Regulation of endometrial granulocyte macrophage-colony stimulating factor (GM-CSF) in the ewe

Abstract

Granulocyte macrophage-colony stimulating factor (GM-CSF) increases ovine interferon-tau (oIFNτ) secretion by ovine conceptuses, but endometrial production of GM-CSF has not been characterized. Endometrial GM-CSF expression was evaluated in ovariectomized ewes implanted with estradiol-17β (E 2) and/or progesterone (P 4) for 14 days, in day 14 cyclic and day 14 pregnant ewes. Relative levels of endometrial GM-CSF mRNA were 3-fold higher in E 2- and E 2/P 4-treated ewes than that of control or P 4-treated ovariectomized ewes. Levels of endometrial GM-CSF mRNA for cyclic ewes were similar to E 2- and E 2/P 4-treated ewes, but amounts of GM-CSF mRNA in pregnant ewes were 2-fold higher. GM-CSF concentrations in endometrial culture media, determined by GM-CSF bioassay, for cyclic and E 2/P 4-treated ovariectomized ewes were 3-fold higher than those of control, E 2- and P 4-treated ovariectomized ewes; however, amounts of GM-CSF in pregnant ewes were 2-fold higher. Immunoreactive GM-CSF, examined by western blot, was detected in the culture medium from E 2/P 4-treated ovariectomized, cyclic and pregnant ewes. Luminal and glandular epithelia and stromal regions were determined to be sites of GM-CSF expression by immunohistochemistry and in situ hybridization techniques. Data indicate that combined E 2 and P 4 treatment of ovariectomized ewes is sufficient to restore GM-CSF expression to the level found in cyclic ewes; however, GM-CSF mRNA and protein in pregnant ewes is 2-fold greater than in ovariectomized or cyclic ewes. These data suggest that the conceptus, in addition to steroids, may play a role in the regulation of endometrial production of GM-CSF.