Effects of the estrous cycle, pregnancy and interferon tau on expression of cyclooxygenase two (COX-2) in ovine endometrium

Whole-genome resequencing of Hu sheep identifies candidate genes associated with agronomic traits

The phenotypic diversity resulting from artificial or natural selection of sheep has made a significant contribution to human civilization. Hu sheep are a local sheep breed unique to China with high reproductive rates and rapid growth. Genomic selection signatures have been widely used to investigate the genetic mechanisms underlying phenotypic variation in livestock. Here, we conduct whole-genome sequencing of 207 Hu sheep and compare them with the wild ancestors of domestic sheep (Asiatic mouflon) to investigate the genetic characteristics and selection signatures of Hu sheep. Based on six signatures of selection approaches, we detect genomic regions containing genes related to reproduction (BMPR1B, BMP2, PGFS, CYP19, CAMK4, GGT5, and GNAQ), vision (ALDH1A2, SAG, and PDE6B), nervous system (NAV1), and immune response (GPR35, SH2B2, PIK3R3, and HRAS). Association analysis with a population of 1299 Hu sheep reveal those missense mutations in the GPR35 (GPR35 g.952651 A>G; GPR35 g.952496 C>T) and NAV1 (NAV1 g.84216190 C>T; NAV1 g.84227412 G>A) genes are significantly associated (P < 0.05) with immune and growth traits in Hu sheep, respectively. This research offers unique insights into the selection characteristics of Hu sheep and facilitates further genetic improvement and molecular investigations.

Effect of early administration of progesterone on the function of the corpus luteum of llamas

The aim of the present study was to evaluate if early administration of progesterone immediately after ovulation affects corpus luteum lifespan in llamas. Female llamas (n = 16) were induced to ovulate by Buserelin injection in the presence of an ovulatory follicle (Day 0). On Day 2, ovulation was confirmed and animals were randomly divided into two groups: treated animals (n = 8) received an intravaginal device containing 0.3 g of progesterone from Day 2 to Day 6 post-induction of ovulation and control group (n = 8) received a device with 0 g of progesterone. Blood samples were collected daily to determine plasma progesterone concentration and transrectal ultrasonographies were performed from Day 7 to Day 12 post-induction of ovulation. Mean maximum diameter of the corpus luteum was significantly lower and was reached before in the treated group than in the control group. The mean highest plasma progesterone concentration and the day that concentration was achieved were similar between groups. However, mean plasma progesterone concentration was significantly higher in the treated group than in the control group on Days 3 and 4 and lower on Days 8 and 9 post-induction of ovulation. The day that plasma progesterone concentration returns to 1 ng/ml differed between groups, occurring earlier in the treated group. In conclusion, the early increase of plasma progesterone concentration during the luteal phase, promoted the premature activation of the luteolytic process affecting corpus luteum function in llamas as it was previously reported in other species.

How Is Arachidonic Acid Metabolism in the Uterus Connected with the Immune Status of Red Deer Females (Cervus elaphus L.) in Different Reproductive Stages?

Reproductive and condition parameters' dependency on immune status in seasonally reproducing ruminants such as red deer have not been outlined to date. We determined T and B blood lymphocytes; the concentration of IgG, cAMP, haptoglobulin, and 6-keto-PGF1α in blood plasma; and the mRNA and protein expression of PG endoperoxide synthase 2, 5-lipoxygenase, PGE2 synthase (PGES), PGF2α synthase (PGFS), PGI2 synthase (PGIS), leukotriene (LT)A4 hydrolase, and LTC4 synthase (LTC4S) in the uterine endo- and myometrium, on the 4th (N = 7) and 13th (N = 8) days of the estrous cycle, in anestrus (N = 6) and pregnancy (N = 8) in hinds. An increase in CD4+ T regulatory lymphocyte percentage during the estrous cycle and anestrus compared with pregnancy was recorded; the opposite effect was observed for CD21+ B cells (p < 0.05). cAMP and haptoglobin concentration were elevated during the cycle, as was IgG on the fourth day of the cycle, whereas 6-keto-PGF1α concentration was the highest in pregnancy, and the nearest in anestrus similarly were LTC4S, PGES, PGFS, and PGIS protein expression in the endometrium (p < 0.05). We showed an interaction between the immune system activation and AA-metabolite production in the uterus throughout different reproductive stages. IgG, cAMP, haptoglobin, and 6-keto-PGF1α concentrations are valuable candidates for markers of reproductive status in hinds. The results help expand our knowledge of the mechanisms underlying seasonal reproduction in ruminants.

Changes in expression of prostaglandin synthase in ovine liver during early pregnancy

Liver can function as part of the innate and adaptive immune systems. We hypothesize that prostaglandins participate in the regulation of hepatic immune function during early pregnancy in sheep. The objective of this study was to elucidate expression of prostaglandin synthase in ovine liver during early pregnancy. Ovine livers were sampled on day 16 of the estrous cycle, and days 13, 16, and 25 of pregnancy, and the expression of prostaglandin synthases, including prostaglandin-endoperoxide synthase 1 (PTGS1), PTGS2, prostaglandin E synthase (PTGES), and aldo-keto reductase family 1, member B1, a prostaglandin F synthase (PGFS), were detected by quantitative real-time polymerase chain reaction, Western blot, and immunohistochemistry analysis. There were increases in the expression of mRNA and the proteins of PTGS2, PTGES, and PGFS in the livers during early pregnancy, but PTGS1 was decreased in the pregnant ewes. The PGFS protein was limited to the hepatocytes and the endothelial cells of the proper hepatic arteries and hepatic portal veins. In summary, the upregulation of PTGS2, PTGES, and PGFS and downregulation of PTGS1 may be involved in the maternal hepatic immune adjustment during early pregnancy in sheep.

The potentialities of oxytocin receptor inhibitors for endometriosis therapy

OBJECTIVE

Genital endometriosis (GE) is a widespread gynecological disease which requires its further pathogenesis investigation and search for new effective treatments. The known data of oxytocin receptor presence in endometrioid heterotopy smooth muscle cells give some grounds to assume oxytocin participation in the pathogenesis of endometriosis. The present study objective was to evaluate oxytocin level in peripheral blood (PB) in patients with endometriosis associated pain syndrome and to estimate the efficacy of oxytocin receptor inhibitors (IOXTR) administration based on animal endometriosis model.

MATERIALS AND METHODS

The basic group comprised 61 patients with endometriosis associated pain syndrome, while 21 patients formed the control group. VAS, MPQ, and BBS objective tests were applied for pain syndrome evaluation. Oxytocin level in PB was measured by immunoenzyme method. After confirmation of endometriosis experimental model formation in rats and further randomization, a daily IOXTR intra-abdominal injection was performed in a dose of 0.35 mg/kg/24 h in the basic group (n = 12) or saline solution administration in the control (n = 12). On the final stage, endometrioid heterotopy size measuring was performed along with histological examination.

RESULTS

Oxytocin level in PB was authentically higher in patients with GE compared to the control: 51.45 (35.54-62.76) pg/mL and 27.64 (23.23-34.12) pg/mL, respectively (p<.001). Positive correlation between oxytocin PB level and pain syndrome expression was established in patients with GE: VAS (r = 0.76; p<.001), MPQ (r = 0.52; p<.001), and BBS (r = 0.57; p<.001). Based on the experimental disease model authentical decrease of endometrioid heterotopy average area was observed after IOXTR therapy compared to the control (7.3 ± 1.8 mm² and 22.2 ± 1.2 mm², respectively, p<.05).

