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ABSTRACT: Immunological barriers still preclude clinical xenotransplantation. The protective role of CD4(+)CD25(+)Foxp3(+) T-regulatory cells (Treg) in allotransplantation is well described and, therefore, could represent a promising therapeutical tool for xenotransplantation. This review addresses the latest findings on Treg in xenotransplantation research.
In vivo, costimulation blockade-based strategies including anti-CD154 monoclonal antibodies (mAbs) in combination with rapamycin or anti-LFA-1 mAb prolonged both concordant and discordant islets xenografts survival in a Treg-dependent manner. In vitro, IL-10 secretion was shown to be critical for the suppression of xenogeneic responses mediated by Treg. Moreover, transgenic expression of inducible costimulator-immunoglobulin or PD-L1 on porcine endothelial cells inhibited human T-cell proliferation in vitro and was associated with the induction of Treg and IL-10 secretion. CXCR3 mediated the recruitment of Treg to pig endothelium. Finally, the recruitment of human Treg was enhanced by the immobilization of human CCL17 on pig endothelium.
There is increasing evidence for the potential of CD4(+)CD25(+)Foxp3(+) Treg to protect xenografts. Induction of Treg in recipients and/or recruitment of human Treg to pig endothelium may represent novel strategies to prevent cell-mediated rejection in pig-to-human xenotransplantation.
Current opinion in organ transplantation 02/2012; 17(2):155-61. · 1.22 Impact Factor
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ABSTRACT: The aim of this study was to assess the expression of different types of cadherins in human islets and their role in human β-cell apoptosis. Expression of E-, N-, and P-cadherins was studied by immunofluorescence on pancreas sections and islet cells, and by Western blotting on protein extracts of isolated islets and islet cells. The effects of specific cadherins on cell adhesion and apoptosis were studied using chimeric proteins containing functional E-, N-, or P-cadherin ectodomains fused to Fc fragment of Ig (E-cad/Fc, N-cad/Fc, and P-cad/Fc) and immobilized on glass substrate. β-Cells were identified by immunofluorescence for insulin and apoptotic cells by terminal deoxynucleotide transferase-mediated 2'-deoxyuridine, 5'-triphosphate nick-end labeling. By immunofluorescence, we showed that E- and N-, and not P-, cadherins were expressed at the surface of islet cells. By triple staining, we showed that E-cadherin was expressed at similar extent in β- and α-cells, whereas N-cadherin was preferentially expressed in β-cells. These results were confirmed by Western blot analysis using protein extracts from fluorescence-activated cell sorting-sorted β- and non-β-cells. Adhesion tests showed that the affinity of islet cells for E-cad/Fc and N-cad/Fc and not for P-cad/Fc was increased compared with control. By terminal deoxynucleotide transferase-mediated 2'-deoxyuridine, 5'-triphosphate nick-end labeling, we showed that the percentage of apoptotic cells was lower in aggregated β-cells compared with single β-cells and that attachment to E-cad/Fc and N-cad/Fc and not to P-cad/Fc decreased apoptosis of single β-cells compared with control. Our results show that at least E- and N-cadherins are expressed at the surface of human β-cells and that these adhesion molecules are involved in the maintenance of β-cell viability.
Endocrinology 12/2011; 152(12):4601-9. · 4.46 Impact Factor
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Yannick D Muller,
Déla Golshayan,
Driss Ehirchiou,
Jean Christophe Wyss,
Laurianne Giovannoni,
Raphael Meier,
Véronique Serre-Beinier,
Gisella Puga Yung,
Philippe Morel,
Leo H Bühler,
Jörg D Seebach
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ABSTRACT: Streptozotocin (STZ) is the most widely used diabetogenic agent in animal models of islet transplantation. However, the immunomodifying effects of STZ and the ensuing hyperglycemia on lymphocyte subsets, particularly on T regulatory cells (Tregs), remain poorly understood.
This study evaluated how STZ-induced diabetes affects adaptive immunity and the consequences thereof on allograft rejection in murine models of islet and skin transplantation. The respective toxicity of STZ and hyperglycemia on lymphocyte subsets was tested in vitro. The effect of hyperglycemia was assessed independently of STZ in vivo by the removal of transplanted syngeneic islets, using an insulin pump, and with rat insulin promoter diphtheria toxin receptor transgenic mice.
Early lymphopenia in both blood and spleen was demonstrated after STZ administration. Direct toxicity of STZ on lymphocytes, particularly on CD8(+) cells and B cells, was shown in vitro. Hyperglycemia also correlated with blood and spleen lymphopenia in vivo but was not lymphotoxic in vitro. Independently of hyperglycemia, STZ led to a relative increase of Tregs in vivo, with the latter retaining their suppressive capacity in vitro. The higher frequency of Tregs was associated with Treg proliferation in the blood, but not in the spleen, and higher blood levels of transforming growth factor-β. Finally, STZ administration delayed islet and skin allograft rejection compared with naive mice.
