PROGESTERONE-DEPENDENT SECRETION OF MACROPHAGE-COLONY-STIMULATING FACTOR BY HUMAN ENDOMETRIAL STROMAL CELLS OF NONPREGNANT UTERUS IN CULTURE

Recent studies have suggested that macrophage colony-stimulating facto r (M-CSF), a hematopoietic glycoprotein essential to the proliferation and differentiation of mononuclear phagocytes and their progenitor ce lls, is also involved in the reproductive process in mice and humans. In this study, we examined, by enzyme-linked immunosorbent assay, the supernatants of stromal cell-enriched fraction (SF) of human nonpregna nt endometrium for the presence of M-CSF during culture with progester one (P) or estrogen. The bioactivity of M-CSF was assessed in a colony -forming assay of murine bone marrow cells. In addition, the M-CSF lev el in the culture supernatant of SF further purified by subculture, of epithelial cell-enriched fraction purified from human endometrium, an d of peripheral blood lymphocytes, including about 10% monocytes, was examined with or without P, because SF is contaminated by epithelial c ells and macrophages, both of which are suggested to secrete M-CSF. Du ring 2-week culture, the level of M-CSF in the supernatants of SF cult ured with P was markedly higher that of control culture and estrogen-t reated culture on any day tested, except for the first 2 days. P had a dose-dependent effect on M-CSF production by SF. Estrogen also enhanc ed M-CSF production by SF, but did not show dose dependency. The SF cu lture supernatants showed a colony-forming activity that was completel y blocked by neutralizing anti-M-CSF antibody. SF subcultured three ti mes, which was confirmed to be of more than 99% purity, secreted M-CSF in a P-dependent manner. M-CSF was also detected in the culture super natants of epithelial cell-enriched fraction and peripheral blood lymp hocytes, but P-dependent M-CSF production was not shown in these cultu res. These results suggest that human endometrial stromal cells themse lves can secrete bioactive M-CSF in a P-dependent manner in vitro, ind icating that the M-CSF reported to be present in human endometrium is secreted in part by stromal cells and may play a role in the regulatio n of endometrial function under P control.