title: A novel approach to xenotransplantation combining surface engineering and genetic modification of isolated adult porcine islets.
abstract: BACKGROUND
  Effective cytoprotection to xenoislets would circumvent the major tissue limitation for pancreatic islet transplantation (PIT). Cell-surface engineering with poly[ethylene glycol] (PEG) derivatives can successfully prevent antibody binding to the surface antigens. Gene transfer of the antiapoptotic Bcl-2 gene has been shown to decrease cytotoxicity mediated by xenoreactive natural antibodies and complement. In this study, we assessed survival and function of surface-engineered porcine islets genetically modified to overexpress Bcl-2.
  
  
  METHODS
  Incorporation of PEG derivatives into the islet surface and adenovirus-mediated gene transfer of Bcl-2 (AdBcl-2) was accomplished within 24 hours post-isolation. Cytotoxicity induced by human xenoreactive natural antibodies was evaluated by islet intracellular lactate dehydrogenase release and microscopic analysis using membrane-integrity staining. Islet functionality was assessed by static incubation and after intraportal infusion (5000 IEQ) into diabetic NOD-SCID mice reconstituted with human lymphocytes (5 x 10 8 /intraperitoneally/15 days before PIT).
  
  
  RESULTS
  No significant change in islet viability, morphology, and functionality was demonstrated after the incorporation of PEG-mono-succimidyl-succinate (MSPEG), or PEG-di-succimidyl-succinate "end"-capped with albumin (DSPEG) with or without gene transfer of Bcl-2. Islets treated with MSPEG presented a significant reduction in lactate dehydrogenase release compared with controls (41.2 +/- 3 vs 72.1 +/- 7, respectively, P <.05). Further protection was accomplished by DSPEG or AdBcl-2. The maximal cytoprotection was achieved by DSPEG +AdBcl-2 (15.5 +/- 4.9%, P <.001). Nonfasting glucose >200 mg/dL was found in 100% of the animals given control islets (n = 6) within 48 hours post-transplant. In contrast, euglycemia was achieved in 100% of the animals given islets modified with DSPEG + AdBcl-2 during the observation time.
  
  
  CONCLUSIONS
  Surface-engineering with functionalized PEG derivatives in combination with genetic modification with Bcl-2 significantly reduced islet loss after PIT. Application of this novel technology may improve results in xenoislet transplantation.
authors.affiliation: Department of Surgery, Division of Human Gene Therapy and Gene Therapy Center, University of Alabama at Birmingham, USA.
authors.forename: Juan L
authors.initials: JL
authors.lastname: Contreras
authors.forename: Dong
authors.initials: D
authors.lastname: Xie
authors.forename: Jimmy
authors.initials: J
authors.lastname: Mays
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Smyth
authors.forename: Christopher
authors.initials: C
authors.lastname: Eckstein
authors.forename: Firoz G
authors.initials: FG
authors.lastname: Rahemtulla
authors.forename: Carlton J
authors.initials: CJ
authors.lastname: Young
authors.forename: J
authors.initials: J
authors.lastname: Anthony Thompson
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Bilbao
authors.forename: David T
authors.initials: DT
authors.lastname: Curiel
authors.forename: Devin E
authors.initials: DE
authors.lastname: Eckhoff
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology; D002470:Cell Survival / Q000276:immunology; D002478:Cells, Cultured; D015870:Gene Expression; D018014:Gene Transfer Techniques; D019254:Genes, bcl-2 / Q000235:genetics*; D007515:Islets of Langerhans / Q000276:immunology; D016381:Islets of Langerhans Transplantation / Q000276:immunology*; D023421:Models, Animal; D011092:Polyethylene Glycols / Q000494:pharmacology; D013501:Surface-Active Agents / Q000494:pharmacology; D013552:Swine; D014183:Transplantation, Heterologous / Q000276:immunology*
chemical_list: D013501:Surface-Active Agents; D011092:Polyethylene Glycols