Shear stress induces transforming growth factor-beta1 release by arterial endothelial cells

Background. Myointimal hyperplasia is a common complication after vascular reconstruction. Increasing shear stress has been shown to reduce formation of myointimal hyperplasia. The aims of our study were (1) to analyze the correlation between shear stress and release of transforming growth factor (TGF)-beta(1) by endothelial cells and (2) to determine the effect of TGF-beta(1) on smooth muscle cell proliferation. Methods. Bovine arterial endothelial cells were subjected to increasing shear stress in an in vitro serum-free system. The release of TGF-beta(1) by endothelial cells was assessed by enzyme-linked immunosorbent assay and Western blot analysis. The effect of TGF-beta(1) on the proliferation of the subconfluent monolayer of bovine smooth muscle cells was determined by tritiated thymidine uptake. Results. Shear stress induced a significant increase of the release of TGF-beta(1) by endothelial cells (p < 0.001). This phenomenon was proportional to the level of shear stress. The amount of TGF-beta(1) released by endothelial cells subjected to shear stress had a significant inhibitory effect on growth rate and tritiated thymidine uptake of smooth muscle cells. Conclusions. On the basis of the results of our study, we conclude that increasing shear stress induces release of TGF-beta(1) by arterial endothelial cells in a concentration that has a clear inhibitory effect on smooth muscle cell proliferation. This phenomenon could explain the inhibitory effect of increasing shear stress on the formation of myointimal hyperplasia.