title: Effect of porcine endothelial tissue factor pathway inhibitor on human coagulation factors.
abstract: BACKGROUND
  Delayed xenograft rejection (DXR) is characterized by inflammation and vascular thrombosis. Activation of coagulation may occur as a result of tissue factor (TF) expression on both activated donor endothelial cells (EC) and recipient infiltrating monocytes (Mo). In addition, natural anticoagulants associated with porcine endothelial cells may not function adequately across species.
  
  
  METHODS
  In the present study, we examined the interaction of the TF pathway of coagulation with the natural anticoagulant TF pathway inhibitor, in xenogeneic leukocyte-EC cultures in vitro, and during rejection of discordant xenografts in vivo.
  
  
  RESULTS
  Coculture of human Mo with pig aortic EC (PAEC) resulted in 1.7-fold and 2-fold higher induction of Mo TF and Mo intercellular adhesion molecule-1, respectively, when compared with coculture with human aortic endothelial cells (HAEC). In addition, TF-dependent and -independent activation of coagulation factor X was higher on PAEC than on HAEC. Low levels of mRNA for tissue factor pathway inhibitor (TFPI) and its variant, TFPI-2, in resting PAEC were up-regulated by stimulation with tumor necrosis factor alpha. Procoagulant activity of recombinant human TF complexed to activated factor VII was inhibited by PAEC and HAEC-associated TFPI by 22% and 56%, respectively. In contrast, human activated factor X (factor Xa) activity was inhibited by human, but not porcine, EC-associated TFPI, suggesting functional incompatibility of PAEC for human factor Xa. Endothelial TFPI was detected in pig control organs and after hyperacute rejection, but was lost from the vasculature during DXR.
  
  
  CONCLUSIONS
  Lack of appropriate human factor Xa inhibition by porcine EC during hyperacute rejection and loss of porcine EC TFPI during DXR could promote the development of a procoagulant environment leading to xenograft rejection.
authors.affiliation: Department of Surgery, New England Deaconess Hospital, Harvard Medical School, Boston, Massachusetts 02215, USA.
authors.forename: C W
authors.initials: CW
authors.lastname: Kopp
authors.forename: J B
authors.initials: JB
authors.lastname: Siegel
authors.forename: W W
authors.initials: WW
authors.lastname: Hancock
authors.forename: J
authors.initials: J
authors.lastname: Anrather
authors.forename: H
authors.initials: H
authors.lastname: Winkler
authors.forename: C L
authors.initials: CL
authors.lastname: Geczy
authors.forename: E
authors.initials: E
authors.lastname: Kaczmarek
authors.forename: F H
authors.initials: FH
authors.lastname: Bach
authors.forename: S C
authors.initials: SC
authors.lastname: Robson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000925:Anticoagulants / Q000378:metabolism*; D001011:Aorta / Q000166:cytology; D015152:Blotting, Northern; D004591:Electrophoresis, Polyacrylamide Gel; D004730:Endothelium, Vascular / Q000378:metabolism*; D015942:Factor VIIa / Q000037:antagonists & inhibitors; D015951:Factor Xa / Q000378:metabolism*; D065427:Factor Xa Inhibitors; D005434:Flow Cytometry; D016027:Heart Transplantation; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D008074:Lipoproteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009000:Monocytes / Q000378:metabolism; D016415:Sequence Alignment; D013552:Swine; D013925:Thromboplastin / Q000378:metabolism*
chemical_list: D000925:Anticoagulants; D065427:Factor Xa Inhibitors; D008074:Lipoproteins; C051928:lipoprotein-associated coagulation inhibitor; D018799:Intercellular Adhesion Molecule-1; D013925:Thromboplastin; D015942:Factor VIIa; D015951:Factor Xa