IL-22 is expressed by the invasive trophoblast of the equine (Equus caballus) chorionic girdle

Activated T cells are the cellular source of IL-22 that enhances proliferation and survival of lymphocytes in Nile tilapia

As a pleiotropic cytokine mainly secreted by CD4⁺ T cells, interleukin (IL)-22 plays an important role in immune regulation and infection elimination. Despite IL-22 homologues have been identified in non-mammal, whether and how IL-22 participates in the adaptive immune response of early vertebrates have not been fully addressed. In this study, we identified an evolutionarily conserved IL-22 from Nile tilapia Oreochromis niloticus (defined as OnIL-22), proved by its properties regarding sequence, gene structure, functional domain, tertiary structure and phylogeny. IL-22 was broadly expressed in lymphoid-related tissues of tilapia, and with relatively higher levels in skin, gill, intestine and liver. The expression of OnIL-22 in spleen lymphocytes was markedly induced at the adaptive immune stage after Streptococcus agalactiae infection. Moreover, once lymphocytes were activated by PMA plus ionomycin or T-cell specific mitogen PHA in vitro, OnIL-22 expression was obviously up-regulated at both mRNA and protein levels. These results thus suggest that activated T cells produce IL-22 to take part in the adaptive immune response of tilapia. Furthermore, treatment of lymphocytes with recombinant OnIL-22 increased the expression of genes related to proliferation and survival, and further promoted the proliferation and reduced the apoptosis of lymphocytes during bacterial infection or T-cell activation. These cellular effects of IL-22 seem to be associated with JAK1/STAT3 axis downstream of IL-22, because IL-22 application not only elevated the mRNA expression of JAK1 and STAT3, but also enhanced their phosphorylation in lymphocytes. Altogether, we suggest that activated T cells produce IL-22 to promote lymphocyte proliferation and survival probability via JAK1/STAT3 signaling pathway, thus participating in adaptive immune response of Nile tilapia. Our study therefore provides helpful perspective for understanding the function and mechanism of adaptive immune system in teleost.

Fibrinogen in equine pregnancy as a mediator of cell adhesion, an epigenetic and functional investigation

Preimplantation equine embryos synthesize and secrete fibrinogen, which is a peculiar finding as fibrinogen synthesis almost exclusively occurs in the liver. This study investigated the hypothesis that conceptus-derived fibrinogen mediates cell adhesion during fixation. On day 21 of pregnancy, five integrin subunits, including ITGA5, ITGB1, ITGAV, and ITGB1, displayed significantly higher transcript abundance than on day 16 of pregnancy. Endometrial epithelial cells adhered to fibrinogen in an integrin-dependent manner in an in vitro cell adhesion assay. Bilaminar trophoblast and allantochorion expressed fibrinogen transcript, indicating that fibrinogen expression persists past fixation. Preimplantation-phase endometrium, conceptuses, and microcotyledonary tissue expressed components of the clotting cascade regulating fibrin homeostasis, leaving open the possibility that fibrinogen is converted to fibrin. Fibrinogen is likely to have functions beyond mediating cell adhesion, such trapping growth factors and triggering signaling cascades, and has remarkable parallels to the expression of fibrinogen by some tumors. The deposition of fibrinogen within tumor stroma is characteristic of breast carcinoma, and tumor-derived fibrinogen has been implicated in the metastatic potential of circulating tumor cells. DNA methylation of the fibrinogen locus in equine conceptuses was examined in comparison to liver and endometrium, and across the full gene cluster, was significantly higher for endometrium than liver and conceptus. DNA methylation of regulatory regions did not differ between liver and conceptus, and was significantly lower than in endometrium. These results, therefore, support the hypothesis of DNA methylation being a regulator of fibrinogen expression in the conceptus.

