Abstract: AimTo study the effect of antiparallel phosphorothioate triplex-forming oligonucleotide (apsTFO) matching with the shear stress response element (SSRE) of tissue factor (TF) gene promoter region on the expression of TF in endothelial cells (ECs) of rat common carotid artery stenosis. Methods The model of common carotid artery middle segment stenosis was established by silica gel pipe loop ligation in SD rats. The mRNA expression and protein synthesis of TF, early growth response-1 (Egr-1) and specificity protein 1 (Sp1) were measured by in situ hybridization (ISH) and immunohistochemistry (IHC) technique. GT21-apsTFO, GT20-apsTFO, GT20-psTFO and FITC-labeled apsTFO, matching with the SSRE of TF gene promoter region, were designed, and intravenously injected into rats at 0.5 h before operation. TFO was detected 4 h after the operation, and the mRNA expression and protein synthesis of TF, Egr-1 and Sp1 were detected 6 h after the operation. ResultsThere were much fluorescence in vascular tissue, especially in the nuclear of ECs 4.5 h after the injection of apsTFO. The mRNA expression and protein synthesis of TF reduced by 22%-23% with injection of GT20-apsTFO 6.5 h after stenosis (P<0.01) and by 10%-11% with GT21-apsTFO at the same time (P<0.05). The inhibition by GT20-apsTFO was stronger than that of the GT21-apsTFO (P<0.05). The expression of TF was not inhibited by the GT20-psTFO (P>0.05). The mRNA expression and protein synthesis of Egr-1and Sp1 did not change in the rat treated with GT20-apsTFO, GT20-psTFO and GT21-apsTFO (P>0.05). ConclusionapsTFO could mero-inhibit the expression of TF gene but could not change the expression of Egr-1 and Sp1 protein.