Tracheal Replacement with Fresh and Cryopreserved Aortic Allograft in Adult Dog

Background Many reports have described tracheal replacement using aortic allografts, with varying results and minimal understanding of the mechanism of tracheal regeneration. The present study attempted tracheal regeneration in adult dogs using fresh aortic allografts (FAA) and cryopreserved aortic allografts (CAA). Materials and Methods Twelve adult beagles underwent tracheal resection and were transplanted with FAA ( n = 5) or CAA ( n = 7). Animals were followed-up with serial radiography and magnetic resonance imaging, and were euthanized at predetermined times up to 16 mo post-surgery. Results There were no procedural deaths, but two animals died due to stent migration. Stent migration occurred in seven of the 12 animals. Evidence of regeneration of tracheal epithelium was observed in the surviving animals, with the transformation of squamous metaplasia to mucociliary epithelium being time-dependent. Islet of cartilage were observed in animals after 6 mo, but ring-like cartilage structures were absent, even after 16 mo. During autopsy, axial graft contractions up to 68% were observed. Serial radiographs show that most of the contraction occurred within 1 mo. The results of the MRI showed that the graft area was strongly enhanced for up to 2 mo, but was clearly reduced after 3 mo. Conclusions Tracheal replacement in adult dogs using FAA or CAA is feasible. However, immaturity of the neotracheal cartilage did not allow the tissue to function as native tracheal tissue. Prolonged stenting should be considered in adult if the procedure is to be clinically contemplated.