These data highlight the direct and indirect immunosuppressive effects of STZ and acute hyperglycemia, respectively. Thus, these results have important implications for the future development of tolerance-based protocols and their translation from the laboratory to the clinic.
Diabetes 07/2011; 60(9):2331-40. · 8.29 Impact Factor
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Nadja Niclauss,
Domenico Bosco,
Philippe Morel,
Sandrine Demuylder-Mischler,
Coralie Brault,
Laure Milliat-Guittard,
Cyrille Colin,
Geraldine Parnaud, Yannick D Muller,
Laurianne Giovannoni,
Raphael Meier,
Christian Toso,
Lionel Badet,
Pierre-Yves Benhamou,
Thierry Berney
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ABSTRACT: It has been suggested that the age of human organ donors might influence islet isolation and transplantation outcome in a negative way due to a decrease of in vivo function in islets isolated from older donors.
We retrospectively analyzed 332 islet isolations according to donor age. We determined isolation outcome by islet yields, transplantation rates, and [beta]-cell function in vitro. Transplanted patients were divided into two groups depending on donor age (n=25 and n=31 patients for <=45- and >45-year-old donors, respectively). We assessed islet graft function by C-peptide/glucose ratio, [beta] score, secretory units of islets in transplantation index, and insulin independence rate at 1, 6, and 12 months after transplantation.
There was no difference in islet yields between the two groups (251,900+/-14,100 and 244,600+/-8400 islet equivalent for <=45- and >45-year-old donors, respectively). Transplantation rates and stimulation indices were similar in both groups as well. All islet graft function parameters were significantly higher at 1-month follow-up in patients who had received islets from younger donors. At 6-month follow-up after second or third injection and at 12-month follow-up, secretory units of islets in transplantation indices and C-peptide/glucose ratios were significantly higher in patients with donors aged 45 years or younger.
These data suggest that, despite similar outcomes of the isolation procedure, islet graft function is significantly influenced by donor age. These results may have important consequences in the definition of pancreas allocation criteria.
Transplantation 02/2011; 91(3):360-6. · 4.00 Impact Factor
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ABSTRACT: The major challenge in transplantation medicine remains long-term allograft acceptance, with preserved allograft function under minimal chronic immunosuppression. To safely achieve the goal of sustained donor-specific T and B cell non-responsiveness, research efforts are now focusing on therapies based on cell subsets with regulatory properties. In particular the transfusion of human regulatory T cells (Treg) is currently being evaluated in phase I/II clinical trials for the treatment of graft versus host disease following hematopoietic stem cell transplantation, and is also under consideration for solid organ transplantation. The purpose of this review is to recapitulate current knowledge on naturally occurring as well as induced human Treg, with emphasis on their specific phenotype, suppressive function and how these cells can be manipulated in vitro and/or in vivo for therapeutic purposes in transplantation medicine. We highlight the potential but also possible limitations of Treg-based strategies to promote long-term allograft survival. It is evident that the bench-to-beside translation of these protocols still requires further understanding of Treg biology. Nevertheless, current data already suggest that Treg therapy alone will not be sufficient and needs to be combined with other immunomodulatory approaches in order to induce allograft tolerance.
Self/Nonself - Immune Recognition and Signaling 01/2011; 2(1):26-34.
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Helga Ellingsgaard,
Irina Hauselmann,
Beat Schuler,
Abdella M Habib,
Laurie L Baggio,
Daniel T Meier,
Elisabeth Eppler,
Karim Bouzakri,
Stephan Wueest, Yannick D Muller, [......],
Manfred Reinecke,
Daniel Konrad,
Max Gassmann,
Frank Reimann,
Philippe A Halban,
Jesper Gromada,
Daniel J Drucker,
Fiona M Gribble,
Jan A Ehses,
Marc Y Donath
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ABSTRACT: Exercise, obesity and type 2 diabetes are associated with elevated plasma concentrations of interleukin-6 (IL-6). Glucagon-like peptide-1 (GLP-1) is a hormone that induces insulin secretion. Here we show that administration of IL-6 or elevated IL-6 concentrations in response to exercise stimulate GLP-1 secretion from intestinal L cells and pancreatic alpha cells, improving insulin secretion and glycemia. IL-6 increased GLP-1 production from alpha cells through increased proglucagon (which is encoded by GCG) and prohormone convertase 1/3 expression. In models of type 2 diabetes, the beneficial effects of IL-6 were maintained, and IL-6 neutralization resulted in further elevation of glycemia and reduced pancreatic GLP-1. Hence, IL-6 mediates crosstalk between insulin-sensitive tissues, intestinal L cells and pancreatic islets to adapt to changes in insulin demand. This previously unidentified endocrine loop implicates IL-6 in the regulation of insulin secretion and suggests that drugs modulating this loop may be useful in type 2 diabetes.
Nature medicine 01/2011; 17(11):1481-9. · 27.14 Impact Factor
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ABSTRACT: It is generally admitted that the endocrine cell organization in human islets is different from that of rodent islets. However, a clear description of human islet architecture has not yet been reported. The aim of this work was to describe our observations on the arrangement of human islet cells.
