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

IFNT-induced IRF1 enhances bovine endometrial receptivity by transactivating LIFR

Interferon-τ (IFN-τ) participates in the establishment of endometrial receptivity in ruminants. However, the precise mechanisms by which IFN-τ establishes bovine endometrial receptivity remain largely unknown. Interferon regulatory factor 1 (IRF1) is a classical interferon-stimulated gene (ISG) induced by type I interferon, including IFN-τ. Leukemia inhibitory factor receptor (LIFR) is a transmembrane receptor for leukemia inhibitory factor (LIF), which is a key factor in regulating embryo implantation in mammals. This study aimed to investigate the roles of IRF1 and LIFR in the regulation of bovine endometrial receptivity by IFN-τ. In vivo, we found IRF1 and LIFR were upregulated in the bovine endometrial luminal epithelium on Day 18 of pregnancy compared to Day 18 of the estrous cycle. In vitro, IFN-τ could upregulate IRF1, LIFR, and endometrial receptivity markers (LIF, HOXA10, ITGAV, and ITGB3) expression, downregulate E-cadherin expression and reduce the quantity of microvilli of bovine endometrial epithelial cells (bEECs). Overexpression of IRF1 had similar effects to IFN-τ on endometrial receptivity, and interference of LIFR could block these effects, suggesting the positive effects of IRF1 on endometrial receptivity were mediated by LIFR. Dual luciferase reporter assay verified that IRF1 could transactivate LIFR transcription by binding to its promoter. In conclusion, IFN-τ can induce IRF1 expression in bovine endometrial epithelial cells, and IRF1 upregulates LIFR expression by binding to LIFR promoter, contributing to the enhancement of bovine endometrial receptivity.

Early transcriptomic changes in peripheral blood 7 days after embryo transfer in dairy cattle

A common goal of the dairy industry is to shorten the calving interval to reap several benefits associated with improved fertility. Early pregnancy detection is crucial to shorten this interval, allowing for prompt re-insemination of cows that failed to conceive after the first service. Currently, the industry lacks a method to accurately predict pregnancy within the first 3 wk. The polypeptide cytokine IFN-tau (IFNT) is the primary signal for maternal recognition of pregnancy in ruminants. As IFNT is released from the early conceptus, it initiates a cascade of effects, including upregulation of IFN-stimulated genes (ISG). Expression of ISG can be detected in the peripheral blood. The present study aimed to characterize peripheral transcriptomic changes, including the ISG, as early as d 7 after embryo transfer. A total of 170 Holstein heifers received in vitro-produced embryos. Whole blood was collected from these heifers within 24 h of the embryo transfer (d 0), d 7, and d 14 after embryo transfer. The heifers were divided into 2 groups, pregnant and nonpregnant, based on pregnancy diagnosis on d 28 via ultrasound. Total RNA was extracted from the peripheral blood of pregnant and nonpregnant heifers, pooled and sequenced. Expression analysis on d 7 heifers resulted in 13 significantly differentially expressed genes mostly related to innate immunity. Differential expression analysis comparing pregnant heifers on d 0 to the same heifers on d 14 showed 51 significantly differentially expressed genes. Eight genes were further quantified through reverse-transcription quantitative real-time PCR for biological validation. On d 7 after embryo transfer, mRNA transcriptions of EDN1, CXCL3, CCL4, and IL1A were significantly upregulated in pregnant heifers (n = 14) compared with nonpregnant heifers (n = 14), with respective fold changes of 8.10, 18.12, 29.60, and 29.97. Although on d 14 after embryo transfer, mRNA transcriptions of ISG15, MX2, OASY1, and IFI6 were significantly upregulated in the blood of pregnant heifers (n = 14) compared with the same heifers on d 0, with respective fold changes of 5.09, 2.59, 3.89, and 3.08. These findings demonstrate that several immune-related genes and ISG are activated during the first 2 wk after embryo transfer, which may explain how the maternal immune system accommodates the allogenic conceptus. To further investigate the diagnostic potentials of these genes, future studies are warranted to analyze the specificity and sensitivity of these biomarkers to predict early pregnancy.

