Influence of cold ischemia time, pretransplant anti-porcine antibodies, and donor/recipient size matching on hyperacute graft rejection after discordant porcine to cynomolgus kidney transplantation

Comparison between slow and rapid freezing for adrenal gland cryopreservation and xenotransplantation

The aim of our study was to examine whether slow or rapid cryopreservation of adrenal xenografts affected xenotransplant outcome. Adrenal xenografts were got from newborn piglets (<24 h after birth). Receptor rats were randomly divided into four groups: a bilateral adrenalectomy group, fresh xenotransplantation group, rapid cryopreservation xenotransplantation group, and a slow cryopreservation xenotransplantation group. 30 days after xenotransplantation, the survival rates of rats in the fresh xenotransplantation group, rapid cryopreservation xenotransplantation group and slow cryopreservation xenotransplantation group were 80 %, 60 % and 60 %, respectively, which were significantly higher than 40 % of the bilateral adrenalectomy group. In addition, the survival rate of rats in the slow cryopreservation group was consistently significantly higher than that in the rapid cryopreservation group at 29 days after xenotransplantation. Morphological observation showed that there were a few medulla cells existed in the adrenal glands in the slow cryopreservation group after 30 days of xenotransplantation, but no medulla cells were found in the rapid cryopreservation group. The plasma cortisol level of rats in the fresh xenotransplantation group and the slow xenotransplantation group 30 days after xenotransplantation was significantly higher than that of the rapid cryopreservation group and bilateral adrenalectomy group (P < 0.05). The levels of liver glycogen and cholesterol in the xenotransplantation rats were increased relative to those of the bilateral adrenalectomy rats, and close to normal level. In conclusion, compared with rapidly frozen preserved grafts, slowly frozen preserved grafts not only ensure the structural integrity of adrenal tissues, but also have corresponding physiological functions, which provid a basic research opportunities for the preservation of xenografts and the treatment of adrenal corticosteroid deficiency. Moreover, these findings can provide evidence for xenotransplantation in the treatment of Addison's disease (adrenal cortex hormone deficiency).

Progress in pig-to-non-human primate transplantation models (1998-2013): a comprehensive review of the literature

BACKGROUND

The pig-to-non-human primate model is the standard choice for in vivo studies of organ and cell xenotransplantation. In 1998, Lambrigts and his colleagues surveyed the entire world literature and reported all experimental studies in this model. With the increasing number of genetically engineered pigs that have become available during the past few years, this model is being utilized ever more frequently.

METHODS

We have now reviewed the literature again and have compiled the data we have been able to find for the period January 1, 1998 to December 31, 2013, a period of 16 yr.

RESULTS

The data are presented for transplants of the heart (heterotopic and orthotopic), kidney, liver, lung, islets, neuronal cells, hepatocytes, corneas, artery patches, and skin. Heart, kidney, and, particularly, islet xenograft survival have increased significantly since 1998.

DISCUSSION

The reasons for this are briefly discussed. A comment on the limitations of the model has been made, particularly with regard to those that will affect progression of xenotransplantation toward the clinic.

Appropriate donor size for porcine liver xenotransplant

OBJECTIVES

Owing to an imbalance between demand and supply, which is more prominent in pediatric transplant, every year more patients lose their lives on waiting lists. In addition to the use of deceased-donor split and living-donor organs, xenotransplant could provide a solution if associated problems, such as immunologic and physiologic ones, are solved. This study sought to analyze the surgical aspects for liver xenotransplant in a porcine model.

MATERIALS AND METHODS

Landrace pigs (n=22, 23 to 37 kg) underwent a laparotomy under general anesthesia. The hepatic hilum was prepared and the common bile ducts, common hepatic artery, portal vein, supra- and infrahepatic inferior vena cava were identified. The length and diameter of each vessel and bile duct and the weight of the liver were measured.

RESULTS

Pearson tests showed a clear correlation between the increase of the pigs' weight and the livers' weight, and the length of the vessels and the bile ducts. We did not find a clear correlation between the increase of the pigs' liver weight and the diameters of the vessels and the bile duct.

