Expression and activity of Toll-like receptors 1-9 in the human term placenta and changes associated with labor at term

Establishment and comparison of human term placenta-derived trophoblast cells†

Research on the biology of fetal-maternal barriers has been limited by access to physiologically relevant cells, including trophoblast cells. In this study, we describe the development of a human term placenta-derived cytotrophoblast immortalized cell line (hPTCCTB) derived from the basal plate. Human-term placenta-derived cytotrophoblast immortalized cell line cells are comparable to their primary cells of origin in terms of morphology, marker expression, and functional responses. We demonstrate that these can transform into syncytiotrophoblast and extravillous trophoblasts. We also compared the hPTCCTB cells to immortalized chorionic trophoblasts (hFM-CTC), trophoblasts of the chorionic plate, and BeWo cells, choriocarcinoma cell lines of conventional use. Human-term placenta-derived cytotrophoblast immortalized cell line and hFM-CTCs displayed more similarity to each other than to BeWos, but these differ in syncytialization ability. Overall, this study (1) demonstrates that the immortalized hPTCCTB generated are cells of higher physiological relevance and (2) provides a look into the distinction between the spatially distinct placental and fetal barrier trophoblasts cells, hPTCCTB and hFM-CTC, respectively.

Infection and disruption of placental multidrug resistance (MDR) transporters: Implications for fetal drug exposure

P-glycoprotein (P-gp, encoded by the ABCB1 gene) and breast cancer resistance protein (BCRP/ABCG2) are efflux multidrug resistance (MDR) transporters localized at the syncytiotrophoblast barrier of the placenta and protect the conceptus from drug and toxin exposure throughout pregnancy. Infection is an important modulator of MDR expression and function. This review comprehensively examines the effect of infection on the MDR transporters, P-gp and BCRP in the placenta. Infection PAMPs such as bacterial lipopolysaccharide (LPS) and viral polyinosinic-polycytidylic acid (poly I:C) and single-stranded (ss)RNA, as well as infection with Zika virus (ZIKV), Plasmodium berghei ANKA (modeling malaria in pregnancy - MiP) and polymicrobial infection of intrauterine tissues (chorioamnionitis) all modulate placental P-gp and BCRP at the levels of mRNA, protein and or function; with specific responses varying according to gestational age, trophoblast type and species (human vs. mice). Furthermore, we describe the expression and localization profile of Toll-like receptor (TLR) proteins of the innate immune system at the maternal-fetal interface, aiming to better understand how infective agents modulate placental MDR. We also highlight important gaps in the field and propose future research directions. We conclude that alterations in placental MDR expression and function induced by infective agents may not only alter the intrauterine biodistribution of important MDR substrates such as drugs, toxins, hormones, cytokines, chemokines and waste metabolites, but also impact normal placentation and adversely affect pregnancy outcome and maternal/neonatal health.

Animal Models of Preeclampsia: Mechanistic Insights and Promising Therapeutics

Preeclampsia (PE) is a common pregnancy-specific disorder that is a major cause of both maternal and fetal morbidity and mortality. Central to the pathogenesis of PE is the production of antiangiogenic and inflammatory factors by the hypoxic placenta, leading to the downstream manifestations of the disease, including hypertension and end-organ damage. Currently, effective treatments are limited for PE; however, the development of preclinical animal models has helped in the development and evaluation of new therapeutics. In this review, we will summarize some of the more commonly used models of PE and highlight their similarities to the human syndrome, as well as the therapeutics tested in each model.

Association of Single Nucleotide Polymorphisms from Angiogenesis-Related Genes, ANGPT2, TLR2 and TLR9, with Spontaneous Preterm Labor

In this study, we hypothesized that the changes localized at angiopoietin-2 (ANGPT2), granulocyte-macrophage colony-stimulating factor (CSF2), fms-related tyrosine kinase 1 (FLT1) and toll-like receptor (TLR) 2, TLR6 and TLR9 genes were associated with spontaneous preterm labor (PTL), as well as with possible genetic alterations on PTL-related coagulation. This case-control genetic association study aimed to identify single nucleotide polymorphisms (SNPs) for the aforementioned genes, which are correlated with genetic risk or protection against PTL in Polish women. The study was conducted in 320 patients treated between 2016 and 2020, including 160 women with PTL and 160 term controls in labor. We found that ANGPT2 rs3020221 AA homozygotes were significantly less common in PTL cases than in controls, especially after adjusting for activated partial thromboplastin time (APTT) and platelet (PLT) parameters. TC heterozygotes for TLR2 rs3804099 were associated with PTL after correcting for anemia, vaginal bleeding, and history of threatened miscarriage or PTL. TC and CC genotypes in TLR9 rs187084 were significantly less common in women with PTL, compared to the controls, after adjusting for bleeding and gestational diabetes. For the first time, it was shown that three polymorphisms-ANGPT2 rs3020221, TLR2 rs3804099 and TLR9 rs187084 -were significantly associated with PTL, adjusted by pregnancy development influencing factors.

