Placental development during early pregnancy in sheep: Progesterone and estrogen receptor protein expression

Evaluating estrus synchronization and early pregnancy detection in Ossimi sheep: The influence of fluorogestone acetate treatment duration and dosage

Estrus synchronization is important for improving sheep reproduction. To enhance sheep reproduction efficiency, this study investigated the impact of different durations (7 vs. 14 days) and fluorogestone acetate (FGA) doses in intravaginal sponges on estrus synchronization and early pregnancy detection in Ossimi sheep. Two hundred ewes were evenly divided into two groups, each receiving a full 40 mg or a halved 20 mg FGA sponge for their respective durations. The study aimed to optimize breeding efficiency by examining the effectiveness of these treatments in synchronizing estrous cycles and by evaluating the use of serum levels of pregnancy-associated glycoprotein 1 (PAG1) and progesterone (P4) as markers for early pregnancy identification. Prostaglandin F2α and equine chorionic gonadotropin were administered to enhance the synchronization process. Results highlighted that the 7-day treatment protocol significantly improved estrus, pregnancy, and lambing rates compared to the 14-day protocol. Furthermore, pregnant ewes demonstrated elevated levels of PAG1 and P4, with PAG1 levels particularly higher in ewes with multiple pregnancies. The findings underscore that the shorter duration of FGA treatment is more effective for reproductive management in Ossimi sheep without significantly affecting PAG1 levels based on the dose or duration of FGA. PAG1 also proved to be a reliable marker for early pregnancy detection, offering a promising approach to identifying fetal numbers early in pregnancy. This research suggests optimizing FGA sponge use could be cost-efficient for improving reproductive efficiency and early pregnancy management in sheep.

Histological, immunohistochemical and serological investigations of the ovary during follicular phase of estrous cycle in Saidi sheep

BACKGROUND

Saidi sheep are the most abundant ruminant livestock species in Upper Egypt, especially in the Assiut governorate. Sheep are one of the most abundant animals raised for food in Egypt. They can convert low-quality roughages into meat and milk in addition to producing fiber and hides therefore; great opportunity exists to enhance their reproduction. Saidi breed is poorly known in terms of reproduction. So this work was done to give more information on some hormonal, oxidative, and blood metabolites parameters in addition to histological, histochemical and immunohistochemical investigations of the ovary during follicular phase of estrous cycle. The present study was conducted on 25 healthy Saidi ewes for serum analysis and 10 healthy ewes for histological assessment aged 2 to 5 years and weighted (38.5 ± 2.03 kg).

RESULTS

The follicular phase of estrous cycle in Saidi sheep was characterized by the presence of ovarian follicles in different stages of development and atresia in addition to regressed corpus luteum. Interestingly, apoptosis and tissue oxidative markers play a crucial role in follicular and corpus luteum regression. The most prominent features of the follicular phase were the presence of mature antral (Graafian) and preovulatory follicles as well as increased level of some blood metabolites and oxidative markers. Here we give a new schematic sequence of ovarian follicles in Saidi sheep and describing the features of different types. We also clarified that these histological pictures of the ovary was influenced by hormonal, oxidative and blood metabolites factors that characterizes the follicular phase of estrous cycle in Saidi sheep.

CONCLUSION

This work helps to understanding the reproduction in Saidi sheep which assist in improving the reproductive outcome of this breed of sheep. These findings are increasingly important for implementation of a genetic improvement program and utilizing the advanced reproductive techniques as estrous synchronization, artificial insemination and embryo transfer.

