Hemodynamics, Uremia & Vascular Biology: Interactive Pathways for AVF Maturation

描述（由申请人提供）： 虽然动静脉瘘（AVF）被广泛认为是最好的透析血管通路形式，但目前存在非常严重的成熟失败问题，即无法实现足够的静脉扩张和流动以支持透析。在放射学水平上，AVF成熟失败的特征是吻合口周围静脉段狭窄，而在组织学和病理学水平上，它是由于新生内膜增生的组合 以及缺乏外部重塑。在机械水平上，我们在当前资助期间进行的工作清楚地表明，不同的血流动力学特征导致非常不同的临床（流量和直径）和组织学终点。因此，我们认为血流动力学损伤是关键的上游事件，然后导致下游级联事件（血管生物学对损伤的反应）。然而，一个重要的未知因素仍然是尿毒症在该级联反应中的潜在影响，特别是在能够调节下游生物反应对上游血流动力学损伤的背景下。尿毒症可能是重要的原因是其特征在于氧化应激、炎症和内皮功能障碍的显著增加，所有这些都是对血流动力学损伤的下游生物反应的关键参与者。此外，我们和其他人已经能够证明在建立透析血管通路时（甚至在暴露于血流动力学变化之前）采集的静脉组织样本中存在新生内膜增生，这表明尿毒症本身（与炎症、氧化应激和内皮功能障碍相关）可能是静脉狭窄/重塑的重要独立风险因素。因此，当前提案的中心假设是AVF成熟是两种主要机制途径（上游血流动力学损伤和尿毒症影响下游血管生物学）之间广泛相互作用的最终结果。换句话说，我们想探索尿毒症的存在或不存在如何调节血液动力学损伤的生物反应。我们计划通过三个具体目标来解决这个中心假设。在具体目标1中，我们将扩展以下假设：不同的血流动力学剪切应力曲线（弯曲与直AVF）启动了一系列不同的生物学（基因表达和细胞表型）曲线，然后导致不同的形态测量（壁厚）和临床（流量和直径）终点。该特定目标还将为特定目标2中的研究提供历史同期比较。在具体目标2中，我们将通过详细比较具体目标1中描述的尿毒症猪模型与对照动物（来自具体目标1）的生物学、形态学和临床终点，阐述尿毒症本身可以影响/调节对血流动力学损伤的生物学反应的假设。最后，在具体目标3中，我们将联合收割机结合下一代测序技术（RNA Seq.分析）与我们独特的尿毒症动物模型，以展望未来，关于新的基因，途径和机制的识别。这些信息可用于识别AVF成熟的新预测标志物，或者作为开发未来生物学相关疗法的知识基础，以预防或治疗AVF成熟失败。总之，我们认为该提案是重要的，因为它关注的是一个重要的临床问题，目前还没有有效的治疗方法;它的独特之处在于它解决了尿毒症本身作为AVF成熟调节剂的复杂问题，最后它是创新的，因为它将先进的测序技术和生物信息学与临床相关的尿毒症模型联系起来。

DESCRIPTION (provided by applicant): Although arteriovenous fistulae (AVFs) are widely considered to be the best form of dialysis vascular access they currently have very significant problems with maturation failure, which is an inability to achieve adequate venous dilatation and flow to support dialysis. At a radiological level AVF maturation failure is characterized by a perianastomotic venous segment stenosis, while at a histological and pathogenetic level it is due to a combination of neointimal hyperplasia and an absence of outward remodeling. At a mechanistic level, work performed by us during the current grant period has clearly demonstrated that differing hemodynamic profiles result in very different clinical (flow and diameter) and histological end points. We therefore believe that hemodynamic injury is the critical upstream event, which then results in a downstream cascade of events (the vascular biology response to injury). An important unknown, however, remains the potential impact of uremia within this cascade, especially in the context of being able to modulate the downstream biological response to upstream hemodynamic injury. The reason that uremia is likely to be important is that it is characterized by significant increases in oxidaive stress, inflammation and endothelial dysfunction, all of which are key players in the downstream biological response to hemodynamic injury. In addition we, and others have been able to demonstrate the presence of neointimal hyperplasia within venous tissue samples taken at the time of dialysis vascular access creation (even before exposure to hemodynamic changes) suggesting that uremia per se (with its linkages to inflammation, oxidative stress and endothelial dysfunction), could be an important independent risk factor for venous stenosis/remodeling. The central hypothesis of the current proposal therefore is that AVF maturation is the end result of interactions between a wide spectrum of two prominent mechanistic pathways (upstream hemodynamic injury and uremia influenced downstream vascular biology). Put another way we want to explore how the presence or absence of uremia modulates the biological response to hemodynamic injury. We plan to address this central hypothesis through three Specific Aims. In Specific Aim 1, we will expand on the hypothesis that differential hemodynamic shear stress profiles (curved versus straight AVFs) initiate a sequence of differential biological (gene expression and cellular phenotyping) profiles, which then result in different morphometric (wall thickness) and clinical (flow and diameter) end points. This Specific Aim will also provide a historically concurrent comparator for the studies in Specific Aim 2. In Specific Aim 2, we will address the hypothesis that uremia per se can influence/modulate the biological response to hemodynamic injury, through a detailed comparison of the biological, morphometric and clinical end points described in Specific Aim 1 in the setting of a uremic pig model as compared to control animals (from Specific Aim 1). Finally in Specific Aim 3, we will combine the power of next generation sequencing technology (RNA Seq. analyses) with our unique animal model of uremia in order to look to the future, with regard to the identification of novel genes, pathways and mechanisms. This information could then be used to identify novel predictive markers for AVF maturation, or alternatively, as a knowledge base for the development of future biologically relevant therapies to prevent or treat AVF maturation failure. In summary, we believe that this proposal is significant because it focuses on an important clinical problem for which there are currently no effective therapies; it is unique in that it addresses head on the complex issue of uremia per se as a modulator of AVF maturation, and finally it is innovative in that it links advanced sequencing technology and bioinformatics to a clinically relevant uremic model.