Insulin gene transfer enhances the function of human islet grafts

Abstract

Aims/hypothesis. Recent success in islet transplantation renews the hope for the complete cure of patients afflicted with Type 1 diabetes. However, in the Edmonton series, two to four pancreas donors were required to obtain a sufficient islet mass to reverse the diabetes of each patient. In view of the donor shortage, this represents a major obstacle preventing greater application of islet transplantation to diabetic patients. We hypothesised that increasing the expression of the insulin gene in transplanted islets would augment their capacity for insulin production, thereby allowing reversal of diabetes with a reduced islet mass. Methods. We used a replication defective adenovirus to deliver the human proinsulin gene (Ad-Ins) to isolated human islets. The function of Ad-Ins-transduced human islets was compared to islets transduced with a control vector (Ad-lacz).Results. Ad-Ins-transduced islets produced two to three times more insulin than normal islets or those infected with Ad-lacz, as assessed by in vitro perifusion tests of glucose stimulated insulin release. When transplanted, Ad-Ins-transduced islets normalised the blood glucose of diabetic immunodeficient NOD-Scid mice, and less than half as many Ad-Ins islets were required for reversal of diabetes than when normal islets were transplanted. Conclusion/interpretation. Our results suggest a simple and effective approach that could enhance the efficiency of islet transplantation for treatment of diabetes in humans. [Diabetologia (2003) 46:386-393]

Dominant negative mutant forms of the cAMP response element binding protein induce apoptosis and decrease the anti-apoptotic action of growth factors in human islets

“…Overexpression of the B cell CLL/lymphoma 2 gene (Bcl2), an anti-apoptotic gene, resulted in significant protection against apoptosis in vivo [9]. Similar results have been obtained by transferring the insulin gene [10], anti-apoptotic gene Bcl-XL [11] and XIAP (now known as baculoviral IAP repeat-containing 4 gene [BIRC4]), an endogenous inhibitor of caspases [12]. These studies suggested that manipulation of isolated islets is a potential strategy to improve islet survival after transplantation.…”

XIAP Overexpression in Human Islets Prevents Early Posttransplant Apoptosis and Reduces the Islet Mass Needed to Treat Diabetes

“…1E). This result is especially remarkable considering that only 10 virus particles/cell were used, while other groups have obtained at most 50% transduction efficiency in human islets using 500 -1,000 virus particles/ cell (29,34,35). Even with the 50-to 100-fold decrease in adenovirus used to transduce the islets in our experiments, infectious virus was still detectable up to 8 days posttransduction, after Ͼ20 wash steps, suggesting that adenovirally transduced islets must be cultured for at least a week before transplantation to ensure that no vector is inadvertently transferred to the recipient (Fig.…”

“…output per islet (29,33,34). These strategies function by enhancing the survival, growth, and/or function of the islets that manage to engraft but still exert little effect on apoptotic islets posttransplant.…”

“…Over the years, it has become apparent that adenoviral vectors represent the most reliable and efficient method to deliver genes to intact islets without the worrisome long-term effect of nontargeted genomic integration associated with lentiviral vectors. That being said, many groups have struggled to obtain transduction efficiencies Ͼ50%, which limits the opportunity to observe any protective effect, especially with a transgene such as XIAP, which functions intracellularly (29,34). One approach to improve transduction efficiency involves the use of more virus (i.e., increase the multiplicity of infection per cell), and while this does result in enhanced levels of transgene expression, the consequence is that the viral load itself becomes toxic to the islets (35).…”

Present Accomplishments and Future Prospects of Cell-Based Therapies for Type 1 Diabetes Mellitus

“…A simple conceptual approach to create hyper-functional islets would consist of augmentation of the regulated insulin secretory capacity of an islet graft by insulin gene transfer to the graft before transplantation. Deng et al demonstrated that Ad-Ins-transduced islets showed superior function in terms of insulin production and secretion as well as GSIS (Deng et al, 2003). The amount of basal insulin secretion and the overall pattern of insulin secretion from the AdIns-transduced islet appeared completely normal and following transplantation, recipients remained normoglycemic for more than 100 days without evidence of deterioration in graft function.…”