Mechanotransduction in Neointimal Hyperplasia Formation in Arteriovenous Grafts

描述（由申请人提供）：由于新生内膜增生（NH）导致的移植物-静脉吻合口狭窄是用于血液透析的动静脉移植物（AVGs）失败的主要原因。目前，尚无临床治疗方法能有效预防或治疗原发性AVG NH。动脉血流直接分流到静脉，极大地改变了静脉的血流动力学。结果表明，氮敏感部位的流体剪切应力（FSS）和壁周向应力（WCS）发生了显著变化。我们认为这些血流动力学变化是AVGs静脉吻合处NH发展的主要因素。本项目旨在了解AVGs中NH发育的血流动力学调控。详细的FSS和WCS在AVG设置尚未完全了解。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以描绘机械转导途径。我们将重点关注i)两种受体酪氨酸激酶（RTKs），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；ii)转录因子E 26 -1 （Ets-1）作为RTK激活的主要效应因子，导致NH形成的作用。我们的建议是基于我们的初步发现：i)在猪AVG模型中，VEGFR、PDGFR和Ets-1在nhh易感位点上调；ii) RTK抑制剂舒尼替尼抑制Ets-1的表达

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.