EFFECT OF PRESSURE ON CULTURED SMOOTH-MUSCLE CELLS

Recent studies indicate that smooth muscle cell (SMC) growth and morph ology can be modulated by repetitive strain. However, there is very li ttle known about the influence of pressure, without an associated cell stretch, on SMC phenotype. To study this, cultured bovine aortic SMC were grown on a rigid surface and placed in a custom-designed plexigla ss pressure chamber with a carefully regulated 5% CO2/air environment. SMC were exposed to either atmospheric, 105 mm Hg or 120/90 mm Hg pre ssure at a frequency of 60 cycles/min (0.5 s systole, 0.5 s diastole). SMC number was determined on days 1, 3, 5, 7 and 9. SMC exposed to pr essure were more elongated and displayed a significant increase in cel l number by day 5.which persisted until day 9. Lactate dehydrogenase ( LDH) in the conditioned media, an index of cytotoxicity, was not diffe rent between the groups at each time point. There was also no differen ce in pH or pCO(2) of the media of SMC in any group. This is the first report of the effects of increased static and pulsatile pressure on S MC in vitro and indicates an increased proliferative rate. We hypothes ize that the systemic pressure that the blood vessel is exposed to in vivo may have a significant regulatory influence on the phenotype of t he smooth muscle cells which may affect the SMC response to injury or stimuli.