Matsuba Yukio, Nagata Kenichi, Kadota Yosuke, Sahara Naruhiko, Saido Takaomi C, Hashimoto Shoko
Pionnering Research Division, Medical Innovation Research Center, Shiga University of Medical Science, Seta Tsukinowa-Cho, Otsu, Shiga, 520-2192, Japan.
Laboratory for Proteolytic Neuroscience, RIKEN Center for Brain Science, 2-1 Hirosawa, Wako-City, Saitama, 351-0198, Japan.
J Neuroinflammation. 2025 Jul 16;22(1):184. doi: 10.1186/s12974-025-03504-5.
Microglia, resident immune cells of the central nervous system, play an essential role in responding to pathological conditions by adopting diverse activation states and morphologies. Recent single-cell RNA sequencing have revealed that microglial subtypes were heterogeneous based on their gene expression profiles. However, the mechanism on how morphological changes in microglia are correlated with their gene expression profiles remains unclear. The current study aimed to identify a distinct population of rod-shaped microglia, characterized by an elongated morphology, in glutamyl cysteine ligase (GCLC)-deficient mice, a model of glutathione deficiency-induced oxidative stress. In the process of brain atrophy accompanied by neuronal cell death, which was observed in GCLC-KO mice, the rod-shaped microglia emerged in early stages of neurodegeneration and subsequently decreased in number over time. C1q-mediated synaptic pruning has been implicated in microglial activation under pathological conditions. Thus, whether C1q contributes to the formation of rod-shaped microglia was investigated. Notably, the genetic deletion of C1q did not affect the number or distribution of rod-shaped microglia in GCLC-KO mice. These findings suggest that their formation occurs via a C1q-independent mechanism. According to morphological and molecular analyses, the gene expression profile of the rod-shaped microglia was similar to that of the disease-associated microglia (DAM). To investigate the mechanisms underlying their formation, single-nucleus RNA sequencing was performed on cortical tissues collected from GCLC-KO mice. DAM-like microglial clusters were consistently identified. Further, pathway enrichment analysis suggested the potential involvement of the urokinase-type plasminogen activator (uPA, encoded by Plau) signaling. Considering the role of uPA in extracellular matrix degradation and cell migration, it may contribute to the morphological changes in rod-shaped microglia. In addition, the phosphorylation of growth-associated protein 43 (GAP43), a modification linked to structural plasticity, increased in rod-shaped microglia. Based on these findings, uPA signaling and phosphorylated GAP43 may be involved in microglial elongation and alignment along neuronal fibers, which potentially facilitate their migration during early neurodegenerative responses. Taken together, the rod-shaped microglia are a previously unrecognized activated population that emerges early in neurodegeneration and may be involved in disease-related processes. Understanding their molecular regulation can provide insights into early microglial responses and potential therapeutic targets.
小胶质细胞是中枢神经系统的常驻免疫细胞，通过呈现不同的激活状态和形态在应对病理状况中发挥重要作用。最近的单细胞RNA测序显示，小胶质细胞亚型基于其基因表达谱具有异质性。然而，小胶质细胞形态变化如何与其基因表达谱相关的机制仍不清楚。当前研究旨在在谷氨酰半胱氨酸连接酶（GCLC）缺陷小鼠（一种谷胱甘肽缺乏诱导的氧化应激模型）中鉴定出一群以细长形态为特征的杆状小胶质细胞。在GCLC基因敲除小鼠中观察到的伴有神经元细胞死亡的脑萎缩过程中，杆状小胶质细胞在神经退行性变的早期出现，随后数量随时间减少。C1q介导的突触修剪与病理条件下的小胶质细胞激活有关。因此，研究了C1q是否有助于杆状小胶质细胞的形成。值得注意的是，C1q的基因缺失并不影响GCLC基因敲除小鼠中杆状小胶质细胞的数量或分布。这些发现表明它们的形成通过一种不依赖C1q的机制发生。根据形态学和分子分析，杆状小胶质细胞的基因表达谱与疾病相关小胶质细胞（DAM）相似。为了研究其形成的潜在机制，对从GCLC基因敲除小鼠收集的皮质组织进行了单核RNA测序。持续鉴定出了类似DAM的小胶质细胞簇。此外，通路富集分析表明尿激酶型纤溶酶原激活剂（uPA，由Plau编码）信号可能参与其中。考虑到uPA在细胞外基质降解和细胞迁移中的作用，它可能导致杆状小胶质细胞的形态变化。此外，生长相关蛋白43（GAP43）的磷酸化（一种与结构可塑性相关的修饰）在杆状小胶质细胞中增加。基于这些发现，uPA信号和磷酸化的GAP43可能参与小胶质细胞沿神经元纤维的伸长和排列，这可能在早期神经退行性反应中促进它们的迁移。综上所述，杆状小胶质细胞是一种先前未被认识的激活群体，在神经退行性变早期出现，可能参与疾病相关过程。了解它们的分子调控可以为早期小胶质细胞反应和潜在治疗靶点提供见解。