Distinct trans-placental effects of maternal immune activation by TLR3 and TLR7 agonists: implications for schizophrenia risk

Exposure to infection in utero predisposes towards psychiatric diseases such as autism, depression and schizophrenia in later life. The mechanisms involved are typically studied by administering mimetics of double-stranded (ds) virus or bacterial infection to pregnant rats or mice. The effect of single-stranded (ss) virus mimetics has been largely ignored, despite evidence linking prenatal ss virus exposure with psychiatric disease. Understanding the effects of gestational ss virus exposure has become even more important with recent events. In this study, in pregnant mice, we compare directly the effects, on the maternal blood, placenta and the embryonic brain, of maternal administration of ds-virus mimetic poly I:C (to activate Toll-like receptor 3, TLR3) and ss-virus mimetic resiquimod (to activate TLR7/8). We find that, 4 h after the administration, both poly I:C and resiquimod elevated the levels of IL-6, TNFα, and chemokines including CCL2 and CCL5, in maternal plasma. Both agents also increased placental mRNA levels of IL-6 and IL-10, but only resiquimod increased placental TNFα mRNA. In foetal brain, poly I:C produced no detectable immune-response-related increases, whereas pronounced increases in cytokine (e.g. Il-6, Tnfα) and chemokine (e.g. Ccl2, Ccl5) expression were observed with maternal resiquimod administration. The data show substantial differences between the effect of maternal exposure to a TLR7/8 activator as compared to a TLR3 activator. There are significant implications for future modelling of diseases where maternal ss virus exposure contributes to environmental disease risk in offspring.

Targeting TBK1 Attenuates LPS-Induced NLRP3 Inflammasome Activation by Regulating of mTORC1 Pathways in Trophoblasts

Pathological maternal inflammation and abnormal placentation contribute to several pregnancy-related disorders, including preterm birth, intrauterine growth restriction, and preeclampsia. TANK-binding kinase 1 (TBK1), a serine/threonine kinase, has been implicated in the regulation of various physiological processes, including innate immune response, autophagy, and cell growth. However, the relevance of TBK1 in the placental pro-inflammatory environment has not been investigated. In this study, we assessed the effect of TBK1 inhibition on lipopolysaccharide (LPS)-induced NLRP3 inflammasome activation and its underlying mechanisms in human trophoblast cell lines and mouse placenta. TBK1 phosphorylation was upregulated in the trophoblasts and placenta in response to LPS. Pharmacological and genetic inhibition of TBK1 in trophoblasts ameliorated LPS-induced NLRP3 inflammasome activation, placental inflammation, and subsequent interleukin (IL)-1 production. Moreover, maternal administration of amlexanox, a TBK1 inhibitor, reversed LPS-induced adverse pregnancy outcomes. Notably, TBK1 inhibition prevented LPS-induced NLRP3 inflammasome activation by targeting the mammalian target of rapamycin complex 1 (mTORC1). Thus, this study provides evidence for the biological significance of TBK1 in placental inflammation, suggesting that amlexanox may be a potential therapeutic candidate for treating inflammation-associated pregnancy-related complications.

A review of key cytokines based on gene polymorphism in the pathogenesis of pre-eclampsia

Although a number of theories have been suggested, including roles for oxidative stress, an abnormal maternal-fetal interface, and genetic and environmental factors, the etiopathology of pre-eclampsia (PE) remains unclear. Maternal immune tolerance is important for maintaining pregnancy, and researchers have increasingly focused on the critical roles of cytokines in the pathogenesis of PE in recent years. The assessment of candidate genetic polymorphisms in PE could partially elucidate the mechanisms of susceptibility to disease, and contribute to seeking for new diagnosis and treatment methods of PE. PE can lead to severe complications, and even the death of both mother and fetus. Although the complex pathology is not yet clear, some evidence suggested that the occurrence of PE is related to inflammatory factors. We reviewed the current understandings of roles of cytokines in PE, and provided an extensive overview of the role of single nucleotide chain polymorphisms (SNPs) in the genes potentially underlying the pathophysiology of PE.

