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Background Transplantation of islets of Langerhans can restore insulin production in diabetic patients. Because of the shortage of human donor organs, transplantation of porcine islets may be an alternative solution. The present study was aimed at the characterization of rejection mechanisms of porcine islets transplanted into eight nondiabetic monkeys under the kidney capsule. Methods Cultured adult pig islets were used, which showed no expression of the galactose(alpha1,3)galactose epitope, major histocompatibility complex class II, or CD45, and no binding of antibodies or complement after exposure to monkey serum. Immunosuppression consisted of cyclophosphamide, cyclosporine A (CsA), and steroids (group 1); or antithymocyte globulin, anti-interleukin-2 receptor antibody, CsA, and steroids (group 2). In three animals of group 2, islets were also transplanted in the portal vein. Results Although all monkeys had preformed anti-pig antibodies, no correlation was found between antibody titers and rejection and no deposition of antibodies or complement was observed in the grafts. Group 1 showed islets up to day 11, followed by T-cell infiltration and rejection at approximately day 14. In group 2, two monkeys showed infiltrates consisting predominantly of T cells starting at approximately day 29, whereas two monkeys showed well-preserved islets without infiltration up to day 53. In the livers of the three monkeys that also received islets intraportally and were resectioned on days 21, 33, and 49, no islets could be detected. Conclusions This study demonstrates that cultured adult pig islets can survive in the monkey for more than 53 days without signs of rejection under standard immunosuppression.

The aims of this study were (1) to assess portal hemodynamics during intraportal hepatocyte transplantation (HTX) in dogs, (2) to evaluate a new method for the detection of transplanted hepatocytes using 5-bromo-2'-deoxyuridine (BrdU) incorporation, and (3) to determine the metabolic effects of HTX on an inborn error of the purine metabolism in dalmatian dogs. HTX was performed by intraportal infusion of freshly isolated allogeneic beagle hepatocytes. Portal flow and pressure were monitored continuously during HTX. For the detection experiments, beagles received hepatocytes that had been exposed to BrdU during regeneration of the donor liver, induced by partial hepatectomy. For metabolic studies, dalmatian dogs were used as recipients. Repetitive HTX was performed. As judged by the portal hemodynamics, the number of hepatocytes that could be infused safely varied from 5 x 10 8 to 8 x 10 8 in beagles, to 1 x 10 9 in dalmatians. Transaminase levels showed a 5- to 6-fold increase (P=0.05) after HTX, but normalized within 3 weeks. BrdU-positive cells were identified in the recipient livers 2 weeks after HTX and 5-10% of the total amount of transplanted hepatocytes was retrieved. A significant (P=0.05) decrease in serum uric acid was demonstrated after repeated HTX in dalmatians. In conclusion, (1) intraportal HTX is feasible, but portal hypertension limits the maximum amount of hepatocytes that can be infused in one HTX ; (2) BrdU labeling is an attractive method for the detection of transplanted hepatocytes in the recipient liver ; and (3) after two consecutive hepatocyte transplantations, a temporary correction of the purine metabolism was accomplished in the dalmatian dog.

Xenotransplantation of porcine islets of Langerhans is considered to be a possible alternative for clinical islet transplantation. However, porcine islet isolation procedures have been shown to produce highly variable yields between pigs with similar backgrounds. One of the variables that could account for this is the collagen substrate within the pancreas. We determined the amount and distribution of collagen within porcine pancreata as they determined islet isolation outcomes. This study involved the histological examination of 140 porcine pancreata (64 juvenile and 76 adult) and islet isolation from 58 adult organs. To quantify the amount of collagen, tissue samples were stained with Sirius Red. Collagen distribution was determined by assessing the presence of collagen in the endocrine-exocrine interface (the "islet capsule"), in tissue samples double-stained with Sirius Red and anti-insulin. Strong variation in total collagen was observed in both adult and juvenile pigs. The mean collagen content in the juvenile group was significantly lower than that in the adult group. Apparently, the pancreas undergoes a process of fibrosis as pigs age. The vast majority of islets from both adult and juvenile pancreata had no or only a limited collagen capsule. However, islet encapsulation was highly variable between pancreata. We observed no significant correlation between total collagen content or the percentage islet encapsulation and islet yield. Although total collagen content and islet encapsulation show great variability between pancreata, neither the amount nor the distribution of collagen affected porcine islet isolation outcome.

The aims of this study were (1) to assess portal hemodynamics during intraportal hepatocyte transplantation (HTX) in dogs, (2) to evaluate a new method for the detection of transplanted hepatocytes using 5-bromo-2'-deoxyuridine (BrdU) incorporation, and (3) to determine the metabolic effects of HTX on an inborn error of the purine metabolism in dalmatian dogs. HTX was performed by intraportal infusion of freshly isolated allogeneic beagle hepatocytes. Portal flow and pressure were monitored continuously during HTX. For the detection experiments, beagles received hepatocytes that had been exposed to BrdU during regeneration of the donor liver, induced by partial hepatectomy. For metabolic studies, dalmatian dogs were used as recipients. Repetitive HTX was performed. As judged by the portal hemodynamics, the number of hepatocytes that could be infused safely varied from 5 x 10(8) to 8 x 10(8) in beagles, to 1 x 10(9) in dalmatians. Transaminase levels showed a 5- to 6-fold increase (P=0.05) after HTX, but normalized within 3 weeks. BrdU-positive cells were identified in the recipient livers 2 weeks after HTX and 5-10% of the total amount of transplanted hepatocytes was retrieved. A significant (P=0.05) decrease in serum uric acid was demonstrated after repeated HTX in dalmatians. In conclusion, (1) intraportal HTX is feasible, but portal hypertension limits the maximum amount of hepatocytes that can be infused in one HTX; (2) BrdU labeling is an attractive method for the detection of transplanted hepatocytes in the recipient liver; and (3) after two consecutive hepatocyte transplantations, a temporary correction of the purine metabolism was accomplished in the dalmatian dog.

The present study was initiated to study the efficacy of donor pretreatment with interferon-gamma to induce class II antigen expression in heart tissue, and to investigate whether this pretreatment would influence heart allograft survival. BN rats were used as donors, and LEW rats as recipients. During a period of 3 consecutive days prior to transplantation, IFN-gamma was administered to BN rats via continuous intravenous infusion at dosages of 10(3), 10(4), and 5.10(4) U/hr. Control animals were infused with PBS; each group consisted of 9 animals. Analysis of IFN-gamma induced class II expression by immunoperoxidase staining revealed a significant, fourfold increase in the number of dendriticlike cells, irrespective of the IFN-gamma dose given (controls: 15 +/- 4 vs. highest dose group: 57 +/- 9 cells/mm2; P less than 0.005). Endothelial cells of arteries and venules remained class II antigen negative. Grafting of hearts from IFN-gamma perfused donors to untreated recipients (6 animals per group), did not result in a shortened or prolonged survival time in any of the experimental groups, as compared to controls. These results indicate that upgrading of class II antigen expression on dendriticlike cells is not likely to be of importance for the process of rejection.