EPITHELIAL REGENERATION AND PRESERVATION OF TRACHEAL CARTILAGE AFTER TRACHEAL REPLACEMENT WITH CRYOPRESERVED ALLOGRAFT IN THE RAT

Objective: We investigated the origin of the epithelium in transplante d cryopreserved tracheal allografts in rats and tried to clarify the m echanism by which immunogenicity is reduced in this procedure, Methods : Tracheal transplantation was performed with PVG rats (allele at the RT1 locus: c) used as donors and ACI rats (allele at the RT1 locus: a) as recipients. After resection of a 5-ring segment of the cervical tr achea of an ACI I at, the trachea was reconstructed with the cryoprese rved tracheal segment of a PVG rat (n = 6). No immunosuppressive agent s or steroids were given, Histologic changes were determined and immun ohistochemical staining was performed to investigate major histocompat ibility complex class I antigens of the transplanted tracheal segment. Results: Two months after tracheal transplantation, 6 surviving ACI r ats were killed. Histologically, the epithelium and tracheal cartilage of the transplanted cryopreserved segment displayed normal structure. Immunohistochemical staining showed that the major histocompatibility complex class I antigen of the ACI rat was expressed in the epitheliu m of the transplanted segment and that the class I antigen of the PVG rat was expressed in the cartilage of the transplanted segment. Conclu sions: After transplantation of the cryopreserved trachea, the epithel ium of the transplanted cryopreserved segment originated from the reci pient epithelium whereas the cartilage retained the structure of the d onor trachea. We hypothesize that transplantation of a cryopreserved t rachea leads to the growth of the recipient's epithelium over the dono r trachea, thereby reducing the antigenicity of the transplant.