AimTo investigate the effects of DNA enzyme targeting early growth response factor-1 （Egr-1) mRNA (ED5) on the expression of PAI-1 after vascular balloon injury and the mechanism of inhibiting neointimal hyperplasia.MethodsTo establish the intimal injury model of left carotid artery in rats.Ninty-six rats were randomly divided into four groups, sham group, MgCl₂ group, FuGENE6 group and ED5 group.Six rats were killed at 3 d, 7 d, 14 d and 21 d after operation.Vascular sections were stained with heamotoxylin and eosin to identify pathological changes of vascular by light microscope.Immunohistochemistry stain was used to test the expression of Egr-1 inarterial wall.ELISA kit was used to test the expression of PAI-1 gene in plasma.ResultsThe levels of Egr-1 were reduced after treatment with ED5, and there were significant differences between the ED5 group and the MgCl₂ and FuGENE6 group (p<0.01).The expression of PAI-1 reduced at every time point in ED5 group (p<0.01).Compared with MgCl₂ group and FuGENE6 group, the intimal and media thickness and the stenosis rate of vessel in ED5 group at every time points after operation was significantly lowered (p<0.01).ConclusionThe level of PAI-1 increase after balloon injury.ED5 can through