CONCLUSIONS

The obtained results confirm the oxytocin role in the pathogenesis of endometrioid associated pain syndrome. The high efficacy of IOXTR administration based on animal model of surgically induced endometriosis allows viewing this method as a perspective therapy.

Effect of early pregnancy on the expression of prostaglandin synthases in the ovine thymus

Thymus is a primary lymphoid organ, must adapt to the presence of fetal alloantigens. Prostaglandins (PGs) have diverse effects to activate or inhibit the immune response, but effects of early pregnancy on the expression of PG synthases in ovine maternal thymus are unclear. In this study, ovine thymic samples were obtained at day 16 of the estrous cycle, and days 13, 16 and 25 of pregnancy. The expression of PG synthases, including cyclooxygenase 1 (COX-1), COX-2, PGE2 synthase (PTGES), and a prostaglandin F2α synthase (Aldo-keto reductase family 1, member B1, AKR1B1), was evaluated using quantitative real-time PCR, Western blot and immunohistochemistry analysis. In addition, the thymus/body ratio was also calculated. Our results showed that the expression of COX-2 mRNA and protein, AKR1B1 mRNA and dimer were up-regulated on day 25 of pregnancy (P < 0.05), and expression of COX-1, PTGES mRNA and protein, AKR1B1 monomer and thymus/body ratio were similar at different stages of pregnancy and the estrous cycle. The immunohistochemistry results showed that the COX-2 and AKR1B1 proteins were located in the stromal cells, capillaries and thymic corpuscles. This is the first study to report that expression of COX-2 and AKR1B1 dimer is up-regulated in the maternal thymus during early pregnancy, suggesting that early pregnancy exerts its effects on maternal thymus, which is involved in immunomodulation during early pregnancy in sheep.

Exacerbated conceptus signaling does not favor establishment of pregnancy in beef cattle

Background

Insufficient production of anti-luteolytic signals by the pre-attachment embryo is considered a major cause of pregnancy failure in cattle. We tested the hypothesis that transfer of multiple blastocysts (n = 5/recipient) and progesterone (P4) supplementation amplify anti-luteolytic signaling and reduce embryonic losses in beef cattle. Cows detected in estrus (D0; n = 104) were assigned randomly to receive 150 mg of injectable long-acting P4 (iP4) or vehicle (non-iP4) on D4 and transcervical transfer of none or five, grade 1, not-frozen, in vitro-produced blastocysts, on D7. Luteal development and time of structural luteolysis were monitored by ultrasonography. Plasma P4 concentrations were determined on D4, D5 and D7, and daily between D14 and D20. Conceptus signaling was monitored by transcript abundance of interferon-stimulated gene 15 (ISG15) in peripheral blood mononuclear cells isolated on D14, D16, D18 and D20. Early embryonic mortality (EEM) was defined as the absence of ISG15 mRNA upregulation over time and/or luteal regression up to D20. Late embryonic mortality (LEM) was defined as the absence of a conceptus with a heartbeat on pregnancy diagnosis at D30 (PD30) after observing upregulation of ISG15 mRNA and extension of luteal lifespan. Pregnant cows presented conceptuses with heartbeat at PD30.

Results

On D5, iP4-treated cows had P4 concentrations 2.07-fold greater than non-iP4 treated (P < 0.001). On D7, P4 concentrations were similar. Pregnant and LEM animals showed a progressive increase in the abundance of ISG15 from D14 to D20. iP4-treated cows detected pregnant at PD30 had 1.53-fold greater abundance of ISG15 mRNA between D14 and D20 than non-iP4 treated cows (P = 0.05). iP4 doubled the frequency of EEM while it did not affect LEM. At PD30, embryonic survival was 37.0% vs. 55.6% for iP4-treated vs. control cows. Majority of pregnant cows (71%) presented only a single viable embryo.

Conclusions

A substantial proportion of cows had EEM (31%) and LEM (20%) even after transferring multiple blastocysts. This argues that mortality was due to poor uterine receptivity that could not be reversed by supplemental P4 or overcome by transferring multiple blastocysts. Further, a given uterine environment was not necessarily adequate to all embryos.

Effect of exogenous progesterone on embryo size and ewe uterine gene expression in an ovine 'dam size' model of maternal constraint

Progesterone (P4), acting via its receptor, regulates uterine function and histotroph production, which are crucial to embryo growth. This study aimed to examine exogenous P4 effects on embryo size and differential endometrial gene expression at Day 19 of gestation using a 'dam size' sheep model of maternal constraint. Purebred Suffolk (S, genotypically large) embryos were transferred into recipient groups of Cheviot (C, genotypically small) or Suffolk ewes that had, or had not, been pre-treated with P4 from Days 0 to 6 of pregnancy. At Day 19S embryos were collected from four experimental groups: P4 pretreated S ewes (SP4; n=5), untreated S ewes (SnP4; n=15), P4 pretreated C ewes (CP4; n=7) and untreated C ewes (CnP4; n=21). Day-19 embryos from CP4 ewes were larger (P<0.05) than those from CnP4 ewes and similar in size (P>0.05) to embryos from SnP4 and SP4 ewes. Expression of mucin 1 (MUC1) and prostaglandin-endoperoxide synthase 2 (PTGS2) was upregulated in uterine horns ipsilateral to the corpus luteum from CP4 ewes. Prostaglandin receptor (PGR), MUC1 and PTGS2 expression was upregulated, whilst cathepsin L (CTSL) and radical S-adenosyl methionine domain-containing 2 (RSAD2) expression was downregulated in the ipsilateral horn of SP4 ewes. This suggests that pretreating ewes with exogenous P4 may alleviate early pregnancy maternal constraint via mechanisms that alter uterine function. However, further research is required to investigate the timing of P4 administration and its impact on conception rates.

Paracrine and endocrine actions of interferon tau (IFNT)

This review focuses on the paracrine and endocrine actions of interferon tau (IFNT) during pregnancy recognition and establishment in ruminants. Pregnancy recognition involves the suppression of the endometrial luteolytic mechanism by the conceptus to maintain progesterone production by the corpus luteum (CL). The paracrine antiluteolytic effects of conceptus-derived IFNT inhibit upregulation of oxytocin receptors in the endometrial epithelia of the uterus, thereby preventing the production of luteolytic prostaglandin F2 alpha (PGF2α) pulses. In the endometrium, IFNT induces or upregulates a large number of classical IFN-stimulated genes (ISGs) and regulates expression of many other genes in a cell-specific manner that are likely important for conceptus elongation, implantation and establishment of pregnancy. Further, IFNT has endocrine effects on extrauterine cells and tissues. In sheep, IFNT induces luteal resistance to PGF2α, thereby ensuring survival of the CL for maintenance of pregnancy. The ISGs induced in circulating peripheral blood mononuclear cells by IFNT may also be useful as an indicator of pregnancy status in cattle. An increased knowledge of IFNT and ISGs is important to improve the reproductive efficiency in ruminants.