Melatonin promotes progesterone secretion in sheep luteal cells by regulating autophagy via the AMPK/mTOR pathway

The corpus luteum is primarily responsible for the production and secretion of progesterone. Melatonin has been established to regulate autophagy and induce progesterone secretion in luteal cell. However, whether melatonin affects progesterone secretion by interfering with autophagy is yet to be reported. In the present study, the expression levels of melatonin receptors (MT1 and MT2), autophagy-related protein Beclin1 (Bec1), microtubule-associated protein light chain 3 B (LC3B), progesterone and steroidogenic acute regulatory protein (StAR), and cytochrome P450scc (CYP11A1) were analyzed in the corpus luteum of sheep at different stages (early, middle, and late); specifically, enzyme-linked immunosorbent assays, immunohistochemical staining, and western blotting were utilized for this expression analysis. In addition, to determine whether melatonin regulated progesterone secretion via the regulation of autophagy, luteal cells were cultured before being exposed to different concentrations of melatonin (0.01-100 nM) and the autophagy inhibitor chloroquine (50 μM). Next, luteal cells were treated with the melatonin receptor inhibitors 4-phenyl-2-propionamidotetralin (1 μM) and luzindole (1 μM) before detecting Bec1, LC3B2, AMPK/mTOR, and progesterone secretion levels to ascertain whether the effect of melatonin on autophagy and progesterone secretion is mediated by its corresponding receptors in luteal cells. Finally, to determine the significance of the AMPK/mTOR pathway in this process, an AMPK inhibitor, Compound C (10 μM), was added to luteal cells. Overall, the highest expression of melatonin receptors, autophagy and progesterone secretion was observed in the middle-phase corpus luteum; additionally, melatonin promoted autophagy, at least partially, through its receptor-mediated AMPK/mTOR pathway, which thereby promoting progesterone secretion in luteal cells in vitro. Ultimately, this study is the first to clarify the important role of autophagy in the melatonin-mediated regulation of progesterone secretion in the corpus luteum of sheep; it also lays a foundation for further exploration into the role of melatonin in regulating sheep's ovarian function.

One-carbon metabolite supplementation to nutrient-restricted beef heifers affects placental vascularity during early pregnancy

We hypothesized that restricted maternal nutrition and supplementation of one-carbon metabolites (OCM; methionine, folate, choline, and vitamin B12) would affect placental vascular development during early pregnancy. A total of 43 cows were bred, and 32 heifers successfully became pregnant with female calves, leading to the formation of four treatment groups: CON - OCM (n = 8), CON + OCM (n = 7), RES - OCM (n = 9), and RES + OCM (n = 8). The experimental design was a 2 × 2 factorial, with main factors of dietary intake affecting average daily gain: control (CON; 0.6 kg/d ADG) and restricted (RES; -0.23 kg/d ADG); and OCM supplementation (+OCM) in which the heifers were supplemented with rumen-protected methionine (7.4 g/d) and choline (44.4 g/d) and received weekly injections of 320 mg of folate and 20 mg of vitamin B12, or received no supplementation (-OCM; corn carrier and saline injections). Heifers were individually fed and randomly assigned to treatment at breeding (day 0). Placentomes were collected on day 63 of gestation (0.225 of gestation). Fluorescent staining with CD31 and CD34 combined with image analysis was used to determine the vascularity of the placenta. Images were analyzed for capillary area density (CAD) and capillary number density (CND). Areas evaluated included fetal placental cotyledon (COT), maternal placental caruncle (CAR), whole placentome (CAR + COT), intercotyledonary fetal membranes (ICOT, or chorioallantois), intercaruncular endometrium (ICAR), and endometrial glands (EG). Data were analyzed with the GLM procedure of SAS, with heifer as the experimental unit and significance at P ≤ 0.05 and a tendency at P > 0.05 and P < 0.10. Though no gain × OCM interactions existed (P ≥ 0.10), OCM supplementation increased (P = 0.01) CAD of EG, whereas nutrient restriction tended (P < 0.10) to increase CAD of ICOT and CND of COT. Additionally, there was a gain × OCM interaction (P < 0.05) for CAD within the placentome and ICAR, such that RES reduced and supplementation of RES with OCM restored CAD. These results indicate that maternal rate of gain and OCM supplementation affected placental vascularization (capillary area and number density), which could affect placental function and thus the efficiency of nutrient transfer to the fetus during early gestation.

