UTERINE EPITHELIAL-CELL SECRETION OF INTERLEUKIN-1-ALPHA INDUCES PROSTAGLANDIN-E2 (PGE2) AND PGF2-ALPHA SECRETION BY UTERINE STROMAL CELLS-INVITRO

Uterine epithelial cells (UEC) were isolated from cycling mice and cultured on Matrigel-coated nitrocellulose filters to determine their ability to secrete interleukin-1alpha (IL-1alpha) in response to ovarian steroids and induce prostaglandin (PG) secretion by uterine stromal cells (USC). UEC cultured in a polarized manner secreted IL-1alpha with an 8-to 10-fold apical vs. basal preference, as determined by an enzyme-linked immunosorbent assay. There was no effect of 17beta-estradiol, progesterone, or 17beta-estradiol plus progesterone on IL-1alpha secretion by UEC. The mean total IL-1alpha secreted to the apical and basal secretory compartments over the 24-h incubation period was 0.8 +/- 0.16 and 0.07 +/- 0.05 ng/2 x 10(5) cells, respectively. Cytokine bioactivity, as determined by [H-3]thymidine incorporation into D10 cells in response to UEC-conditioned medium, paralleled the pattern of IL-1alpha secretion observed using the immunoassay. In addition to the in vitro secretion of IL-la by polarized UEC, pooled uterine fluid collected from proestrous stage mice contained IL-1alpha at a concentration of 0.7 ng/ml, indicating that IL-1alpha is released into the uterine lumen in vivo. Coculture with UEC or treatment with conditioned medium from either the apical or basal UEC secretory compartments induced a several-fold increase in the secretion of PGE2 and PGF2alpha by USC. Relative to untreated USC, PGE2 was induced to a greater extent than PGF2alpha. The addition of polyclonal anti-IL-1alpha significantly inhibited the ability of UEC-conditioned medium and UEC coculture to induce PG secretion to on by USC. In addition, mouse recombinant IL-1alpha added at a concentration similar to that secreted by UEC stimulated USC PGE2 and PGF2alpha secretion in a manner similar to that observed with UEC coculture. Experiments designed to determine the cell type specificity of the induction of PG secretion by USC indicated that conditioned medium from a human UEC line (RL95), a rat prostate epithelial cell line (E4), and a mouse fibroblast cell line (10T1/2) induced PG secretion to an extent that paralleled their ability to induce D10 cell proliferation. The present results demonstrate the ability of UEC to secrete IL-1alpha in a vectorial manner. Soluble products secreted by UEC are capable of stimulating PGE2 and PGF2alpha secretion by USC, and IL-1alpha appears to be a significant factor contributing to this effect. The secretion of IL-1alpha by UEC may function in an autocrine or paracrine manner to regulate aspects of uterine function during implantation, including the decidual cell response.