Progesterone and Interferon Tau Regulation of LIFR and IL6ST in the Peri-implantation Ovine Uterus.

Abstract

Leukemia inhibitory factor (LIF) plays a key role in blastocyst implantation and development and also regulates uterine receptivity and conceptus (embryo and associated extraembryonic membranes) implantation in many species. In sheep, LIF is expressed by uterine epithelia throughout the estrous cycle and early pregnancy, and LIF is hypothesized to act on the trophectoderm of the rapidly expanding blastocyst. In fact, human LIF improves the implantation rate of ovine embryos. However, little information is available on expression of LIF receptor (LIFR) and co-receptor interleukin 6 signal transducer (IL6ST; also known as gp130), which is a signal transducer shared by many cytokines, including IL6 and LIF. These studies determined effects of the estrous cycle, pregnancy, progesterone (P4) and interferon tau (IFNT) on LIFR and IL6ST expression in the ovine uterus. In Study One, ewes (n=5/day/status) were hysterectomized on either Day 10, 12, 14 or 16 of the estrous cycle or Day 10, 12, 14, 16, 18 or 20 of pregnancy. In both cyclic and pregnant ewes, endometrial LIFR mRNA levels increased after Day 10, but the increase was greater in pregnant than cyclic ewes (day x status, P<0.01). IL6ST mRNA levels were higher in pregnant than cyclic ewes (status, P<0.04), and increased 2.8-fold from Days 10 to 20 of pregnancy (linear, P<0.05). LIFR mRNA and protein were localized to the endometrial luminal (LE) and superficial glands (sGE), whereas IL6ST mRNA and protein were localized primarily in uterine glands. Both LIFR and IL6ST were expressed in conceptus trophectoderm. In Study Two, Day 5 cyclic ewes were ovariectomized and fitted with uterine catheters. Ewes (n=5/treatment) received daily injections of either 50 mg P4 or P4 with the anti-progestin ZK 136,317 from Days 5 to 16 and intrauterine injections of either control proteins (CX) or recombinant ovine IFNT from Days 11 to 16. All ewes were hysterectomized on Day 17. Endometrial LIFR mRNA was not affected by P4 (P4+CX vs P4+ZK+CX, P>0.10). However, IFNT infusion increased LIFR mRNA levels by 1.7-fold (P4+CX vs P4+IFN, P<0.04), but not in P4+ZK-treated ewes. IL6ST mRNA was increased 2.6-fold by P4 (P4+CX vs P4+ZK+CX, P<0.03), and IFNT infusion increased (P<0.05) IL6ST mRNA abundance by 1.5- and 2.6-fold, respectively, in P4- as well as P4+ZK-treated ewes. Study Three used a model of accelerated blastocyst development in which bred ewes were treated daily with vehicle as a control or 25 mg P4 beginning on Day 1.5 post-mating. In ewes treated to Day 9, endometrial LIFR mRNA abundance was increased 2-fold by P4 (P<0.03), while IL6ST mRNA was unaffected (P>0.10). In ewes treated to Day 12, LIFR mRNA was increased 1.6-fold by P4 (P<0.05), while IL6ST was not affected (P>0.10). Treatment of ewes with the anti-progestin RU486 from Days 9 to 12 reduced endometrial LIFR mRNA levels by 2.5-fold (P<0.005) and IL6ST mRNA by 2.8-fold (P<0.02) as compared to P4-treated ewes. These results indicate that LIFR and IL6ST are both stimulated by IFNT and regulated by P4 in a complex stage- and cell-specific manner. Coexpression of LIFR and IL6ST was observed only in the upper glands of the endometrium and conceptus trophectoderm. Thus, uterine LIF may have actions on both the uterine glands and trophectoderm in order to mediate endometrial receptivity and conceptus growth and development in sheep. (Supported by NIH Grant 5 R01 HD32534)