Placentation in Equids

This chapter focuses on the early stages of placental development in horses and their relatives in the genus Equus and highlights unique features of equid reproductive biology. The equine placenta is classified as a noninvasive, epitheliochorial type. However, equids have evolved a minor component of invasive trophoblast, the chorionic girdle and endometrial cups, which links the equine placenta with the highly invasive hemochorial placentae of rodents and, particularly, with the primate placenta. Two types of fetus-to-mother signaling in equine pregnancy are mediated by the invasive equine trophoblast cells. First, endocrinological signaling mediated by equine chorionic gonadotrophin (eCG) drives maternal progesterone production to support the equine conceptus between days 40 and 100 of gestation. Only in primates and equids does the placenta produce a gonadotrophin, but the evolutionary paths taken by these two groups of mammals to produce this placental signal were very different. Second, florid expression of paternal major histocompatibility complex (MHC) class I molecules by invading chorionic girdle cells stimulates strong maternal anti-fetal antibody responses that may play a role in the development of immunological tolerance that protects the conceptus from destruction by the maternal immune system. In humans, invasive extravillous trophoblasts also express MHC class I molecules, but the loci involved, and their likely function, are different from those of the horse. Comparison of the cellular and molecular events in these disparate species provides outstanding examples of convergent evolution and co-option in mammalian pregnancy and highlights how studies of the equine placenta have produced new insights into reproductive strategies.

Immunological memory and tolerance at the maternal-fetal interface: Implications for reproductive management of mares

The development of placentation that coincided with the evolution of mammals presented new challenges to the transmission of life from one generation to the next, particularly with regard to the possibility of maternal immunological recognition and destruction of the developing conceptus. The balance between immunity and tolerance dominates the immunological relationship between mother and fetus during mammalian pregnancy, and the focal point of this relationship lies at the interface between the trophoblast cells that comprise the outermost layer of the placenta and the maternal endometrial tissues. Immune memory and tolerance are two of the cardinal characteristics of the immune system. Immune memory is essential in preventing or lessening the effect of infections to the mother or conceptus, but may also be a threat to the semi-allogeneic tissues of the fetus and placenta. The mother must develop functional immune tolerance to her fetus, but at the same time retain her ability to combat infections while pregnant. To address this imperative, mammals have developed overlapping and independent mechanisms for evading maternal anti-fetal immune responses that could result in pregnancy loss. Studies of the unusual component of equine invasive trophoblast in the epitheliochorial placenta have illuminated aspects of immune memory and tolerance that have relevance to fertility in the horse and other mammalian species.

Characterization of the placental transcriptome through mid to late gestation in the mare

The placenta is a dynamic organ which undergoes extensive remodeling throughout pregnancy to support, protect and nourish the developing fetus. Despite the importance of the placenta, very little is known about its gene expression beyond very early pregnancy and post-partum. Therefore, we utilized RNA-sequencing to characterize the transcriptome from the fetal (chorioallantois) and maternal (endometrium) components of the placenta from mares throughout gestation (4, 6, 10, 11 m). Within the endometrium, 47% of genes changed throughout pregnancy, while in the chorioallantois, 29% of genes underwent significant changes in expression. Further bioinformatic analyses of both differentially expressed genes and highly expressed genes help reveal similarities and differences between tissues. Overall, the tissues were more similar than different, with ~ 95% of genes expressed in both tissues, and high similarities between the most highly expressed genes (9/20 conserved), as well as marked similarities between the PANTHER pathways identified. The most highly expressed genes fell under a few broad categories, including endocrine and immune-related transcripts, iron-binding proteins, extracellular matrix proteins, transport proteins and antioxidants. Serine protease inhibitors were particularly abundant, including SERPINA3, 6 and 14, as well as SPINK7 and 9. This paper also demonstrates the ability to effectively separate maternal and fetal components of the placenta, with only a minimal amount of chorioallantoic contamination in the endometrium (~8%). This aspect of equine placentation is a boon for better understanding gestational physiology and allows the horse to be used in areas where a separation of fetal and maternal tissues is essential. Overall, these data represent the first large-scale characterization of placental gene expression in any species and include time points from multiple mid- to late-gestational stages, helping further our understanding of gestational physiology.

