21 results on '"Miyazaki, H."'
Search Results
2. The biologic properties of recombinant human thrombopoietin in the proliferation and megakaryocytic differentiation of acute myeloblastic leukemia cells
- Author
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Matsumura, I, primary, Kanakura, Y, additional, Kato, T, additional, Ikeda, H, additional, Horikawa, Y, additional, Ishikawa, J, additional, Kitayama, H, additional, Nishiura, T, additional, Tomiyama, Y, additional, Miyazaki, H, additional, and Matsuzawa, Y, additional
- Published
- 1996
- Full Text
- View/download PDF
3. p120c-cbl is present in human blood platelets and is differentially involved in signaling by thrombopoietin and thrombin
- Author
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Oda, A, primary, Ozaki, K, additional, Druker, BJ, additional, Miyakawa, Y, additional, Miyazaki, H, additional, Handa, M, additional, Morita, H, additional, Ohashi, H, additional, and Ikeda, Y, additional
- Published
- 1996
- Full Text
- View/download PDF
4. Thrombopoietin supports proliferation of human primitive hematopoietic cells in synergy with steel factor and/or interleukin-3
- Author
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Kobayashi, M, primary, Laver, JH, additional, Kato, T, additional, Miyazaki, H, additional, and Ogawa, M, additional
- Published
- 1996
- Full Text
- View/download PDF
5. Thrombopoietin primes human platelet aggregation induced by shear stress and by multiple agonists
- Author
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Oda, A, primary, Miyakawa, Y, additional, Druker, BJ, additional, Ozaki, K, additional, Yabusaki, K, additional, Shirasawa, Y, additional, Handa, M, additional, Kato, T, additional, Miyazaki, H, additional, Shimosaka, A, additional, and Ikeda, Y, additional
- Published
- 1996
- Full Text
- View/download PDF
6. Establishment and characterization of the thrombopoietin-dependent megakaryocytic cell line, UT-7/TPO
- Author
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Komatsu, N, primary, Kunitama, M, additional, Yamada, M, additional, Hagiwara, T, additional, Kato, T, additional, Miyazaki, H, additional, Eguchi, M, additional, Yamamoto, M, additional, and Miura, Y, additional
- Published
- 1996
- Full Text
- View/download PDF
7. Thrombopoietin induces tyrosine phosphorylation of Stat3 and Stat5 in human blood platelets
- Author
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Miyakawa, Y, primary, Oda, A, additional, Druker, BJ, additional, Miyazaki, H, additional, Handa, M, additional, Ohashi, H, additional, and Ikeda, Y, additional
- Published
- 1996
- Full Text
- View/download PDF
8. Recombinant human thrombopoietin (Mpl ligand) enhances proliferation of erythroid progenitors
- Author
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Kobayashi, M, primary, Laver, JH, additional, Kato, T, additional, Miyazaki, H, additional, and Ogawa, M, additional
- Published
- 1995
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- View/download PDF
9. Recombinant thrombopoietin induces rapid protein tyrosine phosphorylation of Janus kinase 2 and Shc in human blood platelets
- Author
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Miyakawa, Y, primary, Oda, A, additional, Druker, BJ, additional, Kato, T, additional, Miyazaki, H, additional, Handa, M, additional, and Ikeda, Y, additional
