Effect of recombinant granulocyte-macrophage colony-stimulating factor on
murine thrombocytopoiesis in vitro and in vivo
T Ishibashi, H Kimura, Y Shikama, T Uchida, S Kariyone and Y Maruyama
First Department of Internal Medicine, Fukushima Medical College, Japan.
To investigate the effect of recombinant granulocyte-macrophage colony-
stimulating factor (rGM-CSF) on murine megakaryocytopoiesis in vitro, the
factor was added to both serum-free colony assays and liquid marrow
cultures. GM-CSF had a significant megakaryocytic colony-stimulating
activity. After 2 hours of preincubation with and without 10 ng/mL rGM-
CSF, the percentage of megakaryocyte colony-forming cell (CFU-MK) in DNA
synthesis was determined by tritiated-thymidine suicide using colony
growth. The reduction of CFU-MK colony numbers in marrow culture was 47.5%
+/- 9.9%, 20.9% +/- 5.2% (control), respectively, indicating that the
factor affected cell cycle at CFU-MK levels. When acetylcholinesterase
(AchE) production was measured fluorometrically after 4 days of liquid
culture, rGM-CSF elicited an increase in AchE activity in a dose-dependent
fashion. To determine if the hematopoietin acts directly on megakaryocytic
differentiation, 2 ng/mL rGM-CSF was added to serum-free cultures of 295
single megakaryocytes isolated from CFU-MK colonies. An increase in size
was observed in 65% of cells initially 10 to 20 microns in diameter, 71% of
cells 20 to 30 microns, and 40% of cells greater than 30 microns.
Conversely, in absence of GM- CSF, 17%, 31%, and 10% of cells in each group
increased in diameter. These data suggest that rGM-CSF promotes murine
megakaryocytopoiesis in vitro and that the response to the factor is
direct. To determine if the factor influences megakaryocytic/thrombocytic
lineage in vivo, 1 and 5 micrograms of rGM-CSF were administered
intraperitoneally every 12 hours for 6 consecutive days. Although a two- to
three-fold increase in peripheral granulocytes was observed, neither
megakaryocytic progenitor cells or platelets changed. Histologic analysis
of bone marrow megakaryocytes showed no increase in size and number. The in
vivo studies demonstrated no effect of GM-CSF on thrombocytopoiesis. The
discrepancies between the in vitro and in vivo effects of GM-CSF require
additional investigations.
Volume 75,
Issue 7,
pp. 1433-1438,
04/01/1990
Copyright © 1990 by The American Society of Hematology
