fibroblasts to induced pluripotent stem (iPS) cells, and there has been a rapid increase in the number of iPS cell-based preclinical trials. In this study, the effects of these transcription factors were evaluated regarding the growth and differentiation of murine iPS cells under hypoxia. Based on the results of RT-PCR and alizarin red S staining, there were no statistical differences in the growth and differentiation of iPS cells or the induction of iPS cells to osteoblasts under hypoxia between the transcription factor groups. Furthermore, the function of hypoxia inducible factors (HIFs) in murine iPS cells under hypoxia was investigated in relation to the morphology and expression of transcription factors using RT-PCR and Western blotting. The HIF-2α knockdown group exhibited a decrease in the colony size of the iPS cells. The HIF-2α or -3α knockdown group demonstrated a statistically significant decrease in the transcription factor expression compared to that observed in the control group. These results demonstrate that HIF-2α among HIFs is the most influential candidate for the maintenance of the pluripotency of murine iPS cells.