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， 每年新增病例超过10万例，死亡率约为8.8万人 年。退伍军人事务部照顾大约30,000名患有ESRD的退伍军人。治疗终末期肾病的费用， 2008年约为390亿美元，继续增长。肾脏置换最常见的选择 治疗是血液透析；血液透析的通路通过动静脉瘘(AVF)， 动静脉移植(AVG)，或临时放置导管。虽然瘘管需要时间才能“成熟”，例如。 扩张、增厚和增加流量，在开始透析之前，动静脉动静脉瘘仍然是首选的通路模式， 与AVG和导管通路相比，具有更好的长期效果。尽管AVF接入具有优越性 与其替代品相比，AVF仍远未达到完美。AVF未成熟的比例约为20%-50% 2例，其中许多动静脉瘘需要一些治疗干预才能成功成熟。事实上，这些 糟糕的临床结果表明，动静脉瘘违反了血管外科的所有规则；尽管它们是可取的 长径短、直径大、流量大、阻力小的径流特性最差。 血管外科医生进行的任何手术的通畅性。AVF的糟糕通畅性清楚地反映了我们的 对导致动静脉瘘成熟的静脉重塑的生物学认识不足和医学上的未解决之处 需要新的方法来增强动静脉瘘的成熟度和随后的瘘管使用。 最近，几个EPhin-Eph途径的成员被描述为发育中的 血管识别的特定关键决定因素，其中EPhin-B2配体是动脉的胚胎决定因素 而Eph-B4受体是血管的胚胎决定因素。然而，目前还不能确定Eph是否- B4在成人静脉中是有功能的，以及EPhin-Eph通路在AVF中是否发挥机械作用 对动脉环境的适应。 我们假设Eph-B4表达和/或激活增加(通过磷酸化评估) 调节aVF管壁直径的增加和正常aVF成熟过程中的增厚。这是一种不同的 与Eph-B4介导静脉移植适应的机制不同。我们将用这些目标来检验我们的假设： 目的I：确定Eph-B4是否介导血管直径扩张和/或管壁增厚 AVF发育正常。根据我们的初步数据，我们的假设是，表达和/或 激活静脉规范基因Eph-B4可导致正常的AVF直径扩张和管壁 增厚，瘘管成熟。我们将检查从人类AVF专利中提取的手术标本 接受外科翻修或结扎以确定动静脉瘘直径和/或室壁厚度如何与 Eph-B4的表达和激活。我们将通过直接增加和降低Eph-B4来检验这一假设 在我们的小鼠AVF模型中传递信号，并将血管识别与AVF直径和壁厚相关联。 目的II：确定切应力如何调节Eph-B4的磷酸化和表达。我们的 假设切应力通过刺激Eph-B4信号转导和表达促进AVF成熟。 在这种情况下，切应力的变化会导致AVF扩张和壁厚。我们将对此进行测试 在我们的体外血流模型中，使用全静脉和内皮细胞血流改变剪应力的假说 模型，并显示动脉切应力的大小刺激Eph-B4的磷酸化和表达。 目的III：研究Eph-B4信号对血管细胞功能的调节作用。我们的假设是伊夫- 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因子。我们 我将通过检测野生型和突变的Eph-B4对内皮细胞的不同影响来检验这一假说 以及平滑肌细胞的信号转导以及细胞的增殖和迁移。

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.