New immune horizons in therapeutics and diagnostic approaches to Preeclampsia

Hypertensive disorders of pregnancy (HDP) are one of the commonest maladies, affecting 5%-10% of pregnancies worldwide. The American College of Obstetricians and Gynecologists (ACOG) identifies four categories of HDP, namely gestational hypertension (GH), Preeclampsia (PE), chronic hypertension (CH), and CH with superimposed PE. PE is a multisystem, heterogeneous disorder that encompasses 2%-8% of all pregnancy-related complications, contributing to about 9% to 26% of maternal deaths in low-income countries and 16% in high-income countries. These translate to 50 000 maternal deaths and over 500 000 fetal deaths worldwide, therefore demanding high priority in understanding clinical presentation, screening, diagnostic criteria, and effective management. PE is accompanied by uteroplacental insufficiency leading to vascular and metabolic changes, vasoconstriction, and end-organ ischemia. PE is diagnosed after 20 weeks of pregnancy in women who were previously normotensive or hypertensive. Besides shallow trophoblast invasion and inadequate remodeling of uterine arteries, dysregulation of the nonimmune system has been the focal point in PE. This results from aberrant immune system activation and imbalanced differentiation of T cells. Further, a failure of tolerance toward the semi-allogenic fetus results due to altered distribution of Tregs such as CD4+FoxP3+ or CD4+CD25+CD127(low) FoxP3+ cells, thereby creating a cytotoxic environment by suboptimal production of immunosuppressive cytokines like IL-10, IL-4, and IL-13. Also, intracellular production of complement protein C5a may result in decreased FoxP3+ regulatory T cells. With immune system dysfunction as a major driver in PE pathogenesis, it is logical that therapeutic targeting of components of the immune system with pharmacologic agents like anti-inflammatory and immune-modulating molecules are either being used or under clinical trial. Cholesterol synthesis inhibitors like Pravastatin may improve placental perfusion in PE, while Eculizumab (monoclonal antibody inhibiting C5) and small molecular inhibitor of C5a, Zilucoplan are under investigation. Monoclonal antibody against IL-17(Secukinumab) has been proposed to alter the Th imbalance in PE. Autologous Treg therapy and immune checkpoint inhibitors like anti-CTLA-4 are emerging as new candidates in immune horizons for PE management in the future.

T-Lymphocyte proliferative activity in early pregnancy and outside pregnancy state

T-lymphocytes are present in the endometrium before pregnancy and their number varies depending on menstrual cycle stage. Despite T-lymphocyte population heterogeneity, there is no clear vision of general mechanisms of decidua T-lymphocyte pool formation. One of the assumed variants is T-lymphocyte proliferation in situ. The study objective is to evaluate variations of peripheral blood T-lymphocyte proliferative activity in the presence of trophoblast cells. The peripheral blood was sampled from healthy nonpregnant women in the proliferative (n = 29) and secretory (n = 32) menstrual cycle phases and also from women on 6-7 weeks stage of physiological pregnancy (n = 30). Jeg-3 (ATCC) line cells were applied as trophoblast cells within in vitro model system. T-lymphocyte proliferation was determined by estimating the Ki-67 expression and T-lymphocyte relative number. It was established that trophoblast cells perform inhibiting effect on Ki-67 by T-lymphocytes in all groups of examined women both in course of PBMC cultivation and in case of preliminarily isolated T-lymphocytes. During cultivation in the presence of IL-2 and trophoblasts, PBMC T-lymphocytes in pregnant women are more resistant to trophoblast cells inhibition than in nonpregnant women. In case of isolated T-lymphocytes, decreased T-lymphocyte proliferation during pregnancy was observed as compared to the proliferative cycle phase hence pointing to necessity of T-lymphocyte contact with microenvironment cells for self-support.

Dynamics of Tryptophan Metabolic Pathways in Human Placenta and Placental-Derived Cells: Effect of Gestation Age and Trophoblast Differentiation

L-Tryptophan is an essential amino acid and a precursor of several physiologically active metabolites. In the placenta, the serotonin and kynurenine metabolic pathways of tryptophan metabolism have been identified, giving rise to various molecules of neuroactive or immunoprotective properties, such as serotonin, melatonin, kynurenine, kynurenic acid, or quinolinic acid. Current literature suggests that optimal levels of these molecules in the fetoplacental unit are crucial for proper placenta functions, fetal development and programming. Placenta is a unique endocrine organ that, being equipped with a battery of biotransformation enzymes and transporters, precisely orchestrates homeostasis of tryptophan metabolic pathways. However, because pregnancy is a dynamic process and placental/fetal needs are continuously changing throughout gestation, placenta must adapt to these changes and ensure proper communication in the feto-placental unit. Therefore, in this study we investigated alterations of placental tryptophan metabolic pathways throughout gestation. Quantitative polymerase chain reaction (PCR) analysis of 21 selected genes was carried out in first trimester (n = 13) and term (n = 32) placentas. Heatmap analysis with hierarchical clustering revealed differential gene expression of serotonin and kynurenine pathways across gestation. Subsequently, digital droplet PCR, Western blot, and functional analyses of the rate-limiting enzymes suggest preferential serotonin synthesis early in pregnancy with a switch to kynurenine production toward term. Correspondingly, increased function and/or protein expression of serotonin degrading enzyme and transporters at term indicates efficient placental uptake and metabolic degradation of serotonin. Lastly, gene expression analysis in choriocarcinoma-derived cell lines (BeWo, BeWo b30, JEG-3) revealed dissimilar expression patterns and divergent effect of syncytialization compared to primary trophoblast cells isolated from human term placentas; these findings show that the commonly used in vitro placental models are not suitable to study placental handling of tryptophan. Altogether, our data provide the first comprehensive evidence of changes in placental homeostasis of tryptophan and its metabolites as a function of gestational age, which is critical for proper placental function and fetal development.

