title: Decreased fibrinolytic activity in porcine-to-primate cardiac xenotransplantation.
abstract: BACKGROUND
  One major barrier to successful xenotransplantation is acute vascular rejection, a process pathologically characterized by microvascular thrombosis and diffuse fibrin deposition in transplant blood vessels. This pathologic picture may result from a disturbance in the coagulant or fibrinolytic pathways that regulate normal vascular patency. This study evaluated the regulation of fibrinolytic activity defined by tissue plasminogen activator and plasminogen activator inhibitor-1 as it may exist in the setting of acute vascular rejection.
  
  
  RESULTS
  Serial biopsies from cardiac xenotransplants evaluated by immunofluorescence microscopy demonstrated progressive decreases in tissue plasminogen activator and increases in plasminogen activator inhibitor-1. In vitro studies measuring fibrinolytic activity of cell culture medium from porcine aortic endothelial cells stimulated with human serum or autologous porcine serum revealed that human serum triggered as much as 93% increase in antifibrinolytic activity.
  
  
  CONCLUSIONS
  These findings demonstrate that porcine vascular endothelial cells change toward an antifibrinolytic state following stimulation with human xenoreactive antibodies and complement. The shift is at least partly explained by an increased ratio of plasminogen activator inhibitor-1 to tissue plasminogen activator, and is at least in part mediated by the activation of complement. This increased antifibrinolytic activity may contribute to the thrombotic diathesis seen in acute vascular rejection in pig-to-primate xenografts.
authors.affiliation: Duke University Medical Center, Department of Surgery, Durham, North Carolina, USA.
authors.forename: M F
authors.initials: MF
authors.lastname: Kalady
authors.forename: J H
authors.initials: JH
authors.lastname: Lawson
authors.forename: R D
authors.initials: RD
authors.lastname: Sorrell
authors.forename: J L
authors.initials: JL
authors.lastname: Platt
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D000910:Antibodies, Heterophile / Q000502:physiology; D015703:Antigens, CD / Q000235:genetics / Q000502:physiology; D001011:Aorta; D016913:Blood Component Transfusion; D018958:CD55 Antigens / Q000235:genetics / Q000502:physiology*; D018957:CD59 Antigens / Q000235:genetics / Q000502:physiology*; D002470:Cell Survival; D002478:Cells, Cultured; D003165:Complement System Proteins / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D005342:Fibrinolysis / Q000502:physiology*; D016027:Heart Transplantation / Q000502:physiology*; D006706:Homeostasis; D006801:Humans; D007700:Kinetics; D010215:Papio; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D013552:Swine; D010959:Tissue Plasminogen Activator / Q000378:metabolism; D014183:Transplantation, Heterologous / Q000502:physiology*
chemical_list: D000910:Antibodies, Heterophile; D015703:Antigens, CD; D018958:CD55 Antigens; D018957:CD59 Antigens; D017395:Plasminogen Activator Inhibitor 1; D003165:Complement System Proteins; D010959:Tissue Plasminogen Activator