title: Porcine extrahepatic vascular endothelial asialoglycoprotein receptor 1 mediates xenogeneic platelet phagocytosis in vitro and in human-to-pig ex vivo xenoperfusion.
abstract: BACKGROUND
  Asialoglycoprotein receptor-1 (ASGR1) mediates capture and phagocytosis of platelets in pig-to-primate liver xenotransplantation. However, thrombocytopenia is also observed in xenotransplantation or xenoperfusion of other porcine organs than liver. We therefore assessed ASGR1 expression as well as ASGR1-mediated xenogeneic platelet phagocytosis in vitro and ex vivo on porcine aortic, femoral arterial, and liver sinusoidal endothelial cells (PAEC/PFAEC/PLSEC).
  
  
  METHODS
  Porcine forelimbs were perfused with whole, heparinized human or autologous pig blood. Platelets were counted at regular intervals. Pig limb muscle and liver, as well as PAEC/PFAEC/PLSEC, were characterized for ASGR1 expression. In vitro, PAEC cultured on microcarrier beads and incubated with non-anticoagulated human blood were used to study binding of human platelets and platelet-white blood cell aggregation. Carboxyfluorescein diacetate succinimidyl ester-labeled human platelets were exposed to PAEC/PFAEC/PLSEC and analyzed for ASGR1-mediated phagocytosis.
  
  
  RESULTS
  Human platelet numbers decreased from 102 ± 33 at beginning to 13 ± 6 × 10/μL (P < 0.0001) after 10 minutes of perfusion, whereas no significant decrease of platelets was seen during autologous perfusions (171 ± 26 to 122 ± 95 × 10/μL). The PAEC, PFAEC, and PLSEC all showed similar ASGR1 expression. In vitro, no correlation was found between reduction in platelet count and platelet-white blood cell aggregation. Phagocytosis of human carboxyfluorescein diacetate succinimidyl ester-labeled platelets by PAEC/PFAEC/PLSEC peaked at 15 minutes and was inhibited (P < 0.05 to P < 0.0001) by rabbit anti-ASGR1 antibody and asialofetuin.
  
  
  CONCLUSIONS
  The ASGR1 expressed on aortic and limb arterial pig vascular endothelium plays a role in binding and phagocytosis of human platelets. Therefore, ASGR1 may represent a novel therapeutic target to overcome thrombocytopenia associated with vascularized pig-to-primate xenotransplantation.
authors: 1 Department of Clinical Research, University of Bern, Bern, Switzerland. 2 Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland. 3 Clinic of Plastic and Hand Surgery, University Hospital, Bern, Switzerland. 4 Clinic of Cardiovascular Surgery, University Hospital, Bern, Switzerland. 5 Department of Surgery, Schulze Diabetes Institute, University of Minnesota, Minneapolis, MN. 6 Division of Immunology and Allergology, University Hospital and Medical Faculty, Geneva, Switzerland.
authors: Anjan K
authors: AK
authors: Bongoni
authors: David
authors: D
authors: Kiermeir
authors: Julie
authors: J
authors: Denoyelle
authors: Hansjörg
authors: H
authors: Jenni
authors: Christopher
authors: C
authors: Burlak
authors: Jörg D
authors: JD
authors: Seebach
authors: Esther
authors: E
authors: Vögelin
authors: Mihai A
authors: MA
authors: Constantinescu
authors: Robert
authors: R
authors: Rieben
mesh_terms: D000671:Amputation, Surgical; D000818:Animals; D037263:Asialoglycoprotein Receptor / Q000276:immunology / Q000378:metabolism*; D001792:Blood Platelets / Q000276:immunology / Q000378:metabolism*; D001803:Blood Transfusion / Q000379:methods*; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000276:immunology / Q000378:metabolism*; D005260:Female; D005552:Forelimb / Q000098:blood supply* / Q000601:surgery; D006801:Humans; D008297:Male; D023421:Models, Animal; D010587:Phagocytosis; D010973:Platelet Adhesiveness; D015398:Signal Transduction; D013045:Species Specificity; D013552:Swine; D013921:Thrombocytopenia / Q000097:blood / Q000276:immunology; D013997:Time Factors; D014183:Transplantation, Heterologous
chemical_list: D037263:Asialoglycoprotein Receptor