title: Von Willebrand factor regulates complement on endothelial cells.
abstract: Atypical hemolytic uremic syndrome and thrombotic thrombocytopenic purpura have traditionally been considered separate entities. Defects in the regulation of the complement alternative pathway occur in atypical hemolytic uremic syndrome, and defects in the cleavage of von Willebrand factor (VWF)-multimers arise in thrombotic thrombocytopenic purpura. However, recent studies suggest that both entities are related as defects in the disease-causing pathways overlap or show functional interactions. Here we investigate the possible functional link of VWF-multimers and the complement system on endothelial cells. Blood outgrowth endothelial cells (BOECs) were obtained from 3 healthy individuals and 2 patients with Type 3 von Willebrand disease lacking VWF. Cells were exposed to a standardized complement challenge via the combination of classical and alternative pathway activation and 50% normal human serum resulting in complement fixation to the endothelial surface. Under these conditions we found the expected release of VWF-multimers causing platelet adhesion onto BOECs from healthy individuals. Importantly, in BOECs derived from patients with von Willebrand disease complement C3c deposition and cytotoxicity were more pronounced than on BOECs derived from normal individuals. This is of particular importance as primary glomerular endothelial cells display a heterogeneous expression pattern of VWF with overall reduced VWF abundance. Thus, our results support a mechanistic link between VWF-multimers and the complement system. However, our findings also identify VWF as a new complement regulator on vascular endothelial cells and suggest that VWF has a protective effect on endothelial cells and complement-mediated injury.
authors.affiliation: Division of Nephrology, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada; Cell Biology Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Damien G
authors.initials: DG
authors.lastname: Noone
authors.affiliation: Cell Biology Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Pediatrics, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Riedl
authors.affiliation: Cell Biology Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Fred G
authors.initials: FG
authors.lastname: Pluthero
authors.affiliation: Clinical and Molecular Hemostasis Research Group, Queen's University, Kingston, Ontario, Canada.
authors.forename: Mackenzie L
authors.initials: ML
authors.lastname: Bowman
authors.affiliation: Department of Medicine, Division of Rheumatology, Washington University School of Medicine, Saint Louis, Missouri, USA.
authors.forename: M Kathryn
authors.initials: MK
authors.lastname: Liszewski
authors.affiliation: Cell Biology Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Lily
authors.initials: L
authors.lastname: Lu
authors.affiliation: Cell Biology Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Yi
authors.initials: Y
authors.lastname: Quan
authors.affiliation: Cell Biology Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Steve
authors.initials: S
authors.lastname: Balgobin
authors.affiliation: Department of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Schneppenheim
authors.affiliation: Medilys Laborgemeinschaft mbH, Coagulation Laboratory, Hamburg, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Schneppenheim
authors.affiliation: Medilys Laborgemeinschaft mbH, Coagulation Laboratory, Hamburg, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Budde
authors.affiliation: Clinical and Molecular Hemostasis Research Group, Queen's University, Kingston, Ontario, Canada.
authors.forename: Paula
authors.initials: P
authors.lastname: James
authors.affiliation: Department of Medicine, Division of Rheumatology, Washington University School of Medicine, Saint Louis, Missouri, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Atkinson
authors.affiliation: Program in Physiology and Experimental Medicine, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nades
authors.initials: N
authors.lastname: Palaniyar
authors.affiliation: Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada; Cell Biology Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Division of Haematology, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Walter H A
authors.initials: WH
authors.lastname: Kahr
authors.affiliation: Division of Nephrology, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada; Cell Biology Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada. Electronic address: christoph.licht@sickkids.ca.
authors.forename: Christoph
authors.initials: C
authors.lastname: Licht
mesh_terms: D065766:Atypical Hemolytic Uremic Syndrome / Q000276:immunology*; D001792:Blood Platelets / Q000276:immunology; D002448:Cell Adhesion / Q000276:immunology; D015932:Complement C3c / Q000378:metabolism; D003170:Complement Pathway, Alternative / Q000276:immunology*; D042783:Endothelial Cells / Q000276:immunology*; D006801:Humans; D007678:Kidney Glomerulus / Q000166:cytology; D061251:Primary Cell Culture; D011697:Purpura, Thrombotic Thrombocytopenic / Q000276:immunology*; D056729:von Willebrand Disease, Type 3 / Q000097:blood; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D014841:von Willebrand Factor; D015932:Complement C3c
keywords: atypical hemolytic uremic syndrome; blood outgrowth endothelial cells; complement; thrombotic microangiopathy; thrombotic thrombocytopenic purpura; von Willebrand factor