Constructing a growth-promoting pathway for functional regeneration after SCI

项目摘要 脊髓损伤（SCI）是影响美国军队受伤人员的最严重的致残性疾病之一。 不幸的是，SCI患者没有有效的治疗方法。开发新型修复 减轻SCI的破坏性并将其转化为临床的策略是迫切的医疗需求 为我们的退伍军人与SCI。对于SCI后发生的功能恢复，再生的轴突需要遵循 移植的细胞/生长因子的拓扑结构，并与特定的神经元亚群进行准确的连接， 树突状结构的亚区。腰椎运动神经元（MN）是运动的最终共同通路， 输出到后肢，并且它们在高于水平的SCI后经历树突萎缩和突触剥离。的 我们的研究目标是重建跨越损伤间隙的神经回路并促进功能恢复 SCI之后我们假设由移植的雪旺细胞（SC）组成的生长促进途径， 过度表达一种叫做胶质细胞源性神经营养因子（GDNF）的生长因子， 下行固有脊髓束（dPST）轴突穿过病变间隙，向尾侧延伸至腰椎 MNs在宿主脊髓中，这些轴突将与腰椎MNs形成靶向特异性突触接触 过度表达一种叫做神经营养素-3（NT-3）的神经营养素。我们还假设，这种组合 该方法将导致比任何单一治疗更大的功能恢复。使用临床相关的 在第9胸（T9）水平的挫伤性SCI模型中，移植SCs-GDNF以形成连续的轴突 跨越SCI的生长促进途径和表达NT-3的腺相关病毒血清型2 （AAV2-NT-3）基因转移方法增强腰椎MN中NT-3表达，我们将确定（1） 移植的SCs-GDNF形成的连续轴突生长促进途径是否会促进dPST 轴突生长通过和超越挫伤性SCI，支配腰椎MN池，并增强 电生理和运动恢复;（2）是否结合轴突生长促进途径 由SCs-GDNF与腰椎MN中NT-3的表达形成的复合物将协同增强腰椎MN的神经支配。 dPST轴突上的腰椎MN，因此，促进更好的恢复功能相比， 单独治疗;（3）dPST-MN神经传递是否是后肢运动恢复所必需的， 联合治疗;（4）dPST-MN重建后腰椎MN的分子特征 电路和突触发生。完成这一提案将使我们能够揭示基本的机制， 重建dPST-MN通路的神经回路，并确定新的运动治疗策略， 临床相关挫伤性SCI后的恢复。

Project Summary Spinal cord injury (SCI) is among the most disabling conditions affecting wounded members of the U.S. military. Unfortunately, no effective treatment has been available for patients with SCI. Developing novel repair strategies to mitigate the devastating nature of SCI and translating them to the clinic are urgent medical needs for our veterans with SCI. For functional recovery to occur after a SCI, regenerated axons need to follow the topography of grafted cells/growth factors and make accurate connections with specific subsets of neurons or subregions of dendritic architecture. The lumbar motoneurons (MNs) are the final common pathways for motor output to the hindlimbs and they undergo dendritic atrophy and synaptic stripping after an above-level SCI. The goal of our research is to reestablish neural circuitry across the lesion gap and to promote functional recovery after SCI. We hypothesize that a growth promoting pathway composed of grafted Schwann cells (SCs) overexpressing a growth factor called glial cell line-derived neurotrophic factor (GDNF) will promote the growth of descending propriospinal tract (dPST) axons across the lesion gap with extension caudally to the lumbar MNs in the host spinal cord, and that these axons will form target-specific synaptic contacts with lumbar MNs overexpressing a neurotrophin called neurotrophin-3 (NT-3). We also hypothesize that such a combinatorial approach will lead to greater recovery of function than either single treatment. Using a clinically-relevant contusive SCI model at the 9th thoracic (T9) level, transplantation of SCs-GDNF to form a continuous axonal growth-promoting pathway across and beyond a SCI, and adeno-associated virus serotype 2 expressing NT-3 (AAV2-NT-3) gene transfer approach to enhance NT-3 expression in lumbar MNs, we will determine (1) whether a continuous axonal growth-promoting pathway formed by grafted SCs-GDNF will promote dPST axonal growth through and beyond a contusive SCI, innervate the lumbar MNs pools, and enhance electrophysiological and locomotor recoveries; (2) whether combining the axonal growth-promoting pathway formed by SCs-GDNF with expression of NT-3 in lumbar MNs will synergistically enhance the innervation of dPST axons on lumbar MNs and, therefore, promote better recovery of function as compared to either treatment alone; (3) whether dPST-MN neurotransmission is necessary for hindlimb locomotor recovery in the combinatorial treatment; and (4) the molecular signature of lumbar MNs after the reestablishment of dPST-MN circuitry and synaptogenesis. Completion of this proposal will allow us to reveal mechanisms fundamental to rebuilding neural circuitry of the dPST-MN pathway and to identify new therapeutic strategies for locomotor recovery after clinically-relevant contusive SCIs.