title: Ultrastructural study shows morphologic features of apoptosis and para-apoptosis in megakaryocytes from patients with idiopathic thrombocytopenic purpura.
abstract: To investigate whether altered megakaryocyte morphology contributes to reduced platelet production in idiopathic thrombocytopenic purpura (ITP), ultrastructural analysis of megakaryocytes was performed in 11 ITP patients. Ultrastructural abnormalities compatible with (para-)apoptosis were present in 78% +/- 14% of ITP megakaryocytes, which could be reversed by in vivo treatment with prednisone and intravenous immunoglobulin. Immunohistochemistry of bone marrow biopsies of ITP patients with extensive apoptosis showed an increased number of megakaryocytes with activated caspase-3 compared with normal (28% +/- 4% versus 0%). No difference, however, was observed in the number of bone marrow megakaryocyte colony-forming units (ITP, 118 +/- 93/105 bone marrow cells; versus controls, 128 +/- 101/105 bone marrow cells; P =.7). To demonstrate that circulating antibodies might affect megakaryocytes, suspension cultures of CD34+ cells were performed with ITP or normal plasma. Morphology compatible with (para-)apoptosis could be induced in cultured megakaryocytes with ITP plasma (2 of 10 samples positive for antiplatelet autoantibodies). Finally, the plasma glycocalicin index, a parameter of platelet and megakaryocyte destruction, was increased in ITP (57 +/- 70 versus 0.7 +/- 0.2; P =.009) and correlated with the proportion of megakaryocytes showing (para-) apoptotic ultrastructure (P =.02; r = 0.7). In conclusion, most ITP megakaryocytes show ultrastructural features of (para-) apoptosis, probably due to action of factors present in ITP plasma.
authors.affiliation: Department of Hematology, University Hospital Groningen, PO Box 30001, 9700 RB Groningen, The Netherlands. j.th.m.de.wolf@int.azg.nl
authors.forename: Ewout J
authors.initials: EJ
authors.lastname: Houwerzijl
authors.forename: Nel R
authors.initials: NR
authors.lastname: Blom
authors.forename: Johannes J L
authors.initials: JJ
authors.lastname: van der Want
authors.forename: Mariet T
authors.initials: MT
authors.lastname: Esselink
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Koornstra
authors.forename: Jan W
authors.initials: JW
authors.lastname: Smit
authors.forename: Henk
authors.initials: H
authors.lastname: Louwes
authors.forename: Edo
authors.initials: E
authors.lastname: Vellenga
authors.forename: Joost Th M
authors.initials: JT
authors.lastname: de Wolf
mesh_terms: D000328:Adult; D015703:Antigens, CD / Q000097:blood; D018952:Antigens, CD34 / Q000097:blood; D017209:Apoptosis / Q000502:physiology*; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008533:Megakaryocytes / Q000473:pathology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000473:pathology*; D012016:Reference Values; D013234:Stem Cells / Q000473:pathology
chemical_list: D015703:Antigens, CD; D018952:Antigens, CD34