OBJECTIVETo review the current status and progress on pig islet xenotransplantation.

DATA SOURCESData used in this review were mainly from English literature of Pubmed database. The search terms were "pig islet" and "xenotransplantation".

STUDY SELECTIONThe original articles and critical reviews selected were relevant to this review's theme.

RESULTSPigs are suggested to be an ideal candidate for obtaining available islet cells for transplantation. However, the potential clinical application of pig islet is still facing challenges including inadequate yield of high-quality functional islets and xenorejection of the transplants. The former can be overcome mainly by selection of a suitable pathogen-free source herd and the development of isolation and purification technology. While the feasibility of successful preclinical pig islet xenotranplantation provides insights in the possible mechanisms of xenogeneic immune recognition and rejection to overwhelm the latter. In addition, the achievement of long-term insulin independence in diabetic models by means of distinct islet products and novel immunotherapeutic strategies is promising.

CONCLUSIONSPig islet xenotransplantation is one of the prospective treatments to bridge the gap between the needs of transplantation in patients with diabetes and available islet cells. Nonetheless, further studies and efforts are needed to translate obtained findings into tangible applications.

Animals ; Graft Rejection ; immunology ; prevention & control ; Islets of Langerhans Transplantation ; immunology ; methods ; Swine ; Transplantation, Heterologous ; methods

Microencapsulation of cells or tissue fragments represents a potentially effective method to prevent graft rejection in allotransplantation and xenotransplantation without the need of immunosuppression, but the functional survival of all trial grafts is still limited. Usually, graft failure is mainly interpreted as the consequence of the progressive fibrotic overgrowth of capsules, the insufficient supply of oxygen and nutrition to the encapsulated graft, and the dysfunction of the encapsulated graft induced by small proinflammatory factors. These detrimental factors are interrelatd with the microcapsules, the implanted graft, and the transplantation site. This article reviews and summarizes the advance and the limitation of microencapsulated grafts transplantation in the above-mentioned aspects.
Alginates ; chemistry ; Animals ; Biocompatible Materials ; chemistry ; Capsules ; Graft Survival ; immunology ; Humans ; Islets of Langerhans Transplantation ; immunology ; methods ; physiology ; Transplantation, Heterologous ; immunology

Up till 2000 when Edmonton group introduced islet transplant procedure in conjunction with a novel glucocorticoid-free immunosuppressive regimen rendering 100% (n=7) of patients with type 1 diabetes insulin-independent for at least 1 year, islet transplant was taken into the clinic. Although significant progress in clinical islet transplant has occurred during recent years, challenges remain, including shortage of available donor organs, technical aspects of islet preparation and transplantation, immunological rejection post-transplant, unclear long-term outcomes of islet transplantation. Special attention is given to current limitation in islet transplantation together with new possible strategies that raise expectations for the widespread use of islet transplantation in the future.
Diabetes Mellitus ; surgery ; Humans ; Immunosuppressive Agents ; therapeutic use ; Islets of Langerhans Transplantation ; immunology ; methods ; trends

