[Show abstract][Hide abstract] ABSTRACT: Although Cyclooxygenase-2 (COX-2) is essential for mouse ovulation, fertilization, implantation and decidualization, the regulation and function of COX-2 in rat reproduction are still unknown. This study was designed to examine the action of COX-2 in rat ovulation, implantation and decidualization by using two specific inhibitors of COX-2 (nimesulide and niflumic acid). Compared to control, either nimesulide or niflumic acid significantly inhibited the ovulation in the superovulated rats. Although nimesulide had no obvious effects on the number of implantation sites and the vascular permeability, the expression of PPARdelta, HB-EGF and vimentin proteins was down-regulated in the nimesulide-treated groups. COX-1 protein was upregulated by nimesulide treatment. Nimesulide also had an inhibitory effect on decidualization during early pregnancy and under artificial decidualization. Moreover, nimesulide caused the increase of the gestation period and the reduction of litter size and birth weight compared to controls. Based on our data, rat implantation and decidualization were delayed by nimesulide treatment, resulting in the reduction of litter size and birth weight and the prolongation of gestational length, suggesting that COX-2 plays an important role in implantation and decidualization.
Full-text · Article · Feb 2007 · Frontiers in Bioscience
[Show abstract][Hide abstract] ABSTRACT: It has been shown that both prostaglandin I2 (PGI2) and PGE2 are essential for mouse implantation, whereas only PGE2 is required for hamster implantation. To date, the expression and regulation of cyclooxygenase (COX) and prostaglandin E synthase (PGES), which are responsible for PGE2 production, have not been reported in the rat. The aim of this study was to examine the expression pattern and regulation of COX-1, COX-2, membrane-associated PGES-1 (mPGES-1), mPGES-2 and cytosolic PGES (cPGES) in rat uterus during early pregnancy and pseudopregnancy, and under delayed implantation. At implantation site on day 6 of pregnancy, COX-1 immunostaining was highly visible in the luminal epithelium, and COX-2 immunostaining was clearly observed in the subluminal stroma. Both mPGES-1 mRNA and protein were only observed in the subluminal stroma surrounding the implanting blastocyst at the implantation site on day 6 of pregancy , but were not seen in the inter-implantation site on day 6 of pregnancy and on day 6 of pseudopregnancy. Our data suggest that the presence of an active blastocyst is required for mPGES-1 expression at the implantation site. When pregnant rats on day 5 were treated with nimesulide for 24 h, mPGES-1 protein expression was completely inhibited. cPGES immunostaining was clearly observed in the luminal epithelium and subluminal stromal cells immediately surrounding the implanting blastocyst on day 6 of pregnancy. mPGES-2 immunostaining was clearly seen in the luminal epithelium at the implantation site. Additionally, immunostaining for prostaglandin I synthase (PGIS) was also strongly detected at the implantation site. In conclusion, our results indicate that PGE2 and PGI2 should have a very important role in rat implantation.
Preview · Article · Feb 2006 · Reproduction (Cambridge, England)
[Show abstract][Hide abstract] ABSTRACT: Signal transducer and activator of transcription 3 (Stat3), a member of the Stat family, is specifically activated during mouse embryo implantation. The aim of this study was to investigate the expression, activation and regulation of Stat3 in rat uterus during early pregnancy, pseudopregnancy, delayed implantation and artificial decidualization. Stat3 mRNA was highly expressed in the luminal epithelium on day 5 and in the luminal epithelium and underlying stromal cells at implantation sites on day 6 of pregnancy. There was a strong level of Stat3 protein expression and phosphorylation in the stromal cells near the lumen and in the luminal epithelium on day 5 of pregnancy, which was similar to day 5 of pseudopregnancy. In the afternoon of day 6, the strong level of Stat3 phosphorylation was detected only in the luminal epithelium. Stat3 was highly expressed and activated in the decidual cells from days 7 to 9 of pregnancy and under artificial decidualization in the present study. Our results suggest that the strong level of Stat3 activation in the luminal epithelium and underlying stromal cells during the pre-implantation period may be important for establishing uterine receptivity as in mice, and the high level of Stat3 expression and activation in decidual cells may play a role during decidualization.