Effects of recombinant thrombopoietin on the growth of murine primitive and committed hematopoietic progenitors in serum-free culture.
BACKGROUND
The aim of the present study was to determine the effect of thrombopoietin (Tpo) in combination with other cytokines on the growth of murine megakaryocytic, granulocyte-macrophage, erythroid and primitive hematopoietic progenitor cells, excluding possibilities of synergistic effects by serum factor(s).


METHODS
Serum-free clonogenic assay systems were used for assay of colony forming units in megakaryocytes (CFU-Mk), colony forming units in granulocytes-macrophages (CFU-GM), burst-forming units in erythrocytes (BFU-E) in marrow of normal mice and of high proliferative potential colony forming cells in 5-fluorouracil-treated marrow.


RESULTS
Serum-free culture enabled megakaryocyte colony growth by recombinant murine (rm) Tpo and this was synergistically supported with rm interleukin (IL)-3, rm stem cell factor (SCF) or recombinant human (rh) erythropoietin (Epo). Recombinant human IL-6, rhIL-11 and rm granulocyte-macrophage colony stimulating factor (GM-CSF) showed synergistic effects with rmTpo only in the presence of serum. Recombinant murine IL-3 or rmSCF increased the large colonies and mixed-type colonies containing other populations, suggesting that these cytokines promoted the proliferation of immature populations of CFU-Mk. The rmTpo enhanced the growth of granulocyte-macrophage (GM) colonies stimulated by rmGM-CSF or rmIL-3 and erythroid bursts by rhEpo, with or without rmIL-3. The rmTpo also significantly increased HPP colonies in synergy with rmIL-3 only in the presence of serum or rmSCF.


CONCLUSIONS
Serum-free culture is valuable for evaluating synergistic effects of cytokines and Tpo acts not only on megakaryocytic progenitors but also on granulocyte-macrophage, erythroid and primitive progenitor cells in combination with other cytokines, such as rmIL-3 and rmSCF. However, serum or SCF was required for enhancement of the colony growth of primitive progenitors by Tpo.
Sasaki
H
H
Department of Pediatrics, Yokohama City University School of Medicine, Japan.
Ikuta
K
K
Funabiki
T
T
Fujioka
K
K
Matsuda
M
M
D000818:Animals; D001773:Blood Cells / Q000166:cytology / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D016895:Culture Media, Serum-Free; D016207:Cytokines / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects*; D008297:Male; D008533:Megakaryocytes / Q000166:cytology / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D011994:Recombinant Proteins / Q000494:pharmacology*; D013926:Thrombopoietin / Q000494:pharmacology*
D016895:Culture Media, Serum-Free; D016207:Cytokines; D011994:Recombinant Proteins; D013926:Thrombopoietin