Successful islet auto- and allotransplantation in diabetic pigs

Distributions of endocrine cell clusters during porcine pancreatic development

Background

Pancreatic islet xenotransplantation is a potential treatment for diabetes mellitus, and porcine pancreas may provide a readily available source of islets. Islets in juvenile pigs are smaller than those in young adult pigs, but the insulin content is very similar. In addition, as juvenile pigs are more easily reared in uncontaminated conditions, many researchers have conducted studies using pancreatic islets from juvenile pigs. We aimed to analyze the distributions of endocrine cell clusters by comprehensively evaluating juvenile porcine pancreatic development and to propose an appropriate age at which islets could be isolated from the juvenile porcine pancreas.

Methods

Splenic (SL) and duodenal lobe (DL) samples were collected from the pancreases of pigs aged 0–180 days (n = 3/day after birth). The chronological changes in endocrine cell clustering were analyzed in relation to morphological changes, cell characterization, numbers, islet areas, and gene expression.

Results

In juvenile pigs aged 0–21 days, the pancreas contained numerous endocrine cells, and compact islets appeared from 21 days of age. Well-defined small islets were seen at 28 days of age, and the clusters were denser in the SL than in the DL. At 35 days of age, the islets were morphologically similar to those observed at 180 days of age, and the greater number of islets was similar to that seen at 90 days of age. The differences in the islets’ cytoarchitecture between the lobes were negligible. The expression of β-cell-related genes was higher in the juvenile pancreas than in the adult pancreas, and the expression of neurogenin-3 decreased dramatically over time.

Conclusions

These findings may have implications for attempts to refine the most appropriate age for islet isolation from porcine donors. Focusing on porcine pancreatic islets isolated at around 35 days after birth may offer benefits regarding their xenotransplantation potential.

Establishment of a diabetic myocardial hypertrophy model in Mus musculus castaneus mouse

The aim of this study was to establish a robust model of diabetic myocardial hypertrophy in Mus musculus castaneus mice. Mice were fed a high-fat diet for four weeks and then given streptozotocin (STZ, 40 mg kg-1  d-1 for 5 days, intraperitoneally) and fasting blood glucose (FBG) levels were tested after seven days. Mice with FBG levels above 11.1 mmol/L were considered diabetic. Diabetic mice continued to have access to the high-fat diet until cardiac hypertrophy developed. FBG and body weight (BW) were measured weekly. Myocardial hypertrophy was confirmed by left ventricle (LV) hypertrophy index (LVHI), LV/BW, LV histopathological observation and atrial natriuretic factor (ANF) mRNA expression. Serum insulin and plasma haemoglobin A1c (HbA1c) levels, total cholesterol (TCH) and triglyceride (TG) were measured, and then an insulin resistance index (HOMA.IR) was calculated. The level of FBG in the model group remained above 11.1 mmol/L, and the BW showed significant weight loss, compared with the control group (P < 0.01). The high levels of HbA1c, HOME.IR, TCH and TG, and the low level of insulin suggested that glucose metabolism was not balanced with insulin resistance; meanwhile, higher TCH and TG showed that dyslipidaemia had also developed. After the diabetic mice were kept on the high-energy diet for another four  weeks, histopathological observation showed myocardial injuries, much more surface area and collagen fibres, higher LVHI and LV/BW, and elevated expression of ANF mRNA (P < 0.01), suggesting that myocardial hypertrophy had appeared in Mus musculus castaneus mice under the current experimental conditions. Thus a robust model of diabetic myocardial hypertrophy was established four  weeks after confirmation of diabetes, which was induced by feeding a high-fat diet for four weeks combined with a repeated low-dose STZ exposure, in Mus musculus castaneus mice.

