SHEAR-STRESS INCREASES ENDOTHELIAL PLATELET-DERIVED GROWTH-FACTOR MESSENGER-RNA LEVELS

We have investigated the effect of shear stress on platelet-derived growth factor (PDGF) A and B chain mRNA levels in cultured human umbilical vein endothelial cells (hUVEC). The levels of both PDGF A and B mRNA in hUVEC were increased by a physiological shear stress (16 dyn/cm2), reaching a maximum approximately 1.5-2 h after the onset of shear stress and returning almost to control values at 4 h. The peak levels showed a more than 10-fold enhancement for PDGF A mRNA and a 2- to 3-fold increase for PDGF B mRNA (P < 0.05). PDGF A mRNA also showed a shear-dependent increase from 0 to 6 dyn/cm2 (P < 0.05) and then plateaued from 6 to 51 dyn/cm2. PDGF B mRNA levels were elevated as shear stress increased from 0 to 6 dyn/cm2 then declined gradually to a minimum at 31 dyn/cm2 (P < 0.05) and increased again when shear stress rose to 51 dyn/cm2 (P < 0.05). PDGF, a potent smooth muscle cell mitogen and vasoconstrictor, released from the endothelium may regulate the blood flow in vivo. The shear stress-dependent elevation of PDGF A and B mRNA in endothelial cells may be involved in the adaptation of blood vessels to flow mediated by the endothelium.