Abstract
Objective:Our purpose was to investigate the effect of the shape of the growth surface (curved versus flat) on flow-induced F-actin organization in endothelial cells. Methods:Human umbilical vein endothelial cells were grown to confluence on curved or flat surfaces. Microchannels (curved surface, 10- to 30-µm radius) or parallel plate flow chambers were perfused (30 minutes to 6 hours) at physiological flow rates (wall shear stress 1 to 10 dyn/cm2). Results:On curved surfaces, the number of central F-actin stress fibers (for cells of equal area) decreased from 4.8 ± 0.3 (mean ± SE, n= 36) (static) to 0.9 ± 0.5 per cell in perfused microchannels. Perfusion with 100 µM histamine prevented this response to flow (5.5 ± 0.8 per cell, n= 12). Stress fibers were initially aligned with the long axis of the microchannel at an angle of 9 ± 0.7° (static). With flow, alignment of the few remaining central F-actin stress fibers with respect to the long axis of the microchannel decreased to 19 ± 4°; this was prevented by perfusion with histamine (5.6 ± 1°). The number of stress fibers per cell, for cells grown on flat surfaces (8.1 ± 0.3, static, n= 36) was significantly greater than for cells on curved surfaces, and did not change with flow (8.1 ± 0.5 per cell, n= 6). On flat surfaces, the stress fiber orientation (with respect to the longitudinal axis of the channel) was 42 ± 1.4° (static) and did not change with flow (38 ± 4.2°). Conclusions:Endothelial cells on curved growth surfaces respond to flow rapidly, with marked changes in F-actin central stress fiber formation. This implicates a tight relationship between cell shape and the environmental substrate, and suggests that the shape of the endothelial cell significantly impacts its ability to respond to its environment. Microcirculation (2000) 7, 419–427.