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- 1995
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- View/download PDF
10. In vivo efficacy of anti-MPL agonist antibody in promoting primary human hematopoietic cells.
- Author
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Kai M, Hagiwara T, Emuta C, Chisaka Y, Tsuruhata K, Endo C, Inagaki Y, Miyazaki H, and Kataoka S
- Subjects
- Animals, Antigens, CD34 metabolism, Blood Cells metabolism, Bone Marrow Cells metabolism, Flow Cytometry, Humans, Leukocyte Common Antigens metabolism, Male, Mice, Platelet Membrane Glycoprotein IIb metabolism, Receptors, Thrombopoietin immunology, Antibodies pharmacology, Blood Cells drug effects, Bone Marrow Cells drug effects, Receptors, Thrombopoietin agonists
- Abstract
In a previous study, we generated novel antithrombopoietin receptor agonist antibodies as therapeutic candidates. In this report, we investigated the in vivo effects of one of these antibodies, MA01G4344U, on primary human hematopoietic cells using xenotransplantation. NOD/Shi-scid, IL-2Rgamma(null) (NOG) mice were pretreated by total-body irradiation and received a transplant of human cord blood-derived CD34(+) cells. Weekly intraperitoneal injection of MA01G4344U (100 microg/mouse per week) or Peg-rhMGDF (5 microg/mouse per week) or phosphate-buffered saline (PBS) was performed. Human cells in peripheral blood were analyzed by flow cytometry and bone marrow cells were analyzed by flow cytometry and colony assay. MA01G4344U successfully increased the number of human CD41(+) platelets and human CD45(+) cells in peripheral blood. In the bone marrow, MA01G4344U increased the number of human CD45(+)/CD34(+) cells, which resulted in more multilineage progenitor cells. The efficacy of MA01G4344U in promoting primary human hematopoietic cells in vivo suggests its therapeutic potential for thrombocytopenic and pancytopenic disorders.
- Published
- 2009
- Full Text
- View/download PDF
11. WAVE/Scars in platelets.
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Oda A, Miki H, Wada I, Yamaguchi H, Yamazaki D, Suetsugu S, Nakajima M, Nakayama A, Okawa K, Miyazaki H, Matsuno K, Ochs HD, Machesky LM, Fujita H, and Takenawa T
- Subjects
- Actin Cytoskeleton metabolism, Animals, COS Cells, Calpain metabolism, Chlorocebus aethiops, Humans, Isomerism, Platelet Aggregation physiology, Proteins genetics, Proteins metabolism, Substrate Specificity, Wiskott-Aldrich Syndrome Protein Family, Blood Platelets physiology, Microfilament Proteins genetics, Microfilament Proteins metabolism
- Abstract
Using specific antibodies against isoforms of WAVE (WASP [Wiskott-Aldrich syndrome protein] family Verprolin-homologous protein, also called Scar), we demonstrated that human platelets express all 3 isoforms. With the use of an in vitro pull-down technique, the src homology 3 (SH3) domain of insulin receptor substrate p53 (IRSp53) precipitated WAVE2 from platelet lysates more efficiently than did profilin I. The opposite was true for WAVE1, and neither precipitated WAVE3, suggesting that WAVE isoforms have different affinities to these ligands, while the SH3 domain of abl binds to all 3 isoforms. The 3 WAVE isoforms were distributed in the actin-rich Triton X-100-insoluble pellets following platelet aggregation induced by thrombin receptor-activating peptide. We also found that all 3 WAVE isoforms are substrates for calpain in vivo and in vitro. Although portions of these 3 isoforms were commonly distributed in the actin- and actin-related protein 2 and 3 (Arp2/3)-rich edge of the lamellipodia in spreading platelets, only WAVE2 remained in the cell fringe following detergent extraction or fixation of the cells. Finally, by mass spectrometry, we found that the proteins, which reportedly interact with WAVE/Scars, are present in platelets. These data suggest that the 3 WAVE isoforms exhibit common and distinct features and may potentially be involved in the regulation of actin cytoskeleton in platelets.
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- 2005
- Full Text
- View/download PDF
12. Familial essential thrombocythemia associated with a dominant-positive activating mutation of the c-MPL gene, which encodes for the receptor for thrombopoietin.