Dynamic changes in gene expression and signalling during trophoblast development in the horse

Equine chorionic girdle trophoblast cells play important endocrine and immune functions critical in supporting pregnancy. Very little is known about the genes and pathways that regulate chorionic girdle trophoblast development. Our aim was to identify genes and signalling pathways active in vivo in equine chorionic girdle trophoblast within a critical 7-days window. We exploited the late implantation of the equine conceptus to obtain trophoblast tissue. An Agilent equine 44K microarray was performed using RNA extracted from chorionic girdle and chorion (control) from equine pregnancy days 27, 30, 31 and 34 (n = 5), corresponding to the initiation of chorionic girdle trophoblast proliferation, differentiation and migration. Data were analysed using R packages limma and maSigPro, Ingenuity Pathway Analysis and DAVID and verified using qRT-PCR, promoter analysis, western blotting and migration assays. Microarray analysis showed gene expression (absolute log FC >2, FDR-adjusted P < 0.05) was rapidly and specifically induced in the chorionic girdle between days 27 and 34 (compared to day 27, day 30 = 116, day 31 = 317, day 34 = 781 genes). Pathway analysis identified 35 pathways modulated during chorionic girdle development (e.g. FGF, integrin, Rho GTPases, MAPK) including pathways that have limited description in mammalian trophoblast (e.g. IL-9, CD40 and CD28 signalling). Rho A and ERK/MAPK activity was confirmed as was a role for transcription factor ELF5 in regulation of the CGB promoter. The purity and accessibility of chorionic girdle trophoblast proved to be a powerful resource to identify candidate genes and pathways involved in early equine placental development.

Equine mesenchymal stromal cells from different tissue sources display comparable immune-related gene expression profiles in response to interferon gamma (IFN)-γ

Mesenchymal stromal cells (MSC) have the therapeutic potential to decrease inflammation due to their immunomodulatory properties. They can be isolated from various tissue sources such as bone marrow, adipose tissue, and blood, but it is unknown how the tissue source of origin affects the responses of MSC to inflammatory stimuli. Here, we conceptually addressed this question by evaluating the immune-related gene expression profiles of equine MSC from different tissue sources in response to interferon gamma (IFN-γ) stimulation, with the goal to determine if there is a preferable MSC source for clinical application in an inflammatory environment. The salient findings from this initial study were that the baseline expression of all immune related genes analyzed, with the exception of prostaglandin-endoperoxide synthase 2 (PTGS2), was variable in MSC depending on tissue source. Following IFN-γ stimulation, however, gene expression profiles became more similar across all tissue sources, suggesting that MSC from different sources will likely respond similarly in an inflammatory environment when used clinically.

Inflammatory licensed equine MSCs are chondroprotective and exhibit enhanced immunomodulation in an inflammatory environment

Background

Inflammatory licensed mesenchymal stem cells (MSCs) have the ability to promote functional tissue repair. This study specifically sought to understand how the recipient tissue environment reciprocally affects MSC function. Inflammatory polarized macrophages, modeling an injured tissue environment, were exposed to licensed MSCs, and the resultant effects of MSC immunomodulation and functionality of the MSC secretome on chondrocyte homeostasis were studied.

Methods

Inflammatory licensed MSCs were generated through priming with either IFN-γ or polyinosinic:polycytidylic acid (poly I:C). Macrophages were polarized to an inflammatory phenotype using IFN-γ. Licensed MSCs were co-cultured with inflammatory macrophages and immunomodulation of MSCs was assessed in a T-cell proliferation assay. MSC gene expression was analyzed for changes in immunogenicity (MHC-I, MHC-II), immunomodulation (IDO, PTGS2, NOS2, TGF-β1), cytokine (IL-6, IL-8), and chemokine (CCL2, CXCL10) expression. Macrophages were assessed for changes in cytokine (IL-6, IL-10, TNF-α, IFN-γ) and chemokine (CCL2, CXCL10) expression. Conditioned medium representing the secretome from IFN-γ or poly I:C-primed MSCs was applied to IL-1β-stimulated chondrocytes, which were analyzed for catabolic (IL-6, TNF-α, CCL2, CXCL10, MMP-13, PTGS2) and matrix synthesis (ACAN, COL2A1) genes.

Results

IFN-γ-primed MSCs had a superior ability to suppress T-cell proliferation compared to naïve MSCs, and this ability was maintained following exposure to proinflammatory macrophages. In naïve and licensed MSCs exposed to inflammatory macrophages, MHC-I and MHC-II gene expression was upregulated. The secretome from licensed MSCs was chondroprotective and downregulated inflammatory gene expression in IL-1β-stimulated chondrocytes.

