Proliferation of sorted human and rat beta cells

AIMS/HYPOTHESIS

The aim of the study was to determine whether purified beta cells can replicate in vitro and whether this is enhanced by extracellular matrix (ECM) and growth factors.

METHODS

Human beta cells were purified by FACS by virtue of their high zinc content using Newport Green, and excluding ductal and dead cells. Rat beta cells were sorted by autofluorescence or using the same method developed for human cells. Cells were plated on poly-L-lysine or ECMs from rat or human bladder carcinoma cells or bovine corneal ECM and incubated in the presence of BrdU with or without growth factors.

RESULTS

The newly developed method for sorting human beta cells yields a population containing 91.4 +/- 2.8% insulin-positive cells with a low level of spontaneous apoptosis and a robust secretory response to glucose. Beta cells from 8-week-old rats proliferated in culture and this was increased by ECM. Among growth factors, only human growth hormone (hGH) and the glucagon-like peptide-1 analogue liraglutide enhanced proliferation of rat beta cells, with a significant increase on both poly-L-lysine and ECM. By contrast, sorted adult human beta cells from 16 donors aged 48.9 +/- 14.3 years (range 16-64 years) failed to replicate demonstrably in vitro regardless of the substratum or growth factors used.

CONCLUSIONS/INTERPRETATION

These findings indicate that, in our conditions, the fully differentiated human adult insulin-producing beta cell was unable to proliferate in vitro. This has important implications for any attempt to expand cells from pancreases of donors of this age group. By contrast, the rat beta cells used here were able to divide in vitro, and this was enhanced by ECM, hGH and liraglutide.

Expression of peroxisome proliferator-activated receptor gamma (PPARgamma) in normal human pancreatic islet cells

AIMS/HYPOTHESIS

Thiazolidinediones are reported to improve pancreatic islet morphology and beta-cell function in rodents, supporting the hypothesis of a direct action of thiazolidinediones on endocrine islet cells. In this study we examined the expression of the peroxisome proliferator-activated receptor gamma, a nuclear receptor that is activated by naturally occurring fatty acids and synthetic thiazolidinediones, in normal human endocrine pancreatic cells.

METHODS

Human islets were isolated from pancreata harvested in ten brain-dead lean non-diabetic adult donors. We analysed the gene and protein expression of the human peroxisome proliferator-activated receptor gamma and evaluated the effects of peroxisome proliferator-activated receptor gamma agonist on insulin secretion in human islet preparations.

RESULTS

The RT-PCR carried out on total RNA from four distinct human islet preparations demonstrated the presence of peroxisome proliferator-activated receptor gamma mRNA. Western blot analysis showed the consistent expression of peroxisome proliferator-activated receptor gamma protein. Peroxisome proliferator-activated receptor gamma was shown to be present in all three endocrine cell types studied (alpha, beta and delta cells) by immunohistochemistry.

CONCLUSION/INTERPRETATION

We found that peroxisome proliferator-activated receptor gamma is highly expressed in human islet endocrine cells, both at the mRNA and protein levels. These results support the hypothesis of a direct influence of peroxisome proliferator-activated receptor gamma agonist on human pancreatic endocrine cells.

Persistent infection of human pancreatic islets by coxsackievirus B is associated with alpha interferon synthesis in beta cells

The interactions of coxsackievirus B3 (CVB3), CVB4E2 (diabetogenic), and CVB4JBV (nondiabetogenic) strains with human pancreatic islets from eight adult brain-dead donors were investigated. Persistent replication of viruses in human islets was proved by detection of viral RNA by in situ hybridization, VP1 capsid protein by immunofluorescence (IF) staining, negative-strand viral RNA by reverse transcription-PCR in extracted RNA from islets, and release of infectious particles up to 30 days after infection without obvious cytolysis. By double IF staining, glucagon-containing alpha cells and insulin-containing beta cells were shown to be susceptible to CVB. The persistence of CVB3 and CVB4 in islet cells was associated with the chronic synthesis of alpha interferon (IFN-alpha), as evidenced by the detection of IFN-alpha mRNA and immunoreactive IFN-alpha with antiviral activity. By double IF staining, IFN-alpha was detected in insulin-producing beta cells only. Experiments with neutralizing anti-coxsackievirus and adenovirus receptor (CAR) antibodies provided evidence that CAR was expressed by alpha and beta cells and that it played a role in the infection of these cells with CVB and the consecutive IFN-alpha expression in beta cells. The viral replication and the expression of IFN-alpha in islets were not restricted to the CVB4E2 diabetogenic strain and did not depend on the genetic background of the host. The neutralization of endogenous IFN-alpha significantly enhanced the CVB replication in islet cells and resulted in rapid destruction of islets. Thus, human beta cells can harbor a persistent CVB infection, and CVB-induced IFN-alpha plays a role in the initiation and/or maintenance of chronic CVB infection in human islets.

