title: Different radiosensitive megakaryocytic progenitor cells exist in steady-state human peripheral blood.
abstract: CD34 antigen is a novel marker for human hematopoietic stem/progenitor cells. In the present study, two cell fractions, CD34low and CD34high, were prepared from steady-state human peripheral blood on the basis of CD34 antigen expression. The colony-forming unit megakaryocytes (CFU-Meg) contained in each cell fraction were compared for X-radiation sensitivity and cytokine action. The content of CD34+CD45+ cells in the CD34low and CD34high cell fractions was 74.8% and 88.8%, respectively, and the frequency of thrombopoietin (TPO)-supported CFU-Meg in the CD34low cell fraction was 1.9 times higher than that in CD34high. The CFU-Meg in CD34high were more radiosensitive than those in CD34low, indicating that steady-state human peripheral blood contains different types of CFU-Meg. However, no significant differences were observed between cell fractions in the radiation survival curves of CFU-Meg stimulated by TPO plus cytokines except granulocyte colony-stimulating factor (G-CSF). TPO plus interleukin 3 was the optimal combination for survival of both types of CFU-Meg after X irradiation. The present study also demonstrated that TPO plus G-CSF is able to increase the survival of irradiated CD34low CFU-Meg. These results suggest that two megakaryocytic progenitor populations with different radiosensitivity and cytokine responses are found in steady-state human peripheral blood.
authors.affiliation: Laboratory of Radiological Technology, Hirosaki University School of Health Sciences, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan. ikashi@cc.hirosaki-u.ac.jp
authors.forename: Ikuo
authors.initials: I
authors.lastname: Kashiwakura
authors.forename: Osamu
authors.initials: O
authors.lastname: Inanami
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Abe
authors.forename: Tsuneo A
authors.initials: TA
authors.lastname: Takahashi
authors.forename: Mikinori
authors.initials: M
authors.lastname: Kuwabara
mesh_terms: D018952:Antigens, CD34 / Q000378:metabolism*; D002469:Cell Separation; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D004307:Dose-Response Relationship, Radiation; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D008533:Megakaryocytes / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects*; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000187:drug effects / Q000502:physiology*
chemical_list: D018952:Antigens, CD34; D016207:Cytokines