Association Between TLR4 Gene Polymorphisms and Risk of Preeclampsia: Systematic Review and Meta-Analysis

BACKGROUND Toll-like receptor 4 (TLR4) plays a pivotal role in the innate immune response and is hyperactivated in preeclampsia (PE). Several researchers have published conflicting evidence for TLR4 rs4986790 and rs4986791 single nucleotide polymorphisms (SNPs) as risk factors for PE. The present meta-analysis was conducted to obtain a more definitive conclusion about the effects of these SNPs on PE susceptibility. MATERIAL AND METHODS To determine the correlation between rs4986790 and rs4986791 polymorphisms in the TLR4 gene and susceptibility to PE, the PubMed, Web of Science, EMBASE, Chinese National Knowledge Infrastructure, and Chinese WANFANG databases were searched for eligible articles. Statistical analysis was performed with STATA software, version 12.0. Pooled odds ratios with corresponding 95% confidence intervals (CIs) were extracted for assessment of correlation strength. RESULTS We identified 5 studies including 578 cases and 631 controls for the rs4986790 SNP and 4 studies including 469 cases and 457 controls for the rs4986791 SNP, mainly from a White population. The pooled analyses showed no statistical relationship between the polymorphisms rs4986790 and rs4986791 and PE susceptibility in 5 genetic models (all P>0.05). Moreover, the allelic and dominant gene models of rs4986790 and the allelic, heterozygous, and dominant gene models of rs4986791 had high heterogeneity. The sensitivity analysis explored potential sources of heterogeneity and confirmed the findings of this meta-analysis. CONCLUSIONS TLR4 rs4986790 and rs4986791 polymorphisms may not be implicated in PE susceptibility, primarily in a White population. More high-quality studies of genetic associations with PE are warranted.

The Immunology of Syncytialized Trophoblast

Multinucleate syncytialized trophoblast is found in three forms in the human placenta. In the earliest stages of pregnancy, it is seen at the invasive leading edge of the implanting embryo and has been called primitive trophoblast. In later pregnancy, it is represented by the immense, multinucleated layer covering the surface of placental villi and by the trophoblast giant cells found deep within the uterine decidua and myometrium. These syncytia interact with local and/or systemic maternal immune effector cells in a fine balance that allows for invasion and persistence of allogeneic cells in a mother who must retain immunocompetence for 40 weeks of pregnancy. Maternal immune interactions with syncytialized trophoblast require tightly regulated mechanisms that may differ depending on the location of fetal cells and their invasiveness, the nature of the surrounding immune effector cells and the gestational age of the pregnancy. Some specifically reflect the unique mechanisms involved in trophoblast cell–cell fusion (aka syncytialization). Here we will review and summarize several of the mechanisms that support healthy maternal–fetal immune interactions specifically at syncytiotrophoblast interfaces.

Insight into the expression of RIG-I-like receptors in human third trimester placentas following ex vivo cytomegalovirus or vesicular stomatitis virus infection

A viral infection is detected through germline-encoded pattern-recognition receptors (PRRs) leading to the production of interferons (IFNs) and proinflammatory cytokines. The objective of this study was to investigate the expression of retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) in response to viral infection and the selected cytokine responses in the human term placenta. Placental villi and decidual explants were infected with human cytomegalovirus (CMV) or vesicular stomatitis virus (VSV) and cultured ex vivo to study viral infection. To evaluate DDX58 (RIG-I), IFIH1 (MDA5), and DHX58 (LGP2) expression, quantitative real-time PCR (qRT-PCR) was used. The expression of RLRs was detected by Western blotting. Cytokine and chemokine production, as well as RLR protein levels, were quantified using ELISA. The increased expression of both RIG-I and MDA5 and the enhanced secretion of IFN-ß were observed in response to VSV infection compared to mock-infected tissues. CMV infection resulted in higher transcript levels of DDX58 and IFIH1, while no changes in the cytokine production were observed. Our results indicate that RIG-I and MDA5 are specifically expressed in chorionic villi and deciduae in response to VSV infection. These findings suggest that RLRs may play a key role in pathogen recognition and the immune response against intrauterine viral transmission.

Innate Immune Responses to Acute Viral Infection During Pregnancy

Immunological adaptations in pregnancy allow maternal tolerance of the semi-allogeneic fetus but also increase maternal susceptibility to infection. At implantation, the endometrial stroma, glands, arteries and immune cells undergo anatomical and functional transformation to create the decidua, the specialized secretory endometrium of pregnancy. The maternal decidua and the invading fetal trophoblast constitute a dynamic junction that facilitates a complex immunological dialogue between the two. The decidual and peripheral immune systems together assume a pivotal role in regulating the critical balance between tolerance and defense against infection. Throughout pregnancy, this equilibrium is repeatedly subjected to microbial challenge. Acute viral infection in pregnancy is associated with a wide spectrum of adverse consequences for both mother and fetus. Vertical transmission from mother to fetus can cause developmental anomalies, growth restriction, preterm birth and stillbirth, while the mother is predisposed to heightened morbidity and maternal death. A rapid, effective response to invasive pathogens is therefore essential in order to avoid overwhelming maternal infection and consequent fetal compromise. This sentinel response is mediated by the innate immune system: a heritable, highly evolutionarily conserved system comprising physical barriers, antimicrobial peptides (AMP) and a variety of immune cells—principally neutrophils, macrophages, dendritic cells, and natural killer cells—which express pattern-receptors that detect invariant molecular signatures unique to pathogenic micro-organisms. Recognition of these signatures during acute infection triggers signaling cascades that enhance antimicrobial properties such as phagocytosis, secretion of pro-inflammatory cytokines and activation of the complement system. As well as coordinating the initial immune response, macrophages and dendritic cells present microbial antigens to lymphocytes, initiating and influencing the development of specific, long-lasting adaptive immunity. Despite extensive progress in unraveling the immunological adaptations of pregnancy, pregnant women remain particularly susceptible to certain acute viral infections and continue to experience mortality rates equivalent to those observed in pandemics several decades ago. Here, we focus specifically on the pregnancy-induced vulnerabilities in innate immunity that contribute to the disproportionately high maternal mortality observed in the following acute viral infections: Lassa fever, Ebola virus disease (EVD), dengue fever, hepatitis E, influenza, and novel coronavirus infections.

