DYNAMICS OF FLOW-DEPENDENT ARTERIAL PERMEABILITY

这项研究的总体目标是了解影响大分子通过内皮进入动脉壁的因素，特别是局部血流动力学对这一过程的调节作用。大分子转运在动脉粥样硬化的发生和发展中的重要性引起了人们对它的兴趣。血流动力学因素对动脉摄取的调节尤为重要，因为动脉粥样硬化病变的分布表明血流动力学因素可能参与了疾病的定位；此外，有证据表明血液动力学应激可以影响内皮通透性。这项研究的一个基本假设是，在血流变化引起的通透性增加过程中，跨内皮细胞流量的一个重要部分发生；因此，特别强调内皮细胞衬里的屏障功能对血流动力学环境变化的动态响应。研究目标通过动物实验、计算机模拟以及细胞和分子生物学的独特组合来实现。无论是在基线还是在改变血流的干预措施之后，将使用Evans Blue染料的摄影密度测量法来测量白蛋白摄取，从而获得猪永久髂动脉白蛋白通透性的空间变化。血流的改变将由可逆的、可调整的股动静脉分流术产生。壁切应力的分布，以及分流引起的应力变化，将通过动脉和近端血管注射模型区域的验证流体动力学计算来获得；白蛋白摄取与血流动力学应力的关系将被评估和模拟。在另一组动物中，不会注射铸型材料，而是固定或移植并培养感兴趣区域的组织，并将使用各种技术将渗透性的变化与细胞特性联系起来。特别令人感兴趣的是调节细胞的氧化还原状态、细胞骨架的完整性及其与相邻细胞的连接和与底物的黏附的性质。高胆固醇血症对血管通透性的影响及其对血流变化的动态反应也将被检测，以确定高脂水平是否可能影响血流变化对血管摄取的影响。

The overall objective of this research is to understand the factors affecting the transendothelial entry of macromolecules into the arterial wall, and particularly the mediation of this process by local hemodynamics. The interest in macromolecular transport is prompted by its importance in the genesis and development of artherosclerosis. The mediation of arterial uptake by hemodynamic factors is of particular interest because the distribution of atherosclerotic lesions suggests that hemodynamic factors may be involved in the localization of the disease; furthermore, there is evidence that hemodynamic stress can influence endothelial permeability. A primary hypothesis of this research is that an important fraction of the transendothelial flux occurs during increases in permeability prompted by changes in flow; accordingly, particular emphasis is placed on the dynamic response of the barrier function of the endothelial lining to changes in the hemodynamic environment. The research objectives are addressed through a unique combination of animal experiments, computer simulation and cell and molecular biology. The spatial variation of the albumin permeability in the eternal iliac arteries of swine, either at baseline or subsequent to interventions that alter flow, will be obtained using photographic densitometry of Evans Blue dye to measure albumin uptake. The alterations in flow will be produced by reversible, adjustable femoral arteriovenous shunts. The distribution of wall shear stress, and of the changes in stress caused by manipulating the shunt, in the iliac vessels will be obtained from validated fluid dynamic computations in regions derived from injection casts of the arteries and the proximal vasculature; the dependence of albumin uptake on hemodynamic stress, and alterations in stress, will be assessed and modeled. In a separate set of animals, casting material will not be injected, and tissue from the region of interested will be fixed or explanted and cultured, and a variety of techniques will be used to relate the variations in permeability to cellular properties. Of particular interest are properties that mediate the redox state of the cell, the integrity of the cytoskeleton, and its junctions with neighboring cells and adhesion to the substratum. The effects of hypercholesterolemia on vascular permeability and its dynamic response to changes in flow will be examined as well, to determine whether high lipid levels potential the effects of flow changes on vascular uptake.