HH5 double-carrier embryos fail to progress through early conceptus elongation

Massive genotyping in cattle has uncovered several deleterious haplotypes that cause preterm mortality. Holstein haplotype 5 (HH5) is a deleterious haplotype present in the Holstein Friesian population that involves the ablation of the transcription factor B1 mitochondrial (TFB1M) gene. The developmental stage at which HH5 double-carrier (DC, homozygous) embryos or fetuses die remains unknown and this is a relevant information to estimate the economic losses associated with the inadvertent cross between carriers. To determine whether HH5 DC survive to maternal recognition of pregnancy, embryonic day (E) 14 embryos were flushed from superovulated carrier cows inseminated with a carrier bull. Double-carrier E14 conceptuses were recovered at Mendelian rates but they failed to achieve early elongation, as evidenced by a drastic reduction of their extra-embryonic membranes, which were >26-fold shorter than those of carrier or noncarrier embryos. To assess development at earlier stages, TFB1M knockout (KO) embryos-functionally equivalent to DC embryos-were generated by clustered regularly interspaced short palindromic repeats (CRISPR) technology and cultured to the blastocyst stage, in vitro culture day (D) 8, and to the early embryonic disc stage, D12. No significant effect of TFB1M ablation was observed on the differentiation and proliferation of embryonic lineages and relative mitochondrial DNA (mtDNA) content up to D12. In conclusion, HH5 DC embryos are able to develop to early embryonic disc stage but fail to undergo early conceptus elongation, which is required for pregnancy recognition.

In vitro regulation of gene expression of pregnancy-associated proteins and cytokines in bovine endometrial epithelial cells and bovine trophoblastic cells by infection with Neospora caninum

Abortion caused by the parasite Neospora caninum is an important threat to the livestock industry worldwide. Trophoblasts and caruncular cells play major roles in initiating innate immune responses and controlling parasite infection at the fetal-maternal interface. In the present study, bovine uterine epithelial cells (BUECs) and bovine trophoblastic (BT) cells treated with bovine interferon-gamma (IFN-γ), IFN-alpha (IFN-α) and IFN-tau (IFN-τ) followed by infection with N. caninum were examined by measuring the mRNA expression levels of numerous pregnancy-associated proteins and observing parasite growth to elucidate the host-parasite interaction at the uteroplacental region. N. caninum infection increased the expression of prolactin-related protein 1 (PRP1), pregnancy-associated glycoprotein 1 (PAG1), and cytokines (TNF-α, IL-8 and IL-10) in BUECs and of IL-8 in BT cells. Bovine IFN-γ inhibited IL-8 and TNF-α expression in BUECs and IL-8 in BT cells. In contrast, the expression of the interferon-stimulated gene OAS1 was significantly increased by treatment of the infected BT cells with IFN-γ. However, treatment with bovine IFNs did not inhibit N. caninum growth in either cell line. In conclusion, our results suggest that bovine IFN-γ plays a crucial role in control of pathogenesis in uterus and induction of inflammatory response in the placental region following N. caninum infection, rather than growth inhibition of the parasites.

Influence of sub-clinical endometritis on early pregnancy predictors and proinflammatory cytokines in circulating immune cells in dairy cows

In Experiment 1, PBMC were isolated from cows considered healthy or with SCE (n=6/group) on Days 0 (estrus) and 7 (diestrus) of a synchronized estrous cycle. In Experiment 2, on D21 (D0 was defined as the day of Fixed Timed Artificial Insemination (FTAI), cows were evaluated by ultrasonography to assess luteal blood perfusion and PBMC were isolated. On D32, cows were classified into: healthy pregnant (n=7), pregnant with SCE (n=4), healthy non-pregnant (n=8), and non-pregnant with SCE (n=10). Gene expression of ISGs (ISG15, OAS1, MX1 and IFI6) and proinflammatory cytokines (IL1-β, TNF-α and IFN-γ) were determined. Expression of ISG15, MX1, IFI6, TNF-α and IFN-γ did not differ between SCE and healthy cows and between Days 0 and 7. Expression of OAS1 and IL1-β were higher (P=0.02) on Day 7 than Day 0, regardlees of the SCE presence. In Exp.2, ISG15 abundance was 2.5-fold greater (P=0.0008), TNF-α was 2.2-fold greater (P=0.05), and IL1-β tended (P=0.06) to be 2.4-fold higher in pregnant than non-pregnant cows. Luteal blood perfusion was greater (P=0.01) in pregnant animals. In conclusion, OAS1 and IL1-β are transcripts upregulated in PBMC at diestrus, regardless of SCE occurrence. Proinflammatory cytokines are not affected by SCE occurrence, but IL1-β and TNF-α are upregulated in pregnant animals on D21 of pregnancy. ISG15 abundance is a good pregnancy predictor, regardless SCE presence.

Role of chemokines in regulating luteal and uterine functions in pregnant cows

Pregnancy is intricately regulated by the interactions between various bioactive substances secreted by the conceptus, uterus, and corpus luteum (CL). Interferon-τ, synthesized and secreted by the conceptus, plays a central role in the interaction mechanism of maternal recognition in cows. Chemokines, chemotaxis mediators that are primarily secreted by immune cells, regulate various reproductive responses in various species. Although there are scattered reports on the potential roles of chemokines in the bovine CL and the uterus during the estrous cycle, there is little information on chemokines in these organs during pregnancy. Therefore, in this review, we discuss the possible physiological roles of chemokines in the CL and uterus of pregnant cows, focusing on our recent findings on chemokines and changes in their receptor expression in the CL and endometrium of cows at some stages of 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.

Transcriptomics analysis of the bovine endometrium during the perioestrus period

During the oestrous cycle, the bovine endometrium undergoes morphological and functional changes, which are regulated by alterations in the levels of oestrogen and progesterone and consequent changes in gene expression. To clarify these changes before and after oestrus, RNA-seq was used to profile the transcriptome of oestrus-synchronized beef heifers. Endometrial samples were collected from 29 animals, which were slaughtered in six groups beginning 12 h after the withdrawal of intravaginal progesterone releasing devices until seven days post-oestrus onset (luteal phase). The groups represented proestrus, early oestrus, metoestrus and early dioestrus (luteal phase). Changes in gene expression were estimated relative to gene expression at oestrus. Ingenuity Pathway Analysis (IPA) was used to identify canonical pathways and functional processes of biological importance. A total of 5,845 differentially expressed genes (DEGs) were identified. The lowest number of DEGs was observed at the 12 h post-oestrus time point, whereas the greatest number was observed at Day 7 post-oestrus onset (luteal phase). A total of 2,748 DEGs at this time point did not overlap with any other time points. Prior to oestrus, Neurological disease and Organismal injury and abnormalities appeared among the top IPA diseases and functions categories, with upregulation of genes involved in neurogenesis. Lipid metabolism was upregulated before oestrus and downregulated at 48h post-oestrus, at which point an upregulation of immune-related pathways was observed. In contrast, in the luteal phase the Lipid metabolism and Small molecule biochemistry pathways were upregulated.

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.

Transcriptomic Changes in Response to Form of Selenium on the Interferon-Tau Signaling Mechanism in the Caruncular Tissue of Beef Heifers at Maternal Recognition of Pregnancy

We have reported that selenium (Se) provided to grazing beef cattle in an inorganic (ISe) form versus a 1:1 mixture (MIX) of inorganic and organic (OSe) forms affects cholesterol biosynthesis in the corpus luteum (CL), the abundance of interferon tau (IFNτ) and progesterone (P4)-induced mRNAs in the caruncular (CAR) tissue of the endometrium, and conceptus length at maternal recognition of pregnancy (MRP). In this study, beef heifers were supplemented with a vitamin-mineral mix containing 35 ppm Se as ISe or MIX to achieve a Se-adequate status. Inseminated heifers were killed at MRP (d 17, n = 6 per treatment) for tissue collection. In CAR samples from MIX versus ISe heifers, qPCR revealed that mRNA encoding the thyroid regulating DIO2 and DIO3 was decreased (p < 0.05) and a complete transcriptomic analysis revealed effects on the interferon JAK-STAT1/2 pathway, including decreased expression of mRNAs encoding the classical interferon stimulated genes IFIT1, IFIT2, IFIT3, IRF1, IRF9, ISG15, OAS2, and RSAD2 (p < 0.05). Treatment also affected the abundance of mRNAs contributing to the immunotolerant environment (p < 0.05). In combination, these findings suggest more advanced preparation of the CAR and developing conceptus for implantation and to evade immune rejection by the maternal system in MIX- vs. ISe-treated heifers.

