Epithelial cells are the major source of biologically active granulocyte macrophage colony-stimulating factor in human endometrium

Granulocyte macrophage colony-stimulating factor (GM-CSF) hasemerged as an important growth factor for trophoblast and otherplacental cells, leading to improved placental functioning andfetal survival. Recent observations have indicated that GM-CSFis synthesized by epithelial cells in the murine pregnant andnon-pregnant uterus. In this study, the production of GM-CSFby cells derived from human endometrium is assessed using asensitive bioassay and specific neutralization of the cytokinebioactivity with a monoclonal antibody to GM-CSF. Originally,GM-CSF was assayed in the culture supernatants of explant culturesof human endometria. Concentrations of GM-CSF up to 4440 pg/mlwere detected. Subsequently, enriched epithelial cell cultureswere prepared from glands isolated from human endometrium. Thepurity of epithelial cultures was demonstrated by the expressionof cytokeratin, a weak immunoreactivity for vimentin and a lackof immunoreactivity for leukocyte common antigen, CD68, a macrophage-specificprotein and endothelial marker (factor VIH-related antigens).Detected concentrations of GM-CSF were as high as 18 800 pg/ml.Furthermore, pure epithelial cells of a neoplastic endometrialcell line ECC1 secreted GM-CSF, confirming the ability of endometrialepithelial cells to secrete this cytokine. The immunostainingof dated endometria from proliferative and secretory phasesshowed primarily that epithelial cells, and to a lesser extentstromal cells, exhibited immunoreactivity for GM-CSF. A Westernblot analysis, performed to validate the immunohistochemicaldata, confirmed the presence of an immunoreactive gene productfor GM-CSF in human endometrium throughout the menstrual cycle.These findings indicate that human endometrium synthesizes GM-CSFand that epithelial cells are a major contributor to its production.