Induction of reprogramming of human amniotic epithelial cells into iPS cells by overexpression of Yap, Oct4, and Sox2 through the activation of the Hippo-Yap pathway

The present study has reported a novel method for producing induced pluripotent stem (iPS) cells. Primary human amniotic epithelial cells (HuAECs) were isolated from the amniotic membranes of pregnant women who received Cesarean sections. These cells were infected with retroviruses carrying octamer-binding transcription factor 4 (Oct4), (sex determining region Y)-box 2 (Sox2) and Yes-associated protein (Yap) (OSY). Following in vitro culture for ~14 days, epithelial-like HuAECs exhibited several iPS clone-like cell colonies (OSY-iPS). These cell clones presented positive alkaline phosphatase features and expressed high levels of embryonic stem cell-like markers (Nanog homeobox, Sox2, Oct4, reduced expression protein 1, and SSES3/4). Additionally, epigenetic analysis results indicated that the methylation of CpG islands on endogenous Oct4 and Sox2 promoters was reduced in OSY-iPS cells. Furthermore, the majority of the histone H3 at lysine 9 sites that interacted with the Oct4 and Sox2 promoters were acetylated, suggesting that the transcription activities of the above two transcription factors significantly increased. In vivo and in vitro induced differentiation experiments demonstrated that OSY-iPS could develop into embryoid bodies in vitro, and express numerous cellular markers in the three germ layers. Furthermore, OSY-iPS could form teratomas in immunodeficient mice. The pathological detection results suggest that these teratomas contain numerous types of cells from the three germ layers. However, the results from the quantitative polymerase chain reaction and western blot analyses suggest that the Hippo-Yap signaling pathway was significantly activated in OSY-iPS cells. In conclusion, a novel method for iPS induction was established in the present study. HuAECs were successfully induced to reprogram iPS cells through the introduction of OSY to activate the Hippo-Yap signaling pathway.