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Human Islets (human + islet)

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Medical Sciences	100%

Selected Abstracts

Beneficial Effects of Desferrioxamine on Encapsulated Human Islets,In Vitro and In Vivo Study

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 9 2010
V. Vaithilingam
As many as 2000 IEQs (islet equivalent) of encapsulated human islets are required to normalize glucose levels in diabetic mice. To reduce this number, encapsulated islets were exposed to 100 ,M desferrioxamine (DFO) prior to transplantation. Cell viability, glucose-induced insulin secretion, VEGF (Vascular endothelial growth factor), HIF-1, (Hypoxia inducible factor-1 alpha), caspase-3 and caspase-8 levels were assessed after exposure to DFO for 12, 24 or 72 h. Subsequently, 1000, 750 or 500 encapsulated IEQs were infused into peritoneal cavity of diabetic mice after 24 h exposure to DFO. Neither viability nor function in vitro was affected by DFO, and levels of caspase-3 and caspase-8 were unchanged. DFO significantly enhanced VEGF secretion by 1.6- and 2.5-fold at 24 and 72 h, respectively, with a concomitant increase in HIF-1, levels. Euglycemia was achieved in 100% mice receiving 1000 preconditioned IEQs, as compared to only 36% receiving unconditioned IEQs (p < 0.001). Similarly, with 750 IEQ, euglycemia was achieved in 50% mice receiving preconditioned islets as compared to 10% receiving unconditioned islets (p = 0.049). Mice receiving preconditioned islets had lower glucose levels than those receiving unconditioned islets. In summary, DFO treatment enhances HIF-1, and VEGF expression in encapsulated human islets and improves their ability to function when transplanted. [source]

Human Islets Derived From Donors After Cardiac Death Are Fully Biofunctional

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 10 2007
M. Zhao
Islets from brain-dead donors (BDDs) are being used in the treatment of Type 1 diabetes. However, both donor numbers and islet survival are limited. We explored the clinical potential for islets from non-heart-beating donors (NHBDs), who have lower circulating cytokines, by comparing islets from 10 NHBDs against 12 identically-isolated islets from BDDs over the same time period. The quantity and quality of islets from NHBDs was good. NHBD yielded ,12.6% more islets than those of BDDs (505 000 ± 84 230 vs. 400 970 ± 172 430 islet equivalent number [IEQ]/pancreas, p = 0.01) with comparable viability. ATP and GTP contents were lower (6.026 ± 3.076 vs. 18.105 ± 7.8 nM/mg protein, p = 0.01 and 1.52 ± 0.87 vs. 3.378 ± 0.83 nM/mg protein, p = 0.04) and correlated negatively to warm ischemia time (R2= 0.8022 and R2= 0.7996, respectively). Islets from NHBDs took longer to control hyperglycemia in diabetic mice, but were equally able to sustain euglycemia. With a warm ischemia time (WIT) of ,25 min, islets from NHBDs are at least as competent as islets from BDDs and should be suitable for clinical use. [source]

Composite Islet-Endothelial Cell Grafts: A Novel Approach to Counteract Innate Immunity in Islet Transplantation

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 11 2005
Ulrika Johansson
An instant blood-mediated inflammatory reaction (IBMIR) is elicited when islets come in contact with blood after intraportal transplantation. In contrast, endothelial cells (EC) readily tolerate contact with blood. A conceivable strategy to overcome IBMIR would be to create composite islet-EC grafts. Human islets were co-cultured with primary human aortic endothelial cells (HAEC) for 2,7 days to obtain 50,90% coverage. HAEC-coated islets were exposed to ABO-identical blood and analyzed with regard to clotting time, signs of inflammation and cell infiltration. Composite islet-HAEC graft survival was assessed after transplantation to athymic (nu/nu) nude mice. Exposed to blood, HAEC-coated islets induced less activation of coagulation and complement compared to control islets. Also, platelet and leukocyte consumption in blood was decreased. Clots with entrapped HAEC-coated islets showed less infiltration of CD11b+ cells. The extent of protection correlated to the level of HAEC coverage. Transplanted composite grafts stained positive for insulin and PECAM-1 demonstrating presence of both islets and HAEC within the islet graft 7 weeks after transplantation. Composite islet-HAEC grafts reduce all components of IBMIR. Refinement of the technique will allow introduction of composite islet-EC grafts in clinical islet transplantation, using autologous EC expanded in vitro and kept frozen until allogeneic islets become available for that specific recipient. [source]

Activation of human macrophages by allogeneic islets preparations: inhibition by AOP-RANTES and heparinoids