The abnormal expression of oxytocin receptors in the uterine junctional zone in women with endometriosis

BACKGROUND

The junctional zone (JZ), also called as the endometrial-myometrial junction, is related to peristaltic-like movements in the non-pregnant uterus. Hyperperistalsis and dysperistalsis of uterus constructions might underlie many important disorders such as dysmenorrhea, infertility, endometriosis, implantation failure. The major proteins for uterine contraction of the non-pregnant uterus may be Oxytocin (OT) and oxytocin receptor (OTR). The objective of this study was to inspect the expression of OTR in isthmic and mid-fundal parts of the uterine junctional zone at different stages of the follicular cycle in patients with and without endometriosis.

METHODS

Uterine biopsies containing endometrium and junctional zone were collected from the isthmic and mid-fundal parts of the anterior wall after hysterectomy. The OTR expression was evaluated by immunohistochemistry.

RESULTS

In the control uterus, OTR expression in the isthmic region was significantly higher than in the fundal region in the proliferative phase (p < 0.05) but significantly lower in the secretory phase (p < 0.05). And the expression of OTR in the proliferative phase was significantly higher than that in the secretory phase in both isthmic and fundal regions (p = 0.000 and 0.049, respectively). However, in endometriosis uteri, OTR expression in the isthmic region showed no significant difference with that in the fundal region in both proliferative and secretory phases (p = 0.597 and 0.736, respectively). In both isthmic and fundal regions, OTR expression was not significantly different between the proliferative phase and secretory phase (p = 0.084 and 0.222, respectively). OTR expression in fundal regions of revised ASRM I and II endometriosis were lower than that of revised ASRM III and IV (p = 0.049). In the fundal region of JZ, the expression of OTR in ovarian endometriosis was significantly lower than that in deep infiltrating endometriosis (p = 0.046). The expression level of OTR in the funds region is positively associated with the severity of dysmenorrhea in endometriosis group (r = 0.870, p < 0.05). Comparing to normal uteri, the expression of OTR in the secretory phase was significantly higher in the endometriosis uteri (p < 0.05). In the fundus of endometriosis uteri, OTR expression was significantly higher in both the proliferative and secretory phases (p = 0.045 and 0.028, respectively).

CONCLUSION

OTR expression in the JZ of women with endometriosis changes significantly, which may result in abnormal uterine contractile activity, reducing the endometriosis-related fertility and dysmenorrhea.

Environmental factors affecting pregnancy: endocrine disrupters, nutrients and metabolic pathways

Uterine adenogenesis, a unique post-natal event in mammals, is vulnerable to endocrine disruption by estrogens and progestins resulting in infertility or reduced prolificacy. The absence of uterine glands results in insufficient transport of nutrients into the uterine lumen to support conceptus development. Arginine, a component of histotroph, is substrate for production of nitric oxide, polyamines and agmatine and, with secreted phosphoprotein 1, it affects cytoskeletal organization of trophectoderm. Arginine is critical for development of the conceptus, pregnancy recognition signaling, implantation and placentation. Conceptuses of ungulates and cetaceans convert glucose to fructose which is metabolized via multiple pathways to support growth and development. However, high fructose corn syrup in soft drinks and foods may increase risks for metabolic disorders and increase insulin resistance in adults. Understanding endocrine disrupters and dietary substances, and novel pathways for nutrient metabolism during pregnancy can improve survival and growth, and prevent chronic metabolic diseases in offspring.

Conceptus elongation in ruminants: roles of progesterone, prostaglandin, interferon tau and cortisol

The majority of pregnancy loss in ruminants occurs during the first three weeks after conception, particularly during the period of conceptus elongation that occurs prior to pregnancy recognition and implantation. This review integrates established and new information on the biological role of ovarian progesterone (P4), prostaglandins (PGs), interferon tau (IFNT) and cortisol in endometrial function and conceptus elongation. Progesterone is secreted by the ovarian corpus luteum (CL) and is the unequivocal hormone of pregnancy. Prostaglandins (PGs) and cortisol are produced by both the epithelial cells of the endometrium and the trophectoderm of the elongating conceptus. In contrast, IFNT is produced solely by the conceptus trophectoderm and is the maternal recognition of pregnancy signal that inhibits production of luteolytic pulses of PGF_2α by the endometrium to maintain the CL and thus production of P4. Available results in sheep support the idea that the individual, interactive, and coordinated actions of P4, PGs, IFNT and cortisol regulate conceptus elongation and implantation by controlling expression of genes in the endometrium and/or trophectoderm. An increased knowledge of conceptus-endometrial interactions during early pregnancy in ruminants is necessary to understand and elucidate the causes of infertility and recurrent early pregnancy loss and provide new strategies to improve fertility and thus reproductive efficiency.

Hosting the preimplantation embryo: potentials and limitations of different approaches for analysing embryo - endometrium interactions in cattle

Ongoing detailed investigations into embryo–maternal communication before implantation reveal that during early embryonic development a plethora of events are taking place. During the sexual cycle, remodelling and differentiation processes in the endometrium are controlled by ovarian hormones, mainly progesterone, to provide a suitable environment for establishment of pregnancy. In addition, embryonic signalling molecules initiate further sequences of events; of these molecules, prostaglandins are discussed herein as specifically important. Inadequate receptivity may impede preimplantation development and implantation, leading to embryonic losses. Because there are multiple factors affecting fertility, receptivity is difficult to comprehend. This review addresses different models and methods that are currently used and discusses their respective potentials and limitations in distinguishing key messages out of molecular twitter. Transcriptome, proteome and metabolome analyses generate comprehensive information and provide starting points for hypotheses, which need to be substantiated using further confirmatory methods. Appropriate in vivo and in vitro models are needed to disentangle the effects of participating factors in the embryo–maternal dialogue and to help distinguish associations from causalities. One interesting model is the study of somatic cell nuclear transfer embryos in normal recipient heifers. A multidisciplinary approach is needed to properly assess the importance of the uterine milieu for embryonic development and to use the large number of new findings to solve long-standing issues regarding fertility.

mRNA transcription of prostaglandin synthases and their products in the equine endometrium in the course of fibrosis

Accurate regulation of the reproductive cycle and successful implantation depend on proper functioning of the endometrium. The aim of this study was to determine whether mRNA transcription of specific enzymes responsible for prostaglandin (PG) synthesis (prostaglandin-endoperoxide synthase, PTGS-2; prostaglandin F(2α) synthase, PGFS; and prostaglandin E(2) synthases, PGES) and PG concentrations in endometrial extracts would change in moderate (Kenney's Category II) and severe phases of fibrosis (Kenney's Category III; endometrosis), compared with healthy endometrium (Kenney's Category I), during the estrous cycle. Endometrial tissues samples were obtained from mares at the early (n = 12), mid (n = 12) and late (n = 12) luteal phases and the follicular phase (n = 12) of the estrous cycle. Additionally, all endometria were classified microscopically as belonging to Categories I and II or III according to the Kenney classification, resulting in allocation of 4 samples for each subcategory, e.g., mid luteal I, II and III. Relative mRNA transcription was quantified using Real-time PCR. Concentrations of PGE(2) and PGF(2α) in the endometrial extracts were determined using enzyme-linked immunosorbent assay (EIA). In Category I, PTGS-2 mRNA transcription was upregulated at the mid (P < 0.05) and late luteal phases (P < 0.001) and at the follicular phase (P < 0.05) compared to the early luteal phase. PGFS mRNA transcription as well as PGF(2α) concentrations increased at the mid (P < 0.01) and late (P < 0.05) luteal phases compared to the early luteal phase in Category I. PGES mRNA transcription was higher at the mid (P < 0.01) and late luteal phases (P < 0.05) compared to the early luteal and follicular phases in Category I. Prostaglandin E(2) concentration in Category I was higher at the mid luteal phase (P < 0.01) compared to all other phases of the estrous cycle. During incipient endometrosis (Category II) and under full endometrosis (Category III), PTGS-2, PGFS and PGES mRNA transcription and PG concentration were altered compared to the respective estrous phases in healthy endometria (P < 0.05). It may be concluded that serious changes in mRNA transcription of PG synthases and PG production that occur in the equine endometrium during the course of fibrosis in the estrous cycle could be responsible for disturbances leading to disorders of the estrous cycle and early embryo losses.

