title: Effect of cryopreservation period on rat tracheal allografts.
abstract: BACKGROUND
  The effect of cryopreservation on tracheal allogenicity is still unclear. Therefore, in this study, we assessed the effect of cryopreservation period on tracheal allografts in 62 rats.
  
  
  METHODS
  Each transplant consisted of a 3-ring segment of the trachea harvested from 8 Lewis rats, immersed in preservation solution, and cryopreserved and stored in a Bicell biofreezing vessel in a deep freezer at -80 degrees C. Six tracheal grafts without cryopreservation that underwent a heterotopically syngeneic transplantation into the omentum served as controls. Forty-eight tracheal segments were randomly assigned to 8 groups according to period of cryopreservation, which ranged from 0 to 12 months (0, 0.5 [2 weeks], 1, 2, 3, 6, 9 and 12 months). The cryopreserved grafts were then thawed and heterotopically implanted into the omentum of recipient Brown-Norway rats. After 28 days, the tracheal segments were then evaluated histologically.
  
  
  RESULTS
  All isografts in Group 1 were intact, whereas the allografts undergoing a particularly shorter period of cryopreservation showed a more stenotic lumen. Prolonged periods of cryopreservation tended to show decreasing tendencies of viability of chondrocytes, mononuclear cell infiltration and sub-epithelial thickness, whereas all allografts showed a uniformly denuded epithelium, irrespective of the length of cryopreservation.
  
  
  CONCLUSIONS
  A longer period of cryopreservation may help to maintain a better patency of tracheal allografts by preventing an allogeneic response. Reduced tracheal allogenicity may be associated with a decreased viability of chondrocytes by cryopreservation.
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: R
authors.initials: R
authors.lastname: Nakanishi
authors.forename: M
authors.initials: M
authors.lastname: Hashimoto
authors.forename: H
authors.initials: H
authors.lastname: Muranaka
authors.forename: K
authors.initials: K
authors.lastname: Yasumoto
mesh_terms: D000818:Animals; D002356:Cartilage / Q000473:pathology / Q000637:transplantation; D002470:Cell Survival / Q000502:physiology; D015925:Cryopreservation / Q000379:methods*; D004195:Disease Models, Animal; D004848:Epithelium / Q000473:pathology / Q000637:transplantation; D008297:Male; D051381:Rats; D011914:Rats, Inbred BN; D011917:Rats, Inbred Lew; D014132:Trachea / Q000473:pathology* / Q000637:transplantation*; D014184:Transplantation, Homologous