Pig-to-monkey islet xenotransplantation using multi-transgenic pigs.

The generation of pigs with genetic modifications has significantly advanced the field of xenotransplantation. New genetically engineered pigs were produced on an α1,3-galactosyltransferase gene-knockout background with ubiquitous expression of human CD46, with islet beta cell-specific expression of human tissue factor pathway inhibitor and/or human CD39 and/or porcine CTLA4-lg. Isolated islets from pigs with 3, 4 or 5 genetic modifications were transplanted intraportally into streptozotocin-diabetic, immunosuppressed cynomolgus monkeys (n = 5). Immunosuppression was based on anti-CD154 mAb costimulation blockade. Monitoring included features of early islet destruction, glycemia, exogenous insulin requirement and histopathology of the islets at necropsy. Using these modified pig islets, there was evidence of reduced islet destruction in the first hours after transplantation, compared with two series of historical controls that received identical therapy but were transplanted with islets from pigs with either no or only one genetic modification. Despite encouraging effects on early islet loss, these multi-transgenic islet grafts did not demonstrate consistency in regard to long-term success, with only two of five demonstrating function beyond 5 months.

Ex vivo application of carbon monoxide in UW solution prevents transplant-induced renal ischemia/reperfusion injury in pigs.

I/R injury is a major deleterious factor of successful kidney transplantation (KTx). Carbon monoxide (CO) is an endogenous gaseous regulatory molecule, and exogenously delivered CO in low concentrations provides potent cytoprotection. This study evaluated efficacies of CO exposure to excised kidney grafts to inhibit I/R injury in the pig KTx model. Porcine kidneys were stored for 48 h in control UW or UW supplemented with CO (CO-UW) and autotransplanted in a 14-day follow-up study. In the control UW group, animal survival was 80% (4/5) with peak serum creatinine levels of 12.0 +/- 5.1 mg/dL. CO-UW showed potent protection, and peak creatinine levels were reduced to 6.9 +/- 1.4 mg/dL with 100% (5/5) survival without any noticeable adverse event or abnormal COHb value. Control grafts at 14 days showed significant tubular damages, focal fibrotic changes and numerous infiltrates. The CO-UW group showed significantly less severe histopathological changes with less TGF-beta and p-Smad3 expression. Grafts in CO-UW also showed significantly lower early mRNA levels for proinflammatory cytokines and less lipid peroxidation. CO in UW provides significant protection against renal I/R injury in the porcine KTx model. Ex vivo exposure of kidney grafts to CO during cold storage may therefore be a safe strategy to reduce I/R injury.

Systemic chimerism in human female recipients of male livers.

We have previously reported data from clinical and laboratory animal observations which suggest that organ tolerance after transplantation depends on a state of balanced lymphodendritic cell chimerism between the host and donor graft. We have sought further evidence to support this hypothesis by investigating HLA-mismatched liver allograft recipients. 9 of 9 female recipients of livers from male donors had chimerism in their allografts and extrahepatic tissues, according to in-situ hybridisation and molecular techniques 10 to 19 years posttransplantation. In 8 women with good graft function, evidence of the Y chromosome was found in the blood (6/8), skin (8/8), and lymph nodes (7/8). A ninth patient whose transplant failed after 12 years from recurrent chronic viral hepatitis had chimerism in her lymph nodes, skin, jejunum, and aorta at the time of retransplantation. Although cell migration is thought to take place after all types of transplantation, the large population of migratory cells in, and the extent of their seeding from, hepatic grafts may explain the privileged tolerogenicity of the liver compared with other organs.

Long survival in rats after multivisceral versus isolated small-bowel allotransplantation under FK 506.

Abdominal multivisceral allotransplantation (MVTX) from Brown Norway donor rats to Lewis recipient rats was performed under a 14-day course of low (0.32 mg/kg) or high-dose (0.64 mg/kg) intramuscular FK 506 to which weekly further injections were added in some of the high-dose animals. With all three regimens, long survival was frequently achieved with good intestinal adsorption and weight gain, but histopathologic evidence of intestinal rejection existed in the most lightly treated animals. The liver, stomach, and pancreas had only minor abnormalities. Rejection of isolated intestinal grafts was more difficult to control based on histopathologic criteria, and satisfactory results were obtained only with the most aggressive treatment protocol, suggesting that the liver in the MVTX had provided an advantage to the companion organs of the graft, of which the intestine was most vulnerable. Histopathologically, the lymphoid elements of the intestine, including the Peyer's patches, appeared to be the most immunogenic component of the intestine. Epithelium near lymphoid areas was secondarily involved with villous atrophy, cryptitis, and abscess formation. Beginning within 12 days in successful MVTX experiments, the lymphoreticular components of the graft intestine, including the Peyer's patches, lamina propria, and mesenteric nodes, were shown with anti-Ia monoclonal antibodies to be repopulated with recipient cells. This finding in grafts that appeared to be permanently accepted was surprising and contrary to expectations from the literature on intestinal allotransplantation.

Rejection of multivisceral allografts in rats: a sequential analysis with comparison to isolated orthotopic small-bowel and liver grafts.

Multivisceral isografts and allografts were transplanted to Lewis rats, and the histopathologic changes were studied in the liver, intestine, and other constituent organs. Rats receiving isografts had indefinite survival with maintenance of weight. With multivisceral allografts (from Brown-Norway donors), the intestinal component was rejected more severely than the companion liver and with about the same severity as when intestinal transplantation was performed alone. Intestinal rejection in either circumstance was a lethal event, causing death in 10 to 12 days. The earliest (by day 4) and most intense cellular rejection was in the Peyer's patches and mesenteric lymph nodes. This was associated with or followed by cryptitis, epithelial cell necrosis, focal abscess formation, mural necrosis, and eventual perforation. Liver allografts transplanted alone or as part of multivisceral grafts also had histopathologic evidence of rejection, but this was self-limiting and spontaneously reversible when the liver was transplanted alone. Thus the Achille's heel of multivisceral grafts is the intestinal component that is not protected by the presence of the liver in the organ complex. Better immunosuppression should permit successful experimental and clinical transplantation of such grafts.

Heterotopic heart transplantation in the rat receiving FK-506 alone or with cyclosporine.

In rats, FK significantly prolonged heterotopic heart graft survival over a wide dose range when given for 2 weeks starting on the day of the operation. Brief courses of FK for one to four days preoperatively, and especially beginning four days postoperatively, allowed long subsequent survival of heart grafts in otherwise untreated recipients. The seeming acceptance of the grafts with postoperative FK treatment was largely but not exclusively donor specific when tested eight days after the last FK dose by second grafts from the same donor v third-party donor grafts. FK in minimally therapeutic doses was synergistic with suboptimal doses of CyA.