Nonspecific inflammatory response is the major cause for failure of islet grafts at the early phase of intraportal islet transplantation (IPIT). Bilirubin, a natural product of heme catabolism, has displayed anti-oxidative and anti-inflammatory activities. The present study has demonstrated that bilirubin protected islet grafts by inhibiting nonspecific inflammatory response in a syngeneic rat model of IPIT. The inflammation-induced cell injury was mimicked by exposing cultured rat insulinoma INS-1 cells to cytokines (IL-1beta, TNF-alpha and IFN-gamma) in in vitro assays. At appropriate lower concentrations, bilirubin significantly attenuated the reduced cell viability and enhanced cell apoptosis induced by cytokines, and protected the insulin secretory function of INS-1 cells. Diabetic inbred male Lewis rats induced by streptozotocin underwent IPIT at different islet equivalents (IEQs) (optimal dose of 1000, and suboptimal doses of 750 or 500), and bilirubin was administered to the recipients every 12 h, starting from one day before transplantation until 5 days after transplantation. Administration of bilirubin improved glucose control and enhanced glucose tolerance in diabetic recipients, and reduced the serum levels of inflammatory mediators including IL-1beta, TNF-alpha, soluble intercellular adhesion molecule 1, monocyte chemoattractant protein-1 and NO, and inhibited the infiltration of Kupffer cells into the islet grafts, and restored insulin-producing ability of transplanted islets.
Animals ; Apoptosis/drug effects/immunology ; Bilirubin/*administration & dosage/pharmacology ; Cell Line, Tumor ; Cytokines/immunology/metabolism ; Diabetes Mellitus, Experimental/*drug therapy/*immunology ; Inflammation ; Inflammation Mediators/immunology/metabolism ; Islets of Langerhans/drug effects/*immunology/injuries/pathology ; *Islets of Langerhans Transplantation ; Male ; Oxidative Stress/drug effects/immunology ; Rats ; Rats, Inbred Lew ; Transplantation, I

Non-human primate studies must be conducted prior to the clinical trial of xenotransplantation. In order to develop clinically applicable immune-modulatory regimen through non-human primate studies, close monitoring of xenogeneic immune responses is required. We adopted multiplex cytokine analysis in assessment of the immune status during the course of pig-to-non-human primate islet transplantation. This study aimed to assess the feasibility of this multiplex cytokine assay in the development of immune-modulatory regimen. Using this assay, we were able to detect different cytokines with a minimal usage of blood samples, and this allowed us to detect various immunological situations in the recipients. Detection of TNF-alpha surge (347.8 pg/mL) guided us to block TNF-alpha in the early phase of transplantation. Supportive information for in vivo efficacy of cytokine neutralizing antibody could be speculated by in vitro neutralization assay (1,250 pg/mL --> 0 pg/mL). In addition, periodic monitoring of cytokines in peripheral blood allowed the detection of the infection episode prior to other routine assays. These benefits of multiplex cytokine assay may be generally applied to other pre-clinical research, which is a prerequisite for clinical trials.
Animals ; Antibodies, Neutralizing/immunology ; Blood Cell Count ; Cytokines/*blood/immunology ; Immunoassay/*methods ; Interleukin-6/blood ; Islets of Langerhans Transplantation/*immunology ; Macaca mulatta ; Swine ; Transplantation, Heterologous ; Tumor Necrosis Factor-alpha/blood/immunology

OBJECTIVETo study the effects of gene transfer cytotoxic T lymphocyte associated antigen 4 immunoglobulin (CTLA4-Ig) and anti-cluster of differentiation 154 (CD154) mAb on the rejection of rat islet xenografts.

METHODSHuman islets were infected with the recombinant adenoviruses containing CTLA4-Ig gene. Transduced islets were transplanted under the left kidney capsule of diabetic rats. And then the animal model were treated with anti-CD154 monoclonal antibody. The changes of blood sugar were measured and the survival rates of grafts and transplantation rats were observed after transplantation. The morphological changes of grafts were observed. Expression of CTLA4-Ig and insulin were detected by immunohistochemical staining and cytokines were quantified by ELISA.

