A Rational Approach to Stimulating Peripheral Nerve Regeneration Across Criticall

描述(申请人提供)：严重的创伤和外科手术，如肿瘤切除，经常造成周围神经间隙，在美国每年有超过25万人受伤。临床修复的“金标准”是自体移植，有40%~50%的患者恢复了有用的功能。自体移植的有效性和使用受到捐赠地点可获得性有限和附带损害等问题的限制。因此，开发与自体移植物性能相当或超过自体移植物性能的替代生物工程方法至关重要。我们最近报道了使用标准神经引导通道中携带的基于薄膜的腔内支架在大鼠身上桥接临界尺寸的神经气体(=15 mm)方面的突破。这一发现引出了两个重要问题。(1)管腔内呈现最小的基于薄膜的信号(仅占管腔内体积的0.3%)如何对再生产生显著影响？(2)如果我们了解了这种影响的机制，我们是否可以影响这一过程，并进一步增强再生以匹配或超过自体移植的性能？对于腔内支架的合理设计，有必要了解基于聚合物纤维的表面形貌(可称为内源性“再生过程/序列”)之间的机理相互作用。这一过程自发地发生在成功桥接短间隙(大鼠为10 mm)时，而不发生在桥接较长间隙(大鼠为15 mm)时。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)、胶质/支持细胞(成纤维细胞和雪旺细胞)以及轴突向间隙的渗透。我们的中心假设是，具有地形线索的薄膜促进再生的机制是作为雪旺细胞渗透、雪旺细胞取向、细胞外基质沉积/组织和轴突渗透的物理‘组织模板’，这反过来又导致成功的再生。我们的具体目标如下：目的1：研究聚合物纤维薄膜的形态结构与纤维蛋白缆线/细胞外基质组织和胶质细胞在体内修复严重神经缺损区过程中的相互作用。目的2：确定局部传递影响再生序列的扩散生化因子的效果，以协同促进再生。这里的创新之处在于，我们将研究再生/伤口愈合序列的早期事件与呈现地形线索的腔内薄膜支架之间以前未被充分探索的相互作用。除了这个调节再生序列的物理模板外，我们还建议通过持续的局部递送神经营养素-3来给它一个‘生化促进’[目标2]。因此，我们通过合理设计最低限度的管腔内薄膜支架解决了一个重要的临床问题，这种支架应该a)增强我们对管腔内支架设计的理解，以及b)在弥合临界大小的神经间隙方面取得比以前神经引导通道显著更好的性能。 与公共健康相关：仅在美国，每年就有超过25万至30万人发生周围神经损伤。这项研究将促进我们对管腔内支架促进周围神经再生的机制的理解，并将开发可能改善周围神经损伤后临床结果的技术。

DESCRIPTION (provided by applicant): 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 gas (=15mm) 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 (=15mm in rats). It involves a fibrin cable formation, extracellular matrix deposition/remodeling (e.g., 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 physical 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 bridging critically sized nerve gaps. PUBLIC HEALTH RELEVANCE: Over 250,000-300,000 peripheral nerve injuries occur every year in the US alone. This research will advance our understanding of the mechanisms of peripheral nerve regeneration that is promoted by intra-luminal scaffolds, and will develop technologies that are likely to improve clinical outcomes after peripheral nerve injury.