title: Thrombin receptor levels in platelet concentrates during storage and their impact on platelet functionality.
abstract: BACKGROUND
  Quality control of platelet (PLT) concentrates is challenging, due to PLT lesions, which are difficult to detect with routine methods. The search for reliable PLT lesion biomarkers is focused on the role of PLTs in primary hemostasis. PLT transfusions also have a significant impact on secondary hemostasis. In this phase, responsiveness of PLTs to small amounts of thrombin is crucial. PAR1 and PAR4 are protease-activated receptors and are responsible for thrombin reactivity of human PLTs. This study should elucidate if levels of those two receptors are changing in PLT concentrates during storage and if those changes have an impact on PLT aggregation and support of thrombin generation.
  
  
  METHODS
  PLT concentrates from buffy coat preparations were stored in SSP+ solution for 9 days at 22±2°C on a horizontal flatbed agitator, and samples were taken daily for analysis. PAR1 and PAR4 levels were evaluated using Western blot analysis. PLT aggregation was measured using Born aggregometry and specific PAR1 or PAR4 agonists. Thrombin generation was measured using calibrated automated thrombography.
  
  
  RESULTS
  Levels of both receptors (PAR1 and PAR4) started to decrease after 5 days of storage. PAR1-mediated PLT aggregation remained constant, whereas PAR4-mediated PLT aggregation decreased with storage time. Rate of thrombin generation was accelerated after 5 days of storage.
  
  
  CONCLUSIONS
  Decreasing levels of PARs in PLT concentrates after 5 days of storage influenced PAR4-mediated, but not PAR1-mediated, aggregation. Thrombin generation with senescent PLTs was increased, which may be attributed to other mechanisms promoting increased phosphatidylserine exposure.
authors.affiliation: Department of General Pediatrics and Adolescent Medicine, Medical University of Graz, Graz, Austria.
authors.forename: Axel
authors.initials: A
authors.lastname: Schlagenhauf
authors.forename: Noemi
authors.initials: N
authors.lastname: Kozma
authors.forename: Bettina
authors.initials: B
authors.lastname: Leschnik
authors.forename: Thomas
authors.initials: T
authors.lastname: Wagner
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Muntean
mesh_terms: D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism* / Q000502:physiology*; D001793:Blood Preservation / Q000379:methods / Q000592:standards; D048430:Cell Shape; D006801:Humans; D066298:In Vitro Techniques; D015539:Platelet Activation / Q000502:physiology; D010974:Platelet Aggregation / Q000502:physiology; D010976:Platelet Count; D010983:Plateletpheresis / Q000592:standards; D011786:Quality Control; D044463:Receptor, PAR-1 / Q000032:analysis / Q000378:metabolism; D018179:Receptors, Thrombin / Q000032:analysis / Q000378:metabolism* / Q000502:physiology*; D013997:Time Factors
chemical_list: D044463:Receptor, PAR-1; D018179:Receptors, Thrombin; C112908:protease-activated receptor 4