Characterization of circulating microRNA profiles of postpartum dairy cows with persistent subclinical endometritis

Subclinical endometritis (SCE) is an unresolved inflammation of the endometrium of postpartum dairy cows, seriously affecting fertility. Current diagnosis, which relies on uterine cytology or even more invasive biopsy sampling, would benefit from the identification of blood-based diagnostic biomarkers. Due to the known role of microRNAs (miRNAs) in other diseases, this case-control study evaluated the cell-free circulating miRNA profiles of SCE cows, and the network of transcripts predicted to interact with those miRNAs, previously identified as differentially expressed genes (DEG) in the endometrium of the same cows. Healthy (H, n = 6) and persistent SCE (n = 11) cows characterized by endometrial cytology and biopsy were blood sampled at 21 and 44 d postpartum (DPP). Following extraction of cell-free plasma miRNAs and RNA-seq analysis, differential abundance analysis of miRNAs was performed with the DESeq2 R package (adjusted p-value of 0.05), and in silico prediction of miRNA-interacting genes on a sequence complementary basis was conducted using the miRWalk database. The principal component analysis showed a clear clustering between groups of uterine health phenotypes (H vs. SCE), although the clustering between groups was less pronounced at 44 DPP than at 21 DPP. No effect of the stage (21 vs. 44 DPP) was observed. A total of 799 known circulating miRNAs were identified, from which 34 demonstrated differential abundance between H and SCE cows (12 less abundant and 22 more abundant in SCE than in H cows). These 34 miRNAs are predicted to interact with 10,104 transcripts, among which 43, 81, and 147 were previously identified as differentially expressed in, respectively, endometrial luminal epithelial, glandular epithelial, and stromal cells of the same cows. This accounts for approximately half of the DEG identified between those H and SCE cows, including genes involved in endometrial cell proliferation, angiogenesis and immune response, whose dysregulation in SCE cows may impair pregnancy establishment. From 219 miRNAs with mean normalized read counts above 100, the presence and abundance of miR-425-3p and miR-2285z had the highest discriminatory level to differentiate SCE from H cows. In conclusion, despite apparent confinement to the endometrium, SCE is associated with a distinct circulating miRNA profile, which may represent a link between the systemic changes associated with disease and the endometrial immune response. The validation of a miRNA panel consisting of circulating cell-free miR-425-3p and miR-2285z may prove a relevant advancement for the noninvasive diagnosis of persistent SCE.

Dose- and time-dependent effects of interferon tau on bovine endometrial gene expression

Failure by the developing conceptus to secrete sufficient interferon tau (IFNT), required for maternal recognition of pregnancy (MRP), at the appropriate time is related to early pregnancy loss in cattle. We aimed to test the hypothesis that there is a dose- and time-dependent relationship between IFNT and the endometrial expression of key interferon-stimulated genes (ISGs) involved in the signalling cascade leading to MRP in cattle. Candidate genes were identified first through a bioinformatic approach, where integrated transcriptomic data from two previous studies were analyzed to identify endometrial genes induced by IFNT. Next, expression of selected candidate genes was investigated in vitro in endometrial explants. Endometrial explants collected from cows (n = 8) in the late luteal phase of the estrous cycle were cultured in medium without (control) or with recombinant ovine IFNT (1, 10, 100 ng/mL) for 6 h. Simultaneously, endometrial explants were cultured in medium containing 100 ng/mL IFNT for different time periods (15 min, 30 min, 1 h, 3 h, 6 h). Gene expression was analyzed by RT-qPCR. We identified 54 endometrial genes responding to IFNT and to some degree to the conceptus, from which five ISGs (CMPK2, BPNT1, IFI35, TNFSF10 and TRIM38) were further selected for the dose- and time-dependent experiments. Classical ISGs (ISG15, OAS1, MX1 and MX2) were up-regulated (P < 0.05) in endometrium by 1 ng/mL IFNT. However, other selected ISGs (CMPK2, BPNT1, IFI35, TNFSF10 and TRIM38) were induced only by higher concentrations (10 and 100 ng/mL) of IFNT (P < 0.05). In terms of duration of exposure, IFNT at 100 ng/mL induced a significant (P < 0.05) increase in ISG15 and CMPK2 expression after 1 h incubation, while all other studied ISGs in the endometrium were upregulated when cultured for 3 or 6 h, but did not affect expression when the duration of culture was for 1 h or less. These results suggest that IFNT acts on the uterus in both a dose- and time-dependent manner in cattle and that timely exposure of the endometrium to sufficient IFNT is essential for appropriate signalling to ensure successful pregnancy establishment.

Global analyses and potential effects of extracellular vesicles on the establishment of conceptus implantation during the peri-implantation period

Intrauterine extracellular vesicles (EVs) are involved in establishing proper conceptus-endometrial communication, which is essential for conceptus implantation and subsequent successful placentation. Despite several studies on intrauterine EVs, the composition and quantitative changes in conceptus and endometrial EVs, as well as the effects of intrauterine EVs on endometrial epithelial cells (EECs) during the peri-implantation period, have not been well characterized. To elucidate global changes in proteins in EVs extracted from uterine flushings (UFs) during the pre-implantation (P17), just-implantation (P20), and post-implantation (P22) periods, the datasets of the proteome iTRAQ analysis were compared among P17, P20, and P22 EVs. These analyses revealed that the composition and function of proteins in the EVs changed dramatically during peri-implantation in cattle. Notably, intrauterine P17 EVs affected the high expression of "Developmental Biology" and "morphogenesis of an endothelium" compared with those in P20 and P22 EVs. Furthermore, P20 EVs had the functions of the high expression of "mitochondrial calcium ion homeostasis" and "Viral mRNA Translation" compared with those in P17 EVs. Transcripts extracted from EECs treated with P17, P20, or P22 EVs were subjected to RNA-seq analysis. These analyses identified 60 transcripts in EECs commonly induced by intrauterine EVs recovered from P17, P20, and P22, a large number of which were associated with "type I interferon signaling pathway". Collectively, these findings reveal the presence and multiple functions of EVs that are potentially implicated in facilitating conceptus implantation into the uterine epithelium during the peri-implantation period.

Extensive rewiring of the gene regulatory interactions between in vitro-produced conceptuses and endometrium during attachment

Pregnancy loss is a significant problem when embryos produced in vitro are transferred to a synchronized uterus. Currently, mechanisms that underlie losses of in vitro-produced embryos during implantation are largely unknown. We investigated this problem using cattle as a model of conceptus attachment by analyzing transcriptome data of paired extraembryonic membrane and endometrial samples collected on gestation days 18 and 25, which spans the attachment window in cattle. We identified that the transfer of an in vitro-produced embryo caused a significant alteration in transcript abundance of hundreds of genes in extraembryonic and endometrial tissues on gestation days 18 and 25, when compared to pregnancies initiated by artificial insemination. Many of the genes with altered transcript abundance are associated with biological processes that are relevant to the establishment of pregnancy. An integrative analysis of transcriptome data from the conceptus and endometrium identified hundreds of putative ligand-receptor pairs. There was a limited variation of ligand-receptor pairs in pregnancies initiated by in vitro-produced embryos on gestation day 18, and no alteration was observed on gestation day 25. In parallel, we identified that in vitro production of embryos caused an extensive alteration in the coexpression of genes expressed in the extraembryonic membranes and the corresponding endometrium on both gestation days. Both the transcriptional dysregulation that exists in the conceptus or endometrium independently and the rewiring of gene transcription between the conceptus and endometrium are a potential component of the mechanisms that contribute to pregnancy losses caused by in vitro production of embryos.

Single-cell transcriptomic characterization of sheep conceptus elongation and implantation

Bidirectional communication between the developing conceptus and endometrium is essential for pregnancy recognition and establishment in ruminants. We dissect the transcriptomic dynamics of sheep conceptus and corresponding endometrium at pre- and peri-implantation stages using single-cell RNA sequencing. Spherical blastocysts contain five cell types, with 68.62% trophectoderm cells. Strikingly, elongated conceptuses differentiate into 17 cell types, indicating dramatic cell fate specifications. Cell-type-specific gene expression delineates the features of distinctive trophectoderm lineages and indicates that the transition from polar trophectoderm to trophoblast increases interferon-tau expression and likely drives elongation initiation. We identify 13 endometrium-derived cell types and elucidate their molecular responses to conceptus development. Integrated analyses uncover multiple paired transcripts mediating the dialogues between extraembryonic membrane and endometrium, including IGF2-IGF1R, FGF19-FGFR1, NPY-NPY1R, PROS1-AXL, and ADGRE5-CD55. These data provide insight into the molecular regulation of conceptus elongation and represent a valuable resource for functional investigations of pre- and peri-implantation ruminant development.