Early pregnancy induced expression of prostaglandin E2 receptors EP2 and EP4 in the ovine endometrium and regulated by interferon tau through multiple cell signaling pathways

Prostaglandin E2 (PGE(2)) plays pleiotropic roles at fetal-maternal interface during establishment of pregnancy. The objectives of the study were to: (i) determine regulation of PGE2 receptors EP1, EP2, EP3, and EP4 in the endometrium during the estrous cycle and early pregnancy; and (ii) understand endometrial epithelial and stromal cell-specific hormonal regulation of EP2 and EP4 in sheep. Results indicate that: (i) early pregnancy induces expression of EP2 and EP4 but not EP1 and EP3 proteins in the endometrium on days 12-16 compared to that of estrous cycle; (ii) intrauterine infusion of interferon tau (IFNT) increases expression of EP2 and EP4 proteins in endometrium; and (iii) IFNT activates distinct epithelial and stromal cell-specific JAK, EGFR, ERK1/2, AKT, or JNK signaling module to regulate expression of EP2 and EP4 proteins in the ovine endometrium. Our results indicate a role for EP2 and EP4-mediated PGE(2) signaling in endometrial functions and establishment of pregnancy in ruminants.

Uterine histotroph and conceptus development: select nutrients and secreted phosphoprotein 1 affect mechanistic target of rapamycin cell signaling in ewes

Interferon tau (IFNT), the pregnancy recognition signal in ruminants, abrogates the uterine luteolytic mechanism to ensure maintenance of function for the corpora lutea to produce progesterone (P4). IFNT also suppresses expression of classical IFN-stimulated genes by uterine lumenal epithelium (LE) and superficial glandular (sGE) epithelium but, acting in concert with progesterone, affects expression of a multitude of genes critical to growth and development of the conceptus. The LE and sGE secrete proteins and transport nutrients into the uterine lumen necessary for conceptus development, pregnancy recognition signaling, and implantation. Secretions include arginine and secreted phosphoprotein 1 (SPP1). Arginine can be metabolized to nitric oxide and to polyamines or act directly to activate the mechanistic target of rapamycin cell signaling pathway to stimulate proliferation, migration, and mRNA translation in trophectoderm cells. SPP1 binds alphavbeta3 and alpha5beta1 integrins to induce focal adhesion assembly, adhesion, and migration of conceptus trophectoderm cells during implantation. Thus, arginine and SPP1 mediate growth, migration, cytoskeletal remodeling, and adhesion of trophectoderm essential for pregnancy recognition signaling and implantation. This minireview focuses on components of histotroph that affect conceptus development in the ewe.

Interferon tau regulates PGF2alpha release from the ovine endometrial epithelial cells via activation of novel JAK/EGFR/ERK/EGR-1 pathways

In ruminants, pulsatile release of prostaglandin F2α (PGF(2α)) from the endometrium is transported to the ovary and induces luteolysis thereby allowing new estrous cycle. Interferon tau (IFNT), a type 1 IFN secreted by the trophoblast cells of the developing conceptus, acts on endometrial luminal epithelial (LE) cells and inhibits pulsatile release of PGF(2α) and establishes pregnancy. One of the unknown mechanisms is that endometrial pulsatile release of PGF(2α) is inhibited whereas basal release of PGF(2α) is increased in pregnant compared with nonpregnant sheep. We have recently found that pulsatile release of PGF(2α) from the endometrium is regulated by prostaglandin transporter (PGT)-mediated mechanisms. We hypothesize that modulation in the endometrial pulsatile vs. basal release of PGF(2α) likely requires PGT-mediated selective transport, and IFNT interacts with PGT protein and modulates pulsatile vs. basal release of PGF(2α). The new findings of the present study are: 1) IFNT activates novel JAK-SRC kinase-EGFR-RAS-RAF-ERK1/2-early growth response (EGR)-1 signaling module in LE cells; 2) IFNT increases interactions between PGT and ERK1/2 or EGR-1 proteins and alters phosphorylation of PGT protein; 3) IFNT precludes action of protein kinase C and Ca(2+) on PGT function; and 4) IFNT inhibits 80% PGT-mediated but not 20% simple diffusion-mediated release of PGF(2α) from the endometrial LE cells through this novel signaling module. The results of the present study provide important new insights on IFNT signaling and molecular control of PGT-mediated release of PGF(2α) and unravel the underlying mechanisms responsible for the increased basal release of PGF(2α) at the time of establishment of pregnancy in ruminants.

Discovery of candidate genes and pathways in the endometrium regulating ovine blastocyst growth and conceptus elongation

Establishment of pregnancy in ruminants requires blastocyst growth to form an elongated conceptus that produces interferon tau, the pregnancy recognition signal, and initiates implantation. Blastocyst growth and development requires secretions from the uterine endometrium. An early increase in circulating concentrations of progesterone (P4) stimulates blastocyst growth and elongation in ruminants. This study utilized sheep as a model to identify candidate genes and regulatory networks in the endometrium that govern preimplantation blastocyst growth and development. Ewes were treated daily with either P4 or corn oil vehicle from day 1.5 after mating to either day 9 or day 12 of pregnancy when endometrium was obtained by hysterectomy. Microarray analyses revealed many differentially expressed genes in the endometria affected by day of pregnancy and early P4 treatment. In situ hybridization analyses revealed that many differentially expressed genes were expressed in a cell-specific manner within the endometrium. The Database for Annotation, Visualization, and Integrated Discovery (DAVID) was used to identify functional groups of genes and biological processes in the endometrium that are associated with growth and development of preimplantation blastocysts. Notably, biological processes affected by day of pregnancy and/or early P4 treatment included lipid biosynthesis and metabolism, angiogenesis, transport, extracellular space, defense and inflammatory response, proteolysis, amino acid transport and metabolism, and hormone metabolism. This transcriptomic data provides novel insights into the biology of endometrial function and preimplantation blastocyst growth and development in sheep.

