Spatial Regulation of Inflammation by Human Aortic Endothelial Cells in a Linear Gradient of Shear Stress

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Objective: Atherosclerosis is a focal disease that develops at sites of low and oscillatory shear stress in arteries. This study aimed to understand how endothelial cells sense a gradient of fluid shear stress and transduce signals that regulate membrane expression of cell adhesion molecules and monocyte recruitment. Methods: Human aortic endothelial cells were stimulated with TNF‐α and simultaneously exposed to a linear gradient of shear stress that increased from 0 to 16 dyne/cm2. Cell adhesion molecule expression and activation of NFκ B were quantified by immunofluorescence microscopy with resolution at the level of a single endothelial cell. Monocyte recruitment was imaged using custom microfluidic flow chambers. Results: VCAM‐1 and E‐selectin upregulation was greatest between 2–4 dyne/cm2 (6 and 4‐fold, respectively) and above 8 dyne/cm2 expression was suppressed below that of untreated endothelial cells. In contrast, ICAM‐1 expression and NFκ B nuclear translocation increased with shear stress up to a maximum at 9 dyne/cm2. Monocyte recruitment was most efficient in regions where E‐selectin and VCAM‐1 expression was greatest. Conclusions: We found that the endothelium can sense a change in shear stress on the order of 0.25 dyne/cm2 over a length of ∼ 10 cells, regulating the level of protein transcription, cellular adhesion molecule expression, and leukocyte recruitment during inflammation.