'Conceptualizing' the Endometrium: Identification of Conceptus-Derived Proteins During Early Pregnancy in Cattle

Unraveling the elongating bovine conceptus microenvironment: identification of gene transcripts and proteins along the conceptus-maternal interface in cattle†

The bovine conceptus elongates near Day 16 of development and releases interferon-tau, disrupting the endometrial luteolytic mechanism to sustain luteal P4 and pregnancy. Conceptus factors other than interferon tau modify local endometrial activities to support pregnancy; however, the microenvironment is largely uncharacterized. We utilized a bovine conceptus-endometrial culture system to elucidate the microenvironment in the form of gene transcripts and protein. Estrus synchronized heifers remained cyclic (13) or were inseminated (9) to produce Day 16 cyclic endometrium and elongating conceptuses, respectively. Conceptus sections and endometrium were then used to generate tissue cultures in 1 ml of medium: (i) no tissue (control med; n = 7), (ii) mono-cultured conceptus (conceptus; n = 9) (iii) mono-cultured endometrium (endo; n = 13), or (iv) endo-conceptus co-culture (n = 15). After 12 h, tissue gene transcripts were sequenced (RNA-Seq) and media underwent proteomic analysis (LC-MS/MS). Compared to conceptus and endo, co-cultured conceptus and endometrial tissue contained 3400 and 4575 differentially expressed genes, respectively (P ≤ 0.01). More abundantly expressed endometrial differentially expressed genes were associated with interferon signaling whereas more abundantly expressed conceptus differentially expressed genes were associated with protein homeostasis and metabolism (FDR < 0.001). When co-culture media where compared to endo media, 288 more abundant proteins were identified (P < 0.05). Biological processes related to these proteins included antigen presentation via MHC Class Ib and keratinization (FDR < 0.001). Within the mono-cultured conceptus and endometrial media, folate receptor alpha (FOLR1; P < 0.001) was identified as the most abundant secreted protein suggesting the reproductive tissues elicit a microenvironment supportive of conceptus growth involving folate metabolism.

Embryo-Induced Changes in the Protein Profile of Bovine Oviductal Extracellular Vesicles

The study of early maternal-embryonic cross-talk remains one of the most challenging topics in reproductive biology. Understanding the physiological mechanisms involved in the interactions between the maternal reproductive tract and the developing embryo is essential for enhancing bovine reproductive efficiency. This complex communication starts within the oviduct, where the modulation of biological processes important for ensuring embryo quality is partially facilitated through extracellular vesicles (EVs). Utilizing a combination of in vivo and in vitro models this study had three main objectives: 1) to examine the protein cargo of EVs isolated from the oviductal fluid (OF) of cyclic and pregnant heifers to understand their role in maternal-embryonic communication in vivo; 2) to characterize the protein profile of EVs in conditioned medium (CM) resulting from the culture of oviductal explants alone (Exp) or in the presence of 8- to 16-cell stage embryos (Exp + Emb); and 3) to compare the protein cargo of EVs from Exp with EVs from cyclic heifers and EVs from Exp + Emb with EVs from pregnant heifers. Proteins were considered "identified" if detected in at least three out of five replicates and considered "exclusive" if detected in at least three out of five replicates within one group but absent in all samples of other groups. We identified 659 and 1476 proteins in the OF-EVs of cyclic and pregnant heifers, respectively. Among these, 644 proteins were identified in OF-EVs from both cyclic and pregnant heifers, and 40 proteins were exclusive to OF-EVs from the pregnant group. Within the 644 proteins identified in both groups, 31 were identified as differently abundant proteins (DAPs). In pregnant heifers, DAPs were mainly related to genome activation, DNA repair, embryonic cell differentiation, migration, and immune tolerance. In vitro, we identified 841 proteins in the CM-EVs from Exp alone, 613 from Exp + Emb, and 111 in the CM-EVs from Emb alone. In the qualitative analysis between the three in vitro groups, 81 proteins were identified in all groups, 452 were common to Exp and Exp + Emb, 17 were common to Exp and Emb, 5 were common to Exp + Emb and Emb, 4 were unique to Exp, 6 were unique to Exp + Emb, and none were unique to Emb. Proteins identified when there is an interaction between the oviduct and the embryo in vitro, corresponding to the Exp + Emb group, were associated with immune tolerance, structural activity, binding, and cytoskeletal regulation. In vivo and in vitro EVs exhibit distinct qualitative and quantitative protein contents, both when comparing EVs produced in the absence of an embryo (Cyclic and Exp) and those that have undergone embryo-oviduct interaction (Pregnant and Exp + Emb). The observed changes in the protein cargo of EVs due to maternal-embryonic communication in vivo and in vitro suggest that the interaction between the embryo and the maternal milieu initiates within the oviduct and is potentially facilitated by EVs and their protein contents.

Small extracellular vesicles derived from the crosstalk between early embryos and the endometrium potentially mediate corpus luteum function†

The first interactions among the embryo, endometrium, and corpus luteum are essential for pregnancy success. Small extracellular vesicles (sEVs) are part of these interactions. We previously demonstrated that small extracellular vesicles from in vivo- or in vitro-produced bovine embryos contain different miRNA cargos. Herein we show: (1) the presence and origin (in vivo or in vitro) of the blastocyst differentially reprograms endometrial transcriptional profiles; (2) the endometrial explant (EE) cultured with in vivo or in vitro embryos release small extracellular vesicles with different miRNA contents, and (3) the luteal explant (CLE) exposed to these small extracellular vesicles have distinct mRNA and miRNA profiles. To elucidate this, the endometrial explant were cultured in the presence or absence of a single Day-7 in vivo (EE-artificial insemination; EE-AI) or in vitro (EE-in vitro fertilization; EE-IVF) embryo. After of culture we found, in the endometrial explant, 45 and 211 differentially expressed genes associated with embryo presence and origin, respectively. Small extracellular vesicles were recovered from the conditioned media (CM) in which endometrial explant and embryos were co-cultured. Four miRNAs were differentially expressed between small extracellular vesicles from CC-EE-AI and CC-EE-IVF. Luteal explants exposed in culture to these small extracellular vesicles showed 1360 transcripts and 15 miRNAs differentially expressed. The differentially expressed genes associated with embryo presence and origin, modulating cells' proliferation, and survival. These results demonstrate that in vivo- or in vitro-produced bovine embryos induce molecular alterations in the endometrium; and that the embryo and endometrium release small extracellular vesicles capable of modifying the messenger RNA (mRNA) and miRNA profile in the corpus luteum. Therefore, the small extracellular vesicles-mediated embryo-endometrium-corpus luteum interactions possibly regulate the corpus luteum viability to ensure pregnancy success.

Research Progress on the Impact of Human Chorionic Gonadotropin on Reproductive Performance in Sows

Human chorionic gonadotropin is a glycoprotein hormone produced by human or humanoid syncytiotrophoblasts that differentiate during pregnancy. Due to its superior stability and long-lasting effects compared to luteinizing hormone, it is often used to replace luteinizing hormone to regulate reproductive performance in sows. Human chorionic gonadotropin promotes oocyte maturation, follicle development, and luteinization, thereby increasing conception rates and supporting early embryonic development. In sow reproductive management, the application of human chorionic gonadotropin not only enhances ovulation synchrony but also improves the success rate of embryo implantation by regulating endometrial receptivity and immune mechanisms, significantly enhancing overall reproductive performance. This article primarily reviews the application of human chorionic gonadotropin in sow follicle development, luteal maintenance, and embryo implantation, providing theoretical support for its use in improving reproductive performance in sows.

In vitro reminiscence: uterine programming in vivo affects respective luminal epithelial cells function in vitro†

In cattle, the endometrium during diestrus and early pregnancy displays cellular responses that are consequences of prior, transient stimuli. Goal was to establish a model to study cellular memory in the endometrium. The hypothesis is that stimuli given to endometrium in vivo are retained as a cellular memory that remains after bovine uterine epithelial cells (BUECs) are isolated, cultured, and further stimulated in vitro. Objectives were to measure BUEC proliferation/migration and responsiveness to recombinant bovine Interferon-tau (rbIFNT) in vitro: among cows that showed estrus (experiment 1 [Exp1]), cows that became or not pregnant to artificial insemination (Exp2), cows that received or not supplemental progesterone (P4; Exp3) and cows that received or not a COX-1/2 inhibitor (Exp4). Only cows that displayed estrus were included in studies. For all experiments endometrial cytology was collected 4 days after estrus, BUECs were cultured, propagated, and submitted to rbIFNT treatment and an in vitro scratch assay. In Exp1, different cows spontaneously grouped according to proliferative/migratory capacity and responsiveness to rbIFNT of their respective BUECs. In Exp2, BUECs from pregnant cows showed greater rbIFNT responsiveness and cellular proliferation. In Exp3, BUECs from cows supplemented with P4 presented inhibited proliferation and increased expression of RSAD2. In Exp4, Flunixin Meglumine modified rbIFNT responsiveness of BUECs in an IFN-signaling pathway-specific manner. In conclusion, physiological and pharmacological stimuli received by the endometrium in vivo were retained as cellular memory in BUECs, persisted in culture, and changed BUEC proliferation/migration and responsiveness to rbIFNT, which are characteristics associated with fertility in cattle.