Expression of endometrial protein kinase a during early pregnancy in bonnet monkeys (Macaca radiata)

Embryo-induced signaling pathways are considered to be important for initiation and sustenance of pregnancy. However many of these pathways remain to be deciphered in primates. In the present study, differential display RT-PCR was used to identify genes or gene fragments that are differentially expressed in endometrium of bonnet monkeys (Macaca radiata) on Day 6 of pregnancy. Of several fragments found to be differentially expressed, a fragment of 567 base pair (named GG1) was characterized in detail. GG1 was highly represented in endometrium of pregnant animals compared with that of nonpregnant animals. Sequencing analysis revealed homology of this fragment to exons 7, 8, 9, and 10 and surprisingly to intron 6 of cAMP-dependent protein kinase A (PKA) regulatory type I alpha (tissue-specific extinguisher 1) (PRKAR1A). The increased expression of this fragment in gestational endometrium was confirmed by quantitative PCR studies. Two transcripts of 3.0 kilobase (kb) and 1.5 kb were detected in Northern blot probed with labeled GG1. Protein expressions of alpha regulatory (PRKAR1A) and alpha catalytic (PRKCA) subunits of PKA were also higher in gestational endometrium compared with that in nongestational endometrium. Further in vitro studies using human endometrial explants demonstrated regulation of PRKAR1A (or GG1) and prostaglandin-endoperoxide synthase 2 or cyclooxygenase 2 (PTGS2) by estradiol. This is the first study to date on the differential expression of PKA in primate endometrium during early pregnancy and its in vitro regulation by estradiol.

Quantitative characterization of prostaglandins in the uterus of early pregnant cattle

Prostaglandins (PGs) are important regulators of reproductive processes including early embryonic development. We analyzed the most relevant PG in bovine uteri at different preimplantation pregnancy stages when compared with non-pregnant controls. Additionally, endometrium and trophoblast tissues were examined regarding specific enzymes and receptors involved in PG generation and function. Simmental heifers were artificially inseminated or received seminal plasma only. At days 12, 15, or 18, post-estrus uteri were flushed for PG determination by liquid chromatography–tandem mass spectrometry. Endometrium and trophoblast tissues were sampled for RNA extraction and quantitative real-time PCR analysis. At all days and points of time examined, the concentration of 6-keto PGF1α (stable metabolite of PGI2) was predominant followed by PGF2α>PGE2>PGD2≈TXB2 (stable metabolite of TXA2). At days 15 and 18, PG increased from overall low levels at day 12, with a much more pronounced increase during pregnancy. The PGF2α/PGE2 ratio was not influenced by status. The highest PG concentration was measured at day 15 with 6-keto PGF1α (6.4 ng/ml) followed by PGF2α (1.1 ng/ml) and PGE2 (0.3 ng/ml). Minor changes in endometrial PG biosynthesis enzymes occurred due to pregnancy. Trophoblasts revealed high transcript abundance of general and specific PG synthases contributing to uterine PG. As PGI2 and PGF2α receptors were abundantly expressed by the trophoblast, abundant amounts of PGI2 and PGF2α in the uterine lumen point towards an essential role of PG for the developing embryo. High amounts of PG other than PGE2 in the preimplantation uterus may be essential rather than detrimental for successful reproduction.

Species Comparison of the Role of p38 MAP Kinase in the Female Reproductive System

The p38 mitogen-activated protein kinases (MAPKs) are members of discrete signal transduction pathways that have significant regulatory roles in a variety of biological processes, depending on the cell, tissue and organ type. p38 MAPKs are involved in inflammation, cell growth and differentiation and cell cycle. In the female reproductive system, p38 MAPKs are known to regulate various aspects of the reproductive process such as mammalian estrous and menstrual cycles as well as early pregnancy and parturition. p38 MAPKs have also been implicated in alterations and pathologies observed in the female reproductive system. Therefore, pharmacologic modulation of p38 MAPKs, and inter-connected signaling pathways (e.g., estrogen receptor signaling, c-fos, c-jun), may influence reproductive physiology and function. This article provides a critical, comparative review of available data on the roles of p38 MAPKs in the mammalian female reproductive system and in reproductive pathophysiology in humans and preclinical species. We first introduce fundamental differences and similarities of the mammalian female reproductive system that should be considered by toxicologists and toxicologic pathologists when assessing the effects of new pharmacologic agents on the female reproductive system. We then explore in detail the known roles for p38 MAPKs and related molecules in female reproduction. This foundation is then extended to pathological conditions in which p38 MAPKs are thought to play an integral role.

Oxytocin receptor down-regulation is not necessary for reducing oxytocin-induced prostaglandin F(2alpha) accumulation by interferon-tau in a bovine endometrial epithelial cell line

Interferon-tau (IFNtau) is the embryonic signal responsible for pregnancy recognition in ruminants. The primary action of IFNtau is believed to be mediated through inhibition of prostaglandin F(2alpha) (PGF(2alpha)) released from the endometrial epithelial cells in response to oxytocin (OT). Our working hypothesis was that the antiluteolytic effect of IFNtau also involved modulation of PG production downstream of OT receptor (OTR) and/or cyclooxygenase 2 (COX2). There is currently no OT-sensitive endometrial cell line to study the molecular mechanisms underlying our hypotheses. Therefore, we established an immortalized bovine endometrial epithelial cell line (bEEL) exhibiting OT response. These cells were cytokeratin positive, expressed steroid receptors, and exhibited preferential accumulation of PGF(2alpha) over PGE(2). The bEEL cells were highly sensitive to OT, showing time- and concentration-dependent increase in COX2 transcript and protein and PGF(2alpha) accumulation. Interestingly, IFNtau (20 ng/ml) significantly reduced OT-induced PGF(2alpha) accumulation, but surprisingly, the effect was not mediated through down-regulation of either OTR or COX2. Rather, IFNtau up-regulated COX2 in a time- and concentration-dependent manner while decreasing OT-induced PG accumulation. This suggests that COX2 is not a primary target for the antiluteolytic effect of IFNtau. Because IFNtau reduced OT-stimulated PGF(2alpha) accumulation within 3 h, the mechanism likely involves a direct interference at the level of the OT signaling or transcription in addition to the down-regulation of OTR observed in vivo. In summary, bEEL cells offer a unique in vitro model for investigating the cellular and molecular mechanisms underlying OT and IFNtau response in relation with luteolysis and recognition of pregnancy in the bovine.

Development and characterization of a simian virus 40 immortalized bovine endometrial stromal cell line

In ruminants, interferon-tau (IFNtau) is the maternal recognition signal inhibiting prostaglandin (PG) F2alpha production by endometrial epithelial cells and stimulating interferon-stimulated genes in the stroma. Stromal cells mediate the action of progesterone on epithelial cells during pregnancy. Our working hypothesis is that IFNtau acts as a molecular switch that turns on PGE(2) production in endometrial stromal cells while suppressing PGF2alpha production from epithelial cells. In this report we document immortalization and functional characterization of a bovine stromal cell line from the caruncular region of the endometrium [caruncular stromal cell (CSC)]. Primary stromal cells were immortalized by nucleofection with simian virus 40 large T antigen and integrase. The resulting cell line, CSC, expresses stromal cell-specific vimentin, estrogen, and progesterone receptors, and is amenable for transient transfection. Basal and stimulated production of PGE2 is higher than PGF2alpha and associated with cyclooxygenase (COX) 2 expression. Phorbol myristate acetate (PMA) and IFNtau up-regulate COX2 and PG production in a dose-dependent manner. When added together, low concentrations of IFNtau inhibit PMA-induced COX2 expression; whereas this inhibition is lost at high concentrations. Expression of signal transducer and activator of transcription 1 is induced by IFNtau at all concentrations studied but is not modulated by PMA. Because expression of signal transducer and activator of transcription 1 does not exhibit the biphasic response to IFNtau, we investigated the p38 MAPK pathway using the selective inhibitor SB203580. Inhibition of the p38 MAPK pathway abolishes IFNtau action on PG production. In summary, CSC appears as a good stromal cell model for investigating the molecular mechanisms related to IFNtau action and PG production in the bovine.

