Elongation and Random Orientation of Bovine Endothelial Cells in Response to Hydrostatic Pressure: Comparison with Response to Shear Stress

Morphological responses of cultured bovine endothelial cells (ECs) exposed to hydrostatic pressure were investigated. ECs were exposed to physiological blood pressure under a hydrostatic head of culture medium for 24 hours. Pressured ECs exhibited marked elongation and orientation with the random direction, together with development of centrally located, thick stress fibers. Pressured ECs also exhibited multilayered structure unlike under control conditions. The area and the shape index value significantly decreased after exposure to hydrostatic pressure, which were in good agreement with the results from conventional flow-imposed experiments. In contrast, a tortuosity index, which was newly introduced to represent cell shape tortuosity, significantly increased for pressured ECs, while sheared ECs had no difference in turtuosity index from control. In addition, pressured ECs aligned with no predominant direction, while sheared ECs aligned in the flow direction. These results indicate that ECs can respond very specifically to the type of imposed mechanical stimuli such as hydrostatic pressure and fluid shear stress.