Differential expression and regulation of cytokine genes in the mouse uterus

The present investigation examined the differential expression of cytokine genes in vivo and in vitro in the mouse uterus and their regulation by ovarian steroid hormones. The expression of interleukin-1 beta (IL-1 beta), IL-1 alpha, IL-6, and tumor necrosis factor-alpha (TNF alpha) genes was examined in the mouse uterus as well as in freshly isolated or cultured epithelial cells by Northern blot and in situ hybridization. In the day 1 pregnant (D1 = vaginal plug) uterus, the levels of IL-1 alpha and IL-1 beta messenger RNAs (mRNAs) were abundant, whereas those of TNF alpha and IL-6 were at the limits of detection. Freshly isolated D1 uterine epithelial cell preparations contained higher levels of IL-1 alpha and IL-1 beta mRNAs than those observed in the D1 whole uterus, whereas TNF alpha and IL-6 mRNA levels were consistently low. In contrast, D1 epithelial cells showed decreased levels of IL-1 beta mRNA after 1 day of culture, whereas the levels of IL-1 alpha and IL-6 mRNAs increased under similar conditions. The levels of IL-1, IL-6, and TNF alpha mRNAs were at the limits of detection in the D4 whole uterus or freshly isolated diestrous epithelial cells. However, IL-1 alpha and IL-6 mRNA levels in diestrous epithelial cells, like those in D1 epithelial cells, increased in culture. In contrast, IL-1 beta and TNF alpha mRNA levels remained low in cultured epithelial cells. In situ hybridization was used to examine the cell type-specific expression of IL-1 alpha or IL-6 mRNA in uterine sections and cultured cells. Although hybridization signals for IL-1 alpha mRNA were detected in uterine epithelial cells on D1 of pregnancy, IL-6 mRNA could not be detected. IL-1 alpha and IL-6 mRNAs could not be detected in freshly isolated diestrous epithelial cells, although a majority of the epithelial cells showed hybridization signals for these mRNAs after 2 or 4 days of culture. The effects of steroid hormones on uterine cytokine gene expression were examined by Northern blot and in situ hybridization. In adult ovariectomized mice, an injection of 17 beta-estradiol (E2), progesterone (P4), or a combination of E2 and P4 had little or no apparent effect on these cytokine mRNA levels. The results establish that uterine epithelial cells on D1 of pregnancy exhibit heightened expression of IL-1 alpha in culture. In contrast, these cells express little or no IL-6 mRNA in vivo, but show heightened expression in culture. These results suggest that an apparent loss of repression of these uterine genes occurs in culture. Furthermore, E2 and/or P4 treatments appear to have little or no effect on uterine cytokine mRNA levels in adult ovariectomized mice.