A Rational Approach to Stimulating Peripheral Nerve Regeneration Across Criticall

严重的创伤和肿瘤切除等手术通常会造成周围神经间隙， 美国每年有超过25万人受伤修复的临床“金标准”是自体移植， 40~50%的患者恢复有用功能。自体移植物的有效性和使用受到以下因素的限制： 问题包括有限的可用性和供体部位的附带损害。因此， 替代的生物工程方法，匹配或超过自体移植物的性能。我们最近报道了一个 使用基于薄膜的管腔内桥接大鼠中临界尺寸神经间隙（e15 mm）的突破 在标准神经引导通道中携带的支架。这一发现引出了两个重要问题。（一） 最小的基于薄膜的线索（仅占管腔内的0.3%）的管腔内呈现是如何 体积）对再生有显著影响？(2)如果我们理解了这种效应背后的机制， 我们能否影响这个过程，进一步增强再生，以达到或超过自体移植的性能？ 了解聚合物纤维为基础的地形之间的机械相互作用（可以称为 内源性“再生过程/序列”）对于合理设计管腔内 脚手架这一过程自发地发生在短间隙（大鼠<10 mm）的成功桥接过程中，但 在较长的间隙（大鼠中为15 mm）的桥接中未能发生。它涉及纤维蛋白电缆的形成，细胞外 基质沉积/重塑（例如，纤维连接蛋白）、神经胶质/支持细胞（成纤维细胞和雪旺细胞）和轴突 渗透到差距中。我们的中心假设是，具有形貌的薄膜 提示增强再生是通过充当施旺细胞浸润的物理“组织模板”， 雪旺细胞定向、细胞外基质沉积/组织化和轴突浸润，这反过来又影响了细胞的生长。 导致成功的再生。我们的具体目标如下： 目的1：研究聚合物纤维基薄膜形貌与纤维蛋白电缆/ECM之间的相互作用 组织和胶质细胞迁移在体内修复临界尺寸的神经间隙。 目的2：确定影响再生的可扩散生化因子的局部递送的效果。 序列，以协同增强再生时，结合地形线索。 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/伤口愈合序列和呈现形貌的腔内薄膜支架 线索除了这个调节再生序列的物理模板之外，我们进一步提出， 它是一种持续局部递送神经营养素-3的“生化增强”[目的2]。因此，我们提出一个 通过合理设计最低限度的、基于腔内膜的支架， 应该a）增强我们对腔内支架设计理解和B）导致显著更好的 在桥接临界尺寸的神经间隙方面，比以前从神经引导通道可获得的性能更好。

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.