Lack of Plasminogen Activator Inhibitor-1 Promotes Growth and Abnormal Matrix Remodeling of Advanced Atherosclerotic Plaques in Apolipoprotein E–Deficient Mice

Epidemiological studies suggest that elevated plasma levels of plasminogen activator inhibitor-1 (PAI-1) predispose an individual to ischemic heart disease or promote plaque progression by inhibiting fibrinolysis. In the present study, loss of PAI-1 in apolipoprotein E (apoE)-deficient (apoE −/− :PAI-1 −/− ) mice promoted the growth of advanced atherosclerotic plaques, which was due to enhanced extracellular matrix deposition. ApoE −/− :PAI-1 −/− plaques also exhibited collagen fiber disorganization and degradation. Immunostaining and bone marrow transplantation revealed that smooth muscle cells, not macrophages, primarily expressed PAI-1 in plaques. Thus, although PAI-1 may promote plaque growth because of its antifibrinolytic properties, the present study reveals a protective role for PAI-1 by limiting plaque growth and preventing abnormal matrix remodeling.