Nerve Allotransplantation for Traumatic Nerve Injury

描述（由申请人提供）：周围神经损伤可导致严重和永久性的功能缺陷。同种异体神经移植提供了无限来源的神经移植材料，用于临床重建严重的否则无法修复的创伤性神经损伤。FK506促进神经再生，是预防同种异体移植排斥反应的首选免疫抑制剂，但可能导致显著的患者发病率。本课题的长期目标是制定预防同种异体神经移植排斥反应的策略，同时尽量减少免疫抑制的副作用，从而提高周围神经移植的安全性，拓宽临床适应症。在几种动物模型中，共刺激阻断诱导的供体特异性免疫无反应已被证明可以在保持一般免疫能力的情况下通过同种异体移植物进行神经再生。同样，同种异体神经移植物可以低温保存以降低抗原性，并与宿主雪旺细胞一起播种以促进神经再生。更好地了解同种异体神经移植物的反应、冷保存的影响以及雪旺细胞向神经移植物的迁移，为减少对宿主免疫抑制的需求提供了策略基础。用修饰的宿主雪旺细胞补充同种异体神经移植物可以增强同种异体神经移植物的再生。这些方法将扩大神经同种异体移植的适应症，包括目前使用神经自体移植的较轻的损伤。在目的1a中，使用CD4+和CD8+敲除和MHC类缺陷小鼠来表征同种异体抗原呈递周围神经移植物的直接和间接途径的相对贡献。Aim 1b利用STAT4和STAT6基因敲除小鼠研究同种异体神经移植物冷保存对这些通路的影响。在aim 2a中，在同时阻断CD28/B7和CD40共刺激通路后，评估同种异体神经移植物的再生。在目的2b中，同种异体神经移植物被冷保存以优化共刺激阻断的效果，从而允许同种异体移植物接受。在目的3a中，Thy1-CFP/S100-GFP小鼠被用来表征雪旺细胞在冷保存的异体神经移植物中迁移、分化和成熟。在目的3b中，同种异体神经移植物冷保存7周，然后植入培养的过表达GDNF的自体雪旺细胞，使同种异体神经移植物再生而不产生任何免疫抑制。在目标3中，同样的结构在长猪同种异体移植模型中进行了评估，该模型与临床遇到的长神经缺损非常相似，并且可以移植到神经损伤患者身上。

DESCRIPTION (provided by applicant): Injury to peripheral nerves can result in significant and permanent functional deficits. Nerve allografts offer a limitless source of nerve graft material that is used clinically to reconstruct severe otherwise irreparable traumatic nerve injuries. FK506 enhances nerve regeneration and is the immunosuppressant of choice for preventing allograft rejection, but can cause significant patient morbidity. The long-term objective of this proposal is to develop strategies to prevent nerve allograft rejection while minimizing the side effects of immunosuppression, thereby improving safety and broadening the clinical indications for peripheral nerve allotransplantation. Donor-specific immune unresponsiveness induced by costimulation blockade has been shown to permit nerve regeneration through allografts in several animal models while maintaining general immunocompetence. Similarly nerve allografts can be cold preserved to decrease antigenicity and seeded with host Schwann cells to facilitate nerve regeneration. A better understanding of the nerve allograft response, the effects of cold preservation, and Schwann cell migration into nerve grafts provides a basis for strategies to minimize requirements for host immunosuppression. Supplementation of nerve allografts with modified host Schwann cells may enhance regeneration through nerve allografts. These approaches will expand the indications for nerve allotransplantation to include less severe injuries where nerve autografts are currently used. In aim 1 a the relative contributions of the direct and indirect pathways of alloantigen presentation in peripheral nerve allografts are characterized using CD4+ and CD8+ knockout and MHC class ll-deficient mice. Aim 1b studies the effects of cold preservation of nerve allografts on these pathways using STAT4 and STAT6 gene knockout mice. In aim 2a, regeneration through nerve allografts is evaluated following simultaneous blockade of CD28/B7 and CD40 costimulatory pathways. In aim 2b, nerve allografts are cold preserved to optimize the efficacy of costimulatory blockade to permit allograft acceptance. In aim 3a, Thy1-CFP/S100-GFP mice are used to characterize Schwann cell migration, differentiation, and maturation when repopulating a cold preserved nerve allograft. In aim 3b, nerve allografts are cold preserved for 7 weeks and then seeded with cultured autologous Schwann cells that overexpress GDNF to permit regeneration through nerve allografts without any immunosuppression. In aim 3c this same construct is evaluated in a long swine allograft model that closely resembles the long nerve defects encountered clinically and will allow translation to the nerve-injured patient.