Prolonged normoglycemia in STZ-induced diabetic rats transplanted with Adenovirus-mediated human TRAIL gene (Ad5hTRAIL) infected islets

Background: Type 1 diabetes, characterized by permanent destruction of insulin producing beta cells is lethal unless conventional exogenous-insulin therapy or whole-organ transplantation are employed (Tx). Pancreatic islet Tx is a safer and less invasive method compared to surgery but has been limited by islet graft mal-function and the graft failure. Thus, ex vivo genetically engineered b-cells are needed to prolong islet graft survival. TNF-related apoptosis-inducing ligand (TRAIL) plays essential roles during the course of diabetes. Thus, our aim was to develop a novel gene therapy approach by making pancreatic islets over-express TRAIL in Order to prevent auto-reactive T-cells from attacking the islets. Consequently, we investigated the effect of Ad5hTRAIL-infected islets transplanted into STZ-induced diabetic rats on graft function and survival. Methods: DTZ, PI and FDA staining were employed to determine islet cell purity and cell viability. Transduction efficacy of AdEGFP transduced islets was determined by both fluorometric measurements and fluorescent microscopy. While immunohistochemical methods were performed to show TRAIL expression after Ad5hTRAIL infection, cytotoxic effects of exogenous TRAIL expression were determined with Annexin-V staining. Wistar rats received a single intraperitoneal dose of 30, 40 and 50 mg/kg/BW STZ, and were followed up to 100 days. Ad5hTRAIL and AdLacZ-transduced or untransduced rat pancreatic islets were transplanted under the kidney capsule of STZ-induced diabetic rats. The diabetic status after islet TX was followed up for 90 days. Results: AdEGFP infections revealed optimum doses of adenovirus vectors to efficiently transduce pancreatic islets. Ad5hTRAIL infection was not cytotoxic at optimum doses. In terms of blood glucose and survival rates, optimum dose of STZ was 40 mg/kg/BW. The required number of islets transplanted to one recipient was at least 750. While Ad5hTRAIL-infected islets prolonged normoglycemia, Ad-LacZ-infected pancreatic islets did not manifest such an effect during the 90 day post-Tx period. Conclusion: Notable therapeutic efficiency of Ad5hTRAIL on transplanted pancreatic islets indicates a positive effect of TRAIL over the function and survival of the pancreatic islets.