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 strategy to enhance patency is the coverage ("seeding") of luminal polymeric graft surfaces with endothelial cells (EC), which may in themselves be thromboresistant and antiproliferative, or which could be transfected with genes whose products are thrombolytic or growth-inhibitory. Advances in understanding of EC-biomaterial interaction have led to improvements in cell coverage and retention, but the sources of EC for such procedures have been limited to large vessels (autologous veins) and microvascular endothelium isolated from autologous adipose tissue. Before the practice of graft seeding can gain widespread clinical acceptance, the practical constraints of EC harvest, EC culture, and quick access to the seeded prosthesis for the surgical procedure must be overcome. Ideally, an EC line with a high proliferative capacity could be preestablished on the grafts, which could then be cryopreserved and made available as needed. The authors have seeded Dacron graft material with an immortalized human dermal microvascular EC line, HMEC-1. These cells were initially transfected with simian virus 40A large T antigen and have been passaged more than 100 times without signs of senescence. 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 coated with gelatin, was achieved in two weeks. The cells formed a monolayer over topographically elevated regions or appeared to be > one layer thick in other areas. Cells were also shown to remain viable after freezing. These results suggest a potential practical method for enhancement of small-caliber vascular graft biocompatibility in humans.