Background and Objectives The physiological oxygen tension in fetal brains (∼3%, physioxia) is beneficial for the maintenance of neural stem cells (NSCs). Sensitivity to oxygen varies between NSCs from different fetal brain regions, with midbrain NSCs showing selective susceptibility. Data on Hif-1α/Notch regulatory interactions as well as our observations that Hif-1α and oxygen affect midbrain NSCs survival and proliferation prompted our investigations on involvement of Notch signalling in physioxia-dependent midbrain NSCs performance. Methods and Results Here we found that physioxia (3% O2) compared to normoxia (21% O2) increased proliferation, maintained stemness by suppression of spontaneous differentiation and supported cell cycle progression. Microarray and qRT-PCR analyses identified significant changes of Notch related genes in midbrain NSCs after long-term (13 days), but not after short-term physioxia (48 hours). Consistently, inhibition of Notch signalling with DAPT increased, but its stimulation with Dll4 decreased spontaneous differentiation into neurons solely under normoxic but not under physioxic conditions. Conclusions Notch signalling does not influence the fate decision of midbrain NSCs cultured in vitro in physioxia, where other factors like Hif-1α might be involved. Our findings on how physioxia effects in midbrain NSCs are transduced by alternative signalling might, at least in part, explain their selective susceptibility to oxygen.

中文翻译：

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Notch 不参与中脑神经干细胞中生理氧介导的干细胞维持。

背景和目的胎儿大脑中的生理氧张力（~3%，生理氧）有利于神经干细胞（NSC）的维持。来自不同胎儿大脑区域的神经干细胞对氧气的敏感性不同，中脑神经干细胞表现出选择性敏感性。Hif-1α/Notch 调控相互作用的数据以及我们对 Hif-1α 和氧气影响中脑 NSC 存活和增殖的观察促使我们对 Notch 信号传导参与缺氧依赖性中脑 NSC 性能的研究。方法和结果我们发现，与常氧（21% O2）相比，生理氧（3% O2​​）可增加增殖，通过抑制自发分化来维持干性，并支持细胞周期进程。微阵列和 qRT-PCR 分析发现，长期（13 天）后中脑 NSC 中 Notch 相关基因发生显着变化，但短期生理缺氧（48 小时）后没有显着变化。一致的是，DAPT 对 Notch 信号传导的抑制增加，但 Dll4 对其的刺激仅在常氧条件下（而非理氧条件下）减少了向神经元的自发分化。结论 Notch信号通路不影响体外培养的中脑神经干细胞在生理氧条件下的命运决定，而Hif-1α等其他因素可能参与其中。我们关于中脑 NSC 中的缺氧效应如何通过替代信号转导的研究结果可能至少部分解释了它们对氧气的选择性敏感性。