RESULTS(1) The blood glucose of transplantation rats decreased to normal level on 2nd day post-transplantation. The average level blood glucose of control group A, anti-CD154mAb treatment group B, transfected group C and associated treatment group D increased on day 8, 18, 25, 36, post-transplantation respectively. (2) The grafts of group A, B, C and D survived for (10.0 +/- 2.1) d, (22.0 +/- 8.2) d, (28.0 +/- 6.5) d and (37.0 +/- 9.3) d respectively. The survival of grafts in group D was significant longer than that in group A, B and C, respectively; The survival of group B and C were significantly prolonged compared with group A and the survival of group B was significantly different with group C (P < 0.05). The survival of transplantation rats were (21.0 +/- 5.7) d, (35.0 +/- 6.5) d, (48.0 +/- 8.5) d and (65.0 +/- 12.5) d in group A, B, C and D, respectively. The survival of transplantation rats compared each other among four groups were same as the survival of grafts (P < 0.05). (3) In control animals (group A), serum IL-2 and TNF-alpha concentration were elevated to a high level within seven days post-transplantation and significantly increased compared with that before transplantation (P < 0.01). (4) Hematoxylin-eosin staining of grafts showed a lot of islets under the kidney capsule of transplantation rats, no inflammatory cell infiltrate and immunohistochemical staining of grafts demonstrated expression of insulin protein at islets in group B, C and D. These grafts positively stained for CTLA4-Ig in group C and D.

CONCLUSIONSGene transfer CTLA4-Ig and anti-CD154mAb treatment can inhibit the rejection of rat islet xenografts and treatment Ad-CTLA4-Ig and anti-CD154 mAb could induce immune tolerance of islet xenografts.

Adenoviridae ; genetics ; Animals ; Antibodies, Monoclonal ; therapeutic use ; CD40 Ligand ; immunology ; Diabetes Mellitus, Experimental ; surgery ; Genetic Vectors ; Graft Rejection ; immunology ; prevention & control ; Humans ; Immunoconjugates ; genetics ; Islets of Langerhans Transplantation ; Rats ; Rats, Wistar ; Transfection ; Transplantation, Heterologous

BACKGROUNDCostimulatory signals play a vital role in T cell activation. Blockade of costimulatory pathway by CTLA4Ig or CD40LIg have enhanced graft survival in experimental transplantation models yet mechanisms remain undetermined. We investigated the effects of CTLA4Ig and CD40LIg gene transfer on islet xenografts rejection in rats.

METHODSHuman islets were infected with recombinant adenoviruses containing CTLA4Ig and CD40LIg genes and implanted beneath the kidney capsule of diabetic rats. Levels of blood sugar, morphological changes, and survival of grafts were recorded. Expressions of CTLA4Ig, CD40LIg and insulin were detected by immunohistochemical staining and cytokines levels were quantified by enzyme-linked immunosorbent assay (ELISA).

RESULTSBlood glucose levels in transplant rats decreased to normal level on the 2nd day post transplantation. The mean blood glucose in the control group, CTLA4Ig transfected group, CD40LIg transfected group and CTLA4Ig + CD40LIg cotransfected group increased on days 8, 24, 21, 68, post transplantation respectively. The grafts in control group, CTLA4Ig transfected group, CD40LIg transfected group and CTLA4Ig + CD40LIg cotransfected group survived for (8 ± 1), (29 ± 4), (27 ± 3), and (74 ± 10) days, respectively. Survival in CTLA4Ig + CD40LIg cotransfected group was significantly longer. Survivals of CTLA4Ig transfected group and CD40LIg transfected group were significantly longer than control group. In control animals, serum interleukin-2 and tumor necrosis factor α concentration significantly increased within seven days post transplantation. Haematoxylin eosin staining of grafts showed live islets in situ of transplant rats without inflammatory cell infiltration. Immunohistochemical staining confirmed the expression of insulin at islets in all experimental groups.

CONCLUSIONSTransfer of CTLA4Ig and CD40LIg genes, especially the cotransfer of both, inhibits rejection of murine islet xenografts. Downregulated expressions of Th1 cells related cytokines might be related to the beneficial effects.

