Maternal Immune Regulation by Conceptus During Early Pregnancy in the Bovine

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.

Implantation associated changes in expression profile of indoleamine-2, 3-dioxygenase 1, Th1-Th2 cytokines and interferon-stimulated genes on neutrophils and peripheral blood mononuclear cells of crossbred cows

Effective bidirectional communication between the embryo and dam improves the reproductive efficiency of dairy cows. Possible role of immunosuppressive indolamine-2, 3-dioxygenase 1 (IDO1) enzyme in the regulation of maternal systemic cytokine balance/shift during early pregnancy establishment along with various interferon-stimulated genes (ISGs) expression in neutrophils and peripheral blood mononuclear cell (PBMCs) were investigated in crossbred cows. Blood was collected on days 0 i.e. day of Artificial Insemination (AI), 10, 18 and 36 post-AI followed by isolation of neutrophils and PBMCs for gene expression study of IDO1, anti-inflammatory cytokines (IL-4, IL-10 and TGFβ1), pro-inflammatory cytokines (IFNγ and TNFα) and ISGs (ISG15, MX1, MX2, OAS1) in pregnant and non-pregnant cows. Cows were grouped as pregnant and non-pregnant after pregnancy confirmation by non-return to heat, ultrasonography, per rectal examination along with progesterone and IFNτ assay. Significantly (P < 0.05) higher relative mRNA expression of IDO1 and anti-inflammatory cytokines on days 10 and 18 post-AI were observed in both neutrophils and PBMCs of pregnant cows. Pregnant cows showed significantly (P < 0.05) higher mRNA transcripts of IFNγ and TNFα genes on days 18 post-AI in both neutrophils and PBMCs. Expression of ISGs was higher (P < 0.05) on day 10^th and 18^th post AI in both the neutrophils and PBMCs of pregnant cows. The study indicates that systemic immune regulation by IDO1 (through cytokine shift) and ISGs in peripheral immune cells are essential for the establishment of pregnancy and may be targeted in future as biomarkers for pregnancy diagnosis.

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

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

Expression of melatonin receptors and CD4 in the ovine thymus, lymph node, spleen and liver during early pregnancy

As a pineal gland hormone, melatonin acts through its receptors to modulate the immune system. The immune system is composed of primary and secondary organs, and immune organs are adapted to the presence of the fetal alloantigen during pregnancy. However, it is unclear whether melatonin affects maternal immune organs during early pregnancy in sheep. In this study, the ovine thymus, lymph node, spleen and liver were sampled at day 16 of the oestrous cycle, and at days 13, 16 and 25 of pregnancy. The expression of melatonin receptor 1A (MT1), melatonin receptor 1B (MT2) and cluster of differentiation 4 (CD4) was detected by quantitative real-time polymerase chain reaction, Western blot and immunohistochemistry experiments. Our results showed that during early pregnancy there was an upregulation of MT1 mRNA and protein in the thymus, lymph node and liver, and there was a downregulation in the spleen. The expression of MT2 mRNA and protein was increased in the thymus but decreased in the spleen and liver, and there was no significant change in the lymph node during early pregnancy. CD4 protein was upregulated in the thymus, lymph node and liver, but there were no significant changes in the spleen during early pregnancy. In conclusion, early pregnancy induces tissue-specific expression of MT1, MT2 and CD4, which may be due to the different functions of the thymus, lymph node, spleen and liver. Further, melatonin is involved in immune regulation of the maternal thymus, lymph node, spleen and liver during early pregnancy in sheep.

