title: Clinical relevance of microparticles from platelets and megakaryocytes.
abstract: OBJECTIVE
  Platelet microparticles were identified more than 40 years ago and are the most abundant circulating microparticle subtype. Yet fundamental questions about their formation and role in human disease are just beginning to be understood at the cellular and molecular level. This review will address mechanisms of platelet microparticle generation and evaluate our current understanding of their clinical relevance.
  
  
  RESULTS
  New evidence indicates that the majority of CD41 microparticles circulating in healthy individuals derive directly from megakaryocytes. CD41 microparticles also form from activated platelets upon loss of cytoskeleton-membrane adhesion, which occurs in a multitude of disease states characterized by elevated platelet microparticle levels. More recent studies have demonstrated that platelet microparticles function as a transport and delivery system for bioactive molecules, participating in hemostasis and thrombosis, inflammation, malignancy infection transfer, angiogenesis, and immunity. The mechanism of platelet microparticle participation in specific disease entities such as rheumatoid arthritis has been elucidated.
  
  
  CONCLUSIONS
  Continued research into how platelet microparticles are generated and function as a transcellular delivery system will advance our basic understanding of microparticle physiology and may enable new strategies for treatment of select disease entities.
authors.affiliation: Division of Hemostasis and Thrombosis, Beth Israel Deaconess Medical Center, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA. jitaliano@rics.bwh.harvard.edu
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Italiano
authors.forename: Albert T A
authors.initials: AT
authors.lastname: Mairuhu
authors.forename: Robert
authors.initials: R
authors.lastname: Flaumenhaft
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000166:cytology*; D055252:Cell-Derived Microparticles; D006801:Humans; D008533:Megakaryocytes / Q000166:cytology*