Achucarro Basque Center for Neuroscience, Science Park University of the Basque Country EHU/UPV, Leioa, Spain.
Department of Neuroscience, University of the Basque Country UPV/EHU, Leioa, Spain.
Epilepsia. 2020 Nov;61(11):2593-2608. doi: 10.1111/epi.16692. Epub 2020 Sep 17.
Microglial phagocytosis of apoptotic cells is an essential component of the brain regenerative response during neurodegeneration. Whereas it is very efficient in physiological conditions, it is impaired in mouse and human mesial temporal lobe epilepsy, and now we extend our studies to a model of progressive myoclonus epilepsy type 1 in mice lacking cystatin B (CSTB).
We used confocal imaging and stereology-based quantification of apoptosis and phagocytosis of the hippocampus of Cstb knockout (KO) mice, an in vitro model of phagocytosis and siRNAs to acutely reduce Cstb expression, and a virtual three-dimensional (3D) model to analyze the physical relationship between apoptosis, phagocytosis, and active hippocampal neurons.
Microglial phagocytosis was impaired in the hippocampus of Cstb KO mice at 1 month of age, when seizures arise and hippocampal atrophy begins. This impairment was not related to the lack of Cstb in microglia alone, as shown by in vitro experiments with microglial Cstb depletion. The phagocytosis impairment was also unrelated to seizures, as it was also present in Cstb KO mice at postnatal day 14, before seizures begin. Importantly, phagocytosis impairment was restricted to the granule cell layer and spared the subgranular zone, where there are no active neurons. Furthermore, apoptotic cells (both phagocytosed and not phagocytosed) in Cstb-deficient mice were at close proximity to active cFos neurons, and a virtual 3D model demonstrated that the physical relationship between apoptotic cells and cFos neurons was specific for Cstb KO mice.
These results suggest a complex crosstalk between apoptosis, phagocytosis, and neuronal activity, hinting that local neuronal activity could be related to phagocytosis dysfunction in Cstb KO mice. Overall, these data suggest that phagocytosis impairment is an early feature of hippocampal damage in epilepsy and opens novel therapeutic approaches for epileptic patients based on targeting microglial phagocytosis.
小胶质细胞吞噬凋亡细胞是神经退行性变过程中大脑再生反应的一个重要组成部分。虽然在生理条件下它的效率非常高，但在小鼠和人类内侧颞叶癫痫中它的效率受损，现在我们将研究扩展到缺乏胱抑素 B (CSTB) 的进行性肌阵挛性癫痫 1 型小鼠模型。
我们使用共聚焦成像和基于体视学的定量分析，研究了 Cstb 敲除 (KO) 小鼠海马的凋亡和吞噬作用，体外吞噬作用模型和 siRNAs 急性降低 CSTB 表达，以及虚拟三维 (3D) 模型来分析凋亡、吞噬作用和活性海马神经元之间的物理关系。
在 1 月龄时，即癫痫发作开始和海马萎缩开始时，Cstb KO 小鼠海马中的小胶质细胞吞噬作用受损。这种损伤与小胶质细胞中缺乏 Cstb 无关，因为体外实验表明小胶质细胞中的 Cstb 耗竭不会引起这种损伤。吞噬作用的损伤也与癫痫无关，因为它在癫痫发作前的 14 日龄的 Cstb KO 小鼠中也存在。重要的是，吞噬作用的损伤仅限于颗粒细胞层，而 spared 了没有活性神经元的颗粒下区。此外，Cstb 缺陷型小鼠中的凋亡细胞（吞噬和未吞噬的）与活性 cFos 神经元接近，并且虚拟 3D 模型表明凋亡细胞与 cFos 神经元之间的物理关系是 Cstb KO 小鼠特有的。
这些结果表明凋亡、吞噬作用和神经元活动之间存在复杂的相互作用，提示局部神经元活动可能与 Cstb KO 小鼠的吞噬作用功能障碍有关。总的来说，这些数据表明吞噬作用受损是癫痫中海马损伤的早期特征，并为基于靶向小胶质细胞吞噬作用的癫痫患者提供了新的治疗方法。
Zotero 插件