Pregnancy loss in beef cattle: A meta-analysis

Pregnancy loss in beef cattle causes both management and economic challenges to a producer. A meta-analysis was conducted to quantify reproductive failures that occur during fertilization, early embryonic development, and late embryonic/early fetal development periods of gestation in beef cattle. The meta-analysis included more than 56,000 diagnostic records in 159 studies from 48 papers with 12 studies included in fertilization and pre- blastocyst loss analysis (FERT; days 1-7 of gestation), 107 in early embryo (EEM; days 7-32), and 40 in late embryo/early fetal period (LEF; days 32-100) analysis. Although fertilization rates are reportedly high in beef cattle, significant developmental failure occurs within the first 7 days of gestation. Approximately 28.4 % of embryos will not develop past day 7 of gestation with most embryonic losses occurring before day 4. By the conclusion of the first month of gestation, 47.9 % of cows submitted to a single insemination at day 0 will not be pregnant. Overall, LEF between days 32-60 and 100 was 5.8 %. Bos indicus animals had greater (P =  0.001) EEM compared to Bos taurus, but there was no difference (P =  0.39) for the LEF period between subspecies. Primiparous cows had greater EEM (P =  0.002) compared to nulliparous heifers and multiparous cows; and nulliparous heifers had a greater LEF compared to primiparous and multiparous cows (P =  0.048). Collectively, these cumulative findings provide a baseline assessment of pregnancy loss specific to beef cattle.

Modulation of Helper T Cytokines in Thymus during Early Pregnancy in Ewes

Simple Summary

The thymus is a main organ of the immune system. Immune tolerance exists in maternal immune system during pregnancy. Helper T (Th)1 and Th2 cytokines regulate the functions of immune system. We found that early pregnancy affected the production of Th1 and Th2 cytokines in maternal thymus in sheep, which may be beneficial for normal pregnancy.

Abstract

There is an immune tolerance in maternal immune system during pregnancy, and thymus is a main organ of the immune system. Helper T (Th)1 and Th2 cytokines are involved in the regulation of immune system, but the modulation of Th cytokines in the thymus during early pregnancy is unclear in ewes. Thymuses were collected on day 16 of the estrous cycle, and on days 13, 16, and 25 of pregnancy in ewes. qRT-PCR, Western blot, and immunohistochemistry were used to analyze the expression of Th1 and Th2 cytokines in the thymuses. There was a peak in the expression of interferon-gamma (IFN-γ) on day 16 of pregnancy, an upregulation of tumor necrosis factor beta (TNF-β), and a sustained expression of interleukin-2 (IL-2) and IL-4. Furthermore, there was a peak in the expression of IL-6 on day 13 of pregnancy, no expression of IL-6 on day 16 of the estrous cycle and day 25 of pregnancy, and an upregulation of IL-5 and IL-10 in the thymuses during early pregnancy. The immunohistochemistry results revealed that the IFN-γ and IL-6 proteins were limited to the stromal cells, capillaries, and thymic corpuscles. In conclusion, early pregnancy influenced the production of Th1 and Th2 cytokines of maternal thymus in sheep.

Comparison of Th1 and Th2 cytokines production in ovine lymph nodes during early pregnancy

As a fetal allograft to the mother, early conceptus regulates the intrauterine immune and systemic immune responses during early pregnancy in sheep. However, expression of T helper 1 (Th1) and Th2 cytokines in maternal lymph nodes is unclear during early pregnancy in sheep. In this study, inguinal lymph nodes were obtained on day 16 of the estrous cycle and on days 13, 16 and 25 of pregnancy (n = 4 for each group) in ewes, and qRT-PCR, western blot and immunohistochemistry were used to compare the expression of Th1 and Th2 cytokines in the lymph nodes. Our results showed that there were the highest levels of Th1 cytokines (IFN-γ, TNF-β and IL-2) and Th2 cytokines (IL-4, IL-5, IL-6 and IL-10) in the lymph nodes on day 13 or 16 of pregnancy. Furthermore, there were a downregulation of TNF-β and IL-2 and an upregulation of IL-5 and IL-10 on day 25 of pregnancy compared with that in nonpregnancy, with no significant difference in the expression of IFN-γ, IL-4, and IL-6 between the ewes on day 25 of pregnancy and nonpregnancy. The immunohistochemistry results showed that the IL-2 and IL-10 proteins were limited to the subcapsular sinus and trabeculae in the cortex, lymph sinus. In conclusion, early pregnancy exerted its effects on the lymph node and induced a Th2-biased response, which was essential for a normal pregnancy in sheep.

