糖萼是位于内皮细胞顶膜的一层多糖蛋白复合结构，是血管壁的物理渗透屏障。糖萼具有阻止致动脉粥样性脂质——低密度脂蛋白（LDL）在血管壁沉积的作用，但机制不明。本项目拟采用LDL亲和柱层析结合蛋白质免疫印迹、高压冷冻电镜、免疫荧光及体外力学加载等方法，探究LDL是否与糖萼结合、LDL在糖萼层的渗透深度、糖萼与孔洞（leaky junctions）及LDL跨内膜输运的相关性。旨在验证申请人提出的科学猜想：糖萼在阻止LDL向血管壁沉积过程中可能扮演了双重角色：一方面，糖萼通过与LDL结合，将其捕捉、截留在糖萼层内部；另一方面，糖萼作为力感受器，在局部血流动力学环境下，抑制内皮细胞（EC）的增殖、凋亡，减少血管内膜表面供LDL通过的孔洞数量和面积，最终达到阻止LDL向血管壁沉积的目的。本项目的实施将为动脉粥样硬化的发病机理提供力学生物学依据，并为将糖萼作为血管潜在的防治靶点提供理论支持。

The endothelial glycocalyx is a fluffy surface layer mainly composed of glycosaminoglycans and its bearing core proteins, and also a physical barrier for molecular exchange. It has been demonstrated that the endothelial glycocalyx can inhibit the transport of atherogenic low density lipoproteins (LDL) across the endothelium. Howerver, the underlying mechanism is unclear. This project intends to investigate the binding effect between LDL and glycocalyx, the depth of LDL penetrated into the glycocalyx, and the correlationship between glycocalyx, leaky junctions, and LDL transendothelial transport by using LDL affinity column chromatography, SDS-PAGE, high pressure freezing/freezing substitution transmission electron microscopy, immunofluorescence, and in in vitro shear stress application techniques. The proposed project aims at testifying the following hypothesis: the endothelial glycocalyx may play dual roles in the process of LDL accumulation within the vascular wall. One hand, it may act as a physical barrier, bind with LDLs, control them, and inhibit the deeper infiltration of LDLs into the vascular wall. The other hand, it may act as a mechanosensor, inhibit the proliferation and apoptosis of endothelial cell (EC) in response to the local hemodynamic environment, thus reducing the number of leaky junctions for LDL transport across the endothelium. The proposed project can enrich our understanding of the mechanism of atherosclerosis initiation and provide evidence to view the glycocalyx as a novel target for vascular disease prevention and treatment.