Identification and purification of functional human beta-cells by a new specific zinc-fluorescent probe

Pancreatic beta-cells contain large amounts of zinc. We took advantage of this to try to localize, quantify, and isolate insulin-producing cells from islet preparations. Our study was designed to identify a non-toxic zinc-sensitive fluorescent probe able to selectively label labile zinc in viable beta-cells and to exhibit excitation and emission wavelengths in the visible spectrum, making this technique exploitable by most instruments. We tested Newport Green, a probe excitable at 485 nm with a dissociation constant in the micromolar range corresponding to a low affinity for zinc. The loading of the lipophilic esterified form of Newport Green was easy, rapid, specific, and non-toxic to cells. Confocal microscopy highlighted an intense fluorescence associated with secretory granules. Regression analyses showed a good relationship between zinc fluorescence and islet number (r = 0.98) and between zinc fluorescence and insulin content (r = 0.81). The determination of Zn fluorescence per DNA enabled us to assess the quality of the different islet preparations intended for islet allografting in terms of both purity and viability. Cell sorting of dissociated Newport Green-labeled cells resulted in a clear separation of beta-cells, as judged by insulin content per DNA and immunocytochemical analysis. This zinc probe, the first able to specifically label living cells in the visible spectrum, appears very promising for beta-cell experimentation, both clinically and for basic research.

Adenovirus-mediated catalase gene transfer reduces oxidant stress in human, porcine and rat pancreatic islets

Susceptibility of pancreatic islets to oxidant stress may affect islet viability and contribute to primary non function of allo- or xenogenic grafts. We investigated the influence of overexpression of catalase (CAT) on the viability of human, porcine and rat islets, as well as INS-1 beta-cell line. Islets were transfected with a replication-deficient adenovirus vector containing human CAT cDNA under the control of the adenovirus major late promoter (AdCAT) or a vector containing no foreign gene (AdNull) and used as a control. Oxidant stress was induced 48 h later by xanthine oxidase-hypoxanthine (XO 25 mU/ml, HX 0.5 mmol/l) or hydrogen peroxide (100 or 250 micromol/l). Islet cell viability was assessed 72 h after CAT transfer by 4-[3-(4-Idophenyl)-2-(4 nitrophenyl)-2H-5-tetrazolio]-1,2,benzene disulphonate (WST-1) test. Baseline catalase activity was three to fourfold lower in porcine than in human islets. CAT activity was reproducibly increased 2.5- to 7-fold in AdCAT infected islets, at least for 13 days. Overall, AdCAT conferred on human and pig islets a protection of 26.1 +/- 6.1 and 21.2 +/- 9.8% on XOHX injury and 35.4 +/- 4.2 and 57.9 +/- 10.5% on H2O2 stress. Similarly, rat islet cells and INS-1 cells were protected on XOHX stress by 17.8 +/- 2.3 and 30.8 +/- 8.7%, respectively. AdNull had no effect. Basal and stimulated insulin secretion was preserved in AdCAT-transfected human islets despite a XOHX challenge. This study validates adenovirus-mediated catalase gene transfer as a realistic approach to reduce non specific inflammation effects on human or porcine islet grafts. Moreover the relevance of defense mechanisms, previously suggested in human islets, is here illustrated in porcine islets.

Adult human cytokeratin 19-positive cells reexpress insulin promoter factor 1 in vitro: further evidence for pluripotent pancreatic stem cells in humans

Human pancreatic cells with a typical ductal phenotype and potential to proliferate can be obtained in vitro, but the differentiation capacity of these putative human pancreatic stem cells remains to be documented. We investigated the protein and mRNA expression of insulin promoter factor 1 (IPF-1) (or pancreas/duodenal homeobox 1), a transcription factor critical for pancreatic development and endocrine cell neogenesis, in human pancreatic ductal cells derived from cultured exocrine tissue. In vitro, exocrine cells rapidly adhered (within 12 h) and were de-/transdifferentiated to ductal cells after 3 days with a dramatic loss of amylase protein (n = 4, 92 +/- 3.3%, P < 0.05 vs. day 1) and a simultaneous increase of ductal cytokeratin 19 protein (n = 4, 3.4-fold on day 3 and 7-fold on day 9, P < 0.05 vs. day 1). IPF-1 protein and mRNA levels were low to undetectable in exocrine preparations before culture. After 2 days of culture, a 3.2-fold increase in IPF-1 protein was observed, corresponding to the characteristic 46-kDa protein in Western blots. Reverse transcriptase-polymerase chain reaction confirmed a 10.5-fold increase in IPF-1 mRNA levels after 3 days of culture (n = 5, P < 0.001 vs. day 1). Double immunocytochemistry showed direct evidence that IPF-1 appeared during culture in these exocrine-derived ductal cells (cytokeratin 7-positive) and was not merely in contaminating endocrine cells (chromogranin A-positive). In conclusion, we describe herein the first converging evidence on both the molecular and protein level that human cells with a typical ductal phenotype derived ex vivo from pancreatic exocrine tissue (obtained from healthy donors) can reexpress IPF-1 in culture, suggesting their pancreatic precursor/stem cell potential.

