MEASUREMENT OF PLOIDY DISTRIBUTION IN MEGAKARYOCYTE COLONIES OBTAINED FROM CULTURE - WITH STUDIES OF THE EFFECTS OF THROMBOCYTOPENIA

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  • 1 January 1981
    • journal article
    • research article
    • Vol. 57  (2) , 287-297
Abstract
Microdensitometric measurement of the DNA content of individual megakaryocytes was performed using megakaryocyte [meg] colonies obtained following culture, in soft agar, of hematopoietic cells from C57BL/6J mice. Two types of colonies were detected. After 7 days of culture the big cell type contained 16 .+-. 2.3 acetylcholinesterase (AChE) positive cells/colony, with a mean ploidy level of 16.8 .+-. 0.8/cell and the ploidy distribution characteristic of recognizable megakaryocytes in bone marrow. The heterogeneous type contained 44 .+-. 9.6 cells/colony (some of which were AChE negative), with a mean ploidy level of 6.8 .+-. 0.7/cell. The ploidy distribution of heterogeneous colonies differed markedly from big cell colonies, with preponderance of 2N and 4N cells. Colony-forming cells [CFC] obtained 4-5 days after induction of acute thrombocytopenia, gave big cell colonies with a marked increase in DNA content. Mean ploidy level increased to 21.5 .+-. 1.8/cell; the frequency of 32N cells increased from 17-30% and 64N cells from 0-6%. This is the pattern of change observed in bone marrow, in vivo, 24-48 h after induction of acute thrombocytopenia. The number of cells/colony did not increase. Acute thrombocytopenia did not alter the ploidy of heterogeneous colonies. The different responses to the stimulus of acute thrombocytopenia suggest that there are at least 2 types of Meg-CFC. The delayed appearance of altered Meg-CFC that produce big cell colonies indicates that the pool of stem cells, from which committed megakaryocyte precursors are derived, may respond indirectly to the stimulus of platelet depletion.