PIK3CA mutation in endometriotic epithelial cells promotes viperin-dependent inflammatory response to insulin

Endometrial epithelia are known to harbor cancer driver mutations in the absence of any pathologies, including mutations in PIK3CA. Insulin plays an important role in regulating uterine metabolism during pregnancy, and hyperinsulinemia is associated with conditions impacting fertility. Hyperinsulinemia also promotes cancer, but the direct action of insulin on mutated endometrial epithelial cells is unknown. Here, we treated 12Z endometriotic epithelial cells carrying the PIK3CAH1047R oncogene with insulin and examined transcriptomes by RNA-seq. While cells naively responded to insulin, the magnitude of differential gene expression (DGE) was nine times greater in PIK3CAH1047R cells, representing a synergistic effect between insulin signaling and PIK3CAH1047R expression. Interferon signaling and the unfolded protein response (UPR) were enriched pathways among affected genes. Insulin treatment in wild-type cells activated normal endoplasmic reticulum stress (ERS) response programs, while PIK3CAH1047R cells activated programs necessary to avoid ERS-induced apoptosis. PIK3CAH1047R expression alone resulted in overexpression (OE) of Viperin (RSAD2), which is involved in viral response and upregulated in the endometrium during early pregnancy. The transcriptional changes induced by insulin in PIK3CAH1047R cells were rescued by knockdown of Viperin, while Viperin OE alone was insufficient to induce a DGE response to insulin, suggesting that Viperin is necessary but not sufficient for the synergistic effect of PIK3CAH1047R and insulin treatment. We identified interferon signaling, viral response, and protein targeting pathways that are induced by insulin but dependent on Viperin in PIK3CAH1047R mutant cells. These results suggest that response to insulin signaling is altered in mutated endometriotic epithelial cells.

Review: Implantation and placentation in ruminants

Ruminants have a unique placenta in comparison to other mammalian species. Initially, they possess a non-invasive epitheliochorial type of placenta during conceptus elongation. As the conceptus trophectoderm begins to attach to the luminal epithelium (LE) of the endometrium, binucleate cells (BNCs) develop within the trophoblast of the chorion. The BNCs migrate and fuse with the uterine LE to form multinucleate syncytial plaques in sheep and hybrid trinucleate cells in cattle. This area of the ruminant placenta is semi-invasive synepitheliochorial. The BNCs form the foundation of the placental cotyledons and express unique placenta-specific genes including pregnancy-associated glycoproteins and chorionic somatomammotropin hormone 2 or placental lactogen. Attachment and interdigitation of cotyledons into endometrial caruncles form placentomes that are subsequently vascularized to provide essential nutrients for growth of the fetus. This chapter review will discuss historical and current aspects of conceptus implantation and placenta development in ruminant ungulates with a focus on cattle and sheep. Single-cell analysis promises to provide a much more detailed understanding of the different cell populations and insights into pathways mediating trophoblast and placenta. This fundamental is required to understand pregnancy loss and develop strategies to improve pregnancy outcomes in ruminants.

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.

A burst of genomic innovation at the origin of placental mammals mediated embryo implantation

The origin of embryo implantation in mammals ~148 million years ago was a dramatic shift in reproductive strategy, yet the molecular changes that established mammal implantation are largely unknown. Although progesterone receptor signalling predates the origin of mammals and is highly conserved in, and critical for, successful mammal pregnancy, it alone cannot explain the origin and subsequent diversity of implantation strategies throughout the placental mammal radiation. MiRNAs are known to be flexible and dynamic regulators with a well-established role in the pathophysiology of mammal placenta. We propose that a dynamic core microRNA (miRNA) network originated early in placental mammal evolution, responds to conserved mammal pregnancy cues (e.g. progesterone), and facilitates species-specific responses. Here we identify 13 miRNA gene families that arose at the origin of placental mammals and were subsequently retained in all descendent lineages. The expression of these miRNAs in response to early pregnancy molecules is regulated in a species-specific manner in endometrial epithelia of species with extreme implantation strategies (i.e. bovine and human). Furthermore, this set of miRNAs preferentially target proteins under positive selective pressure on the ancestral eutherian lineage. Discovery of this core embryo implantation toolkit and specifically adapted proteins helps explain the origin and evolution of implantation in mammals.

Interferon-τ -induced ISG15-AS regulates endometrial receptivity during early goat pregnancy

Endometrial receptivity is a critical process for the successful establishment of pregnancy in ruminants. However, the biological role of long non-coding RNAs (lncRNAs) in the development of endometrial receptivity is poorly understood. In this study, we performed RNA-seq analysis of immortalised goat endometrial epithelial cells (gEECs) treated with interferon-τ (IFNT). Transcriptome profiles showed that 8069 high-confidence putative lncRNAs, including 6498 intronic lncRNA transcripts, 1078 lincRNAs and 493 antisense lncRNAs were identified in gEECs with or without IFNT treatment. Functional clustering analysis was performed by using cis and trans lncRNAs prediction. GO and KEGG analyses revealed that differentially expressed lncRNAs may regulate tissue remodelling and immune responses. Subsequently, six of the 21 differentially expressed antisense lncRNAs were validated using qRT-PCR. Through functional screening and co-expression analysis of lncRNAs in gEECs, we identified that ISG15-AS was mainly expressed in the luminal and glandular epithelium on days 5 and 15 and was strongly upregulated on day 18 of pregnancy in vivo. Similarly, ISG15-AS was abundant in the nucleus and cytoplasm, and was significantly upregulated after treatment with IFNT in gEECs. In addition, ISG15 is an IFNT-responsive gene, that displayed an evident increase in vivo and in vitro. Moreover, sense ISG15 was significantly upregulated following ISG15-AS silencing. The key genes related to ISGylation and endometrial receptivity in gEECs dramatically increased after ISG15-AS inhibition. Collectively, our results indicate that a novel antisense lncRNA, ISG15-AS, may be important in regulating endometrial receptivity through ISGylation.

USP18 promotes endometrial receptivity via the JAK/STAT1 and the ISGylation pathway

Interferon-tau (IFNT), a pregnancy recognition signal in ruminants, promotes the establishment of endometrial receptivity by inducing the expression of interferon-stimulated genes (ISGs) via the Janus kinase/signal transducer and activator of transcription (JAK/STATs) signaling pathway. However, the precise mechanisms remain largely unknown. Ubiquitin-specific protease 18 (USP18) acts specifically on the ISGylation modification system to exert deubiquitination and participates in the regulation of the type I IFN signaling pathway. The purpose of this study was to determine the role and mechanism of USP18 on endometrial receptivity in goat. USP18 was mainly localized in the uterine luminal and glandular epithelium, and its expression levels were significantly increased from days 5-18 of early pregnancy. Progesterone (P₄), estradiol (E₂), and IFNT significantly stimulated USP18 expression in goat endometrial epithelial cells (gEECs) cultured in vitro. Meanwhile, the markers of endometrial receptivity HOXA11, ITGB1, ITGB3, and ITGB5 were significantly upregulated after USP18 overexpression in gEECs. However, USP18 interference significantly inhibited the expression of HOXA10, ITGB1, ITGB3, and ITGB5 in gEECs. In addition, both the phosphorylation levels of STAT1 and the expression of ISGylation-modified proteins were significantly increased after USP18 silencing in gEECs. Furthermore, pretreatment with the STAT1 inhibitor Fludara markedly restored the effect of USP18 interference in gEECs. In summary, USP18 may play an important role in promoting goat endometrial receptivity by regulating the JAK/STAT1 pathway and ISGylation.

Administration of Beta-Nerve Growth Factor during the Preovulatory Stage Improves Endocrine and Luteal Function in Dairy Heifers

The neurotrophin beta-nerve growth factor (NGF), which is present in the semen of different mammals, elicits potent ovulatory and luteotrophic actions in llamas following systemic administration. Here, we determine if purified NGF given intramuscularly (IM) during the preovulatory stage affects the corpus luteum (CL), hormone production, endometrial gene expression, and pregnancy rate of dairy heifers. Holstein-Friesian heifers were estrus-synchronized using estradiol benzoate (EB) plus an intravaginal progesterone (P4) device (DIB). After eight days, the device was removed and cloprostenol was given IM; the next day (day 9), heifers received EB IM plus one of the following: (i) 1 mg of NGF (NGF D9 group), (ii) 1 mg of NGF 32 h after EB (NGF D10 group), or (iii) phosphate buffer saline (control group). To measure pregnancy rates, heifers were treated similarly, then artificially inseminated with sexed semen 48–52 h after DIB removal, then an ultrasound was conducted 30 days after insemination. The females given NGF along with EB (NGF D9) showed significantly higher luteinizing hormone (LH) concentrations, larger CL vascular areas, and higher plasma P4 concentrations than the NGF D10 and control animals. Downregulation of the P4 receptor (PGR), and upregulation of both lipoprotein lipase (LPL) and Solute Carrier Family 6 member 14 (SLC6A14) endometrial genes, were detected in NGF D9 heifers. Furthermore, these heifers had a 10% higher pregnancy rate than the control group. We conclude that the higher P4 output, in response to the early NGF administration, led to the enhanced gene expression of transcripts related to uterine receptivity that may result in enhanced pregnancy rates.

