Flow-induced cytoskeletal changes in endothelial cells growing on curved surfaces

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.

Human umbilical vein endothelial cells were grown to confluence on curved or flat surfaces. Microchannels (curved surface, 10- to 30-microm 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).

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 microM histamine prevented this response to flow (5.5+/-0.8 per cell, n = 12). Stress fibers were initially aligned with tile long axis of the microchannel at an angle of 9+/-0.7 degrees (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 degrees this was prevented by perfusion with histamine (5.6+/-1 degrees). The number of stress fibers per cell, for cells grown on flat surfaces (8.1+/-0.3, static, n = 36) was significantly greater than 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 degrees (static) and did not change with flow (38+/-4.2 degrees).

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.