Peripheral Nerve Regeneration and Sensory Neuron Plasticity

描述(由申请人提供)：急性周围神经损伤后的慢性疼痛是一个主要的公共卫生问题。我们在这项建议中的主要目标是了解损伤和再生后皮肤和肌肉感觉神经元可塑性的细胞过程。具体地说，我们将研究损伤诱导的初级感觉神经元重新神经支配皮肤或横纹肌的可塑性。在第一个目标中，我们使用体外皮肤或肌肉/神经/背根神经节/脊髓标本和我们的新方法来恢复单个功能特征的感觉神经元，以确定幼鼠皮肤C纤维和IV类肌肉传入的综合表型。这包括对单个具有功能特征的纤维的基因表达谱进行表征。在我们的初步研究中，我们已经确定了这些纤维的几个独特的功能类别。在第二个目标中，我们将首先研究神经损伤对重新支配皮肤或肌肉的个别特征纤维的功能特性和相关基因表达变化的影响。在我们的初步研究中，我们证实并扩展了早期的研究，即这些纤维在再生后会敏化。此外，我们的结果表明，一些纤维正在改变表型。接下来，我们将研究这些纤维中特定的Trk、GFRpha、ASIC、Trp和嘌呤能受体/通道的DRG表达的变化，以确定导致神经损伤和再生后观察到的功能变化的可能分子机制。在第三个目标中，我们将使用我们的新的体内siRNA敲除技术来验证以下假设：损伤导致特定受体/通道(如ASIC、Trp和嘌呤能)表达的增加介导了特定人群皮肤和肌肉传入的功能可塑性。例如，我们希望发现，抑制皮肤神经损伤和再生后TRPM3表达水平的增加将阻止观察到的皮肤C-多模式纤维对热的敏化。同样，我们预计，肌肉神经损伤和再生后ASIC3表达的下调将阻止肌肉传入对机械刺激的敏感化。负责这些纤维敏化的特定受体/通道的确定将 为这些过程提供新的见解，更重要的是可以为药物疗法的发展提供潜在的目标。这些新疗法可以为缓解慢性神经性疼痛的不良症状提供改进的治疗方法。

DESCRIPTION (provided by applicant): Chronic pain following acute peripheral nerve injury is a major public health issue. Our primary goal in this proposal is to understand the cellular processes that underlie plasticity in cutaneous and muscle sensory neurons following injury and regeneration. Specifically, we will look at injury-induced plasticity of primary sensory neurons reinnervating either skin or striated muscle. In the first aim, we use ex vivo skin or muscle/nerve/DRG/spinal cord preparations and our novel method for recovering individual functionally characterized sensory neurons to determine the comprehensive phenotypes of cutaneous C-fibers and Group IV muscle afferents in naive mice. This includes characterization of the gene expression profiles of the individual functionally characterized fibers. In our preliminary studies we have indentified several unique functional classes of these fibers. In the second aim, we will first examine the effects of nerve injury on the functional properties and correlated changes in gene expression in individual characterized fibers reinnervating skin or muscle. In our preliminary studies we have confirmed and expanded upon earlier studies showing that these fibers are sensitized following regeneration. In addition, our results suggest that some fibers are changing phenotype. Next we will examine changes in DRG expression of specific trk, GFRalpha, ASIC, TRP and purinergic receptors/channels contained in these fibers to indentify possible molecular mechanisms responsible for the changes in function observed following nerve injury and regeneration. In the third aim, we will use our novel in vivo siRNA knockdown technique to test the hypothesis that the injury-induced increase in the expression of particular receptors/channels (e.g. ASIC, TRP and purinergic) mediates the observed functional plasticity in specific populations of cutaneous and muscle afferents. For example, we expect to find that knockdown of the increase in TRPM3 expression levels following cutaneous nerve injury and regeneration will block the observed sensitization of cutaneous C-polymodal fibers to heat. Similarly we expect that knockdown in ASIC3 expression following muscle nerve injury and regeneration will block the sensitization of muscle afferents to mechanical stimulation. The determination of the specific receptors/channels responsible for sensitization of these fibers will provide new insights to these processes and more importantly could provide potential targets for the development of pharmaceutical therapies. These new therapies could provide for improved treatments for the alleviation of the adverse symptoms of chronic neuropathic pain.