Machine-learning methods applied to integrated transcriptomic data from bovine blastocysts and elongating conceptuses to identify genes predictive of embryonic competence

Early pregnancy loss markedly impacts reproductive efficiency in cattle. The objectives were to model a biologically relevant gene signature predicting embryonic competence for survival after integrating transcriptomic data from blastocysts and elongating conceptuses with different developmental capacities and to validate the potential biomarkers with independent embryonic data sets through the application of machine-learning algorithms. First, two data sets from in vivo-produced blastocysts competent or not to sustain a pregnancy were integrated with a data set from long and short day-15 conceptuses. A statistical contrast determined differentially expressed genes (DEG) increasing in expression from a competent blastocyst to a long conceptus and vice versa; these were enriched for KEGG pathways related to glycolysis/gluconeogenesis and RNA processing, respectively. Next, the most discriminative DEG between blastocysts that resulted or did not in pregnancy were selected by linear discriminant analysis. These eight putative biomarker genes were validated by modeling their expression in competent or noncompetent blastocysts through Bayesian logistic regression or neural networks and predicting embryo developmental fate in four external data sets consisting of in vitro-produced blastocysts (i) competent or not, or (ii) exposed or not to detrimental conditions during culture, and elongated conceptuses (iii) of different length, or (iv) developed in the uteri of high- or subfertile heifers. Predictions for each data set were more than 85% accurate, suggesting that these genes play a key role in embryo development and pregnancy establishment. In conclusion, this study integrated transcriptomic data from seven independent experiments to identify a small set of genes capable of predicting embryonic competence for survival.

MSX1 Regulates Goat Endometrial Function by Altering the Plasma Membrane Transformation of Endometrial Epithelium Cells during Early Pregnancy

MSX1 is an important member of the muscle segment homeobox gene (Msh) family and acts as a transcription factor to regulate tissue plasticity, yet its role in goat endometrium remodeling remains elusive. In this study, an immunohistochemical analysis showed that MSX1 was mainly expressed in the luminal and glandular epithelium of goat uterus, and the MSX1 expression was upregulated in pregnancy at days 15 and 18 compared with pregnancy at day 5. In order to explore its function, goat endometrial epithelial cells (gEECs) were treated with 17 β-estrogen (E₂), progesterone (P₄), and/or interferon-tau (IFNτ), which were used to mimic the physiological environment of early pregnancy. The results showed that MSX1 was significantly upregulated with E₂- and P₄-alone treatment, or their combined treatment, and IFNτ further enhanced its expression. The spheroid attachment and PGE2/PGF2α ratio were downregulated by the suppression of MSX1. The combination of E₂, P₄, and IFNτ treatment induced the plasma membrane transformation (PMT) of gEECs, which mainly showed the upregulation of N-cadherin (CDH2) and concomitant downregulation of the polarity-related genes (ZO-1, α-PKC, Par3, Lgl2, and SCRIB). The knockdown of MSX1 partly hindered the PMT induced by E₂, P₄, and IFNτ treatment, while the upregulation of CDH2 and the downregulation of the partly polarity-related genes were significantly enhanced when MSX1 was overexpressed. Moreover, MSX1 regulated the CDH2 expression by activating the endoplasmic reticulum (ER) stress-mediated unfolded protein response (UPR) pathway. Collectively, these results suggest that MSX1 was involved in the PMT of the gEECs through the ER stress-mediated UPR pathway, which affects endometrial adhesion and secretion function.

Embryo-Uterine Cross-Talk: Exploration of the Immunomodulatory Mechanism in Buffalo

Understanding the molecular cross-talk between the embryo and uterine endometrium is crucial for the improvement of IVF outcomes. The present work was undertaken to investigate the effect of pre-implantation embryo on the expression profile of immune-related genes in uterine epithelial cells (UECs) and PBMCs in buffalo. UECs were isolated from slaughterhouse-derived non-gravid uteri, cultured ex vivo and characterized, and buffalo embryos were produced in vitro from slaughterhouse-derived ovaries. Embryos co-cultured with steroid-treated UECs significantly stimulated (p < 0.05) the relative mRNA abundance of PTGS2, ISG15, OAS1, MX2, IFNAR1 and IFNAR2 in UECs while they significantly suppressed the mRNA expression of NFkβIA, NFkβ2, TNFα and IL1B, with no significant change in TGFβ1 and IL10 in the co-culture of embryos with UECs. In vitro treatment of PBMCs with conditioned media (CM) derived from embryos as well as UEC−embryo co-culture upregulated the mRNA abundance of ISG15, TGFβ1, PTGS2OAS1, MX2 and STAT1 while it downregulated IL17 and TNFα expression. The expression of IFNAR1 and IFNAR2 was elevated in PBMCs cultured in embryo-derived CM, but there was no significant change in PBMCs cultured in UEC−embryo co-culture CM. Thus, it can be concluded that the developing embryo and its secretions modulate the expression of immune responses by inducing an anti-inflammatory action in uterine epithelial cells for acceptance of the semi-allogenic embryo in the uterus to sustain pregnancy in buffalo.

Expression Profiling of Circular RNAs in Early Pregnant Jianghuai Buffaloes

Simple Summary

CircRNA transcriptome sequencing technology is widely used in the study of germ-line stem cell proliferation and differentiation and early embryonic development, but the research on early pregnancy diagnosis in female animals is still in the preliminary stage, and the specific regulatory mechanism has not been reported. Here, we identified numerous differentially expressed circRNAs (DECs) in the venous blood of the distinctive local breed of Chinese Jianghuai buffalo. Analysis of the enrichment showed that DECs were mainly enriched in the epidermal growth factor receptor-signaling pathway that is important for embryonic development and pregnancy maintenance. These findings have provided a better understanding of buffalo pregnancy establishment and a potential basis for improving early pregnancy diagnosis techniques in buffalo.

Abstract

Circular RNA (circRNA) is expressed in cells and tissues of several species. However, the expression of circRNAs in the blood of Jianghuai buffaloes during early pregnancy has not been reported. In this study, we identified the DECs in the blood of Jianghuai buffaloes and annotated the functions of these DECs. The results showed that there were 890 DECs between the pregnant and non-pregnant groups, of which more than 80% were exon-derived circRNAs, including 323 up-regulated circRNAs and 567 down-regulated circRNAs. Enrichment analysis revealed that DECs were mainly enriched in the epidermal growth factor receptor-signaling pathway important for embryonic development and pregnancy maintenance. In addition, most DECs have multiple miRNA targets, suggesting that these DECs have the potential to function as miRNA sponges. In conclusion, several DECs are present between pregnant and non-pregnant Jianghuai buffaloes, and these DECs are associated with embryo implantation and pregnancy establishment.

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.

Form of dietary selenium affects mRNA encoding interferon-stimulated and progesterone-induced genes in the bovine endometrium and conceptus length at maternal recognition of pregnancy

Widespread regions of the southeast United States have soils, and hence forages, deficient in selenium (Se), necessitating Se supplementation to grazing cattle for optimal immune function, growth, and fertility. We have reported that supplementation with an isomolar 1:1 mix (MIX) of inorganic (ISe) and organic (OSe) forms of Se increases early luteal phase (LP) concentrations of progesterone (P4) above that in cows on ISe or OSe alone. Increased early LP P4 advances embryonic development. Our objective was to determine the effects of the form of Se on the development of the bovine conceptus and the endometrium using targeted real-time PCR (qPCR) on day 17 of gestation, the time of maternal recognition of pregnancy (MRP). Angus-cross yearling heifers underwent 45-d Se-depletion then repletion periods, then at least 90 d of supplementation (TRT) with 35 ppm Se per day as either ISe (n = 10) or MIX (n = 10). Heifers were inseminated to a single sire after detected estrus (day 0). On day 17 of gestation, caruncular (CAR) and intercaruncular (ICAR) endometrial samples and the developing conceptus were recovered from pregnant heifers (ISe, n = 6 and MIX, n = 6). qPCR was performed to determine the relative abundance of targeted transcripts in CAR and ICAR samples, with the expression data subjected to one-way ANOVA to determine TRT effects. The effect of TRT on conceptus development was analyzed using a one-tailed Student's t-test. When compared with ISe-treated heifers, MIX heifers had decreased (P < 0.05) abundance of several P4-induced and interferon-stimulated mRNA transcripts, including IFIT3, ISG15, MX1, OAS2, RSAD2, DGAT2, FGF2 in CAR and DKK1 in ICAR samples and tended (P ≤ 0.10) to have decreased mRNA abundance of IRF1, IRF2, FOXL2, and PGR in CAR samples, and HOXA10 and PAQR7 in ICAR samples. In contrast, MIX-supplemented heifers had increased (P < 0.05) mRNA abundance of MSTN in ICAR samples and an increase in conceptus length (ISe: 17.45 ± 3.08 cm vs. MIX: 25.96 ± 3.95 cm; P = 0.05). Notably, myostatin increases glucose secretion into histotroph and contributes to advanced conceptus development. This advancement in conceptus development occurred in the presence of similar concentrations of serum P4 (P = 0.88) and whole blood Se (P = 0.07) at MRP.

