Modulation of arterial smooth muscle cell growth by haemodynamic forces

To define the correlation between flow dynamics and the proliferation of arterial smooth muscle cells (SMCs), bovine arterial SMC were subjected to increasing laminar flow shear stress in an in vitro system. Smooth muscle cells were seeded in a fibronectin-coated polystyrene cylinder at 5 x 10(5) cells/tube. The experimental groups were subjected to increasing shear stress (3, 6, 9 dyn cm-2) for a 24-h period. The control group was subjected to similar incubation conditions without flow. Shear stress reduced significantly (p less than 0.01) the 24-h incorporation of tritiated thymidine and cell proliferation. This effect was proportional to the level of shear stress and was still evident 24 h after flow cessation. Flow cytometry demonstrated a lower percentage of SMCs in S-phase with increasing shear stress. Extrapolation of these findings to the clinical setting might explain how unphysiological shear stress can predispose to the abnormal proliferation rate of SMCs and early plaque formation.