Hepatocyte nuclear factor 4 alpha isoforms originated from the P1 promoter are expressed in human pancreatic beta-cells and exhibit stronger transcriptional potentials than P2 promoter-driven isoforms

The nuclear receptor hepatocyte nuclear factor (HNF) 4 alpha is involved in a transcriptional network and plays an important role in pancreatic beta-cells. Mutations in the HNF4 alpha gene are correlated with maturity-onset diabetes of the young 1. HNF4 alpha isoforms result from both alternative splicing and alternate usage of promoters P1 and P2. It has recently been reported that HNF4 alpha transcription is driven almost exclusively by the P2 promoter in pancreatic islets. We observed that transcripts from both P1 and P2 promoters were expressed in human pancreatic beta-cells and in the pancreatic beta-cell lines RIN m5F and HIT-T15. Expression of HNF4 alpha proteins originating from the P1 promoter was confirmed by immunodetection. Due to the presence of the activation function module AF-1, HNF4 alpha isoforms originating from the P1 promoter exhibit stronger transcriptional activities and recruit coactivators more efficiently than isoforms driven by the P2 promoter. Conversely, activities of isoforms produced by both promoters were similarly repressed by the corepressor small heterodimer partner. These behaviors were observed on the promoter of HNF1 alpha that is required for beta-cell function. Our results highlight that expression of P1 promoter-driven isoforms is important in the control of pancreatic beta-cell function.

Ductal cyst formation in collagen-embedded adult human islet preparations. A means to the reproduction of nesidioblastosis in vitro

Neogenesis of endocrine islets from ductal epithelium termed nesidioblastosis has been described in vivo after various experimental conditions (90% pancreatectomy or pancreas wrapping in the rodent) and in clinical pathologies. In the adult regenerating pancreas, a proliferation and organization of ductal epithelium into tubular structures precedes its differentiation into endocrine cells. Reproduction of nesidioblastosis in vitro may provide a novel approach to human islet propagation in vitro. With this aim, adult human islet preparations were cultured in diverse three-dimensional (3D) gels in the presence of serum. After 3-5 days in rat tail collagen gels, proliferating (bromodeoxyuridine-positive) cystic structures appeared associated with islets and as isolated spheres. Percentage labeling indexes of the cysts were 4.1, 18.7, 15.4, and 13.3% after 3, 5, 7, and 10 days of culture, respectively. Immunohistochemistry confirmed the ductal (carbohydrate antigen 19-9) and epithelial (keratin-1) nature of the cysts. No cysts were formed in agarose gels or Vitrogen 100, whereas the cyst number was increased by the quantity of serum (20% > 10%) and gels rich in extracellular matrix components and growth factors (Matrigel). The latter lead to tubular networks. Single endocrine islet cells were observed in the ductal cysts after 7 (2.8%) to 10 (5.6%) days in rat tail collagen. Our observations paralleled the changes characteristic of the regenerating pancreas in vivo. 3D culture may permit the identification of matrix and media constituents promoting the neogenesis of islets and may be the means to increase the mass of endocrine tissue obtained from adult cadaveric pancreases for transplantation.

Adenylyl cyclase 8 is central to glucagon-like peptide 1 signalling and effects of chronically elevated glucose in rat and human pancreatic beta cells

AIMS/HYPOTHESIS

Glucose and incretins regulate beta cell function, gene expression and insulin exocytosis via calcium and cAMP. Prolonged exposure to elevated glucose (also termed glucotoxicity) disturbs calcium homeostasis, but little is known about cAMP signalling. We therefore investigated long-term effects of glucose on this pathway with special regard to the incretin glucagon-like peptide 1 (GLP-1).