Long-Term Insulin Independence following Repeated Islet Transplantation in Totally Pancreatectomized Diabetic Pigs

Clinical islet transplantation (Tx) in type I diabetic patients has been successful so far only in a minority of cases, probably because of multiple factors, partly immunologic and partly nonimmunologic in nature. Pre-clinical studies of islet Tx in large animals are still needed to clarify the reasons and find possible solutions. In this study, we tested the feasibility of noninvasive, repeated intrahepatic allo-Tx of porcine pancreatic islets obtained from multiple donors, in pigs rendered diabetic by total pancreatectomy (Pct). In group I Yucatan miniature swine (n = 6), after induction of diabetes by Pct, repeated islet allo-Tx of ≥80% pure islets was performed. Islets obtained from two pigs of the Hanford breed were injected twice a week, half freshly isolated and half 48-h cultured, over a period of 11 days, for a total of 23,647 ± 1617 islet equivalents (IE)/kg recipient body weight (BW). In group II Yucatan miniature swine (n = 3), after Pct, a single allo-Tx of ≥80% pure islets, previously obtained from two donors of the Hanford breed, was performed, using a total of 22,416 ± 1124 IE/kg BW. In group III Yucatan miniature swine (n = 3), auto-Tx of 60–75% pure islets, averaging 2980 ± 424 IE/kg BW, was performed a few hours after Pct. Group IV Yucatan mini pigs (n = 3) underwent Pct and were used as diabetic controls. Group V animals (n = 3) were normal control Yucatan mini pigs. Porcine islets were isolated by a modification of the standard collagenase digestion and Ficoll gradient purification method. Donors and recipients were chosen on the basis of moderate to high mutual alloreactivity in mixed lymphocyte culture (MLC). In groups I and II, cyclosporine A (CsA) was started 4 days before allo-Tx, at the dose of 15 mg/kg IM, and then gradually reduced to 4 mg/kg IM. In all group I animals, normal fasting blood glucose (FBG) was restored within 2–3 weeks. Two normoglycemic pigs died of acute pneumonia at 33 and 112 days, respectively, and one animal became progressively hyperglycemic at 100 days. After 3 months, discontinuation of CsA treatment resulted in FBG increase in two group I animals. In one pig, CsA was stopped after 151 days, and normoglycemia persisted until euthanasia, after 8 months. In group II pigs, normoglycemia lasted 4–20 days, with a progressive increase of insulin requirement thereafter. In group III animals, after islet auto-Tx, normoglycemia lasted 7–10 days, while insulin daily requirement progressively increased thereafter, stabilizing at 0.4 IU/kg/day, corresponding to about one third of the amount required in diabetic controls. The single most important result in this series of experiments is that intraportal allo-Tx of a sufficient islet mass, divided in multiple subtherapeutic doses, produced a better metabolic long-term control in comparison to a single injection of the same amount of islets. The technique of multiple-donor repeated islet Tx may prove useful to overcome the problem of primary nonfunction or early graft failure, currently limiting the success of clinical islet Tx in most cases.

Effects of exercise on brain functions in diabetic animal models

Human life span has dramatically increased over several decades, and the quality of life has been considered to be equally important. However, diabetes mellitus (DM) characterized by problems related to insulin secretion and recognition has become a serious health problem in recent years that threatens human health by causing decline in brain functions and finally leading to neurodegenerative diseases. Exercise is recognized as an effective therapy for DM without medication administration. Exercise studies using experimental animals are a suitable option to overcome this drawback, and animal studies have improved continuously according to the needs of the experimenters. Since brain health is the most significant factor in human life, it is very important to assess brain functions according to the different exercise conditions using experimental animal models. Generally, there are two types of DM; insulin-dependent type 1 DM and an insulin-independent type 2 DM (T2DM); however, the author will mostly discuss brain functions in T2DM animal models in this review. Additionally, many physiopathologic alterations are caused in the brain by DM such as increased adiposity, inflammation, hormonal dysregulation, uncontrolled hyperphagia, insulin and leptin resistance, and dysregulation of neurotransmitters and declined neurogenesis in the hippocampus and we describe how exercise corrects these alterations in animal models. The results of changes in the brain environment differ according to voluntary, involuntary running exercises and resistance exercise, and gender in the animal studies. These factors have been mentioned in this review, and this review will be a good reference for studying how exercise can be used with therapy for treating DM.

Establishment of a stringent large animal model of insulin-dependent diabetes for islet autotransplantation: combination of pancreatectomy and streptozotocin

OBJECTIVE

A stringent porcine islet autograft diabetes model was developed to enable the assessment of autoislet safety and efficacy in either portal vein or an extrahepatic site.

