Enhanced intimal thickening of expanded polytetrafluoroethylene grafts coated with fibrin or fibrin-releasing vascular endothelial growth factor in the pig carotid artery interposition model

A, Scanning electron micrographs of noncoated and VEGF–fibrin-coated ePTFE surface before arteriovenous shunt blood perfusion. B, SEM shows increased platelet deposition and microthrombus formation on fibrin and VEGF–fibrin-coated ePTFE surfaces compared with noncoated grafts after 30 minutes of extracorporeal arteriovenous shunt perfusion.

A, Graft histology at the experimental end point, 1 month, shows an increase of neointima formation on ePTFE grafts coated with fibrin or VEGF–fibrin over noncoated ePTFE. The pictures are taken from the grafts’ middle portions. Immunohistochemistry with anti-CD31 for endothelial cells (middle), anti-smooth muscle actin for smooth muscle cells (right), and hematoxylin-eosin (left). The graft-neointimal border (arrows). B, Examination of graft surface ultrastructure at the experimental end point by SEM showed most parts lined by densely grown endothelial cells aligned in direction of flow. Sites of bare ePTFE surface were occasionally observed in noncoated grafts (left). VEGF–fibrin-coated graft with a confluent layer of aligned endothelial cells (right). C, Representative photomicrographs of CD31-stained neointima (upper row) and adventitia (lower row). There were no significant differences in capillary counts among uncoated, fibrin-coated, or VEGF–fibrin-coated grafts (see Table 3). In every study group, capillary formation was substantially higher in adventitia than in neointima. IH, intimal hyperplasia.