Human Tregs at the materno-fetal interface show site-specific adaptation reminiscent of tumor Tregs

Tregs are crucial for maintaining maternal immunotolerance against the semiallogeneic fetus. We investigated the elusive transcriptional profile and functional adaptation of human uterine Tregs (uTregs) during pregnancy. Uterine biopsies, from placental bed (materno-fetal interface) and incision site (control) and blood were obtained from women with uncomplicated pregnancies undergoing cesarean section. Tregs and CD4⁺ non-Tregs were isolated for transcriptomic profiling by Cel-Seq2. Results were validated on protein and single cell levels by flow cytometry. Placental bed uTregs showed elevated expression of Treg signature markers, including FOXP3, CTLA-4, and TIGIT. Their transcriptional profile was indicative of late-stage effector Treg differentiation and chronic activation, with increased expression of immune checkpoints GITR, TNFR2, OX-40, and 4-1BB; genes associated with suppressive capacity (HAVCR2, IL10, LAYN, and PDCD1); and transcription factors MAF, PRDM1, BATF, and VDR. uTregs mirrored non-Treg Th1 polarization and tissue residency. The particular transcriptional signature of placental bed uTregs overlapped strongly with that of tumor-infiltrating Tregs and was remarkably pronounced at the placental bed compared with uterine control site. In conclusion, human uTregs acquire a differentiated effector Treg profile similar to tumor-infiltrating Tregs, specifically at the materno-fetal interface. This introduces the concept of site-specific transcriptional adaptation of Tregs within 1 organ.

Human regulatory T cells at the maternal-fetal interface show uterine site-specific functional adaptation with late-stage effector differentiation, chronic activation, Th1 polarization, and tumor-infiltrating, Treg-like features.

Human Chorionic Gonadotropin-Mediated Immune Responses That Facilitate Embryo Implantation and Placentation

Human chorionic gonadotropin (hCG) serves as one of the first signals provided by the embryo to the mother. Exactly at the time when the first step of the implantation process is initiated and the blastocyst adheres to the maternal endometrium, the embryonic tissue starts to actively secrete hCG. Shortly thereafter, the hormone can be detected in the maternal circulation where its concentration steadily increases throughout early pregnancy as it is continuously released by the forming placenta. Accumulating evidence underlines the critical function of hCG for embryo implantation and placentation. hCG not only regulates biological aspects of these early pregnancy events but also supports maternal immune cells in their function as helpers in the establishment of an adequate embryo-endometrial relationship. In view of its early presence in the maternal circulation, hCG has the potential to influence both local uterine immune cell populations as well as peripheral ones. The current review aims to summarize recent literature on the participation of innate and adaptive immune cells in embryo implantation and placentation with a specific focus on their regulation by hCG.

Effect of intrauterine perfusion of human chorionic gonadotropin before embryo transfer after two or more implantation failures: A systematic review and meta-analysis

OBJECTIVE

To investigate whether intrauterine perfusion of hCG before embryo transfer (ET) is effective in women experienced two or more implantation failures.

STUDY DESIGN

Systematic review and meta-analysis. In the current meta-analysis, Pubmed, EMBASE and The Cochrane Library were searched for trials which compared the efficacy of intrauterine perfusion of hCG with no perfusion of hCG in women undergoing in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), or frozen embryo transfer (FET) before ET. The primary outcomes are the clinical pregnancy rate (CPR) and live birth rate (LBR).

RESULTS

Six trials consisted of 1432 women were eligible for quantitative analysis. CPR (including 6 trials consisted of 1432 women) and LBR (including 3 trials consisted of 870 women) were significantly improved in the hCG group compared to the control group, with a CPR of 41.8 % vs. 31.2 % (RR 1.30, 95 % CI 1.14∼1.50, P < .001), an LBR of 27.8 % vs. 18.0 % (RR 1.52, 95 % CI 1.18∼1.96, P = .001).

CONCLUSION

Intrauterine perfusion of hCG is effective in improving clinical pregnancy rate and live birth rate in women who experienced two or more implantation failures, which might provide a potential therapeutical intervention for recurrent implantation failure (RIF). Although promising, further evidence from multicenter, randomized controlled trials are needed to confirm the conclusion from the current meta-analysis.

Reproductive immunomodulatory functions of B cells in pregnancy

Pregnancy, a challenging physiological state, requires shuffling of conventional immune work-sets. Strategies to tolerate the semi-allogenic fetus in normal human pregnancy are multivariate with perfect modulation of the immune cells. Pregnancy is marked by B cell lymphocytopenia accompanied by reduced responsiveness to infectious agents. Besides this old age concept, plenty of research confirms that B cells have other crucial roles in pregnancy and undergo a wide range of modifications in terms of its proliferation, switching between its subtypes, variation in antibody productions, shifting the tides of cytokines as well as regulating other immune cells. B cells establish tolerant environment in pregnancy by producing protective antibodies to encounter the foreign paternal antigens. Regulatory B cells (Bregs) have adopted anti-inflammatory characteristics to sustain normal pregnancy. Moreover, the colossal physiological alterations during human pregnancy also include synchronized changes in the cross-talks between the pregnancy hormones and B cells. These aspects of pregnancy from the view point of B cell functions have so far appeared individually in discrete reports. This review finds its novelty in concisely presenting every facet of association of B cell with human pregnancy.

