Engineering astroglial bridges for axons across severe SCI lesions

解剖学上完全的脊髓损伤（SCI）横断并消除了所有的功能连接， 在成年人中，轴突不能在这种损伤中自发地再生。恢复 自愿控制功能将需要干预，以建立新的神经连接， 损伤。在此赠款的上一个资助周期中，我们确定了一种基于机制的生物修复 在啮齿类动物中实现完整SCI损伤中本体脊髓轴突稳健再生长的策略。 我们发现，在发育过程中，提供三种轴突生长所必需的机制，（i）神经元 内在生长能力，（ii）生长支持底物和（iii）化学吸引，可以实现稳健 轴突再生通过和超出解剖学上完整的SCI。轴突的再生是 比对照组更大，通过了一个完整的脊髓节段超过受伤，并能够恢复 在损伤处有显著的电生理传导能力。为了实现空间和 为了实现这种轴突再生，我们设计了时间控制的体内分子递送， 生物材料仓库，使我们能够模拟某些时空事件调节轴突生长， 发展在这里提出的项目中，我们将在这项工作的基础上，使用我们新开发的 合成水凝胶载体以递送指导移植的神经细胞在体内分化的分子 祖细胞（NPC）转化为轴突支持的未成熟星形胶质细胞， 并重建有利于宿主固有脊髓长期支持的多细胞神经环境 轴突被化学吸引通过损伤再生成备用的神经组织。我们的假设是 用未成熟的星形胶质细胞重新填充（和“重新神经化”）这种非神经损伤核心或它们的囊肿， 促进轴突的长期维持，并为髓鞘再生细胞提供有利的生态位。我们 目标是开发便于这样做的工程方法。我们的前提是我们的水凝胶 载体可以递送：（i）指导NPC体内分化的分子，和（ii）分子 化学吸引宿主轴突我们过去的工作和初步的数据表明，NPC接枝在我们的水凝胶 载体是产生宿主轴突以及宿主来源的轴突的支持细胞的良好候选者。 少突胶质细胞祖细胞迁移到移植细胞的区域。我们还表明， 脊髓本体神经元是桥接宿主轴突穿过完整的SCI损伤进入保留的 神经组织下面受伤。该提案的工作将促进机制的发展- 严重SCI、中风和其他CNS疾病后修复神经组织的基础工程方法 有很大的病灶

Anatomically complete spinal cord injury (SCI) transects and eliminates all functional connections across the level of the lesion, and in adults, axons fail to regrow spontaneously across such lesions. Restoring voluntary control of function will require interventions to establish new neural connections across the lesion. During the previous funding cycle of this grant, we identified a mechanism-based biological repair strategy for achieving robust regrowth of propriospinal axons across complete SCI lesions in rodents. We showed that providing three mechanisms essential for axon growth during development, (i) neuron intrinsic growth capacity, (ii) growth-supportive substrate and (iii) chemoattraction, can achieve robust regrowth of axons through and beyond anatomically complete SCI. This axon regrowth was 100-fold greater than controls, passed a full spinal segment beyond the injuries, and was able to restore significant electrophysiological conduction capacity across injuries. To achieve the spatially and temporally controlled in vivo molecular delivery required to realize this axon regrowth, we engineered biomaterial depots that enabled us to mimic certain spatiotemporal events regulating axon growth during development. In the project proposed here, we will build on this work and use our newly developed synthetic hydrogel vehicle to deliver molecules that direct the differentiation in vivo of grafted neural progenitor cells (NPC) into axon-supportive immature astroglia that repopulate non-neural lesion cores and reestablish a multicellular neural environment favorable for long term support of host propriospinal axons chemoattracted to regrow through lesions into spared neural tissue. Our hypothesis is that repopulating (and ‘reneuralizing’) such non-neural lesion cores, or their cysts, with immature astroglia will promote long-term axonal maintenance and provide a favorable niche for remyelinating cells. Our objective is to develop engineering approaches that facilitate doing so. Our premise is that our hydrogel vehicles can deliver both: (i) molecules that direct the differentiation of NPC in vivo, and (ii) molecules that chemoattract host axons. Our past work and preliminary data show that NPC grafted in our hydrogel vehicles are good candidates to generate support cells for host axons as well as for host-derived oligodendrocyte progenitor cells that migrate into areas of grafted cells. We have also shown that propriospinal neurons are good targets for bridging host axons across complete SCI lesions into spared neural tissue below injuries. The work for this proposal will advance the development of mechanism- based engineering approaches to repair neural tissue after severe SCI, stroke and other CNS disorders with large focal lesions.