Endothelial Cell Structural Polarity Modulates Shear Stress Control of Directional Migration

Abstract

Restoration of endothelial function after procedures such as angioplasty and stent placement requires directional endothelial cell migration to reestablish a patent cell monolayer. However, endothelial cells near atherosclerotic lesions exhibit non-polarized shape and structure, and the mechanisms by which cells establish directional polarity under physiological hemodynamic forces remains unclear. This study aimed to elucidate whether pre-established cytoskeletal and focal adhesion structure or the direction of fluid shear stress determines the direction of cell migration. Endothelial cells grown on 20-μm lines of fibronectin exhibited an elongated cell shape, and their stress fibers and focal adhesion sites were aligned to the pattern direction. In the absence of shear stress, patterned cells migrated significantly faster than unpatterned confluent cells, and their migration direction was primarily along the line direction. After 10 h of unidirectional steady shear stress (15 dyn/cm2), unpatterned cells doubled their migration speed and aligned their migration primarily to the downstream direction. In contrast, onset of shear stress either parallel or perpendicular to the micropatterned cells did not induce increased speed and directional adaptation, indicating that the elongation in cell structure interfered with the flow-adaptation mechanism for cell migration. Thus, control of endothelial cell morphology using micropatterned lines in the presence of a physiological shear stress magnitude suggests that geometric preconditioning of cell shape and structure dominates over hemodynamic shear stress in determining migration speed and direction.