title: Platelet microparticles are heterogeneous and highly dependent on the activation mechanism: studies using a new digital flow cytometer.
abstract: BACKGROUND
  Platelet-derived microparticles (MPs) are believed to play an important role in coagulation and inflammatory disorders. Unfortunately, MP size renders them difficult to study and analyze by conventional flow cytometry.
  
  
  METHODS
  We analyzed and characterized platelet-derived MPs, using antibodies against the major surface glycoproteins (GP), the platelet activation antigen P-selectin (CD62P), and a marker of procoagulant activity (phosphatidylserine exposure). MPs were generated by exposure of platelets to thrombin receptor activating peptide (TRAP) or ionophore. Both agonists induced significant microvesiculation of platelets, and the resulting MPs were analyzed by a new digital flow cytometer: Becton-Dickinson FACSAria.
  
  
  RESULTS
  Membrane GPs were equally well represented in MPs generated by either reagent. In contrast, P-selectin was more intensely expressed in TRAP-MPs, while phosphatidylserine (PS) expression was markedly increased in ionophore-MPs. Two distinct populations of TRAP-MPs (one PS-positive and another PS-negative) were apparent. The latter characteristic facilitated sorting of MPs according to their PS exposure.
  
  
  CONCLUSIONS
  The data presented herein show a significant improvement in the methodology applied until now to the characterization of MPs. The ability to characterize and sort MP subpopulations may help to resolve their contributions to normal and pathological functions.
authors.affiliation: Department of Medicine, University of Minnesota Medical School, Minneapolis, Minnesota, USA.
authors.forename: Sílvia
authors.initials: S
authors.lastname: Perez-Pujol
authors.forename: Paul H
authors.initials: PH
authors.lastname: Marker
authors.forename: Nigel S
authors.initials: NS
authors.lastname: Key
mesh_terms: D000135:Acid Phosphatase / Q000494:pharmacology; D017304:Annexin A5 / Q000097:blood; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D000001:Calcimycin / Q000494:pharmacology; D005434:Flow Cytometry / Q000379:methods*; D039661:Integrin beta3 / Q000097:blood; D007527:Isoenzymes / Q000494:pharmacology; D019007:P-Selectin / Q000097:blood; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology*; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000032:analysis; D000071681:Tartrate-Resistant Acid Phosphatase
chemical_list: D017304:Annexin A5; D039661:Integrin beta3; D007527:Isoenzymes; D019007:P-Selectin; D019038:Platelet Glycoprotein GPIb-IX Complex; D000001:Calcimycin; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase