(Circulation. 1997;96:1783-1789.)
© 1997 American Heart Association, Inc.
Articles |
Plasminogen Activator Inhibitor-1 in Neointima of Vein Grafts
Its Role in Reduced Fibrinolytic Potential and Graft Failure
From the Wihuri Research Institute, Helsinki (P.K., R.L.); the Department of Virology, Haartman Institute, University of Helsinki (V.S., A.V.); the Department of Pathology, Haartman Institute, University of Helsinki (O.C.); and the Division of Vascular Surgery, Department of Surgery, Helsinki University Central Hospital (M.L.), Finland.
Correspondence to Riitta Lassila, Wihuri Research Institute, Kalliolinnantie 4, FIN-00140, Helsinki, Finland.
Background Intimal smooth muscle cell proliferation is an underlying pathogenetic mechanism for neointimal hyperplasia and consequent vein graft failure. This study characterizes the expression of tissue-type plasminogen activator (TPA), urokinase-type plasminogen activator (UPA), and plasminogen activator inhibitor-1 (PAI-1) in hyperplastic vein grafts and normal venous tissue.
Methods and Results Failing graft and control vein specimens from 14 donors were homogenized, and TPA and PAI-1 were quantified with ELISA. The amount of PAI-1 was seven times higher (4.2±2.1 versus 0.6±0.6 ng/mg protein, P<.005), but the TPA antigen content was markedly lower (3.1±2.1 versus 8.1±3.7 ng/mg protein, P<.005) in the stenosed grafts compared with the control veins. Strong immunohistochemical PAI-1 reactivity and in situ hybridization signals for PAI-1 and UPA mRNA were associated with the smooth muscle cells of the thickened intima of the grafts. Functional assays of the graft specimens showed an increased UPA/TPA ratio and a decreased total fibrinolytic activity in comparison with normal veins.
Conclusions Upregulation of PAI-1 mRNA expression and markedly increased amounts of PAI-1 antigen were detected in the vein grafts after the development of neointima. Furthermore, augmented UPA activity was found in the graft wall, but TPA was clearly depleted. Altogether, our findings imply decreased fibrinolytic potential in the stenosed graft, which may contribute to the graft occlusion.
Key Words: bypass • fibrinolysis • peripheral vascular disease • plasminogen activator • veins
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