Biosensor capability of the endometrium is mediated in part, by altered miRNA cargo from conceptus-derived extracellular vesicles

We tested the hypothesis that the biosensor capability of the endometrium is mediated in part, by the effect of different cargo contained in the extracellular vesicles secreted by the conceptus during the peri-implantation period of pregnancy. We transferred Bos taurus taurus embryos of different origin, in vivo (high developmental potential (IV)), in vitro (intermediate developmental potential (IVF)), or cloned (low developmental potential (NT)), into Bos taurus indicus recipients. Extracellular vesicles (EVs) recovered from Day 16 conceptus-conditioned medium were characterized and their microRNA (miRNA) cargo sequenced alongside RNA sequencing of their respective endometria. There were substantial differences in the endometrial response to in vivo versus in vitro and in vivo versus cloned conceptuses (1153 and 334DEGs respectively) with limited differences between in vitro Vs cloned conceptuses (36 DEGs). The miRNA cargo contained in conceptus-derived EVs was similar between all three groups (426 miRNA in common). Only 8 miRNAs were different between in vivo and cloned conceptuses, while only 6 miRNAs were different between in vivo and in vitro-derived conceptuses. Treatment of endometrial epithelial cells with mimic or inhibitors for miR-128 and miR-1298 changed the proteomic content of target cells (96 and 85, respectively) of which mRNAs are altered in the endometrium in vivo (PLXDC2, COPG1, HSPA12A, MCM5, TBL1XR1, and TTF). In conclusion, we have determined that the biosensor capability of the endometrium is mediated in part, by its response to different EVs miRNA cargo produced by the conceptus during the peri-implantation period of pregnancy.

TMT-based quantitative proteomic analysis unveils uterine fluid difference in hens producing normal and pimpled eggs

Eggshell is a crucial indicator of egg quality. Pimpled eggs (PE) a type of eggshell defect are characterized by low eggshell strength, leading to substantial financial losses. Eggshell formation occurs in the uterine fluid (UF), which contains the required ions and matrix proteins However, the underlying mechanisms of PE formation remain poorly understood. In this study, we analyzed the egg quality of PE, and normal eggs (NE) by examining the differences in UF from hens producing PE and NE (n = 6 each). This 2-wk-long assessment involved histomorphological and proteomics analyses. The results showed that NE had better eggshell quality compared to PE, and the uterus structure in PE hens was conducive to the formation of PE. Using quantitative proteomic analysis, we identified 68 differential abundance proteins (DAPs) in the UF of PE hens, including 9 key proteins related to ion transport, protein synthesis and folding, and immunity. Downregulation of CALM1 and SCNN1G proteins in PE hens might have negatively affected the calcium signaling pathway, decreasing the calcium amount in UF. Additionally, the PHB1 and TSN proteins may affect eggshell formation by regulating immune responses. Taken together, our results provide insights into the mechanism of PE production, with potential applications for enhancing eggshell quality.

β-Hydroxybutyrate Effects on Bovine Caruncular Epithelial Cells: A Model for Investigating the Peri-Implantation Period Disruption in Ketotic Dairy Cows

Ketosis is a metabolic disorder arising from a negative energy balance (NEB). It is characterized by high β-Hydroxybutyrate (BHBA) blood levels and associated with reduced fertility in dairy cows. To investigate the impact of BHBA on bovine caruncular epithelial cells (BCEC) in vitro, these cells were stimulated with different concentrations of BHBA. Cell metabolism and motility were examined using an MTT assay and Live-cell imaging. RT-qPCR was used to examine mRNA expressions of TNF, IL6, RELA, prostaglandin E2 synthase (PTGES2) and receptor (PTGER2) as well as integrin subunits ITGAV, ITGA6, ITGB1 and ITGB3. Stimulation with 1.8 and 2.4 mM of BHBA negatively affected cell metabolism and motility. TNF showed increased mRNA expression related to rising BHBA concentrations. IL6, RELA, ITGAV, ITGA6, ITGB1 and ITGB3 as well as PTGER2 showed no changes in mRNA expression. Stimulation with 0.6 and 1.2 mM of BHBA significantly increased the mRNA expression of PTGES2. This does not indicate a negative effect on reproductive performance because low BHBA concentrations are found in steady-state conditions. However, the results of the study show negative effects of high BHBA concentrations on the function of BCECs as well as an inflammatory response. This could negatively affect the feto-maternal communication during the peri-implantation period in ketotic dairy cows.

Interferon-Stimulated Gene Expression in Peripheral Blood Leucocytes as a Convenient Prediction Marker for Embryo Status in Embryo-Transferred Japanese Black Cows during the Peri-Implantation Period

Pregnancy diagnosis during early gestation is important for cattle reproduction. The expression of interferon-stimulated genes (ISGs) in peripheral blood leukocytes (PBLs) was studied in embryo-transferred (ET) Japanese Black cattle. ISGs in PBLs-ISG15, MX1, MX2, and OAS1-were detected in multiple ovulation ET cattle using a real-time quantitative polymerase chain reaction, and receiver operating characteristic (ROC) curve analysis was performed. Gestational status was predicted using the average ISG levels during the normal estrous cycle (AVE) and the Youden index from the ROC curve analysis as cutoff values. The ISG15, MX1, and MX2 levels were significantly higher in pregnant cattle (n = 10) than in non-pregnant cattle (n = 23) on gestation day 21, whereas the levels of all ISGs were similar between non-pregnant and non-pregnant cattle with late embryonic death (n = 7). ISG15, MX1, and MX2 appropriately predicted the gestational status of ET cows. The statistical evaluation of the diagnostic accuracy in ET cows on day 21 of gestation presented higher values of sensitivity, specificity, accuracy, and positive predictive values of ISG15, MX1, and MX2 using the Youden index than using the AVE. Therefore, ISG15, MX1, and MX2 are excellent biomarkers of gestational status during the peri-implantation period in ET cattle.

Review: Endometrial function in pregnancy establishment in cattle

The endometrium is fundamentally required for successful pregnancy in ruminants and species where the posthatching conceptus undergoes a protracted elongation and peri-implantation phase of pregnancy. Moreover, there are substantial waves of pregnancy loss during this pre- and peri-implantation period of pregnancy the precise source of which has not been clearly defined i.e., the maternal uterine contribution to this loss. Understanding the molecular interactions required for successful pregnancy in cattle will allow us to intervene to support pregnancy success during this vulnerable window. The endometrium contributes to most key developmental milestones of pregnancy establishment, including (1) contributing to the regulation of the oestrus cycle, (2) nourishing the preimplantation conceptus, (3) responding to the conceptus to create a more receptive microenvironment, (4) providing essential biophysical support, and (5) signalling and producing factors which affect the mother systemically. This review will summarise what we currently know about conceptus-maternal interactions as well as identify the gaps in our knowledge that could be filled with newer in vitro model approaches. These include the use of microfluidics, organ-on-a-chip devices, and bioinformatic approaches. This will help maximise food production efficiency (both meat and dairy) and decrease the environmental burden, while enhancing our understanding of the fundamental processes required for successful implantation in cattle.

Comparative Proteome Analysis of Serum Uncovers Differential Expression of Proteins in Donkeys (Equus Asinus) With Endometritis Caused by Escherichia Coli

Endometritis is a common disease in donkeys that causes economic losses to donkey farms and the common cause is bacterial infection. Uterine flush fluid proteomics has been used to study protein biomarkers associated with endometritis in mares. As a convenient diagnostic tool, serum proteomics has not been studied yet in equine species with endometritis. This study is aiming to evaluate the serum proteomics in jennies with and without endometritis and identify potential proteins as biomarker for endometritis diagnosis. Nine donkeys recruited into this study were diagnosed of bacterial (Escherichia coli) endometritis and nine healthy jennies were selected as control. Blood samples of each donkey was collected, and serum was separated from each sample. Peptides samples extracted from the serum were analyzed using nano-ultrahigh-performance liquid chromatography-tandem mass spectrometry in data-independent acquisition mode. Protein identification and quantification were performed followed by differential and functional analysis. Of 579 proteins identified in all jennies, 12 proteins were exclusively identified in jennies with endometritis (group E) including myeloperoxidase and Ras-related protein Rab-1B, which might be associated with bacterial infection. There were 11 differentially expressed proteins detected between the two groups of jennies with 4 downregulated proteins and 7 upregulated proteins in jennies with endometritis. Some upregulated proteins along with the GO and KEGG annotation indicated inflammatory response against uterine infection. Characteristic serum proteins identified in jennies with endometritis were associated with inflammation or bacterial infection. These proteins might be potential biomarkers for endometritis diagnosis in jennies.

