title: The regulation of hemopoiesis in long-term bone marrow cultures. II. Stimulation and inhibition of stem cell proliferation.
abstract: The isolation of a DNA synthesis inhibitor (NBME fraction IV) and stimulator (RBME fraction III) specific for the hemopoietic stem cell (CFU-s) from freshly isolated normal adult and regenerating murine bone marrow, respectively, has been well documented. We have utilized long-term liquid bone marrow cultures in a further analysis of the role of these factors in the regulation of CFU-s proliferation. Our results show that shortly after feeding, at a time when the cultured CFU-s are actively proliferating, high levels of the hemopoietic stem cell proliferation stimulator fraction III can be isolated from the culture medium. In contrast, the presence of essentially noncycling CFU-s found in cultures fed 8-10 days previously correlates with high levels of the hemopoietic stem cell inhibitor fraction IV. These results suggest that a certain balance between these factors determines CFU-s proliferation in the long-term cultures. In support of this, DNA synthesis in actively cycling CFU-s in the long-term cultures is inhibited for at least 3 days by the addition of excess NBME fraction IV (inhibitor). Furthermore, DNA synthesis in noncycling cultured CFU-s is stimulated for at least 5 days by the addition of RBME fraction III (stimulator).
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells; D002448:Cell Adhesion; D002455:Cell Division; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D003470:Culture Media; D004247:DNA / Q000096:biosynthesis; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D013997:Time Factors
chemical_list: D003470:Culture Media; D004247:DNA