Growth factor release by smooth muscle cells is dependent on haemodynamic factors

Abnormal proliferation of smooth muscle cells (SMCs) is a key event in the development of the atherosclerotic plaque. The early atherosclerotic plaque localises preferentially in areas of flow separation. The basic mechanisms which correlate haemodynamic forces and atherosclerotic plaque formation are not known. Bovine arterial SMCs were subjected to increasing levels of shear stress for 24 h in an in vitro system. The control group was subjected to similar incubation conditions without flow. SMCs subjected to shear stress released a higher quantity of mitogens, including a platelet derived growth factor (PDGF)-like substance. This mitogenic activity was partially reduced (30%, p < 0.01) by an excess of monospecific anti-PDGF antibody. The release of mitogens was proportional to the level of shear stress and was still evident 24 h after flow cessation. In conclusion, shear stress influences the release of mitogens; this might represent a mechanism which links haemodynamic forces and atherosclerotic plaque formation.