Expression and Regulation of a Novel Decidual Cells-Derived Estrogen Target during Decidualization

During decidualization in rodents, uterine stromal cells undergo extensive reprogramming to differentiate into distinct cell types, forming primary decidual zones (PDZs), secondary decidual zones (SDZs), and layers of undifferentiated stromal cells. The formation of secondary decidual zones is accompanied by extensive angiogenesis. During early pregnancy, besides ovarian estrogen, de novo synthesis of estrogen in the uterus is essential for the progress of decidualization. However, the molecular mechanisms are not fully understood. Studies have shown that Cystatin B (Cstb) is highly expressed in the decidual tissue of the uterus, but the regulation and mechanism of Cstb in the process of decidualization have not been reported. Our results showed that Cstb was highly expressed in mouse decidua and artificially induced deciduoma via in situ hybridization and immunofluorescence. Estrogen stimulates the expression of Cstb through the Estrogen receptor (ER)α. Moreover, in situ synthesis of estrogen in the uterus during decidualization regulates the expression of Cstb. Silencing the expression of Cstb affects the migration ability of stromal cells. Knockdown Cstb by siRNA significantly inhibits the expression of Dtprp, a marker for mouse decidualization. Our study identifies a novel estrogen target, Cstb, during decidualization and reveals that Cstb may play a pivotal role in angiogenesis during mouse decidualization via the Angptl7.

Influence of sire fertility status on conceptus-induced transcriptomic response of the bovine endometrium

The aim was to examine the effect of sire fertility status on conceptus-induced changes in the bovine endometrial transcriptome. To generate elongated conceptuses, Day 7 blastocysts produced in vitro using frozen-thawed sperm from Holstein Friesian bulls (3 High fertility, HF and 3 Low fertility, LF) were transferred in groups of 5–10 into synchronized heifers (n = 7 heifers per bull) and recovered following slaughter on Day 15. Day 15 endometrial explants recovered from the uterine horn ipsilateral to the corpus luteum were recovered from synchronized cyclic heifers (n = 4). Explants from each heifer were co-cultured for 6 h in RPMI medium alone (Control) or with 100 ng/ml ovine recombinant interferon tau (IFNT) or with a single conceptus from each HF or LF bull. After 6 h, explants were snap frozen and stored at −80°C. Extracted mRNA was subjected to RNA-seq and the resulting data were analyzed with R software. The numbers of differentially expressed genes (DEG; FDR&lt;0.05) were: HF vs. Control: 956; LF vs. Control: 1021; IFNT vs. Control: 1301; HF vs. LF: 2. Unsurprisingly, the majority of DEG (658) were common to all comparisons and were related to IFNT-induced changes in the endometrium. Prior to applying the adjusted p-value, there were 700 DEG between HF and LF, with 191 and 509 genes more expressed in HF or LF, respectively (p &lt; 0.05). Overrepresentation analysis of KEGG pathways (FDR&lt;0.05), revealed that DEG with higher expression in LF were involved in cell cycle and proteolysis, while those upregulated DEG by HF conceptuses were strongly associated with immune process pathways, such as TNF, NF-kappa B, cytokine-cytokine receptor interaction, and TLR signaling. These pathways were also enriched by DEG upregulated by IFNT compared to the Control. Furthermore, only the HF, and not the LF group, affected the expression of most genes in these pathways (p &lt; 0.05) according to a negative binomial regression model. Finally, a weighted gene co-expression network analysis revealed two clusters of co-expressed genes associated with the HF conceptuses (p &lt; 0.05), which were also enriched for the aforementioned pathways. In conclusion, HF conceptuses, similar to IFNT treatment, stimulated multiple pathways involved in immune response, which were apparently not affected by LF conceptuses.

Intrauterine infusion of low levels of interferon-tau on day-8 post-estrus stimulates the bovine endometrium to secrete apolipoprotein-A1: A possible implication for early embryo tolerance

We previously reported that interferon-tau (IFNT), derived from day-7 blastocyst, generates anti-inflammatory responses in bovine endometrial epithelial cells (BEECs) in vitro. However, the real in vivo impact of early embryo-derived IFNT on the uterine proteomic profile is mostly unknown. This study aimed to investigate proteomic changes of uterine flush (UF) when infused with a low physiological level of IFNT without embryo on day-8 post-estrus and its possible impact on the uterine immunological microenvironment. First, a fresh medium was infused into the uterine lumen on day-6, from which UF was obtained 24 h later, and this procedure was repeated on day-7 (control UF). On day-8, this procedure was done with a medium containing recombinant bovine IFNT (100 pg/ml) (IFNT-supplemented UF). Control and IFNT-supplemented UF were tested for immune responses in peripheral blood mononuclear cells (PBMCs). Real-time PCR results revealed that IFNT-supplemented UF downregulated pro-inflammatory cytokines (TNFA, IL1B) and upregulated anti-inflammatory cytokine (TGFB1) and PTGES in PBMCs. Through 2-D PAGE, followed by TOF/TOF mass spectrometer, apolipoprotein-A1 (Apo-A1) protein was identified in the IFNT-supplemented UF, which was confirmed by ELISA analysis. Proteomic analysis revealed again that the in vitro stimulation of BEECs by IFNT upregulated Apo-A1 expression. Further, stimulation of PBMCs with recombinant bovine Apo-A1 downregulated TNFA and NFKB and upregulated TGFB1 and PTGES in PBMCs. Altogether, our results suggest that minute amounts of IFNT alone, normally secreted from bovine blastocyst, stimulate Apo-A1 secretion from the endometrial epithelium in the absence of embryo that initiates an anti-inflammatory environment, which could pave the way for the acceptance of early embryo in the uterus. This article is protected by copyright. All rights reserved.

Ruminant conceptus-maternal interactions: interferon-tau and beyond

Embryonic or fetal loss in cattle is associated with problems that occur during oocyte maturation, early embryonic development, conceptus elongation, maternal recognition of pregnancy (MRP), and/or placental attachment and implantation. Many of these problems manifest as inadequate or asynchronous communication between the developing conceptus and endometrium, resulting in pregnancy failure. This review will provide an overview of how various conceptus-endometrial paracrine signaling systems control the fate of early pregnancy in cattle and other ruminants. We begin by summarizing the actions of interferon-tau, the classic MRP signal in ruminates, and then explore how other secretory factors derived from either the conceptus or endometrium influence establishment and maintenance of pregnancy. Insight into how the endometrium responds to male vs. female conceptuses or conceptuses produced by in vitro methods will also be described. Specific focus will be placed on describing how "omic" technologies and other cutting-edge techniques have assisted with identifying novel conceptus and/or endometrial factors and their functions. Recent findings indicate that the endometrial transcriptome and histotroph are altered by conceptus sex, quality, and origin, suggesting that the endometrium is a sensor of conceptus biochemistry. Although the endometrium has a certain level of flexibility in terms of conceptus-maternal interactions, this interplay is not sufficient to retain some pregnancies. However, new information inspires us to learn more and will help develop technologies that mitigate early embryonic loss and reproductive failure in ruminants and other animals.

Uterine lumen fluid is metabolically semi-autonomous

Uterine lumen fluid (ULF) is central to successful pregnancy establishment and maintenance, and impacts offspring wellbeing into adulthood. The current dogma is that ULF composition is primarily governed by endometrial glandular epithelial cell secretions and influenced by progesterone. To investigate the hypothesis that ULF is metabolically semi-autonomous, ULF was obtained from cyclic heifers, and aliquots incubated for various durations prior to analysis by untargeted semi-quantitative metabolomic profiling. Metabolite flux was observed in these ULF isolates, supporting the idea that the biochemical makeup of ULF is semi-autonomously dynamic due to enzyme activities. Subsequent integrative analyses of these, and existing, data predict the specific reactions underpinning this phenomenon. These findings enhance our understanding of the mechanisms leading to pregnancy establishment, with implications for improving fertility and pregnancy outcomes in domestic animals as well as women.

Characterization of lncRNA functioning in ovine conceptuses and endometria during the peri-implantation period

In ruminants, RNA-sequence analyses have revealed many characteristics of transcripts expressed in conceptuses (embryo and extraembryonic membrane) during peri-implantation periods; however, lncRNA profiles are yet characterized. In this study, we aimed to characterize the lncRNA expression profile in conceptuses during peri-implantation periods in sheep. We analyzed the RNA-sequence data of ovine conceptuses and endometria obtained from pregnant animals on days 15, 17, 19 and 21 (day 0 = day of estrus, n = 3 or 4/day). We predicted the protein coding ability of the assembled transcripts to identify the lncRNA candidates. This analysis identified 8808 lncRNAs, 3423 of which were novel lncRNAs. Gene ontology analysis revealed that lncRNA target genes were enriched for biological processes involved in the respiratory electron transport chain (RETC). qPCR analysis demonstrated that the expression levels on transcripts encoding RETC such as mitochondrially encoded cytochrome c oxidase II (MTCO2) and mitochondria DNA copy number in conceptuses were not increased on P21, although western blotting analysis and immunohistochemistry demonstrated that MTCO2 protein in conceptuses was increased on P21. NAD/NADH assay revealed that NADH level in conceptuses was increased on P21. These results indicate that lncRNAs could regulate the RETC through post-transcriptional levels in the conceptuses. Therefore, lncRNA is a potential new regulator in ovine conceptus development during peri-implantation periods.