Human pancreas specimens and isolated islets were processed for histology. Sections were analyzed by fluorescence microscopy after immunostaining for islet hormones and endothelial cells.
In small human islets (40-60 mum in diameter), beta-cells had a core position, alpha-cells had a mantle position, and vessels laid at their periphery. In bigger islets, alpha-cells had a similar mantle position but were found also along vessels that penetrate and branch inside the islets. As a consequence of this organization, the ratio of beta-cells to alpha-cells was constantly higher in the core than in the mantle part of the islets, and decreased with increasing islet diameter. This core-mantle segregation of islet cells was also observed in type 2 diabetic donors but not in cultured isolated islets. Three-dimensional analysis revealed that islet cells were in fact organized into trilaminar epithelial plates, folded with different degrees of complexity and bordered by vessels on both sides. In epithelial plates, most beta-cells were located in a central position but frequently showed cytoplasmic extensions between outlying non-beta-cells.
Human islets have a unique architecture allowing all endocrine cells to be adjacent to blood vessels and favoring heterologous contacts between beta- and alpha-cells, while permitting homologous contacts between beta-cells.
Diabetes 02/2010; 59(5):1202-10. · 8.29 Impact Factor
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Yannick D Muller,
Gang Mai,
Philippe Morel,
Véronique Serre-Beinier,
Carmen Gonelle-Gispert,
Gisella Puga Yung,
Driss Ehirchiou,
Jean-Christophe Wyss,
Sinda Bigenzahn,
Magali Irla,
Christoph Heusser,
Déla Golshayan,
Jörg D Seebach,
Thomas Wekerle,
Leo H Bühler
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ABSTRACT: Anti-CD154 (MR1) monoclonal antibody (mAb) and rapamycin (RAPA) treatment both improve survival of rat-to-mouse islet xenograft. The present study investigated the effect of combined RAPA/MR1 treatment on rat-to-mouse islet xenograft survival and analyzed the role of CD4(+)CD25(+)Foxp3(+) T regulatory cells (Treg) in the induction and maintenance of the ensuing tolerance.
C57BL/6 mice were treated with MR1/RAPA and received additional monoclonal anti-IL2 mAb or anti CD25 mAb either early (0-28 d) or late (100-128 d) post-transplantation. Treg were characterised in the blood, spleen, draining lymph nodes and within the graft of tolerant and rejecting mice by flow cytometry and immunohistochemistry. Fourteen days of RAPA/MR1 combination therapy allowed indefinite islet graft survival in >80% of the mice. Additional administration of anti-IL-2 mAb or depleting anti-CD25 mAb at the time of transplantation resulted in rejection (100% and 89% respectively), whereas administration at 100 days post transplantation lead to lower rejection rates (25% and 40% respectively). Tolerant mice showed an increase of Treg within the graft and in draining lymph nodes early post transplantation, whereas 100 days post transplantation no significant increase of Treg was observed. Rejecting mice showed a transient increase of Treg in the xenograft and secondary lymphoid organs, which disappeared within 7 days after rejection.
These results suggest a critical role for Treg in the induction phase of tolerance early after islet xenotransplantation. These encouraging data support the need of developing further Treg therapy for overcoming the species barrier in xenotransplantation.
PLoS ONE 01/2010; 5(4):e10352. · 4.09 Impact Factor
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ABSTRACT: The role of T regulatory cells (Treg) in the induction and maintenance of allograft tolerance is being studied to a great extent. In contrast, little is known on their potential to prevent graft rejection in the field of xenotransplantation, where acute vascular rejection mediated by cellular and humoral mechanisms and thrombotic microangiopathy still prevents long-term graft survival. In this regard, the induction of donor-specific tolerance through isolation and expansion of xenoantigen-specific recipient Treg is currently becoming a focus of interest. This review will summarize the present knowledge concerning Treg and their potential use in xenotransplantation describing in particular CD4(+)CD25(+)Foxp3(+) T cells, CD8(+)CD28(-) Treg, double negative CD4(-)CD8(-) T cells, and natural killer Treg. Although only studied in vitro so far, human CD4(+)CD25(+)Foxp3(+) Treg is currently the best characterized subpopulation of regulatory cells in xenotransplantation. CD8(+)CD28(-) Treg and double negative CD4(-)CD8(-) Treg also seem to be implicated in tolerance maintenance of xenografts. Finally, one study revealing a role for natural killer CD4(+)Valpha14(+) Treg in the prolongation of xenograft survival needs further confirmation. To our opinion, CD4(+)CD25(+)Foxp3(+) Treg are a promising candidate to protect xenografts. In contrast to cadaveric allotransplantation, the donor is known prior to xenotransplantation. This advantage allows the expansion of recipient Treg in a xenoantigen specific manner before transplantation.
Xenotransplantation 06/2009; 16(3):121-8. · 2.33 Impact Factor