A Proteome Approach Reveals Differences between Fertile Women and Patients with Repeated Implantation Failure on Endometrial Level⁻Does hCG Render the Endometrium of RIF Patients?

Background: The molecular signature of endometrial receptivity still remains barely understood, especially when focused on the possible benefit of therapeutical interventions and implantation-related pathologies. Therefore, the protein composition of tissue and isolated primary cells (endometrial stromal cells, ESCs) from endometrial scratchings of ART (Assisted Reproductive Techniques) patients with repeated implantation failure (RIF) was compared to volunteers with proven fertility during the time of embryo implantation (LH + 7). Furthermore, an analysis of the endometrial tissue of fertile women infused with human chorionic gonadotropin (hCG) was conducted. Methods: Endometrial samples (n = 6 RIF, n = 10 fertile controls) were split into 3 pieces: 1/3 each was frozen in liquid nitrogen, 1/3 fixed in PFA and 1/3 cultured. Protein lysates prepared from fresh frozen tissue were processed for mass spectrometric analysis. Results: Three proteins (EPPK1, BCLAF1 and PTMA) showed a statistically altered abundance in the endometrial tissue of RIF patients. Furthermore, pathways like metabolism, immune system, ferroptosis and the endoplasmic reticulum were altered in RIF patients. Remarkably, endometrial tissues of RIF patients showed a significantly higher (p-value = 9 × 10⁻⁸) protein intensity correlation (Pearson’s correlation coefficient = 0.95) compared to fertile women (Pearson’s correlation coefficient = 0.88). The in vivo infusion of hCG stimulated proteins of endocytosis, HIF1 signalling and chemokine production. Notably, patients suffering from RIF had a clinical pregnancy rate of 19% after the intrauterine infusion of hCG before embryo transfer (ET) compared to their failed previous cycles. Conclusion: Our study showed for the first time that the endometrial proteome composition of RIF patients differs from fertile controls during the window of implantation. The intrauterine infusion of hCG prior to an embryo transfer might improve the chemokine triggered embryo-endometrial dialogue and intensify the angiogenesis and immune response. From a clinical point of view, the hCG infusion prior to an embryo transfer might increase the pregnancy rate of RIF patients.

Expression of immune regulatory genes in early, mid and late stages of pig (Sus scrofa domesticus) gestation

Semi-allogeneic foetus and placenta exploit various mechanisms to avoid immune-mediated maternal rejection. Several factors and cytokines are attributed for production of immune tolerance during gestation and very little information on expression of these immune-regulatory genes is available in pig. Chorioallantoic membrane (CAM) from early, mid and late gestational stages (n=4) were analysed for expression of immune regulatory genes, viz. Fas ligand (FasL), transporter for antigen processing-1 (TAP-1), transforming growth factor β1 (TGF-β1) and macrophage migration inhibitory factor (MIF) whereas Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was employed as housekeeping gene. FasL gene expression was significantly higher in mid (13.46 fold) and late (28.77 fold) gestation than the early (1 fold) stage.TAP-1 mRNA expression was enhanced by 4.95 fold and 2.69 fold during mid and late gestation respectively in comparison to the early (1 fold) stage. TGF-β1 gene expression was up regulated in mid (2.43 fold) and late (2.29 fold) gestation than the early (1 fold) stage. MIF mRNA expression was enhanced in mid (3.04 fold) and late (1.59 fold) gestation in relation to the early (1 fold) stage. Placenta of pig remains entirely epitheliochorial which may minimise immune recognition and is supposed to diminish potent immune-regulatory mechanisms. However, our present study revealed consistent expression for immune regulatory factors which suggests immune modulation does exist in pig and may impart a role in pregnancy success.

The role of indoleamine-2,3-dioxygenase in normal and pathological pregnancies

The survival of allogeneic fetus during pregnancy contradicts the laws of immune responses. Behind this paradoxical phenomenon, the mechanism is quite complex. Indoleamine-2,3-dioxygenase (IDO) is the first and rate-limiting enzyme of tryptophan catabolism. Emerging evidence shows that IDO is expressed at the maternal-fetal interface, including trophoblast cells, decidual stroma cells, decidual immune cells (eg, natural killer cells, T cells, and macrophages), and vascular endothelial cells of decidua and chorion. Moreover, the expression and activity of IDO are different among non-pregnant, normal pregnant, and pathological pregnant conditions. IDO plays important roles in normal pregnancy through immune suppression and regulation of fetal invasion and circulation. However, the abnormal expression and dysfunction of IDO are associated with some pathological pregnancies (including recurrent spontaneous abortion, preeclampsia, preterm labor, and fetal growth restriction).

