STRETCH AFFECTS PHENOTYPE AND PROLIFERATION OF VASCULAR SMOOTH-MUSCLECELLS

The exertion of periodic dynamic strain on the arterial wall is hypoth esized to be relevant to smooth muscle cell morphology and function. T his study has investigated the effect of cyclic mechanical stretching on rabbit aortic smooth muscle cell proliferation and expression of co ntractile phenotype protein markers. Cells were cultured on flexible-b ottomed dishes and cyclic stretch was applied (frequency 30 cycles/min , 15% elongation) using a Flexercell Strain unit. Cyclic stretch poten tiated smooth muscle cell proliferation in serum-activated cultures bu t not in cultures maintained in 0.5% fetal calf serum. Stretching indu ced a serum-independent increase of h-caldesmon expression and this ef fect was reversible following termination of mechanical stimulation. S train was without effect on smooth muscle myosin or calponin expressio n. In cells grown on laminin stretch-induced h-caldesmon expression wa s more prominent than in cells cultured on collagen types I and IV, po ly-L-lysine and gelatin. These data suggest that cyclic mechanical sti mulation possesses dual effect on vascular smooth muscle cell phenotyp e characteristics since it: 1) potentiates proliferation, an attribute of a dedifferentiated phenotype; and 2) increases expression of h-cal desmon considered a marker of a differentiated smooth muscle cell stat e.