Expression dynamics of bovine MX genes in the endometrium and placenta during early to mid pregnancy

Characterization and expression profiling of buffalo IFN-lambda family

Interferon lambda (IFN-λ) is an important type III interferon triggered mainly by viral infection. IFN-λ binds to their heterodimeric receptors and signals through JAK-STAT pathways similar to type I IFN. In this study, we deduced the buffalo IFN-λ sequences through the polymerase chain reaction, and then studied IFN-λ's expression patterns in different tissues, and post induction with poly I:C and live MRSA using RT-qPCR. The full-length sequences of buffalo IFN-λ3, IFN-λ receptors, and a transcript variant of IFN-λ4 were determined. IFN-λ1 is identified as a pseudogene. Virus response elements and a recombination hotspot factor was observed in the regulatory region of IFN-λ. The IFN-λ3 expressed highest in lungs and monocytes but IFN-λ4 did not. The expression of Interferon Lambda Receptor 1 was tissue specific, while Interleukin 10 Receptor subunit beta was ubiquitous. Following poly I:C induction, IFN-λ3 expression was primarily observed in epithelial cells as opposed to fibroblasts, displaying cell type-dependent expression. The cytosolic RNA sensors were expressed highest in endometrial epithelial cells, whereas the endosomal receptor was higher in fibroblasts. 2',5'-oligoadenylate synthetase expressed higher in fibroblasts, myxoma resistance protein 1 and IFN-stimulated gene 56 in epithelial cells, displaying cell-specific antiviral response of the interferon stimulated genes (ISGs). The endometrial epithelial cells expressed IFN-λ3 after live S. aureus infection indicating its importance in bacterial infection. The induction of IFN-λ3 was S. aureus isolate specific at the same multiplicity of infection (MOI). This study elucidates the IFN-λ sequences, diverse expression patterns revealing tissue specificity, and specificity in response to poly I:C and bacterial stimuli, emphasising its crucial role in innate immune response modulation.

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.

Early milk-feeding regimes in calves exert long-term effects on the development of ovarian granulosa cells

BACKGROUND

Nutrition has not only an impact on the general wellbeing of an animal but can also affect reproductive processes. In cattle, feeding regimes can influence the age of puberty onset and alter gonadal development. We analyzed effects of different milk replacer (MR) feeding regimes during rearing on ovarian physiology with specific emphasis on the numbers as well as gene expression characteristics of granulosa cells (GCs) at the age of puberty onset. Two groups of calves received either 10% or 20% of bodyweight MR per day during their first 8 weeks. After weaning, both groups were fed the same mixed ration ad libitum until slaughter at 8 months.

RESULTS

Animals of the 20% feeding group had a significantly higher body weight, but the proportion of animals having a corpus luteum at the time of slaughter was not different between groups, suggesting a similar onset of puberty. Calves of the 10% group showed a constant GC count regardless of the number of follicles (r = 0.23) whereas in the 20% group increasing numbers of GCs were detected with a higher follicle count (r = 0.71). As a first effort to find a possible molecular explanation for this unexpected limitation of GC numbers in the 10% group, we comparatively analyzed GC transcriptomes in both diet groups. The mRNA microarray analysis revealed a total of 557 differentially expressed genes comparing both groups (fold change > |1.5| and p < 0.05). OAS1X, MX2 and OAS1Z were among the top downregulated genes in the 20% vs. the 10% group, whereas top upregulated genes comprised BOLA and XCL1. All of these genes are known to be regulated by interferon. Subsequent signaling pathway analysis revealed the involvement of several immune response mechanisms in accordance with a number of interferons as upstream regulators.

CONCLUSIONS

The results indicate that the plane of MR feeding in early life has an impact on the number and physiology of GCs later in life. This might influence the overall reproductive life initiated by the onset of puberty in cattle. In addition, the observed alterations in GCs of calves fed less MR might be a consequence of interferon regulated immunological pathways.

