Engineered Matrices with Electrical and Chemical Stimulation for Peripheral Nerve Repair

项目摘要/摘要 在美国，周围神经损伤(PNI)影响着数以百万计的人，间隙较大的PNI需要手术修复。 尽管生物和合成移植物被广泛用于修复有较大间隙的PNI，但它们都会受到 临床结果不太理想。自体移植是治疗的黄金标准，但受到可用性和缺陷的限制。 修复大小，而合成移植物的生物降解性、强度、生物活性和功能性较差。因此， 这项建议的长期目标是设计具有增强的大间隙神经再生能力的移植物。 物理和化学刺激可以增强神经再生反应，因此，结合了这些 工程化移植物的模式可能会解决目前的一些治疗局限性。电刺激(ES)可以 促进神经传导、神经营养素释放和神经挤压伤的功能恢复，但这些 大差距PNI的福利尚未确定。4-氨基吡啶(4-AP；a)的化学刺激 钾通道阻滞剂)对神经元的影响似乎与ES相似，并能促进挤压的PNI修复， 但可能会与ES协同行动。实施这些物理和化学线索以实现有效的大缺口PNI 修复将需要外科手术插入具有适当机械强度的导电支架， 降解性、导电性和孔隙特性。该提案旨在通过NOVICE、 可生物降解的离子导电(IC)壳聚糖支架和混合工程异体神经移植修复大面积 缝隙神经缺陷。含4-AP的生物工程IC支架可促进神经营养因子的体外释放和增强 大间隙PNI体内髓鞘形成早期修复。初步研究表明，联合应用 4-AP和ES减少了皮下植入支架周围的纤维包膜厚度，并增加了 神经营养素的体外表达与4-AP或单独ES的比较。这表明将4-AP和ES相结合可以提高 功能性、生物兼容性和积极的免疫反应。因此，我们假设IC支架 结合化学和电信号将调节细胞与材料的相互作用，以促进轴突再生 功能恢复率和功能恢复与自体移植相当。这将在三个具体目标中进行测试：1)开发和 4-AP释放率、传导性和生物降解性变化的IC支架的特征；2)评估人类 和大鼠雪旺细胞对含有4-AP和/或ES的IC支架的体外反应，以模拟体内反应和 4-AP/-ES的工程支架和同种异体移植物的安全性和有效性。 严重的坐骨神经缺损症。大间隙PNI的生物活性电化修复 暗示将对该领域产生广泛影响。这些研究将弥合复杂的ES之间的知识鸿沟- 介导的细胞-材料相互作用的微环境，以及对潜在的再生途径研究较少。 这些发现可能会改进神经缺陷的治疗，并为再生的探索性工作提供参考。 其他肌肉骨骼组织的神经支配策略。

Project Summary/Abstract Peripheral nerve injuries (PNI) affect millions of people in the US, and PNI with large gaps require surgical repair. Although biological and synthetic grafts are widely used to repair PNI with large gaps, they both can suffer from suboptimal clinical outcomes. Autografts are the gold standard treatment but are limited by availability and defect repair size, while synthetic grafts have poor biodegradability, strength, bioactivity, and functionality. Thus, the long-term objective of this proposal is to engineer grafts with enhanced large-gap nerve regeneration capabilities. Physical and chemical stimulation can enhance nerve regeneration responses, thus, incorporating these modalities into engineered grafts may address some current treatment limitations. Electrical stimulation (ES) can enhance nerve conduction, neurotrophin release, and functional recovery of nerve crush injuries, but these benefits have not been established for large-gap PNI. Chemical stimulation using 4-aminopyridine (4-AP; a potassium channel blocker) appears similar to ES in its effects on neurons and can enhance crush PNI repair, yet may act synergistically with ES. Implementing these physical and chemical cues for effective large-gap PNI repair will require surgical insertion of an electrically conductive scaffold with appropriate mechanical strength, degradation, conductivity, and pore properties. This proposal aims to deliver 4-AP and ES via novel, biodegradable, ionically conducting (IC) chitosan scaffolds and hybrid engineered nerve allografts to repair large- gap nerve defects. Bioengineered IC scaffolds with 4-AP can increase neurotrophin release in vitro and enhance myelination of large-gap PNI in vivo in early-stage repair. Preliminary studies revealed that combined application of 4-AP and ES reduced fiber capsule thickness around subcutaneously implanted scaffolds and increased in vitro neurotrophin expression compared to 4-AP or ES alone. This suggests combining 4-AP and ES improves functionality, biocompatibility, and positive immune responses. Therefore, it was hypothesized that IC scaffolds combined with chemical and electrical cues will modulate cell-material interactions to enhance axon regeneration rate and functional recovery comparable to autografts. This will be tested in three Specific Aims: 1) Develop and characterize IC scaffolds with variations in 4-AP release rate, conductivity, and biodegradation; 2) Assess human and rat Schwann cell responses to IC scaffolds with 4-AP and/or ES in vitro to model in vivo responses and future interventions; and 3) Test safety and efficacy of engineered scaffolds and allografts with 4-AP +/- ES in a critical-sized sciatic nerve defect. Engineered repair of large-gap PNI using bioactive electrical and chemical cues will broadly impact the field. These studies will bridge the knowledge gap between the complex ES- mediated cell-material interaction microenvironment and poorly studied underlying regeneration pathways. These findings may improve the treatment of nerve defects, and inform exploratory work on regenerative strategies for innervation in other musculoskeletal tissues.