The Role of Extracellular Vesicles in Embryo Implantation

Extracellular vesicles (EVs) are membrane-coating nanoparticles derived from cells. The effect of cell-to-cell communication mediated by EVs has been investigated in different fields of physio-logical as well as pathological process in recent years. Reproduction, regarded as a definitive characteristic of organisms, has been a focus in both animal and medical sciences. It is well agreed that implantation is a critical event during early pregnancy in viviparous animals, and a proper implantation is essential for the establishment and maintenance of normal pregnancy. However, successful implantation requires the synchronized development of both the uterus and the embryo, therefore, in which well communication and opportune regulation are necessary. This review focuses on the progression of studies that reveal the role of EVs in early pregnancy, especially during implantation. Based on current evidence, EVs are produced and exist in the environment for implantation. It has been proved that EVs of different origins such as endometrium and embryo, have positive influences on embryo implantation. With their cargos of proteins and nucleic acids (especially microRNAs), EVs exert their effects including information transportation, immune stimulation and regulation of gene expression.

The Lifestyle Modifications and Endometrial Proteome Changes of Women With Polycystic Ovary Syndrome and Obesity

Polycystic ovary syndrome (PCOS) is a polyendocrine disorder and the most common endocrinopathy in women of reproductive age. Affected women have an elevated prevalence of being overweight and obese. Our study sought to determine how weight loss associated with lifestyle changes affects the endometrium specific proteome, endocrine-metabolic characteristics, and motor capabilities of obese women with PCOS and infertility. A group of 12 infertile women under the age of 38 with PCOS and BMI ≥30 kg/m² were included in the study. An evaluation was performed by a gynecologist and an endocrinologist. The weight-loss program lasted 8 weeks under the guidance of a professional trainer. Endometrial sampling during a period of implantation window for proteome determination was performed before and after weight loss. In endometrial samples at the end of the study increased protein abundance was recorded for Legumain, Insulin-like growth factor-binding protein 7, Hepatocyte growth factor receptor, Keratin, type II cytoskeletal 7, and Cystatin-B, while the B-lymphocyte antigen CD20 protein abundance decreased. Our results also indicate significantly lowered fasting blood glucose level and free testosterone concentration and significant improvements in body composition and physical capacity. This study may open up the venues for investigating important biomarkers that may affect endometrial receptivity.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT04989244?term=NCT04989244&draw=2&rank=1, identifier: NCT04989244.

Galectin-1 Confers Endometrial Gene Expression and Protein Related to Maternal-Conceptus Immune Tolerance in Cattle

Conceptus secretory factors include galectins, a family of carbohydrate binding proteins that elicit cell adhesion and immune suppression by interacting with intracellular and extracellular glycans. In rodents, galectin-1 (LGALS1) promotes maternal-fetal immune tolerance in the decidua through expansion of tolerogenic CD11c+ dendritic cells, increased anti-inflammatory IL-10, and activation of FOXP3+ regulatory T cells (Treg). This study characterized galectin expression in early ruminant conceptuses and endometrium. We also tested the effect of recombinant bovine LGALS1 (rbLGALS1) and progesterone (P4) on endometrial expression of genes and protein related to maternal-fetal immune tolerance in cattle. Elongating bovine and ovine conceptuses expressed several galectins, particularly, LGALS1, LGALS3 and LGALS8. Within bovine endometrium, expression of LGALS3, LGALS7 and LGALS9 was greater on Day 16 of pregnancy compared to the estrous cycle. Within ovine endometrium, LGALS7 was greater during pregnancy compared to the estrous cycle and endometrium of pregnant sheep tended to have greater LGALS9 and LGALS15. Expression of endometrial LGALS4 was less during pregnancy in sheep. Treating bovine endometrium with rbLGALS1 increased endometrial expression of CD11c, IL-10 and FOXP3, within 24 h. Specifically, within caruncular endometrium, both rbLGALS1 and P4 increased FOXP3, suggesting that both ligands may promote Treg expansion. Using IHC, FOXP3+ cells with a leukocyte phenotype were localized to the bovine uterine stratum compactum near the uterine surface and increased in response to rbLGALS1. We hypothesize that galectins have important functions during establishment of pregnancy in ruminants and bovine conceptus LGALS1 and luteal P4 confer mechanisms of maternal-conceptus immune tolerance in cattle.

Proteomic determinants of uterine receptivity for pregnancy in early and mid-postpartum dairy cows†

Dairy cow subfertility is a worldwide issue arising from multiple factors. It manifests in >30% early pregnancy losses in seasonal pasture-grazed herds, especially when cows are inseminated in the early post-partum period. Most losses occur before implantation, when embryo growth depends on factors present in maternal tract fluids. Here we examined the proteomic composition of early and mid-postpartum uterine luminal fluid in crossbred lactating dairy cows to identify molecular determinants of fertility. We also explored changes in uterine luminal fluid from first to third estrus cycles postpartum in individual cows, linking those changes with divergent embryo development. For this, we flushed uteri of 87 cows at day 7 of pregnancy at first and third estrus postpartum, recovering and grading their embryos. Out of 1563 proteins detected, 472 had not been previously reported in this fluid, and 408 were predicted to be actively secreted by bioinformatic analysis. The abundance of 18 proteins with roles in immune regulation and metabolic function (e.g. cystatin B, pyruvate kinase M2) was associated with contrasting embryo quality. Matched-paired pathway analysis indicated that, from first to third estrus postpartum, upregulation of metabolic (e.g. creatine and carbohydrate) and immune (e.g. complement regulation, antiviral defense) processes were related to poorer quality embryos in the third estrus cycle postpartum. Conversely, upregulated signal transduction and protein trafficking appeared related to improved embryo quality in third estrus. These results advance the characterization of the molecular environment of bovine uterine luminal fluid and may aid understanding fertility issues in other mammals, including humans.

Steroidal but not embryonic regulation of mucin 1 expression in bovine endometrium

In cow herd management, inadequate embryo implantation leads to pregnancy loss and causes severe economic losses. Thus, it is crucial to understand the molecular mechanisms underlying endometrial receptivity and subsequent embryo implantation. Transmembrane glycocalyx mucin 1 (MUC1) has a large and highly glycosylated extracellular domain known to inhibit embryo implantation via steric hindrance. The role of MUC1 in the bovine endometrium remains to be explored. Herein, we used simple but reliable in vivo and in vitro experiments to investigate the expression and regulation of MUC1 in the bovine endometrium. MUC1 gene expression was analyzed in endometrial epithelial cells collected by the cytobrush technique using reverse transcription-quantitative polymerase chain reaction. MUC1 protein expression was evaluated by immunohistochemical analysis of endometrial samples collected from slaughtered cows. We used an in vitro cell culture model to study the regulation of MUC1 expression by treating cells with sex steroidal hormones or co-culturing cells with a blastocyst. The results revealed that MUC1 was expressed and localized to the apical surface of luminal epithelial cells in the bovine endometrium. MUC1 expression disappeared during the luteal phase of the estrous cycle and during pregnancy. 17β-estradiol induced MUC1 expression, whereas progesterone inhibited its increase and co-culturing with blastocysts did not affect the expression. A long postpartum interval is a known risk factor for reduced fertility, and MUC1 expression was higher in this compromised condition. Our results demonstrated the MUC1 regulation by steroid hormones in bovine endometrium for embryo implantation, and we observed a negative correlation between MUC1 expression and fertility.

Combined approaches identify known and novel genes associated with sheep litter size and non-seasonal breeding

Improvement of ewe reproduction is considerable by appropriately increasing litter size and sustaining non-seasonal breeding. However, their genetic makeups have not been entirely elucidated. Genome-wide analyses of 821 individuals were performed by combining three genomic approaches (genome-wide association study, XP-nSL, and runs of homozygosity). Consequently, 35 candidate genes including three domestication genes (TSHR, GTF2A1, and KITLG) were identified. Other than the FecB mutation at BMPR1B, we described a significant association of a missense mutation rs406686139 at seasonal lambing-associated TSHR gene with litter size. Some promising novel genes may be relevant for sheep reproduction by multitude biological processes, such as FETUB functioning in fertilization, HNRNPA1 in oogenesis, DCUN1D1 in spermatogenesis, and HRG in fertility outcome. The present study suggests that improvement of ewe reproduction is attributed to selective breeding, and casts light on the genetic basis and improvement of sheep reproduction.

Detection of selection signatures in the genome of a farmed population of anadromous rainbow trout (Oncorhynchus mykiss)

Domestication processes and artificial selection are likely to leave signatures that can be detected at a molecular level in farmed rainbow trout (Oncorhynchus mykiss). These signatures of selection are genomic regions that contain functional genetic variants conferring a higher fitness to their bearers. We genotyped 749 rainbow trout from a commercial population using a rainbow trout Axiom 57 K SNP array panel and identified putative genomic regions under selection using the pcadapt, Composite Likelihood Ratio (CLR) and Integrated Haplotype Score (iHS) methods. After applying quality-control pipelines and statistical analyses, we detected 12, 96 and 16 SNPs putatively under selection, associated with 96, 781 and 115 candidate genes, respectively. Several of these candidate genes were associated with growth, early development, reproduction, behavior and immune system traits. In addition, some of the SNPs were found in interesting regions located in autosomal inversions on Omy05 and Omy20. These findings could represent a genome-wide map of selection signatures in farmed rainbow trout and could be important in explaining domestication and selection for genetic traits of commercial interest.

