Mechanisms underlying macrophage action in nerve regeneration and degeneration

周围神经损伤很常见，由各种原因引起，包括创伤、糖尿病、癌症 化疗、自身免疫反应和遗传疾病。尽管外周神经元能够 在再生过程中，这个过程通常是不完整的。因此，确定再生器的方式是至关重要的- 我们可以加强这一点。巨噬细胞被认为可以促进急性脑损伤后周围神经的再生 由于它们聚集在远端神经中而造成的损伤，在那里它们吞噬轴突碎片和髓鞘 创造一个轴突可以生长的环境。此外，巨噬细胞分泌的细胞因子 触发神经中非神经细胞的生长因子合成。这些行动的缺席一直是 被认为是在缓慢退化的Wlds小鼠中发生缓慢再生的基础。怎么- 曾经，它已经被知道了20年。部分原因是我们的学习。Mac上还有第二个不同的地点- 损伤后噬菌体积聚，即周围神经节，如背根神经节(DRGs) 轴突切除的细胞体存在。目前尚不清楚的是，这些巨噬细胞的功能是什么。 我们实验室最近的研究表明，在回答这个问题方面取得了重大进展。与两个突变体一起工作 小鼠品系，趋化因子受体CCR2和Wlds小鼠的敲除导致了这一假说 神经节内巨噬细胞的聚集是发生条件性损伤(CL)反应所必需的。 损伤后突起生长的反应由于较早的情况而增加- ING损伤。此应用程序旨在测试以下整体模型：将巨噬细胞带入 趋化因子CCL2诱导的DRG通过细胞外信号途径启动再生相关基因的表达 轴突周围细胞因子的分泌，从而促进CL反应和再生。 此外，巨噬细胞对远端神经有任何影响。确凿无疑地证明 CCL2依赖的巨噬细胞聚集和CCL2依赖的CL反应是因果相关的， 我们将使用一种集落刺激因子1受体的抑制剂来消耗循环单核细胞。为了阻止- 无论巨噬细胞是否直接作用于神经元细胞体，我们将使用微流室，在微流室中 神经元的胞体和轴突是可以分离的。使用RNAseq的基因表达将在AX-AX之后进行比较 在CCRs-/-和野生型动物中进行切开以确定哪些轴突切断诱导的基因依赖于Mac- 噬菌体堆积。由于我们已经证明了沃勒变性在CCR2-/-小鼠中是正常的，但 单核细胞对DRG的渗透被阻断，这些动物将允许我们确定巨噬细胞 在活体内感觉神经再生需要DRGs的积聚。使用这些新颖的方法，我们 将研究巨噬细胞聚集在轴突附近之间的关系的机制。 胞体和轴突生长。强调神经节，未被探索的神经炎症部位，代表 与关注巨噬细胞对远端神经影响的传统观点相比，这是一种范式转变。

Peripheral nerve injury is common and occurs due to a variety of causes including trauma, diabetes, cancer chemotherapy, autoimmune reactions, and genetic disorders. Although peripheral neurons are capable of regenerating, this process is generally incomplete. It is therefore crucial to determine ways in which regener- ation can be enhanced. Macrophages are thought to promote peripheral nerve regeneration after an acute injury due to their accumulation in the distal nerve where they phagocytize axonal debris and myelin thereby creating an environment through which axons can grow. In addition, macrophages secrete cytokines that trigger growth factor synthesis in non-neuronal cells in the nerve. The absence of these actions has been assumed to be the basis for the slow regeneration that occurs in the slowly degenerating Wlds mouse. How- ever, it has been known for 20 years. In part due to our studies. that there is a second, distinct, site of mac- rophage accumulation after injury, namely, peripheral ganglia such as dorsal root ganglia (DRGs) where the axotomized cell bodies reside. What has remained unknown is what function these macrophages subserve. Recent studies from our lab represent a major advance in answering this question. Work with two mutant mouse strains, a knockout for the chemokine receptor CCR2 and the Wlds mice led to the hypothesis that macrophage accumulation in ganglia is required for the occurrence of the conditioning lesion (CL) response, the response in which neurite outgrowth after a lesion is increased as a consequence of an earlier condition- ing lesion. This application is designed to test the following overall model: macrophages brought into the DRG by the chemokine CCL2 trigger the expression of regeneration associated genes (RAGs) via the secretion of cytokines around axotomized cell bodies and this promotes the CL response and regen- eration in addition to any effects macrophages have on the distal nerve. To establish beyond doubt that CCL2-dependent macrophage accumulation and the CCL2-dependent CL response are causally related, we will use an inhibitor of colony stimulating factor 1 receptors to deplete circulating monocytes. To deter- mine whether macrophages act directly on neuronal cell bodies, we will use microfluidic chambers in which a neuron’s cell body and axon can be separated. Gene expression using RNAseq will be compared after ax- otomy in CCRs -/- and wild type animals to determine which axotomy-induced genes are dependent on mac- rophage accumulation. Since we have shown that Wallerian degeneration is normal in CCR2 -/- mice but monocyte infiltration into DRGs is blocked, these animals will allow us to determine whether macrophage accumulation in DRGs is required for sensory nerve regeneration in vivo. Using these novel approaches, we will examine the mechanisms underlying the relationship between macrophage accumulation near axoto- mized cell bodies and axonal growth. Emphasizing ganglia, unexplored sites of neuroinflammation, repre- sents a paradigm shift from the traditional view that focuses on macrophage effects on the distal nerve.