Laminar flow through a model of collapsed veins. Morphometric response of endothelial vascular cells to a longitudinal shear stress non uniform cross-wise

We studied the response of vascular endothelial cells to unidirectional lam inar flow through collapsed veins. An original experimental set-up was deve loped, to generate and to map shear stresses with local transverse gradient s. This enabled us to detect changes in the shape of endothelial cells when viscous fluid flow was applied. Porcine vena cava endothelial cells were s eeded on a proof sample placed in the specifically designed flow chamber. P ostconfluent endothelial cells were continuously exposed to a maximum calcu lated wall shear stress of 0.11 Pa (1.1 dyne/cm(2)) and to a maximum calcul ated transverse gradient of 0.045 Pa/mm for 20 hours. This paper deals with the morphometry of single cells and the angle of their major axes with res pect to the flow direction. Cells in confluent monolayer underwent a shear stress intensity-dependent change in shape with a decrease of shape index f rom 0.55 to 0.34. The cells were not uniformly oriented in the direction of flow axes except in the region of larger gradient. In this particular regi on, the cells had a low angle with respect to the flow axes at some coordin ates or exhibited reversal of their major and minor axes with a doubling of cell area. These observations suggest that there have been specific cytosk eleton rearrangements, associated with specific resultant forces over the c ellular surface.