Molecular Characterisation of Uterine Endometrial Proteins during Early Stages of Pregnancy in Pigs by MALDI TOF/TOF

The molecular mechanism underlying embryonic implantation is vital to understand the correct communications between endometrium and developing conceptus during early stages of pregnancy. This study’s objective was to determine molecular changes in the uterine endometrial proteome during the preimplantation and peri-implantation between 9 days (9D), 12 days (12D), and 16 days (16D) of pregnant Polish Large White (PLW) gilts. 2DE-MALDI-TOF/TOF and ClueGO^TM approaches were employed to analyse the biological networks and molecular changes in porcine endometrial proteome during maternal recognition of pregnancy. A total of sixteen differentially expressed proteins (DEPs) were identified using 2-DE gels and MALDI-TOF/TOF mass spectrometry. Comparison between 9D and 12D of pregnancy identified APOA1, CAPZB, LDHB, CCT5, ANXA4, CFB, TTR upregulated DEPs, and ANXA5, SMS downregulated DEPs. Comparison between 9D and 16D of pregnancy identified HP, APOA1, ACTB, CCT5, ANXA4, CFB upregulated DEPs and ANXA5, SMS, LDHB, ACTR3, HP, ENO3, OAT downregulated DEPs. However, a comparison between 12D and 16D of pregnancy identified HP, ACTB upregulated DEPs, and CRYM, ANXA4, ANXA5, CAPZB, LDHB, ACTR3, CCT5, ENO3, OAT, TTR down-regulated DEPs. Outcomes of this study revealed key proteins and their interactions with metabolic pathways involved in the recognition and establishment of early pregnancy in PLW gilts.

Embryonic Trophectoderm Secretomics Reveals Chemotactic Migration and Intercellular Communication of Endometrial and Circulating MSCs in Embryonic Implantation

Embryonic implantation is a key step in the establishment of pregnancy. In the present work, we have carried out an in-depth proteomic analysis of the secretome (extracellular vesicles and soluble proteins) of two bovine blastocysts embryonic trophectoderm primary cultures (BBT), confirming different epithelial–mesenchymal transition stages in these cells. BBT-secretomes contain early pregnancy-related proteins and angiogenic proteins both as cargo in EVs and the soluble fraction. We have demonstrated the functional transfer of protein-containing secretome between embryonic trophectoderm and maternal MSC in vitro using two BBT primary cultures eight endometrial MSC (eMSC) and five peripheral blood MSC (pbMSC) lines. We observed that eMSC and pbMSC chemotax to both the soluble fraction and EVs of the BBT secretome. In addition, in a complementary direction, we found that the pattern of expression of implantation proteins in BBT-EVs changes depending on: (i) their epithelial–mesenchymal phenotype; (ii) as a result of the uptake of eMSC- or pbMSC-EV previously stimulated or not with embryonic signals (IFN-τ); (iii) because of the stimulation with the endometrial cytokines present in the uterine fluid in the peri-implantation period.

Influence of estradiol on bovine trophectoderm and uterine gene transcripts around maternal recognition of pregnancy†

Embryo survival and pregnancy success is increased among animals that exhibit estrus prior to fixed time-artificial insemination, but there are no differences in conceptus survival to d16. The objective of this study was to determine effects of preovulatory estradiol on uterine transcriptomes, select trophectoderm (TE) transcripts, and uterine luminal fluid proteins. Beef cows/heifers were synchronized, artificially inseminated (d0), and grouped into either high (highE2) or low (lowE2) preovulatory estradiol. Uteri were flushed (d16); conceptuses and endometrial biopsies (n = 29) were collected. RNA sequencing was performed on endometrium. Real-time polymerase chain reaction (RT-PCR) was performed on TE (n = 21) RNA to measure relative abundance of IFNT, PTGS2, TM4SF1, C3, FGFR2, and GAPDH. Uterine fluid was analyzed using 2D Liquid Chromatography with tandem mass spectrometry-based Isobaric tags for relative and absolute quantitation (iTRAQ) method. RT-PCR data were analyzed using the MIXED procedure in SAS. There were no differences in messenger RNA (mRNA) abundances in TE, but there were 432 differentially expressed genes (253 downregulated, 179 upregulated) in highE2/conceptus versus lowE2/conceptus groups. There were also 48 differentially expressed proteins (19 upregulated, 29 downregulated); 6 of these were differentially expressed (FDR < 0.10) at the mRNA level. Similar pathways for mRNA and proteins included: calcium signaling, protein kinase A signaling, and corticotropin-releasing hormone signaling. These differences in uterine function may be preparing the conceptus for improved likelihood of survival after d16 among highE2 animals.

Local action of cytokines and immune cells in communication between the conceptus and uterus during the critical period of early embryo development, attachment and implantation - Implications for embryo survival in cattle: A review

Early embryo development, implantation and pregnancy involve a complex dialogue between the embryo and mother. In cattle this dialogue starts as early as days 3-4 when the embryo is still in the oviduct, and it continues to implantation. Immunological processes involving cytokines, mast cells and macrophages form an important part of this dialogue. Amongst the cytokines, interleukin-6 (Il-6) and leukemia inhibitory factor (LIF) are secreted by both the embryo and uterine endometrium and form part of an ongoing and reciprocating dialogue. Mast cells and macrophages populate the uterine endometrium during embryo development and are involved in achieving the correct balance between inflammatory and anti-inflammatory reactions at the uterus that are associated with embryo attachment and implantation. Embryo loss is the major cause of reproductive wastage in cattle, and livestock generally. A deeper understanding of immunological processes during early embryo development will help to achieve the next step change in the efficiency of natural and assisted breeding.

Conceptus metabolomic profiling reveals stage-specific phenotypes leading up to pregnancy recognition in cattle†

Reproductive efficiency in livestock is a major driver of sustainable food production. The poorly understood process of ruminant conceptus elongation (a) prerequisites maternal pregnancy recognition, (b) is essential to successful pregnancy establishment, and (c) coincides with a period of significant conceptus mortality. Conceptuses at five key developmental stages between Days 8-16 were recovered and cultured in vitro for 6 h prior to conditioned media analysis by untargeted ultrahigh-performance liquid chromatography tandem mass spectroscopy. This global temporal biochemical interrogation of the ex situ bovine conceptus unearths two antithetical stage-specific metabolic phenotypes during tubular (metabolically retentive) vs. filamentous (secretory) development. Moreover, the retentive conceptus phenotype on Day 14 coincides with an established period of elevated metabolic density in the uterine fluid of heifers with high systemic progesterone-a model of accelerated conceptus elongation. These data, combined, suggest a metabolic mechanism underpinning conceptus elongation, thereby enhancing our understanding of the biochemical reciprocity of maternal-conceptus communication, prior to maternal pregnancy recognition.

Isolation and Characterization of Equine Uterine Extracellular Vesicles: A Comparative Methodological Study

Extracellular vesicles (EVs) have been identified in the uterine fluid in different species and have been pointed as key players in the embryo-maternal dialogue, maternal recognition of pregnancy and establishment of pregnancy. However, little is known about the uterine EVs in the mare. Therefore, the present study aimed at characterizing EVs from uterine lavage of cyclic mares by comparing five EVs isolation methods and the combination of them: (1) ultracentrifugation (UC); (2) concentration of lavage volume by Centricon ultrafiltration (CE); (3) the use of CE with different washing steps (phosphate-buffered saline with or without trehalose); (4) size-exclusion chromatography with iZON-qEV columns, and (5) a combination of the methods with best results based on EVs yield, purity, and protein cargo profiles. Transmission electron microscopy and Western blotting confirmed the isolation of EVs by all methods but with quantitative and qualitative differences. Mass spectrometry provided differences in protein profiles between methods, number of identified proteins, and protein classes. Our results indicate that the combination of CE/trehalose/iZON/UC is an optimal method to isolate equine uterine EVs with good yield and purity that can be applied in future studies to determine the role of equine uterine EVs in embryo-maternal interactions.