METHODS

A 95% pancreatectomy was performed preserving the pancreaticoduodenal arcade; however, glycemic control was still maintained at 3.3 ± 0.3 days (mean ± SEM), shown by euglycemic fasting blood glucose levels of 4.9 ± 0.8 mmol/L (mean ± SEM, n = 3). To reduce surgical complications and eliminate remaining islets, pigs were dosed intravenously after a modified 90% pancreatectomy, with 150-mg/kg streptozotocin, producing a diabetic state (18.9 ± 1.8 mmol/L [mean ± SEM], n = 8; P < 0.001) within 2.0 ± 0.9 days (mean ± SEM).

RESULTS

Animals presented with sustained hyperglycemia, failing a glucose challenge test 12 weeks after diabetic induction, and showed no stimulated C-peptide secretion compared to nondiabetic controls (baseline: 0.479 ± 0.080 ng/mL [mean ± SEM] vs after procedure: 0.219 ± 0.055 ng/mL [mean ± SEM], P = 0.02). Diabetic animals were maintained on daily insulin. Despite an initial decline in body weight acutely after pancreatectomy and streptozotocin administration, the mean body weight increased after induction over the approximately 88-day study, indicating that the animals were in good health.

CONCLUSION

This stringent porcine model of diabetic induction should be used to assess autograft transplantation safety and efficacy.

The use of animal models in diabetes research

Diabetes is a disease characterized by a relative or absolute lack of insulin, leading to hyperglycaemia. There are two main types of diabetes: type 1 diabetes and type 2 diabetes. Type 1 diabetes is due to an autoimmune destruction of the insulin-producing pancreatic beta cells, and type 2 diabetes is caused by insulin resistance coupled by a failure of the beta cell to compensate. Animal models for type 1 diabetes range from animals with spontaneously developing autoimmune diabetes to chemical ablation of the pancreatic beta cells. Type 2 diabetes is modelled in both obese and non-obese animal models with varying degrees of insulin resistance and beta cell failure. This review outlines some of the models currently used in diabetes research. In addition, the use of transgenic and knock-out mouse models is discussed. Ideally, more than one animal model should be used to represent the diversity seen in human diabetic patients.

Endoscopic gastric submucosal transplantation of islets (ENDO-STI): technique and initial results in diabetic pigs

The results of transplantation of human donor islets into the portal vein (PV) in patients with diabetes are encouraging. However, there are complications, for example, hemorrhage, thrombosis and an immediate loss of islets through the 'instant blood-mediated inflammatory reaction' (IBMIR). The gastric submucosal space (GSMS) offers potential advantages. Islets were isolated from adult pigs. Recipient pigs were made diabetic by streptozotocin. Donor islets were injected into the GSMS through a laparotomy (Group 1A, n = 4) or endoscopically (Group 1B, n = 8) or into the PV through a laparotomy (Group 2, n = 3). The pigs were followed for a maximum of 28 days. Monitoring of C-peptide in Group 1 indicated that there was minimal immediate loss of islets whereas in Group 2 there was considerable loss from IBMIR. In Group 1, there were significant reductions in mean blood glucose and mean exogenous insulin requirement between pretransplantation and 20 days posttransplantation. In Group 2, there was no significant reduction in either parameter. Insulin-positive cells were seen in the GSMS in Group 1, but not in the liver in Group 2. Endoscopic gastric submucosal transplantation of islets (ENDO-STI) offers a minimally invasive and quick approach to islet transplantation, avoids IBMIR and warrants further exploration.

Safe induction of diabetes by high-dose streptozotocin in pigs

OBJECTIVES

Streptozotocin (STZ) has been widely used to induce diabetes in rodents and nonhuman primates, but it has been found difficult to achieve a completely diabetic state in pigs in the absence of detrimental side effects. As a result, pancreatectomy has been advocated in this species. We have investigated the effects of 2 dosages of STZ to safely induce diabetes in pigs.

METHODS

Three pigs received Zanosar STZ at 150 mg/kg (group 1). Four pigs received Zanosar STZ at 200 mg/kg (group 2). The levels of glucose, insulin, and C-peptide when (a) fasting, (b) 30 minutes after eating, and (c) during intravenous glucose tolerance tests (IVGTTs) were measured in all pigs for 4 weeks after STZ injection. To confirm how long the diabetic state can be maintained after induction with STZ, levels were measured for 20 weeks in group 2.

