THROMBOGENISITY OF ENDOTHELIAL SEEDED VASCULAR GRAFT

It has recently been suggested that endothelial cell (EC) seeding of vascular grafts surfaces may lead to a less thrombo-genic surface. The present investigation was designed to study the capacity of aortic endothelium and neointima developing on seeded grafts to inactivate thrombin. In order to obtain an optimal surface for EC attachment the lyophylized porcine skin (Zenoderm®, Ethicon, Scotland) were used to form tubular grafts. Grafts seeded with enzymatically derived EC from the jugular vein was compared with control grafts that were shamed seeded with culture medium and blood. Animals with seeded grafts were divided into two groups, one group received dipyridamole treatment, theother one remained untreated. The prosthesis were implanted in the abdominal aorta in 21 dogs. Six dogs died due to different complications after surgery. The remaining 15 were sacrified 2 monthsafter graft implantations. The aorta and the grafts were excised divided into two parts, one was fixed for light and scanning electron microscopy, the otherone was analyzed for capacity to inactivate thrombin which enzymatic activity was assayed by an amiodolytic method. The grafts and aortic segments were exposed for 12 U/ml of thrombin solution. After 10 min incubation the enzyme activity decreased in the supernatant and were found in similar amounts on the grafts and aortic surfaces. Thrombin bound to endothelium was rapidly inhibited after exposure to plasma for 30 sec. In contrast, thrombin retained on the neointima of both seeded and shame seeded grafts were only minor inhibited by plasma. The morphological analyses shown that both seeded and shame seeded grafts developed a thin cellular lining covering up to 100% of the specimens’ surface area. The subcellular layer was equal in all groups. No statistical difference in morphology nor in thrombin inhibiting capacity was noted between dipyridamole treated and untreated animals. It is concluded that both the aorticendothelium and graft neointima can take up thrombin but only aortic endothelium can efficiently inactivate it. Seeding of the grafts with endothelial cellsdid not signifcantly improve its capacity to inhibit activated coagulation enzymes.