CONCLUSIONS

As the first reporting, this study on xenotransplants from the surgical point of view, we postulate that it could be possible to estimate the size of the liver and the proper length of its vessels and bile duct by weighing only the pigs. It was not feasible to match the diameter of mentioned structures by the livers' weight. However, the weight of pig's liver as well as vascular anatomy of pigs appeared to be suitable alternative for the human liver.

Singlet oxygen energy illumination during moderate cold ischemia prolongs the survival of concordant hamster xeno-heart transplants

INTRODUCTION

Singlet oxygen energy (SOE) is a potent inhibitor of reactive oxygen species (ROS) in vitro and in vivo in certain dose ranges and can improve the levels of high-energy phosphates (HEP) in concordant hamster xeno-heart transplants. Some data indicate that a certain degree of cold ischemia (CI) might be beneficial to xenotransplants. We investigated if SOE illumination of hamster xeno-hearts during moderate cold ischemia (CI) improved graft survival.

MATERIALS AND METHODS

Eighteen hearts from Golden Syrian hamsters (70 to 80 g) were subjected to 8 hours of CI in cold (+4 degrees C) saline solution (NaCL, 0.9%) before heterotopic cervical transplantation to Lewis rats (220 g). Among the treatment group (n = 8), SOE was produced by illuminating the hearts for 10 minutes every 30 minutes with photons at lambda 634 nm with the Oxylight equipment. Graft function was evaluated every 6 hours after transplantation with digital exam until cessation of heart beats.

RESULTS

The graft survival of SOE-illuminated ischemic hamster xenografts was 2.34 +/- 0.56 versus 1.15 +/- 0.37 days in the control group (P < .05). All hearts displayed immediate graft function versus 70% in the controls (NS).

CONCLUSIONS

SOE illumination at lambda 634 nm during moderate cold ischemia (+4 degrees C) can improve the survival of concordant hamster xeno-heart transplants. The exact mechanism(s) are currently unknown, but the effect might in part be exerted by a combination of reduced production of ROS and increased oxidative phosphorylation.

Hyperacute rejection of hDAF-transgenic pig organ xenografts in cynomolgus monkeys: influence of pre-existing anti-pig antibodies and prevention by the alphaGAL glycoconjugate GAS914

BACKGROUND

Our introductory pig-to-cynomolgus monkey heart or kidney transplantation using organs from pigs transgenic for human decay-accelerating factor (hDAF), showed a high incidence of hyperacute rejection (HAR), which was ascribed to extraordinary high levels of anti-pig antibodies. We evaluated the efficacy of GAS914, a Gal alpha 1-3Gal trisaccharide linked to a poly-l-lysine backbone, in inhibition of HAR.

METHODS

hDAF transgenic heterotopic heart (n = 15) or life-supporting kidney (n = 8) transplantation included induction with cyclophosphamide or anti-thymocyte globulin, and maintenance with cyclosporine or tacrolimus, steroids and mycophenolate sodium/mofetil. Four doses of GAS914 were given before transplantation. Rejection was confirmed by graft histology, and anti-pig antibody levels were determined in various assays.

RESULTS

Four of six heart transplants without GAS914 treatment showed HAR. Nine subsequent transplants with GAS914 pre-treatment, did not show HAR (chi-square, P < 0.05). Two of four kidney transplants without GAS914 treatment ended with HAR. Four subsequent transplants with GAS914 did not show HAR. Animals with HAR showed extremely high antibody levels. Samples just before transplantation showed significantly higher antibody levels in recipients presenting with HAR. In all assays antibody levels were significantly lowered by GAS914 pre-treatment.

CONCLUSIONS

HAR of hDAF solid organs could be ascribed to high levels of anti-pig antibodies. It is hypothesized that the hDAF transgene shows a threshold in efficacy, above which an overwhelming attack by antibodies and complement activation cannot be modulated to prevent HAR. HAR does not occur when animals with lower levels are used, or when antibodies are effectively depleted from the circulation by GAS914 treatment.

