Fluid shear stress enhanced DNA synthesis in cultured endothelial cells during repair of mechanical denudation

We have previously observed a stimulatory effect of fluid shear stress on the regeneration of cultured endothelial cell layers after mechanical denudation. In this study we examined how fluid shear stress affects endothelial cell DNA synthesis during regeneration. Following mechanical denudation of narrow linear areas, monolayers of bovine aortic endothelial cells cultured on plastic dishes were subjected to shear stress of 1.3–4.1 dynes/cm² for 24–48 hours in a specially designed apparatus. After the application of shear stress, cells were stained with propidium iodide, and its fluorescence intensity, reflecting cellular DNA content, was measured using photometric fluorescence microscopy. The DNA content of cells exposed to shear stress increased significantly more than that of paired, static control cells (p < 0.005 to p < 0.001). The DNA histogram showed that cells exposed to shear stress contained a relatively high proportion of cells located in the S, G₂, and M phases of the cell cycle as compared with the static control. These data suggest that fluid shear stress enhances endothelial cell DNA synthesis during the repair of mechanical denudation.