title: Platelet-derived extracellular vesicles in plateletpheresis concentrates as a quality control approach.
abstract: BACKGROUND
  Platelet-derived extracellular vesicles (PL-EVs) are present in plateletpheresis concentrates (PCs) and may influence the quality of PCs. The aim of the study was to analyze PC-derived PL-EVs and to correlate them with standard quality control (QC) variables of PCs and with donor-specific laboratory variables.
  
  
  METHODS
  PL-EVs were analyzed by standard as well as advanced high-sensitivity flow cytometry (FCM) and nanoparticle tracking analysis. A hematology analyzer was applied to the determination of platelet (PLT) count and immature PLT fraction (IPF). Functional capacity of PLTs (CD62P in response to thrombin receptor-activating peptide 6 activation) was measured by FCM. All in vitro measurements were carried out on Day 0 and on Day 5. Altogether, a total of 42 PC samples, 15 irradiated on Day 0, were investigated.
  
  
  RESULTS
  Externalization of CD62P, as an indicator of intact PLT function, significantly decreased during in vitro PLT senescence and CD62P expression inversely correlated with increased PL-EV levels. Interestingly, in fresh PCs a significant correlation was found between PL-EVs and different hemapheresis instruments, duration of apheresis, and IPF count in peripheral blood of the donor before apheresis. In senescent PCs, the body mass index of donors inversely correlated with the PL-EV counts.
  
  
  CONCLUSIONS
  Loss of PLT function in PCs was associated with increased PL-EV levels. Shedding of PL-EVs depends on shear stress influenced by different hemapheresis settings and diverse preanalytical conditions of donors. PL-EV analysis may stimulate new quality and apheresis strategies for more vital PLTs for transfusion.
authors.affiliation: Institute for Laboratory Medicine and Transfusion Medicine, University of Regensburg, Regensburg, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Black
authors.affiliation: Institute for Laboratory Medicine and Transfusion Medicine, University of Regensburg, Regensburg, Germany.
authors.forename: Annika
authors.initials: A
authors.lastname: Pienimaeki-Roemer
authors.affiliation: Apogee Flow Systems Ltd., Hertfordshire, UK.
authors.forename: Oliver
authors.initials: O
authors.lastname: Kenyon
authors.affiliation: Institute for Laboratory Medicine and Transfusion Medicine, University of Regensburg, Regensburg, Germany.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Orsó
authors.affiliation: Institute for Laboratory Medicine and Transfusion Medicine, University of Regensburg, Regensburg, Germany.
authors.forename: Gerd
authors.initials: G
authors.lastname: Schmitz
mesh_terms: D001782:Blood Donors; D001792:Blood Platelets / Q000166:cytology*; D055252:Cell-Derived Microparticles; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D019007:P-Selectin / Q000097:blood*; D010983:Plateletpheresis / Q000379:methods*; D011786:Quality Control
chemical_list: D019007:P-Selectin; C546937:SELP protein, human