Rupture of pseudointima in an implanted vascular prosthesis: immunohistological study of plasminogen activators and matrix metalloproteinases.

We investigated late-onset anastomotic stenosis in an implanted prosthetic graft. Rupture of the pseudointima and hemorrhaging from the vasa vasorum were observed at the border of the collagenous tissue and fibrin layer. An immunohistological study showed that the fibrin layer was positive for tPA, but weakly positive for PAI-1. Some neutrophils and monocyte/macrophages in the fibrin layer were immunostained for tPA, uPA, uPAR, and MMP-1, -2 and -3. Some spindle-shaped cells surrounding the graft were immunostained for uPA, uPAR, MMP-1, -2, -3, -7 and -9, and TIMP-1 and -2. The endothelial cells of some microvessels were positive for MMP-1 and -2, and tPA. Some multi-nucleated giant cells were immunostained for MMP-7 and-9, tPA, PAI-1, uPA, and uPAR. Overexpressed MMPs and PAs possibly caused instability of the pseudointima.