Prostaglandins and the initiation of blastocyst implantation and decidualization

The process of blastocyst implantation in mammals is remarkably variable, especially in the extent of trophoblast invasion of the endometrium. In most species studied, the earliest macroscopically identifiable sign of blastocyst implantation is an increase in endometrial vascular permeability in areas adjacent to the blastocysts. This is followed in species with invasive implantation by decidualization, again localized to areas adjacent to the blastocysts. In some species, the application of a stimulus to the endometrium can result in increased endometrial vascular permeability and decidualization. Based initially on studies utilizing inhibitors of prostaglandin (PG) synthesis and more recently on studies using the techniques of transgenics, considerable evidence has accumulated indicating that PGs have an important role in the early events of implantation and artificially induced decidualization. However, which PGs are involved remains controversial. There may be differences between species, and different PGs may be involved at different times.

A microarray analysis for genes regulated by interferon-tau in ovine luminal epithelial cells

Interferon-tau (IFNT) is released by preimplantation conceptuses of ruminant species and prepares the mother for pregnancy. Although one important function is to protect the corpus luteum from the luteolytic activity of prostaglandin-F 2alpha, IFNT most likely regulates a range of other physiological processes in endometrium. Here, an immortalized cell line from ovine uterine luminal epithelial cells was treated with IFNT for either 8 or 24 h. RNA was subjected to cDNA microarray analysis, with RNA from untreated cells as the reference standard. Of 15 634 genes, 1274 (8%) were IFNT responsive at P<0.01 and 585 at P<0.001 to at least one treatment. Of the latter, 356 were up-regulated and 229 down-regulated. Increasing IFNT concentrations from 10 ng/ml to 10 microg/ml had minor effects, and most genes up- or down-regulated at 8 h were regulated similarly at 24 h. Although IFNT influences many genes implicated in antiviral activity and apoptosis, its action also likely regulates prostaglandin metabolism, growth factors and their receptors, apoptosis and the nuclear factor (NF)-kappaB cascade, extracellular matrix accretion, angiogenesis, blood coagulation, and inflammation. In particular, it increased mRNA concentrations of genes related to the vascular endothelial growth factor R2 pathway of angiogenesis and down-regulated ones associated with hypoxia. Two genes implicated in the antiluteolytic actions of IFNT (encoding cyclooxygenase-2 and the oxytocin receptor respectively) were down-regulated in response to all treatments. IFNT targets a complex range of physiological processes during the establishment of pregnancy.

Immunoendocrine aspects of endometrial function and implantation

Effective ovarian and uterine function relies on a complex interplay between the endocrine and immune systems. It is generally accepted that in reproductive tissues, oestradiol and progesterone have pro- and anti-inflammatory activities respectively and, in this regard, the paracrine effects of the sex steroids on the ovary are similar to the endocrine effects on the uterus. Ovarian leukocyte recruitment and cytokine release are central to follicle development, ovulation and corpus luteum function. At the uterine level, the cyclical changes in sex steroids regulate the number and distribution of endometrial and decidual immune cells as well as other immune signalling and surveillance factors. The uterine mucosa is unique, in that it must tolerate sperm and the allogeneic blastocyst in a way that does not compromise uterine immune surveillance against bacteria, yeast and viruses. Crosstalk between the sex steroids and immune mediators (systemic and local) are central to these functions, and this article will review these mechanisms and their importance for successful reproductive function and pregnancy success.

Pregnancy recognition and conceptus implantation in domestic ruminants: roles of progesterone, interferons and endogenous retroviruses

The present review highlights new information on pregnancy recognition and conceptus development and implantation in sheep with respect to regulation by progesterone, interferons and endogenous retroviruses. After formation of the corpus luteum, progesterone acts on the endometrium and stimulates blastocyst growth and elongation to a filamentous conceptus (embryo/fetus and associated extra-embryonic membranes). The envelope of endogenous retroviruses related to Jaagsiekte sheep retroviruses appears to intrinsically regulate mononuclear trophectoderm cell proliferation and differentiation into trophoblast giant binucleate cells. The mononuclear trophectoderm cells of elongating sheep conceptuses secrete interferon-tau, which acts on the endometrium to prevent development of the luteolytic mechanism by inhibiting transcription of the gene for the oestrogen receptor alpha in the luminal and superficial ductal glandular epithelia. These actions prevent oestrogen-induced transcription of the oxytocin receptor gene and, therefore, oxytocin-induced luteolytic pulses of prostaglandin F2alpha. Progesterone down regulation of its receptors in luminal and glandular epithelia correlates temporally with a reduction in anti-adhesive mucin land induction of secreted galectin 15 (LGALSI5) and secreted phosphoprotein 1, which are proposed to regulate trophectoderm proliferation and adhesion. Interferon-c acts on the endometrial lumenal epithelium to induce WNT7A and to stimulate LGALS 15, cathepsin L and cystatin C, which are candidate regulators of conceptus development and implantation. The number of potential contributors to maternal recognition and establishment of pregnancy continues to grow and this highlights our limited appreciation of the complexity of the key molecules and signal transduction pathways that intersect during these key developmental processes. The goal of improving reproductive efficiency by preventing embryonic losses that occur during the peri-implantation period of pregnancy in domestic ruminants provides the challenge to increase our knowledge of endometrial function and conceptus development.

Pregnancy, Bovine Somatotropin, and Dietary n-3 Fatty Acids in Lactating Dairy Cows: II. Endometrial Gene Expression Related to Maintenance of Pregnancy

