Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
J Neurosci. 2010 Dec 1;30(48):16272-83. doi: 10.1523/JNEUROSCI.2195-10.2010.
We have shown recently that following saphenous nerve transection and successful regeneration, cutaneous polymodal nociceptors (CPMs) lacking transient receptor potential vanilloid 1 (TRPV1) are sensitized to heat stimuli and that mechanically insensitive, heat-sensitive C-fibers (CHs) that contain TRPV1 increase in prevalence. Target-derived neurotrophic factor levels were also enhanced after axotomy and regeneration. In particular, the glial-cell line-derived neurotrophic factor (GDNF) family member artemin was found to be significantly enhanced in the hairy hindpaw skin and its receptor GDNF family receptor α3 (GFRα3) was increased in the L2/L3 dorsal root ganglia (DRGs) following nerve injury. In this study, we assessed the role of enhanced artemin/GFRα3 levels on the changes in mouse cutaneous CH neurons following saphenous nerve regeneration. We used a newly developed siRNA-mediated in vivo knockdown strategy to specifically inhibit the injury-induced expression of GFRα3 and coupled this with an ex vivo recording preparation to examine response characteristics and neurochemical phenotype of different types of functionally defined neurons after injury. We found that inhibition of GFRα3 did not affect the axotomy-induced decrease in CPM threshold, but transiently prevented the recruitment of CH neurons. Western blot and real-time PCR analysis of hairy hindpaw skin and L2/L3 DRGs after saphenous nerve regeneration suggested that inhibition of the potential initial injury-induced increase in enhanced target-derived artemin signaling resulted in dynamic changes in TRPV1 expression after regeneration. These changes in TRPV1 expression may underlie the functional alterations observed in CH neurons after nerve regeneration.
我们最近已经表明，在隐神经切断和成功再生后，缺乏瞬时受体电位香草素 1（TRPV1）的皮肤多模态伤害感受器（CPMs）对热刺激敏感，并且包含 TRPV1 的机械不敏感、热敏感 C 纤维（CHs）的出现频率增加。轴突切断和再生后，靶源性神经营养因子水平也增强。特别是，胶质细胞系衍生的神经营养因子（GDNF）家族成员 artemin 在毛发后足皮肤中显著增强，其受体 GDNF 家族受体 α3（GFRα3）在神经损伤后 L2/L3 背根神经节（DRGs）中增加。在这项研究中，我们评估了增强的 artemin/GFRα3 水平在隐神经再生后小鼠皮肤 CH 神经元变化中的作用。我们使用新开发的 siRNA 介导的体内敲低策略特异性抑制 GFRα3 的损伤诱导表达，并将其与体外记录准备相结合，以检查不同类型功能定义神经元在损伤后的反应特征和神经化学表型。我们发现，抑制 GFRα3 不会影响 CPM 阈值的轴突切断诱导降低，但会暂时防止 CH 神经元的募集。隐神经再生后毛发后足皮肤和 L2/L3 DRGs 的 Western blot 和实时 PCR 分析表明，抑制潜在的初始损伤诱导的增强的靶源性 artemin 信号的增加导致再生后 TRPV1 表达的动态变化。这种 TRPV1 表达的变化可能是神经再生后 CH 神经元观察到的功能改变的基础。
