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Vaithilingam V.,University of New South Wales | Vaithilingam V.,Australian Foundation for Diabetes Research | Kollarikova G.,Slovak Academy of Sciences | Qi M.,University of Illinois at Chicago | And 6 more authors.
Journal of Microencapsulation | Year: 2011

Pericapsular fibrotic overgrowth (PFO) may be attributed to an immune response against microcapsules themselves or to antigen shedding through microcapsule pores from encapsulated islet tissue. Modification of microcapsules aimed at reducing pore size should prevent PFO and improve graft survival. This study investigated the effect of increased gelling time (20 vs. 2min) in barium chloride on intrinsic properties of alginate microcapsules and tested their biocompatibility in-vivo. Prolonged gelling time affected neither permeability nor size of the microcapsules. However, prolonged gelling time for 20min produced brittle microcapsules compared to 2min during compression test. Encapsulation of human islets in both types of microcapsules affected neither islet viability nor function. The presence of PFO when transplanted into a large animal model such as baboon and its absence in small animal models such as rodents suggest that the host immune response towards alginate microcapsules is species rather than alginate specific. © 2011 Informa UK Ltd. All rights reserved.

Vaithilingam V.,University of New South Wales | Vaithilingam V.,Australian Foundation for Diabetes Research | Quayum N.,Cleveland Clinic | Joglekar M.V.,National Center for Cell Science | And 7 more authors.
Biomaterials | Year: 2011

Encapsulation of human islets may prevent their immune rejection when transplanted into diabetic recipients. To assist in understanding why clinical outcomes with encapsulated islets were not ideal, we examined the effect of encapsulation on their global gene (mRNA) and selected miRNAs (non-coding (nc)RNA) expression. For functional studies, encapsulated islets were transplanted into peritoneal cavity of diabetic NOD-SCID mice. Genomics analysis and transplantation studies demonstrate that islet origin and isolation centres are a major source of variation in islet quality. In contrast, tissue culture and the encapsulation process had only a minimal effect, and did not affect islet viability. Microarray analysis showed that as few as 29 genes were up-regulated and 2 genes down-regulated (cut-off threshold 0.1) by encapsulation. Ingenuity analysis showed that up-regulated genes were involved mostly in inflammation, especially chemotaxis, and vascularisation. However, protein expression of these factors was not altered by encapsulation, raising doubts about the biosignificance of the gene changes. Encapsulation had no effect on levels of islet miRNAs. In vivo studies indicate differences among the centres in the quality of the islets isolated. We conclude that microencapsulation of human islets with barium alginate has little effect on their transcriptome. © 2011 Elsevier Ltd.

Vaithilingam V.,University of New South Wales | Vaithilingam V.,Australian Foundation for Diabetes Research | Tuch B.E.,University of New South Wales | Tuch B.E.,Australian Foundation for Diabetes Research
Review of Diabetic Studies | Year: 2011

Human islet transplantation can provide good glycemic control in diabetic recipients without exogenous insulin. However, a major factor limiting its application is the recipient's need to adhere to life-long immunosuppression, something that has serious side effects. Microencapsulating human islets is a strategy that should prevent rejection of the grafted tissue without the need for anti-rejection drugs. Despite promising studies in various animal models, the encapsulated human islets so far have not made an impact in the clinical setting. Many non-immunological and immunological factors such as biocompatibility, reduced immunoprotection, hypoxia, pericapsular fibrotic overgrowth, effects of the encapsulation process and post-transplant inflammation hamper the successful application of this promising technology. In this review, strategies are discussed to overcome the above-mentioned factors and to enhance the survival and function of encapsulated insulin-producing cells, whether in islets or surrogate β-cells. Studies at our center show that barium alginate microcapsules are biocompatible in rodents, but not in humans, raising concerns over the use of rodents to predict outcomes. Studies at our center also show that the encapsulation process had little or no effect on the cellular transcriptome of human islets and on their ability to function either in vitro or in vivo. New approaches incorporating further modifications to the microcapsule surface to prevent fibrotic overgrowth are vital, if encapsulated human islets or β-cell surrogates are to become a viable therapy option for type 1 diabetes in humans. © by Lab & Life Press/SBDR.

Vaithilingam V.,University of New South Wales | Oberholzer J.,University of Illinois at Chicago | Guillemin G.J.,University of New South Wales | Tuch B.E.,Australian Foundation for Diabetes Research
American Journal of Transplantation | Year: 2010

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 μM desferrioxamine (DFO) prior to transplantation. Cell viability, glucose-induced insulin secretion, VEGF (Vascular endothelial growth factor), HIF-1α (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-1α 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-1α and VEGF expression in encapsulated human islets and improves their ability to function when transplanted. © 2010 The American Society of Transplantation and the American Society of Transplant Surgeons.

Vaithilingam V.,University of New South Wales | Vaithilingam V.,Australian Foundation for Diabetes Research | Barbaro B.,University of Illinois at Chicago | Oberholzer J.,University of Illinois at Chicago | Tuch B.E.,Australian Foundation for Diabetes Research
Pancreas | Year: 2011

OBJECTIVE: Human islets produced at an isolation center are shipped to researchers, usually taking short periods to arrive at their destination. In this study, we investigated whether human islets after long-distance shipment across the Pacific Ocean for 2 to 3 days and encapsulation could maintain their functionality. METHODS: Human islets were encapsulated in alginate and viability assessed using carboxyfluorescein diacetate and propidium iodide. Stimulation index after static glucose incubation was calculated. Streptozotocin-induced diabetic nonobese diabetic/severe combined immunodeficient mice were transplanted with 3000, 2000, or 1000 islet equivalents of nonencapsulated and encapsulated islets and glucose levels monitored. When levels were normal, the graft was retrieved and assessed. RESULTS: Viability of human islets was unaltered after long-distance shipment with a retrieval rate of 88.3% ± 1.9%. After encapsulation, the viability was unchanged (before encapsulation 86.1% ± 0.7% vs after encapsulation 80.8 ± 0.7%) at 11 days after isolation. Function in vitro of nonencapsulated and encapsulated islets was unaffected with a stimulation index of 2.2 and 1.9, respectively. Euglycemia was achieved in 100% mice receiving 2000 and 3000 islet equivalents of nonencapsulated and encapsulated islets, respectively. Capsules retrieved after transplantation was intact, free floating, and contained viable islets. CONCLUSION: Human islets can be shipped safely for long distances without compromising viability and function even after encapsulation and culture. © 2011 Lippincott Williams & Wilkins, Inc.

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