title: Meta-analysis of the independent and cumulative effects of multiple genetic modifications on pig lung xenograft performance during ex vivo perfusion with human blood.
abstract: BACKGROUND
  Genetically modified pigs are a promising potential source of lung xenografts. Ex vivo xenoperfusion is an effective platform for testing the effect of new modifications, but typical experiments are limited by testing of a single genetic intervention and small sample sizes. The purpose of this study was to analyze the individual and aggregate effects of donor genetic modifications on porcine lung xenograft survival and injury in an extensive pig lung xenoperfusion series.
  
  
  METHODS
  Data from 157 porcine lung xenoperfusion experiments using otherwise unmodified heparinized human blood were aggregated as either continuous or dichotomous variables. Lungs were wild type in 17 perfusions (11% of the study group), while 31 lungs (20% of the study group) had one genetic modification, 40 lungs (39%) had 2, and 47 lungs (30%) had 3 or more modifications. The primary endpoint was functional lung survival to 4 h of perfusion. Secondary analyses evaluated previously identified markers associated with known lung xenograft injury mechanisms. In addition to comparison among all xenografts grouped by survival status, a subgroup analysis was performed of lungs incorporating the GalTKO.hCD46 genotype.
  
  
  RESULTS
  Each increase in the number of genetic modifications was associated with additional prolongation of lung xenograft survival. Lungs that exhibited survival to 4 h generally had reduced platelet activation and thrombin generation. GalTKO and the expression of hCD46, HO-1, hCD55, or hEPCR were associated with improved survival. hTBM, HLA-E, and hCD39 were associated with no significant effect on the primary outcome.
  
  
  CONCLUSIONS
  This meta-analysis of an extensive lung xenotransplantation series demonstrates that increasing the number of genetic modifications targeting known xenogeneic lung injury mechanisms is associated with incremental improvements in lung survival. While more detailed mechanistic studies are needed to explore the relationship between gene expression and pathway-specific injury and explore why some genes apparently exhibit neutral (hTBM, HLA-E) or inconclusive (CD39) effects, GalTKO, hCD46, HO-1, hCD55, and hEPCR modifications were associated with significant lung xenograft protection. This analysis supports the hypothesis that multiple genetic modifications targeting different known mechanisms of xenograft injury will be required to optimize lung xenograft survival.
authors.affiliation: Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA; Center for Vascular and Inflammatory Diseases, University of Maryland School of Medicine, Baltimore, MD, USA.
authors.forename: Donald G
authors.initials: DG
authors.lastname: Harris
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Quinn
authors.forename: Beth M
authors.initials: BM
authors.lastname: French
authors.forename: Evan
authors.initials: E
authors.lastname: Schwartz
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Kang
authors.forename: Siamak
authors.initials: S
authors.lastname: Dahi
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Phelps
authors.forename: David L
authors.initials: DL
authors.lastname: Ayares
authors.forename: Lars
authors.initials: L
authors.lastname: Burdorf
authors.forename: Agnes M
authors.initials: AM
authors.lastname: Azimzadeh
authors.forename: Richard N
authors.initials: RN
authors.lastname: Pierson
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified / Q000276:immunology*; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology; D015478:Antigens, Heterophile / Q000235:genetics; D001769:Blood / Q000276:immunology; D000074283:Endothelial Protein C Receptor; D005700:Galactosyltransferases / Q000172:deficiency / Q000235:genetics / Q000276:immunology; D055786:Gene Knockout Techniques; D006085:Graft Survival / Q000235:genetics / Q000276:immunology; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000276:immunology; D064593:Heterografts / Q000276:immunology*; D006801:Humans; D066298:In Vitro Techniques; D016040:Lung Transplantation / Q000009:adverse effects / Q000379:methods*; D051916:Membrane Cofactor Protein / Q000235:genetics / Q000276:immunology; D010477:Perfusion; D011956:Receptors, Cell Surface / Q000235:genetics / Q000276:immunology; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D034421:Sus scrofa / Q000235:genetics* / Q000276:immunology*; D014183:Transplantation, Heterologous / Q000009:adverse effects / Q000379:methods*
chemical_list: D015703:Antigens, CD; D015478:Antigens, Heterophile; C497857:CD46 protein, human; D000074283:Endothelial Protein C Receptor; D051916:Membrane Cofactor Protein; C478370:PROCR protein, human; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D005700:Galactosyltransferases; C530267:alpha-1,3-galactosyltransferase 1, porcine
keywords: ex vivo lung perfusion; genetically engineered pig; immune response; lung xenotransplantation; thromboregulation