RESULTS

One to 4 weeks after STZ administration, in group 1 (150 mg/kg) pigs, insulin and C-peptide levels were detected up to 7 microIU/mL and 0.4 ng/mL, respectively, both when fasting and after a meal test or IVGTT, indicating that the pigs had failed to become fully diabetic. In group 2 (200 mg/kg) pigs, insulin and C-peptide levels were less than the 2 microIU/mL and 0.25 ng/mL respective detection levels and did not increase after a meal test or IVGTT. Group 2 remained completely diabetic for the entire 20-week period of follow-up, without STZ-related hepatic or renal dysfunction.

CONCLUSIONS

High-dose (200 mg/kg) Zanosar STZ induces diabetes safely and completely in pigs without side effects. Pancreatectomy can, therefore, be avoided.

Nutrient control of insulin secretion in perifused adult pig islets

OBJECTIVES

Xenotransplantation of pig islets is a potential solution to the shortage of human islets, but our knowledge of how these islets secrete insulin in response to nutrients is still fragmentary. This was the question addressed in the present study.

METHODS

After 24 h culture adult pig islets were perifused to characterize the dynamics of insulin secretion. Some responses were compared to those in human islets.

RESULTS

Increasing glucose from 1 to 15 mM weakly (approximately 2x) stimulated insulin secretion, which was potentiated (approximately 12x) by the cAMP-producing agent, forskolin. The effect of glucose was concentration-dependent (threshold at 3-5 mM and maximum at approximately 10 mM). The pattern of secretion was biphasic with a small first phase and an ascending second phase, and a paradoxical increase when the glucose concentration was abruptly lowered. Diazoxide abolished glucose-induced insulin secretion and tolbutamide reversed the inhibition. Glucose also increased secretion when islets were depolarized with tolbutamide or KCl. Insulin secretion was increased by leucine+glutamine, arginine, alanine or a mixture of amino acids, but their effect was significant only in the presence of forskolin. Upon stimulation by glucose alone, human islets secreted approximately 10x more insulin than pig islets, and the kinetics was characterized by a large first phase, a flat second phase, and rapid reversibility.

CONCLUSIONS

Compared with human islets, in vitro insulin secretion by adult pig islets is characterized by a different kinetics and a major quantitative deficiency that can be corrected by cAMP.

Unexpected immunoresponse to Gal and APA antigens in diabetic type 1 patients receiving neonatal pig islets after 6 years

Cotransplantation of porcine islets and Sertoli cells into preimplanted subcutaneous devices improve metabolic control in type 1 diabetic patients, and survive grafted for more than 4 years. We report here, further assessment of the endocrine and porcine nature of the surviving cells and the immune responses elicited toward Gal alpha(1,3)-Gal beta(1,4)-GlcNAc (Gal) antigen in patients who received a second and third transplants. No immunosuppressive drugs were administered. We were able to immunostain insulin- and glucagon-positive cells in all biopsies of patients and Sertoli cell markers in 60.9% of biopsies. Additionally, all biopsies tested, amplified the porcine COII gene. Patients demonstrated an increase in antipig antibodies in response to the first transplant with a decreasing response toward the second and third transplants. In all transplants, the IgG levels promptly returned to basal values after 3-4 months. The long-term survival of porcine cells and the reduced humoral immune response to multiple transplants indicate a form of tolerance. We have not been able to find CD25-positive cells, indicating that it is probably an immune accommodation of the graft.

Pancreas islet transplantation in the genitourinary tract associated with renal transplantation: an experimental study

