Regulation of prostacyclin synthase expression and prostacyclin content in the pig endometrium.

Prostaglandins (PGs) are critical regulators of a number of reproductive processes, including embryo development and implantation. In the present study, prostacyclin (PGI(2)) synthase (PGIS) mRNA and protein expression, as well as 6-keto PGF(1α) (a PGI(2) metabolite) concentration, were investigated in the pig uterus. Endometrial tissue and uterine luminal flushings were obtained on Days 4 to 18 of the estrous cycle and pregnancy. Additionally, conceptuses were collected and examined for PGIS mRNA expression and 6-keto PGF(1α) concentration. Regulation of PGI(2) synthesis in the porcine endometrium by steroids, conceptus products, and cytokines was studied in vitro and/or in vivo. Endometrial PGIS protein level increased on Days 12 and 16 in pregnant but not in cyclic gilts. Moreover, higher PGIS protein expression on Day 12 of pregnancy was accompanied by a greater content of 6-keto PGF(1α) in the endometrium. The concentration of 6-keto PGF(1α) in uterine luminal flushings increased substantially on Days 16 and 18 in pregnant gilts and was higher than in cyclic animals. Greater PGIS mRNA expression and PGI(2) metabolite concentration were detected in Day 12 and 14 conceptuses, respectively. Incubation of endometrial explants with conceptus-conditioned medium resulted in upregulation of PGIS protein expression and increased PGI(2) secretion. Moreover, PGIS mRNA and protein expression were upregulated in the endometrium collected from gravid uterine horn on Day 14 of pregnancy. In summary, PGIS is differentially expressed in the endometrium of cyclic and pregnant gilts resulting in higher PGI(2) synthesis in pregnant animals. Porcine conceptuses are important regulators of endometrial PGIS expression and PGI(2) release during the implantation period.

Regulation of expression and role of leukemia inhibitory factor and interleukin-6 in the uterus of early pregnant pigs.

Cytokines, which are generally involved in the process of inflammation, may also play a critical role in conceptus implantation. We examined: (1) the expression profiles of leukemia inhibitory factor (LIF) and interleukin (IL)-6 mRNA and their protein content in the endometrium of cyclic and pregnant gilts on Days 10 to 18 after estrus; (2) the effect of conceptus-exposed medium on LIF and IL-6 synthesis in the endometrium; (3) the profiles of IL6R and LIFR mRNA expression in pig conceptuses collected on Days 10 to 18 of pregnancy; and (4) the effect of LIF and IL-6 on the attachment and proliferation of porcine trophoblast cells. The expression of LIF mRNA in the endometrium increased between Days 10 and 12 in both cyclic and pregnant gilts, and tended to be higher in Day 12 pregnant animals compared with nonpregnant ones. The LIF protein content in the uterine lumen peaked on Day 12 of pregnancy, and was higher than on Day 12 of the estrous cycle. Endometrial IL-6 mRNA expression was upregulated on Day 12 in pregnant gilts compared with nonpregnant animals. Moreover, a higher content of IL-6 protein was observed in pregnant than in cyclic gilts. The addition of conceptus-exposed medium resulted in up-regulation of LIF and IL6 mRNA expression, and increased IL-6 content in endometrial slices. In conceptuses, increased mRNA expression was detected on Days 10 to 14 for IL6R and on Day 14 for LIFR, when compared with other days studied. LIF and IL-6 stimulated the attachment and proliferation of trophoblast cells in vitro. In summary, LIF and IL-6 are important components of embryo-uterine interactions during early pregnancy in the pig, and may contribute to successful conceptus implantation.

Effect of conceptus secretions on HOXA10 and PTGS2 gene expression, and PGE2 release in co-cultured luminal epithelial and stromal cells of the porcine endometrium at the time of early implantation.

Homeobox A10 (HOXA10) gene expression was demonstrated in the endometrium of adult porcine uteri, however there is little information concerning the role of this gene in the pig. Objectives of the present study were to examine: 1) the expression of HOXA10 in the endometrium of cyclic and early pregnant gilts; 2) the effect of estradiol (E(2)) and progesterone (P(4)) on HOXA10 expression in porcine luminal epithelial (LE) and stromal (ST) cells in vitro; 3) the effect of E(2) and conceptus-exposed medium (CEM) on HOXA10 and prostaglandin endoperoxide synthase (PTGS2) gene expression and prostaglandin (PG) E(2) secretion from LE and ST cells in a co-culture model. The abundance of HOXA10 mRNA was increased on day 15 of pregnancy in comparison to day 15 of the estrous cycle. Moreover, increased HOXA10 mRNA level was detected in ST cells after E(2) and P(4) treatment. E(2) stimulated the expression of HOXA10 in LE cells cultured on collagen and pre-treated with steroids, but not in LE on plastic surfaces. Addition of CEM to LE cells cultured in collagen-coated inserts of the co-culture system resulted in elevated HOXA10 and PTGS2 gene expression and PGE(2) secretion in these cells, but not in ST cells cultured in basal compartments. ST cells directly treated with E(2) or CEM showed higher levels of HOXA10 and PTGS2 expression. Blocking of estrogen receptors with ICI-182,780 did not influence the stimulatory effect of CEM. We conclude that HOXA10 expression in the porcine endometrium is closely related to the implantation process and stimulated by conceptus products. Moreover, the co-culture system of LE and ST cells is a promising model for the study of endometrial response to conceptus-derived factors.