The Role of HCG in Implantation: A Mini-Review of Molecular and Clinical Evidence

Embryo implantation is a complex process involving continuous molecular cross-talk between the embryo and the decidua. One of the key molecules during this process is human chorionic gonadotropin (HCG). HCG effectively modulates several metabolic pathways within the decidua contributing to endometrial receptivity. Herein, a brief overview of the molecular mechanisms regulated by HCG is presented. Furthermore, we summarize the existing evidence regarding the clinical impact on reproductive outcomes after endometrial priming with HCG prior to embryo transfer. Although promising, further evidence is needed to clarify the protocol that would lead to beneficial outcomes.

Prototype and Chimera-Type Galectins in Placentas with Spontaneous and Recurrent Miscarriages

Galectins are galactose binding proteins and, in addition, factors for a wide range of pathologies in pregnancy. We have analyzed the expression of prototype (gal-1, -2, -7, -10) and chimera-type (gal-3) galectins in the placenta in cases of spontaneous abortions (SPA) and recurrent abortions (RA) in the first trimester. Fifteen placental samples from healthy pregnancies were used as a control group. Nine placentas were examined for spontaneous abortions, and 12 placentas for recurrent abortions. For differentiation and evaluation of different cell types of galectin-expression in the decidua, immunofluorescence was used. For all investigated prototype galectins (gal-1, -2, -7, -10) in SPA and RA placenta trophoblast cells the expression is significantly decreased. In the decidua/extravillous trophoblast only gal-2 expression was significantly lowered, which could be connected to its role in angiogenesis. In trophoblasts in first-trimester placentas and in cases of SPA and RA, prototype galectins are altered in the same way. We suspect prototype galectins have a similar function in placental tissue because of their common biochemical structure. Expression of galectin 3 as a chimera type galectin was not found to be significantly altered in abortive placentas.

Trophoblast cells primed with vasoactive intestinal peptide enhance monocyte migration and apoptotic cell clearance through αvβ3 integrin portal formation in a model of maternal-placental interaction

STUDY HYPOTHESIS

Is apoptotic cell phagocytosis by monocytes modulated by pathways elicited by vasoactive intestinal peptide (VIP) action on trophoblast?

STUDY FINDING

Targeting trophoblast cells with VIP induces monocyte migration, polarization to anti-inflammatory phenotypes and apoptotic trophoblast cell clearance which involves increased αvβ3 integrin expression on phagocytic cells and binding to thrombospondin 1.

WHAT IS KNOWN ALREADY

Monocytes recruited to the maternal-placental interface interact with trophoblast cells and differentiate to alternatively activated macrophages involved in the silent clearance of apoptotic cells. Vasoactive intestinal peptide (VIP) is an immunomodulatory polypeptide synthesized at the human placenta that can target both trophoblast cells and monocytes/macrophages. Integrin αvβ3 and thrombospondin 1 are involved in the formation of a phagocytic portal for the immunosuppressant clearance of apoptotic cells.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

This is a laboratory-based study studying monocytes isolated from peripheral blood of healthy women (n = 33) and their interaction in vitro with first trimester trophoblast cell lines. Peripheral blood monocytes were isolated from healthy volunteers by Percoll gradient and tested in co-culture settings with first trimester trophoblast cell lines (Swan 71 and HTR8) or with trophoblast cell conditioned media obtained in the presence or absence of 10 or 100 nM VIP. The effect of VIP-conditioned media on monocyte migration was assessed through transwell systems and monocyte/macrophage phenotype was determined by flow cytometry. Phagocytosis of apoptotic cells and the mechanisms involved in phagocytic portal formation were assessed by flow cytometry, confocal microscopy, immunological blockade and RT-PCR.

MAIN RESULTS AND THE ROLE OF CHANCE

Exposing cells to 100 nM VIP increased the migration of monocytes toward trophoblast cell conditioned media (VIP conditioned medium) (P < 0.05 versus conditioned media from cells not exposed to VIP) and contributed to the monocytes acquiring an anti-inflammatory profile with increased CD39 and IL-10 expression (P < 0.05). Phagocytosis of apoptotic trophoblast cells by monocytes and monocyte-differentiated macrophages was increased by VIP conditioned medium (P < 0.05 versus media conditioned in the absence of VIP or direct addition of 100 nM VIP). The boosting effect of VIP conditioned medium on phagocytosis involved increased expression and re-localization of αvβ3 integrin on phagocytic cells along with enhanced expression of thrombospondin 1 on trophoblast cells.

LIMITATIONS, REASONS FOR CAUTION

The conclusions are based on in vitro experiments with monocytes drawn from peripheral blood of healthy individuals and trophoblast cell lines and we were unable to ascertain that these mechanisms operate similarly in vivo. We cannot rule out a differential behavior of either trophoblast cells targeted in vivo with VIP, or primary cultures of first trimester trophoblast cells assayed in vitro.

WIDER IMPLICATIONS OF THE FINDINGS

The results presented provide new clues for immune and trophoblast cell pharmacological targeting in pregnancy complications of immunopathologic nature.

STUDY FUNDING/COMPETING INTERESTS

This work was funded by the National Agency of Sciences and Technology ANPCyT (PICT 2011-0144), National Research Council CONICET (PIP 602/2012) and University of Buenos Aires (UBACyT 20020130100040BA) to C.P.L. The authors have no conflicts of interest to disclose.

