Training Novel Host-Graft Interfaces to Enhance Spinal Cord Repair

描述（由申请人提供）：神经元置换显示出增强脊髓损伤（SCI）后恢复的前景，并且被认为是干细胞介导的脊髓修复的主要目标。然而，实现有效的宿主-移植神经元通信是尚未研究的神经元替代的主要挑战。这个建议的总体假设是，提出新建立的宿主移植神经元网络的生理模式的活动将增强功能连接。基于我们在SCI建模以及呼吸和计算神经生物学方面的丰富经验，我们建议通过将大鼠胚胎脊髓（FSC）组织移植物-神经元祖细胞的来源-移植到成年大鼠的临床相关的高颈（C3）挫伤中来验证这一假设。初步的跨神经元神经解剖追踪数据显示FSC供体细胞与宿主膈运动神经元和颈中间神经元之间的突触连接。此外，FSC移植物从宿主接受广泛的多巴胺能输入，并且一些移植神经元表现出缺氧敏感性放电模式，包括明显的吸气相关爆发。因此，一个先决条件的解剖功能框架是适当的，以测试我们的中心假设，通过以下具体目标，使用FSC移植物放置到成年大鼠C3挫伤损伤：目的1）验证FSC源性神经元在解剖学和生理学上与宿主灰质整合的假设，目的2）验证通过间歇性低氧（IH）刺激的“训练”将增强FSC衍生的神经元的解剖和生理整合的假设。为了验证这些假设，我们将使用多学科的方法，包括移植物和宿主脊髓之间连接的神经解剖学研究，清醒大鼠呼吸的测量，以及移植物的神经生理学研究。我们建议的一个创新技术特征是，这将是第一次使用微电极阵列来监测脊髓中移植物相关的神经集合。将使用FSC移植方法，因为这种移植物发育成含有大量类似中间灰质中间神经元的细胞的有髓组织。将使用一种独特的康复模式-每天暴露于轻度、间歇性缺氧（IH），因为它导致脊髓可塑性与脊髓损伤动物呼吸输出的持续增加相关。同样重要的是，IH提供了一种工具，用于在移植物周围（可能在移植物内）引入或增加适当的图案化破裂。该提案汇集了呼吸神经生理学，计算神经生物学，神经移植和SCI方面的独特专业知识，以促进SCI理解和治疗的变革性进展。 公共卫生相关性：呼吸损害是颈脊髓损伤后的一个重要问题。一种可以增强脊髓损伤后运动恢复的策略是“神经替代”疗法，其中细胞被移植到脊髓损伤中。在这些实验中，我们将研究一种新的康复模式是否可以提高脊髓损伤后神经移植的有效性。

DESCRIPTION (provided by applicant): Neuronal replacement shows promise for enhancing recovery after spinal cord injury (SCI), and is considered a major objective for stem cell-mediated spinal cord repair. Achieving effective host-graft neuronal communication, however, represents a major challenge for neuronal replacement which has not been investigated. The overall hypothesis of this proposal is that presenting newly established host-graft neuronal networks with physiologically-patterned activities will enhance functional connectivity. Based on our extensive experience with SCI modeling and both respiratory and computational neurobiology, we are proposing to test this hypothesis by transplanting rat fetal spinal cord (FSC) tissue grafts - a source of neuronal progenitors - into clinically-relevant, high cervical (C3) contusion injuries in adult rats. Preliminary transneuronal neuroanatomical tracing data show synaptic connectivity between FSC donor cells and host phrenic motoneurons and cervical interneurons. In addition, FSC grafts receive extensive serotonergic inputs from the host, and some graft neurons exhibit hypoxia-sensitive discharge patterns including apparent inspiratory- related bursting. A prerequisite anatomical-functional framework is thus in place to test our central hypothesis via the following specific aims using FSC grafts placed into C3 contusion injuries in adult rats: Aim 1) to test the hypothesis that FSC-derived neurons will become anatomically and physiologically integrated with host gray matter, and Aim 2) to test the hypothesis that "training" via intermittent hypoxia (IH) stimulation will enhance the anatomical and physiological integration of FSC-derived neurons. To test these hypotheses, we will use a multi-disciplinary approach including neuroanatomical studies of connectivity between the graft and host spinal cord, measurement of breathing in awake rats, and neurophysiological studies of the graft. An innovative technical feature of our proposal is that this will be the first use of microelectrode arrays to monitor graft- associated neural ensembles in the spinal cord. A FSC grafting method will be used because such grafts develop into myelinated tissue containing a large contingent of cells resembling intermediate gray matter interneurons. A unique rehabilitative paradigm - daily exposure to mild, intermittent hypoxia (IH) - will be used because it leads to spinal cord plasticity associated with persistent increases in respiratory output in spinal injured animals. Equally important, IH provides a tool to introduce or increase appropriately patterned bursting around, and possibly within, the graft. This proposal brings together unique expertise in respiratory neurophysiology, computational neurobiology, neural transplantation, and SCI in an effort to facilitate transformative advances in the understanding and treatment of SCI. PUBLIC HEALTH RELEVANCE: Respiratory compromise is a significant problem after cervical spinal cord injury. A strategy that may enhance motor recovery after spinal injury is "neural replacement" therapy in which cells are transplanted into the spinal cord lesion. In these experiments, we will examine if a novel rehabilitation paradigm can enhance the effectiveness of a neural transplant following spinal cord injury.