title: Mapping the dynamics of shear stress-induced structural changes in endothelial cells.
abstract: Hemodynamic shear stress regulates endothelial cell biochemical processes that govern cytoskeletal contractility, focal adhesion dynamics, and extracellular matrix (ECM) assembly. Since shear stress causes rapid strain focusing at discrete locations in the cytoskeleton, we hypothesized that shear stress coordinately alters structural dynamics in the cytoskeleton, focal adhesion sites, and ECM on a time scale of minutes. Using multiwavelength four-dimensional fluorescence microscopy, we measured the displacement of rhodamine-fibronectin and green fluorescent protein-labeled actin, vimentin, paxillin, and/or vinculin in aortic endothelial cells before and after onset of steady unidirectional shear stress. In the cytoskeleton, the onset of shear stress increased actin polymerization into lamellipodia, altered the angle of lateral displacement of actin stress fibers and vimentin filaments, and decreased centripetal remodeling of actin stress fibers in subconfluent and confluent cell layers. Shear stress induced the formation of new focal complexes and reduced the centripetal remodeling of focal adhesions in regions of new actin polymerization. The structural dynamics of focal adhesions and the fibronectin matrix varied with cell density. In subconfluent cell layers, shear stress onset decreased the displacement of focal adhesions and fibronectin fibrils. In confluent monolayers, the direction of fibronectin and focal adhesion displacement shifted significantly toward the downstream direction within 1 min after onset of shear stress. These spatially coordinated rapid changes in the structural dynamics of cytoskeleton, focal adhesions, and ECM are consistent with focusing of mechanical stress and/or strain near major sites of shear stress-mediated mechanotransduction.
authors.affiliation: Department of Biomedical Engineering and Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, Virginia 22908, USA.
authors.forename: Rosalind E
authors.initials: RE
authors.lastname: Mott
authors.forename: Brian P
authors.initials: BP
authors.lastname: Helmke
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002452:Cell Count; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D005456:Fluorescent Dyes; D022001:Focal Adhesions / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D006439:Hemodynamics; D040542:Mechanotransduction, Cellular; D008856:Microscopy, Fluorescence / Q000379:methods; D008955:Models, Cardiovascular; D051419:Paxillin / Q000378:metabolism; D011554:Pseudopodia / Q000378:metabolism; D012235:Rhodamines; D022502:Stress Fibers / Q000378:metabolism; D013314:Stress, Mechanical; D013997:Time Factors; D014746:Vimentin / Q000378:metabolism; D016596:Vinculin / Q000378:metabolism
chemical_list: D000199:Actins; D005353:Fibronectins; D005456:Fluorescent Dyes; D051419:Paxillin; D012235:Rhodamines; D014746:Vimentin; D016596:Vinculin; D049452:Green Fluorescent Proteins