Functional enhancement of beta cells in transplanted pancreatic islets by secretion signal peptide-linked exendin-4 gene transduction.

This study assessed whether the newly designed exendin-4 (Ex-4) gene with highly releasable characteristics could enhance the beta cell function, thereby attenuating the essential islet mass required to cure diabetes. We constructed a lentivirus system encoding for a highly releasable secretion signal peptide, the peptide linked Ex-4 (SP-Ex-4) gene. After the transduction of lentivirus encoding for SP-Ex-4 (LV-SP-Ex-4) gene into the islets, the therapeutic effects of Ex-4 secreted were evaluated by conducting glucose-stimulated insulin secretion and cytokine- or hypoxia-induced apoptosis. Additionally, the effect of reduced islet numbers for transplantation was evaluated via in vivo models. The transduction of LV-SP-Ex-4 gene did not affect the viability of islets. In diabetic animal models, 50 islets expressing Ex-4 were transplanted to cure the diabetic nude mice, whereas at least 150 untransduced islets had to be transplanted to cure the diabetic nude mice. When the transduced islets were transplanted into diabetic immunocompetent mice, the survival rate of the mice was 18.0±4.9 days; however, when the untransduced islets were transplanted, they were rejected within 10.0±0.6 days. Therefore, the highly releasable Ex-4 could enhance the beta cell function with slightly enhanced viability of transplanted islets, presenting as a potential technology for overcoming islet shortage.