title: Cellular origin of platelet-derived microparticles in vivo.
abstract: BACKGROUND
  Microparticles (MP), presumably of platelet origin, are the most abundant microparticles in blood. To which extent such MP may also directly originate from megakaryocytes, however, is unknown. During hematopoietic stem cell transplantation, patients undergo total body irradiation which leads to an irreversible destruction of hematopoiesis.
  
  
  METHODS
  We studied the levels of "platelet-derived" MP (PMP) in 13 patients before and after total body irradiation with 12 Gy (4 Gy for 3 days, dose rate 4.5 cGy/min). PMP were isolated and double-stained with annexin V and anti-CD61. In 6 patients, we additionally analyzed MP exposing P-selectin or CD63.
  
  
  RESULTS
  PMP rapidly declined upon total body irradiation, which was 2.4-fold faster than platelet disappearance. In contrast, the kinetics of MP exposing P-selectin or CD63 was comparable to platelets.
  
  
  CONCLUSIONS
  Since CD61-positive MP disappear faster than platelets or MP exposing P-selectin or CD63, our data indicate that MP exposing P-selectin or CD63 are likely to originate from platelets, whereas at least a major fraction of CD61-exposing MP is likely to originate from megakaryocytes in vivo.
authors.affiliation: Medizinische Klinik III-Großhadern, Klinikum der Ludwig Maximilians-Universität München, Marchioninistraße 15, 81377 München, Germany. andreas.rank@med.uni-muenchen.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Rank
authors.forename: Rienk
authors.initials: R
authors.lastname: Nieuwland
authors.forename: Ruth
authors.initials: R
authors.lastname: Delker
authors.forename: Anton
authors.initials: A
authors.lastname: Köhler
authors.forename: Bettina
authors.initials: B
authors.lastname: Toth
authors.forename: Verena
authors.initials: V
authors.lastname: Pihusch
authors.forename: Ralf
authors.initials: R
authors.lastname: Wilkowski
authors.forename: Rudolf
authors.initials: R
authors.lastname: Pihusch
mesh_terms: D000328:Adult; D001792:Blood Platelets / Q000378:metabolism* / Q000528:radiation effects*; D055252:Cell-Derived Microparticles / Q000378:metabolism* / Q000528:radiation effects*; D005260:Female; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D008297:Male; D014916:Whole-Body Irradiation / Q000009:adverse effects*; D055815:Young Adult