نقش ايمني و محفاظتي IDO در پيوند جزاير پانكراس

سومين سمينار بين المللي تازه هاي ديابت

22 الي 23 آبان 1386، تهران - ايران

نوع ارائه: سخنراني
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Immuno-Protective Role of IDO in Islet Transplantation

Presentation Type: Speech
Abstract:

Introduction: Type 1 diabetes mellitus which is considered to be a serious chronic disorder with long-term complications, causes a significant mortality and morbidity in millions of patients worldwide. The only treatment currently available for these patients is repeated daily injections of insulin. Transplantation of the insulin-producing islet cells of the pancreas, which requires only a minor surgical procedure, has been proposed as an ideal approach to replace the efficient insulin regulation that is lost in type 1 diabetic patient. However, the success of this procedure depends on a long term use of the systemic immunosuppressive drugs. Thus, this study was undertaken to seek a novel approach through which a viral vector is used to deliver an immunosuppressive factor, indoleamine 2, 3-dioxygenase (IDO), a tryptophan catabolizing enzyme, gene into syngeneic fibroblasts populated into an engineered a matrix scaffold within which allogenic islets are embedded in. This will generate a tryptophan deficient microenvironment in which infiltrated immune cells, but not allogeneic islets, are unable to proliferate and destroy the engrafted allogeneic islets.
Hypothesis: It is our working hypothesis that engraftment of IDO expressing syngeneic fibroblasts co-populated with allogenic islets into a tissue engineered composite, can be immuno-protected upon its transplantation into a diabetic mouse model.
Methods: We have used a tissue engineering technique and an adenoviral vector to genetically prepare an IDO expressing syngeneic fibroblasts populated collagen-GAG gel within which allogeneic viable islet cells are embedded in. The viability and biological function of pancreatic islets were examined using different viability and functional assays. C57BL/6 (B6) mouse fibroblasts were induced to express IDO by transduction with an adenoviral vector and were co-cultured with B6 mouse lymphocytes and BALB/c mouse pancreatic islets in the presence or absence of an IDO inhibitor. Proliferation of lymphocytes were then assessed using [3H]-thymidine incorporation assay. Engraftment of viable allogeneic islets embedded within genetically modified IDO expressing syngeneic fibroblast populated engineered scaffold was then transplanted into the renal subcapsular space of a chemically induced diabetic mouse The criteria for graft take and level of blood glucose were evaluated at different time intervals.
Results: The results of this study showed that adenoviral vectors can effectively be used to deliver the IDO gene into syngeneic fibroblasts and that these cells along with allergenic islets can reliably be co-populated into a tissue engineered matrix composite. Our findings also revealed that co-culturing syngeneic IDO expressing fibroblasts with allergenic islets can suppress immune cell proliferation in an in vitro model. This effect was specific for IDO as allogeneic response was restored when IDO inhibitor was added to the culture. We further showed that islets survived better when were populated within tissue engineered matrix scaffold than those cultured on culture flask. Our preliminary findings of the in vivo phase of this study also showed a significant prolongation of graft survival in the mice receiving IDO-expressing syngeneic fibroblasts with allogeneic islets. Interestingly, the level of glucose in diabetic animals was normalized upon islet transplantation up to 6 weeks examined.
Conclusion: The finding of this study confirms that local expression of IDO can be induced by using adenoviral vector and that immuno-protect allogenic islet populated engineered matrix composite transplanted into kidney capsule of a diabetic animal model. Acknowledgement: This study has been supported by the Canadian Institute of Health research.

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