(644b) A Tissue-Engineered Stem Cell Bypass Graft (Invited)

Background: Autologous vascular tissue remains the gold standard conduit for bypass of diseased coronary and peripheral arteries, and for the creation of hemodialysis access. In the absence of this tissue, patients are offered bypass with prosthetic grafts which are far less durable and prone to infection. This presentation summarizes our efforts to produce a tissue-engineered bypass graft composed of decellularized vein allograft seeded with autologous adult stem cells differentiated into endothelial cells.

Methods: Decellularized venous allograft is created by removal all cellular elements from human cadaver saphenous vein using sodium dodecyl sulfate. The adult stem cells are isolated from human peri-umbilical fat (adipose-derived stem cells) and cultured in differentiating media for up to two weeks; further eNOS expression within the cells is induced by transfection using an adenoviral vector. Within a vascular bioreactor, the lumen of the decellularized scaffold is seeded with the stem cells and subsequently flow-conditioned (up to 9 dynes over 5d). These grafts have been implanted within the carotid artery of dogs or within the aorta of rabbits for up to two months.

Results: The decellularized venous allograft alone has burst and suture-holding strengths similar to non-decellularized vein. The residual extracellular matrix has preserved collagen and elastin, including basement membrane consisting of collagen type IV. In vivo, the decellularized allograft has reduced immunogenicity, repopulates with smooth muscle cell-like cells, but it lumen is lined with a dense layer of fibrin, similar to prosthetics. Following seeding of the allograft with autologous differentiated stem cells, we observed persistent thrombogenicity of the graft. Subsequent optimization of the graft creation process involving flow conditioning and eNOS transfection of the stem cells resulted in a non-thrombogenic luminal surface as well as reduced intimal hyperplasia.

Conclusions: Our efforts to create a tissue-engineered vascular graft using autologous adult stem cells have resulted in a graft that appears durable, non-immunogenic, non-thrombogenic and resistant to intimal hyperplasia. It is our intention to now translate this work to human clinical usage as a conduit for hemodialysis access.