title: The immunomodulatory effect of cryopreservation in rat tracheal allotransplantation.
abstract: BACKGROUND
  Cryopreservation is one solution to the problem of donor organ deficit. To investigate the effect of cryopreservation on tracheal allografts, we performed 2 experiments in rats.
  
  
  METHODS
  In Experiment 1, we assessed second-set graft rejection. Two weeks after primary heterotopic transplantation (Group 1, fresh isografts; Group 2, fresh allografts from Lewis rats; and Group 3, cryopreserved allografts from Lewis rats; n = 5, respectively), each animal underwent secondary heterotopic grafting with isografts and allografts from Lewis and Wistar Furth rats (n = 5, respectively). Four weeks after the secondary transplantation, all grafts were retrieved for histologic analysis. In Experiment 2, we assessed the long-term results of allograft cryopreservation, without immunosuppression therapy. Six months after transplantation of fresh (Group 4) and cryopreserved (Group 5) allografts, the tracheal segments (each group, n = 5) were histologically evaluated.
  
  
  RESULTS
  In Experiment 1, only the secondary allografts from Lewis rats in Group 2 did not maintain lumen structure and often showed dislocated or destroyed cartilage. Second-set graft rejection was specifically recognized in Group 2, but not in Group 1 or 3. In Experiment 2, the cryopreserved allografts appeared almost normal and lumen rigidity was preserved 6 months after transplantation. These allografts were superior to the fresh allografts in patency and in cartilage dislocation and mononuclear cell infiltration scores, but not in the viable chondrocyte ratio.
  
  
  CONCLUSIONS
  We conclude that cryopreservation may produce successful long-term results because of its immunomodulatory effect on tracheal allografts.
authors.affiliation: Second Department of Surgery, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan. ryoichi@med.uoeh-u.ac.jp
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Nakanishi
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Onitsuka
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Shigematsu
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Muranaka
authors.forename: Kosei
authors.initials: K
authors.lastname: Yasumoto
mesh_terms: D000818:Animals; D015925:Cryopreservation; D006084:Graft Rejection; D008297:Male; D051381:Rats; D011914:Rats, Inbred BN; D011917:Rats, Inbred Lew; D011920:Rats, Inbred WF; D014132:Trachea / Q000637:transplantation*; D014181:Transplantation Immunology; D014184:Transplantation, Homologous