Production and inhibition of the gelatinolytic matrix metalloproteinases in a human model of vein graft stenosis

Objectives: human vein graft stenoses are caused by intimal hyperplasia, a process which is characterised by extensive degradation and accumulation of extracellular matrix. This study investigated the role of the matrix metal loproteinases (MMPs) - the principal physiological mediators of extracellul ar matrix degradation - in the development of intimal hyperplasia in cultur ed human long saphenous vein. Design: experimental study. Materials and methods: paired venous segments with the endothelium intact o r denuded were cultured in standard conditions for 14 days. At the terminat ion of culture, MMPs were extracted from one half of the tissue, whilst the remainder of the vein was prepared for histological examination. Results: stereologic analysis revealed that the endothelium intact veins de veloped a significantly thicker neointima when compared to the denuded veno us segments (20 mu m v. 0 mu m, p = 0.006). Quantification of MMPs by subst rate gel enzymography demonstrated that the development of a neointima was associated with increased production of the gelatinolytic MMP-9 (p = 0.03) in intact veins. Immunocytochemistry showed that the MMP-9 localised to the internal elastic lumina, which suggested a role in facilitating smooth-mus cle-cell migration into the intima. The role of MMPs-2 and -9 in intimal hyperplasia was further investigated b y culturing intact venous segments with a therapeutic concentration of doxy cycline - a potent MMP inhibitor. These experiments demonstrated that a the rapeutic dose of doxycycline significantly reduced neointimal thickness (co ntrol 21 mu m, doxycycline 10 mg/l-5.5 mu m), in conjunction with a signifi cant reduction in the production of MMP-9. Conclusions: these data suggest that elevated levels of MMPs may play a sig nificant role in the development of human intimal hyperplasia and that inhi bition of these enzymes may offer a potential therapeutic strategy for the prevention of hyperplastic lesions.