title: In vivo study of the effects of cryopreservation on heart valve xenotransplantation.
abstract: 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.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Nara Medical University School of Medicine, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan. nshige2002@msn.com
authors.forename: Shigeo
authors.initials: S
authors.lastname: Nagasaka
authors.forename: Shigeki
authors.initials: S
authors.lastname: Taniguchi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Nakayama
authors.forename: Hidehito
authors.initials: H
authors.lastname: Sakaguchi
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nishizaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Naito
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Morioka
mesh_terms: 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*
chemical_list: D017252:CD3 Complex