Mechanotransduction in Neointimal Hyperplasia Formation in Arteriovenous Grafts

描述（由申请方提供）：新生内膜增生（NH）导致的移植物-静脉吻合处狭窄是血液透析用动静脉移植物（AVG）失败的主要原因。目前，没有临床治疗方法可以显著预防或治疗原发性AVG NH。动脉血流直接分流到静脉中极大地改变了静脉中的血液动力学。因此，流体剪切应力（FSS）和壁周向应力（WCS）在NH敏感部位的AVG显着改变。我们认为这些血流动力学变化是AVG静脉吻合处NH发展的主要因素。本项目旨在了解AVG中NH发展的血流动力学调节。AVG设置中的详细FSS和WCS尚未完全理解。我们将使用最先进的基于图像的计算力学来表征这些应力，并将这些数据应用于设计实验来描绘机械转导途径。我们将重点关注i）两种受体酪氨酸激酶（RTK），血管内皮生长因子受体（VEGFR）和血小板衍生生长因子受体（PDGFR）作为NH发病机制中的主要机械传感器的作用;和ii）转录因子E26 -1（Ets-1）作为RTK激活的主要效应子，导致NH形成的作用。我们的建议是基于我们的初步发现，i）VEGFR，PDGFR和Ets-1在猪AVG模型的NH敏感位点上调; ii）RTK抑制剂舒尼替尼抑制Ets-1表达 和NH发展; iii）在颈动脉球囊损伤的大鼠模型和天然动静脉瘘的小鼠模型中，通过Ets-1抑制减少NH形成。我们的假设如下：i）RTK和Ets-1的激活是通过分别由于AVG近吻合静脉段血流量增加和管壁扩张而导致的FSS和WCS增加而启动的。ii）VEGFR和PDGFR分别是血管内皮细胞和平滑肌细胞中的主要机械传感器，其介导FSS和WCS对Ets-1的激活。iii）RTK激活后Ets-1激活是AVG中NH形成的关键事件。有三个具体目标：i）理解猪模型中AVG的NH敏感位点和NH抗性位点之间的机械环境差异。ii）在灌注静脉培养模型中确定增加的FSS或WCS是否增强RTK和Ets-1活化以及随后的NH形成。iii）探索RTK和Ets-1是否介导猪AVG模型中的NH形成。RTK和Ets-1依赖的机械转导途径和探索这些途径在NH形成中的作用是新的。该结果具有广泛应用于其他血管病理条件下，其中有改变的血流，包括动静脉瘘的潜力。灌注器官培养系统可用于研究相关流动条件下的药物治疗。

DESCRIPTION (provided by applicant): Stenosis at the graft-vein anastomosis due to neointimal hyperplasia (NH) is the predominant cause of failure of arteriovenous grafts (AVGs) used for hemodialysis. Currently, there are no clinical therapies that significantly prevent or tret primary AVG NH. Shunting of arterial blood flow directly into the vein greatly alters the hemodynamics in the vein. Consequently, the fluid shear stress (FSS) and wall circumferential stress (WCS) at the NH-susceptible sites of AVGs are markedly altered. We propose that these hemodynamic changes are major contributors to NH development at the venous anastomosis of AVGs. This project aims to understand the hemodynamic regulation of NH development in AVGs. Detailed FSS and WCS in the AVG setting are not yet fully understood. We will use state-of-the-art image-based computational mechanics to characterize these stresses, and apply these data to design experiments to delineate mechanotransduction pathways. We will focus on i) the roles of two receptor tyrosine kinases (RTKs), vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR), as major mechanosensors in the pathogenesis of NH; and ii) the role of the transcription factor E twenty-six-1 (Ets-1) as the primary effector activated by RTK, leading to NH formation. Our proposal is based on our preliminary findings that i) VEGFR, PDGFR and Ets-1 are up-regulated in NH-susceptible sites in a porcine AVG model; ii) the RTK inhibitor sunitinib inhibits Ets-1 expression and NH development in a perfused vein organ culture model; iii) NH formation is reduced by Ets-1 inhibition in a rat model of carotid artery balloon injury and a mouse model of native arteriovenous fistula. Our hypotheses are as follows: i) The activation of RTK and Ets-1 is initiated by increases in FSS and WCS, as a result of increased blood flow and wall distention respectively, at the juxta-anastomotic vein segment of the AVG. ii) VEGFR and PDGFR are the primary mechanosensors in vascular endothelial cells and smooth muscle cells, respectively, that mediate Ets-1 activation by FSS and WCS. iii) RTK activation followed by Ets-1 activation is a critical event in NH formation in the AVG. There are three Specific Aims: i) Understand differences in the mechanical environment between the NH- susceptible and NH-resistant sites of AVG in a porcine model. ii) Determine in a perfused vein culture model whether increased FSS or WCS enhances RTK and Ets-1 activation and subsequently NH formation. iii) Explore whether RTK and Ets-1 mediate NH formation in a porcine AVG model. Delineation of the RTK- and Ets-1-dependent mechanotransduction pathways and exploration of the roles of these pathways in NH formation is novel. The results have the potential for broad applications in other vascular pathological conditions where there is altered blood flow, including AV fistulas. The perfused organ culture system can be used to investigate pharmacological therapies under relevant flow conditions.