Differential expression of interferon-gamma, IL-4 and IL-10 in peripheral blood mononuclear cells during early pregnancy of the bovine

Maternal systemic immune response is regulated by conceptus-derived signals through peripheral blood mononuclear cells (PBMCs) via blood circulation during early pregnancy in cattle. In this study, the PBMCs from day 18 in non-pregnant cows and days 14, 18 and 30 in pregnant cows were used to explore the expression of interferon-gamma (IFN-γ), interleukin 4 (IL-4) and IL-10, and the plasma progesterone (P4) concentration was also determined. The results showed that the expression levels of mRNA and the protein of IFN-γ were lower and that IL-4 and IL-10 were higher in the PBMCs from the pregnant cows than in those of non-pregnant cows. From this study, early pregnancy induced a lower Th1 immunity (IFN-γ) and a higher Th2 immunity (IL-4 and IL-10) in the PBMCs, which may be related to interferon-tau and P4, thereby contributing to successful pregnancy in cattle.

Age-associated mRNA expression changes in bovine endometrial cells in vitro

BACKGROUND

Endometrial cells secrete various cytokines and the dysfunction of endometrial cells may directly lead to infertility. Interferon tau (IFNT) secreted by trophoblast cells, a well-known pregnancy recognition signal in ruminants, acts on the uterus to prepare for pregnancy. Aging causes cellular and organ dysfunction, and advanced maternal age is associated with reduced fertility. However, few studies have investigated age-dependent changes in the uterus.

METHODS

Using next generation sequencing and real-time PCR, we examined mRNA expression in bovine endometrial cells in vitro obtained from young (mean 45.2 months) and aged (mean 173.5 months) animals and the effects of IFNT depending on the age.

RESULTS

We showed that inflammation-related (predicted molecules are IL1A, C1Qs, DDX58, NFKB, and CCL5) and interferon-signaling (predicted molecules are IRFs, IFITs, STATs, and IFNs) pathways were activated in endometrial cells obtained from aged compared to young cows. Also, the activation of "DNA damage checkpoint regulation" and the inhibition of "mitotic mechanisms" in endometrial cells obtained from aged cows were evident. Moreover, we showed lower cell viability levels in endometrial cells obtained from aged compared to young cows. Although treatment with IFNT upregulated various types of interferon stimulated genes both in endometrial cells obtained from young and aged cows, the rate of increase by IFNT stimulus was obviously lower in endometrial cells obtained from aged compared to young cows.

CONCLUSIONS

Endometrial cells obtained from aged cows exhibited higher levels of inflammatory- and IFN-signaling, and dysfunction of cell division compared with young cows. In addition, a high basal level of IFN-related genes in endometrial cells of aged cows is suggested a concept of "inflammaging".

Expression of genes associated with luteolysis in peripheral blood mononuclear cells during early pregnancy in cattle

The conceptus-derived signals that initiate maternal recognition of pregnancy act primarily on the endometrium to inhibit the development of luteolysis, thus modifying the expression of genes in the corpus luteum. The involvement of peripheral blood mononuclear cells (PBMCs) in the formation of this anti-luteolytic mechanism during early pregnancy is uncertain. In this study, PBMCs from non-pregnant and early-pregnant cows were sampled to explore the expression of genes associated with luteolysis, including AKR1B1 (aldo-keto reductase family 1, member B1; a bovine prostaglandin F synthase), PTGFR (PGF2α receptor), OXT (oxytocin), PTGES (PGE synthase), PTGER1 (PGE2 receptor 1), and PGR (progesterone receptor). OXT and PTGFR transcript abundance was low in PBMCs at Day 18 in pregnant individuals. PGR and PTGER1 mRNA abundance was significantly higher at Day 30 in pregnant individuals. AKR1B1 and PTGES transcript abundance was significantly higher at Day 18 in PBMCs from non-pregnant individuals, yet AKR1B1 and PTGES protein abundance was elevated at Day 30 in pregnant individuals-although AKR1B1 dimer may be significantly higher at Day 18 in non-pregnant PBMCs. In conclusion, changes in bovine PBMC gene expression are associated with luteolysis during early pregnancy, which implicate the influence of circulating blood components in controlling luteolysis. Mol. Reprod. Dev. 83: 509-515, 2016. © 2016 Wiley Periodicals, Inc.