Long-term cryopreservation can prevent rejection of canine tracheal allografts with preservation of graft viability.

We previously reported that cryopreservation of tracheas for 1 month was possible in a canine tracheal autotransplantation model with use of a preservative solution containing trehalose. Realizing that the allogenicity of many organs is decreased by freezing, we examined the possibility of immunosuppressant-free canine tracheal allotransplantation after long-term cryopreservation. Six to 10 rings of the trachea were removed from donor dogs (n = 12), immersed in the preservative solution, and cryopreserved in a deep freezer at -85 degrees C for 285 +/- 28 days (cryopreservation group). Five rings of the mediastinal trachea of recipient dogs were removed. The cryopreserved tracheas were thawed and transplanted to replace the excised mediastinal tracheas. In a control group (n = 6), the graft was preserved in Euro-Collins solution at 10 degrees C for 16 to 17 hours. Allotransplantation of tracheas was done as in the cryopreservation group. The anastomotic site and graft were covered with an omental pedicle in both groups. In the cryopreservation group, every animal, except one that was killed for pathologic examination, survived more than 2 months. All the grafts of this group were viable, and no stenosis or tracheomalacia was observed. In the control group, most of the animals died within 1 month of tracheal stenosis caused by rejection. These findings reveal that immunosuppressant-free canine tracheal allotransplantation was consistently possible after long-term cryopreservation of the graft in a preservative solution containing trehalose. This simple method could solve both donor shortage and immunosuppression problems.