Enhancing the Reparative Efficacy of Schwann Cells following Chronic SCI

描述 在美国，慢性脊髓损伤（SCI）影响着超过125万人，每年有超过11，000例新的损伤。恢复是有限的，因为成年哺乳动物中枢神经系统（CNS）的切断轴突无法再生。在SCI修复实验模型中采用的多种治疗策略中，细胞移植桥接损伤部位并为轴突再生提供基质已成为许多有前途的急性，亚急性和慢性治疗的基础。迄今为止，我们的工作集中在许旺细胞（SC），周围神经再生和修复的关键外周胶质细胞，解剖和功能恢复受损的脊髓的效用。在许多实验性SCI模型（完全和不完全;颈和胸;急性和慢性）中，SC可以促进解剖修复和功能恢复的改善。重要的是，SC可以从SCI个体的外周神经活检中获得，纯化并在培养物中扩增至大量用于随后的自体植入。正是由于这些有益的效果，迈阿密项目最近向美国食品和药物管理局提交了一份研究性新药申请，请求允许进行自体干细胞用于亚急性人类SCI修复的1期临床试验。 尽管取得了这一成功，但事实仍然是SC迁移在受损脊髓内非常有限，这可能会显著降低其治疗效果。缺乏迁移限制了SC引导轴突进入和离开病变的能力，以及阻止SC到达远端脱髓鞘区域以促进髓鞘再生修复。因此，我们认为，细胞表面的聚唾液酸（PSA）的能力，以促进细胞迁移在正常发育过程中可能会利用SC翻译的方法。我们最近在亚急性SCI中表明，当SC被遗传修饰以表达高水平的PSA时，它们可以容易地在受损的脊髓内迁移，并且这种SC修饰导致SCI后显著更大的轴突再生和功能恢复。我们工作的下一步，如本提案所示，是通过优化和扩展PSA在SCI中的应用，特别是治疗慢性SCI，更接近治疗相关性。该研究计划旨在首先通过使用纯化的聚唾液酸转移酶（从细菌中获得）直接在SC和/或轴突上合成PSA来改善PSA-SC方法的实用性，从而避免在亚急性和慢性SCI的实验范例中使用基因治疗来实现这一目标（具体目标1）。然后，该提案试图了解PSA改变许旺细胞迁移能力并提高许旺细胞轴突生长促进能力的机制。（具体目标2）。由于这项工作的最终目标是改善体内SCI修复，这些研究将不仅在我们操作的细胞和组织生物学方面进行评估，而且还将在广泛的行为测试中测量这些程序对功能结果的影响。拟议的工作将提供重要的数据，使我们能够扩大我们的初步临床试验的范围与SC从亚急性到慢性SCI，以及提供容易翻译的组合方法，可以puperminally提高疗效的SC临床亚急性和慢性SCI。

DESCRIPTION Chronic spinal cord injury (SCI) affects more than 1.25 million people in the United States, with more than 11,000 new injuries sustained annually. Recovery is limited because severed axons of the adult mammalian central nervous system (CNS) are unable to regenerate. Of the multiple treatment strategies employed in experimental models for SCI repair, cellular grafting to bridge the injury site and provide a substrate for axonal re-growth has been a foundation for many of the promising acute, sub-acute and chronic therapies. Our work to date has focused on the utility of the Schwann cell (SC), a peripheral glial cell critical for peripheral nerve regeneratio and repair, to anatomically and functionally restore the injured spinal cord. SCs can facilitate anatomical repair and improvements in functional recovery in a number of experimental SCI models (complete and incomplete; cervical and thoracic; acute and chronic). Importantly, SCs could be obtained from a peripheral nerve biopsy from a SCI individual, purified and expanded to large numbers in culture for ensuing autologous implantation. It is because of these beneficial effects that The Miami Project recently submitted to The Food and Drug Administration an Investigational New Drug Application to request permission to undertake a Phase 1 clinical trial with autologous SCs for sub-acute human SCI repair. Despite this success, the fact remains that SC migration is very limited within the injured spinal cord, which is likely to significantly lessen their therapeutic efficacy. A lack of migration limits the ability of SCs to guide axons bot into and from the lesion as well as prevents SCs from reaching regions of distal demyelination so as to facilitate re-myelination repair. It therefore occurred to us that the ability of cell surace polysialylic acid (PSA) to facilitate cell migration during normal development might be exploited in the SC translational approach. We have recently shown in sub-acute SCI that SCs can readily migrate within the injured spinal cord when they have been genetically modified to express high levels of PSA, and that this SC modification leads to significantly greater axon regeneration and functional restitution following SCI. The next step in our work, as represented in this proposal, is to move closer to therapeutic relevance through the optimization and extension of the use of PSA in SCI, particularly to the treatment of chronic SCI. The research plan seeks to achieve that goal first by improvement in the practicality of the PSA-SC approach through the use of the purified polysialyltransferase (obtained from bacteria) to synthesize PSA directly on SCs and/or axons, thus avoiding the use of gene therapy in experimental paradigms of sub-acute and chronic SCI (Specific Aim 1). The proposal then seeks to understand the mechanism(s) by which PSA alters the migratory capacity of Schwann cells and improves the axon growth promoting ability of Schwann cells. (Specific Aim 2). As the ultimate goal of this work is to improve SCI repair in vivo, these studies will be evaluated not only in terms of the cel and tissue biology of our manipulations, but also the effect of those procedures on functional outcomes as measured in extensive behavioral testing. The proposed work will provide important data to allow us to expand the scope of our initial clinical trial with SCs from sub-acut to chronic SCI as well as provide readily translatable combinatory approaches that can putatively enhance the effectiveness of SCs clinically in both sub-acute and chronic SCI.