MT 1‐ MMP evaluation in neointimal hyperplasia in the late follow‐up after prosthesis implantation

Vascular surgical interventions are often burdened with late complications, including thrombosis or restenosis. The latter is generally caused by neointimal hyperplasia. Although extracellular matrix ( ECM ) remodelling is an important part of neointima formation, this process is not clearly understood. The aim of the study was to assess the content and activity of membrane‐type 1 matrix metalloproteinase in human neointima in the late stages of its development. Matrix metalloproteinase‐2 and tissue inhibitor of matrix metalloproteinase‐2 were also evaluated. The research was performed on neointima samples collected during secondary vascular interventions from patients with chronic limb ischaemia who developed vascular occlusion at 6‐18 months after aorto/ilio‐femoral bypass grafting. The control material consisted of segments of femoral arteries collected from organ donors. Western blot and/or ELISA were used for the determination of MT 1‐ MMP and TIMP ‐2 expression. The activity of MT 1‐ MMP was measured by fluorometric assay and that of MMP ‐2 by zymography. We demonstrated significantly increased MT 1‐ MMP protein content in neointima when compared to normal arteries. However, the activity of MT 1‐ MMP was significantly lower in neointima than in control samples. The decreased MT 1‐ MMP activity was concomitant with reduced activity of MMP ‐2. The TIMP ‐2 protein levels in neointima and normal arteries were not significantly different. The results of our study suggest that the reduced activity of MT 1‐ MMP and consequently MMP ‐2 in human neointima may play a role in decreased degradation of ECM components and thus promote neointimal overgrowth.