Noria Sabrena, Xu Feng, McCue Shannon, Jones Mara, Gotlieb Avrum I, Langille B Lowell
Toronto General Research Institute, University Health Network, Toronto, Canada.
Am J Pathol. 2004 Apr;164(4):1211-23. doi: 10.1016/S0002-9440(10)63209-9.
Fluid shear stress greatly influences the biology of vascular endothelial cells and the pathogenesis of atherosclerosis. Endothelial cells undergo profound shape change and reorientation in response to physiological levels of fluid shear stress. These morphological changes influence cell function; however, the processes that produce them are poorly understood. We have examined how actin assembly is related to shear-induced endothelial cell shape change. To do so, we imposed physiological levels of shear stress on cultured endothelium for up to 96 hours and then permeabilized the cells and exposed them briefly to fluorescently labeled monomeric actin at various time points to assess actin assembly. Alternatively, monomeric actin was microinjected into cells to allow continuous monitoring of actin distribution. Actin assembly occurred primarily at the ends of stress fibers, which simultaneously reoriented to the shear axis, frequently fused with neighboring stress fibers, and ultimately drove the poles of the cells in the upstream and/or downstream directions. Actin polymerization occurred where stress fibers inserted into focal adhesion complexes, but usually only at one end of the stress fiber. Neither the upstream nor downstream focal adhesion complex was preferred. Changes in actin organization were accompanied by translocation and remodeling of cell-substrate adhesion complexes and transient formation of punctate cell-cell adherens junctions. These findings indicate that stress fiber assembly and realignment provide a novel mode by which cell morphology is altered by mechanical signals.
流体剪切应力极大地影响血管内皮细胞的生物学特性以及动脉粥样硬化的发病机制。内皮细胞会因生理水平的流体剪切应力而发生显著的形态变化和重新定向。这些形态变化会影响细胞功能；然而，产生这些变化的过程却知之甚少。我们研究了肌动蛋白组装与剪切诱导的内皮细胞形态变化之间的关系。为此，我们对培养的内皮细胞施加高达96小时的生理水平剪切应力，然后使细胞通透，并在不同时间点将它们短暂暴露于荧光标记的单体肌动蛋白中，以评估肌动蛋白组装情况。或者，将单体肌动蛋白显微注射到细胞中，以持续监测肌动蛋白的分布。肌动蛋白组装主要发生在应力纤维的末端，应力纤维同时会重新定向到剪切轴，经常与相邻的应力纤维融合，并最终推动细胞的两极向上游和/或下游方向移动。肌动蛋白聚合发生在应力纤维插入粘着斑复合物的位置，但通常只发生在应力纤维的一端。上游和下游的粘着斑复合物都没有表现出偏好。肌动蛋白组织的变化伴随着细胞 - 基质粘着复合物的易位和重塑以及点状细胞 - 细胞粘附连接的短暂形成。这些发现表明，应力纤维的组装和重新排列提供了一种新的模式，通过这种模式，细胞形态可以被机械信号改变。