Conclusions

In-vitro inflammatory licensing agents enhanced the immunomodulatory ability of MSCs exposed to inflammatory macrophages, and the resultant secretome was biologically active, protecting chondrocytes from catabolic stimulation. Use of licensing agents produced a more consistent immunomodulatory MSC population compared to exposure to inflammatory macrophages. The clinical implications of this study are that in-vitro licensing prior to therapeutic application could result in a more predictable immunomodulatory and reparative response to MSC therapy compared to in-vivo inflammatory licensing by the recipient environment.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0840-2) contains supplementary material, which is available to authorized users.

Impact of equine assisted reproductive technologies (standard embryo transfer or intracytoplasmic sperm injection (ICSI) with in vitro culture and embryo transfer) on placenta and foal morphometry and placental gene expression

Assisted reproductive technologies (ARTs) such as intracytoplasmic sperm injection (ICSI), in vitro embryo culture and embryo transfer (ET) may be associated with alterations in fetal and placental development. In horses, ET has been used for decades. More recently, in vitro embryo production by ICSI and in vitro culture, followed by embryo transfer (ICSI-C) has become an accepted method for clinical foal production. However, no information is available on the effects of ICSI-C or even of standard ET itself on placental and neonatal parameters in horses. We therefore evaluated placental and neonatal morphology and placental gene expression in reining- and cutting-type American Quarter Horse foals produced using different technologies. Thirty foals and placentas (naturally conceived (NC), ET and ICSI-C; 10 in each group) were examined morphometrically. The only parameter that differed significantly between groups was the length of the foal upper hindlimb, which was longer in ET and ICSI-C than in NC foals. Evaluation of placental mRNA expression for 17 genes related to growth and vascularisation showed no difference in gene expression between groups. These data indicate that within this population, use of ARTs was not associated with meaningful changes in foal or placental morphometry or in expression of the placental genes evaluated.

Placental structure and function in different breeds in horses

Ponies and sometimes draft horses are often used as experimental models for horses although size and metabolic parameters are known to vary between horse breeds. So far, there is little information about differences of placental structure and no information about differences of placental function between breeds. The aim of this study was to investigate differences in placental size, structure and function at birth in relation to foal size and weight in ponies, Saddlebred and draft horses. Pony, Saddlebred and draft horse pregnancies were obtained by artificial insemination over 2 successive breeding seasons. Foals and total fetal membranes (TFM) were weighed and placentas measured for surface area at term. Placentas were sampled above the umbilical cord insertion. Surface density and volume fraction of the different cellular components of the placenta were measured on histological sections using stereology. The expression of genes involved in growth and development, nutrient transfer and vascularization was compared between groups. Foals and TFM were lighter at birth in ponies than Saddlebred horses, and both were lighter compared to draft horses. The surface density and volume fraction of microcotyledonary vessels was increased in pony compared to Saddlebred placentas. The relative expression of genes involved in growth and development was different between breeds and increased with maternal, fetal and placental weight. Primiparous dams produced lighter foals and smaller placentas, associated with a decreased volume fraction of microcotyledonary vessels and genes involved in growth and development and vascularization. Foal sex had little effect on placental structure and function as the expression of only one gene differed according to sex, with EGFR expression being decreased in placentas of females compared to males. In conclusion, foal and placental weight, as well as placental expression of genes involved in growth and development were correlated with maternal size. Placental structure also differed between breeds, with a stronger difference between ponies and both breeds of horses.

The immunomodulatory function of equine MSCs is enhanced by priming through an inflammatory microenvironment or TLR3 ligand

