Effects of cryopreservation on the immunogenicity of porcine arterial allografts in early stages of transplant vasculopathy

Background: The number of revascularization procedures including coronary and lower extremity bypass, have increased greatly in the last decade. It suggests a growing need for vascular grafts. Cryopreserved allografts could represent a viable alternative but their immunologic reactivity remains controversial. Methods: 71 pigs (40 recipients and 31 donors) were used. Two femoral grafts per recipient animal were implanted for 3, 7, and 30 days. Types of grafts: fresh autograft as a control graft (n = 19), fresh allograft (n = 31) and cryopreserved allograft (n = 30). Histological and immunohistochemical studies were performed. Results: Fresh allografts compared to autografts showed intimal inflammatory infiltration at 3 days (328 vs. 0 macrophages/mm 2; P < 0.05) and 7 days (962 vs. 139 T lymphocytes/mm2; P < 0.05) post-transplantation. At 30 days, there was a loss of endothelial cells, presence of luminal thrombus and aneurismal lesions (total area = 15.8 vs. 8.4 mm2; P < 0.05). Cryopreservation did not reduce these lesions nor modify endothelial nitric oxide synthase (eNOS) expression nor modify the number of animals that developed anti-SLA antibodies. Moreover, at 7 days, cryopreserved allografts compared to fresh allografts showed a higher expression of P-selectin (5 out of 5 vs. 1 out of 5; P < 0.05) and, at 30 days, a greater inflammatory reactivity (2692 vs. 1107 T lymphocytes/mm 2 in media; P < 0.05) with a trend towards a higher presence of multinucleated giant cells than in the fresh ones. Conclusions: The cryopreservation method used maintained immunogenicity of allografts and increased the inflammatory reactivity found in fresh allografts up to 30 days of vascular transplantation. © 2005 Elsevier Inc. All rights reserved.