Analysis of the uterine flush fluid proteome of healthy mares and mares with endometritis or fibrotic endometrial degeneration

The objective of this study was to evaluate the differences in the uterine flush fluid proteome between healthy mares and mares with endometritis or fibrotic endometrial degeneration (FED). Uterine flush fluid samples were collected from healthy mares (n=8; oestrus n=5 and dioestrus n=3) and mares with endometritis (n=23; oestrus n=14 and dioestrus n=9) or FED (n=7; oestrus n=6 and dioestrus n=1). Proteomic analysis was performed using label-free liquid chromatography-tandem mass spectrometry. Of 216 proteins identified during oestrus, 127 were common to all three groups, one protein was exclusively detected in healthy mares, 47 proteins were exclusively detected in mares with endometritis and four proteins were exclusively detected in mares with FED. Of 188 proteins identified during dioestrus, 113 proteins were common between healthy mares and mares with endometritis, eight proteins were exclusively detected in healthy mares and 67 proteins were exclusively detected in mares with endometritis. Quantitative analysis revealed a subset of proteins differing in abundance between the three groups during oestrus and between healthy mares and mares with endometritis during dioestrus. These results provide a springboard for evaluation of specific proteins as biomarkers of uterine health and disease and for investigation of their roles in the establishment and maintenance of pregnancy.

Conceptus-induced, interferon tau-dependent gene expression in bovine endometrial epithelial and stromal cells†

Bovine endometrium consists of epithelial and stromal cells that respond to conceptus interferon tau (IFNT), the maternal recognition of pregnancy (MRP) signal, by increasing expression of IFN-stimulated genes (ISGs). Endometrial epithelial and stromal-cell-specific ISGs are largely unknown but hypothesized to have essential functions during pregnancy establishment. Bovine endometrial epithelial cells were cultured in inserts above stromal fibroblast (SF) cells for 6 h in medium alone or with IFNT. The epithelial and SF transcriptomic response was analyzed separately using RNA sequencing and compared to a list of 369 DEGs recently identified in intact bovine endometrium in response to elongating bovine conceptuses and IFNT. Bovine endometrial epithelial and SF shared 223 and 70 DEGs in common with the list of 369 endometrial DEGs. Well-known ISGs identified in the epithelial and SF were ISG15, MX1, MX2, and OAS2. DEGs identified in the epithelial but not SF included a number of IRF molecules (IRF1, IRF2, IRF3, and IRF8), mitochondria SLC transporters (SLC25A19, SLC25A28, and SLC25A30), and a ghrelin receptor. Expression of ZC3HAV1, an anti-retroviral gene, increased specifically within the SF. Gene ontology analysis identified the type I IFN signaling pathway and activation of nuclear factor kappa B transcription factors as biological processes associated with the epithelial cell DEGs. This study has identified biologically relevant IFNT-stimulated genes within specific endometrial cell types. The findings provide critical information regarding the effects of conceptus IFNT on specific endometrial compartments during early developmental processes in cattle.

The role of CAPG in molecular communication between the embryo and the uterine endometrium: Is its function conserved in species with different implantation strategies?

During the preimplantation period of pregnancy in eutherian mammals, transcriptional and proteomic changes in the uterine endometrium are required to facilitate receptivity to an implanting blastocyst. These changes are mediated, in part, by proteins produced by the developing conceptus (inner cell mass and extraembryonic membranes). We hypothesized that this common process in early pregnancy in eutheria may be facilitated by highly conserved conceptus-derived proteins such as macrophage capping protein (CAPG). We propose that CAPG may share functionality in modifying the transcriptome of the endometrial epithelial cells to facilitate receptivity to implantation in species with different implantation strategies. A recombinant bovine form of CAPG (91% sequence identity between bovine and human) was produced and bovine endometrial epithelial (bEECs) and stromal (bESCs) and human endometrial epithelial cells (hEECs) were cultured for 24 hours with and without recombinant bovine CAPG (rbCAPG). RNA sequencing and quantitative real-time PCR analysis were used to assess the transcriptional response to rbCAPG (Control, vehicle, CAPG 10, 100, 1000 ng/mL: n = 3 biological replicates per treatment per species). Treatment of bEECs with CAPG resulted in alterations in the abundance of 1052 transcripts (629 increased and 423 decreased) compared to vehicle controls. Treatment of hEECs with bovine CAPG increased expression of transcripts previously known to interact with CAPG in different systems (CAPZB, CAPZA2, ADD1, and ADK) compared with vehicle controls (P < .05). In conclusion, we have demonstrated that CAPG, a highly conserved protein in eutherian mammals, elicits a transcriptional response in the endometrial epithelium in species with different implantation strategies that may contribute to pregnancy success.

Symposium review: Progesterone effects on early embryo development in cattle

The causes of low fertility in dairy cattle are complex and multifactorial and may be due to compromised follicle development affecting oocyte quality, a suboptimal reproductive tract environment incapable of supporting normal embryo development, or a combination of both. Progesterone (P4) plays a key role in reproductive events associated with establishment and maintenance of pregnancy, through its effects on oocyte quality and its action on the uterine endometrium. Reduced P4 concentrations during growth of the ovulatory follicle are associated with lower fertility, and low concentrations of circulating P4 after ovulation have been associated with reductions in conceptus growth and elongation, decreased interferon-τ (IFNT) production, and lower pregnancy rates in cattle. In contrast, elevated concentrations of circulating P4 in the period immediately following conception have been associated with advancement of conceptus elongation, increased IFNT production, and, in some cases, higher pregnancy rates in cattle. Despite the potential beneficial effects of exogenous P4 supplementation on fertility, results of supplementation studies have been inconsistent. As part of the 2019 ADSA Reproduction Symposium, focusing on the etiology of pregnancy losses in dairy cattle, the aim of this review is to highlight recent findings from our group and others in relation to embryo-maternal interaction during bovine pregnancy establishment and the role of P4 in uterine biology and embryo development.

Protein Synthesis by Day 16 Bovine Conceptuses during the Time of Maternal Recognition of Pregnancy

Interferon Tau (IFNT), the conceptus-derived pregnancy recognition signal in cattle, significantly modifies the transcriptome of the endometrium. However, the endometrium also responds to IFNT-independent conceptus-derived products. The aim of this study was to determine what proteins are produced by the bovine conceptus that may facilitate the pregnancy recognition process in cattle. We analysed by mass spectrometry the proteins present in conceptus-conditioned media (CCM) after 6 h culture of Day 16 bovine conceptuses (n = 8) in SILAC media (arginine- and lysine-depleted media supplemented with heavy isotopes) and the protein content of extracellular vesicles (EVs) isolated from uterine luminal fluid (ULF) of Day 16 pregnant (n = 7) and cyclic (n = 6) cross-bred heifers on day 16. In total, 11,122 proteins were identified in the CCM. Of these, 5.95% (662) had peptides with heavy labelled amino acids, i.e., de novo synthesised by the conceptuses. None of these proteins were detected in the EVs isolated from ULF. Pregnancy-associated glycoprotein 11, Trophoblast Kunitz domain protein 1 and DExD-Box Helicase 39A were de novo produced and present in the CCM from all conceptuses and in previously published CCM data following 6 and 24 h. A total of 463 proteins were present in the CCM from all the conceptuses in the present study, and after 6 and 24 h culture in a previous study, while expression of their transcripts was not detected in endometrium indicating that they are likely conceptus-derived. Of the proteins present in the EVs, 67 were uniquely identified in ULF from pregnant heifers; 35 of these had been previously reported in CCM from Day 16 conceptuses. This study has narrowed a set of conceptus-derived proteins that may be involved in EV-mediated IFNT-independent embryo–maternal communication during pregnancy recognition in cattle.

Immunological detection of pregnancy: Evidence for systemic immune modulation during early pregnancy in ruminants

Mammalian pregnancy creates unique challenges for immune systems highly evolved to detect and eliminate invading pathogens. Recognition of the challenges created by gestating a semi-allogeneic fetus evolved from the discipline of transplantation biology and were informed by studies on the unique natural parabiosis that occurs when female calves are gestated with twin male fetuses. These pregnancies typically result in an intersex female termed a freemartin, which revealed insights into development of the male and female reproductive tracts. However, they also uncovered important clues on immune tolerance with wide-ranging implications to reproductive biology, transplantation biology and autoimmune disease. Many studies focused on identifying mechanisms through which the fetus evades maternal immune detection and elimination. These included studies characterizing immune interactions between the fetus and mother at the nourishing interface of the placenta and uterine endometrium. This immunological forbearance only occurs under high concentrations of circulating progesterone. Beyond the requirement for progesterone, there has been considerable progress towards understanding the effects of conceptus signals on maternal immune function. One common theme is that pregnancy induces a T helper 2 immune bias as shown in several mammalian species, including domestic ruminants. However, a growing body of evidence shows that the fetus not only evades, but also provokes immune responses locally in the uterus and in peripheral tissues. This is perhaps most dramatically illustrated by domestic ruminants where the conceptus secretes a unique interferon in the opening salvo of hormonal communication with the maternal immune system. The role of interferon tau in regulating expression of genes of the innate immune system in the uterus has been extensively studied. More recently, it was determined that these same genes are also induced in peripheral immune cells and other tissues throughout the body. In addition to interferon tau and progesterone, pregnancy associate glycoproteins and chaperonin 10 (aka Early Pregnancy Factor) are implicated in altering immune function both locally and systemically during pregnancy. While it is tempting to speculate that this activation of innate immunity is designed to counteract selective immunosuppression, knowledge of the importance of local and systemic immune activation to the success of pregnancy remains incomplete. This area remains fertile ground for developing better approaches to diagnose and treat infertility in domestic farm species and humans alike.