Mesenchymal stem cells (MSCs) have the therapeutic potential to treat a variety of inflammatory and degenerative disease processes, however the effects of the tissue environment on MSCs have been overlooked. Our hypothesis was that the immunomodulatory function of MSCs would be impaired by TLR4 stimulation or exposure to inflammatory macrophages, whereas their immunosuppressive properties would be enhanced by TLR3 stimulation. MSCs were exposed to polyinosinic:polycytidylic acid (poly I:C) to stimulate TLR3 receptors or lipopolysaccharide (LPS) to stimulate TLR4 receptors. MSC1 proinflammatory phenotype in human MSCs was associated with increased IL-6 and IL-8 and MSC2 regenerative phenotype was associated with increased CCL2 and CXCL10. MSC immunomodulatory function was assessed by measuring the ability of primed MSCs to suppress mitogen-stimulated T cell proliferation. Peripheral blood monocytes were isolated using CD14 MACs positive selection, differentiated into macrophages, and polarized using interferon-gamma (IFN-γ). Polarization was confirmed by increased gene expression of TNFα, CCL2, and CXCL10. Inflammatory macrophages were co-cultured with MSCs for 6h, and the resultant MSC phenotype was analyzed as described above. Both TLR3 and TLR4 priming and co-culture of MSCs with inflammatory macrophages resulted in increased expression of IL-6, CCL2, and CXCL10 in MSCs. Both TLR3 and TLR4 priming or exposure of MSCs to inflammatory macrophages significantly (p<0.05) enhanced their immunomodulatory function, demonstrated by a decrease in T cell proliferation in the presence of poly I:C primed MSCs (11%), LPS primed MSCs (7%), or MSCs exposed to inflammatory macrophages (12%), compared to unstimulated MSCs. Additionally, MHC class II positive MSCs tended to have a greater magnitude of response to priming compared to MHC class II negative MSCs. These results suggest that MSCs can be activated by a variety of inflammatory stimuli, but the recipient injured tissue bed in chronic injuries may not contain sufficient inflammatory signals to activate MSC immunomodulatory function. Enhancement of MSCs immunomodulatory function through inflammatory priming prior to clinical application might improve the therapeutic effect of MSC treatments.

Increased circulating Th22 cells correlated with Th17 cells in patients with severe preeclampsia

OBJECTIVE

We aimed to investigate Th22 cells and their association with Th17 and Treg cells in the etiology of severe preeclampsia (sPE).

METHODS

Thirty sPE patients and 30 healthy pregnant women were recruited in this study. The percentages of Th17, Th22, and regulatory T cells (Tregs) in the peripheral blood were measured by flow cytometry. ELISA was used to measure the plasma concentrations of interleukin (IL)-17, IL-22, and IL-10.

RESULTS

The percentages of Th17 and Th22 cells and the plasma concentrations of IL-17 and IL-22 were significantly increased in sPE patients along with a decreased percentage of Treg cells and a decreased plasma IL-10 concentration. There was a positive correlation between the levels of Th22 cells and Th17 cells in sPE patients. Moreover, a positive correlation was found between plasma IL-22 concentration and the percentage of Th22 cells in sPE patients.

CONCLUSIONS

Increased circulating Th22 cells, which were correlated with Th17 cells, were observed in patients with sPE. The immune imbalance between T helper (Th) cells may contribute to the pathogenesis of sPE.

Differential Gene Expression Profiles and Selected Cytokine Protein Analysis of Mediastinal Lymph Nodes of Horses with Chronic Recurrent Airway Obstruction (RAO) Support an Interleukin-17 Immune Response

Recurrent airway obstruction (RAO) is a pulmonary inflammatory condition that afflicts certain mature horses exposed to organic dust particulates in hay. Its clinical and pathological features, manifested by reversible bronchoconstriction, excessive mucus production and airway neutrophilia, resemble the pulmonary alterations that occur in agricultural workers with occupational asthma. The immunological basis of RAO remains uncertain although its chronicity, its localization to a mucosal surface and its domination by a neutrophilic, non-septic inflammatory response, suggest involvement of Interleukin-17 (IL-17). We examined global gene expression profiles in mediastinal (pulmonary-draining) lymph nodes isolated from RAO-affected and control horses. Differential expression of > 200 genes, coupled with network analysis, supports an IL-17 response centered about NF-κB. Immunohistochemical analysis of mediastinal lymph node sections demonstrated increased IL-17 staining intensity in diseased horses. This result, along with the finding of increased IL-17 concentrations in lymph node homogenates from RAO-affected horses (P = 0.1) and a down-regulation of IL-4 gene and protein expression, provides additional evidence of the involvement of IL-17 in the chronic stages of RAO. Additional investigations are needed to ascertain the cellular source of IL-17 in this equine model of occupational asthma. Understanding the immunopathogenesis of this disorder likely will enhance the development of therapeutic interventions beneficial to human and animal pulmonary health.

