Engineering astroglial bridges for axons across severe SCI lesions

解剖完全性脊髓损伤(SCI)横断并消除所有横跨 损伤的水平，以及在成人中，轴突不能自发地在这些损伤中再生。正在恢复 对功能的自愿控制将需要干预来建立新的神经连接 损伤。在这笔赠款的前一个资金周期中，我们确定了一种基于机制的生物修复 在啮齿动物完全脊髓损伤中实现固有脊髓轴突强健再生的策略。 我们发现在发育过程中为轴突生长提供了三种必不可少的机制：(I)神经元 内在的生长能力，(Ii)支持生长的底物和(Iii)化学吸引，可以实现强劲的 轴突在解剖上完全性脊髓损伤后的再生。轴突再生是原来的100倍。 超过对照组，通过了超过损伤的完整脊柱节段，并能够恢复 显著的跨损伤电生理传导能力。实现空间和空间上的 实现轴突再生所需的时间控制的体内分子传递，我们设计了 生物材料库，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 合成水凝胶载体运送引导移植神经体内分化的分子 将祖细胞(NPC)转化为轴突支持的未成熟星形胶质细胞，重新填充非神经病变核心 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病变重新生长到备用的神经组织中。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)这样的非神经病变核心或它们的包囊 促进轴突的长期维持，为再生髓鞘细胞提供有利的利基。我们的 目标是开发促进这一点的工程方法。我们的前提是我们的水凝胶 载体可以传递：(I)在体内引导鼻咽癌分化的分子，以及(Ii)分子 这种化学物质能吸引宿主轴突。我们过去的工作和初步数据表明，在我们的水凝胶中接枝了NPC 载体是为宿主轴突和宿主来源的细胞产生支持细胞的很好的候选者 向移植细胞区域迁移的少突胶质前体细胞。我们还表明， 固有脊髓神经元是跨越完整脊髓损伤的宿主轴突连接到备用损伤的良好靶点 损伤下方的神经组织。这项建议的工作将推动机制的发展-- 基于工程学方法修复严重脊髓损伤、中风和其他中枢神经系统疾病后的神经组织 有较大的局灶性病变。

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.