- Author
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Ding J, Komatsu H, Wakita A, Kato-Uranishi M, Ito M, Satoh A, Tsuboi K, Nitta M, Miyazaki H, Iida S, and Ueda R
- Subjects
- Cells, Cultured, Female, Genes, Dominant, Humans, Japan, Male, Neoplasm Proteins metabolism, Pedigree, Phosphorylation, Proto-Oncogene Proteins metabolism, Receptors, Cytokine metabolism, Receptors, Thrombopoietin, Signal Transduction physiology, Thrombopoietin metabolism, Transfection, Neoplasm Proteins genetics, Point Mutation, Proto-Oncogene Proteins genetics, Receptors, Cytokine genetics, Thrombocythemia, Essential genetics
- Abstract
One Japanese pedigree of familial essential thrombocythemia (FET) inherited in an autosomal-dominant manner is presented. A unique point mutation, serine 505 to asparagine 505 (Ser505Asn), was identified in the transmembrane domain of the c-MPL gene in all of the 8 members with thrombocythemia, but in none of the other 8 unaffected members in this FET family. The Ba/F3 cells expressing the mutant Asn505 acquired interleukin 3 (IL-3)-independent survival capacity, whereas those expressing wild-type Ser505 did not. The autonomous phosphorylation of Mek1/2 and Stat5b was observed in the mutant Ba/F3 cells in the absence of IL-3. The former was also found in platelets derived from the affected individual in the absence of thrombopoietin. These results show that the Asn505 is an activating mutation with respect to the intracellular signaling and survival of the cells. This is the first report of FET deriving from a dominant-positive activating mutation of the c-MPL gene.
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- 2004
- Full Text
- View/download PDF
13. Production of functional platelets by differentiated embryonic stem (ES) cells in vitro.
- Author
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Fujimoto TT, Kohata S, Suzuki H, Miyazaki H, and Fujimura K
- Subjects
- Animals, Blood Platelets metabolism, Cell Differentiation, Cell Size, Coculture Techniques, Megakaryocytes cytology, Mice, Microscopy, Electron, Platelet Function Tests, Stromal Cells cytology, Time Factors, Transfection, Blood Platelets cytology, Cell Culture Techniques methods, Stem Cells cytology, Thrombopoiesis
- Abstract
Megakaryocytes and functional platelets were generated in vitro from murine embryonic stem (ES) cells with the use of a coculture system with stromal cells. Two morphologically distinctive megakaryocytes were observed sequentially. Small megakaryocytes rapidly produced proplatelets on day 8 of the differentiation, and large hyperploid megakaryocytes developed after day 12, suggesting primitive and definitive megakaryopoiesis. Two waves of platelet production were consistently observed in the culture medium. A larger number of platelets was produced in the second wave; 104 ES cells produced up to 108 platelets. By transmission electron microscopy, platelets from the first wave were relatively rounder with a limited number of granules, but platelets from the second wave were discoid shaped with well-developed granules that were indistinguishable from peripheral blood platelets. ES-derived platelets were functional since they bound fibrinogen, formed aggregates, expressed P-selectin upon stimulation, and fully spread on immobilized fibrinogen. These results show the potential utility of ES-derived platelets for clinical applications. Furthermore, production of gene-transferred platelets was achieved by differentiating ES cells that were transfected with genes of interest. Overexpression of the cytoplasmic domain of integrin beta3 in the ES-derived platelets prevented the activation of alphaIIbbeta3, demonstrating that this system will facilitate functional platelet studies.
- Published
- 2003
- Full Text
- View/download PDF
14. Autoantibodies neutralizing thrombopoietin in a patient with amegakaryocytic thrombocytopenic purpura.
- Author
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Shiozaki H, Miyawaki S, Kuwaki T, Hagiwara T, Kato T, and Miyazaki H
- Subjects
- Aged, Autoantibodies blood, Cyclosporine pharmacology, Female, Humans, Immunoglobulin G blood, Immunosuppressive Agents pharmacology, Purpura, Thrombocytopenic blood, Thrombopoietin blood, Time Factors, Autoantibodies immunology, Megakaryocytes immunology, Purpura, Thrombocytopenic immunology, Thrombopoietin immunology
