Expression of plasminogen activator inhibitor-1 mRNA in healthy, atherosclerotic and thrombotic human arteries and veins.

Plasminogen activator inhibitor-1 (PAI-1), specific inhibitor of plasminogen activators (PA), plays an important role in the regulation of fibrinolysis. Increased levels of PAI-1 have been associated with vascular disease such as thrombosis and atherosclerosis. In the present study the expression of PAI-1 mRNA in human healthy, atherosclerotic and thrombotic blood vessel walls was quantified by RNA-RNA hybridization in solution and localized by in situ hybridization. The mean expression of PAI-1 mRNA was significantly higher in healthy arteries (0.86 pg/microgram total RNA) than in healthy veins (0.29 pg/microgram total RNA), p < 0.01. The mean PAI-1 mRNA expression in thrombotic arteries (1.72 pg/micrograms total RNA) was significantly higher than that in healthy arteries, p < 0.05, and the mean PAI-1 mRNA expression in thrombotic veins (1.29 pg/micrograms total RNA) was significantly higher than that in healthy veins, p < 0.01. By in situ hybridization PAI-1 mRNA was detected in the intima, media and adventitia of healthy arteries and healthy veins. In atherosclerotic arteries PAI-1 mRNA was detected in the atherosclerotic plaque and in the medial and adventitial layers below the plaque. An increased expression of PAI-1 mRNA was found in the intimal layer of a thrombotic vein. The increased expression of PAI-1 mRNA in thrombotic arteries and veins indicates a role for PAI-1 in thrombogenesis.