Molecular regulation of fistula adaptation for dialysis access

终末期肾病（ESRD）扰乱了美国50多万人的生活， 每年新发病例超过10万例，死亡率约为8.8万人 年退伍军人事务部照顾大约3万名患有ESRD的退伍军人。治疗终末期肾病的费用， 2008年约390亿美元，继续增长。肾脏替代手术最常见的选择 治疗是血液透析;血液透析的通路通过动静脉瘘（AVF）进行， 动静脉移植物（AVG）或临时导管放置。虽然瘘管需要时间来“成熟”，例如。 在开始透析之前，扩张、扩张和增加流量，AVF仍然是首选的接入模式， 与AVG和导管入路相比，具有上级长期结果。尽管AVF入路具有优越性， 与其替代品相比，AVF还远远不够完美。AVF在约20-50%的 病例，其中许多AVF需要一些治疗干预才能成功成熟。其实这些 较差的临床结果表明，AVF违反了血管外科的所有规则;尽管它们是理想的 AVF具有长度短、直径大、流量大、径流阻力小的特点， 血管外科医生进行的任何手术的通畅性。AVF的通畅性差清楚地反映了我们的 对导致AVF成熟的静脉重塑生物学的不完全理解和未满足的医疗要求， 需要新的方法来促进AVF成熟和随后的瘘管使用。 Ephrin-Eph途径的几个成员最近被描述为发育性的， 血管特性的特定关键决定因素，Ephrin-B2配体是动脉的胚胎决定因素 Eph-B4受体是静脉的胚胎决定因子。然而，目前还没有确定是否Eph- B4在成人静脉中起作用，以及Ephrin-Eph通路是否在AVF中起机制作用 适应动脉环境。 我们假设Eph-B4表达和/或活化的增加（通过磷酸化评估） 在正常AVF成熟过程中介导AVF壁直径增加和增厚。这是一个不同 Eph-B4介导静脉移植物适应的机制。我们将以这些目标来检验我们的假设： 目的I：确定Eph-B4是否介导在血管扩张期间的直径扩张和/或壁增厚。 AVF成熟正常。我们的假设，基于我们的初步数据，是增加的表达和/或 静脉特异性基因Eph-B4的激活导致正常的AVF直径扩张和壁 增厚和瘘管成熟。我们将检查手术标本来自专利人类AVF 接受手术翻修或结扎，以确定AVF直径和/或壁厚与 Eph-B4表达和活化。我们将通过直接增加和减少Eph-B4来测试这一假设 在我们的小鼠AVF模型中的信号传导，并将血管特性与AVF直径和壁厚度相关联。 目的二：研究切应力对Eph-B4磷酸化和表达的影响。我们 假设剪切应力通过刺激Eph-B4信号传导和表达促进AVF成熟， 内皮细胞;以这种方式，剪切应力的变化导致AVF扩张和壁增厚。我们将测试这个 假设通过改变我们的体外流动模型中的剪切应力，使用全静脉和内皮细胞流动 模型，并显示动脉剪切应力的大小刺激Eph-B4磷酸化和表达。 目的III：确定Eph-B4信号传导如何调节血管细胞功能。我们的假设是伊弗- 酪氨酸-774上的B4磷酸化是血管细胞中Eph-B4下游功能的关键调节剂。我们 将通过检查野生型和突变型Eph-B4对内皮细胞的不同作用来检验这一假设。 平滑肌细胞信号转导以及细胞增殖和迁移。

End-stage renal disease (ESRD) upsets the lives of over half a million people in the United States, with an incidence of over 100,000 new cases per year and a mortality rate of approximately 88,000 people each year. The Veteran's Affairs cares for approximately 30,000 veterans with ESRD. The costs to treat ESRD, approximately $39 billion in 2008, continue to grow. The most common option chosen for renal replacement therapy is hemodialysis; access for hemodialysis is performed by either arteriovenous fistula (AVF), arteriovenous graft (AVG), or temporary catheter placement. Although fistulae take time to "mature," e.g. dilate, thicken and increase flow, prior to beginning dialysis, AVF continue to be the preferred mode of access, with superior long term results compared to AVG and catheter access. Despite the superiority of AVF access compared to its alternatives, AVF are still far from perfect. AVF fail to mature in approximately 20-50% of cases, with many of these AVF requiring some therapeutic intervention to mature successfully. In fact, these poor clinical results demonstrate that AVF defy all the rules of vascular surgery; despite their desirable characteristics of short length, large diameter, high flow, and low resistance runoff, AVF exhibit the worst patency of any procedure performed by vascular surgeons. The poor patency of AVF clearly reflects our imperfect understanding of the biology of venous remodeling leading to AVF maturation and the unmet medical need for novel approaches to enhance AVF maturation and subsequent fistula usage. Several members of the Ephrin-Eph pathway have recently been described as developmentally specified critical determinants of vessel identity, with Ephrin-B2 ligand an embryonic determinant of arteries and Eph-B4 receptor an embryonic determinant of veins. However, it is currently not established whether Eph- B4 is functional in adult veins, and whether the Ephrin-Eph pathway plays a mechanistic role during AVF adaptation to the arterial environment. We hypothesize that increased Eph-B4 expression and/or activation (as assessed by phosphorylation) mediates increased AVF wall diameter and thickening during normal AVF maturation. This is a different mechanism than by which Eph-B4 mediates vein graft adaptation. We will test our hypothesis with these aims: Aim I: To determine whether Eph-B4 mediates diameter expansion and/or wall thickening during normal AVF maturation. Our hypothesis, based on our preliminary data, is that increased expression and/or activation of the venous specification gene Eph-B4 leads to normal AVF diameter expansion and wall thickening and fistula maturation. We will examine surgical specimens derived from patent human AVF undergoing surgical revision or ligation to determine how AVF diameter and/or wall thickness correlate with Eph-B4 expression and activation. We will test this hypothesis by directly increasing and decreasing Eph-B4 signaling in our mouse AVF model and correlating vessel identity with AVF diameter and wall thickness. Aim II: To determine how shear stress regulates Eph-B4 phosphorylation and expression. Our hypothesis is that shear stress promotes AVF maturation by stimulating Eph-B4 signaling and expression in endothelial cells; in this way, changes in shear stress lead to AVF dilation and wall thickening. We will test this hypothesis by altering shear stress in our in vitro flow models, using both whole vein and endothelial cell flow models, and show that arterial magnitudes of shear stress stimulate Eph-B4 phosphorylation and expression. Aim III: To determine how Eph-B4 signaling regulates vascular cell function. Our hypothesis is that Eph- B4 phosphorylation on tyrosine-774 is a critical regulator of Eph-B4 downstream function in vascular cells. We will test this hypothesis by examining the differential effects of wild type and mutated Eph-B4 on endothelial and smooth muscle cell signal transduction as well as cell proliferation and migration.