The hypoxic microenvironment existing in vivo is known to significantly affect cell morphology and dynamics, and cell group behaviour. Collective migration of vascular endothelial cells is essential for vasculogenesis and angiogenesis, and for maintenance of monolayer integrity. Although hypoxic stress increases vascular endothelial permeability, the changes in collective migration and intracellular junction morphology of vascular endothelial cells remain poorly understood. This study reveals the migration of confluent vascular endothelial cells and changes in their adherens junction, as reflected by changes in the vascular endothelial (VE)-cadherin distribution, under hypoxic exposure. Vascular endothelial monolayers of human umbilical vein endothelial cells (HUVECs) were formed in microfluidic devices with controllability of oxygen tension. The oxygen tension was set to either normoxia (21% O2) or hypoxia (<3% O2) by supplying gas mixtures into separate gas channels. The migration velocity of HUVECs was measured using particle image velocimetry with a time series of phase-contrast microscopic images of the vascular endothelial monolayers. Hypoxia inducible factor-1α (HIF-1α) and VE-cadherin in HUVECs were observed after exposure to normoxic or hypoxic conditions using immunofluorescence staining and quantitative confocal image analysis. Changes in the migration speed of HUVECs were observed in as little as one hour after exposure to hypoxic condition, showing that the migration speed was increased 1.4-fold under hypoxia compared to that under normoxia. Nuclear translocation of HIF-1α peaked after the hypoxic gas mixture was supplied for 2 h. VE-cadherin expression was also found to be reduced. When ethanol was added to the cell culture medium, cell migration increased. By contrast, by strengthening VE-cadherin junctions with forskolin, cell migration decreased gradually in spite the effect of ethanol to stimulate migration. These results indicate that the increase of cell migration by hypoxic exposure was attributable to loosening of intercellular junction resulting from the decrease of VE-cadherin expression.

中文翻译：

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低氧暴露下单层血管内皮细胞的迁移。

已知体内存在的低氧微环境会显着影响细胞的形态和动力学以及细胞群的行为。血管内皮细胞的集体迁移对于血管生成和血管生成以及维持单层完整性至关重要。尽管低氧应激增加了血管内皮的通透性，但对血管内皮细胞的集体迁移和细胞内连接形态的变化仍然知之甚少。这项研究揭示了低氧暴露条件下汇合的血管内皮细胞的迁移及其粘附连接的变化，这反映为血管内皮（钙）-钙粘蛋白分布的变化。人脐静脉内皮细胞（HUVEC）的血管内皮单层是在微流控装置中形成的，具有可控的氧张力。通过将气体混合物供应到单独的气体通道中，将氧气张力设置为常氧（21％O2）或低氧（<3％O2）。HUVEC的迁移速度使用粒子图像测速仪和血管内皮单层的相衬显微图像的时间序列进行测量。使用免疫荧光染色和定量共聚焦图像分析，在暴露于常氧或低氧条件下后，观察到HUVECs中的缺氧诱导因子-1α（HIF-1α）和VE-cadherin。暴露于低氧条件下仅一小时，HUVECs的迁移速度就发生了变化，这表明低氧条件下的迁移速度是常氧条件下的1.4倍。在提供低氧气体混合物2小时后，HIF-1α的核易位达到峰值。还发现VE-钙粘着蛋白表达降低。当将乙醇添加到细胞培养基中时，细胞迁移增加。相比之下，尽管有乙醇刺激迁移，但通过用福司可林加强VE-钙黏着蛋白连接，细胞迁移逐渐减少。这些结果表明，低氧暴露引起的细胞迁移的增加归因于VE-钙粘着蛋白表达降低导致的细胞间连接的松动。