Constraint-Based, Score-Based and Hybrid Algorithms to Construct Bayesian Gene Networks in the Bovine Transcriptome

Simple Summary

In this study, we investigated and compared six different Bayesian network algorithms from three different categories to identify hub genes critical to gene expression networks activated in response to progesterone in the bovine uterus. We observed many common hub genes identified between constraint-based algorithms (CBAs) and hybrid algorithms (HAs), while it appeared that score-based algorithm (SBA) methods led to more accurate and relevant predictions of core genes. The results revealed that the identification of hub genes was affected by the type of network reconstruction and by the subsequently used topological parameters. Two identified genes known to have roles during pregnancy are ISG15 and DGAT2. The identified hub genes are associated with biological processes such as amino acid metabolism, hormonal signaling pathways and the immune system. Our analysis revealed a role for miRNAs in the regulation of this system. The biological and physiological roles (enzymatic and hormonal effects) of unannotated identified hub genes should be functionally validated by further studies.

Abstract

Bayesian gene networks are powerful for modelling causal relationships and incorporating prior knowledge for making inferences about relationships. We used three algorithms to construct Bayesian gene networks around genes expressed in the bovine uterus and compared the efficacies of the algorithms. Dataset GSE33030 from the Gene Expression Omnibus (GEO) repository was analyzed using different algorithms for hub gene expression due to the effect of progesterone on bovine endometrial tissue following conception. Six different algorithms (grow-shrink, max-min parent children, tabu search, hill-climbing, max-min hill-climbing and restricted maximum) were compared in three higher categories, including constraint-based, score-based and hybrid algorithms. Gene network parameters were estimated using the bnlearn bundle, which is a Bayesian network structure learning toolbox implemented in R. The results obtained indicated the tabu search algorithm identified the highest degree between genes (390), Markov blankets (25.64), neighborhood sizes (8.76) and branching factors (4.38). The results showed that the highest number of shared hub genes (e.g., proline dehydrogenase 1 (PRODH), Sam-pointed domain containing Ets transcription factor (SPDEF), monocyte-to-macrophage differentiation associated 2 (MMD2), semaphorin 3E (SEMA3E), solute carrier family 27 member 6 (SLC27A6) and actin gamma 2 (ACTG2)) was seen between the hybrid and the constraint-based algorithms, and these genes could be recommended as central to the GSE33030 data series. Functional annotation of the hub genes in uterine tissue during progesterone treatment in the pregnancy period showed that the predicted hub genes were involved in extracellular pathways, lipid and protein metabolism, protein structure and post-translational processes. The identified hub genes obtained by the score-based algorithms had a role in 2-arachidonoylglycerol and enzyme modulation. In conclusion, different algorithms and subsequent topological parameters were used to identify hub genes to better illuminate pathways acting in response to progesterone treatment in the bovine uterus, which should help with our understanding of gene regulatory networks in complex trait expression.

Culture of endometrial epithelial cells collected by a cytological brush in vivo

In cattle, mechanistic studies of endometrial function rely on cell lines or primary culture of cells harvested postmortem. Understanding the endometrial physiology in dairy cows is essential, because approximately 50% of pregnancies are lost in the first 3 wk of gestation for unknown reasons. The objective was to validate an in vivo, minimally invasive, and estrous cycle stage-specific method to obtain endometrial luminal epithelial cells for culture. The uterine body of 26 cows was sampled using a cytology brush (cytobrush) 4 d after estrus. The viability of cells was measured by flow cytometry (80% live cells) and epithelial identity was determined by anti-vimentin and anti-cytokeratin immunofluorescence and quantitative PCR for KRT18 and VIM. A pool of cells from 15 animals was passaged 4 times in culture until confluent and then treated with 0, 0.1, 1, or 10 ng/mL of recombinant bovine interferon-tau (rbIFN-τ). The relative expression of transcripts related to IFN-τ signaling (IFNAR1), early (IRF2) and late (ISG15, OAS1) response to IFN-τ stimulus, and other IFN-τ-stimulated genes (CCL8, CXCL10, and FABP3) was measured by quantitative PCR. The relative expression of KRT18 transcripts was similar across passages; the relative expression of VIM increased at passage 2, and IFNAR1 transcripts decreased in cultured compared with that in fresh cells. The relative expression of ISG15, OAS1, CCL8, and FABP3 increased in response to rbIFN-τ. In conclusion, culture of endometrial luminal cells collected by cytobrush was feasible, generating a monolayer enriched in epithelial cells, and therefore constitutes a novel model by which to study endometrial luminal epithelial cell function, including responses to IFN-τ.

Implantation and Placentation in Ruminants

In comparison to many other mammalian species, ruminant ungulates have a unique form of placentation. Ruminants initially display an epitheliochorial type of placentation; however, during the period of placental attachment, trophoblast giant binucleate cells (BNC) develop within the chorion to migrate and fuse with the uterine surface epithelium to form syncytial plaques. Binucleate cell migration and fusion continues throughout pregnancy but never appears to breach the basal lamina, beneath the uterine surface or luminal epithelium. Therefore, the semi-invasive type of placentation in ruminants is classified as synepitheliochorial. The endometrium of ruminant species also contains unique specialized aglandular structures termed "caruncles" in which the chorioallantois (cotyledons) interdigitates and forms highly vascularized fetal-maternal "placentomes." This chapter will discuss the current knowledge of early conceptus development during the peri-attachment period, establishment of pregnancy, conceptus attachment, and placentation in ruminant ungulates. The features of placentomes, BNCs, fetomaternal hybrid cells, and multinucleated syncytial plaques of the cotyledonary placenta of ruminant species will be reviewed to highlight the unique form of placentation compared to the placentae of other artiodactyls.

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.

Role of reproductive fluids and extracellular vesicles in embryo&#x2013;maternal interaction during early pregnancy in cattle

The coordinated interaction between the developing embryo and the maternal reproductive tract is essential for the establishment and maintenance of pregnancy in mammals. An early cross-talk is established between the oviduct/uterus and the gametes and embryo. This dialogue will shape the microenvironment in which gamete transport, fertilisation, and early embryonic development occur. Due to the small size of the gametes and the early embryo relative to the volume of the oviductal and uterine lumina, collection of tissue and fluid adjacent to these cells is challenging in cattle. Thus, the combination of in vivo and in vitro models seems to be the most appropriate approach to better understand this fine dialogue. In this respect, the aim of this review is to summarise the recent findings in relation to gamete/embryo-maternal interaction during the pre-elongation period.

Genome-wide association study on milk production and somatic cell score for Thai dairy cattle using weighted single-step approach with random regression test-day model

Genome-wide association studies are a powerful tool to identify genomic regions and variants associated with phenotypes. However, only limited mutual confirmation from different studies is available. The objectives of this study were to identify genomic regions as well as genes and pathways associated with the first-lactation milk, fat, protein, and total solid yields; fat, protein, and total solid percentage; and somatic cell score (SCS) in a Thai dairy cattle population. Effects of SNPs were estimated by a weighted single-step GWAS, which back-solved the genomic breeding values predicted using single-step genomic BLUP (ssGBLUP) fitting a single-trait random regression test-day model. Genomic regions that explained at least 0.5% of the total genetic variance were selected for further analyses of candidate genes. Despite the small number of genotyped animals, genomic predictions led to an improvement in the accuracy over the traditional BLUP. Genomic predictions using weighted ssGBLUP were slightly better than the ssGBLUP. The genomic regions associated with milk production traits contained 210 candidate genes on 19 chromosomes [Bos taurus autosome (BTA) 1 to 7, 9, 11 to 16, 20 to 21, 26 to 27 and 29], whereas 21 candidate genes on 3 chromosomes (BTA 11, 16, and 21) were associated with SCS. Many genomic regions explained a small fraction of the genetic variance, indicating polygenic inheritance of the studied traits. Several candidate genes coincided with previous reports for milk production traits in Holstein cattle, especially a large region of genes on BTA14. We identified 141 and 5 novel genes related to milk production and SCS, respectively. These novel genes were also found to be functionally related to heat tolerance (e.g., SLC45A2, IRAG1, and LOC101902172), longevity (e.g., SYT10 and LOC101903327), and fertility (e.g., PAG1). These findings may be attributed to indirect selection in our population. Identified biological networks including intracellular cell transportation and protein catabolism implicate milk production, whereas the immunological pathways such as lymphocyte activation are closely related to SCS. Further studies are required to validate our findings before exploiting them in genomic selection.

