Fluid Mechanical Study on the Effect of Endothelial Surface Glycocalyx on the Cell Function

血管内皮细胞的管腔表面被称为糖萼的一层大分子覆盖。最近的实验证据表明，糖萼影响血管功能的几个方面。在本研究中，我们已经研究了内皮细胞表面糖萼的生理作用，从流体力学的观点。我们首先考虑溶质穿过微血管壁的运输。基于最近的详细测量的表面糖萼的超微结构，我们开发了一个数学模型的糖萼，并估计作为溶质大小的函数的传输系数。我们的预测值的扩散渗透性和反射系数表现出合理的协议与实验观察，并符合假设的内皮细胞表面糖萼形成的主要尺寸选择性结构的溶质在微血管通透性。其次，我们考虑了跨微血管壁的流体的细胞旁运输，并通过分析通过内皮表面糖萼和内皮间裂的串行通路的流动来估计水的水力传导率。结果表明，相对于溶质的运输，水分的运输主要取决于裂缝的结构，而不是表面糖萼。相对于施加在内皮表面上的流体剪切应力，我们已经发现，由于表面糖萼的存在，管腔表面上的幅度显着降低，而它们在细胞间裂隙中可能非常高，无论裂隙跨越分子的存在与否。

The luminal surface of vascular endothelial cells is covered by a layer of macromolecules referred to as the glycocalyx. Recent experimental evidence showed that the glycocalyx influences several aspects of vascular function. In the present study, we have studied physiological roles of the endothelial surface glycocalyx from a stand-point of fluid mechanics. We first considered the transport of solutes across microvessel walls. Based on recent detailed measurements of the ultrastructure of the surface glycocalyx, we developed a mathematical model for the glycocalyx, and estimated the transport coefficients as a function of the solute size. Our predicted values of diffusive permeability and the reflection coefficient showed a reasonable agreement with experimental observations, and conformed to the hypothesis that the endothelial surface glycocalyx forms the primary size selective structure to solutes in microvascular permeability. Second, we considered the paracellular transport of fluid across the microvessel wall, and estimated the hydraulic conductivity to water, by analyzing the flow through a serial pathway of the endothelial surface glycocalyx and the interendothelial cleft. It was suggested that, in contrast to the solute transport, the water transport is mainly determined by the structure of the cleft, rather than the surface glycocalyx. With respect to the fluid shear stresses exerted on the endothelial surface, we have found that the magnitudes on the luminal surface are remarkably reduced due to the presence of the surface glycocalyx, whereas they could be extremely high in the intercellular cleft, irrespective of presence or absence of the cleft-spanning molecules.