Ovine placental explants: A new ex vivo model to study host‒pathogen interactions in reproductive pathogens

Reproductive failure is one of the main performance constraints in ruminant livestock. Transmissible agents such as Toxoplasma gondii and Neospora caninum are commonly involved in the occurrence of abortion in ruminants, but little is known about the mechanisms involved. While in vivo models are optimal for the study of abortion pathogenesis, they have a high economic cost and come with ethical concerns. Unfortunately, alternative in vitro models fail to replicate the complex in vivo placental structure. To overcome the limitations of currently available models, we developed an ex vivo model based on the cultivation of fresh and cryopreserved sheep placental explants, enabling the biobanking of tissues. Reproducible and simple markers of tissue integrity (histology, RNA concentrations), viability (resazurin reduction), and functionality (synthesis of steroid hormones) were also investigated, allowing a clear quality assessment of the model. This work shows that, similar to fresh explants, tissues cryopreserved in ethylene glycol using slow freezing rates maintain not only their structure and function but also their receptivity to T. gondii and N. caninum infection. In addition, the findings demonstrate that explant lifespan is mainly limited by the culture method, with protocols requiring improvements to extend it beyond 2 days. These findings suggest that cryopreserved tissues can be exploited to study the initial host‒pathogen interactions taking place in the placenta, thus deepening the knowledge of the specific mechanisms that trigger reproductive failure in sheep. Importantly, this work paves the way for the development of similar models in related species and contributes to the reduction of experimental animal use in the future.

Spatial and temporal expression profile of sex steroid receptors and antioxidant enzymes in the maternal-fetal interface of domestic cats

Sex steroids and antioxidant enzymes modulate uterine and placental physiology. Failures in the expression, signaling, and/or secretion of these mediators are associated with female infertility and gestational problems. However, there is no data on the expression profile of receptors for sex steroids and antioxidant enzymes in the maternal-fetal interface of domestic cats. Uterus and placenta samples from non-pregnant diestrus cats and cats in mid- and late pregnancy were used to analyze the protein and gene expression of the receptors for estrogen alpha (ERα), progesterone (PR), and androgen (AR) and the antioxidant enzymes superoxide dismutase 1 (SOD1), catalase, and glutathione peroxidase 1 (GPX1) by immunohistochemistry and qPCR. Higher uterine expression of ERα, Pr, and Sod1 was observed in the pregnant cats, especially in mid-pregnancy, compared to non-pregnant diestrus cats, as well as reduced endometrial catalase immunostaining. In the placenta, the mRNA expression of Erα, Pr, Ar, and Gpx1 was higher in late pregnancy in relation to mid-pregnancy. Moreover, weak or no placental expression was observed for catalase in mid- and late pregnancy, while strong immunostaining was observed for AR in trophoblasts and decidual cells in mid-pregnancy. The findings of this study demonstrated that pregnancy in female cats increases the uterine expression of sex steroid receptors and antioxidant enzymes, and that the placental expression of these mediators varies according to gestational age.

An Exploratory Data Analysis from Ovine and Bovine RNA-Seq Identifies Pathways and Key Genes Related to Cervical Dilatation

The present study developed a review and exploration of data in public and already validated repositories. The main objective was to identify the pathways involved in ruminants' cervical dilatation, which are conserved between cattle and sheep in the follicular and luteal phases of the reproductive cycle. In cattle, 1961 genes were more differentially expressed in the follicular phase and 1560 in the luteal phase. An amount of 24 genes were considered exclusively expressed from these. A total of 18 genes were in the follicular phase and 6 genes were in the luteal phase. In sheep, 2126 genes were more differentially expressed in the follicular phase and 2469 genes were more differentially expressed in the luteal phase. Hoxb genes were identified in both species and are correlated with the PI3K/Akt pathway. PI3K/Akt was also found in both cattle and sheep, appearing prominently in the follicular and luteal phases of both species. Our analyses have pointed out that the PI3K/Akt pathway and the Hoxb genes appear in prominence in modulating mechanisms that involve estrus alterations in the cervix. PI3K/Akt appears to be an important pathway in the cervical relaxation process.

