Successful allotransplantation of cryopreserved tracheal grafts with preservation of the pars membranacea in nonhuman primates

Objective: This study was performed to confirm the feasibility of cryopreserved tracheal allotransplantation in primates, the anatomy and immunology of which are considered to be more closely related to those of humans than those of other animals. Methods: Cryopreserved tracheal allotransplantations were performed in 3 recipient primates. In the control group fresh tracheal allotransplantations were performed in 2 primates (control A), and a tracheal allotransplantation with a simply frozen tracheal graft was performed in 1 primate (control B). Monthly bronchoscopic examinations, histologic examinations, electron microscopic examinations, and immunohistochemical investigations were performed in each of the primates. Results: In the cryopreserved tracheal allotransplantation group, 3 recipient monkeys were killed on the 35th, 144th, and 387th postoperative days, respectively. All grafts were incorporated by the recipient trachea without stenosis in the cryopreserved group. In the control group 2 recipient monkeys were killed on the 93rd postoperative day (control A), and one was killed on the 84th postoperative day (control B). Severe stenosis was observed after the transplantation in all of the control monkeys. Immunologic reactions appeared to be attenuated by the cryopreservation, whereas T cell-mediated immunologic rejection (control A) and loss of cartilage viability (control B) were considered to be the causes of graft failure in the control group. Conclusion: The immunogenicity of the tracheal allografts was reduced by cryopreservation, and cryopreserved tracheal allotransplantation was successful in our primate model. Further investigation of cryopreserved tracheal allotransplantation with regard to proper clinical applications and the limitations of the procedure should be performed.