- Published
- 2000
15. Production of thrombopoietin by human carcinomas and its novel isoforms.
- Author
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Sasaki Y, Takahashi T, Miyazaki H, Matsumoto A, Kato T, Nakamura K, Iho S, Okuno Y, and Nakao K
- Subjects
- Amino Acid Sequence, Animals, COS Cells, DNA Transposable Elements, Female, Genetic Variation, HeLa Cells, Humans, Molecular Sequence Data, Protein Isoforms biosynthesis, Protein Isoforms chemistry, Protein Isoforms genetics, RNA, Messenger genetics, Recombinant Proteins biosynthesis, Recombinant Proteins chemistry, Reverse Transcriptase Polymerase Chain Reaction, Sequence Alignment, Sequence Deletion, Thrombopoietin biosynthesis, Thrombopoietin chemistry, Transfection, Tumor Cells, Cultured, Thrombopoietin genetics, Transcription, Genetic
- Abstract
Thrombocytosis is occasionally seen in patients with carcinomas and has been assumed to be attributable to interleukin-6 or granulocyte-macrophage colony-stimulating factor produced by carcinoma cells. In this study, we clarified whether thrombopoietin (TPO) is involved in carcinoma-associated thrombocytosis. Expression of TPO mRNA was observed in the majority of 27 carcinoma cell lines as determined by reverse transcriptase-polymerase chain reaction (RT-PCR). There were 6 PCR products differing in size; sequence analysis showed the full-length TPO mRNA (TPO-1), 12- and 116-bp deleted variants (TPO-2 and TPO-3, respectively), and 3 novel isoforms (197- and 128-bp deleted forms and a 60-bp insert form of TPO-3; named TPO-4, TPO-5, and TPO-6, respectively). Of 27 lines, 24 expressed TPO-1 mRNA with various other isoforms. Culture supernatants of COS-1 cells transfected with TPO-5 or TPO-6 cDNA did not promote the proliferation of TPO-responsive cells, whereas Western blot analysis on the cell lysates demonstrated TPO-5 but not TPO-6 protein, suggesting poor extracellular secretion (TPO-5) or poor protein synthesis (TPO-6). TPO protein was detected in 10-fold concentrated culture supernatants of cells of these carcinoma lines, with a median concentration of 0.38 fmol/mL as evaluated by enzyme-linked immunosorbent assay. High blood TPO levels were observed with a median value of 3.46 fmol/mL (range, 0.34 to 8.67 fmol/mL) in patients with advanced carcinomas associated with thrombocytosis. These results indicate that thrombocytosis in patients with carcinomas might be caused, at least in part, by TPO produced by carcinoma cells.
- Published
- 1999
16. Thrombopoietin augments stem cell factor-dependent growth of human mast cells from bone marrow multipotential hematopoietic progenitors.
- Author
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Sawai N, Koike K, Mwamtemi HH, Kinoshita T, Kurokawa Y, Sakashita K, Higuchi T, Takeuchi K, Shiohara M, Kamijo T, Ito S, Kato T, Miyazaki H, Yamashita T, and Komiyama A
- Subjects
- Cell Differentiation drug effects, Cell Division drug effects, Cells, Cultured, Drug Synergism, Flow Cytometry, Humans, Hematopoietic Stem Cells cytology, Mast Cells cytology, Stem Cell Factor pharmacology, Thrombopoietin pharmacology
- Abstract
The effects of thrombopoietin (TPO) and/or stem cell factor (SCF) on the development of human mast cells from CD34(+) bone marrow (BM) cells were investigated using a serum-deprived liquid culture system. Mast cells were identified by measurement of intracellular histamine content, immunocytochemical staining, and flow cytometric analysis. Whereas SCF alone generated only a small number of tryptase+ cells, the addition of TPO to the culture containing SCF resulted in an apparent production of mast cells from 3 weeks until at least 15 weeks. Some of the cells reacted with an antichymase monoclonal antibody as well. Based on the effects of growth factor(s) on a later phase of the mast cell growth, TPO may stimulate an early stage of mast cell development in combination with SCF, whereas subsequent growth seems to be supported by SCF alone. Single-cell culture studies indicated that the CD34(+)CD38(-)c-kit+ cells and CD34(+)CD38(+)c-kit+ cells were responsible for the SCF + TPO-dependent mast cell production. Two-step culture assays clearly showed that mast cells originated from multilineage colony-forming cells that had potential to differentiate into neutrophil/mast cell lineages, neutrophil/macrophage/mast cell lineages, or neutrophil/macrophage/mast cell/erythroid lineages. These results suggest that TPO plays an important role in the development of human mast cells from CD34(+) BM cells in concert with SCF, and provide direct evidence of the differentiation into the mast cell lineage of human multipotential BM-derived progenitors.