Effects of dietary supplementation with N-carbamylglutamate on maternal endometrium and fetal development during early pregnancy in Inner Mongolia white cashmere goats

This study investigated the effects of dietary supplementation with N-carbamylglutamate (NCG) on maternal endometrium and fetal development during early pregnancy of Inner Mongolia white cashmere goats. Forty-eight pregnant Inner Mongolia white cashmere goats (average age 3 years old, average lactation parity 2, and average body weight 43.81 ± 2.66 kg) were randomly allocated to three groups: a basal diet (control group, n = 16), a basal diet plus 0.30-g NCG/d (NCG1 group, n = 16), and a basal diet plus 0.40-g NCG/d (NCG2 group, n = 16). All of the does were housed in individual pens and the NCG treatment was conducted from Days 0 to 90 of pregnancy. At Days 17 and 90 of pregnancy, six representative pregnant does in each group were slaughtered. The current study results demonstrated that maternal NCG administration during early pregnancy effectively increased the arginine family of amino acids and the glucogenic amino acids concentrations and promoted the mRNA expression of osteopontin (OPN), αv and β3 integrins, and endometrial development of Inner Mongolia white cashmere goats. The supplementation improved the fetal brown adipose tissue (BAT) stores and the mRNA expression of UCP-1 and BMP7, thereby helping to the fetal early development.

Programming of Embryonic Development

Assisted reproductive techniques (ART) and parental nutritional status have profound effects on embryonic/fetal and placental development, which are probably mediated via "programming" of gene expression, as reflected by changes in their epigenetic landscape. Such epigenetic changes may underlie programming of growth, development, and function of fetal organs later in pregnancy and the offspring postnatally, and potentially lead to long-term changes in organ structure and function in the offspring as adults. This latter concept has been termed developmental origins of health and disease (DOHaD), or simply developmental programming, which has emerged as a major health issue in animals and humans because it is associated with an increased risk of non-communicable diseases in the offspring, including metabolic, behavioral, and reproductive dysfunction. In this review, we will briefly introduce the concept of developmental programming and its relationship to epigenetics. We will then discuss evidence that ART and periconceptual maternal and paternal nutrition may lead to epigenetic alterations very early in pregnancy, and how each pregnancy experiences developmental programming based on signals received by and from the dam. Lastly, we will discuss current research on strategies designed to overcome or minimize the negative consequences or, conversely, to maximize the positive aspects of developmental programming.

Effects of FSH treatment and withdrawal during proestrus on uterine proliferation and steroid hormone receptor expression in beef heifers

To determine the effects of Follicle Stimulating Hormone (FSH) treatment and subsequent withdrawal on uterine proliferation and estrogen receptor (ESR), Brahman crossbred heifers (n = 12) were twice daily injected with FSH (4, 3, and 2 mg/injection) on Days 17-19 of the estrous cycle (FSH 3 days) and (4 and 3 mg/injection) on Days 17-18 (FSH 2 days) and withdrawal with saline on Day 19 and (4 mg/injection) on Day 17 (FSH 1 day) and withdrawal with saline on Days 18-19. Uterine tissue was subjectively collected on Day 20 and microscopically classified to four regions: endometrial stroma (ES), surface endometrial gland (EG), deep endometrial gland (DG), and myometrium (Myo). The cell proliferation marker, Ki-67, was quantified as labeling index (LI) in uterine regions, and tissues were immunostained to detect ESR2 followed by image analysis. The LI of ES, EG, and DG was greater (P = 0.0018, P = 0.0005, and P = 0.0103; respectively) in heifers received FSH for 3 days. The expression of ESR2 protein on ES and EG was greatest (P < 0.0001 and P = 0.0036, respectively) in FSH 3 days-treated group. Thus, FSH administration during proestrus stimulates uterine cell proliferation, and ESR2 expressions are affected by FSH during proestrus and differentially distributed in the uterine regions.