Interferon tau-dependent and independent effects of the bovine conceptus on the endometrial transcriptome†

This study investigated bovine conceptus-induced modifications to the endometrial transcriptome related to effects of interferon tau (IFNT), conceptus origin (in vivo vs. in vitro), and conceptus sex. In vitro (IVF) or in vivo (superovulation and artificial insemination, AI) produced blastocysts were transferred into recipient heifers on day 7 of the estrous cycle. On day 15, IVF- or AI-derived conceptuses were obtained by uterine flushing and individually placed on endometrial explants in media for 6 h. Explants were also cultured with media alone as a control or media containing 100 ng/mL IFNT. Total explant RNA was analyzed by RNA-Seq. Incubation of endometrium with IFNT or IVF- or AI-derived conceptuses changed (P ≤ 0.001) expression of 491, 498, and 576 transcripts, respectively, compared to the control. Further, 369 differentially expressed genes (DEGs) were common between explants exposed to IFNT or a conceptus. A total of 240 DEGs were uniquely altered by conceptuses (IVF- and AI-derived) but not IFNT. Of these transcripts, 46 were shared between the IVF and AI groups, while 61 and 133 were specific to IVF and AI conceptuses, respectively. Five genes [melanophilin (MLPH), prominin-2 (PROM2), myeloid associated differentiation marker (MYADM), vomeronasal 1 receptor 4 like (VN1R4L) and 5-hydroxytryptamine receptor 1A (HTR1A)] were more abundant in endometrium exposed to female compared to male conceptuses (P < 0.001). A single gene [ADP-ribosylation factor like GTPase 4C (ARL4C)] was more abundant in response to male conceptuses (P < 0.001) than female conceptuses. These data support the hypothesis that conceptus regulation of gene expression in the endometrium is complex and involves factors other than IFNT that may have a biological role in pregnancy establishment.

Analysis of the uterine lumen in fertility-classified heifers: II. Proteins and metabolites†

Survival and growth of the bovine conceptus is dependent on endometrial secretions or histotroph. Previously, serial blastocyst transfer was used to classify heifers as high fertile (HF), subfertile (SF), or infertile (IF). Here, we investigated specific histotroph components (proteins and metabolites) in the uterine lumen of day 17 fertility-classified heifers. Interferon tau (IFNT) was more abundant in uterine lumenal fluid (ULF) of pregnant HF than SF animals as the conceptus was longer in HF heifers. However, no differences in endometrial expression of selected classical and nonclassical interferon-stimulated genes (ISGs) were observed, suggesting that IFNT signaling in the endometrium of pregnant HF and SF heifers was similar. Pregnancy significantly increased the abundance of several proteins in ULF. Based on functional annotation, the abundance of a number of proteins involved in energy metabolism, oxidative stress, amino acid metabolism, and cell proliferation and differentiation were greater in the ULF of pregnant HF than SF heifers. Metabolomics analysis found that pregnancy only changed the metabolome composition of ULF from HF heifers. The majority of the metabolites that increased in the ULF of pregnant HF as compared to SF heifers were associated with energy and amino acid metabolism. The observed differences in ULF proteome and metabolome are hypothesized to influence uterine receptivity with consequences on conceptus development and survival in fertility-classified heifers.

Aspects of embryo-maternal communication in establishment of pregnancy in cattle

Establishment of pregnancy in mammals requires reciprocal molecular communication between the conceptus and endometrium that modifies the endometrial transcriptome and uterine luminal milieu to support pregnancy. Due to the small size of the early embryo and elongating conceptus relative to the volume of the uterine lumen, collection of endometrium adjacent to the developing conceptus is difficult following conventional uterine flushing methods in cattle. Use of endometrial explants in culture can overcome this challenge and reveal information about the dialogue between the developing embryo and the uterus. The aim of this short review is to summarize some of our recent findings in relation to embryo maternal interaction during bovine pregnancy establishment and to put them in the wider context of fertility in cattle.

Effects of feeding OmniGen-AF® on superovulatory response in donor beef cows: I. Serum progesterone and cortisol, embryo recovery and quality

Optimal results in cattle embryo transfer are limited by the variation in ova recovery, fertilization rate and embryo quality experienced with superovulation. Inflammation and immune dysregulation may be contributing factors. This study, evaluated feeding OmniGen-AF® (OG), a nutritional supplement that reduces inflammation and supports immune health, on superovulatory response and serum progesterone and cortisol concentrations in embryo donors treated with two different doses of Folltropin®-V (FSH). Angus cross-bred beef cows (n = 24) were assigned to four groups, fed OG at 0 or 56 g/animal/day for 49 days and were treated with 200 or 400 mg FSH to induce superovulation. Treatments for superovulation started after feeding OG for 28 days and ova were non-surgically recovered 7 days after estrus and graded for quality. More transferrable embryos (P < 0.05) were recovered from cows fed 56 g OG and treated with 400 compared with 200 mg FSH. Percent degenerate embryos recovered from cows treated with the 400 mg FSH dose was threefold greater (P < 0.05) when fed no OG compared with 56 g OG. Serum progesterone on day of embryo collection was greater (P < 0.05) in OG-supplemented cows and cows treated with 200 mg FSH. Serum cortisol was not affected (P > 0.10) by FSH dose or OG-feeding, but was greatest (P <  0.05) on Days 0 and 42 of the feeding period. In summary, the improvement in embryo quality with OG-feeding may relate to a greater serum progesterone concentration.

BOARD INVITED REVIEW: Post-transfer consequences of in vitro-produced embryos in cattle

In vitro embryo production (IVP) in cattle has gained worldwide interest in recent years, but the efficiency of using IVP embryos for calf production is far from optimal. This review will examine the pregnancy retention rates of IVP embryos and explore causes for pregnancy failures. Based on work completed over the past 25 yr, only 27% of cattle receiving IVP embryos will produce a live calf. Approximately 60% of these pregnancies fail during the first 6 wk of gestation. When compared with embryos generated by superovulation, pregnancy rates are 10% to 40% lower for cattle carrying IVP embryos, exemplifying that IVP embryos are consistently less competent than in vivo-generated embryos. Several abnormalities have been observed in the morphology of IVP conceptuses. After transfer, IVP embryos are less likely to undergo conceptus elongation, have reduced embryonic disk diameter, and have compromised yolk sac development. Marginal binucleate cell development, cotyledon development, and placental vascularization have also been documented, and these abnormalities are associated with altered fetal growth trajectories. Additionally, in vitro culture conditions increase the risk of large offspring syndrome. Further work is needed to decipher how the embryo culture environment alters post-transfer embryo development and survival. The risk of these neonatal disorders has been reduced by the use of serum-free synthetic oviductal fluid media formations and culture in low oxygen tension. However, alterations are still evident in IVP oocyte and embryo transcript abundances, timing of embryonic cleavage events and blastulation, incidence of aneuploidy, and embryonic methylation status. The inclusion of oviductal and uterine-derived embryokines in culture media is being examined as one way to improve the competency of IVP embryos. To conclude, the evidence presented herein clearly shows that bovine IVP systems still must be refined to make it an economical technology in cattle production systems. However, the current shortcomings do not negate its current value for certain embryo production needs and for investigating early embryonic development in cattle.

Clinical significance and role of up-regulation of SERPINA3 expression in endometrial cancer

BACKGROUND

Serpin peptidase inhibitor, clade A member 3 (SERPINA3) belongs to the serpin family with an inhibitory activity against proteases. Its aberrant expression has been observed in a wide range of tumor cells. However, its clinical significance and biological function in endometrial cancer have been rarely studied. We designed a study to determine the levels of SERPINA3 and its significance in patients with endometrial cancer.

AIM

To investigate the clinical significance and role of SERPINA3 expression in endometrial cancer cells.

METHODS

Eighty endometrial tissue samples collected from patients with endometrial cancer were included in an observation group and 80 paraffin-embedded tissues samples collected from patients with normal endometrial tissues undergoing myomectomy were employed as a control group between January 2014 and December 2018. The expression of SERPINA3 mRNA was detected by quantitative polymerase chain reaction (PCR) for all endometrial tissues included in the study.

RESULTS

The positive expression rate of SERPINA3 protein in endometrial cancer cells was 71.25% in the observation group, which was significantly higher than that in the control group (31.25%; P < 0.05). There was no correlation between SERPINA3 protein in endometrial cancer cells and the age range at which women experienced menopause (P > 0.05). However, it was associated with pathological grade, clinical stage, vascular invasion, and lymph node metastasis (P < 0.05). Pathological grade, clinical stage, vascular invasion, and lymph node metastasis were independent prognostic factors for endometrial cancer.

CONCLUSION

The follow-up study of SERPINA3 can be used as a prognostic biomarker for endometrial cancer and as one of the targets for bio-targeted therapy for endometrial cancer.