Conceptually, pancreas islet transplantation (PIT) associated with renal transplantation (RT) should resolve not only chronic renal failure but also diabetes. Although the most frequently used site for PIT is the portal vein, genitourinary locations could be technically feasible during RT. Seventeen pigs (age 3 to 4 months; mean weight 34.5 kg) underwent the following experimental steps: On day 1 a left nephrectomy was performed and the kidney was perfused with cold Wisconsin solution. This was followed by a caudal pancreatectomy and islet isolation by means of digestion with intraductal collagenase. Islets were stained with Dithizone and cultured overnight al 37 degrees C and 5% CO(2). On day 2 a right nephrectomy and orthotopic RT of the preserved left kidney were performed. The islets were transplanted into four different sites: subcapsular in the kidney graft, in the bladder submucosa, in the testis by puncture, and in the testis by infusion through the vas deferens. On day 7 the animals were sacrificed. Islet viability was determined by histological examination with insulin immunostaining and determination of insulin in the blood of the veins draining the implantation sites. The mean weight of the pancreatic specimens was 27.8 g (13 to 46). The mean number of islets was 536,000 (16,600 to 1,5000,000). Islets were shown in the bladder submucosa and the testes after vas deferens infusion. The number of viable islets in the other implantation sites was very scarce. The insulin levels of the venous effluents were: 15.1 microU/mL for bladder submucosa, 10.2 microU/mL for intradeferential injection in the testis, 7.3 microU/mL for intratesticular injection by puncture, and 2.6 microU/mL for subcapsular implantation in the graft. In conclusion, the bladder submucosa and testis via the vas deferens might represent alternative sites for PIT. The latter route may benefit from the immunoprivileged and special trophic conditions of the testis. For the first time, the feasibility of the bladder submucosa as an implantation site for pancreas islets was demonstrated.

Reversal of diabetes in pancreatectomized pigs after transplantation of neonatal porcine islets

Neonatal porcine islets (NPIs) are able to grow and to reverse hyperglycemia after transplantation in immunoincompetent mice. The aim of this study was to demonstrate the feasibility of allogeneic NPI grafts to achieve normoglycemia in a pancreatectomized diabetic pig. NPIs were isolated from pancreases of 1- to 3-day-old pigs, cultured, and then transplanted via the portal vein into the liver of totally pancreatectomized pigs (mean body weight, 20.8 kg). Each pig received NPIs consisting of 3.1 +/- 0.3 x 10(6) beta-cells/kg (12,476 +/- 1,146 islet equivalent/kg). The six pigs that were given cyclosporine and sirolimus achieved normoglycemia by day 14 without insulin therapy. Three pigs died of surgical complications shortly after transplantation, whereas the other three remained insulin independent up to day 69. Of seven nonimmunosuppressed recipients, four pigs became normoglycemic by day 14 without insulin treatment, with two of the animals remaining normoglycemic long term. Well-preserved insulin-positive cells were found in the graft at the end of follow-up with a significant increase in insulin content in long-term survivors of both groups. This study demonstrates for the first time that allogeneic NPIs can reverse hyperglycemia in totally pancreatectomized diabetic pigs.

Development of a porcine model of type 1 diabetes by total pancreatectomy and establishment of a glucose tolerance evaluation method

PURPOSE

To develop and evaluate the efficacy of diabetes-targeted cell therapies in humans, a reliable model in larger animals is highly desirable. This article reports the surgical technique of total pancreatectomy in pigs and the biochemical analysis of the characteristics of totally pancreatectomized pigs.

METHODS

Surgical total pancreatectomy was conducted in 23 pigs. Blood glucose, insulin, biochemistries, activity index, and intravenous glucose tolerance test (IVGTT) were examined to assess the pathophysiological profiles of diabetic pigs.

RESULTS

A total of 14 pigs successfully underwent total pancreatectomy without requiring biliary reconstruction and were analyzed in the present study. Activity index was decreased from day 5 on and the mean survival of totally pancreatectomized pigs was 7.6 +/- 2.7 days. No endogenous insulin secretion was confirmed in these pigs. Pigs which received total pancreatectomy demonstrated significantly higher levels of ketone bodies. IVGTT performed within 4 days after total pancreatectomy showed a spontaneous decrease in blood glucose levels despite an absence of endogenous insulin secretion. IVGTT on day 5 or later showed continued hyperglycemia in pigs with total pancreatectomy. Histological examination showed atrophy of hepatocytes and decreased glycogen storage in the liver and decreased mucus production of the small intestine.

CONCLUSION

This article describes a porcine model of diabetes created by total pancreatectomy and it analyzes the pathophysiological profiles in the animals. The present study has suggested that IVGTT on day 5 or later after total pancreatectomy is a reliable method to evaluate the efficacy of cell therapies.