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.

Characterization of local and peripheral immune system in pregnant and nonpregnant ewes

Modulation of the immune system is known to be important for successful pregnancy but how immune function might differ between the lymph nodes draining the reproductive tract and peripheral lymph nodes is not well understood. Additionally, if immune system changes in response to the presence of an embryo during early pregnancy, and if this response differs in local versus peripheral immune tissue, has not been well characterized. To address these questions, we examined expression of genes important for immune function using NanoString technology in the ampulla and isthmus of the oviduct, endometrium, lymph nodes draining the reproductive tract (lumbo-aortic and medial iliac) as well as a peripheral lymph node (axillary), the spleen, and circulating immune cells from ewes on day 5 of the estrous cycle or pregnancy. Concentrations of estradiol and progesterone in plasma were also determined. Principal component analysis revealed separation of the local from the peripheral lymph nodes (MANOVA P = 3.245e-08, R2 = 0.3) as well as separation of tissues from pregnant and nonpregnant animals [lymph nodes (MANOVA P = 2.337e-09, R2 = 0.5), reproductive tissues (MANOVA P = 2.417e-14, R2 = 0.47)]. Nine genes were differentially (FDR < 0.10) expressed between lymph node types, with clear difference in expression of these genes between the lumbo-aortic and axillary lymph nodes. Expression of these genes in the medial iliac lymph node was not consistently different to either the axillary or the lumbo-aortic lymph node. Expression of IL10RB was increased (FDR < 0.05) by 24% in the reproductive tissue of the pregnant animals compared to nonpregnant animals. Analysis of gene categories revealed that expression of genes of the T-cell receptor pathway in reproductive tract tissues was associated (P < 0.05) with pregnancy status. In conclusion, assessment of gene expression of reproductive and immune tissue provides evidence for a specialization of the local immune system around the reproductive tract potentially important for successful establishment of pregnancy. Additionally, differences in gene expression patterns in reproductive tissue from pregnant and nonpregnant animals could be discerned as early as day 5 of pregnancy. This was found to be associated with expression of genes important for T-cell function and thus highlights the important role of these cells in early pregnancy.

The effect of bta-miR-26b in intrauterine extracellular vesicles on maternal immune system during the implantation period

Extracellular vesicles (EVs) in utero play a role in cellular interactions between endometrium-conceptuses (embryo plus extraembryonic membranes) during peri-implantation periods. However, how intrauterine EVs function on endometrium have not been well characterized. In our previous study, bta-miR-98 found in intrauterine EVs from uterine flushing fluids (UFs) on pregnant day 20 (a half day after initial conceptus attachment, P20) could regulate the maternal immune system and collaborate with other miRNAs and/or components of EVs for conceptus implantation. We, therefore, hypothesized that in addition to bta-miR-98, other miRNAs present in bovine intrauterine EVs may regulate the maternal immune system in the endometrial epithelium. A global analysis of differentially expressed proteins between EVs from P17 and P20 UFs revealed that components of intrauterine P20 EVs had the effect on the down-regulation of "neutrophil activation involved in immune response" and "neutrophil mediated immunity". In silico analyses predicted bta-miR-26b as one of potential miRNA to regulate maternal immune system. In our cell culture experiments, bta-miR-26b negatively regulated several immune system-related genes PSMC6, CD40, and IER3 in bovine endometrial epithelial cells. Our findings revealed that intrauterine EV-derived bta-miR-26b contributes to the down-regulation of the maternal immune system, allowing conceptus implantation to the uterine endometrium. Furthermore, our results suggest that intrauterine EVs extracted from P20 UFs could regulate neutrophils, the first line of immunological defense, to modulate endometrial immune and inflammatory responses for implanting conceptuses.

Loop-mediated isothermal amplification (LAMP) and machine learning application for early pregnancy detection using bovine vaginal mucosal membrane

An early and accurate pregnancy diagnosis method is required to improve the reproductive performance of cows. Here we developed an easy pregnancy detection method using vaginal mucosal membrane (VMM) with application of Reverse Transcription-Loop-mediated Isothermal Amplification (RT-LAMP) and machine learning. Cows underwent artificial insemination (AI) on day 0, followed by VMM-collection on day 17-18, and pregnancy diagnosis by ultrasonography on day 30. By RNA sequencing of VMM samples, three candidate genes for pregnancy markers (ISG15 and IFIT1: up-regulated, MUC16: down-regulated) were selected. Using these genes, we performed RT-LAMP and calculated the rise-up time (RUT), the first-time absorbance exceeded 0.05 in the reaction. We next determined the cutoff value and calculated accuracy, sensitivity, specificity, positive prediction value (PPV), and negative prediction value (NPV) for each marker evaluation. The IFIT1 scored the best performance at 92.5% sensitivity, but specificity was 77.5%, suggesting that it is difficult to eliminate false positives. We then developed a machine learning model trained with RUT of each marker combination to predict pregnancy. The model created with the RUT of IFIT1 and MUC16 combination showed high specificity (86.7%) and sensitivity (93.3%), which were higher compared to IFIT1 alone. In conclusion, using VMM with RT-LAMP and machine learning algorithm can be used for early pregnancy detection before the return of first estrus.

Analysis of the transcriptome of bovine endometrial cells isolated by laser micro-dissection (1): specific signatures of stromal, glandular and luminal epithelial cells

BACKGROUND

A number of studies have examined mRNA expression profiles of bovine endometrium at estrus and around the peri-implantation period of pregnancy. However, to date, these studies have been performed on the whole endometrium which is a complex tissue. Consequently, the knowledge of cell-specific gene expression, when analysis performed with whole endometrium, is still weak and obviously limits the relevance of the results of gene expression studies. Thus, the aim of this study was to characterize specific transcriptome of the three main cell-types of the bovine endometrium at day-15 of the estrus cycle.

RESULTS

In the RNA-Seq analysis, the number of expressed genes detected over 10 transcripts per million was 6622, 7814 and 8242 for LE, GE and ST respectively. ST expressed exclusively 1236 genes while only 551 transcripts were specific to the GE and 330 specific to LE. For ST, over-represented biological processes included many regulation processes and response to stimulus, cell communication and cell adhesion, extracellular matrix organization as well as developmental process. For GE, cilium organization, cilium movement, protein localization to cilium and microtubule-based process were the only four main biological processes enriched. For LE, over-represented biological processes were enzyme linked receptor protein signaling pathway, cell-substrate adhesion and circulatory system process.

CONCLUSION

The data show that each endometrial cell-type has a distinct molecular signature and provide a significantly improved overview on the biological process supported by specific cell-types. The most interesting result is that stromal cells express more genes than the two epithelial types and are associated with a greater number of pathways and ontology terms.

Analysis of Transcripts of Uncertain Coding Potential Using RNA Sequencing During the Preattachment Phase in Goat Endometrium

Transcripts of uncertain coding potential (TUCP) are part of long noncoding RNAs, which include short open reading frames and could be translated into small peptides. In recent years, a growing number of TUCPs has been implicated in multiple biological activities, such as embryogenesis and transcriptional regulation. However, the abundance of TUCPs and their roles in goat endometrium during pregnancy recognition (day 16) remain undocumented. In this study, bioinformatics analyses were conducted to identify the differentially expressed (DE) TUCPs between pregnant animals and corresponding nonpregnant controls. A total of 5551 TUCPs were identified; 114 TUCPs were DE in goat endometrium, of which 74 TUCPs were upregulated in pregnant endometrium, whereas 40 TUCPs were downregulated. The related genes of TUCP were predicted by using coexpression and colocalization methods. In summary, 419 genes were predicted by colocalization, and 9464 genes were predicted by coexpression. The kyoto encyclopedia of genes and genomes (KEGG) and gene ontology (GO) analysis showed that TUCPs, which are highly expressed in pregnant endometrium, were mainly associated with endometrial remodeling, nutrient synthesis, and transportation. However, TUCPs that were lowly expressed in pregnant endometrium were mainly associated with immune tolerance, which is necessary for the protection and development of the embryo in the uterus. These findings may be used for the comparative analysis of TUCP transcripts in endometrium and assist in the selection of applicable candidate genes associated with embryo implantation for further functional analyses.