The objectives were to examine the effects of bovine somatotropin (bST), pregnancy, and dietary fatty acids on expression of key endometrial genes and proteins regulating prostaglandin synthesis in lactating dairy cows. Two diets were fed, at about 17 d in milk (DIM), in which oil of whole cottonseed (control diet) was compared with calcium salts of fish oil-enriched lipid (FO). Ovulation was synchronized in cows with a presynchronization plus Ovsynch protocol and cows were inseminated artificially or not inseminated on d 0 (d 0 = time of synchronized ovulation; 77 +/- 12 DIM). On d 0 and 11, cows received bST (500 mg) or no bST, and were slaughtered on d 17 to recover uterine secretions and endometrial tissue. Number of cows in the control diet: 5 bST-treated cyclic (bST-C), 5 non-bST-treated cyclic (no bST-C), 4 bST-treated pregnant (bST-P), and 5 non-bST-treated pregnant (no bST-P) cows and in the FO diet: 4 bST-treated FO-cyclic (bST-FO-C) and 5 non-bST-treated cyclic (no bST-FO-C) cows. The FO diet increased progesterone receptor (PR) mRNA, and treatment with bST increased PR mRNA concentration in endometrium of no bST-C, but not in no bST-FO-C or no bST-P cows. Concentrations of estrogen receptor-alpha (ERalpha) mRNA and protein, and oxytocin receptor (OTR) mRNA were decreased in no bST-P cows compared with no bST-C cows. Treatment with bST tended to increase OTR and ERalpha mRNA concentrations in cyclic cows fed control or FO diets. Immunohistochemistry demonstrated effects of bST, FO, and pregnancy on distributions of ERalpha and PR proteins in endometrium. Pregnancy and FO feeding decreased ERalpha abundance in luminal epithelium. Prostaglandin H synthase-2 (PGHS-2) protein was elevated in pregnant cows and localized to the luminal epithelium. Both FO and bST treatments reduced staining intensity of PGHS-2 protein. Concentrations of prostaglandin E synthase mRNA were elevated in either cyclic or pregnant cows in response to bST, whereas bST decreased prostaglandin F synthase mRNA in pregnant cows. Uterine lumen fluids had more PGF2alpha and prostaglandin E2 in pregnant than cyclic cows. Uterine lumen fluids of bST-P cows contained more prostaglandin E2 than those from no bST-P cows. In summary, both pregnancy and bST altered endometrial gene expression, and cyclic cows responded differently to bST than pregnant cows. Feeding FO modulated PR, ERalpha, and PGHS-2 expression and distribution among endometrial cell types in a manner that may favor establishment and maintenance of pregnancy.

Estrogen regulates transcription of the ovine oxytocin receptor gene through GC-rich SP1 promoter elements

Establishment of pregnancy in ruminants results from paracrine signaling by interferon tau (IFNT) from the conceptus to uterine endometrial luminal epithelia (LE) that prevents release of luteolytic prostaglandin F(2alpha) pulses. In cyclic and pregnant ewes, progesterone down-regulates progesterone receptor (PGR) gene expression in LE. In cyclic ewes, loss of PGR allows for increases in estrogen receptor alpha (ESR1) and then oxytocin receptor (OXTR) gene expression followed by oxytocin-induced prostaglandin F(2alpha) pulses. In pregnant ewes, IFNT inhibits transcription of the ESR1 gene, which presumably inhibits OXTR gene transcription. Alternatively, IFNT may directly inhibit OXTR gene transcription. The 5' promoter/enhancer region of the ovine OXTR gene was cloned and found to contain predicted binding sites for activator protein 1, SP1, and PGR, but not for ESR1. Deletion analysis showed that the basal promoter activity was dependent on the region from -144 to -4 bp that contained only SP1 sites. IFNT did not affect activity of the OXTR promoter. In cells transfected with ESR1, E2, and ICI 182,780 increased promoter activity due to GC-rich SP1 binding sites at positions -104 and -64. Mutation analyses showed that the proximal SP1 sites mediated ESR1 action as well as basal activity of the promoter. In response to progesterone, progesterone receptor B also increased OXTR promoter activity. SP1 protein was constitutively expressed and abundant in the LE of the ovine uterus. These results support the hypothesis that the antiluteolytic effects of IFNT are mediated by direct inhibition or silencing of ESR1 gene transcription, thereby precluding ESR1/SP1 from stimulating OXTR gene transcription.

Effects of Bovine Somatotropin on Uterine Genes Related to the Prostaglandin Cascade in Lactating Dairy Cows

Multiparous Holstein cows, averaging 80 d in milk, were used to examine the effect of exogenous bovine somatotropin (bST) on uterine expression of estrogen receptor alpha (ERalpha), prostaglandin endoperoxide synthase-2 (PGHS-2), and peroxisome proliferator-activated receptor delta (PPARdelta). About 12 h before expected ovulation in a synchronization protocol, cows were assigned to receive bST (500 mg, n = 11) or serve as untreated controls (n = 10). Cows that ovulated (n = 9 bST, 8 control) were divided within treatment to be killed on d 3 or 7 postovulation. Samples of intercaruncular endometrial tissue from uterine horns ipsilateral to the corpus luteum were collected and stored at -80 degrees C for subsequent mRNA analyses. Endometrial concentrations of ERalpha and PGHS-2 mRNA transcripts were greater on d 7 than on d 3 of the estrous cycle, but did not differ between treatments. Compared with untreated cows, short-term bST treatment decreased PGHS-2 protein expression at d 7 of the estrous cycle. Concentration of PPARdelta mRNA transcript in the uterus decreased between d 3 and 7 of the estrous cycle and was negatively correlated with ERalpha and PGHS-2 mRNA concentrations. Short-term administration of bST to lactating dairy cows had minimal effects on uterine genes encoding ERalpha, PGHS-2, and PPARdelta at d 3 and 7 of the estrous cycle but there may be an inverse relationship between PPARdelta and uterine expression of ERalpha and PGHS-2 genes.

Pregnancy and Bovine Somatotropin in Nonlactating Dairy Cows: II. Endometrial Gene Expression Related to Maintenance of Pregnancy

The objective was to evaluate the effects of pregnancy and bovine somatotropin (bST) on endometrial gene and protein expression related to maintenance of pregnancy in nonlactating dairy cows at d 17. In endometrial tissues, treatment with bST increased the steady state concentration of oxytocin receptor (OTR) mRNA; bST-treated cyclic (bST-C) cows had greater OTR mRNA than bST-treated pregnant (bST-P) cows. Estradiol receptor alpha (ERalpha) mRNA was reduced in bST-P cows compared with control P and C (no bST) cows. Western blotting revealed that pregnancy decreased the abundance of ERalpha protein, and bST stimulated an increase in ERalpha protein in C and P cows. Treatment with bST increased steady state concentrations of progesterone receptor (PR) mRNA. No differences were detected in steady state mRNA concentrations of prostaglandin H synthase-2 (PGHS-2), prostaglandin E synthase, and prostaglandin F synthase due to pregnancy or bST treatment. However, PGHS-2 protein was increased in response to pregnancy and bST treatment. Immunostaining indicated that P decreased ERalpha protein in luminal epithelium and increased PR protein in epithelial cells of the uterine glands. The PR protein response in the glands was less in bST-P cows than in P cows. In the stromal layer of the endometrium, bST decreased PR protein abundance in C and P cows. The PGHS-2 protein was localized exclusively in the luminal epithelium cells of endometrium and was increased in P cows. In conclusion, distinctly different mRNA and protein responses were detected between C and P cows related to prostaglandin biosynthesis, and bST-induced changes may potentially impact mechanisms associated with maintenance of pregnancy in nonlactating cows.

