Shear stress modulates cell shape and stress fiber expression in the rat umbilical vessel endothelial cells

In order to evaluate the factors modulating morphology and cytoskeletal organization in developing rat umbilical vessel endothelial cells, changes in cell shape and actin stress fiber expression in the endothelial cells were investigated using fluorescent cytochemistry and rheological techniques. Oblong umbilical vessel endothelial cells at 14 days of gestation had no stress fibers. They changed to have very slender cell shape and many long stress fibers by 17 days of gestation. While the umbilical vein endothelial cells maintained such cell shape and stress fibers even at the day of delivery, the umbilical artery endothelial cells reverted to a plump shape and lost their stress fibers after 20 days of gestation. The intensity of tension loaded in vascular axial direction and of expansion force due to blood pressure in the umbilical vessels remained almost unchanged during the latter half of the gestation. On the other hand, shear rate in the umbilical vessels increased rapidly after 16 days of gestation. These results indicate that shear stress influences morphology and stress fiber expression in the umbilical vessel endothelial cells. Such stress fibers may serve to maintain endothelial cell structural integrity to counteract increasing shear stress.