Hepatitis E viral infection regulates estrogen signaling pathways: Inhibition of the cAMPK-PKA-CREB and PI3K-AKT-mTOR signaling pathways

Hepatitis E virus (HEV) infection has become a global concern with high mortality rates among pregnant women, especially those in their third trimester of pregnancy. Estrogen plays an important role in mediating the body, regulating physiological and pathological processes. Estrogen is activated by binding to estrogen receptors (ERs) and mediates rapid signaling events by pathways that involve transmembrane ERs. Our previous study had confirmed that high estrogen levels during pregnancy are associated with high HEV titers. However, the association between HEV infection and estrogen signaling pathways remains unclear. In the present study, the regulation of estrogen signaling pathways by HEV infection was evaluated. Results demonstrated that HEV infection significantly inhibits the cAMP-PKA-CREB and PI3K-AKT-mTOR signaling pathways, but is independent of the Ras-Raf-MEK-ERK signaling pathway. In summary, the increasing estrogen levels and highly activated ERα during pregnancy aggravates HEV replication. The exacerbation of HEV replication, in turn, inhibits ERα expression and suppresses both cAMP-PKA-CREB and PI3K-AKT-mTOR signaling pathways.

Maternal periconceptual nutrition, early pregnancy, and developmental outcomes in beef cattle

The focus of this review is maternal nutrition during the periconceptual period and offspring developmental outcomes in beef cattle, with an emphasis on the first 50 d of gestation, which represents the embryonic period. Animal agriculture in general, and specifically the beef cattle industry, currently faces immense challenges. The world needs to significantly increase its output of animal food products by 2050 and beyond to meet the food security and agricultural sustainability needs of the rapidly growing human population. Consequently, efficient and sustainable approaches to livestock production are essential. Maternal nutritional status is a major factor that leads to developmental programming of offspring outcomes. Developmental programming refers to the influence of pre-and postnatal factors, such as inappropriate maternal nutrition, that affect growth and development and result in long-term consequences for health and productivity of the offspring. In this review, we discuss recent studies in which we and others have addressed the questions, "Is development programmed periconceptually?" and, if so, "Does it matter practically to the offspring in production settings?" The reviewed studies have demonstrated that the periconceptual period is important not only for pregnancy establishment but also may be a critical period during which fetal, placental, and potentially postnatal development and function are programmed. The evidence for fetal and placental programming during the periconceptual period is strong and implies that research efforts to mitigate the negative and foster the positive benefits of developmental programming need to include robust investigative efforts during the periconceptual period to better understand the implications for life-long health and productivity.

Endometrial luminal epithelial cells sense embryo elongation in the roe deer independent of interferon-tau†

Numerous intrauterine changes take place across species during embryo development. Following fertilization in July/August, the European roe deer (Capreolus capreolus) embryo undergoes diapause until embryonic elongation in December/January. Embryonic elongation prior to implantation is a common feature among ungulates. Unlike many other ruminants, the roe deer embryo does not secrete interferon-tau (IFNτ). This provides the unique opportunity to unravel IFNτ-independent signaling pathways associated with maternal recognition of pregnancy (MRP). This study aimed at identifying the cell-type-specific endometrial gene expression changes associated with the MRP at the time of embryo elongation that are independent of IFNτ in roe deer. The messenger RNA (mRNA) expression of genes known to be involved in embryo-maternal communication in cattle, pig, sheep, and mice was analyzed in laser capture microdissected (LMD) endometrial luminal, glandular epithelial, as well as stromal cells. The mRNA transcript abundances of the estrogen (ESR1), progesterone receptor (PGR), and IFNτ-stimulated genes were lower in the luminal epithelium in the presence of an elongated embryo compared to diapause. Retinol Binding Protein-4 (RBP4), a key factor involved in placentation, was more abundant in the luminal epithelium in the presence of an elongated embryo. The progesterone receptor localization was visualized by immunohistochemistry, showing an absence in the luminal epithelium and an overall lower abundance with time and thus prolonged progesterone exposure. Our data show a developmental stage-specific mRNA expression pattern in the luminal epithelium, indicating that these cells sense the presence of an elongated embryo in an IFNτ-independent manner.

