Activity-dependent functional regeneration after SCI and OEC transplantation

描述(申请人提供)：我们最近关于嗅鞘胶质细胞(OEC)移植潜力的两项研究为成年大鼠完全脊髓横断后功能重建和感觉运动恢复提供了确凿证据。基于这些发现，嗅鞘细胞处理诱导的轴突再生促进了一些所需的感觉运动功能，但抑制了其他功能。这项建议提出，是否可以通过不同的基于活动的干预措施在幅度和特异性上增强OEC对后肢运动功能的影响。中心假设是，OEC的再生效果可以通过活动依赖的机制来增强，例如硬膜外脊髓刺激(ES)结合5-羟色胺能激动剂，以及为运动任务(攀登或台阶训练)进行训练。我们实验室的许多工作都集中在慢性、低强度ES对完全瘫痪哺乳动物的影响上，尽管机制尚不清楚，ES加上5-羟色胺能激动剂Qupazine激活了腰骶神经回路，极大地增强了脊髓大鼠的运动能力。我们最近在人体模型上的研究表明，当ES与运动训练相结合时，可以触发功能性再生事件，恢复独立站立和对下肢运动的意志控制。为了进一步开发策略来放大先前观察到的OEC介导的效应的大小，提出了两个特定的目标，使用成纤维细胞和OEC治疗的完全脊髓横断大鼠，以及广泛的电生理、解剖学和功能评估。具体目标1将确定嗅鞘细胞移植的再生效果是否大于成纤维细胞对照组，以及ES和奎帕嗪(调节脊髓兴奋性)或“自愿”启动的攀登训练(参与脊髓上通路)是否将促进嗅鞘细胞促进的轴突再生和感觉运动恢复。特定目的2询问ES和自愿攀登训练的联合治疗或ES和跑步机台阶训练的联合治疗是否增强了嗅鞘细胞移植的再生效果。我们预计嗅鞘细胞移植所启动的再生的大小和特异性都将通过ES和爬升训练得到最大程度的增强，这些干预措施将刺激脊髓上和固有脊髓网络，以改善选定的感觉运动任务的执行。这些研究的创新特征包括对清醒行为的脊髓大鼠的诱发电位进行复杂的测量，一系列全面的功能评估工具，以及用于检测脊髓上和固有脊髓神经元再生的跟踪实验。这些研究的意义在于确定横断部位的轴突再生量和已建立的重新连接的特异性都可以通过活动依赖机制来增强的程度。最终，这种机制可能是增强嗅鞘细胞移植对完全瘫痪的脊髓损伤患者的功能益处的最佳候选机制之一。

DESCRIPTION (provided by applicant): Our two recent studies on the potential of olfactory ensheathing glial cell (OEC) transplantation provide conclusive evidence of functional re-connectivity and sensorimotor recovery in adult rats after a complete spinal cord transection. Based on these findings, the axon regeneration induced by OEC treatment facilitated some desired sensorimotor functions, but suppressed others. This proposal asks if the OEC effect on hindlimb motor function can be enhanced in both magnitude and specificity with different activity- based interventions. The central hypothesis is that the regenerative effects of OEC can be enhanced by activity-dependent mechanisms, such as epidural spinal cord stimulation (ES) combined with a serotonergic agonist, and training for a motor task (climbing or step training). Much work from our laboratory has focused on the effects of chronic, low intensity ES in completely paralyzed mammals, and although the mechanism is still unclear, ES plus the serotonergic agonist quipazine activates the lumbosacral neural circuitry and greatly enhances locomotion in spinal rats. Our recent work in a human model shows that ES, when combined with motor training, can trigger functional regenerative events and recovery of independent standing and volitional control of lower limb movements. To further develop strategies to amplify the magnitude of the OEC-mediated effects observed previously, two Specific Aims are proposed using fibroblast- and OEC-treated complete spinal cord transected rats and extensive electrophysiological, anatomical, and functional assessments. Specific Aim 1 will determine whether the regenerative effects of OEC transplantation are greater than those of the fibroblast controls, and if ES and quipazine (to modulate spinal excitability) or a "voluntarily" initiated training of a climbing task (to engage supraspinal pathways) will promote OEC-facilitated axonal regeneration and sensorimotor recovery. Specific Aim 2 asks if the regenerative effects of OEC transplantation are more robust when enhanced by the combined treatments of ES and voluntary climb training or the treatments of ES and treadmill step training. We anticipate that both the magnitude and specificity of the regeneration initiated by OEC transplantation will be most enhanced by ES and climb training, and that these interventions will stimulate the supraspinal and propriospinal networks to improve performance of selected sensorimotor tasks. Innovative features of these studies include the sophisticated measurements of evoked potentials in awake behaving spinal rats, a comprehensive battery of functional evaluation tools, and tracing experiments to detect regeneration of supraspinal and propriospinal neurons. The significance of these studies is to determine the extent to which both the amount of axon regeneration across the transection site and the specificity of the established re-connections can be enhanced by activity-dependent mechanisms. Ultimately, such mechanisms may be among the best candidates to enhance the functional benefits derived from OEC transplantation in completely paralyzed SCI patients.