Xenotransplantation: a tool for reproductive biology and animal conservation?

The transplantation of reproductive organs, including ovaries and ovarian tissue, was pioneered over 100 years ago. In the 1960s, ovarian grafting was used as a tool to investigate ovarian function, but with the recent development of more effective cryopreservation protocols for ovarian tissue, germline preservation and propagation have now become realistic goals. This review describes progress in ovarian banking and ovarian tissue transplantation, with emphasis on how fresh and frozen ovarian tissue can be used in assisted reproduction for both humans and animals. This paper focuses most closely on the potential value of xenotransplantation, the transplantation of gonads from one species to another, to conserve rare and endangered species. Specific attention is drawn to the use of xenotransplantation as a strategy for generating viable gametes that can be used to produce live fertile offspring. Other upcoming xenogeneic technologies that may be of potential significance in animal conservation, such as transplantation of whole ovaries or isolated growing follicles, and even male germ cells, are discussed.

Ex vivo and extracorporeal perfusion with hDAF pig kidneys

The present study was undertaken to determine whether human decay accelerating factor (hDAF) transgene would prevent hyperacute rejection (HAR) while perfused with human blood or extracorporeally in baboons. Four hDAF pig kidneys and three non-hDAF pig kidneys were perfused ex vivo with fresh human blood for 6 h. Additionally four hDAF pig kidneys and four non-hDAF pig kidneys were extracorporeally perfused in baboons and pigs, respectively, for 3 h. In ex vivo perfusion, the color of hDAF pig kidneys remained pink at the end of 6-h perfusion and they had normal histology, while non-hDAF kidneys developed HAR. HDAF pig kidneys had superior function over non-transgenic pig kidneys. Urine output was 17.31 +/- 3.70 ml/h for hDAF pig kidneys, and only 5.81 +/- 0.26 ml/h for non-hDAF kidneys (P < 0.05). Creatinine clearance was 1.16 +/- 1.24 ml/min for hDAF kidneys and 0.22 +/- 0.15 ml/min for non-hDAF kidneys (P < 0.05). Other functional data including potassium, urine specific density, and osmolality were normal in the hDAF kidneys, while in non-hDAF kidneys, serum potassium was elevated to over 9 mmol/l by the end of perfusion (P < 0.01). Non-hDAF kidneys also lost more sodium through urine than hDAF kidneys (173.67 +/- 14.05 mmol/l vs. 109 +/- 31 mmol/l, P < 0.05). In the extracorporeal perfusion, all the baboons tolerated the procedure well with normal hemodynamic and hemotologic profiles. These baboons were well until killed 42 to 56 days after perfusion, although their antiporcine antibodies were greatly elevated. We conclude that hDAF transgene protects against HAR, allowing the pig kidney to function normally while perfused with human blood, and that extracorporeal perfusion using hDAF pig kidneys is a safe procedure in baboons.

The production of transgenic pigs for potential use in clinical xenotransplantation: baseline clinical pathology and organ size studies

This report describes the results of hematology, serum biochemistry, growth, and organ weight studies undertaken on pigs from nine cohorts of qualified pathogen free (QPF) pigs reared within a high welfare bioexclusion facility as potential organ source animals. Confirmation of the high health status of the pigs was given through total leukocyte counts and serum globulin concentrations that fell below the expected reference range for conventional pigs. The calculated mean growth rate for QPF pigs was found to exceed target rates set for optimum genotype commercial pig herds. Body weights of QPF pigs were compared with kidney, heart and liver weights at necropsy.

C1-inhibitor for prophylaxis of xenograft rejection after pig to cynomolgus monkey kidney transplantation

BACKGROUND

Early rejection of discordant porcine xenografts in primate recipients is initiated by the intragraft binding of either preformed (hyperacute xenograft rejection) or induced (acute vascular rejection) antiporcine recipient antibodies with subsequent complement activation via the classical pathway. We have investigated the efficacy of the supplemental administration of C1-inhibitor (C1-INH), a specific inhibitor of the classical complement activation pathway, for prophylaxis of xenograft rejection in a pig to primate kidney xenotransplantation setting.

