Wild-type nerve grafting promotes reinnervation of SOD1 muscle

描述(申请人提供)：运动神经元(MN)变性开始于运动神经元病(MND)模型中的神经肌肉接头(NMJ)。NMJ有3种细胞类型：神经元(运动终末)、终末雪旺细胞(TSC)和肌纤维。在前期工作中，我们发现SOD1小鼠的TSCs和终末前雪旺细胞(SCs)从失神经支配的NMJ中迅速消失，而野生型(WT)TSCs保持在去神经支配的NMJ并帮助指导神经再支配。这种SOD1异常可以通过存活MNS来阻碍或阻止失神经肌肉纤维的再神经支配，并加速虚弱的发展。我们考虑了SOD1TSCs腾空的SOD1终板可以被野生型SCs重新占据的可能性。为了测试这一点，我们使用了一种同基因的方法，并将预变性的WT周围神经移植到同时实验去神经的SOD1肌中。初步证据表明，2周后，在移植物存在的情况下，肌肉重新神经支配更快、更强壮，与WT动物的重新神经支配相似。此外，这种神经支配在嫁接后持续更长的时间间隔。在目标1中，我们将扩展这些长期影响的特征，并了解它们是否与减少MN细胞死亡和改善肌肉和运动单位的性能有关。此外，我们将确定在自然疾病过程中，WT移植物是否可以改善或保留肌肉神经。在目标2中，我们将移植原代培养的WT SC、成纤维细胞(FB)和去细胞的WT神经，并了解这些主要移植成分中的哪些对失神经支配的SOD1肌的WT神经移植效果负责。最后，TSCs和远端SCs在失神经支配后不久出现在SOD1肌中，提示它们的消失可能与细胞死亡有关。在目标3中，我们将使用坏死和凋亡的免疫标记来了解SOD1SCs是否在失神经后不久经历细胞死亡，以获得可能的触发机制的线索。我们希望，这种对移植组织/细胞的创新使用将产生可能的治疗方法的新线索，并扩大对干细胞如何促进SOD1小鼠MND的理解。

DESCRIPTION (provided by applicant): Motor neuron (MN) degeneration commences at the neuromuscular junction (NMJ) in the SOD1 model of motor neuron disease (MND). The NMJ features 3 cell types present in close physical proximity: neuronal (motor terminal), terminal Schwann cell (TSC), and muscle fiber. In preliminary work, we found that TSCs and pre-terminal Schwann cells (SCs) in SOD1 mice rapidly disappear from denervated NMJs whereas wildtype (WT) TSCs remain at denervated NMJs and help guide reinnervation. This SOD1 abnormality can be expected to hinder or prevent reinnervation of denervated muscle fibers by surviving MNs and accelerate the development of weakness. We considered the possibility that SOD1 endplates vacated by SOD1 TSCs can be reoccupied by wildtype SCs. To test this, we used a syngeneic approach and grafted pre-degenerated WT peripheral nerves into SOD1 muscles that were experimentally denervated at the same time. Preliminary evidence shows that after 2 weeks, muscle reinnervation is more rapid and robust in the presence of grafts and resembles reinnervation in WT animals. Moreover, this innervation persists at longer, post-grafting intervals. In Aim 1, we will extend the characterization of these long term effects and learn whether they are associated with reduced MN cell death and improved muscle and motor unit performance. In addition, we will determine whether WT grafts can improve or preserve muscle innervation during the natural disease course. In Aim 2, we will graft primary cultured WT SC, fibroblasts (FB) and acellular WT nerves and learn which of these major graft components is responsible for WT nerve graft effects in denervated SOD1 muscle. Finally, the appearance of TSCs and distal SCs in SOD1 muscles soon after denervation suggests that cell death may be involved in their disappearance. In Aim 3, we will use immunolabels for necrosis and apoptosis to learn whether SOD1 SCs experience cell death soon after denervation in order to gain clues about possible trigger mechanisms. We hope that this innovative use of grafting tissue/cells will produce new clues about possible therapies and extend understanding about how SCs contribute to MND in SOD1 mice.