Improvement of Rat Islet Viability during Transplantation: Validation of Pharmacological Approach to Induce VEGF Overexpression

Abstract

Delayed and insufficient revascularization during islet transplantation deprives islets of oxygen and nutrients, resulting in graft failure. Vascular endothelial growth factor (VEGF) could play a critical role in islet revascularization. We aimed to develop pharmacological strategies for VEGF overexpression in pancreatic islets using the iron chelator deferoxamine (DFO), thus avoiding obstacles or safety risks associated with gene therapy. Rat pancreatic islets were infected in vivo using an adenovirus (ADE) encoding human VEGF gene (4.10(8) pfu/pancreas) or were incubated in the presence of DFO (10 μmol/L). In vitro viability, functionality, and the secretion of VEGF were evaluated in islets 1 and 3 days after treatment. Infected islets or islets incubated with DFO were transplanted into the liver of syngenic diabetic rats and the graft efficiency was estimated in vivo by measuring body weight, glycemia, C-peptide secretion, and animal survival over a period of 2 months. DFO induced transient VEGF overexpression over 3 days, whereas infection with ADE resulted in prolonged VEGF overexpression lasting 14 days; however, this was toxic and decreased islet viability and functionality. The in vivo study showed a decrease in rat deaths after the transplantation of islets treated with DFO or ADE compared with the sham and control group. ADE treatment improved body weight and C-peptide levels. Gene therapy and DFO improved metabolic control in diabetic rats after transplantation, but this effect was limited in the presence of DFO. The pharmacological approach is an interesting strategy for improving graft efficiency during transplantation, but this approach needs to be improved with drugs that are more specific.

In Vitro and In Vivo Investigation of the Angiogenic Effects of Liraglutide during Islet Transplantation

“…Previous studies showed improvements in islet function and vascularisation following ex vivo transfection with the human VEGF gene [ 14 ], [ 15 ]. However, numerous risks have been associated with gene transfer, including the short-term nature of gene therapy, the immune response, problems with viral vectors and the risk of carcinogenesis.…”

“…Thus, a pharmacological approach to increase VEGF expression may be more suitable for clinical application. We previously reported that pre-treatment of pancreatic islets with deferoxamine, an iron chelator already in clinical use, induced VEGF overexpression by activating the hypoxia inducible factor-1α (HIF-1α) pathway; this approach improved metabolic control in diabetic rats [ 14 ], [ 16 ]. However, long-term maintenance of graft function was not achieved, probably due to the stabilisation of HIF-1α, which triggers apoptosis at high concentrations [ 17 ].…”

Proangiogenic Hydrogels Within Macroporous Scaffolds Enhance Islet Engraftment in an Extrahepatic Site

“…[29][30][31][32][33][34] The use of proangiogenic, degradable hydrogels through the combination of angiogenic growth factors (GFs), such as the plateletderived GF (PDGF-BB) and vascular endothelial GF (VEGF), and biomaterials is an attractive approach that has shown enhanced therapeutic effect over delivery of GF alone. [35][36][37][38] Given the importance of islet revascularization in graft efficacy, we sought to explore the potential use of proangiogenic hydrogels within PDMS scaffolds at an alternative transplant site.…”

Impact of Pancreatic Rat Islet Density on Cell Survival during Hypoxia

“…Based on clinical hepatic islet transplantations, 10,000 IEQ/kg is needed to reach normoglycaemia [ 1 ]. Unfortunately, it has been estimated that approximately 40% of the transplanted islets will die during the instant blood mediated inflammatory reaction (IBMIR) [ 23 ] and another 10 to 20% will die during vascularization [ 24 ]. These losses can be avoided when using a bioartificial pancreas.…”