Conceptus signals for establishment and maintenance of pregnancy

Establishment and maintenance of pregnancy results from signaling by the conceptus (embryo/fetus and associated extraembryonic membranes) and requires progesterone produced by the corpus luteum (CL). In most mammals, hormones produced by the trophoblast maintain progesterone production by acting directly or indirectly to maintain the CL. In domestic animals (ruminants and pigs), hormones from the trophoblast are antiluteolytic in that they act on the endometrium to prevent uterine release of luteolytic prostaglandin F2 alpha (PGF). In cyclic and pregnant sheep, progesterone negatively autoregulates expression of the progesterone receptor (PR) gene in the endometrial luminal (LE) and superficial glandular epithelium (GE). Available evidence in cyclic sheep indicates that loss of the PR is closely followed by increases in epithelial estrogen receptors (ER) and then oxytocin receptors (OTR), allowing oxytocin to induce uterine release of luteolytic PGF pulses. In pregnant sheep, the conceptus trophoblast produces interferon tau (IFN tau) that acts on the endometrium to inhibit transcription of the ER alpha gene directly and the OTR gene indirectly to abrogate development of the endometrial luteolytic mechanism. Subsequently, sequential, overlapping actions of progesterone, IFN tau, placental lactogen (PL) and growth hormone (GH) comprise a hormonal servomechanism that regulates endometrial gland morphogenesis and terminal differentiated function to maintain pregnancy in sheep. In pigs, the conceptus trophoblast produces estrogen that alters the direction of PGF secretion from an endocrine to exocrine direction, thereby sequestering luteolytic PGF within the uterine lumen. Conceptus estrogen also increases expression of fibroblast growth factor 7 (FGF-7) in the endometrial LE that, in turn, stimulates proliferation and differentiated functions of the trophectoderm, which expresses the FGF-7 receptor. Strategic manipulation of these physiological mechanisms can offer therapeutic schemes to improve uterine capacity, conceptus survival and reproductive health.

Conceptus signals for establishment and maintenance of pregnancy

Establishment and maintenance of pregnancy results from signaling by the conceptus (embryo/fetus and associated extraembryonic membranes) and requires progesterone produced by the corpus luteum. In most mammals, hormones produced by the trophoblast maintain progesterone production by acting directly or indirectly to maintain the corpus luteum. In domestic animals (ruminants and pigs), hormones from the trophoblast are antiluteolytic in that they act on the endometrium to prevent uterine release of luteolytic prostaglandin F2alpha. In cyclic and pregnant sheep, progesterone negatively autoregulates progesterone receptor gene expression in the endometrial luminal and superficial glandular epithelium. In cyclic sheep, loss of the progesterone receptor is closely followed by increases in epithelial estrogen receptors and then oxytocin receptors, allowing oxytocin to induce uterine release of luteolytic prostaglandin F2alpha pulses. In pregnant sheep, the conceptus trophoblast produces interferon tau that acts on the endometrium to inhibit transcription of the estrogen receptor alpha gene directly and the oxytocin receptor gene indirectly to abrogate development of the endometrial luteolytic mechanism. Subsequently, sequential, overlapping actions of progesterone, interferon tau, placental lactogen, and growth hormone comprise a hormonal servomechanism that regulates endometrial gland morphogenesis and terminal differentiated function to maintain pregnancy in sheep. In pigs, the conceptus trophoblast produces estrogen that alters the direction of prostaglandin F2alpha secretion from an endocrine to exocrine direction, thereby sequestering luteolytic prostaglandin F2alpha within the uterine lumen. Conceptus estrogen also increases expression of fibroblast growth factor 7 in the endometrial lumenal epithelium that, in turn, stimulates proliferation and differentiated functions of the trophectoderm, which expresses the fibroblast growth factor 7 receptor. Strategic manipulation of these physiological mechanisms may improve uterine capacity, conceptus survival, and reproductive health.

Differential Effects of Interferon-τ on the Prostaglandin Synthetic Pathway in Bovine Endometrial Cells Treated with Phorbol Ester

Rationale for these experiments was to evaluate the dose effects of bovine interferon-tau (IFN-tau) on the prostaglandin secretory pathway of immortalized bovine endometrial (BEND) cells in response to phorbol 12, 13-dibutyrate (PdBu) and to characterize similar responses in primary bovine uterine epithelial cells as a biomonitor of embryo-induced antiluteolytic effects on the endometrium. The BEND cells were treated with PdBu (0 or 100 ng/mL) and IFN-tau (0 or 50 ng/mL) for 6 h. The PdBu stimulated secretions of PGF2alpha and prostaglandin E2 (PGE2). Co-treatment of cells with IFN-tau blocked PdBu-induced secretion of both PGF2alpha and PGE2. Treatment with PdBu for 6 h induced expression of prostaglandin H synthase-2 mRNA, prostaglandin H synthase-2 protein, and prostaglandin E synthase mRNA, which were blocked with concurrent addition of IFN-tau. Doses of IFN-tau (0.05, 0.5, 1, 5, 10, and 20 microg/mL) were used with PdBu (0 and 100 ng/mL). The IFN-tau alone failed to stimulate secretion of PGF2alpha and PGE2, whereas IFN-tau doses <5 microg/mL suppressed PdBu-stimulated secretions of PGF2alpha and PGE2. Uterine epithelial cells were isolated from cows at d 17 after estrus and were cultured to confluence in serum-free medium. Cells were treated with IFN-tau (0, 50, or 500 ng/mL) and PdBu (0 or 100 ng/mL) before media were collected after 24 h for PGF2alpha and PGE2 analyses. Treatment of primary uterine epithelial cells with PdBu induced PGF2alpha secretion, and IFN-tau (50 and 500 ng/mL) caused a reduction in PGF2alpha secretion induced by PdBu. In the absence of PdBu, IFN-tau increased basal secretion of PGF2alpha. Concentrations of PGE2 increased in response to PdBu, and the 50-ng/mL dose of IFN-tau had a stimulatory effect on PGE2 concentrations compared with the 500-ng/mL dose in the absence of PdBu. Phorbol ester-induced gene transcription as related to prostaglandin synthesis is regulated by IFN-tau in vitro.

Progesterone and Placental Hormone Actions on the Uterus: Insights from Domestic Animals1

Progesterone is unequivocally required for maternal support of conceptus (embryo/fetus and associated extraembryonic membranes) survival and development. In cyclic sheep, progesterone is paradoxically involved in suppressing and then initiating development of the endometrial luteolytic mechanism. In cyclic and pregnant sheep, progesterone negatively autoregulates progesterone receptor (PR) gene expression in the endometrial luminal (LE) and superficial glandular epithelium (GE). In cyclic sheep, PR loss is closely followed by increases in epithelial estrogen receptor (ERalpha) and then oxytocin receptor (OTR), allowing oxytocin to induce uterine release of luteolytic prostaglandin F2alpha pulses. In pregnant sheep, the conceptus produces interferon tau (IFNtau) that acts on the endometrium to inhibit transcription of the ERalpha gene and thus development of the endometrial luteolytic mechanism. After Day 13 of pregnancy, the endometrial epithelia do not express the PR, whereas the stroma and myometrium remain PR positive. The absence of PR in the endometrial GE is required for onset of differentiated function of the glands during pregnancy. The sequential, overlapping actions of progesterone, IFNtau, placental lactogen (PL), and growth hormone (GH) comprise a hormonal servomechanism that regulates endometrial gland morphogenesis and terminal differentiated function during gestation. In pigs, estrogen, the pregnancy-recognition signal, increases fibroblast growth factor 7 (FGF-7) expression in the endometrial LE that, in turn, stimulates proliferation and differentiated functions of the trophectoderm, which expresses the receptor for FGF-7. Strategic manipulation of these physiological mechanisms may offer therapeutic schemes to improve uterine capacity, conceptus survival, and reproductive health of domestic animals and humans.