Use of Engineered Nervous Tissue Constructs to Repair Extensive Nerve Injury

描述(申请人提供)：使用工程化神经组织结构修复广泛的神经损伤每年在美国约有36万人遭受周围神经损伤，这是导致终生残疾的主要原因。虽然修复主要周围神经损伤的主要策略是用自体神经移植修复损伤，但制造足够长度和数量的神经是一个巨大的挑战。在周围神经移植修复(即自体神经移植)中，所谓的“金标准”受到供体神经采集耗时和手术并发症的限制。此外，目前用于神经移植修复的大多数替代方法(例如，合成管)在促进修复的跨度方面受到限制，通常用于间隙小于2或3厘米。在这里，我们建议利用一种新的组织工程技术来创造可移植的神经组织结构，用于主要的周围神经修复。这一过程的关键是使用一种特殊设计的微步进电机系统，在培养中跨越两组神经元的轴突上产生持续的机械张力。作为我们的中心假设，我们认为，工程化的活神经组织结构将通过提供一条活的标记路径来引导宿主轴突从近端神经残端穿过大型神经损伤重新支配靶组织，从而促进主要周围神经损伤后的恢复。除了提供一条穿过损伤间隙的通路，我们还提出，来自该结构的轴突将生长到近端和远端的神经残端。在这项提议的第一部分，我们将使用我们新的活的工程化神经组织结构在动物模型中修复急性广泛的急性神经损伤。在这项研究的第二部分，我们将尝试主要重建啮齿类动物的臂丛神经损伤，使用我们的活神经组织结构跨越前肢从椎骨到爪子。我们将直接比较接受含有延长的背根节细胞培养的神经组织结构的动物与接受常规自体神经重建(反向自体移植)、单独使用合成管修复(材料底物对照)、不修复(不处理对照)、免疫抑制对照(每天接受环孢素A注射)和物理康复对照的组的结果。在这项研究的第三部分，我们将评估我们的神经组织结构的免疫原性。我们将调查这一假设，即在我们延长的背根节神经元中缺乏MHC I表达是移植宿主没有发生免疫排斥的主要原因。如果成功，我们的新型组织工程神经构建可能会为主要神经重建方法带来革命性的变化，为周围神经广泛损伤的患者提供实验室培养的“现成”活神经，以便移植。 公共卫生相关性：在这项研究中，我们建议使用一种全新的组织工程技术来创建神经结构，用于修复动物模型中的广泛神经损伤。如果成功，我们的发现将通过为移植提供实验室培养的“现成”活神经，从而使患有毁灭性神经损伤的患者受益。

DESCRIPTION (provided by applicant): Use of Engineered Nervous Tissue Constructs to Repair Extensive Nerve Injury Each year approximately 360,000 people in the United States suffer a peripheral nerve injury, which is a leading source of lifelong disability. While a primary strategy to repair major peripheral nerve injury is to bridge the damage with autologous nerve grafts, producing nerves of sufficient length and number has posed a significant challenge. The so called "gold standard" in peripheral nerve graft repair (i.e. the autologous nerve graft) is limited by the time consuming harvesting of donor nerves and complications arising from the harvesting surgery. In addition, most alternative methods currently used for nerve graft repair (e.g., synthetic tubes) are limited in the length that they can span to promote repair and are typically used for gaps of less than 2 or 3 cm. Here, we propose to utilize a novel tissue engineering technique to create transplantable nervous tissue constructs for major peripheral nerve repair. The key of this procedure is to use a specially designed microstepper motor system to produce continuous mechanical tension on axons spanning two populations of neurons in culture. As our central hypothesis, we propose that engineered living nervous tissue constructs will promote recovery after major peripheral nerve injury by providing a living labeled pathway to guide host axons from the proximal nerve stump across large nerve lesions to reinnervate the target tissue. In addition to providing a pathway through the injured gap, we also propose that axons from the construct will grow into both the proximal and distal nerve stumps. In the first part of this proposal, we will repair acute extensive acute nerve injury in an animal model using our novel living engineered nervous tissue constructs. In the second part of this study, we will attempt major reconstruction of brachial plexus injury in rodents, spanning the forelimb from the vertebrae to the paw using our living nervous tissue constructs. We will directly compare the outcome of animals receiving the nervous tissue construct containing the elongated dorsal root ganglion cell cultures with groups receiving conventional autologous nerve reconstruction (reverse autologous graft), repair with a synthetic tube alone (material substrate control), no repair (no treatment control), immunosuppression control (receiving daily cyclosporine A injection) and physical rehabilitation control. In the third part of this study, we will assess the immunogenicity of our nervous tissue construct. We will investigate the hypothesis that the lack of MHC I expression in our elongated DRG neurons is the main reason that immunorejection does not occur in transplanted hosts. If successful, our novel tissue engineered nerve construct could revolutionize methods for major nerve reconstruction by providing laboratory grown 'off-the-shelf' living nerves ready for transplant in patients with extensive peripheral nerve injuries. PUBLIC HEALTH RELEVANCE: In this study we propose to use a fundamentally novel tissue engineering technique to create nerve constructs for repair of extensive nerve injury in an animal model. If successful, our findings could benefit patients with devastating nerve injuries by providing laboratory grown 'off-the-shelf' living nerves ready for transplant.