METHODS

We exposed INS-1E cells and rat or human islets to different levels of glucose for 3 days and determined functional responses in terms of second messengers (cAMP, Ca(2+)), transcription profiles, activation of cAMP-responsive element (CRE) and secretion by measuring membrane capacitance. Moreover, we modulated directly the abundance of a calcium-sensitive adenylyl cyclase (ADCY8) and GLP-1 receptor (GLP1R).

RESULTS

GLP-1- or forskolin-mediated increases in cytosolic calcium, cAMP-levels or insulin secretion were largely reduced in INS-1E cells cultured at elevated glucose (>5.5 mmol/l). Statistical analysis of transcription profiles identified cAMP pathways as major targets regulated by glucose. Quantitative PCR confirmed these findings and unravelled marked downregulation of the calcium-sensitive adenylyl cyclase ADCY8 also in rat and in human islets. Re-expression of ADCY8, but not of the GLP1R, recovered GLP-1 signalling in glucotoxicity in INS-1E cells and in rat islets. Moreover, knockdown of this adenylyl cyclase showed that GLP-1-induced cAMP generation, calcium signalling, activation of the downstream target CRE and direct amplification of exocytosis by cAMP-raising agents (evaluated by capacitance measurement) proceeds via ADCY8.

CONCLUSIONS/INTERPRETATION

cAMP-mediated pathways are modelled by glucose, and downregulation of the calcium-sensitive ADCY8 plays a central role herein, including signalling via the GLP1R.

Non-esterified fatty acids are deleterious for human pancreatic islet function at physiological glucose concentration

AIMS/HYPOTHESIS

Whether excess glucose (glucotoxicity) and excess non-esterified fatty acids (lipotoxicity) act synergistically or separately to alter beta-cell function on Type 2 diabetes remains controversial. We examined the influence of non-esterified fatty acids, with or without concomitant increased glucose concentrations, on human islet function and on the expression of genes involved in lipid metabolism.

METHODS

Human islets isolated from non-diabetic and non-obese donors were cultured with 5.5, 16 or 30 mmol/l glucose, and when appropriate with 1 or 2 mmol/l non-esterified fatty acids. After 48 h, glucose-stimulated insulin secretion, insulin content, triglyceride content and expression of different genes were evaluated.

RESULTS

Non-esterified fatty acids decreased glucose-stimulated insulin secretion, insulin content and increased triglyceride content of human isolated islets, independently from the deleterious effect of glucose. Increased glucose concentrations also decreased glucose-stimulated insulin secretion and insulin content, but had no influence on triglyceride content. Glucose-stimulated insulin secretion of islets appeared to be significantly correlated with their triglyceride content. Glucose and non-esterified fatty acids modified the gene expression of carnitine palmitoyltransferase-I, acetyl-CoA carboxylase, acyl-CoA oxidase and uncoupling protein 2.

CONCLUSION/INTERPRETATION

In our model of isolated human islets, increased glucose and non-esterified fatty acids separately reproduced the two major beta-cell alterations observed in vivo, i.e. loss of glucose-stimulated insulin secretion and reduction in islet insulin content. Our results also suggest that this deleterious effect was, at least in part, mediated by modifications in lipid metabolism gene expression.

TCF7L2 rs7903146 impairs islet function and morphology in non-diabetic individuals

AIMS/HYPOTHESIS

Transcription factor 7-like 2 (TCF7L2) is a Wnt-signalling-associated transcription factor. Genetic studies have clearly demonstrated that DNA polymorphisms within TCF7L2 confer the strongest known association with increased risk of type 2 diabetes. However, the impact of the TCF7L2 type-2-diabetes-associated rs7903146 T allele on biological function and morphology of human pancreatic islets is unknown.

METHODS

Paraffin sections of pancreases from 187 brain-deceased donors (HbA(1c) <6.5% [48 mmol/mol]) were used to genotype the TCF7L2 variant rs7903146 and evaluate its impact on islet morphology and alpha and beta cell subpopulations following immunostaining for glucagon and C-peptide. Following islet isolation, we investigated the correlation between TCF7L2 genotype and in vitro islet functional variables from our in-house pancreatic database.

RESULTS

TCF7L2 rs7903146 (T/T) was associated with reduced basal and glucose-stimulated insulin secretion in isolated human islets, and reduced islet density in whole pancreas. Morphological analysis demonstrated islet size was increased in T/T carriers. Furthermore, rs7903146 was associated with an increased glucagon/C-peptide ratio, especially in bigger islets.