Single-nuclei RNA sequencing (snRNA-seq) uncovers trophoblast cell types and lineages in the mature bovine placenta

Ruminants have a semi-invasive placenta, which possess highly vascularized placentomes formed by maternal endometrial caruncles and fetal placental cotyledons and required for fetal development to term. The synepitheliochorial placenta of cattle contains at least two trophoblast cell populations, including uninucleate (UNC) and binucleate (BNC) cells that are most abundant in the cotyledonary chorion of the placentomes. The interplacentomal placenta is more epitheliochorial in nature with the chorion developing specialized areolae over the openings of uterine glands. Of note, the cell types in the placenta and cellular and molecular mechanisms governing trophoblast differentiation and function are little understood in ruminants. To fill this knowledge gap, the cotyledonary and intercotyledonary areas of the mature day 195 bovine placenta were analyzed by single nuclei analysis. Single-nuclei RNA-seq analysis found substantial differences in cell type composition and transcriptional profiles between the two distinct regions of the placenta. Based on clustering and cell marker gene expression, five different trophoblast cell types were identified in the chorion, including proliferating and differentiating UNC and two different types of BNC in the cotyledon. Cell trajectory analyses provided a framework for understanding the differentiation of trophoblast UNC into BNC. The upstream transcription factor binding analysis of differentially expressed genes identified a candidate set of regulator factors and genes regulating trophoblast differentiation. This foundational information is useful to discover essential biological pathways underpinning the development and function of the bovine placenta.

A decreased expression of interferon stimulated genes in peri-implantation endometrium of embryo transfer recipient sows could contribute to embryo death

Pig pregnancy succeeds thanks to a well-coordinated system ruling both maternal immune activation and embryonic antigen tolerance. In physiological pregnancies, the maternal immune system should tolerate the presence of hemi-allogeneic conceptuses from the pre-implantation phase to term, while maintaining maternal defence against pathogens. Allogeneic pregnancies, as after embryo transfer (ET), depict high embryo mortality during the attachment phase, calling for studies of the dynamic modifications in immune processes occurring at the maternal-foetal interface, for instance, of interferon (IFN)-stimulated genes (ISGs). These ISGs are generally activated by IFN secreted by the conceptus during the process of maternal recognition of pregnancy (MRP) and responsible for recruiting immune cells to the site of embryo attachment, thus facilitating cell-antigen presentation and angiogenesis. We performed RNA-Seq analysis in peri-implantation (days 18 and 24) endometrial samples retrieved from artificially inseminated sows (hemi-allogeneic embryos (HAL) group) or sows subjected to ET (allogeneic embryos (AL) group) to monitor alterations of gene expression that could be jeopardising early pregnancy. Our results showed that endometrial gene expression patterns related to immune responses differed between hemi- or allogeneic embryo presence, with allogeneic embryos apparently inducing conspicuous modifications of immune-related genes and pathways. A decreased expression (P < 0.05; FC < -2) of several interferon ISGs, such as CXCL8, CXCL10, IRF1, IRF9, STAT1, and B2M, among others was detected in the endometrium of sows carrying allogeneic embryos on day 24 of pregnancy. This severe downregulation of ISGs in allogeneic pregnancies could represent a failure of ET-embryos to signal IFN to the endometrium to warrant the development of adequate immunotolerance mechanisms to facilitate embryo development, thus contributing to elevated embryo death.

RNA-Sequencing based analysis of bovine endometrium during the maternal recognition of pregnancy

BACKGROUND

Maternal recognition is the crucial step for establishing pregnancy in cattle. This study aims to identify endometrial genes and biological pathways involved in the maternal recognition of pregnancy. Caruncular endometrial tissues were collected from Day 15-17 of gestation (pregnant), non-pregnant (absence of conceptus), and cyclic (non-bred) heifers.

RESULTS

Total RNAs were isolated from the caruncular endometrial tissues of pregnant, non-pregnant, and cyclic heifers, and were subjected to high-throughput RNA-sequencing. The genes with at least two-fold change and Benjamini and Hochberg p-value ≤ 0.05 were considered differentially expressed genes and further confirmed with quantitative real-time PCR. A total of 107 genes (pregnant vs cyclic) and 98 genes (pregnant vs non-pregnant) were differentially expressed in the pregnant endometrium. The most highly up-regulated genes in the pregnant endometrium were MRS2, CST6, FOS, VLDLR, ISG15, IFI6, MX2, C15H11ORF34, EIF3M, PRSS22, MS4A8, and TINAGL1. Interferon signaling, immune response, nutrient transporter, synthesis, and secretion of proteins are crucial pathways during the maternal recognition of pregnancy.

CONCLUSIONS

The study demonstrated that the presence of conceptus at Day 15-17 of gestation affects the endometrial gene expression related to endometrial remodeling, immune response, nutrients and ion transporters, and relevant signaling pathways in the caruncular region of bovine endometrium during the maternal recognition of pregnancy.

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.

