Neuroinflammation Grading and Adjusting of Spinal Sensorimotor Circuitries in Response to Remote Injuries in Peripheral Nerves

项目摘要/摘要 尽管显微外科技术不断进步，神经损伤患者仍面临终身感觉运动缺陷 技术和神经再生。这些通常被认为是由于较差的或非特异性的再生所致。 周围神经的损伤。然而，当实验性神经损伤被设计在 快速、特异和有效的神经再生和肌肉再神经支配的动物模型。我们有 提出神经损伤后脊髓回路的结构重塑是部分原因。因此， 可以预见的是，神经再生的未来进展将受到因此而引起的缺陷的限制 中枢突触可塑性。值得注意的是，Ia传入本体感觉轴突的中央突触分支 在损伤的外周神经损伤后从脊髓腹角移除导致功能障碍 关键的马达控制电路。我们最近发现，这种突触可塑性被归类为神经的类型 损伤并与肌肉神经再支配过程中获得的或多或少的靶点特异性相关。我们的 初步数据显示，发生在原本完整的脊髓腹角内的神经炎症， 对于根据神经损伤的严重程度对电路重塑进行分级至关重要。腹角小胶质细胞被激活 在神经损伤后，尽管它们的突触吞噬能力经常被提出，但它们的 远端神经损伤后脊髓内的功能仍在争论中。此外，我们发现， 小胶质细胞激活之后是适应性和先天外周免疫系统的细胞渗透， 但这是根据受伤类型的不同而变化的。当发生时，它与最大Ia突触和轴突相关 从腹角移除。这些细胞，特别是单核/巨噬细胞，在以前的 研究是因为它们与激活的小胶质细胞有许多共同的标记，从而阻止了它们的识别。因此，他们的 神经损伤后脊髓腹角内的功能尚不清楚。我们将使用遗传方法来 区分小胶质细胞和血源性免疫细胞，并探讨它们在Ia传入清除中的意义。 在目标1中，我们将对每种细胞类型进行基因标记和操作，以测试它们在Ia轴突和突触中的作用 缺失和探测细胞信号机制。在目标2中，我们将用时间推移双光子来可视化 显微镜直接观察基因标记的感觉传入细胞和小胶质细胞或单核细胞来源的细胞 并分析它们之间的相互作用。最后，在目标3中，我们将测试该机制与运动功能的相关性， 无论是适应不良，造成持久的运动缺陷，还是适应性，尽可能地保持最佳功能 当再生后外设连接变得高度混乱时。所产生的新知识将 允许我们考虑通过调制中央电路来优化中央电路功能的新方法 神经炎。这将是关键的发展战略，以改善感觉运动功能恢复 结合提高外周轴突再生的速度、效率和特异性的方法。

Project Summary / Abstract Nerve injury patients face life-long sensorimotor deficits despite continued improvements in microsurgical techniques and nerve regeneration. These are usually believed to result from poor or unspecific 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. We have proposed that structural remodeling of spinal cord circuitry after nerve lesions is in part responsible. Thus, future advances in nerve regeneration will predictably be limited by deficits caused by this much less studied central synaptic plasticity. Remarkably, the central synaptic branches of Ia afferent proprioceptive axons injured in the periphery are removed from the spinal cord ventral horn after nerve injury resulting in dysfunction of critical motor control circuits. We recently found that this synaptic plasticity is graded to the type of nerve injury and correlated with the more or less target specificity obtained during muscle reinnervation. Our preliminary data suggest that neuroinflammation occurring inside the otherwise intact spinal cord ventral horn, is critical for grading circuit remodeling to the severity of the nerve injury. Ventral horn microglia are activated after nerve injuries and although their capacity for synapse phagocytosis has been frequently proposed, their function inside the spinal cord after a remote nerve injury continues to be debated. Moreover, we found that microglia activation is followed by infiltration of cells from the adaptive and innate peripheral immune system, but this is variable depending on injury type. When occurs, it correlates with maximal Ia synapse and axon removal from the ventral horn. These cells, particularly monocyte/macrophages were missed in previous studies because they share many markers with activated microglia, preventing their identification. Thus, their function inside the spinal cord ventral horn after nerve injury is unexplored. We will use genetic approaches to distinguish microglia from blood-derived immune cells and investigate their significance for Ia afferent removal. In Aim 1 we will genetically label and manipulate each cell type to test their roles in Ia axon and synapse deletions and probe cellular signaling mechanisms. In Aim 2 we will visualize with time-lapse two-photon microscopy genetically labeled sensory afferents and microglia or monocyte-derived cells to directly observe and analyze their interactions. Finally, in Aim 3 we will test the relevance of this mechanism for motor function, whether is maladaptive, causing long-lasting motor deficits or adaptive, to preserve the best function possible when peripheral connectivity becomes highly scrambled after regeneration. The new knowledge generated will allow us to consider new methods for optimization of central circuitry function through modulation of central neuroinflammation. This will be critical for developing strategies to improve sensorimotor function recovery in conjunction with methods to improve the speed, efficiency and specify of axon regeneration in the periphery.