Abatacept ; Animals ; Enzyme-Linked Immunosorbent Assay ; Graft Rejection ; therapy ; Graft Survival ; genetics ; physiology ; Humans ; Immunoconjugates ; genetics ; metabolism ; Immunohistochemistry ; Insulin ; metabolism ; Islets of Langerhans Transplantation ; immunology ; methods ; Rats ; Recombinant Fusion Proteins ; genetics ; metabolism ; Transplantation, Heterologous ; immunology ; methods

Pancreatic islet transplantation can correct the abnormal glucose metabolism of Type 1 diabetes. Although immunosuppressants greatly reduce the acute rejection rate in transplant patients, the long-term side effects can be debilitating. Therefore, researchers are seeking to develop new immunosuppressive regimens that induce maximal levels of immunosuppression with minor side effects. Rosmarinic acid (Ros A) is a secondary metabolite of certain herbs and has multiple biological activities, including anti-inflammatory effects. Here, we have investigated whether treatment of mice with a combination of Ros A and anti-CD154 monoclonal antibody (MR1) improves islet allograft survival in a murine model. After transplantation, the mice were treated with either Ros A, MR1, or both (the "double" treatment). Allograft survival was prolonged in the double-treated animals compared to animals that received only Ros A or MR1. As is the case with the single-treated animals at 15 days after transplantation, the double-treated recipients did not display a significant decrease in the expression of cytokines or the population of activated T cells. Infiltrating CD3+ T cells were reduced in the MR1- or double therapy relative to control or RosA group. However, at the same time point, double-treated graft showed fewer apoptotic cells and increased expression of insulin and glucagons, compared to the single-treatment groups. Furthermore, long-term (>150 days) allografts that were received with double therapy exhibited larger islet clusters and contained more insulin- and glucagon-positive cells, relative to the MR1-treated grafts. In conclusion, treatment with both Ros A and MR1 has a synergistic effect in murine islet allotransplantation.
Animals ; Antibodies, Monoclonal/*pharmacology ; Apoptosis/drug effects ; CD40 Ligand/*immunology ; Cinnamates/*pharmacology ; Cytokines/biosynthesis ; Depsides/*pharmacology ; Diabetes Mellitus, Experimental ; Flow Cytometry ; Glucose/metabolism ; Glucose Tolerance Test ; Graft Survival/*drug effects ; In Situ Nick-End Labeling ; Injections, Intraperitoneal ; Islets of Langerhans/drug effects/pathology ; *Islets of Langerhans Transplantation ; Male ; Mice ; Mice, Inbred BALB C ; Mice, Inbred C57BL ; Time Factors ; Transplantation, Homologous

BACKGROUNDOX40/OX40 ligand (OX40/OX40L) and programmed death-1/programmed death ligand-1 (PD-1/PD-L1) costimulatory signals play important roles in T cell-induced immune responses. The aim of this study was to investigate the roles of OX40/OX40L and PD-1/PD-L1 costimulatory pathways in mouse islet allograft rejection.

METHODSLentiviral vectors containing OX40L siRNA sequences and an adenovirus vector containing the PD-L1 gene were constructed. The streptozotocin-induced model of diabetes was established in C57BL/6 (H-2(b)) mice. Diabetic C57BL/6 mice were randomly allocated into five groups: group 1, untreated control; group 2, Ad-EGFP treatment; group 3, Ad-PD-L1 treatment; group 4, OX40L-RNAi-LV treatment; group 5, OX40L-RNAi-LV combined with Ad-PD-L1 treatment. Lentiviral vector and the adenovirus vector were injected, singly or combined, into the caudal vein one day before islet transplantation. The islets of DBA/2 (H-2(d)) mice were transplanted into the renal subcapsular space of the diabetic recipients. Recipient blood glucose and the survival time of the allografts were monitored. Antigen-specific mixed lymphocyte reaction was also evaluated.