CONCLUSION/INTERPRETATION

The TCF7L2 variant rs7903146 risk allele is associated with impaired insulin secretion, reduction of total islet number and quantitative as well as qualitative morphological changes in human islets. Understanding how the TCF7L2 genotype modulates its activity and how TCF7L2 impacts the islet morphology may aid the design of new therapeutic approaches for the treatment of type 2 diabetes.

Contribution of adenoviral-mediated superoxide dismutase gene transfer to the reduction in nitric oxide-induced cytotoxicity on human islets and INS-1 insulin-secreting cells

AIMS/HYPOTHESIS

Vulnerability of pancreatic islets to oxygen free radicals and nitric oxide contributes to islet transplantation obstacles. This susceptibility can be linked to the low expression levels of antioxidant enzymes in islets. Our aim was to investigate the effect of overexpressing Cu/Zn superoxide dismutase in human islets through a simple procedure on the cytotoxic effects of two nitric oxide donors: 3-morpholinosydnonimine (SIN-1) and S-Nitroso-N-acetyl-D,L-penicillamine (SNAP).

METHODS

Cultured human islets and INS-1 rat-derived insulin-secreting cells were transfected by an E1-deleted adenovirus carrying Cu/Zn SOD cDNA under the control of a cytomegalovirus (CMV) promoter (AdSOD). The viability of the cells was tested by the WST-1 assay (Roche, Indianapolis, Ind., USA).

RESULTS

The AdSOD procedure allowed SOD activity to increase by twofold to threefold for 2 to 8 days following transfection. Adenovirus-driven SOD overexpression was associated with a significant reduction of SIN-1-induced cytotoxicity on human islets (69.9 +/- 10.5% protection at 200 micromol/l and 40.5 +/- 8.9% protection at 400 micromol/l) and INS-1 cells (82.2 8.8% protection at 200 micromol/l and 31.1 +/- 5.8% protection at 400 micromol/l). Protection against increasing doses of SNAP was AdSOD dose-dependent. Transfected islets released significantly more insulin than control islets in glucose-theophylline-stimulated conditions, without or following exposure to SNAP.

CONCLUSIONS/INTERPRETATION

We thus established that adenoviral-induced overexpression of Cu/Zn SOD can be beneficial to human islet endocrine function and resistance to nitric oxide cytotoxicity. These data could be relevant for the development of new strategies aimed at preventing NO-induced beta-cell damage in an islet transplantation setting.

Beneficial effect of 1,25 dihydroxyvitamin D3 on cytokine-treated human pancreatic islets

We examined whether 1,25 dihydroxyvitamin D(3) (1,25 D(3)), the active form of vitamin D involved in the regulation of the immune system, may also protect human pancreatic islet cells from destruction induced by cytokines. In this study, we specifically investigated the effect of 1,25 D(3) on oxidative stress and major histocompatibility complex (MHC) induction, both implicated in cytokine-induced islet cell dysfunction and destruction. We also investigated the effects of 1,25 D(3) on interleukin (IL)-6, a pleiotropic cytokine implicated in the pathogenesis of immunoinflammatory disorders. Human pancreatic islets, isolated from heart-beating donors, were treated with a combination of three cytokines, IL-1beta+tumor necrosis factor alpha+interferon gamma, in the presence or absence of vitamin D, and compared with with untreated control cells. Metabolic activity was assessed by cell viability and insulin content. Oxidative stress was estimated by heat shock protein 70 (hsp70) expression, cell manganese superoxide dismutase (MnSOD) activity and nitrite release, a reflexion of nitric oxide (NO) synthesis. Variation of immunogenicity of islet preparations was determined by analysis of the MHC class I and class II transcripts. Inflammatory status was evaluated by IL-6 production. After 48 h of contact with cytokines, insulin content was significantly decreased by 40% but cell viability was not altered. MHC expression significantly increased six- to sevenfold as well as NO and IL-6 release (two- to threefold enhancement). MnSOD activity was not significantly induced and hsp70 expression was not affected by the combination of cytokines. The addition of 1,25 D(3) significantly reduced nitrite release, IL-6 production and MHC class I expression which then became not significantly different from controls. These results suggest that the effect of 1,25 D(3) in human pancreatic islets cells may be a reduction of the vulnerability of cells to cytotoxic T lymphocytes and a reduction of cytotoxic challenge. Hence, 1,25 D(3) might play a role in the prevention of type 1 diabetes and islet allograft rejection.

