Mechanical stress stimulates aortic endothelial cells to proliferate

The effects of applied cyclic tensional deformation and relaxation on cultured bovine aortic endothelial cells were examined. Endothelial cells from passages 3 to 9 were seeded in flexible-bottomed plates and allowed to attach for 24 hours. Endothelial cells in the experimental group (n = 6 wells per time point) were placed in a vacuum-operated stress-providing instrument that exerted an average elongation of 10% at maximum downward deflection of the culture plate bottom. The stretched endothelial cells were subjected to repeating cycles of 10 seconds elongation and 10 seconds relaxation from days 1 through 7 in culture. Endothelial cells in the control group (n = 6 wells per time point) were subjected to similar incubation conditions as the experimental group but without tensional deformation. Tritiated thymidine was added to cells 24 hours before harvesting. On days 0, 1, 3, 5, and 7 cells were counted and analyzed for trichloroacetic acid-precipitable tritiated thymidine incorporation. The results showed that 3 cycles/min mechanical stretching stimulated deoxyribonucleic acid synthesis and endothelial cell division. We conclude that cyclic tensional deformation may stimulate endothelial cell proliferation. It is possible that naturally occurring cyclic mechanical deformation in vivo, such as the repetitive stretching and relaxation of aortic tissue by the heart, may invoke a particular pattern of synthesis and division in endothelial cells.