Oocyte maturation under lipotoxic conditions induces carryover transcriptomic and functional alterations during post-hatching development of good-quality blastocysts: novel insights from a bovine embryo-transfer model

STUDY QUESTION

Does oocyte maturation under lipolytic conditions have detrimental carry-over effects on post-hatching embryo development of good-quality blastocysts after transfer?

SUMMARY ANSWER

Surviving, morphologically normal blastocysts derived from bovine oocytes that matured under lipotoxic conditions exhibit long-lasting cellular dysfunction at the transcriptomic and metabolic levels, which coincides with retarded post-hatching embryo development.

WHAT IS KNOWN ALREADY

There is increasing evidence showing that following maturation in pathophysiologically relevant lipotoxic conditions (as in obesity or metabolic syndrome), surviving blastocysts of good (transferable) morphological quality have persistent transcriptomic and epigenetic alteration even when in vitro embryo culture takes place under standard conditions. However, very little is known about subsequent development in the uterus after transfer.

STUDY DESIGN, SIZE, DURATION

Bovine oocytes were matured in vitro in the presence of pathophysiologically relevant, high non-esterified fatty acid (NEFA) concentrations (HIGH PA), or in basal NEFA concentrations (BASAL) as a physiological control. Eight healthy multiparous non-lactating Holstein cows were used for embryo transfers. Good-quality blastocysts (pools of eight) were transferred per cow, and cows were crossed over for treatments in the next replicate. Embryos were recovered 7 days later and assessed for post-hatching development, phenotypic features and gene expression profile. Blastocysts from solvent-free and NEFA-free maturation (CONTROL) were also tested for comparison.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Recovered Day 14 embryos were morphologically assessed and dissected into embryonic disk (ED) and extraembryonic tissue (EXT). Samples of EXT were cultured for 24 h to assess cellular metabolic activity (glucose and pyruvate consumption and lactate production) and embryos' ability to signal for maternal recognition of pregnancy (interferon-τ secretion; IFN-τ). ED and EXT samples were subjected to RNA sequencing to evaluate the genome-wide transcriptome patterns.

MAIN RESULTS AND THE ROLE OF CHANCE

The embryo recovery rate at Day 14 p.i. was not significantly different among treatment groups (P > 0.1). However, higher proportions of HIGH PA embryos were retarded in growth (in spherical stage) compared to the more elongated tubular stage embryos in the BASAL group (P < 0.05). Focusing on the normally developed tubular embryos in both groups, HIGH PA exposure resulted in altered cellular metabolism and altered transcriptome profile particularly in pathways related to redox-regulating mechanisms, apoptosis, cellular growth, interaction and differentiation, energy metabolism and epigenetic mechanisms, compared to BASAL embryos. Maturation under BASAL conditions did not have any significant effects on post-hatching development and cellular functions compared to CONTROL.

LARGE-SCALE DATA

The datasets of RNA sequencing analysis are available in the NCBI's Gene Expression Omnibus (GEO) repository, series accession number GSE127889 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE127889). Datasets of differentially expressed genes and their gene ontology functions are available in the Mendeley datasets at http://dx.doi.org/10.17632/my2z7dvk9j.2.

LIMITATIONS, REASONS FOR CAUTION

The bovine model was used here to allow non-invasive embryo transfer and post-hatching recovery on Day 14. There are physiological differences in some characteristics of post-hatching embryo development between human and cows, such as embryo elongation and trophoblastic invasion. However, the main carry-over effects of oocyte maturation under lipolytic conditions described here are evident at the cellular level and therefore may also occur during post-hatching development in other species including humans. In addition, post-hatching development was studied here under a healthy uterine environment to focus on carry-over effects originating from the oocyte, whereas additional detrimental effects may be induced by maternal metabolic disorders due to adverse changes in the uterine microenvironment. RNA sequencing results were not verified by qPCR, and no solvent control was included.

WIDER IMPLICATIONS OF THE FINDINGS

Our observations may increase the awareness of the importance of maternal metabolic stress at the level of the preovulatory oocyte in relation to carry-over effects that may persist in the transferrable embryos. It should further stimulate new research about preventive and protective strategies to optimize maternal metabolic health around conception to maximize embryo viability and thus fertility outcome.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Flemish Research Fund (FWO grant 11L8716N and FWO project 42/FAO10300/6541). The authors declare there are no conflicts of interest.

mRNA Expressions of Candidate Genes in Gestational Day 16 Conceptus and Corresponding Endometrium in Repeat Breeder Dairy Cows with Suboptimal Uterine Environment Following Transfer of Different Quality Day 7 Embryos

Simple Summary

The mRNA expression of Interferon-τ (IFNT), IFN stimulated genes (ISG15, CTSL1, RSAD2, SLC2A1, CXCL10, and SLC27A6), Peroxisome proliferator-activated receptors (PPARA, D, and G), and Retinoid X receptors (RXRA, B, and G) genes and proteins (IFNT, ISG15, CXCL10, PPARG, RXRG, SLC2A1, and SLC27A6) were lower and MUC1 at mRNA and protein levels, was greater in gestation day (GD) 16 embryo and corresponding endometrium of subclinical endometritis cows, and in cows following transfer of poor quality embryo (Grade 3). All genes and proteins but MUC1 expression was lower in GD16 tubular conceptus and corresponding endometrium vs. GD16 filamentous conceptus and matching endometrium in cows with SCE and in cows following the transfer of Grade 3 embryo. Disrupted embryo-uterine communication by altered expression of candidate genes in SCE cows, and in cows following the transfer of poor GD7 embryo negatively programs the conceptus development and plausibly affects the conceptus survival.

Abstract

Effect of the gestational day (GD) 7 embryo quality grade (QG) and subclinical endometritis (SCE) on mRNA and protein expressions of candidate genes [Interferon-τ (IFNT), IFN stimulated genes (ISG15, CTSL1, RSAD2, SLC2A1, CXCL10, and SLC27A6), Peroxisome proliferator activated receptors (PPARA, D, and G), Retinoid X receptors (RXRA, B, and G), and Mucin-1 (MUC1)] in GD16 conceptus and corresponding endometrium were evaluated. After screening of performance records (n = 2389) and selection of repeat breeders (n = 681), cows with SCE (≥6% polymorphonuclear neutrophils—PMN; n = 180) and no-SCE (<6%PMN; n = 180) received GD7 embryos of different QGs. Based on GD16 conceptus recovery, cows with SCE (n = 30) and No- SCE (n = 30) that received GD7 embryos QG1 (good, n = 20), 2 (fair, n = 20), and 3 (poor, n = 20) were included for gene analysis. mRNA and protein expressions (IFNT, ISG15, CXCL10, PPARG, RXRG, SLC2A1, and SLC27A6) differed between SCE and embryo QG groups. All genes but MUC1 and all proteins but MUC1 expression was greater in filamentous conceptus and corresponding endometrium vs. tubular conceptus and matching endometrium in SCE and embryo QG groups. In conclusion, disrupted embryo-uterine communication by altered expression of candidate genes in SCE cows, and in cows following the transfer of poor embryo negatively programs the conceptus development and plausibly affects conceptus survival.

Comparison of the Ability of High and Low Virulence Strains of Non-cytopathic Bovine Viral Diarrhea Virus-1 to Modulate Expression of Interferon Tau Stimulated Genes in Bovine Endometrium

Bovine Viral Diarrhea virus (BVDV) is a pestivirus with a single-stranded, positive sense RNA genome. It is endemic in many cattle populations, causing major economic losses in part due to reduced fertility. BVDV exhibits great genetic diversity and is classified as type 1 or 2 (BVDV-1, BVDV-2) with either non-cytopathogenic (ncp) or cytopathogenic (cp) biotypes. Differing strains of ncpBVDV differ in virulence, affecting clinical outcome. BVDV replicates in the reproductive tract, affecting host immunity and embryo survival. This study used an in vitro model of primary bovine endometrial cell cultures to compare the effects of two BVDV ncp type 1a strains of differing virulence (termed HO and KY) on endometrial transcription of candidate interferon stimulated genes (ISG) using qPCR. Half the cultures were stimulated with interferon tau (IFNT, the conceptus produced pregnancy recognition factor) in the presence or absence of viral infection. Cultures were replicated on cells from 10 BVDV-free cows. IFNT treatment stimulated transcription of 10 candidate ISGs, whereas both ncpBVDV-1 strains alone inhibited transcription of 8/10 ISGs. In combined BVDV-1+IFNT cultures, the stimulatory effect of IFNT on expression of GBP4, ISG15, HERC5, RSAD2, IFIH1, IFIT3, and MX1 was significantly inhibited by HO, but only ISG15, RSAD2, IFI27, and IFIT3 were decreased by KY. Inhibition by HO was generally greater. The IFNT-induced expression of TRIM56 was, however, increased by HO. These data show that HO, the more virulent ncpBVDV-1 strain, has a greater capacity to inhibit key antiviral pathways. These differences need confirmation at the protein level but may influence immune tolerance of the host. They could also reduce fertility by increasing uterine susceptibility to bacterial infection and disrupting IFNT-mediated pregnancy recognition.