- Published
- 1999
17. Neutrophilic cell production by combination of stem cell factor and thrombopoietin from CD34(+) cord blood cells in long-term serum-deprived liquid culture.
- Author
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Sawai N, Koike K, Ito S, Mwamtemi HH, Kurokawa Y, Kinoshita T, Sakashita K, Higuchi T, Takeuchi K, Shiohara M, Miyazaki H, Kato T, and Komiyama A
- Subjects
- ADP-ribosyl Cyclase, ADP-ribosyl Cyclase 1, Antigens, Differentiation analysis, Cells, Cultured, Culture Media, Serum-Free, Flow Cytometry, Granulocyte Colony-Stimulating Factor pharmacology, Granulocyte-Macrophage Colony-Stimulating Factor pharmacology, Humans, Immunohistochemistry, Immunophenotyping, Membrane Glycoproteins, NAD+ Nucleosidase analysis, Peroxidase, Proto-Oncogene Proteins c-kit analysis, Time Factors, Antigens, CD, Antigens, CD34 analysis, Fetal Blood cytology, Hematopoiesis, Neutrophils cytology, Stem Cell Factor pharmacology, Thrombopoietin pharmacology
- Abstract
In the present study, we investigated the effects of stem cell factor (SCF) and/or thrombopoietin (TPO) on the cell production by cord blood CD34(+) cells using a serum-deprived liquid culture system. Although SCF alone supported a modest production of neutrophilic cells and a remarkable generation of mast cells, the addition of TPO to the culture containing SCF caused an apparent generation of neutrophilic cells, identified by immunocytochemical staining and flow cytometric analysis. The significant production of neutrophilic cells by SCF and TPO was persistently observed from 2 weeks to 2 to 3 months of culture. The interaction between SCF and TPO on the neutrophilic cell generation was greater than the combined effects of SCF with granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF). The addition of neutralizing antibody against G-CSF or GM-CSF did not influence the SCF + TPO-dependent neutrophilic cell production. A single-cell culture study showed that not only CD34(+)CD38(+) c-kit+ cells but also CD34(+)CD38(-)c-kit+ cells were responsible for the neutrophilic cell generation. In clonal cell cultures, GM progenitors as well as erythroid progenitors and multipotential progenitors expanded in the cultures supplemented with SCF and TPO. The neutrophilic cells grown by SCF + TPO were at myeloblast to band cell stages, and scarcely matured to segmented neutrophils. In addition, the cells generated by SCF + TPO were stained with monoclonal antibodies against myeloperoxidase, elastase, lactoferrin, and CD11b, but they had negligible levels of alkaline phosphatase (ALP) and CD35. The replating of the CD34(-)c-kit-/low CD15(+) cells grown by SCF + TPO into a culture containing SCF + G-CSF permitted both the terminal maturation into segmented cells and the appearance of ALP and CD35. These results indicate the existence of a G-CSF/GM-CSF-independent system of neutrophilic cell production.
- Published
- 1999
18. Thrombopoietin promotes the survival of murine hematopoietic long-term reconstituting cells: comparison with the effects of FLT3/FLK-2 ligand and interleukin-6.