Evaluation of alternative sites for islet transplantation in the minipig: interest and limits of the gastric submucosa

Since the introduction of glucocorticoid-free immunosuppressive regimens, islet transplantation offers a less invasive alternative to pancreas transplantation. However, complications associated with intraportal islet injection and the progressive functional decline of intrahepatic islets encourage the exploration of alternative sites. Herein we evaluated, in the minipig, the use of the gastric submucosa (GS; group 1, n = 5) for islet transplantation compared with the kidney capsule (KC; group 2, n = 5). Subsequently we attempted to improve the vascularization of the submucosal graft (group 3, n = 5) by the addition of an extracellular matrix rich in growth factors (Matrigel). One month after grafting, we evaluated transplanted islet function in vivo and in vitro. Our study showed better function of islets engrafted in the GS than in the KC (P < .05). Despite the growth factors, Matrigel did not offer a more suitable environment to further improve engraftment (group 3, P < .05). Thus, even if the liver remains the gold standard, the GS represents a potential islet engraftment site, confirming the data obtained in vitro and in the rodent. Offering easy access by endoscopy, this site could constitute an interesting alternative for experimental studies in large mammals and, eventually, for clinical application.

TCF7L2 promotes beta cell regeneration in human and mouse pancreas

AIMS/HYPOTHESIS

Diabetes is characterised by loss and dysfunction of the beta cell. A major goal of diabetes therapy is to promote the formation of new beta cells. Polymorphisms of T cell factor 7-like 2 (TCF7L2) are associated with type 2 diabetes, negatively regulating beta cell survival and function. Here, we provide evidence for a role of TCF7L2 in beta cell proliferation and regeneration.

METHODS

Pancreatic sections from three mouse models (high-fat diet, exendin-4 and streptozotocin-treated mice) and from healthy individuals and patients with type 2 diabetes were used to investigate the association of beta cell regeneration and TCF7L2 levels. To analyse a direct effect of TCF7L2 on duct cell to beta cell conversion, TCF7L2 was overexpressed in isolated exocrine cells.

RESULTS

TCF7L2 levels correlated with beta cell compensation during high-fat diet feeding. TCF7L2 was increased together with pancreatic duct cell proliferation and differentiation. Small islet-like cell clusters (ICCs) that contained TCF7L2 originated in the vicinity of the ductal epithelium. In human isolated exocrine tissue, TCF7L2 overexpression induced proliferation of pancreatic duct cells and ICC formation next to duct cells, an effect dependent on the JAK2/STAT3 pathway.

CONCLUSIONS/INTERPRETATION

The present study demonstrates that TCF7L2 overexpression fosters beta cell regeneration. Our findings imply correlation of TCF7L2 levels and new beta cell formation.

Adaptive changes of human islets to an obesogenic environment in the mouse

AIMS/HYPOTHESIS

In this study, we used an immunodeficient mouse model to explore, in vivo, the longitudinal adaptation of human islets to an obesogenic environment.

METHODS

Non-diabetic Rag2 (-/-) mice (n = 61) were transplanted with human islets (400 islet equivalents [IEQ]) from six pancreases: four non-diabetic and two with overt metabolic dysfunction (older, high HbA(lc) or history of diabetes). Animals were fed for 12 weeks with a control or high-fat diet (HFD), and followed for weight, serum triacylglycerol, fasting blood glucose and human C-peptide. After the mice were killed, human grafts and the endogenous pancreas were analysed for endocrine volume, distribution of beta and alpha cells, and proliferation.

RESULTS

Transplanted mice on an HFD gained significantly more weight (p < 0.001) and had higher fasting glycaemia (2-12 weeks; p = 0.0002) and consistently higher fasting human C-peptide levels (2-12 weeks; p = 0.04) compared with those on the control diet. Histology demonstrated doubling of human islet graft volume at 12 weeks in animals on the HFD and increased beta cell volume (p < 0.001), but no change in alpha cell volume. Human islet function (hyperbolic product HOMA2%BS) at 12 weeks was four times lower in HFD animals (p < 0.001 vs controls) because of insufficient beta cell adaptation to decreased (70%) sensitivity (HOMA%S). Human islets obtained from donors with metabolic dysfunction failed to adapt to the HFD.

CONCLUSIONS/INTERPRETATION

This longitudinal study provides direct evidence that human islets adapt both endocrine and beta cell mass, function and gene expression to obesity in vivo. The present model will facilitate the identification of mechanisms by which human islets adapt to obesity in vivo and the cell type(s) responsible, and factors predisposing human beta cells to decompensation.

