Cryopreservation of the Trachea Can Reduce Its Antigenicity in Various Species

Background: Cryopreserved tracheal allograft has been used successfully for esophageal replacement in the canine model. The working hypothesis was cryopreservation decreases antigenicity but epithelial desquamation remains. However, cryopreservation of human tracheal samples collected at tracheostomy, resulted in no significant desquamation. The aim of this study was to examine the extent of desquamation of the epithelial layer of cryopreserved animal tracheas and find a reason for decreased antigenicity of cryopreserved canine and pig’s trachea. Methods: 5 cm long tracheal segments were removed from 6 dogs and 125 pigs and stored in liquid nitrogen for 21 days. Cross section samples were taken from the end of the segment, 1 cm from the end and at the middle of the segment. Histological examination was performed using haematoxyllin-eosin and MHC-II antigen specific antibody staining. Changes in histological structure were analyzed. Results: General histological morphology of samples changed after cryopreservation. The percentage of intact epithelium and the overall intensity of immune-staining increased significantly from the ends to the middle of the segments, but the intensity of immune-staining showed no difference in the remaining epithelial cells. Conclusion: Cryopreservation damages the epithelial cells, but does not influence the cell’s antigenicity or cause desepithelisation. The main effect is a retraction of the epithelial layer from the ends to the midpart and this effect may be protection against organ rejection. Based on our canine and pig results a 5 cm, long tracheal segment seems to be a promising organ for human esophageal replacement.