Use of the Gottingen Minipig as a Model of Diabetes, with Special Focus on Type 1 Diabetes Research

Animal models of type 1 diabetes remain essential tools for investigation of the etiology and pathogenesis of the disease and, importantly, for the development of effective new treatments. Although a range of well-characterized and widely used models of type 1 diabetes in rodents are currently available, large animal models are a valuable complement to rodent models for both physiological and practical reasons. The pig is very useful in many aspects as a model for human physiology and pathophysiology because many organ systems of this species, as well as physiological and pathophysiological responses, resemble those of the human. The Göttingen minipig is particularly suitable for long-term studies because of its inherent small size and ease of handling, even at full maturity. Of particular relevance to the field of type 1 diabetes are the many similarities evident between humans and pigs with regard to pharmacokinetics of compounds after subcutaneous administration, structure and function of the gastrointestinal tract, morphology of the pancreas, and the overall metabolic status of the two species. Because spontaneous type 1-like diabetes is very rare in pigs, a model of the condition must be induced experimentally, either surgically or chemically. This process is discussed, and the use of the pig as a model in islet transplantation and diabetic complications is briefly summarized.

Effect of immunosuppressive doses of cyclosporine on pancreatic beta cell function in pigs

OBJECTIVE

To evaluate whether immunosuppressive doses of cyclosporine (CsA) have an adverse effect on the liver, kidney, and pancreatic beta cells of pigs.

ANIMALS

8 juvenile 8-week-old Landrace X Large White crossbred pigs.

PROCEDURE

CsA (100 to 140 mg/kg) was administered orally to euglycemic pigs to reach whole blood trough concentrations of approximately 1500 ng/mL. To determine pancreatic beta cell function, plasma C-peptide and insulin concentrations were measured in response to i.v. administration of glucose, glucagon, arginine, and oral administration of glucose. Effects on liver and kidney were determined by monitoring serum measurements of liver function and serum creatinine concentrations, respectively.

RESULTS

Plasma concentrations of C-peptide were significantly lower in euglycemic CsA-treated pigs, compared with control pigs, following i.v. administration of glucose, glucagon, arginine, and oral administration of glucose. Furthermore, the glucose clearance rate was decreased in euglycemic CsA-treated pigs, compared with control pigs. Serum creatinine concentrations and 4 of 7 serum measurements of liver function were not adversely affected by CsA administration. Serum concentrations of bilirubin and albumin were significantly increased, and serum alanine aminotransferase activity was significantly decreased in CsA-treated pigs, compared with control pigs. Histologic evaluation of liver and kidney sections revealed no pathologic findings in CsA-treated or control pigs.

CONCLUSIONS AND CLINICAL RELEVANCE

In our study, immunosuppressive doses of CsA caused an impairment of porcine pancreatic beta cell function, but did not have toxic effects on the kidney. However, on the basis of changes in serum bilirubin and albumin concentrations and alanine aminotransferase activity, subclinical toxic effects on the liver did occur when immunosuppressive doses of CsA were administered.

Mild streptozotocin diabetes in the Göttingen minipig. A novel model of moderate insulin deficiency and diabetes

Nonrodent models of diabetes are needed for practical and physiological reasons. Induction of mild insulin-deficient diabetes was investigated in male Göttingen minipigs by use of streptozotocin (STZ) alone (75, 100, and 125 mg/kg) or 125 mg/kg combined with pretreatment with nicotinamide (NIA; 0, 20, 67, 100, 150, and 230 mg/kg). Use of NIA resulted in a less steep slope of the regression line between fasting plasma glucose and changing doses compared with STZ [-7.0 +/- 1.4 vs. 29.7 +/- 7.0 mM. mg(-1). kg(-1), P < 0.0001]. Intermediate NIA doses induced moderate changes of glucose tolerance [glucose area under the curve increased from 940 +/- 175 to 1,598 +/- 462 mM. min, P < 0.001 (100 mg/kg) and from 890 +/- 109 to 1,669 +/- 691 mM. min, P = 0.003 (67 mg/kg)] with reduced insulin secretion [1,248 +/- 602 pM. min after 16 days and 1,566 +/- 190 pM. min after 60 days vs. 3,251 +/- 804 pM. min in normal animals (P < 0.001)] and beta-cell mass [5.5 +/- 1.4 mg/kg after 27 days and 7.9 +/- 4.1 mg/kg after 60 days vs. 17.7 +/- 4.7 mg/kg in normal animals (P = 0.009)]. The combination of NIA and STZ provided a model characterized by fasting and especially postprandial hyperglycemia and reduced, but maintained, insulin secretion and beta-cell mass. This model holds promise as an important tool for studying the pathophysiology of diabetes and development of new pharmacological agents for treatment of the disease.

