Morphological responses of single endothelial cells exposed to physiological levels of fluid shear stress.
To investigate the basic processes underlying flow induced morphological changes of vascular endothelial cells (ECs), we have examined the responses of single ECs to fluid mechanical forces under controlled flow conditions in vitro. We made a parallel plate culture flow chamber which could be mounted on an inverted microscope equipped with various optical systems. Video-enhanced microscopic images were recorded with a time-lapse, laser video-disk recorder and then analyzed frame by frame. In contrast to ECs in a confluent monolayer, ECs in sparse culture did not show a parallel alignment to the flow direction even after a 100 h exposure to flow at a wall shear stress level of 10 dyne/cm2. However, rapidly after changing from a weak shear stress (1 dyne/cm2 or less) to a high shear stress (6 dyne/cm2 or more), sparsely cultured ECs extended lamellipodia predominantly on the downstream side and began to migrate preferentially downstream. If the viscosity of the circulating medium was raised by adding a small amount of methyl cellulose or polyvinylpyrrolidone, ECs exhibited these characteristic morphological changes under low wall shear rates (100 s-1 or less). We also found that these changes required Ca2+ in the circulating medium. These results indicate that single ECs can respond to flow in a rapid, shear stress and Ca2+ dependent manner.
Masuda
M
M
Department of Structural Analysis, National Cardiovascular Center Research Institute, Osaka, Japan.
Fujiwara
K
K
D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D008858:Microscopy, Phase-Contrast; D012212:Rheology; D013314:Stress, Mechanical
D002118:Calcium