Expression And Regulation Of Prostaglandin E Synthase In Mouse Uterus During Implantation And Decidualization

Prostaglandin E2 (PGE2) is important for blastocyst spacing, implantation and decidualization in the rodent uterus. PGE synthase (PGES) catalyzes the isomerization of PGH2 to PGE2. There are at least three isoforms of PGES, including glutathione-dependent and membrane-associated PGES (mPGES), glutathione-independent and membrane-associated PGES (mPGES-2), and glutathione-dependent cytosolic PGES (cPGES). cPGES, a constitutive enzyme expressed in wide variety of cells and tissues, is predominantly linked with COX-1 to promote immediate PGE2 generation. mPGES, an inducible perinuclear enzyme, is preferentially coupled with the inducible COX-2 to promote delayed PGE2 generation. However, the expression and regulation of PGES in mammalian uterus during early pregnancy are still unknown.The aim of this study was to investigate the differential expression of mPGES and cPGES in mouse uterus during early pregnancy and its regulation under different conditions by in situ hybridization and immunohistochemistry. mPGES expression in the preimplantation mouse embryos was also performed by reverse transcription PCR (RT-PCR).Expression of mPGES mRNA and protein was at a basal level in the luminal epithelium from days 1 to 4 of pregnancy. However, mPGES mRNA and protein were highly expressed in the stroma immediately surrounding the blastocyst, but not in the luminal epithelium on day 5 of pregnancy. mPGES mRNA and protein were not detected in the pseudopregnant uterus from days 1 to 8. Under delayed implantation, mPGES mRNA and protein were also not detected in the uterus. Once delayed implantation was terminated by estrogen treatment and embryo implantation initiated, both mPGES mRNA and protein were induced to express in the stroma immediately surrounding the blastocyst, which was similar to the expression pattern on day 5 of pregnancy. From days 6 to 8 of pregnancy, the signals for mPGES mRNA and protein were strongly detected in the decidualized cells. mPGES mRNA and protein were also highly expressed in the artificially decidualized cells, but not in the control horn. mPGES mRNA was detected in the oocytes and all the stages of preimplantation embryos.There was a strong level of cPGES mRNA signal in the stromal cells at the implantation site on day 5 of pregnancy, while cPGES immunostaining was strongly detected in the luminal epithelium. The signals for both cPGES mRNA and immunostaining were strongly detected inthe decidualized cells from days 6-8 of pregnancy. There was a basal level of cPGES mRNA signal and immunostaining in the uterus under delayed implantation. After delayed implantation was terminated by estrogen treatment and embryo implantation initiated, cPGES mRNA signal was strongly detected in the stroma underlying the luminal epithelium at the implantation site, and cPGES immunostaining was strongly observed in the luminal epithelium surrounding the implanting blastocyst. There was a strong level of both cPGES mRNA signal and immunostaining in the decidualized cells under artificial decidualization, while only a basal level of cPGES mRNA signal and immunostaining was seen in the control.In summary, the specifical expression of both mPGES and cPGES at the implantation site and in the decidual cells suggests that mPGES and cPGES might play an important role during mouse implantation and decidualization.Ph.D. Student: Ni HuaMajor: Animal Histology and EmbryologySupervisor: Professor Yang Zeng-Ming...