Effects of conceptus proteins on endometrium and blood leukocytes of dairy cattle using transcriptome and meta-analysis

This study investigates the short and long-term effects of IFNT and PAG on the transcriptome of endometrium and blood leukocytes. Holstein heifers received intrauterine infusions of one of the following treatments: 20 mL of a 200 μg/mL bovine serum albumin solution (BSA; vehicle) from day 14 to 16 of the estrous cycle (BSA), vehicle + 10 μg/mL of IFNT from day 14 to 16 (IFNT3), vehicle + 10 μg/mL of IFNT from day 14 to 19 (IFNT6), and vehicle + 10 μg/mL of IFNT from day 14 to 16 followed by vehicle + 10 μg/mL of IFNT + 5 μg/mL of PAG from day 17 to 19 (IFNT+PAG). RNA-seq analysis was performed in endometrial biopsies and blood leukocytes collected after treatments. Acute IFNT signaling in the endometrium (IFNT3 vs BSA), induced differentially expressed genes (DEG) associated with interferon activation, immune response, inflammation, cell death, and inhibited vesicle transport and extracellular matrix remodeling. Prolonged IFNT signaling (IFNT6 vs IFNT3) altered gene expression related to cell invasion, retinoic acid signaling, and embryo implantation. In contrast, PAG induced numerous DEG in blood leukocytes but only 4 DEG in the endometrium. In blood leukocytes, PAG stimulated genes involved in development and TGFB signaling while inhibiting interferon signaling and cell migration. Overall, IFNT is a primary regulator of endometrial gene expression, while PAG predominantly affected the transcriptome of circulating immune cells during early pregnancy. Further research is essential to fully grasp the roles of identified DEG in both the endometrium and blood leukocytes.

Transcriptomic analysis of bovine endometrial epithelial cells in response to interferon tau and hormone stimulation

The embryonic loss during early stage of gestation is one of the major causes of infertility for domestic ruminants, causing huge economic losses to pasture. Maternal recognition of pregnancy and implantation are the crucial process for determining the successful establishment and development of pregnancy in cattle. The research on molecular mechanisms of pregnancy recognition will facilitate illustrating the complex process of pregnancy establishment and help to improve pregnancy outcomes. In this study, we performed transcriptomic analysis of primary bovine endometrial epithelial cells (BEND) with or without IFNT and hormones intervention through RNA sequencing. We eventually identified 608 differentially expressed genes (DEGs) including 409 up-regulated genes and 199 down-regulated genes in IFNT and hormones-treated group compared with control group. Gene Ontology (GO) enrichment analysis demonstrated that the majority of DEGs were implicated in immune system process, response to external stimulus, response to cytokine, regulation of response to stress. Results from KEGG analysis showed a significant enrichment of NOD-like receptor signaling pathway, antigen processing and presentation, necroptosis, oxidative phosphorylation, RIG-I-like receptor signaling pathway. Additionally, a set of promising candidate genes, including (USP18, STAT1, PSMB8, IFIH1, MX2, IFI44, DHX58, CASP8, DRAM1, CXCR4), were characterized by constructing an integrated interaction network. Specifically, the mRNA expression of HOXA11, PTGS1 and PTGS2 were remarkably suppressed by silencing DRAM1 under IFNT and hormone administration, thus speculating that DRAM1 might play a crucial role in early pregnancy by regulating endometrial function. The results of this study depicted a relatively comprehensive transcriptional profiles of BEND in response to IFNT and hormones, which contributes to a better understanding of gene interaction network and underlying regulatory mechanisms in endometrium of ruminants during early pregnancy.

N-3 Polyunsaturated Fatty Acids as a Nutritional Support of the Reproductive and Immune System of Cattle-A Review

This paper focuses on the role of n-3 fatty acids as a nutrient crucial to the proper functioning of reproductive and immune systems in cattle. Emphasis was placed on the connection between maternal and offspring immunity. The summarized results confirm the importance and beneficial effect of n-3 family fatty acids on ruminant organisms. Meanwhile, dietary n-3 fatty acids supplementation, especially during the critical first week for dairy cows experiencing their peripartum period, in general, is expected to enhance reproductive performance, and the impact of its supplementation appears to be dependent on body condition scores of cows during the drying period, the severity of the negative energy balance, and the amount of fat in the basic feed ration. An unbalanced, insufficient, or excessive fatty acid supplementation of cows' diets in the early stages of pregnancy (during fetus development) may affect both the metabolic and nutritional programming of the offspring. The presence of the polyunsaturated fatty acids of the n-3 family in the calves' ration affects not only the performance of calves but also the immune response, antioxidant status, and overall metabolism of the future adult cow.

Progesterone-stimulated endometrial cell conditioned media increases in vitro produced bovine embryo blastocyst formation

The early bovine embryo is supported by histotroph molecules secreted by endometrial epithelial (EPI) and stroma fibroblast (SF) cells in response to luteal progesterone (P4). We hypothesized that specific histotroph molecule transcript abundance depends on cell type and P4 concentration and that endometrial cell conditioned media (CM) could improve in vitro produced (IVP) embryo development in culture. Primary bovine EPI and SF cells from seven uteri were incubated for 12 h with RPMI medium containing 0 (Control), 1, 15, or 50 ng of P4. RPMI was also incubated without cells (N-CM) and CM from EPI or SF cultures (EPI- or SF-CM) or a combination of the two (1:1; EPI/SF-CM) was used to culture IVP embryos from days 4-8 of development (n = 117). There was an effect of cell type (SLC1A1, SLC5A6, SLC7A1, FGF-2, FGF-7, CTGF, PRSS23 and NID2) and/or P4 concentration (FGF-7 and NID2) on endometrial cell histotroph molecule mRNA (P < 0.05). Compared to N-CM, blastocyst development on day 7 was greater in the EPI or SF-CM (P ≤ 0.05) and tended to be greater in the EPI/SF-CM (P = 0.07). On day 8, blastocyst development was greater only in the EPI-CM (P < 0.05). Further, culturing embryos with endometrial cell CM reduced day 8 blastocyst transcript abundance of cell adhesion molecule LGALS1 (P < 0.01). In conclusion, endometrial cell CM or histotroph molecules may be used to improve IVP embryo development in 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.

