Revascularization of canine cryopreserved tracheal allografts

Background. We examined the blood supply of a cryopreserved tracheal allograft and its morphohistologic changes after transplantation. Methods. In each of 22 dogs, a five-ring tracheal segment was replaced by one of the following tracheal grafts: fresh autografts (n = 8), cryopreserved tracheal allografts (n = 8), or fresh allografts (n = 6). The cryopreserved tracheal allografts were preserved at −196°C for 60 days. No immunosuppressant was given to any of the animals. All grafts were retrieved at 1 and 12 weeks and assessed by microangiography and histology. Results. The epithelial denudation and the revascularization of the transverse intercartilaginous arteries were recognized within 7 days as common to each of the three types of grafts. In the cryopreserved tracheal allografts, neither cartilage degradation nor graft shrinkage occurred at 7 days. However, the recanalized transverse intercartilaginous arteries completely disappeared at 12 weeks, and marked shrinkage occurred; the cartilage cells were accompanied by karyolysis and were significantly decreased in number (p < 0.05). Recanalization of the transverse intercartilaginous arteries was also demonstrated in the fresh allografts; however, necrosis abruptly occurred as a result of acute rejection responses. Conclusions. Cryopreservation of a tracheal allograft provided sufficient reduction of the acute rejection responses, and blood supply to the cryopreserved tracheal allograft was established through the recanalized transverse intercartilaginous arteries within 7 days; however, subsequent chronic rejection responses resulted in occlusion of the transverse intercartilaginous arteries and atrophy.