METHODS

Based on the results of pharmacokinetic studies performed in two nontransplanted monkeys, supplemental C1-INH therapy was administered daily to three Cynomolgus monkeys receiving a life-supporting porcine kidney transplant together with cyclophosphamide-induction/cyclosporine A/mycophenolat-mofetil/steroid immunosuppressive therapy.

RESULTS

In the three monkeys receiving porcine kidney xenografts and continuous C1-INH treatment none of the grafts underwent hyperacute rejection; all xenografts showed initial function. Recipient survival was 13, 15, and 5 days. No graft was lost due to acute vascular rejection. All animals died with a functioning graft (latest creatinine 96, 112, and 96 micromol/liter) due to bacterial septicemia.

CONCLUSION

We conclude that, in our model, supplemental C1-INH therapy together with a standard immunosuppressive regimen can be helpful for prevention of xenograft rejection in a pig to primate kidney xenotransplantation setting. The optimal dose and duration of C1-INH treatment, however, has yet to be determined.

Cytomegalovirus early promoter induced expression of hCD59 in porcine organs provides protection against hyperacute rejection

The critical shortage of human donor organs has generated growing interest for porcine to human xenotransplantation. The major immunological barrier to xenotransplantation is the hyperacute rejection (HAR) response that is mediated by preformed xenoreactive antibodies and complement. A promising strategy to control the complement activation, is the expression of human complement regulatory proteins in transgenic animals. We have used the human early cytomegalovirus (CMV) promoter to drive expression of the human complement regulatory protein CD59 (hCD59) in transgenic pigs. A total of eight live transgenic founder animals was born from which five transgenic lines could be established. mRNA analysis and Western blotting revealed high expression of hCD59 in heart, kidney, skeletal muscle, and skin in animals of lines 1 and 5, as well as in the pancreas of four lines. This pattern of expression was confirmed by immunhistological staining. A cell-specific expression in heart and kidney tissue of transgenic lines 1 and 5 was determined. Primary fibroblasts and endothelial cell cultures derived from the aorta of transgenic pigs showed a significantly diminished sensitivity against the challenge with xenoreactive human antibodies and complement whereas non-transgenic control cells were highly susceptible to complement mediated lysis. Ex vivo perfusion of kidneys with pooled human blood revealed a significant protective effect of hCD59 against HAR. The average survival of transgenic kidneys was significantly extended (P<0.05) over nontransgenic controls (207.5+/-54.6 vs. 57.5+/-64.5 min). These data support the concept that hCD59 protects nonprimate cells against human complement mediated lysis and suggest that donor pigs transgenic for hCD59 could play a crucial role in clinical xenotransplantation. Two of five hCD59 transgenic lines showed strong hCD59 expression in several organs relevant for xenotransplantation and a protective effect against HAR. This indicates that the use of the CMV-promoter can facilitate the selection process for optimized transgene expression.

C1-Inhibitor for treatment of acute vascular xenograft rejection in cynomolgus recipients of h-DAF transgenic porcine kidneys

At present, the major barrier to successful discordant xenotransplantation of unmodified or complement regulator transgenic porcine xenografts is acute vascular xenograft rejection (AVR). AVR is associated with the intragraft deposition of induced recipient xenoreactive antibodies and subsequent complement activation. In a life-supporting pig to primate kidney xenotransplantation setting using h-DAF transgenic donor organs and postoperative immunosuppression, episodes of AVR were either treated with boluses of cyclophosphamide and steroids or with the same regimen supplemented by a three-day course of C1-Inhibitor, a multifunctional complement regulator. In 8 out of 10 animals stable initial graft function was achieved; in all animals one or more episodes of AVR were observed. When, in 4 animals, C1-Inhibitor was added to the standard anti-rejection treatment regimen, AVR was successfully reversed in 6 out of 7 episodes, while in another group of 4 animals receiving the standard anti-rejection treatment 0 out of 4 episodes of AVR responded to treatment. Response to anti-rejection treatment was associated with a significant increase in recipient survival time. We conclude that AVR of h-DAF transgenic porcine kidneys can be successfully treated by additional short-term fluid phase complement inhibition.