Bovine endometrium responds differentially to age-matched short and long conceptuses†

This study combined in vitro production of bovine blastocysts, multiple embryo transfer techniques, and a conceptus-endometrial explant co-culture system to test the hypothesis that bovine endometrium exposed to long vs. short day 15 conceptuses would exhibit a different transcriptome profile reflective of potential for successful pregnancy establishment. Bovine endometrial explants collected at the late luteal stage of the estrous cycle were cultured in RPMI medium for 6 h with nothing (control), 100 ng/mL recombinant ovine interferon tau (IFNT), a long day 15 conceptus, or a short day 15 conceptus. Transcriptional profiling of the endometrial explants found that exposure of endometrium to IFNT, long conceptuses, or short conceptuses altered (P < 0.05) expression of 491, 498, and 230 transcripts, respectively, compared to the control. Further analysis revealed three categories of differentially expressed genes (DEG): (i) commonly responsive to exposure to IFNT and conceptuses, irrespective of size (n = 223); (ii) commonly responsive to IFNT and long conceptuses only (n = 168); and genes induced by the presence of a conceptus but independent of IFNT (n = 108). Of those 108 genes, 101 were exclusively induced by long conceptuses and functional analysis revealed that regulation of molecular function, magnesium-ion transmembrane transport, and clathrin coat assembly were the principal gene ontologies associated with these DEG. In conclusion, bovine endometrium responds differently to age-matched conceptuses of varying size in both an IFNT-dependent and -independent manner, which may be reflective of the likelihood of successful pregnancy establishment.

Uterine fluid proteome changes during diapause and resumption of embryo development in roe deer (Capreolus capreolus)

The uterine microenvironment during pre-implantation presents a pro-survival milieu and is essential for embryo elongation in ruminants. The European roe deer (Careolus capreolus) pre-implantation embryo development is characterised by a 4-month period of reduced development, embryonic diapause, after which the embryo rapidly elongates and implants. We investigated the uterine fluid proteome by label-free liquid chromatography tandem mass spectrometry at four defined stages covering the phase of reduced developmental pace (early diapause, mid-diapause and late diapause) and embryo elongation. We hypothesised that embryo development during diapause is halted by the lack of signals that support progression past the blastocyst stage. Three clusters of differentially abundant proteins were identified by a self-organising tree algorithm: (1) gradual reduction over development; (2) stable abundance during diapause, followed by a sharp rise at elongation; and (3) gradual increase over development. Proteins in the different clusters were subjected to gene ontology analysis. 'Cellular detoxification' in cluster 1 was represented by alcohol dehydrogenase, glutathione S-transferase and peroxiredoxin-2. ATP-citrate synthase, nucleolin, lamin A/C, and purine phosphorylase as cell proliferation regulators were found in cluster 2 and 'cortical cytoskeleton', 'regulation of substrate adhesion-dependent cell spreading' and 'melanosome' were present in cluster 3. Cell cycle promoters were higher abundant at elongation than during diapause, and polyamines presence indicates their role in diapause regulation. This study provides a comprehensive overview of proteins in the roe deer uterine fluid during diapause and forms a basis for studies aiming at understanding the impact of the lack of cell cycle promoters during diapause.

Symposium review: Immunological detection of the bovine conceptus during early pregnancy

Infertility and subfertility reduce the economic viability of dairy production. Inflammation reduces conception rates in dairy cattle, but surprisingly little information exists about the populations and the functions of immune cells at the conceptus-maternal interface during the periattachment period in dairy cattle. Early pregnancy is accompanied by immune stimulation at insemination and conceptus secretion of IFN-τ, pregnancy-associated glycoproteins, prostaglandins, and other molecules whose effects on immune function during early pregnancy have not been determined. Our working hypothesis is that pregnancy induces changes in immune cell populations and functions that are biased toward immunological tolerance, tissue remodeling, and angiogenesis. This review summarizes current knowledge, starting with insemination and proceeding through early pregnancy, as this is the period of maximal embryo loss. Results indicated that early pregnancy is accompanied by a marked increase in the proportion of endometrial immune cells expressing markers for natural killer (CD335) cells and cytotoxic T cells (CD8) along with an increase in cells expressing major histocompatibility class II antigens (macrophages and dendritic cells). This is accompanied by increased abundance of mRNA for IL-15, a natural killer growth factor, and IL-10 in the endometrium during early pregnancy. Furthermore, expression of indoleamine 2,3 dioxygenase was 15-fold greater in pregnant compared with cyclic heifers at d 17, but then declined by d 20. This enzyme converts tryptophan to kynurenine, which alters immune function by creating a localized tryptophan deficiency and by activation of the aryl hydrocarbon receptor and induction of downstream tolerogenic mediators. Expression of the aryl hydrocarbon receptor is abundant in the bovine uterus, but its temporal and spatial regulation during early pregnancy have not been characterized. Pregnancy is also associated with increased expression of proteins known to inhibit immune activation, including programed cell death ligand-1 (CD274), lymphocyte activation gene-3 (CD223), and cytotoxic T-lymphocyte associated protein-4 (CD152). These molecules interact with receptors on antigen-presenting cells and induce lymphocyte tolerance. Current results support the hypothesis that early pregnancy signaling in dairy heifers involves changes in the proportions of immune cells in the endometrium as well as induction of molecules known to mediate tolerance. These changes are likely essential for uterine wall remodeling, placentation, and successful pregnancy.

Embryo development in cattle and interactions with the reproductive tract

Embryo mortality is a major contributor to poor reproductive efficiency and profitability in cattle production systems. Coordinated interaction between the developing embryo or conceptus and the maternal reproductive tract is essential for pregnancy establishment in mammals. Up to the blastocyst stage, the embryo can grow in the absence of contact with the oviduct or uterus; however, conceptus elongation after hatching and before implantation, a characteristic of ruminant early development, is entirely maternally driven and is essential to ensure that sufficient quantities of interferon-τ (IFNT) are secreted by the developing conceptus to abrogate the mechanisms that bring about luteolysis. Surprisingly, many questions, such as the threshold level of IFNT required for pregnancy maintenance, remain unanswered. Failure of the conceptus to elongate undoubtedly results in embryonic loss and is thus believed to contribute greatly to reproductive failure in cattle.

RNA-sequencing analysis of umbilical cord plasma microRNAs from healthy newborns

MicroRNAs are a class of small non-coding RNA that regulate gene expression at a post-transcriptional level. MicroRNAs have been identified in various body fluids under normal conditions and their stability as well as their dysregulation in disease has led to ongoing interest in their diagnostic and prognostic potential. Circulating microRNAs may be valuable predictors of early-life complications such as birth asphyxia or neonatal seizures but there are relatively few data on microRNA content in plasma from healthy babies. Here we performed small RNA-sequencing analysis of plasma processed from umbilical cord blood in a set of healthy newborns. MicroRNA levels in umbilical cord plasma of four male and four female healthy babies, from two different centres were profiled. A total of 1,004 individual microRNAs were identified, which ranged from 426 to 659 per sample, of which 269 microRNAs were common to all eight samples. Many of these microRNAs are highly expressed and consistent with previous studies using other high throughput platforms. While overall microRNA expression did not differ between male and female cord blood plasma, we did detect differentially edited microRNAs in female plasma compared to male. Of note, and consistent with other studies of this type, adenylation and uridylation were the two most prominent forms of editing. Six microRNAs, miR-128-3p, miR-29a-3p, miR-9-5p, miR-218-5p, 204-5p and miR-132-3p were consistently both uridylated and adenylated in female cord blood plasma. These results provide a benchmark for microRNA profiling and biomarker discovery using umbilical cord plasma and can be used as comparative data for future biomarker profiles from complicated births or those with early-life developmental disorders.

Blastocyst-induced changes in the bovine endometrial transcriptome

The objectives of this study were (i) to determine whether blastocyst-induced responses in endometrial explants were detectable after 6- or 24-h co-culture in vitro; (ii) to test if direct contact is required between embryos and the endometrial surface in order to stimulate endometrial gene expression; (iii) to establish the number of blastocysts required to elicit a detectable endometrial response; (iv) to investigate if upregulation of five interferon-stimulated genes (ISGs) in the endometrium was specific to the blastocyst stage and (v) to test if alterations in endometrial gene expression can be induced by blastocyst-conditioned medium. Exposure of endometrial explants to Day 8 blastocysts in vitro for 6 or 24 h induced the expression of ISGs (MX1, MX2, OAS1, ISG15, RSAD2); expression of IFNAR1, IFNAR2, NFKB1, IL1B, STAT1, LGALS3BP, LGALS9, HPGD, PTGES, ITGB1, AKR1C4, AMD1 and AQP4 was not affected. Culture of explants in the presence of more than five blastocysts was sufficient to induce the effect, with maximum expression of ISGs occurring in the presence of 20 blastocysts. This effect was exclusive to blastocyst stage embryos; oocytes, 2-cell embryos or Day 5 morulae did not alter the relative abundance of any of the transcripts examined. Direct contact between blastocysts and the endometrial surface was not required in order to alter the abundance of these transcripts and blastocyst-conditioned medium alone was sufficient to stimulate a response. Results support the notion that local embryo-maternal interaction may occur as early as Day 8 of pregnancy in cattle.