title: In vitro megakaryocyte differentiation and proplatelet formation in Ph-negative classical myeloproliferative neoplasms: distinct patterns in the different clinical phenotypes.
abstract: BACKGROUND
  Ph-negative myeloproliferative neoplasms (MPNs) are clonal disorders that include primary myelofibrosis (PMF), polycythemia vera (PV) and essential thrombocythemia (ET). Although the pathogenesis of MPNs is still incompletely understood, an involvement of the megakaryocyte lineage is a distinctive feature.
  
  
  RESULTS
  We analyzed the in vitro megakaryocyte differentiation and proplatelet formation in 30 PMF, 8 ET, 8 PV patients, and 17 healthy controls (CTRL). Megakaryocytes were differentiated from peripheral blood CD34(+) or CD45(+) cells in the presence of thrombopoietin. Megakaryocyte output was higher in MPN patients than in CTRL with no correlation with the JAK2 V617F mutation. PMF-derived megakaryocytes displayed nuclei with a bulbous appearance, were smaller than ET- or PV-derived megakaryocytes and formed proplatelets that presented several structural alterations. In contrast, ET- and PV-derived megakaryocytes produced more proplatelets with a striking increase in bifurcations and tips compared to both control and PMF. Proplatelets formation was correlated with platelet counts in patient peripheral blood. Patients with pre-fibrotic PMF had a pattern of megakaryocyte proliferation and proplatelet formation that was similar to that of fibrotic PMF and different from that of ET.
  
  
  CONCLUSIONS
  In conclusion, MPNs are associated with high megakaryocyte proliferative potential. Profound differences in megakaryocyte morphology and proplatelet formation distinguish PMF, both fibrotic and prefibrotic, from ET and PV.
authors.affiliation: Department of Biochemistry, University of Pavia, Pavia, Italy. alessandra.balduini@unipv.it
authors.forename: Alessandra
authors.initials: A
authors.lastname: Balduini
authors.forename: Stefania
authors.initials: S
authors.lastname: Badalucco
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Pugliano
authors.forename: Denis
authors.initials: D
authors.lastname: Baev
authors.forename: Annalisa
authors.initials: A
authors.lastname: De Silvestri
authors.forename: Marco
authors.initials: M
authors.lastname: Cattaneo
authors.forename: Vittorio
authors.initials: V
authors.lastname: Rosti
authors.forename: Giovanni
authors.initials: G
authors.lastname: Barosi
mesh_terms: D001792:Blood Platelets / Q000166:cytology*; D016022:Case-Control Studies; D002454:Cell Differentiation; D006801:Humans; D016130:Immunophenotyping; D066298:In Vitro Techniques; D008533:Megakaryocytes / Q000166:cytology*; D009154:Mutation; D009196:Myeloproliferative Disorders / Q000235:genetics / Q000276:immunology / Q000473:pathology*; D010677:Philadelphia Chromosome