Nuclear and membrane progesterone receptors expression in placenta from early to late pregnancy in sheep: Effects of restricted nutrition and realimentation

Nutrient restriction and/or realimentation may affect several placental functions, such as expression of selected regulatory factors, blood flow and other processes in sheep and other species. To determine the effects of the plane of nutrition, nulliparous white face ewes (6-8 months) carrying singletons on day 50 of gestation were randomly assigned to two dietary treatments receiving 100% of National Research Council recommendations (control; C) or 60% of C (restricted; R). Two groups remained on C or R diets from day 50 until day 130. From day 90-130 another group of C fed ewes was switched to the R diet, and another group of R fed ewes was switched to the C diet. This resulted in 7 groups (n = 5-6 ewes/group): C (day 50, 90 and 130), R (day 90 and 130), CR (day 130) and RC (day 130). At these time points, placental tissues were collected for the evaluation of progesterone receptor (PGR) protein expression (whole tissue), and mRNA expression in maternal (caruncular, CAR) and fetal (cotyledon, COT) (separated tissues). Data were statistically analyzed using analysis of variance (SAS 9.4). Protein for PGRAB and PGRB isoforms was detected using immunohistochemistry in all placental tissues, but the pattern of expression differed depending on pregnancy stage and placental compartment (e.g., CAR vs COT). PGRAB protein expression, quantified using image analysis, was greater (P < 0.04) on day 50 than 90 or 130, and was not affected by plane of nutrition. In CAR and COT, PGRAB mRNA expression was greater (P < 0.05) on day 50 than 90 or 130. PGRB mRNA expression was greater (P < 0.03) in CAR on day 50 than 90 and 130, and was greatest (P < 0.02) in COT on day 50, less on day 130, and least on day 90. For the membrane progesterone receptors, PAQR7 (membrane PGR alpha) mRNA expression was greater (P < 0.05) on days 50 and 90 than 130 in CAR, and greater (P < 0.01) on days 50 than 90 and 130 in COT; PAQR8 (membrane PGR beta) was similar throughout pregnancy in CAR and COT, and PAQR5 (membrane PGR gamma) was greatest (P < 0.0001) on day 130 in COT, but similar throughout pregnancy in CAR. Plane of nutrition affected (P < 0.05) mRNA expression for all genes in CAR and COT throughout pregnancy. These data indicate that expression of PGR in ovine placenta is dependent on stage of pregnancy and plane of nutrition in sheep. The mechanisms of how diet and stage of pregnancy influences placental PGR expression and function remains to be elucidated.

Placental development during early pregnancy in sheep: nuclear estrogen and progesterone receptor mRNA expression in the utero-placental compartments

Sex steroid hormones are major regulators of uterine and placental growth and functions, as well as many other biological processes. To examine the mRNA expression of nuclear estrogen (ESR1 and 2) and progesterone (PGRAB and B) receptors in different compartments of the uterus and placenta, tissues were collected in experiment 1 on days 16, 20, and 28 after natural mating (NAT) and on day 10 after estrus (nonpregnant controls [NP]); and in experiment 2 on day 22 of NAT, and pregnancies established after transfer of embryos generated through mating of FSH-treated ewes (NAT-ET), in vitro fertilization (IVF), or in vitro activation (parthenotes). In experiment 1, ESR1 expression in endometrial stroma (ES), endometrial glands (EGs), and myometrial blood vessels (MBVs), ESR2 in endometrial blood vessels (EBV), PGRAB in ES, and PGRB in ES, EG, and MBV was greater in pregnant than NP ewes depending on the day of pregnancy. The day of pregnancy affected the expression of ESR1 in MBV, ESR2 in EBV and MBV, and PGRAB in ES. In experiment 2, ESR1, PGRAB, and PGRB in EG, but not in other compartments, was greater in NAT-ET than NAT, and PGRB was greater for NAT-ET than IVF. These data demonstrate that ESR and PGR expression differ in pregnant versus NP ewes in selected compartments and was affected by pregnancy stage or embryo origin in selected utero-placental compartments. Thus, sex steroid hormone mRNA expression is differentially regulated in a spatiotemporal manner in the uterus and placenta and is affected by the application of assisted reproductive technology in sheep.