Arterio-Venous fistulate grafts (AVG) fail in humans because of thrombogenicity of the flow surface and the development of cellular hyperplasia. Our previous studies have concentrated on altering graft thrombogenicity by transplanting autologous fat-derived microvessel endothelial cells (MVEC) onto the luminal surface of polymeric grafts. We have observed that MVEC transplantation or 'sodding' results in the accelerated formation of an antithrombogenic cellular lining on polymeric grafts used in arterial bypass surgery. We also have observed a statistically significant improvement in MVEC sodded arterial bypass graft patency in animal studies and have begun to use this technology in human clinical trials. The evaluation of MVEC sodding technology in AV fistulae grafts represents a logical extension of our work. The maintenance of AVG patency in the american population represents a significant healthcare cost. Accordingly, an understanding of the mechanisms resulting in AVG failure, and development of a process to prolong AVG patency will have immediate human benefits. To this end we propose to test four hypotheses addressing MVEC sodding to AVG in a canine model. This hypothesis testing will provide answers to the following questions: 1. Does MVEC sodding of AVG improve patency. 2. Does the density of cells transplanted, cell type and methods of cell deposition affect the rate of formation of an antithrombogenic lining and subsequent graft patency? 3. Does MVEC sodding affect the development of intimal hyperplasia? 4. Is their a temporal sequence of cellular proliferation occurring in intimal hyperplasia? Is this sequence affected by MVEC sodding? To address these questions we will use a canine A-V fistula model and cellular and molecular methodology to evaluate hyperplasia and growth factor expression. Expanded PTFE grafts will be treated with autologous MVEC isolated from falciform ligament fat. First phase studies will evaluate the effects of MVEC sodding on AVG patency. Subsequent studies will evaluate the effects of cell density, and the types of cells used for sodding (EC vs smooth muscle cells) on the development of a neointima. Grafts will be explained and evaluated immediately by morphologic, and molecular biologic techniques. Rings of vascular grafts will also be placed in organ culture and the cellular proliferation in the intima as well as growth factor expression will be quantified. The second phase studies will evaluate the development of the neointima by explanting grafts during periods ranging from 48 hours to 26 weeks. Through these experiments we propose to determine how MVEC sodding influences the development of an antithrombogenic neointima and whether the chronic hyperplasia observed clinically with AV access grafts is affected by MVEC sodding technology.
