title: The contribution of von Willebrand factor-GPIbα interactions to persistent aggregate formation in apheresis platelet concentrates.
abstract: OBJECTIVE
  Apheresis platelet concentrates sometimes contain persistent aggregates (PA). Because apheresis involves extracorporeal circulation, we hypothesized that interactions between GPIbα and von Willebrand factor (VWF) underlie their origin.
  
  
  METHODS
  Platelets in donations with PA were compared to aggregate-free (AF) controls. Flow cytometry was used to determine platelet bound VWF. Degranulation was measured using P-selectin expression in flow cytometry and cytokine release using immunosorbent assays. Platelet adhesion to VWF was assessed in hydrodynamic flow and real-time video microscopy.
  
  
  RESULTS
  Platelets in PA concentrates had significantly more (P = 0·009, n ≥ 8) bound VWF compared to AF platelets, but differences in VWF concentration, VWF collagen binding, activated VWF or GPIbα expression were not found. Degranulation was higher (P = 0·030, n = 7) in PA than AF concentrates on day 1 of storage, but adhesion to immobilized VWF under hydrodynamic flow conditions was normal at that moment. On day 6, however, significantly less VWF adhesion (P = 0·009, n ≥ 6) was found for PA platelets compared to AF, indicating accelerated storage lesion in PA products. In a model that mimicks PA formation by chemically induced binding of VWF to platelets, we found that degranulation, phosphatidylserine expression and metabolism did not differ with paired controls at any time during subsequent storage.
  
  
  CONCLUSIONS
  Accelerated storage lesion is found in concentrates with PA, but this cannot be explained solely by increased platelet bound VWF following apheresis. Therefore, additional stressors are probably responsible for the increases observed in platelet degranulation and storage lesion in products with PA.
authors.affiliation: Transfusion Research Center, Belgian Red Cross-Flanders, Ghent, Belgium.
authors.forename: H B
authors.identifier: http://orcid.org/0000-0003-0052-8852
authors.initials: HB
authors.lastname: Feys
authors.affiliation: Transfusion Research Center, Belgian Red Cross-Flanders, Ghent, Belgium.
authors.forename: B
authors.initials: B
authors.lastname: Van Aelst
authors.affiliation: Transfusion Research Center, Belgian Red Cross-Flanders, Ghent, Belgium.
authors.forename: R
authors.initials: R
authors.lastname: Devloo
authors.affiliation: Blood Service of the Belgian Red Cross-Flanders, Mechelen, Belgium.|Faculty of Medicine and Health Sciences, University of Ghent, Ghent, Belgium.|Department of Public Health and Primary Care, Catholic University of Leuven, Leuven, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Vandekerckhove
authors.affiliation: Transfusion Research Center, Belgian Red Cross-Flanders, Ghent, Belgium.|Blood Service of the Belgian Red Cross-Flanders, Mechelen, Belgium.|Department of Clinical Chemistry, Microbiology and Immunology, University of Ghent, Ghent, Belgium.
authors.forename: V
authors.initials: V
authors.lastname: Compernolle
mesh_terms: D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism*; D001793:Blood Preservation; D016207:Cytokines / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D057446:Hydrodynamics; D046210:Microfluidic Analytical Techniques; D018715:Microscopy, Video; D010974:Platelet Aggregation / Q000502:physiology*; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000737:chemistry / Q000378:metabolism*; D010983:Plateletpheresis; D011485:Protein Binding; D014841:von Willebrand Factor / Q000737:chemistry / Q000378:metabolism*
chemical_list: D016207:Cytokines; D019038:Platelet Glycoprotein GPIb-IX Complex; D014841:von Willebrand Factor
keywords: aggregates; apheresis; platelets; storage lesion; von Willebrand factor