Prolonged survival of murine thyroid allografts after 7 days of hyperbaric organ culture in the UW preservation solution at hypothermia.

Organ culture of murine thyroid allografts in hyperbaric oxygen (95% O2 at 25 psi, 37 degrees C) for 48 hr, results in prolonged allograft survival. Endocrine tissues can be cultured at 37 degrees C--however, this method may not be applicable to vascularized organs at normothermia. The aim of this study was to apply hyperbaric oxygen culture (HOC) under organ preservation conditions (hypothermia, UW solution) that have been shown to be successful in clinical organ transplantation. B10BR/SGSNJ murine thyroid lobes were transplanted beneath the kidney capsule of C57BL/10J recipients. Thyroids were cultured in Eagle's MEM at 37 degrees C (controls) and at 5 degrees C, under hyperbaric conditions (95% O2:5% CO2, 25 psi). Alternatively, thyroids were cultured in UW solution (+/- allopurinol/GSH) at 5 degrees C, for up to 7 days. Graft survival was determined 21 days posttransplant by 125I uptake and by histology. In Eagle's MEM, HOC at 37 degrees C/48 hr and 5 degrees C/7 days, resulted in 93% and 20% allograft survivals, respectively. In UW solution (- allopurinol/glutathione [GSH]), HOC at 5 degrees C/7 days resulted in 83% allograft survival: immunoperoxidase staining showed a decrease of MHC class I alloantigen expression. Oxygen free radical scavenger (allopurinol/GSH) addition to the UW solution diminished this effect and suggested an oxygen free radical-mediated mechanism in immunoalteration. These results demonstrate that HOC for 7 days reduced the antigenicity and immunogenicity of murine thyroid grafts under conditions that simulate organ preservation. Hypothermic hyperbaric oxygen culture conditions require testing in a higher animal species and in vascularized grafts to determine if this method can be applied to whole-organ transplantation.

Enhancement of thyroid allograft survival following organ culture. Alteration of tissue immunogenicity.

Hyperbaric oxygen (95%, O2, 25 psi, 48-hr culture) resulted in prolonged thyroid allograft (B10.A) survival in both primary and sensitized recipients (B10.AQR). Recipients receiving noncultured thyroid allografts uniformly rejected the graft by 35 days, while 100% of cultured grafts survived. Noncultured thyroid grafts transplanted to skin-graft-primed recipients were rejected by 21 days. In contrast, 86% of cultured grafts transplanted to primed recipients were still functioning at 35 days. Donor spleen cells or peritoneal exudate cells transferred at the time of thyroid transplant were unable to stimulate cultured allograft rejection. Allografts histologically examined 35 days after transplant revealed, in some grafts, focal cellular infiltrates adjacent to normal, uninfiltrated tissue. To determine if tissue modification was the mechanism of prolonged allograft survival, hyperbaric-oxygen-cultured thyroids were examined for MHC class I expression. Immunoperoxidase staining with monoclonal antibody to MHC class I molecules showed that cultured thyroids were unstained in contrast to fresh thyroids that were uniformly stained. Cytotoxic T lymphocytes specific for H-2Kk administered 10 days following thyroid transplant were unable to eliminate cultured grafts (80% survival) but completely destroyed noncultured grafts. These results indicate that hyperbaric oxygen culture altered MHC class I expression such that it was no longer detectable by monoclonal antibody or cytotoxic T lymphocytes. Thus, the mechanism, explaining graft prolongation after hyperbaric culture in addition to passenger cell depletion, may be alteration of graft antigenicity such that the graft is no longer perceived as foreign.