Fibrin(ogen) and von Willebrand factor deposition are associated with intimal thickening after balloon angioplasty of the rabbit carotid artery

The aim of the study was to assess the contribution of thrombus incorporation into neointimal thickening in the rabbit carotid artery after deep vascular injury induced by balloon angioplasty compared with superficial vascular injury induced by a perivascular collar. Besides CD 31 (PECAM I), vimentin, alpha-smooth muscle actin, rabbit anti-macrophage monoclonal antibody and proliferating cell nuclear antigen, fibrin(ogen) and von Willebrand factor (vWF) deposition was assessed immunohistochemically. Angioplasty was performed in 47 rabbits and evaluated immediately (n=7), after 6 hours (n=4), and after 1 (n=7), 2 (n=9), or 3 (n=20) weeks. A collar was placed in 29 rabbits and evaluated immediately (n=5), after 6 hours (n=5), and after 1 (n=7), 2 (n=10), or 3 (n=2) weeks. After dilatation, the arteries were extensively denuded of endothelium, the internal elastic membrane was ruptured and blood-filled clefts were present in the media, pointing to deep vascular (type III) injury. Six hours later, mural fibrin(ogen) thrombi were formed, specially at sites with severe damage. This fibrin(ogen) matrix became infiltrated by phagocytes and smooth muscle cells. A luminal cap covered by regenerating endothelium was formed, demonstrating increased immunoreactivity to vWF. vWF was deposited in the extracellular neointimal spaces. Fibrin(ogen) thrombus deposition and incorporation appeared to be protracted phenomena for at least 2 weeks. After collar placement, minimal endothelial denudation was documented, pointing to fecal superficial (type I) vascular injury. In subsequent weeks, neointimal thickening was associated with vWF deposition but not with fibrin(ogen) thrombus incorporation. In conclusion, mural fibrin(ogen) thrombus formation and incorporation contribute to neointima formation after deep vascular injury and seem to occur for several weeks after the initial insult.