Laboratory of Molecular and Cellular Physiology, Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan.
Department of Geriatric Medicine, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.
J Cell Physiol. 2019 Feb;234(2):1689-1698. doi: 10.1002/jcp.27040. Epub 2018 Aug 2.
Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator for the induction of antioxidative genes and plays roles in diverse cellular functions. The roles of Nrf2 in muscle regeneration have been investigated, and both important and unimportant roles of Nrf2 for muscle regeneration have been reported. Here, using aged Nrf2-null and Nrf2-dystrophic double-null mice, we showed nonsignificant phenotypes in the muscle regeneration ability of Nrf2-null mice. In contrast with these results, strikingly, almost all Nrf2-null muscle stem cells (MuSCs) isolated by fluorescence-activated cell sorting died in vitro of apoptosis and were not rescued by antioxidative reagents. Although their proliferation was still impaired, the Nrf2-null MuSCs attached to myofibers activated and divided normally, at least in the first round. To elucidate these discrepancies of MuSCs behaviors, we focused on the basal lamina, because both in vivo and single myofiber culture allow MuSCs within the basal lamina to become activated. In a basal lamina-disrupted model, Nrf2-null mice exhibited remarkable regeneration defects without increased levels of reactive oxidative species in MuSCs, suggesting that the existence of the basal lamina affects the survival of Nrf2-null MuSCs. Taken together, these results suggest that the basal lamina compensates for the loss of Nrf2, independent of the antioxidative roles of Nrf2. In addition, experimental conditions might explain the discrepant results of Nrf2-null regenerative ability.
核因子红细胞 2 相关因子 2（Nrf2）是诱导抗氧化基因表达的主要调节因子，在多种细胞功能中发挥作用。已经研究了 Nrf2 在肌肉再生中的作用，并且报道了 Nrf2 对肌肉再生的重要和不重要作用。在这里，使用老年 Nrf2 基因敲除和 Nrf2 肌营养不良双重基因敲除小鼠，我们发现 Nrf2 基因敲除小鼠的肌肉再生能力没有明显表型。与这些结果形成鲜明对比的是，令人惊讶的是，通过荧光激活细胞分选分离的几乎所有 Nrf2 基因敲除肌肉干细胞（MuSCs）在体外均死于凋亡，并且抗氧化剂不能挽救它们。尽管它们的增殖仍然受到损害，但 Nrf2 基因敲除 MuSCs 仍能正常附着于肌纤维并激活和分裂，至少在第一轮是这样。为了解释这些 MuSCs 行为的差异，我们专注于基底膜，因为在体内和单个肌纤维培养中都允许 MuSCs 位于基底膜内被激活。在基底膜破坏模型中，Nrf2 基因敲除小鼠表现出明显的再生缺陷，而 MuSCs 中的活性氧水平没有增加，这表明基底膜的存在影响了 Nrf2 基因敲除 MuSCs 的存活。总之，这些结果表明基底膜补偿了 Nrf2 的缺失，而与 Nrf2 的抗氧化作用无关。此外，实验条件可能解释了 Nrf2 基因敲除再生能力的差异结果。
