A Rational Approach to Stimulating Peripheral Nerve Regeneration Across Criticall

严重的创伤和肿瘤切除等外科手术往往会造成周围神经缝隙， 每年在美国造成超过25万人受伤。临床上修复的“黄金标准”是自体移植， 有40~50%的患者恢复了有用的功能。自体移植物的有效性和使用受到以下限制 问题包括捐赠地的可获得性有限和附带损害。因此，大力发展生态文明建设至关重要。 符合或超过自体移植性能的替代生物工程方法。我们最近报道了一起 用薄膜管腔内桥接大鼠严重神经间隙(E15 Mm)的突破 支架安装在标准的神经引导通道中。这一发现引出了两个重要问题。(1) 如何在腔内呈现最小的基于薄膜的线索(仅占腔内的0.3% 体积)对再生有戏剧性的影响吗？(2)如果我们了解这种影响的机制， 我们能否影响这一过程，并进一步加强再生，以达到或超过自体移植的性能？ 了解基于聚合物纤维的表面形貌(可以称为 内源性的再生过程/序列)对于腔内的合理设计是必要的 脚手架。这一过程是在成功地桥接短间隙(大鼠为10 mm)时自发发生的，但 在较长间隙(大鼠为15 mm)的桥接中未发生。它涉及到纤维蛋白电缆的形成，细胞外 基质沉积/重塑(如纤维连接蛋白)、胶质/支持细胞(成纤维细胞和雪旺细胞)和轴突 渗入缝隙。我们的中心假设是薄膜与地形 提示通过充当雪旺细胞渗透的物理‘组织模板’来增强再生， 雪旺细胞定向、细胞外基质沉积/组织和轴突渗透，进而 才能成功再生。我们的具体目标如下： 目的1：研究基于聚合物纤维的薄膜形貌与纤维蛋白电缆/ECM的相互作用 在体内修复临界大小神经间隙过程中的组织和神经胶质细胞迁移。 目的2：确定局部注射影响再生的扩散生化因子的效果。 序列，当与地形线索结合时，协同增强再生。 这里的创新之处在于，我们将调查以前未被充分探索的早期事件之间的相互作用 再生/创面愈合序列和呈现地形的腔内薄膜支架 暗示。除了这个调节再生序列的物理模板外，我们还建议给出 这是一种持续的局部神经营养因子-3[目标2]的‘生化促进’。因此，我们提出了一个 通过合理设计最低限度的管腔内膜支架来解决重大的临床问题 应该a)加强我们对管腔内支架设计的理解，b)结果明显更好 在弥合临界大小的神经间隙方面，其性能优于以前通过神经引导通道所能达到的效果。

Severe traumatic injuries and surgical procedures like tumor resection often create peripheral nerve gaps, accounting for over 250,000 injuries in the US annually. The clinical "gold standard" for repair is autografts, with which 40~50% of patients regain useful function. The effectiveness and use of autografts is limited by issues including limited availability and collateral damage at the donor site. So, it is critical to develop alternative bioengineered approaches that match or exceed autograft performance. We recently reported a breakthrough in bridging critically sized nerve gaps (e15mm) in rats using a thin film-based intra-luminal scaffold carried in a standard nerve guidance channel. This finding gives rise to two important questions. (1) How does intra-luminal presentation of minimal thin film-based cues (occupying just 0.3% of intra-luminal volume) have a dramatic effect on regeneration? (2) If we understood the mechanism underlying this effect, could we influence the process, and further enhance regeneration to match or exceed autograft performance? An understanding of the mechanistic interplay between polymer fiber-based topography (what may be termed the endogenous 'regenerative processes/sequence') is necessary for the rational design of intra-luminal scaffolds. This process spontaneously occurs during the successful bridging of short gaps (< 10mm in rats), but fails to occur in the bridging of longer gaps (e15mm in rats). It involves a fibrin cable formation, extracellular matrix deposition/remodeling (eg., fibronectin), glial/support cell (fibroblasts and Schwann cells) and axonal infiltration into the gap. Our central hypothesis is that the mechanism by which thin films with topographical cues enhance regeneration is by serving as physical 'organizing templates' for Schwann cell infiltration, Schwann cell orientation, extra-cellular matrix deposition/organization, and axon infiltration, which in turn leads to successful regeneration. Our specific aims are as follows: Aim 1: Investigate the interplay between polymer fiber-based thin film topographyand fibrin cable/ECM organization and glial cell migration during repair of critically sized nerve gaps in vivo. Aim 2: Determine the effect of local delivery of diffusible biochemical factors that influence the regenerative sequence to synergistically enhance the regeneration when combined with topographical cues. The innovation here is that we will investigate the previously under-explored interplay between early events of the regenerative/wound healing sequence and intra-luminal thin-film scaffolds that present topographical cues. In addition to this phyiscal template that modulates the regenerative sequence, we further propose to give it a 'biochemical boost' with the sustained local delivery of neurotrophin-3 [Aim 2]. We therefore address a significant clinical problem through the rational design of minimalist, intra-luminal film-based scaffolds that should a) enhance our understanding of intra-luminal scaffold design and b) result in significantly better performance than previously attainable from nerve guidance channels in briding critically sized nerve gaps.