Molecular regulation of vein graft adaptation

描述(申请人提供)：几种常见的人类疾病治疗方法的基础是外科手术使用静脉作为动脉管道。自体静脉搭桥通常用于晚期心血管和外周血管疾病；类似地，外科医生也进行动静脉瘘(AVF)，这是血液透析的首选途径。静脉移植物和动静脉瘘的通畅性差，需要额外的重做手术和手术，这反映了我们对导致静脉成功适应动脉环境的静脉重塑生物学的不完全理解。这一知识缺口创造了对增强静脉适应、成熟度和静脉导管的成功长期使用的新方法的未得到满足的医学需求。酪氨酸激酶受体Eph-B4是静脉的胚胎决定因素。在人类和小鼠的静脉移植物中，Eph-B4的表达降低与静脉移植物的适应有关，而Eph-B4活性的降低对于成年小鼠静脉移植物的静脉适应至关重要。我们提供了令人振奋的新数据：1)我们的创新的AVF小鼠模型忠实地概括了人类AVF的成熟过程，包括一个未能成熟的子集；2)在人和小鼠中，AVF适应动脉环境期间Eph-B4的表达增加，而不同于在静脉移植适应期间Eph-B4表达降低；3)Eph-B4功能对于AVF适应是必不可少的；4)Eph-B4酪氨酸-774是Eph-B4磷酸化和下游信号传递的关键位点。我们假设移植静脉的适应性导致血管同一性的丧失，而动静脉动静脉同一性的成熟导致动-静脉同一性的融合。我们的数据还提示了一种机制，例如，Eph-B4是一种先前未被认识的但关键的血管内皮细胞转导因子，可将血流动力学负荷传递到静脉。我们假设，静脉移植物和动静脉瘘血流动力学环境的不同对Eph-B4酪氨酸-774的磷酸化和/或Eph-B4的表达有不同的调节作用。我们将使用体外和体内模型的组合，使用可以单独控制大小血管和内皮单层上的单独血流动力学负荷的生物反应器，以及使用静脉移植物和AVF的体内模型来验证我们的假设，具体目的如下：目的I：确定血流动力学负荷如何差异调节Eph-B4在整个血管中的磷酸化和功能，包括对成功和失败的AVF的分析。目的II：确定不同程度的切应力如何调节内皮细胞中Eph-B4的磷酸化和功能。目的III：研究Eph-B4酪氨酸-774磷酸化对静脉内皮细胞功能的调节作用。这项提案中的工作将建立我们的创新 和改变范式的假设，即Eph-B4是对血管的机械载荷的新的和关键的换能器，并且Eph-B4对不同类型的载荷有不同的响应， 即使在没有伊夫林-B2的情况下。Eph-B4的活性或缺乏决定了血管的表型及其功能。在静脉移植适应和AVF成熟过程中，血管识别的异常调节可以被用来改进人类的临床治疗。

DESCRIPTION (provided by applicant): A cornerstone of several common therapies for human diseases is the surgical use of a vein as an arterial conduit. Autologous vein bypass grafts are commonly performed for advanced cardiovascular and peripheral vascular disease; similarly, surgeons also perform arteriovenous fistulae (AVF), the preferred access for hemodialysis. The poor patency of both vein grafts and AVF, requiring additional re-do procedures and surgery, reflects our imperfect understanding of the biology of venous remodeling that leads to successful venous adaptation to the arterial environment. This knowledge gap creates an unmet medical need for novel approaches to enhance venous adaptation, maturation, and successful long-term use of venous conduits. The tyrosine kinase receptor Eph-B4 is an embryonic determinant of veins. Diminished Eph-B4 expression is associated with vein graft adaptation in humans and mice, and reduced Eph-B4 activity is essential for venous adaptation in adult mouse vein grafts. We present exciting new data that: 1) our innovative mouse model of AVF faithfully recapitulates human AVF maturation, including a subset that fail to mature; 2) in both humans and mice, Eph-B4 expression increases during AVF adaptation to the arterial environment, unlike the decreased Eph-B4 expression during vein graft adaptation; 3) Eph-B4 function is essential for AVF adaptation; and 4) Eph-B4 tyrosine-774 is a critical site of Eph-B4 phosphorylation and downstream signaling. We hypothesize that vein graft adaptation leads to loss of vessel identity and AVF maturation leads to merged arterial-venous identity. Our data also suggest a mechanism, e.g. that Eph-B4 is a previously unrecognized but critical endothelial transducer of hemodynamic loads to veins. We hypothesize that differences in the hemodynamic environments of vein grafts and AVF differentially regulate Eph-B4 tyrosine-774 phosphorylation and/or Eph-B4 expression. We will use a combination of in vitro and in vivo models, using a bioreactor that can individually control separate hemodynamic loads on both large and small vessels and endothelial monolayers, as well as using in vivo models of vein grafts and AVF, to test our hypothesis with the following specific aims: Aim I: Determine how hemodynamic loads differentially regulate Eph-B4 phosphorylation and function in whole vessels, including analysis of successful and failed AVF. Aim II: Determine how different magnitudes of shear stress regulate Eph-B4 phosphorylation and function in endothelial cells. Aim III: Determine how Eph-B4 tyrosine-774 phosphorylation regulates venous endothelial cell function. The work in this proposal will establish our innovative and paradigm-changing hypothesis that Eph-B4 is a novel and critical transducer of mechanical loads to the blood vessel and that Eph-B4 is differentially responsive to different types of loads, even in the absence of Ephrin-B2. Eph-B4 activity or lack thereof, defines the phenotype of the blood vessel and its function. Abnormal regulation of vessel identity during vein graft adaptation and AVF maturation can be manipulated to improve human clinical therapies.