Background. Myointimal hyperplasia is a common complication after vasc
ular 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 transform
ing growth factor (TGF)-beta(1) by endothelial cells and (2) to determ
ine the effect of TGF-beta(1) on smooth muscle cell proliferation. Met
hods. Bovine arterial endothelial cells were subjected to increasing s
hear stress in an in vitro serum-free system. The release of TGF-beta(
1) by endothelial cells was assessed by enzyme-linked immunosorbent as
say and Western blot analysis. The effect of TGF-beta(1) on the prolif
eration of the subconfluent monolayer of bovine smooth muscle cells wa
s determined by tritiated thymidine uptake. Results. Shear stress indu
ced a significant increase of the release of TGF-beta(1) by endothelia
l 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 growt
h rate and tritiated thymidine uptake of smooth muscle cells. Conclusi
ons. On the basis of the results of our study, we conclude that increa
sing shear stress induces release of TGF-beta(1) by arterial endotheli
al cells in a concentration that has a clear inhibitory effect on smoo
th muscle cell proliferation. This phenomenon could explain the inhibi
tory effect of increasing shear stress on the formation of myointimal
hyperplasia.