The alignment of arterial endothelial cells (ECs) with the mean wall shear stress (WSS) vector is the prototypical example of their responsiveness to flow. However, evidence for this behaviour rests on experiments where many WSS metrics had the same orientation or where they were incompletely characterized. In the present study, we tested the phenomenon more rigorously. Aortic ECs were cultured in cylindrical wells on the platform of an orbital shaker. In this system, orientation would differ depending on the WSS metric to which the cells aligned. Variation in flow features and hence in possible orientations was further enhanced by altering the viscosity of the medium. Orientation of endothelial nuclei was compared with WSS characteristics obtained by computational fluid dynamics. At low mean WSS magnitudes, ECs aligned with the modal WSS vector, while at high mean WSS magnitudes they aligned so as to minimize the shear acting across their long axis (transverse WSS). Their failure to align with the mean WSS vector implies that other aspects of endothelial behaviour attributed to this metric require re-examination. The evolution of a mechanism for minimizing transverse WSS is consistent with it having detrimental effects on the cells and with its putative role in atherogenesis.

中文翻译：

---

内皮细胞与平均壁剪切应力向量不对齐


动脉内皮细胞（EC）与平均壁剪切应力（WSS）矢量的对齐是它们对血流响应的典型例子。然而，这种行为的证据依赖于实验，其中许多 WSS 指标具有相同的方向或它们的特征不完整。在本研究中，我们更严格地测试了这一现象。主动脉内皮细胞在轨道摇床平台上的圆柱形孔中培养。在此系统中，方向会根据单元对齐的 WSS 度量而有所不同。通过改变介质的粘度，流动特征的变化以及可能的方向的变化被进一步增强。将内皮细胞核的方向与通过计算流体动力学获得的 WSS 特征进行比较。在低平均 WSS 幅度时，EC 与模态 WSS 矢量对齐，而在高平均 WSS 幅度时，EC 对齐以最小化作用于其长轴（横向 WSS）的剪切力。它们未能与平均 WSS 向量对齐意味着归因于此指标的内皮行为的其他方面需要重新检查。最小化横向 WSS 的机制的演变与它对细胞的有害影响及其在动脉粥样硬化形成中的假定作用是一致的。