title: Tetracycline-regulated expression of VEGF-A in beta cells induces angiogenesis: improvement of engraftment following transplantation.
abstract: Early revascularization of pancreatic islet cells after transplantation is crucial for engraftment, and it has been suggested that vascular endothelial growth factor-A (VEGF-A) plays a significant role in this process. Although VEGF gene therapy can improve angiogenesis, uncontrolled VEGF secretion can lead to vascular tumor formation. Here we have explored the role of temporal VEGF expression, controlled by a tetracycline (TC)-regulated promoter, on revascularization and engraftment of genetically modified beta cells following transplantation. To this end, we modified the CDM3D beta cell line using a lentiviral vector to promote secretion of VEGF-A either in a TC-regulated (TET cells) or a constitutive (PGK cells) manner. VEGF secretion, angiogenesis, cell proliferation, and stimulated insulin secretion were assessed in vitro. VEGF secretion was increased in TET and PGK cells, and VEGF delivery resulted in angiogenesis, whereas addition of TC inhibited these processes. Insulin secretion by the three cell types was similar. We used a syngeneic mouse model of transplantation to assess the effects of this controlled VEGF expression in vivo. Time to normoglycemia, intraperitoneal glucose tolerance test, graft vascular density, and cellular mass were evaluated. Increased expression of VEGF resulted in significantly better revascularization and engraftment after transplantation when compared to control cells. In vivo, there was a significant increase in vascular density in grafted TET and PGK cells versus control cells. Moreover, the time for diabetic mice to return to normoglycemia and the stimulated plasma glucose clearance were also significantly accelerated in mice transplanted with TET and PGK cells when compared to control cells. VEGF was only needed during the first 2-3 weeks after transplantation; when removed, normoglycemia and graft vascularization were maintained. TC-treated mice grafted with TC-treated cells failed to restore normoglycemia. This approach allowed us to switch off VEGF secretion when the desired effects had been achieved. TC-regulated temporal expression of VEGF using a gene therapy approach presents a novel way to improve early revascularization and engraftment after islet cell transplantation.
authors.affiliation: Transplantation and Surgical Department, Semmelweis University, Budapest, H-1089, Hungary.
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Mathe
authors.forename: Philippe
authors.initials: P
authors.lastname: Dupraz
authors.forename: Chris
authors.initials: C
authors.lastname: Rinsch
authors.forename: Bernard
authors.initials: B
authors.lastname: Thorens
authors.forename: Domenico
authors.initials: D
authors.lastname: Bosco
authors.forename: Marie
authors.initials: M
authors.lastname: Zbinden
authors.forename: Philippe
authors.initials: P
authors.lastname: Morel
authors.forename: Thierry
authors.initials: T
authors.lastname: Berney
authors.forename: Michael S
authors.initials: MS
authors.lastname: Pepper
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D006085:Graft Survival / Q000187:drug effects*; D007328:Insulin / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism*; D016381:Islets of Langerhans Transplantation / Q000379:methods*; D051379:Mice; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D013752:Tetracycline / Q000494:pharmacology*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
chemical_list: D007328:Insulin; D011500:Protein Synthesis Inhibitors; D042461:Vascular Endothelial Growth Factor A; D013752:Tetracycline; D005947:Glucose