Context is key: Maternal immune responses to pig allogeneic embryos

Successful establishment of pregnancy includes the achievement of a state of immune tolerance toward the embryos (and placenta), where the well‐coordinated maternal immune system is capable of recognizing conceptus antigens while maintaining maternal defense against pathogens. In physiological pregnancies, following natural mating or artificial insemination (AI), the maternal immune system is exposed to the presence of hemi‐allogeneic embryos, that is, embryos containing maternal self‐antigens and foreign antigens from the paternal side. In this scenario, the hemi‐allogeneic embryo is recognized by the mother, but the immune system is locally modified to facilitate embryo implantation and pregnancy progression. Pig allogeneic pregnancies (with embryos containing both paternal and maternal material foreign to the recipient female), occur during embryo transfer (ET), with conspicuously high rates of embryonic death. Mortality mainly occurs during the peri‐attachment phase, suggesting that immune responses to allogeneic embryos are more complex and less efficient, hindering the conceptuses to survive to term. Reaching a similar maternal tolerance as in conventional breeding would render ET successful. The present review critically summarizes mechanisms of maternal immune recognition of pregnancy and factors associated with impaired maternal immune response to the presence of allogeneic embryos in the porcine species.

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.

Neutrophils recognize and amplify IFNT signals derived from day 7 bovine embryo for stimulation of ISGs expression in vitro: A possible implication for the early maternal recognition of pregnancy

Previously, we reported that the presence of multiple day 7 (D7) bovine embryos in the uterus induces systemic immune responses in circulating polymorphonuclear neutrophils (PMNs), but with unknown mechanism. Thus, this study aimed to investigate the direct impact of D7 bovine embryo on PMNs' immune responses in vitro and whether these PMNs can amplify and transfer embryo signals further to another PMN population. PMNs were directly stimulated by embryo culture media (ECM) or interferon tau (IFNT) (10 ng/ml) followed by evaluating mRNA expression by real-time PCR and phenotypic analysis by flow cytometry. To test whether PMNs can transfer embryo signals to a new PMN population, PMNs triggered by ECM or IFNT, were thoroughly washed and diluted to remove any media components, and again were incubated in fresh culture media for 3 h, from which culture supernatants were collected and used as PMN conditioned media (CM) to stimulate a new PMN population. Similar to ECM, IFNT directly stimulated expressions of IFNs (IFNA, IFNG), interferon-stimulated genes (ISGs; OAS1, ISG15, MX1), STAT1, TGFB and IL8, and downregulated TNFA in PMNs. Flow cytometrical analyses demonstrated that IFNT stimulated expressions of pregnancy-related phenotypic markers, CD16 and arginase-1 (ARG1), in PMNs. Most importantly, PMN CM induced ISGs and STAT1 mRNA in fresh PMNs. Since IFNT directly upregulated IFNA expression in PMNs, the impact of IFNA on PMNs' immune responses was further tested. Stimulation of PMNs with IFNA, especially at a low level (1 pg/ml), induced IFNT-like immune responses comparable to those induced by PMN CM. Together, these findings indicated that D7 bovine embryos induce direct anti-inflammatory responses with upregulation of ISGs expressions in PMNs mainly via IFNT. Additionally, PMNs can amplify and transfer embryo signals to a new PMN population in a cell-to-cell communication mechanism possibly mediated in part by IFNA. Such a novel immunological crosstalk might contribute to embryo tolerance and pregnancy establishment in cattle.

Myxovirus resistance 1 (Mx1) gene: Molecular characterization of complete coding sequence and expression profile in the endometrium of goat (Capra hircus)

Myxovirus resistance 1 (Mx1) gene plays an important role in uterine receptivity and conceptus development by creating a strong defense mechanism in the uterine environment. However, the specific role of Mx1 gene is not yet documented in the goat. Therefore, in the present study, full-length coding sequence (CDS) of the Mx1 gene was amplified, sequenced and characterized through various Bioinformatic tools. Temporal expression profile of Mx1 mRNA and protein was also examined by quantitative real-time PCR (qPCR) and western blot, respectively, in the endometrium of cyclic stage (non-pregnant), pregnancy stage I (16-24 days of gestation) and pregnancy stage II (25-40 days of gestation) of caprine (cp). A fragment of the cpMx1 gene, 2144 bp in length, was amplified from complementary DNA (cDNA) with a 1965 bp open reading frame. Coding and deduced amino acid sequences of the cpMx1 were aligned with other species and it exhibited 98.8-81.5 % identities with different species. On phylogenetic analysis, sheep and goat were found belonging to the same clade but differing from large ruminants. The cpMx1 protein possess the conserved signature motif (LPRGTGIVTR) of dynamin superfamily and the tripartite guanosine-5'-triphosphate (GTP) binding motif (GDQSSGKS, DLPG, TKPD) at the N-terminal end, and the leucine zipper motifs at the C-terminal end. Both cpMx1 mRNA and protein were found to be expressed maximally (P < 0.05) in the pregnancy stage I as compared to cyclic stage. It was concluded that the cpMx1 gene shares major structural and probably functional similarities with other species.