Potential Therapy for Rheumatoid Arthritis and Sjögren Syndrome With Human Chorionic Gonadotropin

Autoimmune diseases such as rheumatoid arthritis (RA) and Sjögren syndrome (SS) ameliorate during pregnancy, through dampening (immunotolerance) of the maternal immune system which protects the fetus from rejection. A large number of studies have shown that human chorionic gonadotropin (hCG) contributes to this tolerance. Studies on animal models have reaffirmed that hCG treatment mimics the benefits of pregnancy. Based on the scientific evidence, randomized clinical trials comparing hCG with current therapies and/or placebo are recommended for RA, SS, and for other autoimmune diseases such as, type 1 diabetes and ankylosing spondylitis, which also get better during pregnancy and hCG treatment seems to help.

Galectins: Double-edged Swords in the Cross-roads of Pregnancy Complications and Female Reproductive Tract Inflammation and Neoplasia

Galectins are an evolutionarily ancient and widely expressed family of lectins that have unique glycan-binding characteristics. They are pleiotropic regulators of key biological processes, such as cell growth, proliferation, differentiation, apoptosis, signal transduction, and pre-mRNA splicing, as well as homo- and heterotypic cell-cell and cell-extracellular matrix interactions. Galectins are also pivotal in immune responses since they regulate host-pathogen interactions, innate and adaptive immune responses, acute and chronic inflammation, and immune tolerance. Some galectins are also central to the regulation of angiogenesis, cell migration and invasion. Expression and functional data provide convincing evidence that, due to these functions, galectins play key roles in shared and unique pathways of normal embryonic and placental development as well as oncodevelopmental processes in tumorigenesis. Therefore, galectins may sometimes act as double-edged swords since they have beneficial but also harmful effects for the organism. Recent advances facilitate the use of galectins as biomarkers in obstetrical syndromes and in various malignancies, and their therapeutic applications are also under investigation. This review provides a general overview of galectins and a focused review of this lectin subfamily in the context of inflammation, infection and tumors of the female reproductive tract as well as in normal pregnancies and those complicated by the great obstetrical syndromes.

Review: hCGs: different sources of production, different glycoforms and functions

Human chorionic gonadotropin (hCG) is the first hormonal message from the placenta to the mother. It is detectable in maternal blood two days after implantation and behaves like an agonist of LH stimulating progesterone secretion by the corpus luteum. hCG has also a role in quiescence of the myometrium and local immune tolerance. Specific to humans, hCG is a complex glycoprotein composed of two glycosylated subunits. The α-subunit is identical to the pituitary gonadotropin hormones (LH, FSH, TSH), contains two N-glycosylation sites, and is encoded by a single gene (CGA). By contrast the β-subunits are distinct in each of the hormones and confer receptor and biological specificity. The hCG β-subunit contains two sites of N-glycosylation and four sites of O-glycosylation and is encoded by a cluster of genes (CGB). In this review, we will stress the importance of hCG glycosylation state, which varies with the stage of pregnancy, its source of production and in the pathology. It is well established that hCG is mainly secreted by the syncytiotrophoblast into maternal blood where it peaks around 8-10 weeks of gestation (WG). The invasive extravillous trophoblast also secretes hCG, and in particular like choriocarcinoma cells, hyperglycosylated forms of hCG (hCG-H). In maternal blood hCG-H is high during early first trimester. In addition to its endocrine role, hCG has autocrine and paracrine roles. It promotes formation of the syncytiotrophoblast and angiogenesis through LHCG receptor. In contrast, hCG-H stimulates trophoblast invasion and angiogenesis by interacting with the TGFβ receptor 2. hCG is largely used in antenatal screening and hCG-H represents a serum marker of early trophoblast invasion. Other abnormally glycosylated hCG are described in aneuploidies. In conclusion, hCG is the major pregnancy glycoprotein hormone, whose maternal concentration and glycan structure change all along pregnancy. Depending on its source of production, glycoforms of hCG display different biological activities and functions that are essential for pregnancy outcome.

Placental Protein 13 (PP13) - A Placental Immunoregulatory Galectin Protecting Pregnancy

Galectins are glycan-binding proteins that regulate innate and adaptive immune responses, and some confer maternal-fetal immune tolerance in eutherian mammals. A chromosome 19 cluster of galectins has emerged in anthropoid primates, species with deep placentation and long gestation. Three of the five human cluster galectins are solely expressed in the placenta, where they may confer additional immunoregulatory functions to enable deep placentation. One of these is galectin-13, also known as Placental Protein 13 (PP13). It has a "jelly-roll" fold, carbohydrate-recognition domain and sugar-binding preference resembling other mammalian galectins. PP13 is predominantly expressed by the syncytiotrophoblast and released from the placenta into the maternal circulation. Its ability to induce apoptosis of activated T cells in vitro, and to divert and kill T cells as well as macrophages in the maternal decidua in situ, suggests important immune functions. Indeed, mutations in the promoter and an exon of LGALS13 presumably leading to altered or non-functional protein expression are associated with a higher frequency of preeclampsia and other obstetrical syndromes, which involve immune dysregulation. Moreover, decreased placental expression of PP13 and its low concentrations in first trimester maternal sera are associated with elevated risk of preeclampsia. Indeed, PP13 turned to be a good early biomarker to assess maternal risk for the subsequent development of pregnancy complications caused by impaired placentation. Due to the ischemic placental stress in preterm preeclampsia, there is increased trophoblastic shedding of PP13 immunopositive microvesicles starting in the second trimester, which leads to high maternal blood PP13 concentrations. Our meta-analysis suggests that this phenomenon may enable the potential use of PP13 in directing patient management near to or at the time of delivery. Recent findings on the beneficial effects of PP13 on decreasing blood pressure due to vasodilatation in pregnant animals suggest its therapeutic potential in preeclampsia.

