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疾病之一。 不幸的是，目前还没有针对脊髓损伤患者的有效治疗方法。发展新型维修 减轻脊髓损伤的破坏性并将其转化为临床的策略是迫切的医疗需求 为我们患有脊髓损伤的退伍军人。为了在脊髓损伤后进行功能恢复，再生的轴突需要遵循 移植细胞/生长因子的拓扑图，并与特定的神经元或 树枝状建筑的亚区。腰椎运动神经元(MN)是运动的最终共同通路 输出到后肢，并经历树突萎缩和突触剥离后，以上水平的脊髓损伤。这个 我们研究的目标是重建跨越病变间隙的神经回路，并促进功能恢复 在SCI之后。我们假设由移植的雪旺细胞(SCs)组成的促生长途径 过表达一种名为胶质细胞系衍生神经营养因子(GDNF)的生长因子将促进生长 DPST轴突穿过病变间隙并向尾部延伸至腰椎 这些轴突将与腰椎MN形成靶向特异性突触接触 过度表达一种名为神经营养素-3(NT-3)的神经营养因子。我们还假设，这样的组合 与任何一种单一治疗方法相比，两种方法都能更好地恢复功能。使用与临床相关的 脊髓9(T9)节段挫伤模型移植SCs-GDNF形成连续轴突 脊髓损伤内外的促生长途径和表达NT-3的腺相关病毒2型 (AAV2-NT-3)基因转移方法增强腰椎MN中NT-3的表达，我们将确定(1) 移植SCs-GDNF形成的连续轴突促生长通路是否促进DPST 脊髓挫伤后轴突生长，支配腰椎MNS池，增强 电生理和运动恢复；(2)是否结合轴突生长促进途径 SCs-GDNF与NT-3在腰髓核的表达将协同增强大鼠腰髓核的神经支配 DPST在腰椎MN上的轴突，因此，与任何一种相比，促进更好的功能恢复 (3)DPST-MN神经传递对大鼠后肢运动功能恢复是否必要。 联合治疗；(4)DPST-MN重建后腰椎MNS的分子特征 回路和突触发生。这项提案的完成将使我们能够揭示 重建DPST-MN通路的神经回路并寻找新的运动治疗策略 临床相关的挫伤性脊髓损伤后的康复。

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.