Department of Immunobiology, University of Arizona, Tucson, AZ 85719, USA.
Department of Immunobiology, University of Arizona, Tucson, AZ 85719, USA; Department of Neurology, University of Arizona, Tucson, AZ 85719, USA.
Neurobiol Dis. 2018 Apr;112:63-78. doi: 10.1016/j.nbd.2018.01.007. Epub 2018 Jan 10.
Following stroke, the damaged tissue undergoes liquefactive necrosis, a stage of infarct resolution that lasts for months although the exact length of time is currently unknown. One method of repair involves reactive astrocytes and microglia forming a glial scar to compartmentalize the area of liquefactive necrosis from the rest of the brain. The formation of the glial scar is a critical component of the healing response to stroke, as well as other central nervous system (CNS) injuries. The goal of this study was to evaluate the toxicity of the extracellular fluid present in areas of liquefactive necrosis and determine how effectively it is segregated from the remainder of the brain. To accomplish this goal, we used a mouse model of stroke in conjunction with an extracellular fluid toxicity assay, fluorescent and electron microscopy, immunostaining, tracer injections into the infarct, and multiplex immunoassays. We confirmed that the extracellular fluid present in areas of liquefactive necrosis following stroke is toxic to primary cortical and hippocampal neurons for at least 7 weeks following stroke, and discovered that although glial scars are robust physical and endocytic barriers, they are nevertheless permeable. We found that molecules present in the area of liquefactive necrosis can leak across the glial scar and are removed by a combination of paravascular clearance and microglial endocytosis in the adjacent tissue. Despite these mechanisms, there is delayed atrophy, cytotoxic edema, and neuron loss in regions adjacent to the infarct for weeks following stroke. These findings suggest that one mechanism of neurodegeneration following stroke is the failure of glial scars to impermeably segregate areas of liquefactive necrosis from surviving brain tissue.
中风后，受损组织会发生液化性坏死，这是梗死灶溶解的一个阶段，尽管确切的持续时间目前尚不清楚，但该阶段可以持续数月。修复方法之一是反应性星形胶质细胞和小胶质细胞形成胶质瘢痕，将液化性坏死区域与大脑的其他部分隔离开来。胶质瘢痕的形成是中风以及其他中枢神经系统（CNS）损伤后修复反应的一个关键组成部分。本研究的目的是评估液化性坏死区域中细胞外液的毒性，并确定其与大脑其余部分的有效隔离程度。为了实现这一目标，我们使用了中风的小鼠模型，结合细胞外液毒性测定、荧光和电子显微镜、免疫染色、梗塞内示踪剂注射以及多重免疫分析。我们证实，中风后液化性坏死区域中存在的细胞外液对原代皮质和海马神经元至少在中风后 7 周内具有毒性，并且发现尽管胶质瘢痕是坚固的物理和内吞屏障，但它们仍然是可渗透的。我们发现，液化性坏死区域中存在的分子可以穿过胶质瘢痕，并通过邻近组织中的血管周围清除和小胶质细胞内吞作用被清除。尽管存在这些机制，但在中风后数周内，梗塞周围区域仍会出现延迟性萎缩、细胞毒性水肿和神经元丢失。这些发现表明，中风后神经退行性变的一种机制是胶质瘢痕不能将液化性坏死区域与存活的脑组织完全隔离开来。