The role of placental tryptophan catabolism

This review discusses the mechanisms and consequences of degradation of tryptophan (Trp) in the placenta, focusing mainly on the role of indoleamine 2,3-dioxygenase-1 (IDO1), one of three enzymes catalyzing the first step of the kynurenine pathway of Trp degradation. IDO1 has been implicated in regulation of feto-maternal tolerance in the mouse. Local depletion of Trp and/or the presence of metabolites of the kynurenine pathway mediate immunoregulation and exert antimicrobial functions. In addition to the decidual glandular epithelium, IDO1 is localized in the vascular endothelium of the villous chorion and also in the endothelium of spiral arteries of the decidua. Possible consequences of IDO1-mediated catabolism of Trp in the endothelium encompass antimicrobial activity and immunosuppression, as well as relaxation of the placental vasotonus, thereby contributing to placental perfusion and growth of both placenta and fetus. It remains to be evaluated whether other enzymes mediating Trp oxidation, such as indoleamine 2,3-dioxygenase-2, Trp 2,3-dioxygenase, and Trp hydroxylase-1 are of relevance to the biology of the placenta.

The role of pregnancy-associated hormones in the development and function of regulatory B cells

During mammalian pregnancy, highly specialized mechanisms of immune tolerance are triggered in order to allow the semi-allogeneic fetus to grow within the maternal uterus in harmony with the maternal immune system. Among other mechanisms, changes in the endocrine status have been proposed to be at least part of the machinery responsible for the induction of immune tolerance during pregnancy. Indeed, pregnancy-associated hormones, estradiol, progesterone, and human chorionic gonadotropin are known to confer immune suppressive capacity to innate as well as adaptive immune cells. Regulatory B cells, a subpopulation of B lymphocytes with strong immunosuppressive functions, were shown to expand during pregnancy. Furthermore, it is well-known that some women suffering from multiple sclerosis, significantly improve their symptoms during pregnancy and this was attributed to the effect of female sex hormones. Accordingly, estradiol protects mice from developing experimental autoimmune encephalomyelitis by triggering the expansion and activation of regulatory B cells. In this review, we discuss different mechanisms associated with the development, activation, and function of regulatory B cells with a special focus on those involving pregnancy-associated hormones.

Galectin signature in normal pregnancy and preeclampsia

Members of the galectin family are expressed within the female reproductive tract and have been shown to be involved in multiple biological functions that support the progression of pregnancy. Specific expression patterns of different members of this family have been identified at the maternal decidua and on the placental side. In some cases, mechanisms by which galectins exert their functions have been delineated in adverse pregnancy outcomes. This review summarizes studies on galectins that have been documented to be important for pregnancy maintenance, either supporting the maternal adaptation to pregnancy or the placentation process. In addition, we focus our discussion on the role of galectins in preeclampsia, a specific life-threatening pregnancy disorder.

Effect of baicalein on the expression of VIP in extravillous cytotrophoblasts infected with human cytomegalovirus in vitro

This paper aimed to study the ability of baicalein to block human cytomegalovirus (HCMV) infection in extravillous cytotrophoblasts (EVT) and its effect on the vasoactive intestinal peptide (VIP) expression in HCMV-infected EVT in vitro. A human trophoblast cell line (HPT-8) was chosen in this study. HCMV with 100 TCID50 was added into culture medium to infect HPT-8 cells, and then HCMV pp65 antigen was assayed by immunofluorescence staining. The infection status was determined by virus titration. Real-time quantitative polymerase chain reaction (qRT-PCR) was used to detect virus DNA load in the infected cells. The expression of VIP mRNA and protein in the infected cells was measured by qRT-PCR, immunocytochemistry and Western blotting. Concentration of VIP secreted in supernatants was determined by ELISA. Red-stained HCMV pp65 antigens were found in infected HPT-8 cells 48 h after infection. HCMV replicated in large quantity in infected HPT-8 cells 4 days after infection, reaching a peak at day 6 post-infection. After treatment with baicalein, virus DNA load in infected HPT-8 cells was decreased (P<0.05), and the levels of VIP mRNA and protein, and the concentration were raised to the normal (P>0.05). Our study suggested that baicalein exerts a positive effect on the VIP expression in HCMV-infected EVT at maternal-fetal interface.

Mechanism of human chorionic gonadotrophin-mediated immunomodulation in pregnancy

Human chorionic gonadotrophin (hCG) is released within hours of fertilization and has a profound ability to downregulate maternal cellular immunity against trophoblastic paternal antigens. It also promotes angiogenic activity of the extravillous trophoblast, and impairment of this function may lead to inadequate placentation and an increased risk of preeclampsia. There is increasing evidence that hCG alters the activity of dendritic cells via an upregulation of indoleamine 2,3-dioxygenase activity. This reduces T-cell activation and cytokine production, as well as encouraging Treg cell recruitment to the fetal-maternal interface. These changes are critical in promoting maternal tolerance. hCG is also able to increase the proliferation of uterine natural killer cells, while reducing the activity of cytotoxic peripheral blood natural killer cells. There are rare reports of autoantibodies directed against hCG or the luteinizing hormone/hCG receptor in women with recurrent miscarriage. These autoantibodies are more frequent in women with thyroid autoimmunity. This may explain the association between thyroid autoimmunity and impaired fertility. Downregulating these anti-hCG and anti-luteinizing hormone/hCG receptor autoantibodies may be helpful in some women with early miscarriage or recurrent failed in vitro fertilization.

