Co-expression of vascular endothelial growth factor and interleukin-1 receptor antagonist improves human islet survival and function.

PURPOSE: Ex vivo gene therapy approaches can improve the outcome of islet transplantation for treating type I diabetes. We have previously shown the improvement in islet function and vascularization following ex vivo transfection for human vascular endothelial growth factor (hVEGF) gene expression. In this study, we tested the hypothesis that co-expression of two genes, which target different challenges faced by islets post-transplantation, supplement each other to improve the survival and function of islets. We determined whether there is an additive effect of hVEGF and human interleukin-1 receptor antagonist (hIL-1Ra) gene expression in human islets.

MATERIALS AND METHODS: Human islets were co-infected with adenoviral vectors encoding hVEGF and hIL-1Ra. Islets were then incubated with a cocktail of inflammatory cytokines (IL-1beta+TNFalpha+IFNgamma), and islet viability and function were determined. In vivo function was evaluated by transplanting islets under the kidney capsules of streptozotocin-induced non-obese diabetic severe combined immunodeficient (NOD-SCID) mice.

RESULTS: Infection of human islets with Adv-hVEGF and/or Adv-hIL-1Ra inhibited expression of inducible nitric oxide synthase (iNOS), decreased the production of nitric oxide (NO), and prevented the loss of in vitro glucose-stimulated insulin response and viability. Moreover, co-expression of hVEGF and hIL-1Ra reduced the blood glucose level of mice, and increased the level of blood insulin and c-peptide upon glucose challenge.

CONCLUSIONS: Our results indicated that co-expression of genes that target different insults to transplanted islets can improve the outcome of islet transplantation better than either gene alone.