Harnessing Neurotropism to Sort Sensory and Motor Axons

利用向神经性对感觉和运动轴突进行分类

• 批准号: 9765432
• 负责人: THOMAS M BRUSHART
• 金额: $ 20.47万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9765432
• 关键词: Address; Amputation; Axon; Code; Collaborations; Collagen; Color; Cutaneous; Data; Dimensions; Encapsulated; Engineering; Environment; Esthesia; Exploratory/Developmental Grant; Goals; Growth Factor; Individual; Laboratories; Laminin; Limb structure; Modality; Modeling; Motor; Muscle; Natural regeneration; Nerve; Nerve Regeneration; Neurotropism; Patients; Peripheral; Peripheral Nerves; Population; Prosthesis; Sensory; Skin; Sorting - Cell Movement; Spinal Cord; Spinal Ganglia; Technology; Testing; Tomatoes; Upper Extremity; Veterans; afferent nerve; axon regeneration; bioprinting; comparative; experimental study; high risk; improved outcome; in vivo; injured; nerve injury; neurotropic; regenerative; repaired; response; success; three-dimensional modeling

Random targeting by regenerating peripheral axons compromises sensory and motor function after nerve repair, and limits the usefulness of regenerative prosthetic interfaces after extremity amputation. Regeneration of motor axons to skin provides no function; regeneration of cutaneous axons to muscle degrades sensation. Similarly, poor sensory/motor localization within the proximal nerve stump after amputation defeats attempts to isolate axons corresponding to specific functions. These problems can be overcome by sorting regenerating axons by modality. However, previous efforts to split axon populations have enjoyed limited success for three reasons: 1)There is little comparative data on which growth factors attract only sensory or only motor axons; 2) In the constructs described so far, few regenerating axons are given equal opportunity to respond to both growth factors; 3) We have recently shown that sensory axons adhere to motor axons and limit their outgrowth, a factor not previously appreciated. The goal of this project is to develop an engineering approach that directs axons regenerating from a mixed nerve trunk into discrete sensory and motor channels. These channels could then be used to innervate individual motor and sensory nerves after nerve injury, or to control individual muscles through a regenerative prosthetic interface. The project tests two core hypotheses: 1) It is possible to identify neurotropic growth factors that direct the regeneration of only motor or only sensory axons (Aim I), and 2) Overlapping gradients of these factors can be used to separate regenerating sensory and motor axons (Aim II). These hypotheses will be tested in our organotypic model of mixed nerve regeneration, in which sensory axons expressing tomato red and motor axons expressing YFP are combined within a three-dimensional segment of peripheral nerve. After this nerve is transected, the color-coded axons grow out onto a featureless collagen/laminin sheet, where their pathfinding can be directed by growth factor gradients. These gradients will be established using micro-encapsulated growth factors and bioprinting technology developed in our laboratory. In Aim I we will evaluate the response of sensory or motor axons to candidate growth factors, modifying growth factor concentrations, gradient steepness, and substrate to maximize axon turning. In Aim II we will generate overlapping gradients of the most effective factors from Aim I while blocking the interaction of sensory and motor axons to maximize their turning. The ability to present regenerating axons with overlapping gradients of truly "motor-only" and "sensory-only" growth factors in an environment that minimizes axon-axon interactions will thus allow us to optimize separation of these axon populations. If successful, this engineering platform could then be used to construct a three-dimensional prosthesis that separates regenerating sensory and motor axons in vivo, which can be used to improve outcomes in the 50,000 patients/year that undergo nerve repair and the nearly 300 veterans with recent upper extremity amputations.

再生外周神经轴突的随机靶向损害神经后的感觉和运动功能 修复，并限制了肢体截肢后再生性假体界面的使用。再生 运动轴突到皮肤的再生没有提供任何功能；皮肤轴突到肌肉的再生会降低感觉。 同样，截肢后感觉/运动在近端神经残端内的不良定位也会挫败 分离与特定功能相对应的轴突。这些问题可以通过排序重新生成来克服 轴突的形态。然而，之前分离轴突种群的努力只取得了有限的成功 原因：1)关于生长因素只吸引感觉轴突还是只吸引运动轴突的比较数据很少；2) 在到目前为止所描述的结构中，很少有再生轴突被给予同等的机会对两者作出反应。 生长因子；3)我们最近发现，感觉轴突附着在运动轴突上，并限制它们的生长。 这是一个以前没有得到重视的因素。该项目的目标是开发一种工程方法，以指导 轴突从混合神经干再生为离散的感觉和运动通道。这些渠道可能 然后用来对神经损伤后的个体运动神经和感觉神经进行神经支配或控制个体 肌肉通过再生假体接口。该项目检验了两个核心假设：1)有可能 确定仅指导运动神经或感觉神经轴突再生的神经营养生长因子(目标I)，以及 2)这些因子的重叠梯度可用于分离再生的感觉轴突和运动轴突(AIM Ii)。这些假说将在我们的混合神经再生的器官模型中得到验证，在该模型中，感觉 表达番茄红的轴突和表达YFP的运动轴突结合在一个三维 周围神经的节段。在这条神经被切断后，颜色编码的轴突生长到一个没有特征的 胶原蛋白/层粘连蛋白片材，其中它们的路径可以通过生长因子梯度来指导。这些渐变将 利用我们开发的微囊化生长因子和生物打印技术建立 实验室。在目标I中，我们将评估感觉轴突或运动轴突对候选生长因子的反应， 改变生长因子浓度、梯度陡度和底物以最大限度地促进轴突转向。在AIM II中 我们将生成来自AIM I的最有效因素的重叠梯度，同时阻止 感觉轴突和运动轴突使其最大限度地转动。以重叠的方式呈现再生轴突的能力 在最小化轴突的环境中，真正的“纯运动型”和“感觉型”生长因子的梯度 因此，相互作用将使我们能够优化这些轴突群体的分离。如果成功，这项工程 然后，可以使用平台来构建三维假体，将再生的感觉分开 和活体内的运动轴突，它们可以用来改善每年50,000名患者的预后 神经修复和最近接受上肢截肢的近300名退伍军人。