Tracheal replacement with cryopreserved tracheal allograft: experiment in dogs

Background. It has been difficult to perform tracheal allotransplantation without immunosuppression. To determine whether cryopreserved trachea can be used in tracheal replacement, we evaluated the viability of cryopreserved tracheal allografts in a canine model of immunosuppressant-free transplantation. Methods. Cryopreserved tracheal allografts, which had been frozen to −80°C in a programmed freezer and then stored in liquid nitrogen (−196°C) (group 1, n = 6), fresh tracheal autografts (group 2, n = 5), and fresh tracheal allografts (group 3, n = 4) were transplanted into the thoracic segment of the trachea using an omental flap without immunosuppressive agents. Results. All dogs in groups 1 and 2 survived, but in group 3, all 4 died of airway obstruction between 1 month and 2 months after operation. Histologically, the cryopreserved allografts displayed normal epithelium and cartilage, but the fresh allografts showed chronic inflammatory changes, no epithelium, and no cartilage. Conclusions. Cryopreserved tracheal allografts maintain their structural integrity after transplantation. The cryopreservation process seems to reduce the allogenic response of the trachea in canine models. Therefore, we believe the cryopreserved tracheal allograft is an excellent choice for tracheal replacement.