Rapid displacement of vimentin intermediate filaments in living endothelial cells exposed to flow

Hemodynamic shear stress at the endothelial cell surface induces acute and chronic intracellular responses that regulate vessel wall biology. The cyto skeleton is implicated by acting both as a direct connector to local surfac e deformation and as a distribution network for mechanical forces throughou t the cell; however, direct observation and measurement of its position dur ing flow have only recently become possible. In this study, we directly dem onstrate rapid deformation of the intermediate filament (IF) network in liv ing endothelial cells subjected to changes in hemodynamic shear stress. Tim e-lapse optical sectioning and deconvolution microscopy were performed with in the first 3 minutes after the introduction of flow (shear stress, 12 dyn /cm(2)). Spatial and temporal dynamics of green fluorescent protein-vimenti n Ifs in confluent endothelial cells were analyzed. The imposition of shear stress significantly increased the variability of IF movement throughout t he cell in the x-, y-, and z-directions compared with the constitutive dyna mics noted in the absence of flow. Acute polymerization and depolymerizatio n of the IF network were absent. The magnitude and direction of flow-induce d LF displacement were heterogeneous at the subcellular level. These qualit ative and quantitative data demonstrate that shear stress acting at the lum inal surface of the endothelium results in rapid deformation of a stable IF network.