Treating diabetes with islet transplantation: lessons from the past decade in Lille

Type 1 diabetes (T1D) is due to the loss of both beta-cell insulin secretion and glucose sensing, leading to glucose variability and a lack of predictability, a daily issue for patients. Guidelines for the treatment of T1D have become stricter as results from the Diabetes Control and Complications Trial (DCCT) demonstrated the close relationship between microangiopathy and HbA1c levels. In this regard, glucometers, ambulatory continuous glucose monitoring, and subcutaneous and intraperitoneal pumps have been major developments in the management of glucose imbalance. Besides this technological approach, islet transplantation (IT) has emerged as an acceptable safe procedure with results that continue to improve. Research in the last decade of the 20th century focused on the feasibility of islet isolation and transplantation and, since 2000, the success and reproducibility of the Edmonton protocol have been proven, and the mid-term (5-year) benefit-risk ratio evaluated. Currently, a 5-year 50% rate of insulin independence can be expected, with stabilization of microangiopathy and macroangiopathy, but the possible side-effects of immunosuppressants, limited availability of islets and still limited duration of insulin independence restrict the procedure to cases of brittle diabetes in patients who are not overweight or have no associated insulin resistance. However, various prognostic factors have been identified that may extend islet graft survival and reduce the number of islet injections required; these include graft quality, autoimmunity, immunosuppressant regimen and non-specific inflammatory reactions. Finally, alternative injection sites and unlimited sources of islets are likely to make IT a routine procedure in the future.

Islet survival and function following intramuscular autotransplantation in the minipig

The liver may not be an optimal site for islet transplantation due to obstacles by an instant blood-mediated inflammatory response (IBMIR), and low revascularization of transplanted islets. Therefore, intramuscular islet transplantation (IMIT) offers an attractive alternative, based on its simplicity, enabling easier access for noninvasive graft imaging and cell explantation. In this study, we explored the outcome of autologous IMIT in the minipig (n = 30). Using the intramuscular injection technique, we demonstrated by direct histological evidence the rapid revascularization of islets autotransplanted into the gracilius muscle. Islet survival assessment was performed using immunohistochemistry staining for insulin and glucagon up to a period of 6 months. Furthermore, we showed the crucial role of minimizing mechanical trauma to the myofibers and limiting exocrine contamination. Intramuscular islet graft function after transplantation was confirmed by documenting the acute insulin response to intravenous glucose in 5/11 pancreatectomized animals. Graft function after IMIT remained however significantly lower than the function measured in 12 out of 18 minipigs who received a similar islet volume in the liver through intraportal infusion. Collectively, these results demonstrated in a clinically relevant preclinical model, suggest IMIT as a promising alternative to intraportal infusion for the transplantation of β cells in certain medical situations.

Acute insulin response to arginine in deceased donors predicts the outcome of human islet isolation

Despite a stringent donor selection, human islet isolation remains frustratingly unpredictable. In this study, we measured acute insulin response to arginine (AIRarg), an in vivo surrogate measure of islet mass, in 29 human deceased donors before organ donation, and correlated values with the outcome of islet isolation. Thirteen isolations (45%) met the threshold for clinical islet transplantation. Among all measured donor characteristics, the only discriminating variable between successful or unsuccessful isolations was donor AIRarg (p < 0.01). Using a threshold of 55 microIU/mL (ROC curve AUC: 72%), isolation was successful in 12/19 donors with high AIRarg and in 1/10 donors with low AIRarg (p < 0.001). The negative and positive predictive values were 90 and 63%, respectively. If used to select donors in the entire cohort, AIRarg would have increased our success rate by 40% and avoided 56% of unsuccessful isolations while missing only 8% of successful preparations. Our results suggest that donor AIRarg is markedly superior to body mass index (BMI) and other criteria currently used to predict isolation outcome. If routinely performed in deceased donors, this simple test could significantly reduce the failure rate of human islet isolation.

Mixed ductal-endocrine carcinoma of the pancreas: a possible pathogenic mechanism for arrhythmogenic right ventricular cardiomyopathy

We describe herein a case of a mixed ductal-endocrine pancreatic carcinoma. Rare cases of mixed pancreatic tumors have been described, with endocrine and exocrine components each making up a significant proportion of the neoplasm; to our knowledge, only one case has been reported with a mixed liver metastasis. In our case, ductal and endocrine cells were intimately admixed in the primary tumor and in a peripancreatic lymph node metastasis, diagnosed by standard light microscopy and double immunostaining for cytokeratin 19 and synaptophysin. The endocrine component was immunoreactive for somatostatin. Tumors with admixed endocrine and exocrine components support the hypothesis of a common endodermal histogenesis for the ductal and endocrine cells in the human pancreas.

Acute insulin response of donors is correlated with pancreatic islet isolation outcome in the pig

AIMS/HYPOTHESIS

Unpredictability of islet isolation outcome remains a frustrating and costly issue in the clinical implementation of islet transplantation. The aim of this experimental study was to test the hypothesis that the donor's insulin secretory reserve, an in vivo surrogate of functional pancreatic mass, is correlated with the outcome of islet isolation.

