Evaluation of Antigenicity of Components of Tracheal Allotransplant and Effect of Immunosuppressant Regime in a Rodent Model.

Tracheal transplantation seems to be the logical step in the process of reconstruction of the trachea following a long-segment resection, which is usually done to treat malignant disease or benign stenosis of the airway caused by a traumatic, congenital, inflammatory, or iatrogenic lesion. Immunosuppression following transplant is essential but not ideal after oncoresection.  The tracheal allografts, harvested from Sprague Dawley rats, were implanted in the Wistar strain rat. The harvested tracheal grafts were divided into groups and subgroups, based on the layers of trachea, method of decellularization, and immunosuppression. The antigenicity of different layers of trachea and the effect of various decellularization methods were studied within three time frames, that is, day 3, 9, and 15.  On structural analysis, the day 3 and day 15 samples showed no meaningful comparison could be made, due to extensive neutrophil infiltration in all three layers. The day 9 tracheal grafts showed loss of epithelium, with no signs of regeneration in most of the allografts. The subepithelial lymphoid infiltration was found to be severe in nonimmunosuppressed allografts. The group in which both inner and outer layers were removed showed moderate-to-severe infiltrate of lymphoid cells in all the allografts, but there was no cartilage loss, irrespective of the method of decellularization. The irradiated specimens retained the cartilage but showed extensive ischemic damage.  Rat trachea is a good model for tracheal transplant research but not adequately sturdy to sustain mechanical debridement. Irradiation and chemical decellularization eliminates the immune response but causes intense ischemic damage. Out of the three time frames, day 9 seemed to be the best to study the immune response. To substantiate the results obtained in this study, the immunohistochemical study of the allografts is needed to be performed among a larger group of animals.