NK cell abnormality and its treatment in women with reproductive failures such as recurrent pregnancy loss, implantation failures, preeclampsia, and pelvic endometriosis

The regulation of uterine and peripheral blood natural killer (NK) cells has been associated with problems related to reproductive immunology such as recurrent pregnancy loss (RPL), implantation failure or preeclampsia. NKp46, one of the natural cytotoxicity receptors (NCRs), is a unique marker that functions in NK cell cytotoxicity and cytokine production. Expression of NKp46 on NK cells is lower in women with recurrent pregnancy loss and pregnancy-induced hypertension. Moreover, expression of NKp46 on peritoneal fluid NK cells is lower in women with pelvic endometriosis. Therefore, evaluation of NKp46 on peripheral blood NK cells may provide a means of screening for reproductive abnormalities. Recently, a new type of NK cell, the NK22 cell, has been reported. This cell may be a regulator not only of the mucosal barrier but also of reproduction. For women with RPL showing abnormal uterine and/or peripheral blood NK cells, both intravenous immunoglobulin treatment and intralipid treatment have been reported. The effects of these treatments are still controversial, and further studies are needed in order to clarify their true impact. The present review examines variations in the expression of NCRs on NK cells, the participation of NK22 cells in reproduction, and the possible use of intravenous immunoglobulin or intralipid treatment for women with recurrent pregnancy loss and NK cell abnormality.

Interleukin-22: biomarker of maternal and fetal inflammation?

Histologic chorioamnionitis (HCA) is an intrauterine status of inflammation which may lead to the fetal inflammatory response syndrome. Inflammation is a pathogenetic mechanism also of preeclampsia, although not of microbial origin. The aim of the present pilot study was to evaluate the pattern of inflammatory cytokines in mothers and high-risk preterm infants during the perinatal period. Concentrations of proinflammatory and anti-inflammatory cytokines and C-reactive protein were evaluated in maternal, cord, and neonatal blood of very preterm infants <1,500 g birth weight. Histologic examinations of placentae and umbilical cords were performed. The 65 mother-neonate pairs enrolled were subdivided into three groups: (1) HCA group (n = 15), (2) preeclampsia group (n = 17), and (3) control group, in the absence of HCA/preeclampsia (n = 33). Maternal Interleukin (IL)-6 levels were significantly higher in women of the HCA group compared with the preeclampsia and control groups (p < 0.05). IL-22 was detected in nearly all maternal samples [median value 693.115 pg/ml (599.91-809.91 pg/ml)], with no statistical difference between the groups, but with a tendency to increased levels among preeclamptic women. Increased concentrations of IL-22 were detected in cord blood of neonates exposed to preeclampsia, compared with controls and infants exposed to HCA (p < 0.05). We speculate that the tendentially higher concentrations of IL-22 in preeclamptic mothers and the significantly higher concentrations in cord blood may reflect placental dysfunction and the underlying reparative processes at the maternal-fetal interface. Therefore, IL-22 could be an important biomarker of inflammation in preeclampsia.

Uterine responses to the preattachment embryo in domestic ungulates: recognition of pregnancy and preparation for implantation

The endometrium is a tissue newly evolved with the development of mammalian species. Its main function is the support of embryonic growth and development and the nutrition of the fetus. The species-specific differences in establishment and maintenance of pregnancy make the study of this tissue in various mammalian organisms particularly interesting. With the application of omics technologies to various mammalian species, many systematic studies of endometrial gene expression changes during the phase of establishment of pregnancy have been performed to obtain a global view of regulatory events associated with this biological process. This review summarizes the results of trancriptome studies of bovine, porcine, and equine endometrium. Furthermore, the results are compared between these species and to humans. Because an increasing number of studies suggest an important role of small regulatory RNAs (i.e., microRNAs), recent findings related to the regulation of endometrial functions and the development of the conceptus are presented.