- Author
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Matsunaga T, Kato T, Miyazaki H, and Ogawa M
- Subjects
- Animals, Cell Differentiation drug effects, Cell Division drug effects, Cell Survival drug effects, Female, Hematopoiesis, Hematopoietic Stem Cells physiology, Mice, Mice, Inbred C57BL, Time Factors, Whole-Body Irradiation, Hematopoietic Stem Cell Transplantation, Hematopoietic Stem Cells pathology, Interleukin-6 pharmacology, Membrane Proteins pharmacology, Radiation-Protective Agents pharmacology, Thrombopoietin pharmacology
- Abstract
The effects of thrombopoietin (TPO; c-mpl ligand), FLT3/FLK-2 ligand (FL), and interleukin-6 (IL-6) on the survival of murine hematopoietic long-term reconstituting cells (LTRC) were studied by using lineage-negative, Sca-1-positive, c-kit-positive (Lin-Sca-1(+)c-kit+) marrow cells from 5-fluorouracil-treated mice. We tested the ability of these cytokines to maintain the viability of LTRC by transplanting the cultured cells to lethally irradiated Ly-5 congenic mice together with compromised marrow cells. As a single agent, only TPO could maintain the LTRC. Neither IL-6 nor FL was effective by itself, but they acted synergistically to maintain the LTRC. We examined whether the maintenance of LTRC by these cytokines was due to the survival of stem cells or was the result of active cell divisions and self-renewal. To monitor cell division, we used membrane dye PKH26. Enriched cells were stained with PKH26 on day 0 and incubated in suspension culture with TPO or with IL-6 and FL for 7 days. On day 7, PKH26(low) and PKH26(high) cells were prepared by sorting and their in vivo reconstituting abilities were tested by transplantation into lethally irradiated Ly-5 congenic mice together with compromised marrow cells. PKH26(high) populations cultured with both TPO alone and the combination of IL-6 and FL showed greater reconstitution activity than that of PKH26(low) populations. These data indicate that TPO alone and the combination of IL-6 and FL can support the survival of stem cells without stimulating their active cell proliferation.
- Published
- 1998
19. Multilineage hematopoietic recovery by a single injection of pegylated recombinant human megakaryocyte growth and development factor in myelosuppressed mice.
- Author
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Shibuya K, Akahori H, Takahashi K, Tahara E, Kato T, and Miyazaki H
- Subjects
- Animals, Blood Cell Count, Colony-Forming Units Assay, Drug Evaluation, Preclinical, Enzyme-Linked Immunosorbent Assay, Filgrastim, Granulocyte Colony-Stimulating Factor pharmacology, Granulocyte Colony-Stimulating Factor therapeutic use, Hematopoietic Stem Cells pathology, Humans, Injections, Intravenous, Male, Megakaryocytes pathology, Mice, Mice, Inbred BALB C, Polyethylene Glycols administration & dosage, Polyethylene Glycols pharmacology, Recombinant Proteins administration & dosage, Recombinant Proteins pharmacology, Recombinant Proteins therapeutic use, Thrombopoietin administration & dosage, Thrombopoietin pharmacology, Whole-Body Irradiation, Bone Marrow Diseases drug therapy, Hematopoiesis drug effects, Polyethylene Glycols therapeutic use, Radiation Injuries, Experimental drug therapy, Thrombopoietin therapeutic use
- Abstract
Previous studies have shown that daily multiple administration of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) markedly stimulates thrombopoiesis and effectively ameliorates thrombocytopenia, and in most cases anemia and neutropenia, in myelosuppressed animals. In this study, we evaluated the effects of a single intravenous injection of PEG-rHuMGDF on hematopoietic recovery after sublethal total-body irradiation in mice. A single injection of PEG-rHuMGDF (1 to 640 microg/kg) 1 hour after irradiation accelerated platelet, red blood cell (RBC), and white blood cell (WBC) recovery in a dose-dependent fashion. In the bone marrow of vehicle-treated mice, megakaryocytic, erythroid, and myeloid progenitors, as well as day 12 colony-forming unit-spleen (CFU-S), were dramatically decreased much earlier than the nadirs of peripheral blood cells, whereas megakaryocytes were modestly decreased. Treatment with PEG-rHuMGDF (80 microg/kg, an optimal dose) 1 hour after irradiation resulted in more rapid recovery of these four hematopoietic progenitors and also significantly facilitated megakaryocyte recovery. In addition, the same PEG-rHuMGDF administration schedule expanded bone marrow cells capable of rescuing lethally irradiated recipient mice. As the interval between irradiation and PEG-rHuMGDF treatment was longer, its effects on hematopoietic recovery were attenuated. In contrast to the effects of PEG-rHuMGDF, a single injection of recombinant human granulocyte colony-stimulating factor (rhG-CSF) 1 hour after irradiation exclusively accelerated WBC recovery, but only to a similar extent as PEG-rHuMGDF (80 microg/kg) treatment even when rhG-CSF doses were escalated to 1,000 microg/kg. This appeared related to different pharmacokinetics of these two factors after a single injection in irradiated mice. The concentrations of PEG-rHuMGDF after injection persisted in the plasma for a longer time compared with rhG-CSF. These results indicate that a single injection of PEG-rHuMGDF at an early time after irradiation is able to effectively improve thrombocytopenia, anemia, and leukopenia with concomitant accelerated recovery of both primitive and committed hematopoietic progenitors in irradiated mice. Our data also show that compared with the rhG-CSF shown to exert multilineage effects on hematopoiesis, PEG-rHuMGDF has more wide-ranging effects on peripheral blood cell recovery.