Rapid failure of pig islet transplantation in non human primates

We have previously demonstrated that adult pig islets of Langerhans are not destroyed in vitro by primate sera. Whether these islets can function when placed into the liver of non-human primates is not known. We now report on the outcome of pig islet xenotransplantation into five non diabetic primates (four baboons and one macacus fascicularis) receiving intraportally purified adult pig islets. The average number of islet-equivalent per graft was 110,000 (60-180,000). All animals received associations of ATG, cyclosporine or LF 195 (a deoxyspergualin analog), mycophenolate mofetil and corticosteroids. A specific porcine C-peptide (C-pep) RIA test was used to monitor insulin secretion. Two hours after grafting, porcine C-peptide was positive (from 0.37 to 4.25 ng/ml) in all monkeys except one. Primate C-pep was normal in all cases. Only two monkeys had detectable levels of porcine C-pep on day 1 or 2 with undetectable levels thereafter, even after glucagon challenge between days 6 and 10. Several normal islets with moderate inflammatory infiltration were observed in one animal liver on day 2 (the time of necropsy) as well as islets with IgM and complement deposition. Among animals sacrificed on days 14, 16 and 38, some residual islet cells could be identified only in livers collected on day 14. Partial glycaemic control was achieved in some rats receiving islets from the same preparations. In conclusion, adult pig islets are not able to maintain insulin secretion for more than 24 h when injected intraportally into non diabetic immunosuppressed monkeys. suggesting immediate islet xenograft destruction.

Diabetic rats transplanted with adult porcine islets and immunosuppressed with cyclosporine A, mycophenolate mofetil, and leflunomide remain normoglycemic for up to 100 days

BACKGROUND

Transplantation of adult porcine islets (APIs) offers a possible means of treating diabetes. However, isolating APIs has been notoriously difficult. Furthermore, islet xenograft rejection must be prevented.

MATERIALS AND METHODS

APIs were isolated by a modified automated method. API quality was assessed by static glucose stimulation (SGS), by transplantation to diabetic nude mice and by intraperitoneal glucose tolerance tests (IPGTTs). The morphologic characteristics of API xenograft rejection in rats were studied immunohistochemically. Furthermore, APIs were transplanted to diabetic rats that were either left untreated or immunosuppressed with cyclosporine A (CsA), mycophenolate mofetil (MMF) and leflunomide (LEF). B-glucose and porcine C-peptide levels were monitored and grafts were studied morphologically.

RESULTS

Large numbers of APIs were isolated. At SGS, insulin release increased significantly. All nude mice transplanted with APIs were normoglycemic within 24 hr and remained so for up to 1 year. During IPGTTs, B-glucose levels were rapidly regulated to porcine levels. In untreated rats, API xenografts were destroyed within 6 days by a cellular infiltrate consisting mainly of macrophages. In untreated diabetic rats normoglycemia was sustained for 5.5+/-0.3 days. Rats immunosuppressed with CsA+MMF+LEF remained normoglycemic for 59.6+/-11.3 days. In 3 of 11 rats, normoglycemia was sustained for up to 101 days. Porcine C-peptide was detected in serum. At recurrence of hyperglycemia, many mononuclear cells were found close to the xenografts. However, only occasional cells infiltrated the grafts and many APIs were intact.

CONCLUSIONS

Well-functioning APIs can be isolated in large numbers. API xenografts can be protected from rejection and can maintain an adequate function for up to 100 days, in rats immunosuppressed with CsA+MMF+LEF.