SMAD1/5 signaling in the early equine placenta regulates trophoblast differentiation and chorionic gonadotropin secretion

TGFβ superfamily proteins, acting via SMAD (Sma- and Mad-related protein)2/3 pathways, regulate placental function; however, the role of SMAD1/5/8 pathway in the placenta is unknown. This study investigated the functional role of bone morphogenetic protein (BMP)4 signaling through SMAD1/5 in terminal differentiation of primary chorionic gonadotropin (CG)-secreting trophoblast. Primary equine trophoblast cells or placental tissues were isolated from day 27-34 equine conceptuses. Detected by microarray, RT-PCR, and quantitative RT-PCR, equine chorionic girdle trophoblast showed increased gene expression of receptors that bind BMP4. BMP4 mRNA expression was 20- to 60-fold higher in placental tissues adjacent to the chorionic girdle compared with chorionic girdle itself, suggesting BMP4 acts primarily in a paracrine manner on the chorionic girdle. Stimulation of chorionic girdle-trophoblast cells with BMP4 resulted in a dose-dependent and developmental stage-dependent increase in total number and proportion of terminally differentiated binucleate cells. Furthermore, BMP4 treatment induced non-CG-secreting day 31 chorionic girdle trophoblast cells to secrete CG, confirming a specific functional response to BMP4 stimulation. Inhibition of SMAD2/3 signaling combined with BMP4 treatment further enhanced differentiation of trophoblast cells. Phospho-SMAD1/5, but not phospho-SMAD2, expression as determined by Western blotting was tightly regulated during chorionic girdle trophoblast differentiation in vivo, with peak expression of phospho-SMAD1/5 in vivo noted at day 31 corresponding to maximal differentiation response of trophoblast in vitro. Collectively, these experiments demonstrate the involvement of BMP4-dependent pathways in the regulation of equine trophoblast differentiation in vivo and primary trophoblast differentiation in vitro via activation of SMAD1/5 pathway, a previously unreported mechanism of TGFβ signaling in the mammalian placenta.

Applied equine genetics

Genome sequencing of the domestic horse and subsequent advancements in the field of equine genomics have led to an explosion in the development of tools for mapping traits and diseases and evaluating gene expression. The objective of this review is to discuss the current progress in the field of equine genomics, with specific emphasis on assembly and analysis of the reference sequence and subsequent sequencing of a Quarter Horse mare; the genomic tools currently available to researchers and their implications in genomic investigations in the horse; the genomics of Mendelian and non-Mendelian traits; the genomics of performance traits and considerations regarding genetic testing in the horse. The whole-genome sequencing of a Quarter Horse mare has provided additional variants within the equine genome that extend past single nucleotide polymorphisms to include insertions/deletions and copy number variants. Equine single nucleotide polymorphism arrays have allowed for the investigation of both simple and complex genetic traits while DNA microarrays have provided a tool for examining gene expression across various tissues and with certain disease conditions. Recently, next-generation sequencing has become more affordable and both whole-genome DNA sequencing and transcriptome-wide RNA sequencing are methodologies that are being applied to equine genomic research. Research in the field of equine genomics continues to expand rapidly as the cost of genotyping and sequencing decreases, resulting in a need for quality bioinformatics software and expertise to appropriately handle both the size and complexity of these data.

Major histocompatibility complex I mediates immunological tolerance of the trophoblast during pregnancy and may mediate rejection during parturition

During pregnancy in larger mammals, the maternal immune system must tolerate the fetus for months while resisting external infection. This tolerance is facilitated by immunological communication between the fetus and the mother, which is mediated by Major Histocompatibility Complex I (MHC I) proteins, by leukocytes, and by the cytokines secreted by the leukocytes. Fetal-maternal immunological communication also supports pregnancy by inducing physiological changes in the mother. If the mother “misunderstands” the signal sent by the fetus during pregnancy, the fetus will be miscarried or delivered preterm. Unlike any other maternal organ, the placenta can express paternal antigens. At parturition, paternal antigens are known to be expressed in cows and may be expressed in horses, possibly so that the maternal immune system will reject the placenta and help to expel it. This review compares fetal-maternal crosstalk that is mediated by the immune system in three species with pregnancies that last for nine months or longer: humans, cattle, and horses. It raises the possibility that immunological communication early in pregnancy may prepare the mother for successful expulsion of fetal membranes at parturition.

