Effects of hypoxia inducible factors on pluripotency in human iPS cells

A hypoxic condition is known to contribute to pluripotency. In the present article, the effects of transcription factors were first assessed regarding the proliferation and differentiation of human induced pluripotent stem (iPS) cells under hypoxic conditions using cell morphology and real-time polymerase chain reaction (RT-PCR). Morphology evaluations and RT-PCR revealed that the colony formation was promoted and the expression of pluripotent markers was increased under hypoxic conditions. In addition, the function of hypoxia inducible factors (HIFs) in human iPS cells under hypoxic conditions was evaluated in relation to the morphology and the expression of pluripotency markers by siRNA and RT-PCR. The HIF-2 silencing group showed a reduction in the colony size of human iPS cells and a statistically significant reduction in the expression of undifferentiation markers compared to the control group. Furthermore, the expression of HIF-2 was decreased when signal transducer and activator of transcription 3 (STAT3) was suppressed by its inhibitor, Stattic or S31 201. The inhibition using Stattic did not produce colony formation. The expression of pluripotent markers was also decreased using Stattic or S31 201. This study indicates that the HIF-2 expression in human iPS cells was activated under hypoxic conditions, similarly to that in murine iPS cells, and that HIF-2 among HIFs is the most effective compound for maintaining the pluripotency of human iPS cells. Furthermore, the STAT3 signal pathway regulates the expression of HIF-2.