METHODS

Insulin secretory reserve was evaluated in 28 healthy adult minipigs prior to pancreatectomy and islet isolation. Blood glucose and insulinaemia were measured before and 1, 3, 5, 10, 15, 30, 60 and 90 min after glucose infusion. Following total pancreatectomy, islet isolation was performed according to Ricordi's semi-automated method, and the total number of islets obtained was determined. Fasting blood glucose, insulinaemia, acute insulin response (AIR), maximal insulinaemia and the glucose decay constant (K(G)) were calculated, and possible associations with the outcome of islet isolation were assessed.

RESULTS

AIR and maximal insulinaemia after glucose injection were correlated with the outcome of islet isolation (p<0.01). Mean values for AIR and maximal insulinaemia were significantly different between animals in which islet isolation was successful (n=11) vs those in which it was unsuccessful (n=17) (77.6+/-13.7 microU/ml vs 42.3+/-7.8 microU/ml, p<0.05; 144.7+/-21.6 microU/ml vs 71.9+/-10.4 microU/ml, p<0.05, respectively).

CONCLUSIONS/INTERPRETATION

This study suggests that the donor's pancreatic endocrine mass, as estimated by AIR, is a major determinant of the outcome of islet isolation in large mammals. Our results may explain the frustrating variability of human islet isolation outcome and could lead to a new approach for optimising the selection of brain-dead and/or living pancreas donors.

Purity of islet preparations and 5-year metabolic outcome of allogenic islet transplantation

In allogenic islet transplantation (IT), high purity of islet preparations and low contamination by nonislet cells are generally favored. The aim of the present study was to analyze the relation between the purity of transplanted preparations and graft function during 5 years post-IT. Twenty-four patients with type 1 diabetes, followed for 5 years after IT, were enrolled. Metabolic parameters and daily insulin requirements were compared between patients who received islet preparations with a mean purity <50% (LOW purity) or ≥50% (HIGH purity). We also analyzed blood levels of carbohydrate antigen 19-9 (CA 19-9)-a biomarker of pancreatic ductal cells-and glucagon, before and after IT. At 5 years, mean hemoglobin A1c (HbA1c levels) (P = .01) and daily insulin requirements (P = .03) were lower in the LOW purity group. Insulin independence was more frequent in the LOW purity group (P < .05). CA19-9 and glucagon levels increased post-IT (P < .0001) and were inversely correlated with the degree of purity. Overall, our results suggest that nonislet cells have a beneficial effect on long-term islet graft function, possibly through ductal-to-endocrine cell differentiation. ClinicalTrial.gov NCT00446264 and NCT01123187.

MnTMPyP, a metalloporphyrin-based superoxide dismutase/catalase mimetic, protects INS-1 cells and human pancreatic islets from an in vitro oxidative challenge

AIMS

Pancreatic islets can be lost early following allotransplantation from oxidative stress. Antioxidant enzyme overexpression could confer a beneficial effect on islets exposed to reactive oxygen species (ROS) and nitrogen species. Here, we tested the effect of MnTMPyP, a superoxide dismutase/catalase mimetic.

METHODS

INS-1 insulin-secreting cells or human islets were cultured with MnTMPyP and exposed to a superoxide donor (the hypoxanthine/xanthine oxidase (HX/XO) system), a nitric oxide donor [3-morpholinosydnonimine (SIN-1)] or menadione. Viability of INS-1 cells was assessed by WST-1 colorimetric assay and FACS analysis (Live/Dead test). ROS production was determined using fluorescent probes. Islet viability was estimated by WST-1 assay and endocrine function by static incubation.

RESULTS

Following MnTMPyP treatment, ROS production in INS-1 cells was reduced by 4- to 20-fold upon HX/XO challenge and up to 2-fold upon SIN-1 stress. This phenomenon correlated with higher viability measured by WST-1 or Live/Dead test. MnTMPyP preserved islet viability upon exposure to SIN-1 or menadione but not upon an HX/XO challenge. Similarly, decrease in insulin secretion tended to be less pronounced in MnTMPyP-treated islets than in control islet when exposed to SIN-1, but no changes were noticed during an HX/XO stress.

CONCLUSIONS

MnTMPyP was able to improve the viability of INS-1 cells and human islets exposed to oxidative challenges in vitro. Protection of INS-1 cells could be as high as 90%. This agent is therefore potentially attractive in situations involving the overproduction of ROS, such as islet transplantation.