Response of porcine aortic smooth muscle cells to cyclic tensional deformation in culture

The vascular wall is continuously subjected to pulsatile hydrostatic pressures. However, most studies of smooth muscle cells (SMC) are done under static tissue culture conditions. We have utilized a flexible-bottom culture plate and applied cyclic tensional deformation to cultured SMC. Recent studies have shown that endothelial cells (EC) proliferate but remain randomly oriented when subjected to a force regimen of 3 cycle/min of up to 24% elongation. The current experiments were performed to study the effects of a similar force regimen on SMC. Porcine SMC were seeded at 200,000 cells/35-mm 2 well and permitted to adhere for 24 hr. After 24 hr, the plates were placed on a vacuum-operated stress-providing unit that exerted a 24% elongation on the culture plate substratum at maximum downward deflection of the plate bottom. The stretched cells ( n = 6 wells/day) were subjected to cycles of 10 sec of 24% elongation and 10 sec of relaxation for 7 days. The control cells ( n = 6 wells/day) were subjected to similar incubations as the control group but without cyclic deformation. Media were changed every 24 hr. [ 3H]Thymidine (THY), a precursor for DNA synthesis, was added (2 μCi/well) to plates 24 hr prior to harvesting. On Days 0, 1, 3, 5, and 7 cells were counted and analyzed for THY incorporation. While previous results indicate that pulsatile stretching stimulates EC, the present study indicates that a similar regimen of stress inhibits SMC proliferation. THY incorporation into SMC paralleled the observed changes in cell count. Morphologically, SMC aligned in an annular pattern in response to applied strain, whereas EC maintained a random orientation. We conclude that pulsatile stretching alters the behavior of cells in culture and has opposite effects on EC and SMC.