Fibroblast growth factor-2 expression in the preimplantation equine conceptus and endometrium of pregnant and cyclic mares

Uterine-derived growth factors and cytokines play essential roles in regulating preimplantation conceptus development. In several species, fibroblast growth factor-2 (FGF2) promotes embryogenesis, trophoblast cell migration, and adhesion. This study investigated mRNA expression for FGF2, its receptors (FGFR1-4), the activating factor FGF binding protein (FGF-BP) in equine endometrium and trophectoderm during early pregnancy and the estrous cycle, and localized FGF2 protein in both endometrium and conceptus tissues. FGF2, FGFRs1-4, and FGFBP mRNAs were expressed in endometrium throughout the estrous cycle and early pregnancy, and in days 14 to 28 conceptus membranes. FGF2 transcription was higher during estrus than on days 7 or 14 of diestrus, suggesting estrogen dependency. Endometrial expression of FGF2 mRNA and protein increased as pregnancy progressed from days 21 and day 28; FGF2 protein was localized predominantly in the luminal and glandular epithelium. FGF2 mRNA was detectable in trophectoderm from as early as day 14, and transcription and translation increased in day 21 and 28 allantochorion. FGF2 protein was localized mainly in the trophectoderm up to day 21 but was present in both trophectoderm and endoderm of day 28 allantochorion. FGFR1 mRNA was down-regulated in the endometrium at day 7 of diestrus but increased again by day 14. Gene expression for all of the FGFR2 splice variants, including FGFR2IIIc, was up-regulated during estrus. During early pregnancy, endometrial FGFR1 expression decreased, whereas FGFR2IIIc expression did not change. Conceptus mRNA expression for all FGFRs increased as pregnancy progressed. FGFBP expression remained unchanged in endometrium, but increased in the conceptus between days 14 and 28, suggesting a role in regulating FGF2 activity in the developing conceptus. We conclude that during weeks 3 and 4 of pregnancy, the equine endometrial epithelium produces FGF2, which may play a role in trophoblast development and adhesion.

IL-22 secreted by decidual stromal cells and NK cells promotes the survival of human trophoblasts

Interleukin-22 (IL-22) has been implicated as an important immune regulator in many physiologic and pathological processes, but little is known about the IL-22 in the fetal-maternal interface. In this study, we demonstrated that co-culture of decidual stromal cells (DSCs) and decidual natural killer (dNK) cells resulted in increased secretion of IL-22, compared to culture of DSCs or dNK cells alone. The trophoblast cell line, HTR8/SVneo, expresses IL-22 receptor α1 (IL-22R1). Combinant human (rh) IL-22 significantly promoted the proliferation and viability, and inhibited the apoptosis of HTR8/SVneo cells. By Western blotting and immunohistochemistry, we confirmed that villi expressed IL-22R1, and the villi from unexplained spontaneous miscarriage patients expressed reduced levels of IL-22R1 than those from normal early pregnancy. These findings indicate that the IL-22 secreted by DSCs and dNK might promote the survival of trophoblasts and participate in the maintenance of pregnancy by binding to the IL-22R1. The reduced level of IL-22/IL-22R1 in villi might be involved in the occurrence of spontaneous miscarriage.

Early embryonic development, assisted reproductive technologies, and pluripotent stem cell biology in domestic mammals

Over many decades assisted reproductive technologies, including artificial insemination, embryo transfer, in vitro production (IVP) of embryos, cloning by somatic cell nuclear transfer (SCNT), and stem cell culture, have been developed with the aim of refining breeding strategies for improved production and health in animal husbandry. More recently, biomedical applications of these technologies, in particular, SCNT and stem cell culture, have been pursued in domestic mammals in order to create models for human disease and therapy. The following review focuses on presenting important aspects of pre-implantation development in cattle, pigs, horses, and dogs. Biological aspects and impact of assisted reproductive technologies including IVP, SCNT, and culture of pluripotent stem cells are also addressed.

The equine endometrial cup reaction: a fetomaternal signal of significance

A remarkable feature of equine pregnancy is the development of the invasive trophoblast of the chorionic girdle and its formation of the gonadotrophin-secreting endometrial cup cells in early gestation. The details of this process have been revealed only slowly over the past century, since the first description of the endometrial cups in 1912. This centennial presents an opportunity to review the characteristics of the cells and molecules involved in this early, critical phase of placentation in the mare. The invasiveness of the chorionic girdle trophoblast appears to represent an atavistic attribute more commonly associated with the hemochorial placentae of primates and rodents but not with the more recently derived epitheliochorial placentae of the odd-toed ungulates. The nature of and raison d'être for the strong fetal signals transmitted to the mare by the endometrial cup reaction, and her responses to these messages, are the subject of the present review.