title: Novel mechanisms of platelet clearance and thrombopoietin regulation.
abstract: OBJECTIVE
  The human body produces and removes 10 platelets daily to maintain a normal steady-state platelet count. Platelet production must be tightly regulated to avoid spontaneous bleeding or arterial occlusion and organ damage. Multifaceted and complex mechanisms control platelet removal and production in physiological and pathological conditions. This review will focus on different mechanisms of platelet clearance, with focus on the biological significance of platelet glycans.
  
  
  RESULTS
  The Ashwell-Morrell receptor (AMR) recognizes senescent, desialylated platelets under steady state conditions. Desialylated platelets and the AMR are the physiological ligand-receptor pair regulating hepatic thrombopoietin (TPO) mRNA production, resolving the longstanding mystery of steady state TPO regulation. The AMR-mediated removal of desialylated platelets regulates TPO synthesis in the liver by recruiting JAK2 and STAT3 to increase thrombopoiesis.
  
  
  CONCLUSIONS
  Inhibition of TPO production downstream of the hepatic AMR-JAK2 signaling cascade could additionally contribute to the thrombocytopenia associated with JAK1/2 treatment, which is clinically used in myeloproliferative neoplasms.
authors.affiliation: Division of Hematology, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Renata
authors.initials: R
authors.lastname: Grozovsky
authors.forename: Silvia
authors.initials: S
authors.lastname: Giannini
authors.forename: Hervé
authors.initials: H
authors.lastname: Falet
authors.forename: Karin M
authors.initials: KM
authors.lastname: Hoffmeister
mesh_terms: D001792:Blood Platelets / Q000378:metabolism*; D016922:Cellular Senescence / Q000502:physiology; D006801:Humans; D053614:Janus Kinase 2 / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D010976:Platelet Count; D012333:RNA, Messenger / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013921:Thrombocytopenia / Q000503:physiopathology; D034061:Thrombopoiesis / Q000502:physiology*; D013926:Thrombopoietin / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D050796:STAT3 Transcription Factor; D013926:Thrombopoietin; C507924:JAK2 protein, human; D053614:Janus Kinase 2