Changes in expression of interferon-stimulated genes and ubiquitin activating enzyme E1-like in ovine thymus during early pregnancy

As the main signal for the maternal recognition in ruminants, interferon-tau (IFNT) stimulates expression of interferon-stimulated genes (ISGs) in uterus and many extrauterine tissues. However, it is unclear that early pregnancy induces expression of signal transducer and activator of transcription 1 (STAT1), myxovirusresistance 1 (Mx1), interferon-gamma-inducible protein 10 (IP-10) and ubiquitin activating enzyme E1-like protein (UBE1L) in maternal thymus. In this study, ovine thymuses were sampled on day 16 of the estrous cycle and on days 13, 16 and 25 of gestation, and the expression of STAT1, Mx1, IP-10 and UBE1L was detected by real-time quantitative PCR, Western blot and immunohistochemistry. The results revealed that the expression of STAT1 and IP-10 reached peaks on day 16 of pregnancy, and expression of Mx1 was enhanced on day 25 of pregnancy, and STAT1 protein was located in the epithelial reticular cells, capillaries and thymic corpuscles. However, expression of UBE1L was declined during early pregnancy. In conclusion, early pregnancy influences expression of STAT1, Mx1, IP-10 and UBE1L in maternal thymus, which may participate in regulation of maternal immune tolerance during early pregnancy in sheep.

The newly established bovine endometrial gland cell line (BEGC) forms gland acini in vitro and is only IFNτ-responsive (MAPK42/44 activation) after E2 and P4-pre-incubation

INTRODUCTION

Uterine glands (UG) are crucial for the establishment of ruminant pregnancy and influenced (orchestrated manner) by estrogen (E₂), progesterone (P₄) and interferon tau (IFNτ). In the study we established a bovine endometrial glandular cell line (BGEC) and tested its functional reactivity (signaling) to IFNτ.

METHODS

BGEC was characterized by light microscopy (LM), epithelial markers (ezrin, CK18) [immunofluorescence (IF)/immunohistochemistry (IHC)] and ultrastructure (TEM/SEM) (apical microvilli). In vitro formation of gland acini and transepithelial-electric-resistance (TEER) measurements (EVOM) were done. The expression of mRNA-transcripts (RT-PCR) of steroid receptors (PR, PGRMC1/2, ESR1/2) and the IFNτ-system (IFNAR1/2, IRF1, 2, 9) was checked. BEGC was stimulated with IFNτ (10 ng/ml;1000 ng/ml) (15 min) after steroid pre-treatment [10 pg/ml E₂ (two days)/20 ng/ml P₄ (two days)]. Activation of MAPK42/44;STAT1 was evaluated (densitometrical Western Blot).

RESULTS

BGEC cells expressed epithelial markers and possessed apical microvilli. High TEER-values could be measured (2320-2620 ohm/cm²). The assembled BEGC acini (25 days) were similar to UG in vivo (markers/ultrastructure). All transcripts (steroid receptors/IFNτ-system) could be detected in BEGC (mRNA). MAPK42/44 were significantly activated after E₂/P₄ pre-treatment and IFNτ stimulation (10 ng/ml) (p < 0.05), whilst 1000 ng/ml IFNτ did not activate MAPK42/44. Neither a STAT1 (by IFNτ) nor an activation (MAPK42/44;STAT1) by IFNτ-only was observed.

DISCUSSION

BGEC retains its epithelial phenotype in culture and forms gland acini in vitro thereby confirming its glandular character. Cells were only reactive to (low) IFNτ concentrations when pre-treated with steroids thereby closely resembling implantation physiology in vivo. BEGC can be used as a bovine implantation model to study embryo-maternal communication during early pregnancy in cattle.