Lowering of blood glucose to nondiabetic levels in a hyperglycemic pig by allografting of fetal pig isletlike cell clusters

BACKGROUND

Fetal pig isletlike cell clusters (ICCs) will differentiate when grafted into the thymus gland of outbred immunosuppressed nondiabetic pigs for up to 3 months. Whether these cells will survive for a similar period in a diabetic recipient and will mature with secretion of insulin to ameliorate the hyperglycemia is unknown.

METHODS

Between 40,000 and 125,000 ICCs (7,000 to 11,400 ICCs/kg) were injected into the thymus gland of five juvenile pigs immunosuppressed with cyclosporine and deoxyspergualin, and the animals were subsequently made diabetic by the injection of streptozotocin. Insulin was administered subcutaneously, with one pig dying from hypoglycemia. The animal with the least number of ICCs transplanted was killed 81 days later, and the graft was analyzed histologically. Blood glucose levels and porcine C-peptide in the remaining animals were monitored for a median of 101 days.

RESULTS

Histological analysis of the graft showed numerous epithelial cell clusters; the percentage of cells that contained insulin, glucagon, somatostatin, and pancreatic polypeptide were 61%, 64%, 25%, and 18%, respectively. Some cells contained more than one hormone. Porcine C-peptide was detected from 21 days after induction of diabetes but not before. In the pig receiving the most ICCs, blood glucose levels were lowered to nondiabetic levels 109 days after transplantation. Plasma C-peptide levels in response to glucagon in this pig steadily increased after grafting; peak levels were 0, 0.21, 0.45, and 0.52 ng/ml at 4, 21, 49, and 80 days after induction of diabetes compared to 0.09 ng/ml in control diabetic pigs. The secretion of C-peptide in response to oral and intravenous glucose and arginine also was greater than in untransplanted diabetic pigs, the pattern of secretion being consistent with developing fetal beta cells as the source of the C-peptide. Pancreatic insulin content was 0.1 mU/mg, 4% of that in nondiabetic pigs, and the number of beta cells per islet was 3 to 6 compared to 90 in nondiabetic controls.

CONCLUSIONS

ICCs will differentiate and function for up to 111 days when transplanted into outbred immunosuppressed pigs rendered diabetic. Blood glucose levels can be lowered to nondiabetic levels when sufficient numbers of ICCs are grafted.

Ingested interferon-alpha prevents allograft islet transplant rejection

BACKGROUND

Ingested interferon (IFN)-alpha is a biological response modifier in experimental autoimmune encephalomyelitis and multiple sclerosis, and prevents type 1 diabetes in nonobese diabetic mice. Islet transplantation possesses significant potential advantages over whole-gland transplantation because it is simple, may achieve insulin independence, and has clear advantages over exogenous insulin therapy. Therefore, we examined whether ingested IFN-alpha, administered to islet allograft recipients, could prevent islet allograft rejection.

METHODS

Recipient C3H mice (H2k) were made diabetic and either untreated or treated with 10-1000 international units (IU) of ingested murine IFN-alpha daily from day -7 through day +14 after transplantation for a total of 21 days. Seven days after diabetes induction, recipients received allograft islets isolated from C57BL.10 donors (H2b) under the kidney capsule and were followed for overt diabetes via elevated blood glucose.

RESULTS

Control recipients and recipients fed 1000 IU all became diabetic by day 13, whereas mice ingesting IFN-alpha had delayed rejection for up to 27 (10 IU) to 29 days (100 IU) after islet transplantation. Treatment of recipients of islet allografts with ingested IFN-alpha doubles the time period before rejection compared with control mice. The feeding period with daily IFN-alpha was doubled from 21 days to 42 days in total, 7 days before transplantation and 35 days after transplantation.

CONCLUSION

Treatment of recipients of islet allografts with prolonged ingested IFN-alpha prevents rejection in a subset of recipients. Ingested IFN-alpha may prevent rejection if given continuously after transplantation.

Isolation of adult porcine islets of Langerhans

While human islet allotransplantation is limited due to the shortage of donors, pig islet xenotransplantation appears to be a possible alternative. Enzymatic digestion is the method most commonly used for adult pig islet isolation, but since the description of the semiautomated isolation technique in the late 1980s, yields of pig islet isolations have not increased significantly. This review article is intended to collate published information on adult pig islet isolation to provide the reader with a clear overview of the relevant issues in this field, and to detail the current state of the art.