SEEDING OF VASCULAR GRAFTS WITH AN IMMORTALIZED HUMAN DERMAL MICROVASCULAR ENDOTHELIAL-CELL LINE

Small-caliber vascular grafts (< 6 mm) for arterial bypass frequently fail owing either to acute thrombosis or long-term fibrosis. One strat egy to enhance patency is the coverage (''seeding'') of luminal polyme ric graft surfaces with endothelial cells (EC), which may in themselve s be thromboresistant and antiproliferative, or which could be transfe cted with genes whose products are thrombolytic or growth-inhibitory. Advances in understanding of EC-biomaterial interaction have led to im provements in cell coverage and retention, but the sources of EC for s uch procedures have been limited to large vessels (autologous veins) a nd microvascular endothelium isolated from autologous adipose tissue. Before the practice of graft seeding can gain widespread clinical acce ptance, the practical constraints of EC harvest, EC culture, and quick access to the seeded prosthesis for the surgical procedure must be ov ercome. Ideally, an EC line with a high proliferative capacity could b e preestablished on the grafts, which could then be cryopreserved and made available as needed. The authors have seeded Dacron graft materia l with an immortalized human dermal microvascular EC line, HMEC-1. The se cells were initially transfected with simian virus 40A large T anti gen and have been passaged more than 100 times without signs of senesc ence. They also express von Willebrand factor, take up acetylated low density lipoproteins, and rapidly form tubes when cultured on matrigel . Confluent coverage of Dacron graft segments, either untreated or coa ted with gelatin, was achieved in two weeks. The cells formed a monola yer over topographically elevated regions or appeared to be > one laye r thick in other areas. Cells were also shown to remain viable after f reezing. These results suggest a potential practical method for enhanc ement of small-caliber vascular graft biocompatibility in humans.