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

项目概要/摘要 神经损伤患者面临终身的感觉运动缺陷，尽管显微外科手术不断改善 技术和神经再生。这些通常被认为是由于穷人或非特异性再生 周围神经然而，当设计实验性神经损伤时， 用于快速、特异和有效的神经再生和肌肉神经再支配的动物模型。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，在本发明中， 可以预见，神经再生的未来进展将受到这种研究较少的缺陷的限制。 中枢突触可塑性值得注意的是，Ia传入本体感受轴突的中央突触分支 在神经损伤导致功能障碍后，从脊髓腹角移除外周损伤的 关键的电机控制电路。我们最近发现，这种突触可塑性是分级的类型的神经 损伤和相关的或多或少的靶特异性在肌肉神经再支配。我们 初步数据表明，神经炎症发生在原本完整的脊髓腹角内， 对于根据神经损伤的严重程度对回路重塑进行分级至关重要。小脑角小胶质细胞被激活 在神经损伤后，尽管经常提出它们的突触吞噬能力， 远端神经损伤后脊髓内的功能仍然存在争议。此外，我们发现， 小胶质细胞活化之后是来自适应性和先天性外周免疫系统的细胞的浸润， 但这取决于损伤类型。当发生时，它与最大Ia突触和轴突相关 从腹角切除这些细胞，特别是单核细胞/巨噬细胞在以前的研究中被遗漏了。 因为它们与活化的小胶质细胞有许多共同的标志物，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还未被研究。我们将使用遗传学方法 区分小胶质细胞和血液来源的免疫细胞，并研究其对Ia传入清除的意义。 在目标1中，我们将对每种细胞类型进行遗传标记和操作，以测试它们在Ia轴突和突触中的作用 缺失和探针细胞信号传导机制。在目标2中，我们将使用延时双光子 显微镜遗传标记的感觉传入和小胶质细胞或单核细胞衍生的细胞，以直接观察 并分析它们的相互作用。最后，在目标3中，我们将测试这种机制与运动功能的相关性， 无论是适应不良，导致长期的运动缺陷或适应，以保持最佳功能可能 当外围连接在再生之后变得高度混乱时。所产生的新知识将 使我们能够考虑通过调节中枢神经系统来优化中枢神经系统功能的新方法。 神经炎症这将是至关重要的发展战略，以改善感觉运动功能的恢复， 结合提高周围轴突再生速度、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.