Hypoxia induces an early primitive streak signature, enhancing spontaneous elongation and lineage representation in gastruloids

The cellular microenvironment together with intrinsic regulators shapes stem cell identity and differentiation capacity. Mammalian early embryos are exposed to hypoxia in vivo and appear to benefit from hypoxic culture in vitro. Yet, how hypoxia influences stem cell transcriptional networks and lineage choices remain poorly understood. Here we investigated the molecular effects of acute and prolonged hypoxia on embryonic and extraembryonic stem cells as well as the functional impact on differentiation potential. We find a temporal and cell type-specific transcriptional response including an early primitive streak signature in hypoxic embryonic stem cells (ESCs) mediated by HIF1. Using a 3D gastruloid differentiation model, we show that hypoxia-induced T expression enables symmetry breaking and axial elongation in the absence of exogenous WNT activation. When combined with exogenous WNT activation, hypoxia enhances lineage representation in gastruloids, as demonstrated by highly enriched signatures of gut endoderm, notochord, neuromesodermal progenitors and somites. Our findings directly link the microenvironment to stem cell function and provide a rationale supportive of applying physiological conditions in models of embryo development. Refer to individual Series

细胞微环境与内在调控因子共同塑造干细胞的身份及其分化潜能。哺乳动物早期胚胎在体内处于低氧环境，且在体外低氧培养条件下似乎更具生长优势。然而，低氧如何影响干细胞的转录调控网络与谱系选择，目前仍未得到充分阐明。本研究探究了急性与长期低氧对胚胎干细胞（embryonic stem cells, ESCs）和胚外干细胞的分子效应，及其对分化潜能的功能性影响。我们发现存在时间与细胞类型特异性的转录应答，其中包括由HIF1α介导的低氧胚胎干细胞早期原条特征。借助三维类原肠胚分化模型，我们证实低氧诱导的T基因表达可在无需外源性WNT激活的情况下，促成对称性破缺与轴向延伸。当与外源性WNT激活联合应用时，低氧可增强类原肠胚中的谱系表征，具体表现为肠内胚层、脊索、神经中胚层祖细胞及体节的特征基因集显著富集。本研究直接将微环境与干细胞功能建立关联，为在胚胎发育模型中应用生理培养条件提供了理论支撑。请参阅各独立系列。