Autologous or synthetic vascular grafts are used routinely for providing access in hemodialysis or for arterial bypass in patients with cardiovascular disease. However, some patients either lack suitable autologous tissue or cannot receive synthetic grafts. Such patients could benefit from a vascular graft produced by tissue engineering. Here, we engineer vascular grafts using human allogeneic or canine smooth muscle cells grown on a tubular polyglycolic acid scaffold. Cellular material was removed with detergents to render the grafts nonimmunogenic. Mechanical properties of the human vascular grafts were similar to native human blood vessels, and the grafts could withstand long-term storage at 4 °C. Human engineered grafts were tested in a baboon model of arteriovenous access for hemodialysis. Canine grafts were tested in a dog model of peripheral and coronary artery bypass. Grafts demonstrated excellent patency and resisted dilatation, calcification, and intimal hyperplasia. Such tissue-engineered vascular grafts may provide a readily available option for patients without suitable autologous tissue or for those who are not candidates for synthetic grafts.

Arterial tissue-engineering techniques that have been reported previously typically involve long waiting times of several months while cells from the recipient are cultured to create the engineered vessel. In this study, we developed a different approach to arterial tissue engineering that can substantially reduce the waiting time for a graft. Tissue-engineered vessels (TEVs) were grown from banked porcine smooth muscle cells that were allogeneic to the intended recipient, using a biomimetic perfusion system. The engineered vessels were then decellularized, leaving behind the mechanically robust extracellular matrix of the graft wall. The acellular grafts were then seeded with cells that were derived from the intended recipient-either endothelial progenitor cells (EPC) or endothelial cell (EC)-on the graft lumen. TEV were then implanted as end-toside grafts in the porcine carotid artery, which is a rigorous testbed due to its tendency for graft occlusion. The EPC-and EC-seeded TEV all remained patent for 30 d in this study, whereas the contralateral control vein grafts were patent in only 3/8 implants. Going along with the improved patency, the cell-seeded TEV demonstrated less neointimal hyperplasia and fewer proliferating cells than did the vein grafts. Proteins in the mammalian target of rapamycin signaling pathway tended to be decreased in TEV compared with vein grafts, implicating this pathway in the TEV's resistance to occlusion from intimal hyperplasia. These results indicate that a readily available, decellularized tissue-engineered vessel can be seeded with autologous endothelial progenitor cells to provide a biological vascular graft that resists both clotting and intimal hyperplasia. In addition, these results show that engineered connective tissues can be grown from banked cells, rendered acellular, and then used for tissue regeneration in vivo.bypass graft | collagen | mechanical conditioning

The results demonstrate a superior treatment effect for control of bleeding using human thrombin compared to a saline solution. Future studies should compare bovine thrombin versus human thrombins ability to control bleeding as well as the hazard of each in activating coagulation inhibitors.

Standard neoadjuvant therapy significantly decreases the number of lymph nodes retrieved following proctectomy for patients with rectal cancers. Quality initiatives or performance measures evaluating lymph node harvest following proctectomy should reflect the use of preoperative chemoradiation.

These results demonstrate that the adventitial application of endothelial implants significantly reduced MMP-2 expression within the venous wall, and increased venous lumen diameter and positive remodeling in a porcine arteriovenous graft model. Adventitial endothelial implants may be useful in decreasing luminal narrowing in a clinical setting.

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