Rice Rachel A, Pham Jason, Lee Rafael J, Najafi Allison R, West Brian L, Green Kim N
Department of Neurobiology and Behavior, Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, California, 92697.
Plexxikon Inc, Berkeley, California, 94710.
Glia. 2017 Jun;65(6):931-944. doi: 10.1002/glia.23135. Epub 2017 Mar 2.
Microglia mediate chronic neuroinflammation following central nervous system (CNS) disease or injury, and in doing so, damage the local brain environment by impairing recovery and contributing to disease processes. Microglia are critically dependent on signaling through the colony-stimulating factor 1 receptor (CSF1R) and can be eliminated via administration of CSF1R inhibitors. Resolving chronic neuroinflammation represents a universal goal for CNS disorders, but long-term microglial elimination may not be amenable to clinical use. Notably, withdrawal of CSF1R inhibitors stimulates new microglia to fully repopulate the CNS, affording an opportunity to renew this cellular compartment. To that end, we have explored the effects of acute microglial elimination, followed by microglial repopulation, in a mouse model of extensive neuronal loss. Neuronal loss leads to a prolonged neuroinflammatory response, characterized by the presence of swollen microglia expressing CD68 and CD45, as well as elevated levels of cytokines, chemokines, complement, and other inflammatory signals. These collective responses are largely resolved by microglial repopulation. Furthermore, microglial repopulation promotes functional recovery in mice, with elevated plus maze performance matching that of uninjured mice, despite the loss of 80% of hippocampal neurons. Analyses of synaptic surrogates revealed increases in PSD95 and synaptophysin puncta with microglial repopulation, suggesting that these cells sculpt and regulate the synaptic landscape. Thus, our results show that short-term microglial elimination followed by repopulation may represent a clinically feasible and novel approach to resolve neuroinflammatory events and promote brain recovery.
小胶质细胞介导中枢神经系统(CNS)疾病或损伤后的慢性神经炎症,在此过程中,通过损害恢复过程并促进疾病进展来破坏局部脑环境。小胶质细胞严重依赖集落刺激因子1受体(CSF1R)的信号传导,并且可以通过给予CSF1R抑制剂来清除。解决慢性神经炎症是中枢神经系统疾病的一个普遍目标,但长期清除小胶质细胞可能不适用于临床。值得注意的是,停用CSF1R抑制剂会刺激新的小胶质细胞重新完全填充中枢神经系统,为更新这个细胞区室提供了机会。为此,我们在广泛神经元损失的小鼠模型中探索了急性清除小胶质细胞,随后小胶质细胞重新填充的效果。神经元损失会导致长期的神经炎症反应,其特征是存在表达CD68和CD45的肿胀小胶质细胞,以及细胞因子、趋化因子、补体和其他炎症信号水平升高。这些共同反应在很大程度上通过小胶质细胞的重新填充得到解决。此外,小胶质细胞的重新填充促进了小鼠的功能恢复,尽管海马神经元损失了80%,但高架十字迷宫实验表现的提高与未受伤小鼠相当。对突触替代物的分析显示,随着小胶质细胞的重新填充,PSD95和突触素的斑点增加,这表明这些细胞塑造并调节突触景观。因此,我们的结果表明,短期清除小胶质细胞后再进行重新填充可能代表一种临床上可行的新方法,以解决神经炎症事件并促进脑恢复。