Hypoxic priming of mESCs accelerates vascular‐lineage differentiation through HIF1‐mediated inverse regulation of Oct4 and VEGF

Abstract Hypoxic microenvironment plays an important role in determining stem cell fates. However, it is controversial to which direction between self‐renewal and differentiation the hypoxia drives the stem cells. Here, we investigated whether a short exposure to hypoxia (termed ‘hypoxic‐priming’) efficiently directed and promoted mouse embryonic stem cells (mESCs) to differentiate into vascular‐lineage. During spontaneous differentiation of embryoid bodies (EBs), hypoxic region was observed inside EB spheroids even under normoxic conditions. Indeed, hypoxia‐primed EBs more efficiently differentiated into cells of vascular‐lineage, than normoxic EBs did. We found that hypoxia suppressed Oct4 expression via direct binding of HIF‐1 to reverse hypoxia‐responsive elements (rHREs) in the Oct4 promoter. Furthermore, vascular endothelial growth factor (VEGF) was highly upregulated in hypoxia‐primed EBs, which differentiated towards endothelial cells in the absence of exogenous VEGF. Interestingly, this differentiation was abolished by the HIF‐1 or VEGF blocking. In vivo transplantation of hypoxia‐primed EBs into mice ischemic limb elicited enhanced vessel differentiation. Collectively, our findings identify that hypoxia enhanced ESC differentiation by HIF‐1‐mediated inverse regulation of Oct4 and VEGF, which is a novel pathway to promote vascular‐lineage differentiation.