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.

Effects of intrauterine devices on proteins in the uterine lavage fluid of mares

Intrauterine devices block luteolysis in cyclic mares, but the underlying mechanism is unknown. To clarify the mechanisms, the protein profile of the endometrial secretome was analyzed using two-dimensional difference gel electrophoresis (2D-DIGE). Twenty-seven mares were classified according to whether they were inseminated (AI) or had an intrauterine device (IUD), a water-filled plastic sphere, inserted into the uterus on Day 3 after ovulation. Uterine lavage fluids were collected on Day 15 from pregnant inseminated mares (AI-P; n = 8), non-pregnant inseminated mares (AI-N; n = 4), and mares with IUD (n = 15). The IUD group was further divided into prolonged (IUD-P; n = 7) and normal luteal phase (IUD-N; n = 8) groups on the basis of ultrasound examinations, serum levels of progesterone and PGFM on Days 14 and 15, and COX-2 results on Day 15. Four mares from each group were selected for the 2D-DIGE analyses. Ten proteins had significantly different abundance among the groups, nine of the proteins were identified. Malate dehydrogenase 1, increased sodium tolerance 1, aldehyde dehydrogenase 1A1, prostaglandin reductase 1, albumin and hemoglobin were highest in pregnant mares; T-complex protein 1 was highest in non-pregnant mares; and annexin A1 and 6-phosphogluconolactonase were highest in IUD mares. The results suggest that the mechanism behind the intrauterine devices is likely related to inflammation.

Genetic Diversity and Signatures of Selection for Thermal Stress in Cattle and Other Two Bos Species Adapted to Divergent Climatic Conditions

Understanding the biological mechanisms of climatic adaptation is of paramount importance for the optimization of breeding programs and conservation of genetic resources. The aim of this study was to investigate genetic diversity and unravel genomic regions potentially under selection for heat and/or cold tolerance in thirty-two worldwide cattle breeds, with a focus on Chinese local cattle breeds adapted to divergent climatic conditions, Datong yak (Bos grunniens; YAK), and Bali (Bos javanicus) based on dense SNP data. In general, moderate genetic diversity levels were observed in most cattle populations. The proportion of polymorphic SNP ranged from 0.197 (YAK) to 0.992 (Mongolian cattle). Observed and expected heterozygosity ranged from 0.023 (YAK) to 0.366 (Sanhe cattle; SH), and from 0.021 (YAK) to 0.358 (SH), respectively. The overall average inbreeding (±SD) was: 0.118 ± 0.028, 0.228 ± 0.059, 0.194 ± 0.041, and 0.021 ± 0.004 based on the observed versus expected number of homozygous genotypes, excess of homozygosity, correlation between uniting gametes, and runs of homozygosity (ROH), respectively. Signatures of selection based on multiple scenarios and methods (F ST, HapFLK, and ROH) revealed important genomic regions and candidate genes. The candidate genes identified are related to various biological processes and pathways such as heat-shock proteins, oxygen transport, anatomical traits, mitochondrial DNA maintenance, metabolic activity, feed intake, carcass conformation, fertility, and reproduction. This highlights the large number of biological processes involved in thermal tolerance and thus, the polygenic nature of climatic resilience. A comprehensive description of genetic diversity measures in Chinese cattle and YAK was carried out and compared to 24 worldwide cattle breeds to avoid potential biases. Numerous genomic regions under positive selection were detected using three signature of selection methods and candidate genes potentially under positive selection were identified. Enriched function analyses pinpointed important biological pathways, molecular function and cellular components, which contribute to a better understanding of the biological mechanisms underlying thermal tolerance in cattle. Based on the large number of genomic regions identified, thermal tolerance has a complex polygenic inheritance nature, which was expected considering the various mechanisms involved in thermal stress response.

Concentration-Dependent Type 1 Interferon-Induced Regulation of MX1 and FABP3 in Bovine Endometrial Explants

The inadequate maternal recognition of embryonic interferon τ (IFNτ) might explain subfertility in cattle. This study aimed at modeling the inducibility of type 1 interferon receptor subunits 1/2 (IFNAR1/2), mimicking competition between IFNτ and infection-associated interferon α (IFNα), and simulating type 1 interferon pathways in vitro. Endometrial explants (n = 728 from n = 26 healthy uteri) were collected at the abattoir, challenged with IFNτ and/or IFNα in different concentrations, and incubated for 24 h. Gene expression analysis confirmed the inducibility of IFNAR1/2 within this model, it being most prominent in IFNAR2 with 10 ng/mL IFNα (p = 0.001). The upregulation of interferon-induced GTP-binding protein (MX1, classical pathway) was higher in explants treated with 300 ng/mL compared to 10 ng/mL IFNτ (p < 0.0001), whereas the non‑classical candidate fatty acid binding protein 3 (FABP3) exhibited significant downregulation comparing 300 ng/mL to 10 ng/mL IFNτ. The comparison of explants challenged with IFNτ + IFNα indicated the competition of IFNτ and IFNα downstream of the regulatory factors. In conclusion, using this well-defined explant model, interactions between infection-associated signals and IFNτ were indicated. This model can be applied to verify these findings and to mimic and explore the embryo-maternal contact zone in more detail.

Association between progesterone concentration and endometrial gene expression in dairy cows

The objective of this study was to evaluate the association between progesterone concentration on Days 4 and 9 of the estrus cycle and endometrial transcriptome at Day 9 in lactating grazing dairy cows. Blood samples were obtained on Days 0, 4, and 9 for progesterone measurement by chemiluminescence. Cows were assigned to one of the following groups (n = 3 per group): cows with low physiological progesterone on Day 4, cows in anestrous, cows with high physiological progesterone on Day 4, and superovulated cows. Endometrial biopsy samples were obtained on Day 9 for RNA sequencing. Quality control and determination of differentially expressed genes (false discovery rate <0.05) were determined using the edgeR package for R software. We identified 3,042 differentially expressed genes among the 4 groups. Cows having high physiological progesterone and superovulated cows showed high similarities and clustered apart from those in anestrus or having low physiological progesterone. Functional analysis using Database for Annotation, Visualization, and Integrated Discovery revealed that endometrial genes upregulated by low progesterone concentration are enriched genes involved in the immune system and inflammatory response. Conversely, cows with high physiological progesterone concentration presented an endometrial transcriptome with similarities to cows with good genetic merit for fertility, showing upregulation of genes related to uterine relaxation-contraction, focal adhesion, GnRH signaling pathway, and epidermal growth factor-like related terms, suggesting a favorable embryo environment. In conclusion, our results support the concept that there is a threshold of progesterone concentration at the beginning of the luteal phase associated with endometrial expression of critical genes involved in the preparation of the uterine environment for embryo implantation.

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.

Interaction of preimplantation factor with the global bovine endometrial transcriptome

Preimplantation factor (PIF) is an embryo derived peptide which exerts an immune modulatory effect on human endometrium, promoting immune tolerance to the embryo whilst maintaining the immune response to invading pathogens. While bovine embryos secrete PIF, the effect on the bovine endometrium is unknown. Maternal recognition of pregnancy is driven by an embryo-maternal cross talk, however the process differs between humans and cattle. As many embryos are lost during the early part of pregnancy in cattle, a greater knowledge of factors affecting the embryo-maternal crosstalk, such as PIF, is needed to improve fertility. Therefore, for the first time, we demonstrate the effect of synthetic PIF (sPIF) on the bovine transcriptome in an ex vivo bovine endometrial tissue culture model. Explants were cultured for 30h with sPIF (100nM) or in control media. Total RNA was analysed via RNA-sequencing. As a result of sPIF treatment, 102 genes were differentially expressed compared to the control (Padj<0.1), although none by more than 2-fold. The majority of genes (78) were downregulated. Pathway analysis revealed targeting of several immune based pathways. Genes for the TNF, NF-κB, IL-17, MAPK and TLR signalling pathways were down-regulated by sPIF. However, some immune genes were demonstrated to be upregulated following sPIF treatment, including C3. Steroid biosynthesis was the only over-represented pathway with all genes upregulated. We demonstrate that sPIF can modulate the bovine endometrial transcriptome in an immune modulatory manner, like that in the human endometrium, however, the regulation of genes was much weaker than in previous human work.