IMMUNOLOGY, Issue 4 2004
Séverine Sigrist
Summary During transplantation, pancreatic islets release chemokines which promote macrophage attraction, hampering engraftment of islets. The aim of this study was to modulate chemotaxis and the immune response of human macrophages induced by islets. Human monocyte-derived macrophages of healthy subjects were exposed to supernatants of human islets. Chemotaxis, tumour necrosis factor-, (TNF-,) and interleukin-1, (IL-1,) release were evaluated. To modulate migration, human macrophages were incubated in the presence of aminooxypentane-regulated on activation, normal, T-cell expressed, and secreted (AOP-RANTES), a potent antagonist of CCR5. Chemotactic activity of islets supernatant was modulated by the addition of heparin or heparinoids [pentosan and calix[8S]arene (C8S)]. AOP-RANTES significantly reduced, in a dose-dependent manner, macrophage chemotaxis and cytokine release induced by islets supernatant. The chemotactic index was reduced from 3·05 ± 0·27 to 0·71 ± 12, TNF-, from 1205 ± 52 to 202 ± 12 pg/ml, and IL-1, from 234 ± 12 to 10 ± 6 pg/ml. The trapping of chemokines by heparinoids reduced the chemotactic activity of islets supernatant from 3·05 ± 0·27 to 1·2 ± 0·1 with heparin or pentosan and to 1·72 ± 0·22 with C8S, and also decreased the TNF-, release by human macrophages from 1205 ± 35 to 1000 ± 26 (C8S), 250 ± 21 (heparin) and 320 ± 19 (pentosan) pg/ml, and IL-1, from 234 ± 13 to 151 ± 5 (C8S), 50 ± 3 (heparin) and 57 ± 4 (pentosan) pg/ml. In conclusion, AOP-RANTES and heparinoids inhibit human macrophage activation and migration induced by islets supernatant. [source]

Human islet-derived precursor cells can cycle between epithelial clusters and mesenchymal phenotypes

JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 8b 2009
Behrous Davani
Abstract We showed previously that undifferentiated, proliferating human islet-derived precursor cells (hIPCs) are a type of mesenchymal stem/stromal cell (MSC) that can be induced by serum deprivation to form clusters and ultimately differentiate in vitro to endocrine cells. We also demonstrated that partially differentiated hIPC clusters, when implanted under the kidney capsules of mice, continued to differentiate in vivo into hormone-producing cells. However, we noted that not all hIPC preparations yielded insulin-secreting cells in vivo and that in some animals no hormone-expressing cells were found. This suggested that the implanted cells were not always irreversibly committed to further differentiation and may even de-differentiate to a mesenchymal phenotype. In this study, we show that human cells with a mesenchymal phenotype are indeed found in the grafts of mice implanted with hIPCs in epithelial cell clusters (ECCs), which are obtained after 4-day in vitro culture of hIPCs in serum-free medium (SFM); mesenchymal cells were predominant in some grafts. We could mimic the transition of ECCs to de-differentiated mesenchymal cells in vitro by exposure to foetal bovine serum (FBS) or mouse serums, and to a significantly lesser extent to human serum. In a complementary series of experiments, we show that mouse serum and FBS are more effective stimulants of mesenchymal hIPC migration than is human serum. We found that proliferation was not needed for the transition from ECCs to de-differentiated cells because mitomycin-treated hIPCs that could not proliferate underwent a similar transition. Lastly, we show that cells exhibiting a mesenchymal phenotype can be found in grafts of adult human islets in mice. We conclude that epithelial-to-mesenchymal transition (EMT) of cells in hIPC ECCs can occur following implantation in mice. This potential for EMT of human islets or differentiated precursor cells must be considered in strategies for cell replacement therapy for diabetes. [source]

Beneficial Effects of Desferrioxamine on Encapsulated Human Islets,In Vitro and In Vivo Study

Improving the Procedure for Detection of Intrahepatic Transplanted Islets by Magnetic Resonance Imaging

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 10 2009
M. L. Malosio
Islet transplantation is an effective therapy for restoring normoglycemia in type-1 diabetes, but long-term islet graft function is achieved only in a minority of cases. Noninvasive magnetic resonance imaging of pancreatic islets is an attractive option for "real-time" monitoring of graft evolution. So far, previous studies have been performed in the absence of a standardized labeling procedure and, besides a feasibility study in patients, the effectiveness and safety of various labeling approaches were tested only with high field magnets (4.7 T). In this study, we addressed: (a) standardization of a labeling procedure for human islets with clinically-approved contrast agent Endorem®, (b) safety aspects of labeling related to inflammation and (c) quality of imaging both at 7 T and 1.5 T. We have highlighted that the ratio of Endorem®/islet is crucial for reproducible labeling, with a ratio of 2.24 ug/IEQ, allowing successful in vivo imaging both with 1.5 T and 7.0 T magnets up to 143 days after intrahepatic transplant. With this standardized labeling procedure, labeled islets are neither inflamed nor more susceptible to inflammatory insults than unlabeled ones. This report represents an important contribution towards the development of a standardized and safe clinical protocol for the noninvasive imaging of transplanted islets in humans. [source]