- Published
- 1998
20. Markedly reduced expression of platelet c-mpl receptor in essential thrombocythemia.
- Author
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Horikawa Y, Matsumura I, Hashimoto K, Shiraga M, Kosugi S, Tadokoro S, Kato T, Miyazaki H, Tomiyama Y, Kurata Y, Matsuzawa Y, and Kanakura Y
- Subjects
- Adolescent, Adult, Aged, Aged, 80 and over, Female, Humans, Male, Middle Aged, Proto-Oncogene Mas, RNA, Messenger analysis, RNA, Messenger metabolism, Receptors, Immunologic biosynthesis, Receptors, Thrombopoietin, Blood Platelets metabolism, Neoplasm Proteins, Proto-Oncogene Proteins biosynthesis, Receptors, Cytokine, Thrombocytosis blood, Thrombopoietin metabolism
- Abstract
Thrombopoietin (TPO) is implicated as a primary regulator of megakaryopoiesis and thrombopoiesis through binding to the cytokine receptor c-Mpl (the product of the c-mpl proto-oncogene). In an effort to determine the pathophysiological role of TPO-c-Mpl system in essential thrombocythemia (ET), we have examined the levels of serum TPO and the expression and function of platelet c-Mpl in 17 patients with ET. In spite of extreme thrombocytosis, serum TPO levels were slightly elevated or within normal range in most, if not all, patients with ET (mean +/- SD, 1.31 +/- 1.64 fmol/mL), as compared with normal subjects (0.76 +/- 0.21 fmol/mL). Flow cytometric and Western blot analyses revealed that the expression of platelet c-Mpl was strikingly reduced in all patients with ET. Furthermore, the expression of platelet c-mpl mRNA was found to be significantly decreased in the ET patients tested. In contrast, almost identical levels of GPIIb/IIIa protein and mRNA were expressed in platelets from ET patients and normal controls. In addition to expression level, activation state of platelet c-Mpl was investigated in ET patients. Immunoblotting with anti-phosphotyrosine antibody showed that no aberrant protein-tyrosine phosphorylation was observed in platelets of ET patients before treatment with TPO, and the levels of TPO-induced protein-tyrosine phosphorylation, including c-Mpl-tyrosyl phosphorylation, roughly paralleled those of c-Mpl expression, suggesting that c-Mpl-mediated signaling pathway was not constitutively activated in platelets of ET patients. These results suggested that the TPO-c-Mpl system may not be directly linked to pathogenesis of ET, and that gene(s) mutated in ET may be important in regulating the levels of c-mpl gene expression in addition to the growth and differentiation of multipotential hematopoietic stem cells.
- Published
- 1997
21. Thrombopoietin in Upshaw-Schulman syndrome.
- Author
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Miura M, Koizumi S, and Miyazaki H
- Subjects
- Anemia, Aplastic blood, Blood Transfusion, Humans, Plasma, Platelet Count, Purpura, Thrombocytopenic, Idiopathic blood, Syndrome, Thrombocytopenia congenital, Thrombopoietin physiology, Anemia, Hemolytic, Congenital blood, Thrombocytopenia blood, Thrombopoietin blood
- Published
- 1997
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