Spinal cord neuroinflammation and synaptic plasticity after peripheral nerve injury

周围神经损伤后脊髓神经炎症和突触可塑性

• 批准号: 9512062
• 负责人: FRANCISCO J ALVAREZ
• 金额: $ 38.45万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9512062
• 关键词: American; Animal Model; Axon; Biological; Blood; CCL2 gene; Cells; Complement; Data; Development; Disease; Electromyography; Excision; Feedback; Functional disorder; Genetic; Goals; Horns; Image; Immune; Individual; Infiltration; Injury; Joints; Knowledge; Label; Left; Length; Lesion; Ligands; Locomotion; Measures; Mediating; Microglia; Microscopy; Motor; Motor Neurons; Motor output; Movement; Mus; Muscle; Natural regeneration; Nerve; Nerve Regeneration; Operative Surgical Procedures; Outcome; Pathway interactions; Patients; Pattern; Peripheral; Peripheral Nerves; Peripheral nerve injury; Phagocytes; Phagocytosis; Pharmacology; Play; Process; Property; Reaction; Recovery; Recruitment Activity; Reporting; Role; Sensory; Severities; Signal Transduction; Specificity; Spinal; Spinal Cord; Stretching; Synapses; Synaptic plasticity; T-Lymphocyte; Techniques; Testing; Time; Ventral Horn of the Spinal Cord; Work; awake; axon regeneration; cell type; chemokine receptor; design; genetic manipulation; improved; injured; insight; macrophage; migration; monocyte; motor control; motor deficit; motor disorder; nerve injury; nerve supply; neural circuit; neuroinflammation; novel strategies; outcome forecast; peripheral nerve regeneration; prevent; reinnervation; response; stretch reflex; time use; tool; treadmill; two-photon

Project Summary / Abstract Every year nearly one million Americans undergo surgery for nerve reattachment after nerve injuries, but despite continued improvements in microsurgical techniques, a majority of these patients are left with permanent motor deficits. Usually these are believed to result from poor regeneration of the peripheral nerve. However, deficits are still present when experimental nerve injuries are designed in animal models for rapid, specific and efficient nerve regeneration and muscle re-innervation. In the past we reported that structural remodeling of spinal cord circuitry after nerve lesions is in part responsible. After injury, the central synaptic branches of sensory proprioceptive axons and motor axons injured in the periphery are removed from the ventral horn of the spinal cord resulting in dysfunction of several critical motor control circuits. The mechanisms of synapse and axon removal are therefore clearly important, but unknown. Our preliminary data implicate the neuroinflammatory response that occurs inside the intact spinal cord around cell bodies of peripherally-injured motoneurons and along the central projections of peripherally-injured sensory axons. Microglia is activated in these regions and although their capacity for synapse phagocytosis has been frequently proposed, their exact function after nerve injury remains controversial. In addition, monocytes infiltrate the spinal cord and transform into macrophages. These cells were missed in previous studies because they become indistinguishable from microglia. Thus, their interactions with resident microglia and possible roles in synaptic plasticity are unknown. More recently we found that after nerve injuries triggering large synaptic circuit remodeling there is additional infiltration by T-cells. The roles T-cells play in synaptic remodeling are completely unknown. To investigate the relation between microglia and different immune cell infiltrates in relation to synapse plasticity we will use mice in which microglial cells are labeled with GFP and infiltrating immune cells by RFP and perform a number of genetic manipulations to interfere with the function of one or other cell and test possible signaling mechanisms leading to microglia activation, immune cell infiltration and synapse removal. In Aim 1 we will investigate the role of peripherally derived monocytes, macrophages and T-cells in the synaptic removal of inputs from muscle sensory afferents. In Aim 2 we will investigate whether microglia activation is necessary for recruitment of blood-derived immune cells and investigate the signals promoting these invasion. In Aim 3 we will use two- photon time-lapse imaging to directly observe and analyze the process of removal of sensory synapses and the mechanisms that facilitate specific recognition of axons injured in the peripheral nerve. Finally, in Aim 4 we will block the central neuroinflammatory response to preserve proprioceptive synaptic inputs and test patterns of muscle activation during treadmill locomotion after nerve regeneration with electromyography. The results will inform about the role of neuroinflammation and the cellular mechanisms involved in removing specific inputs from the spinal cord and will provide first insights into motor outcomes after interfering with this process.

项目概要/摘要 每年有近百万美国人在神经损伤后接受神经复位手术，但是 尽管显微外科技术不断进步，但大多数患者仍面临着 永久性运动缺陷。通常这些被认为是由于周围神经再生不良造成的。 然而，当在动物模型中设计实验性神经损伤以进行快速、 特定且有效的神经再生和肌肉重新神经支配。过去我们报道过结构性 神经损伤后脊髓回路的重塑是部分原因。受伤后，中枢突触 将外周受伤的感觉本体轴突和运动轴突的分支从 脊髓腹角导致几个关键运动控制回路功能障碍。机制 因此，突触和轴突的去除显然很重要，但尚不清楚。我们的初步数据表明 发生在外周损伤细胞体周围完整脊髓内的神经炎症反应 运动神经元和沿着外周受伤的感觉轴突的中央投影。小胶质细胞被激活于 这些区域，虽然人们经常提出它们的突触吞噬能力，​​但它们的确切作用 神经损伤后的功能仍存在争议。此外，单核细胞浸润脊髓并转化 进入巨噬细胞。这些细胞在之前的研究中被遗漏了，因为它们与 小胶质细胞。因此，它们与驻留小胶质细胞的相互作用以及在突触可塑性中可能的作用尚不清楚。 最近我们发现，在神经损伤触发大的突触回路重塑后，还有额外的 T 细胞浸润。 T 细胞在突触重塑中的作用尚不清楚。为了调查 小胶质细胞和不同免疫细胞浸润之间与突触可塑性的关系我们将使用小鼠 其中小胶质细胞被 GFP 标记，并通过 RFP 浸润免疫细胞，并执行许多操作 基因操作干扰一种或其他细胞的功能并测试可能的信号机制 导致小胶质细胞激活、免疫细胞浸润和突触去除。在目标 1 中，我们将调查 外周来源的单核细胞、巨噬细胞和 T 细胞在突触清除肌肉输入中的作用 感觉传入。在目标 2 中，我们将研究小胶质细胞激活对于招募 血液来源的免疫细胞并研究促进这些入侵的信号。在目标 3 中，我们将使用两个 - 光子延时成像可直接观察和分析感觉突触的去除过程 促进对周围神经损伤的轴突进行特异性识别的机制。最后，在目标 4 中，我们 将阻断中枢神经炎症反应，以保留本体感觉突触输入和测试模式 肌电图神经再生后跑步机运动过程中的肌肉激活。结果 将告知神经炎症的作用以及去除特定的细胞机制 来自脊髓的输入，并将在干扰这一过程后提供对运动结果的初步了解。