Aortic smooth muscle cells respond to soluble proteins released by aortic endothelial cells after fluid flow exposure

Vascular functioning is affected by blood flow, as well as the behavior of vascular endothelial and smooth muscle cells. For example, many studies have shown that endothelial cell morphology and gene expression are dependent on the presence of laminar fluid flow within the blood vessel. It is also reasonable to hypothesize that smooth muscle cell behavior is affected by chemical mediators (such as growth factors) released by these flow-exposed endothelial cells. Using a parallel plate flow chamber, this study confirmed up-regulation of COX-2, ecNOS, and PDGF in endothelial cells exposed to laminar flow (shear stress = 10.44 dyne/cm²) for either 6 or 24 hours. For the first time, smooth muscle cells grown in a static environment were exposed to "conditioned" media, or supernatant media containing any soluble factors released by endothelial cells under such flow conditions. Our results have provided the first evidence of altered smooth muscle cell proliferation and gene expression in response to this conditioned medium. Understanding the release of these mediators by vascular endothelial cells and their effects on neighboring smooth muscle cell function will aid in elucidating the mechanism behind atherosclerosis development.