RESULTSThe recombinant lentiviral RNA interference vector OX40L-RNAi-LV reduced OX40L protein expression by 70%. The recombinant adenovirus vector Ad-PD-L1 increased PD-L1 protein expression in vivo in C57BL/6 recipient mice. Combined OX40L-RNAi-LV/Ad-PD-L1 treatment induced a synergistic protective effect in pancreatic islet allografts. Allograft survival time in the combined treatment group was (92.27±9.65) days, not only longer than that of the control ((6.51±0.27) days) and Ad-EGFP groups ((7.09±0.13) days) (P < 0.01), but also significantly longer than that of Ad-PD-L1 and OX40L-RNAi-LV single treatment groups ((40.64±3.95) days and (55.14±5.48) days respectively, P < 0.01). The blood glucose concentration of recipient mice in the combined treatment group was also stable and kept within the normal range. Flow cytometry analysis showed that combined OX40L-RNAi-LV/Ad-PD-L1 treatment significantly decreased proliferation in an antigen-specific mixed lymphocyte reaction. After donor DBA/2 lymphocyte stimulation, 89.71% of lymphocytes from recipient combination treatment C57BL/6 mice were not split and proliferated. In contrast, after stimulation with third party Lewis rat lymphocytes, only 45.84% lymphocytes of C57BL/6 mice were not split and proliferated.

CONCLUSIONSThis study demonstrates the successful construction of the recombinant lentivirus vector OX40L-RNAi-LV and adenovirus vector Ad-PD-L1 for the blockade of OX40/OX40L and activation of PD-1/PD-L1 costimulatory pathways simultaneously in pancreatic islet allografts in diabetic mice. Combination therapy with these two vectors resulted in inhibition of T cell activation, synergistically prolonging the survival time of pancreatic islet allografts.

Animals ; B7-H1 Antigen ; genetics ; metabolism ; Graft Rejection ; genetics ; prevention & control ; Islets of Langerhans Transplantation ; immunology ; Male ; Mice ; Mice, Inbred C57BL ; OX40 Ligand ; genetics ; metabolism ; Receptors, OX40 ; genetics ; metabolism ; Transplantation, Homologous

BACKGROUND: Anti-Gal is a major antibody induced in non-human primates (NHPs) after xenotransplantation. To understand the mechanism of graft rejection, we investigated the association between anti-Gal responses and graft failure in NHP recipients of porcine islet transplantation (PITx). METHODS: Intraportal PITx was performed in 35 diabetic NHPs, and graft function was monitored. Early graft failure (EGF) was defined as loss of graft function within a month after PITx. Seven, 19, nine NHPs received immunosuppression (IS) without CD40 pathway blockade (Group I), with anti-CD154 (Group II), and with anti-CD40 (Group III), respectively. The anti-Gal levels on day 0 and day 7 of PITx were measured by ELISA. RESULTS: The frequency of EGF was significantly lower in Group II (26.3%) than in Group I (100%, P=0.0012) and Group III (77.8%, P=0.0166). While levels of anti-Gal IgG in Group I and anti-Gal IgM in Group III increased on day 7 compared with day 0 (P=0.0156 and 0.0273), there was no increase in either on day 7 in Group II. The ratio of anti-Gal IgM or IgG level on day 7 to that on day 0 (Ratio7/0) was significantly higher in recipients with EGF than without EGF (P=0.0009 and 0.0027). ROC curve analysis of anti-Gal IgM Ratio7/0 revealed an area under the curve of 0.789 (P=0.0003). CONCLUSIONS: IS with anti-CD154 suppressed anti-Gal responses and prevented EGF in PITx. Anti-Gal IgM Ratio7/0, being associated with EGF, is a predictive marker for EGF.
Animals ; Antibodies/blood/immunology ; Antigens, CD40/immunology ; Area Under Curve ; CD40 Ligand/immunology ; Disaccharides/*immunology ; Epidermal Growth Factor/blood ; Graft Rejection/*immunology ; Immunoglobulin G/blood ; Immunoglobulin M/*blood ; Immunosuppressive Agents/therapeutic use ; *Islets of Langerhans Transplantation ; Macaca mulatta ; ROC Curve ; Swine ; Transplantation, Heterologous