In vivo study of the effects of cryopreservation on heart valve xenotransplantation.
BACKGROUND
Recent reports have suggested that cryopreservation reduces the immunogenicity of donor tissue. The immunomodulation by cryopreservation might influence on the tissue durability after xenotransplantation. We investigated the in vivo morphologic changes in cryopreserved xenograft (CXG) heart valves.


METHODS
We transplanted a fresh (fresh xenograft; FXG) and a cryopreserved (CXG) porcine aortic root and a cryopreserved canine (cryopreserved allograft; CAG) aortic root into the abdominal aorta of a dog without any immunosuppressive agents. Explanted grafts on the 21st to 49th days after implantation were analyzed morphologically with light microscopy using some special stains, immunohistochemical analysis, and scanning electron microscopy (SEM).


RESULTS
Light microscopy showed the absence of smooth muscle cells in the media of the aorta in any group after transplantation. FXG valves did not maintain any cellularity after transplantation. CXG valves contained cellular infiltration in themselves. CAG valves contained numerous fibroblasts, which showed the maintenance of tissue integrity without allowing cellular infiltration. The structure of elastic fibers was well maintained, even in the part of CXG valve with cellular infiltration. Immunohistochemical studies documented the infiltration of T lymphocytes in CXG valves that were labeled by anti-CD3 antibodies. SEM demonstrated that no endothelia were seen on the surface of the valves in any group after transplantation.


CONCLUSIONS
We concluded that the cryopreservation method might provide an immunomodulation of xenogeneic heart valves for transplantation.
Nagasaka
Shigeo
S
Department of Thoracic and Cardiovascular Surgery, Nara Medical University School of Medicine, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan. nshige2002@msn.com
Taniguchi
Shigeki
S
Nakayama
Yoshio
Y
Sakaguchi
Hidehito
H
Nishizaki
Kazuhiko
K
Naito
Hiroshi
H
Morioka
Hiroyuki
H
D000818:Animals; D001012:Aorta, Abdominal / Q000601:surgery; D001021:Aortic Valve / Q000276:immunology / Q000473:pathology* / Q000637:transplantation*; D017252:CD3 Complex / Q000378:metabolism; D015925:Cryopreservation; D004285:Dogs; D004727:Endothelium / Q000648:ultrastructure; D006085:Graft Survival; D006350:Heart Valve Prosthesis; D008855:Microscopy, Electron, Scanning; D013194:Staining and Labeling; D013552:Swine; D013601:T-Lymphocytes / Q000378:metabolism / Q000473:pathology; D014183:Transplantation, Heterologous / Q000276:immunology / Q000473:pathology*
D017252:CD3 Complex