Tirofiban and Activated Protein C Synergistically Inhibit the Instant Blood Mediated Inflammatory Reaction (IBMIR) from Allogeneic Islet Cells Exposure to Human Blood

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 7 2009
S. Akima
Instant blood mediated inflammatory reaction (IBMIR) occurs when islets are exposed to blood and manifests clinically as portal vein thrombosis and graft failure. The aim of this study was to determine the impact of recombinant human activated protein C (rhAPC) and platelet inhibition on IBMIR in order to develop a better targeted treatment for this condition. Five thousand human islet cell equivalents (IEQ) were mixed in a PVC loop system with 7 mL of ABO compatible human blood and incubated with rhAPC, either alone or in combination with tirofiban. Admixing human islets and blood caused rapid clot formation, consumption of platelets, leukocytes, fibrinogen, coagulation factors and raised d -dimers. Islets were encased in a fibrin and platelet clot heavily infiltrated with neutrophils. Tirofiban monotherapy was ineffective, whereas rhAPC monotherapy prevented IBMIR in a dose-dependent manner, preserving islet integrity while maintaining platelet and leukocyte counts, fibrinogen and coagulation factor levels, and reducing d -dimer formation. The combination of tirofiban and low-dose rhAPC inhibited IBMIR synergistically with an efficacy equal to high dose rhAPC. Tirofiban and rhAPC worked synergistically to preserve islets, suggesting that co-inhibition of the platelet and coagulation pathways' contribution to thrombin generation is required for the optimal anti-IBMIR effect. [source]

Thrombomodulin Improves Early Outcomes After Intraportal Islet Transplantation

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 6 2009
W Cui
Primary islet nonfunction due to an instant blood mediated inflammatory reaction (IBMIR) leads to an increase in donor islet mass required to achieve euglycemia. In the presence of thrombin, thrombomodulin generates activated protein C (APC), which limits procoagulant and proinflammatory responses. In this study, we postulated that liposomal formulations of thrombomodulin (lipo-TM), due to its propensity for preferential uptake in the liver, would enhance intraportal engraftment of allogeneic islets by inhibiting the IBMIR. Diabetic C57BL/6J mice underwent intraportal transplantation with B10.BR murine islets. In the absence of treatment, conversion to euglycemia was observed among 29% of mice receiving 250 allo-islets. In contrast, a single infusion of lipo-TM led to euglycemia in 83% of recipients (p = 0.0019). Fibrin deposition (p < 0.0001), neutrophil infiltration (p < 0.0001), as well as expression TNF-, and IL-, (p < 0.03) were significantly reduced. Significantly, thrombotic responses mediated by human islets in contact with human blood were also reduced by this approach. Lipo-TM improves the engraftment of allogeneic islets through a reduction in local thrombotic and inflammatory processes. As an enzyme-based pharmacotherapeutic, this strategy offers the potential for local generation of APC at the site of islet infusion, during the initial period of elevated thrombin production. [source]

Antiangiogenic and Immunomodulatory Effects of Rapamycin on Islet Endothelium: Relevance for Islet Transplantation

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 11 2006
V. Cantaluppi
Donor intra-islet endothelial cells contribute to neovascularization after transplantation. Several factors may interfere with this process and ultimately influence islet engraftment. Rapamycin, a central immunosuppressant in islet transplantation, is an mTOR inhibitor that has been shown to inhibit cancer angiogenesis. The aim of this study was to evaluate the effects of rapamycin on islet endothelium. Rapamycin inhibited the outgrowth of endothelial cells from freshly purified human islets and the formation of capillary-like structures in vitro and in vivo after subcutaneous injection within Matrigel plugs into SCID mice. Rapamycin decreased migration, proliferation and angiogenic properties of human and mouse islet-derived endothelial cell lines with appearance of apoptosis. The expression of angionesis-related factors VEGF, ,V,3 integrin and thrombospondin-1 on islet endothelium was altered in the presence of rapamycin. On the other hand, rapamycin decreased the surface expression of molecules involved in immune processes such as ICAM-1 and CD40 and reduced the adhesion of T cells to islet endothelium. Our results suggest that rapamycin exerts dual effects on islet endothelium inducing a simultaneous inhibition of angiogenesis and a down-regulation of receptors involved in lymphocyte adhesion and activation. [source]