Analysis of Anigogenesis and Shear-Mismatching Response Based on Endothelial Cell Biomechanics

本研究的目的是从血管对血流产生的切应力的反应的角度分析生理性血管生成或病理性内膜增厚的机制。在体内研究了血流量增加对新的微血管形成的影响。应用活体显微镜技术，观察了α-1受体阻滞剂(哌唑嗪)作用7-23天后，兔耳腔内新生微血管的形成过程。经哌唑嗪处理的(血流负荷)兔的微血管形成显著增加。治疗组兔血管终末密度较对照组增加近21%，内皮细胞分泌的各种生长因子和细胞因子参与了血管内膜增厚。在体外研究了切应力对内皮细胞产生环状细胞因子的影响。在平行板式流动加载装置中，将培养的人脐静脉内皮细胞置于15dynes/cm2的剪切力作用24 h后，用ELISA测定GM-CSF的浓度变化。剪切力使GM-CSF的产生增加6倍，而对粒细胞-CSF和巨噬细胞-CSF等其他CSF的产生没有影响。但放线菌素D-Chase实验显示，剪切力作用下细胞中GM-CSF mRNA的半衰期明显长于对照组。这表明剪切力通过稳定内皮细胞中的mRNA来增加GM-CSF的产生。

The aim of the present study was to analyze the mechanisms for physiological angiogenesis or pathological intimal thickening from a view point of vascular responses to shear stress produced by flowing blood. The effect of an increase in blood flow on new microvascular formation was studied in vivo. Using an intravital microscopic technique, we observed die process of new microvascular formation in the ear chamber of rabbits treated with alpha 1 blocker (prazosin) for 7-23 days. The prazosin-treated (blood flow-loaded) rabbits showed a marked increase in microvascular formation. The ultimate vascular density in the prazosin-treated rabbit was almost 21% higher than that in the control rabbit Various growth factors and cytokines which are secreted from endothelial cells are involved in vascular intimal thickening. The effect of shear stress on the production of cylokines by endothelial cells was investigated in vitro. Cultured human umbilical vein endothelial cells were subjected to a shear stress of 15 dynes/cm^2 for 24 h in a parallel plate type of flow-loading device and the changes in the concentration of granulocyte/macrophage-colony stimulating factor (GM-CSF) were determined by ELISA.Shear stress increased the production of GM-CSF 6-times the control level, while it had no effect on the production of other CSFs such as granulocyte-CSF and macrophage-CSF.Both run-on assay and luciferase assay demonstrated that shear stress did not affect transcription of GM-CSF gene, but actinomycin-D chase experiments revealed that the half-life of GM-CSF mRNA was significantly longer in shear-stressed cells than that in control cells. This indicates that shear stress augments GM-CSF production in endothelial cells via mRNA stabilization.