DYNAMICS OF FLOW-DEPENDENT ARTERIAL PERMEABILITY

本研究的总体目标是了解影响大分子经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解。对大分子转运的兴趣是由于它在动脉硬化的发生和发展中的重要性。由于动脉粥样硬化病变的分布表明血液动力学因素可能与疾病的局部化有关，因此血液动力学因子对动脉摄取的调节作用尤其令人感兴趣；此外，有证据表明，血流动力学应力可以影响内皮细胞的通透性。本研究的一个主要假设是，在流量变化引起的通透性增加期间，跨内皮通量的重要部分发生；因此，特别强调的是内皮细胞的屏障功能对血流动力学环境变化的动态响应。研究目标是通过动物实验，计算机模拟和细胞和分子生物学的独特组合来解决。在基线或干预后，猪永久髂动脉中白蛋白通透性的空间变化，将使用埃文斯蓝染料的照相密度测定法来测量白蛋白摄取。血流的改变可以通过可逆的、可调节的股动静脉分流术来实现。髂血管壁剪切应力的分布，以及由操纵分流引起的应力变化，将从动脉和近端血管注射模的区域的流体动力学计算中得到；白蛋白摄取对血流动力学应激和应激变化的依赖性将被评估和建模。在一组单独的动物中，不会注射铸造材料，来自感兴趣区域的组织将被固定或外植和培养，并且将使用各种技术来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介导细胞氧化还原状态、细胞骨架的完整性、与邻近细胞的连接以及与基质的粘附的特性。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响应也将被检查，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.