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

本研究的目的是从血管对流动血液产生的剪切应力的反应的角度来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微血管形成的影响。用活体显微技术观察了α 1受体阻滞剂哌唑嗪处理7-23天后兔耳室内新生微血管的形成过程。哌唑嗪治疗（血流负荷）的家兔显示微血管形成显著增加。哌唑嗪组兔的血管密度比对照组高21%。内皮细胞分泌的多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细胞因子的影响。培养的人脐静脉内皮细胞在平行平板型流动加载装置中受到15达因/cm ^2的剪切力作用24小时，用ELISA法测定粒细胞/巨噬细胞集落刺激因子（GM-CSF）的浓度变化，剪切力使GM-CSF的产量增加6倍，而对其他CSF如粒细胞CSF和巨噬细胞CSF的产生无影响。Run-on实验和荧光素酶实验均表明切应力不影响GM-CSF基因的转录，而放线菌素D追踪实验显示，在剪切应力作用下，GM-CSF mRNA的半衰期明显延长。这表明剪切应力通过mRNA稳定化增加了内皮细胞中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.