Reactive oxygen species (ROS) produced by NADPH1 oxidase 1 (NOX1) are thought to drive spermatogonial stem cell (SSC) self-renewal through feed-forward production of ROS by the ROS-BCL6B-NOX1 pathway. Here we report the critical role of oxygen on ROS-induced self-renewal. Cultured SSCs proliferated poorly and lacked BCL6B expression under hypoxia despite increase in mitochondria-derived ROS. Due to lack of ROS amplification under hypoxia, NOX1-derived ROS were significantly reduced, and Nox1-deficient SSCs proliferated poorly under hypoxia but normally under normoxia. NOX1-derived ROS also influenced hypoxic response in vivo because Nox1-deficient undifferentiated spermatogonia showed significantly reduced expression of HIF1A, a master transcription factor for hypoxic response. Hypoxia-induced poor proliferation occurred despite activation of MYC and suppression of CDKN1A by HIF1A, whose deficiency exacerbated self-renewal efficiency. Impaired proliferation of Nox1- or Hif1a-deficient SSCs under hypoxia was rescued by Cdkn1a depletion. Consistent with these observations, Cdkn1a-deficient SSCs proliferated actively only under hypoxia but not under normoxia. On the other hand, chemical suppression of mitochondria-derived ROS or Top1mt mitochondria-specific topoisomerase deficiency did not influence SSC fate, suggesting that NOX1-derived ROS play a more important role in SSCs than mitochondria-derived ROS. These results underscore the importance of ROS origin and oxygen tension on SSC self-renewal.

中文翻译：

---

NOX1衍生的ROS和氧气的相互作用决定了缺氧条件下精原干细胞的自我更新效率

NADPH1 氧化酶​​ 1 (NOX1) 产生的活性氧 (ROS) 被认为通过 ROS-BCL6B-NOX1 途径前馈产生 ROS 来驱动精原干细胞 (SSC) 自我更新。在这里，我们报告了氧气对 ROS 诱导的自我更新的关键作用。尽管线粒体衍生的 ROS 增加，但培养的 SSCs 在缺氧条件下增殖不良且缺乏 BCL6B 表达。由于在缺氧条件下缺乏 ROS 扩增，NOX1 衍生的 ROS 显着减少，并且Nox1缺陷型SSC 在缺氧条件下增殖不良，但在常氧条件下增殖正常。NOX1 衍生的 ROS 也影响体内的缺氧反应，因为Nox1-缺陷的未分化精原细胞显示 HIF1A 的表达显着降低，HIF1A 是缺氧反应的主要转录因子。尽管 MYC 激活和 HIF1A 抑制 CDKN1A，但缺氧诱导的增殖不良仍然存在，HIF1A 的缺乏加剧了自我更新效率。Cdkn1a耗尽挽救了缺氧条件下Nox1或Hif1a 缺陷型SSC的增殖受损。与这些观察结果一致，缺乏 Cdkn1a的 SSC 仅在缺氧条件下活跃增殖，但在常氧条件下不活跃。另一方面，化学抑制线粒体衍生的 ROS 或Top1mt线粒体特异性拓扑异构酶缺乏不会影响 SSC 的命运，这表明 NOX1 衍生的 ROS 在 SSC 中的作用比线粒体衍生的 ROS 更重要。这些结果强调了 ROS 来源和氧张力对 SSC 自我更新的重要性。