Redistribution of von Willebrand factor in porcine carotid arteries after balloon angioplasty

von Willebrand factor (VWF) is a well-characterized multimeric glycoprotein present in platelets and plasma and synthesized by vascular endothelial cells and megakaryocytes. Its role in platelet-vessel wall interactions has been studied extensively, but its involvement in intravascular events after balloon angioplasty has not been clarified. VWF antigen is not present in porcine arterial endothelium (except for the pulmonary artery) but is readily detected in porcine venous endothelial cells. We have examined the localization of VWF in porcine vessel walls during neointima formation after bilateral carotid balloon-angioplasty. Endothelium was denuded by balloon injury but regenerated by 7 days and was fully confluent by 42 days. VWF was detected at the site of injury in localized, adherent platelet aggregates at 10 minutes after angioplasty that were not present at later time points. A well-demarcated homogeneous layer of VWF was observed on the luminal surface from 30 minutes to day 7, but there was a progressive shift of positive staining from the lumen to the outer media from days 1 to 7. VWF was also strongly detected at sites proximal and distal to the balloon injury from 30 minutes to day 7, although endothelial disruption was minimal and the monolayer remained substantially intact at these sites. Regrowing endothelial cells appeared to contain granular VWF from days 12 to 21, but this was not readily evident at later time points. The results suggest that balloon injury is associated with deposition and medial absorption of plasma or platelet VWF in this porcine model over a time period that precedes and overlaps vascular smooth muscle proliferation and endothelial recoverage. The findings provide evidence to support the concept of a wider role for VWF in tissue injury responses.