The Placenta in Toxicology. Part II

During pregnancy, the maternal immune system is challenged by the semiallogeneic fetus, which must be tolerated without compromising fetal or maternal health. This review updates the systemic and local immune changes taking place during human pregnancy, including some examples in rodents. Systemic changes are induced by contact of maternal blood with placental factors and include enhanced innate immunity with increased activation of granulocytes and nonclassical monocytes. Although a bias toward T helper (Th2) and regulatory T cell (Treg) immunity has been associated with healthy pregnancy, the relationship between different circulating Th cell subsets is not straightforward. Instead, these adaptations appear most evidently at the fetal–maternal interface, where for instance Tregs are enriched and promote fetal tolerance. Also innate immune cells, that is, natural killer cells and macrophages, are enriched, constituting the majority of decidual leukocytes. These cells not only contribute to immune regulation but also aid in establishing the placenta by promoting trophoblast recruitment and angiogenesis. Thus, proper interaction between leukocytes and placental trophoblasts is necessary for normal placentation and immune adaptation. Consequently, spontaneous maladaptation or interference of the immune system with toxic substances may be important contributing factors for the development of pregnancy complications such as preeclampsia, preterm labor, and recurrent miscarriages.

Expanded protein expression profile of human placenta using two-dimensional gel electrophoresis

Studying proteins expressed in placenta is important to understand its function in pregnancy and fetal growth. Here, we present protein expression profiling from normal human placenta by 2-D gel - MS/MS approach that resulted in identification of 117 unique proteins. Integration with earlier analyses resulted in a profile of 423 non-redundant proteins, 75 of them being new identifications unique to this study including their isoforms. We present a compilation of placental protein expressions identified by proteomic approaches, their functions and known clinical implications. We believe that our dataset would be a useful resource for studies related to placental dysfunction.

Galectin-1 confers immune privilege to human trophoblast: implications in recurrent fetal loss

Mechanisms accounting for the protection of the fetal semi-allograft from maternal immune cells remain incompletely understood. In previous studies, we showed that galectin-1 (Gal1), an immunoregulatory glycan-binding protein, hierarchically triggers a cascade of tolerogenic events at the mouse fetomaternal interface. Here, we show that Gal1 confers immune privilege to human trophoblast cells through the modulation of a number of regulatory mechanisms. Gal1 was mainly expressed in invasive extravillous trophoblast cells of human first trimester and term placenta in direct contact with maternal tissue. Expression of Gal1 by the human trophoblast cell line JEG-3 was primarily controlled by progesterone and pro-inflammatory cytokines and impaired T-cell responses by limiting T cell viability, suppressing the secretion of Th1-type cytokines and favoring the expansion of CD4(+)CD25(+)FoxP3(+) regulatory T (T(reg)) cells. Targeted inhibition of Gal1 expression through antibody (Ab)-mediated blockade, addition of the specific disaccharide lactose or retroviral-mediated siRNA strategies prevented these immunoregulatory effects. Consistent with a homeostatic role of endogenous Gal1, patients with recurrent pregnancy loss showed considerably lower levels of circulating Gal1 and had higher frequency of anti-Gal1 auto-Abs in their sera compared with fertile women. Thus, endogenous Gal1 confers immune privilege to human trophoblast cells by triggering a broad tolerogenic program with potential implications in threatened pregnancies.

Galectins: guardians of eutherian pregnancy at the maternal-fetal interface

Galectins are multifunctional regulators of fundamental cellular processes. They are also involved in innate and adaptive immune responses, and play a functional role in immune-endocrine crosstalk. Some galectins have attracted attention in the reproductive sciences because they are highly expressed at the maternal-fetal interface, their functional significance in eutherian pregnancies has been documented, and their dysregulated expression is observed in the 'great obstetrical syndromes'. The evolution of these galectins has been linked to the emergence of eutherian mammals. Based on published evidence, galectins expressed at the maternal-fetal interface may serve as important proteins involved in maternal-fetal interactions, and the study of these galectins may facilitate the prediction, prevention, diagnosis, and treatment of pregnancy complications.

Placental trophoblasts shifted Th1/Th2 balance toward Th2 and inhibited Th17 immunity at fetomaternal interface

The aims were to clarify the effect of placental trophoblasts on T lymphocytes by assessing production of cytokines and expression of transcription factors regulating Th1, Th2, and Th17 immunity in T lymphocytes. Placental trophoblasts were isolated and conditioned medium was made after trophoblast cultivation for 72 h. T lymphocytes were cultured in presence or absence of conditioned medium. ELISA was used to detect concentration of IL-2, TNF-α, IFN-γ, IL-4, IL-10, and IL-17 in supernatants of T cell and real-time PCR was used to detect the status of Th1 (T-bet, STAT-4), Th2 (GATA-3, STAT-6), and Th17 (RORC) immunity in T lymphocyte. We found that the level of IL-2, IFN-γ, TNF-α, and IL-17 was significantly decreased when T lymphocytes were cultured in conditioned medium compared with control, while IL-10 and IL-4 level were not significantly changed. The presence of conditioned medium significantly decreased the ratio of Th1/Th2. The expression of GATA-3 and STAT-6 were significantly increased and STAT-4 was reduced when T lymphocyte was cultured in conditioned medium, while the expression of T-bet and RORC was not significantly different. We concluded that placental trophoblast-induced shift of Th1/Th2 balance toward Th2 and inhibition of Th17 might be among the mechanisms involved in maternal tolerance to fetus.