Extracellular Vesicles Secreted by Pre-Hatching Bovine Embryos Produced In Vitro and In Vivo Alter the Expression of IFNtau-Stimulated Genes in Bovine Endometrial Cells

The embryo-maternal interaction occurs during the early stages of embryo development and is essential for the implantation and full-term development of the embryo. In bovines, the secretion of interferon Tau (IFNT) during elongation is the main signal for pregnancy recognition, but its expression starts around the blastocyst stage. Embryos release extracellular vesicles (EVs) as an alternative mechanism of embryo-maternal communication. The aim of the study was to determine whether EVs secreted by bovine embryos during blastulation (D5-D7) could induce transcriptomic modifications, activating IFNT signaling in endometrial cells. Additionally, it aims to assess whether the EVs secreted by embryos produced in vivo (EVs-IVV) or in vitro (EVs-IVP) have different effects on the transcriptomic profiles of the endometrial cells. In vitro- and in vivo-produced bovine morulae were selected and individually cultured for 48 h to collect embryonic EVs (E-EVs) secreted during blastulation. E-EVs stained with PKH67 were added to in vitro-cultured bovine endometrial cells to assess EV internalization. The effect of EVs on the transcriptomic profile of endometrial cells was determined by RNA sequencing. EVs from both types of embryos induced several classical and non-classical IFNT-stimulated genes (ISGs) and other pathways related to endometrial function in epithelial endometrial cells. Higher numbers of differentially expressed genes (3552) were induced by EVs released by IVP embryos compared to EVs from IVV (1838). Gene ontology analysis showed that EVs-IVP/IVV induced the upregulation of the extracellular exosome pathway, the cellular response to stimulus, and the protein modification processes. This work provides evidence regarding the effect of embryo origin (in vivo or in vitro) on the early embryo-maternal interaction mediated by extracellular vesicles.

Identification of photoperiod-induced specific miRNAs in the adrenal glands of Sunite sheep (Ovis aries)

In seasonal estrus, it is well known that melatonin-regulated biorhythm plays a key role. Some studies indicate that the adrenal gland plays an important role in reproduction in mammals, but the molecular mechanism is not clear. This study used an artificially controlled light photoperiod model, combined with RNA-seq technology and bioinformatics analysis, to analyze the messenger RNA (mRNA) and microRNA (miRNA) of ewe (Sunite) adrenal glands under different photoperiod treatments. After identification, the key candidate genes GRHL2, CENPF, FGF16 and SLC25A30 that photoperiod affects reproduction were confirmed. The miRNAs (oar-miR-544-3p, oar-miR-411b-5p, oar-miR-376e-3p, oar-miR-376d, oar-miR-376b-3p, oar-miR-376a-3p) were specifically expressed in the adrenal gland. The candidate mRNA-miRNA pairs (e.g., SLC25A30 coagulated by novel miRNA554, novel miRNA555 and novel miRNA559) may affect seasonal estrus. In summary, we constructed relation network of the mRNAs and miRNAs of sheep adrenal glands using RNA sequencing and bioinformatics analysis, thereby, providing a valuable genetic variation resource for sheep genome research, which will contribute to the study of complex traits in sheep.

An in vitro comparison of antimicrobial efficacy and cytotoxicity between povidone-iodine and chlorhexidine for treating clinical endometritis in dairy cows