Expression of IFNAR1 and IFNAR2 in cattle placenta during early pregnancy

Interferon-tau (IFNT), a type I interferon, is an antiluteolytic factor secreted by trophoderm during pregnancy. IFNT transmitted signals or stimulated the expression of some factors to build maternal recognition and keep pregnancy by binding its receptors, IFNT receptor 1(IFNAR1) and IFNT receptor 2 (IFNAR2). Up to now, the expression model and roles of IFNAR1 and IFNAR2 in placenta have not been investigated in cattle. In this study, the localization and expression of IFNAR1 and IFNAR2 in the cattle placenta at days 18-50 of pregnancy were detected by histological examination, immunofluorescence staining and real-time qPCR. The results showed that IFNAR1 mainly distributed in chorioallantoic membrane, endometrial epithelium, cotyledon and caruncle during the early pregnancy of cattle with change in time- and position-dependent. IFNAR1 and IFNAR2 mRNA expression were mainly detected in chorioallantoic membrane and cotyledon, and markedly increased along with pregnancy process. Moreover, the mRNA expression level of IFNAR1 in chorioallantoic membrane and cotyledon was higher than that of IFNAR2. IFNAR mRNA was also expressed in caruncle tissues, which experienced a tendency of decrease from days 21 to 36, followed by increase after days 36. These results provide morphological basis and quantitative data for investigating the roles of IFNAR1 and IFNAR2 on development of cattle placenta and pregnancy maintenance.

Estrous cycle stage-dependent manner of type I interferon-stimulated genes induction in the bovine endometrium

Interferon tau (IFN-τ) is a ruminant-specific type I IFN secreted by a conceptus before its attachment to the uterus. IFN-τ induces the expression of IFN-stimulated genes (ISGs) via the type I IFN receptor (IFNAR), which is composed of IFNAR1 and IFNAR2 subunits in the endometrium. However, expression patterns of IFNARs during the estrous cycle have not been reported. We hypothesized that the response to a type I IFN changes along with IFNARs and the IFN-regulatory factors (IRFs) driving transcription of IFN signal-related genes and modulating a type I IFN signal during the estrous cycle. We investigated the estrous cycle stage-dependent type I IFN induction of ISGs and expression patterns of IFN signal-related genes in bovine endometrial tissues. Endometrial tissue pieces collected from bovine uteri at each estrous stage (early, mid, and late) were cultured with or without recombinant bovine IFN-α or concentrated pregnant uterine flushing (PUF) on day 18 after confirming the presence of a conceptus. IFN-α and PUF each significantly increased the expression of ISGs in endometrial tissues. The induction levels of the typical ISGs (MX1-a and ISG15) were significantly higher at the mid stage and correlated with high expression of IRFs at the mid stage. The immunostaining of IFNARs showed strong fluorescence intensities in luminal and glandular epithelia at the early and mid stages. Collectively, these results suggest that the endometrium exhibits estrous cycle stage-dependent responsiveness to type I IFN that may be associated with the expression of IFNARs and IRFs for pregnancy recognition.

Change in the responsiveness of interferon-stimulated genes during early pregnancy in cows with Borna virus-1 infection

Background

Borna disease virus is a neurotropic pathogen and infects the central nervous system. This virus infected a variety of animal species including cows. The most of cows infected with Borna disease virus 1 (BoDV-1) exhibit subclinical infection without any neurological symptoms throughout their lifetime. We previously reported on the low conception rates in-seropositive cows. Interferon-τ (IFN-τ) plays an important role in stable fertilization, and is produced from the fetal side following embryo growth at 15–40 days of pregnancy. IFN-τ induces the expression of interferon-stimulated gene (ISG) 15 and Mx2 in peripheral blood mononuclear cells (PBMCs). To understand the embryo growth and maternal reaction during early pregnancy in cows with BoDV-1 infection, we aimed to assess the gene expression of ISG15 and Mx2 from PBMCs in BoDV-1-seropositive cows.

Results

None of the cows showed any clinical and neurological symptoms. Among the cows that conceived, the expressions of the ISG15 and Mx2 genes were greater in the BoDV-1-seropositive cows than in the BoDV-1-seronegative cows; the difference was significant between the cows that conceived and those that did not (P < 0.05).

Conclusions

The expression of ISG15 and Mx2 genes during early pregnancy significantly increased in the BoDV-1-seropositive cows and may be important for the maintenance of stable pregnancy in BoDV-1-infected cows. In contrast, the gene expression levels of ISG15 and Mx2 did not significantly increase during early pregnancy in BoDV-1-seronegative cows. Thus, BoDV-1 infection may lead to instability in the maintenance of early pregnancy by interfering with INF-τ production.