Vascular endothelial expression of indoleamine 2,3-dioxygenase 1 forms a positive gradient towards the feto-maternal interface

We describe the distribution of indoleamine 2,3-dioxygenase 1 (IDO1) in vascular endothelium of human first-trimester and term placenta. Expression of IDO1 protein on the fetal side of the interface extended from almost exclusively sub-trophoblastic capillaries in first-trimester placenta to a nearly general presence on villous vascular endothelia at term, including also most bigger vessels such as villous arteries and veins of stem villi and vessels of the chorionic plate. Umbilical cord vessels were generally negative for IDO1 protein. In the fetal part of the placenta positivity for IDO1 was restricted to vascular endothelium, which did not co-express HLA-DR. This finding paralleled detectability of IDO1 mRNA in first trimester and term tissue and a high increase in the kynurenine to tryptophan ratio in chorionic villous tissue from first trimester to term placenta. Endothelial cells isolated from the chorionic plate of term placenta expressed IDO1 mRNA in contrast to endothelial cells originating from human umbilical vein, iliac vein or aorta. In first trimester decidua we found endothelium of arteries rather than veins expressing IDO1, which was complementory to expression of HLA-DR. An estimation of IDO activity on the basis of the ratio of kynurenine and tryptophan in blood taken from vessels of the chorionic plate of term placenta indicated far higher values than those found in the peripheral blood of adults. Thus, a gradient of vascular endothelial IDO1 expression is present at both sides of the feto-maternal interface.

A balancing act: mechanisms by which the fetus avoids rejection by the maternal immune system

Successful pregnancy requires strict temporal regulation of maternal immune function to accommodate the growing fetus. Early implantation is facilitated by inflammatory processes that ensure adequate vascular remodeling and placental invasion. To prevent rejection of the fetus, this inflammation must be curtailed; reproductive immunologists are discovering that this process is orchestrated by the fetal unit and, in particular, the extravillous trophoblast. Soluble and particulate factors produced by the trophoblast regulate maternal immune cells within the decidua, as well as in the periphery. The aim of this review is to discuss the action of recently discovered immunomodulatory factors and mechanisms, and the potential effects of dysregulation of such mechanisms on the maternal immune response that may result in pregnancy loss or preeclampsia.

In vitro study on human cytomegalovirus affecting early pregnancy villous EVT's invasion function

Background

Human cytomegalovirus (HCMV) is the most common pathogen in uterus during pregnancy, which may lead to some serious results such as miscarriage, stillbirth, cerebellar malformation, fetus developmental retardation, but its pathogenesis has not been fully explained. The hypofunction of extravillous cytotrophoblast (EVT) invasion is the essential pathologic base of some complications of pregnancy. c-erbB-2 is a kind of oncogene protein and closely linked with embryogenesis, tissue repair and regeneration. Matrix metalloproteinase (MMP) is one of the key enzymes which affect EVT migration and invasion function. The expression level changes of c-erbB-2, MMP-2 and MMP-9 can reflect the changes of EVT invasion function.

Results

To explore the influence of HCMV on the invasion function of EVT, we tested the protein expression level changes of c-erbB-2, MMP-2 and MMP-9 in villous explant cultured in vitro infected by HCMV, with the use of immunohistochemistry SP method and western blot. We confirmed that HCMV can reproduce and spread in early pregnancy villus; c-erbB-2 protein mainly expressed in normal early pregnancy villous syncytiotrophoblast (ST) remote plasma membrane and EVT, especially remote EVT cell membrane in villous stem cell column, little expressed in ST proximal end cell membrane and interstitial cells; MMP-2 protein primarily expressed in early pregnancy villous EVT endochylema and rarely in villous trophoblast (VT), ST and interstitial cells; MMP-9 protein largely expressed in early pregnancy villous mesenchyme, EVT and VT endochylema. Compared with control group, the three kinds of protein expression level in early pregnancy villus of virus group significantly decreased (P < 0.05).

Conclusion

HCMV can infect villus in vitro and cause the decrease of early pregnancy villous EVT's invasion function.

Cancer and pregnancy: parallels in growth, invasion, and immune modulation and implications for cancer therapeutic agents

Many proliferative, invasive, and immune tolerance mechanisms that support normal human pregnancy are also exploited by malignancies to establish a nutrient supply and evade or edit the host immune response. In addition to the shared capacity for invading through normal tissues, both cancer cells and cells of the developing placenta create a microenvironment supportive of both immunologic privilege and angiogenesis. Systemic alterations in immunity are also detectable, particularly with respect to a helper T cell type 2 polarization evident in advanced cancers and midtrimester pregnancy. This review summarizes the similarities between growth and immune privilege in cancer and pregnancy and identifies areas for further investigation. Our PubMed search strategy included combinations of terms such as immune tolerance, pregnancy, cancer, cytokines, angiogenesis, and invasion. We did not place any restrictions on publication dates. The knowledge gained from analyzing similarities and differences between the physiologic state of pregnancy and the pathologic state of cancer could lead to identification of new potential targets for cancer therapeutic agents.