The immunological hurdles to cardiac xenotransplantation

The main hurdle to clinical application of cardiac xenotransplantation is the immune response of the recipient against the graft. Although all xenografts arouse an intense immune response, the effect of that response depends very much on whether the graft consists of isolated cells or an intact organ, such as the heart. Intact organs, which are transplanted by primary vascular anastomosis, are subject to severe vascular injury owing to the reaction of immune elements with the endothelial lining of donor blood vessels. Vascular injury leads to hyperacute rejection, acute vascular rejection, and chronic rejection. The immunological basis for these types of rejection and potential therapies, which might be used to avert them, are discussed.

Hemodynamic consequences of porcine kidney xenograft reperfusion in cynomolgus monkeys

BACKGROUND

After xenograft reperfusion, complement activation may lead to generation of anaphylatoxins and cardiocirculatory instability of the recipient.

METHODS

In 13 cynomolgus recipients of either unmodified or human decay accelerating factor transgenic porcine kidneys cardiocirculatory parameters were measured by single indicator transpulmonary thermodilution.

RESULTS

After graft reperfusion, recipient cardiac output decreased by 25.4% (P<0.05), intrathoracic blood volume by 22.8% (P<0.05), extravascular lung water increased slightly (P=n.s.). The impairment in cardiac output was neither influenced by the graft's weight or human decay accelerating factor transgenicity. sC3a and sC5b-9 complement levels in the recipient monkeys showed a sharp peak upon reperfusion.

CONCLUSIONS

After reperfusion a marked and significant cardiodepression accompanied by relative volume depletion were observed. Analysis of volume status ruled out a mere volume shift as the underlying reason for the observed drop in cardiac output. These data may be relevant for the perioperative management of human recipients of discordant xenografts in the future.

Physiologic and immunologic hurdles to xenotransplantation

The major problem in the field of renal transplantation is currently the shortage of available kidneys. However, the use of animals as a source of kidneys, i.e., xenotransplantation, is increasingly being viewed as a potential solution to this problem. One preeminent hurdle to xenotransplantation is the immune response of the recipient against the graft; other hurdles include the physiologic limitations of the transplant, infection, and ethical considerations. This review summarizes what is currently known regarding the obstacles to xenotransplantation and some potential solutions to those problems.

Acute vascular rejection is associated with systemic complement activation in a pig-to-primate kidney xenograft model

The introduction of h-DAF transgenic porcine organs into pre-clinical pig-to-primate discordant xenotransplantation has led to complete and reliable abrogation of hyperacute xenograft rejection (HAR). Despite additional heavy immunosuppression however, most xenografts are still lost due to acute vascular rejection (AVR), with current treatment protocols being of only limited value. In a life-supporting model of pig-to-primate kidney transplantation, unmodified (n=8) or h-DAF-transgenic (n=9) porcine kidneys were transplanted into cynomolgus monkeys under cyclophosphamide (CyP), cyclosporine and low-dose steroid immunosuppression. Longest recipient survival was 11 days in the control group and 68 days in the h-DAF transgenic group. Stable initial graft function with recipient survival >4 days was generated in eight animals (two controls and six transgenics). In these animals, plasma complement levels were analyzed during ongoing AVR. Compared with baseline levels, a two-fold increase in C3a levels and a four-fold increase in sC5b-9 levels were measured. In parallel to systemic complement activation, increased deposition of C3 and C5b-9 along with massive staining for recipient IgM immunoglobulins was detected in the xenografts on immunohistochemistry. We conclude that acute vascular xenograft rejection of porcine kidneys in cynomolgus monkeys is associated with classical pathway complement activation following binding of induced recipient anti-porcine antibodies. This complement activation can be observed despite membrane bound expression of human complement regulators in the porcine xenografts. Therefore, additional short-term fluid phase complement inhibition seems necessary for the future development of protocols designed for treatment of AVR in the pig-to-primate combination.