This study aimed to assess the in vitro antimicrobial effects of chlorhexidine (CHX) and povidone-iodine (PI) on clinical isolates of Escherichia coli (E. coli) and Trueperella pyogenes (T. pyogenes) from the vaginal discharge of dairy cows, as well as to compare the cytotoxicity effects of CHX and PI on bovine endometrial epithelial cells (BEnEpC). In Experiment 1, 12 E. coli and 10 T. pyogenes were isolated from the vaginal discharge of cows with a uterine infection. The MIC and MBC against CHX and PI were analyzed in vitro. In Experiment 2, the cytotoxicity effects of CHX and PI on BEnEpC were analyzed using a Viability/Cytotoxicity Kit, wound scratch healing assay, and the expression of pro-inflammatory cytokine genes (IL-6, IL-8, and TNF-α). In Experiment 1, the MIC and MBC values of CHX against E. coli were 0.0002% and 0.0002 to 0.00025%, respectively. The MIC and MBC values of PI were 1.25 to 2.5% and 1.25 to 5%, respectively. For T. pyogenes, the MIC and MBC values of CHX were 0.00002%. The MIC and MBC values of PI were 1.25%. In Experiment 2, the cell viability significantly decreased, and wound closures were significantly inhibited after treatment with ≥ 0.002% CHX and ≥ 0.025% PI. The expression of IL-6, IL-8, and TNF-α significantly increased after treatment with PI. Only IL-6 showed a significant increase after cells were treated with 0.00002% and 0.0002% CHX. The results suggested that both CHX and PI had high antibacterial effects. However, veterinarians and farmers should be aware of their cytotoxicity, which decrease viability of endometrial epithelial cells and inhibit wound healing in vitro.

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.

Progesterone and interferon tau regulate expression of polyamine enzymes during the ovine peri-implantation period

Progesterone (P4) and interferon tau (IFNT) are important for establishment and maintenance of pregnancy in ruminants. Agmatine and polyamines (putrescine, spermidine, and spermine) have important roles in the survival, growth, and development of mammalian conceptuses. This study tested the hypothesis that P4 and/or IFNT stimulate expression of genes and proteins involved in the metabolism and transport of polyamines in the ovine endometrium. Rambouillet ewes (n = 24) were surgically fitted with intrauterine catheters on Day 7 of the estrous cycle. They received daily intramuscular injections of 50 mg P4 in corn oil vehicle and/or 75 mg progesterone receptor antagonist (RU486) in corn oil vehicle from Days 8–15, and twice daily intrauterine injections (25 μg/uterine horn/day) of either control serum proteins (CX) or IFNT from Days 11–15, resulting in four treatment groups: 1) P4 + CX; 2) P4 + IFNT; 3) RU486 + P4 + CX; or 4) RU486 + P4 + IFNT. On Day 16, ewes were hysterectomized. The total amounts of arginine, citrulline, ornithine, agmatine, and putrescine in uterine flushings were affected (P &lt; 0.05) by P4 and/or IFNT. P4 increased endometrial expression of SLC22A2 (P &lt; 0.01) and SLC22A3 (P &lt; 0.05) mRNAs. IFNT affected endometrial expression of MAT2B (P &lt; 0.001), SAT1 (P &lt; 0.01), and SMOX (P &lt; 0.05) mRNAs, independent of P4. IFNT increased the abundance of SRM protein in uterine luminal (LE), superficial glandular (sGE), and glandular epithelia (GE), as well as MAT2B protein in uterine LE and sGE. These results indicate that P4 and IFNT act synergistically to regulate expression of key genes required for cell-specific metabolism and transport of polyamines in the ovine endometrium during the peri-implantation period of pregnancy.

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.

Transcriptomic Analysis of STAT1/3 in the Goat Endometrium During Embryo Implantation

Interferon tau (IFNT), a pregnancy recognition signal in ruminants, promotes the establishment of embryo implantation by inducing the expression of interferon-stimulated genes (ISGs) via the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway. However, the precise regulatory mechanism of IFNT in goat embryo implantation remains largely unknown. In this study, we performed RNA sequencing of goat endometrial epithelial cells (gEECs) with or without 20 ng/mL IFNT treatment. Differential comparison showed that there were 442 upregulated differentially expressed genes (DEGs) and 510 downregulated DEGs. Bioinformatic analyses revealed that DEGs were significantly enriched in immune-related functions or pathways. The qRT-PCR validation results showed that the expression levels of STAT family members (STAT1, STAT2, and STAT3) were significantly upregulated in gEECs after IFNT treatment, which is in agreement with the RNA-seq data. Meanwhile, the protein levels of p-STAT1 and p-STAT3 increased significantly in gEECs after 6 and 24 h of IFNT treatment, respectively. Further in vivo experiments also confirmed that both mRNA and protein phosphorylation levels of STAT1 and STAT3 in the uterus on day 18 of pregnancy (P18) were significantly increased compared to those on day 5 (P5) and day 15 of pregnancy (P15). On P5, STAT1 and STAT3 proteins were primarily located in the uterine luminal epithelium (LE) and glandular epithelium (GE), and were also detected in the stromal cells. The intense immunostaining of STAT1 and STAT3 proteins were decreased on P15 and then increased on P18, especially in the superficial GE and subepithelial stromal cells. Moreover, p-STAT1 and p-STAT3 were highly expressed in the deep GE on P18. Collectively, these results highlight the role of IFNT in regulating endometrial receptivity in gEECs and uncover the temporal and spatial changes in the expression of STAT1/3 during embryo implantation in the goat endometrium.