Porphyromonas gulae lipopolysaccharide elicits inflammatory responses through toll-like receptor 2 and 4 in human gingivalis epithelial cells

Porphyromonas gulae, a Gram-negative black-pigmented anaerobe, has been associated with periodontal disease in companion animals and its virulence has been attributed to various factors, including lipopolysaccharide (LPS), protease and fimbriae. Toll-like receptors (TLRs) recognise pathogen-associated molecular patterns, such as peptidoglycan, lipids, lipoproteins, nucleic acid and LPS. Following P. gulae infection, some inflammatory responses are dependent on both TLR2 and TLR4. In addition, a recent clinical study revealed that acute and persistent inflammatory responses enhance the expressions of TLR2 and TLR4 in the oral cavity. In this study, we investigated the interaction between P. gulae LPS and human gingivalis epithelial cells (Ca9-22 cells). P. gulae LPS was found to increase TLR2 and TLR4 mRNA expressions and protein productions, and enhanced inflammatory responses, such as COX₂ , TNF-ɑ, IL-6 and IL-8. Stimulated Ca9-22 cells exhibited phosphorylation of ERK1/2 and p38, and their inhibitors diminished inflammatory responses, while knockdown of the TLR2 and/or TLR4 genes with small interfering RNA (siRNA) prevented inflammatory responses. Moreover, p38 and ERK1/2 phosphorylation was decreased in TLR2 and TLR4 gene knockdown cells. These findings suggest that P. gulae LPS activates p38 and ERK1/2 via TLR2 and TLR4, leading to inflammatory responses in human gingival epithelial cells.

Pathogenesis of preterm birth: bidirectional inflammation in mother and fetus

Preterm birth (PTB) complicates 5–18% of pregnancies globally and is a leading cause of maternal and fetal morbidity and mortality. Most PTB is spontaneous and idiopathic, with largely undefined causes. To increase understanding of PTB, much research in recent years has focused on using animal models to recapitulate the pathophysiology of PTB. Dysfunctions of maternal immune adaptations have been implicated in a range of pregnancy pathologies, including PTB. A wealth of evidence arising from mouse models as well as human studies is now available to support that PTB results from a breakdown in fetal-maternal tolerance, along with excessive, premature inflammation. In this review, we examine the current knowledge of the bidirectional communication between fetal and maternal systems and its role in the immunopathogenesis of PTB. These recent insights significantly advance our understanding of the pathogenesis of PTB, which is essential to ultimately designing more effective strategies for early prediction and subsequent prevention of PTB.

Differential Response of Gestational Tissues to TLR3 Viral Priming Prior to Exposure to Bacterial TLR2 and TLR2/6 Agonists

Background: Infection/inflammation is an important causal factor in spontaneous preterm birth (sPTB). Most mechanistic studies have concentrated on the role of bacteria, with limited focus on the role of viruses in sPTB. Murine studies support a potential multi-pathogen aetiology in which a double or sequential hit of both viral and bacterial pathogens leads to a higher risk preterm labour. This study aimed to determine the effect of viral priming on bacterial induced inflammation in human in vitro models of ascending and haematogenous infection.

Methods: Vaginal epithelial cells, and primary amnion epithelial cells and myocytes were used to represent cell targets of ascending infection while interactions between peripheral blood mononuclear cells (PBMCs) and placental explants were used to model systemic infection. To model the effect of viral priming upon the subsequent response to bacterial stimuli, each cell type was stimulated first with a TLR3 viral agonist, and then with either a TLR2 or TLR2/6 agonist, and responses compared to those of each agonist alone. Immunoblotting was used to detect cellular NF-κB, AP-1, and IRF-3 activation. Cellular TLR3, TLR2, and TLR6 mRNA was quantified by RT-qPCR. Immunoassays were used to measure supernatant cytokine, chemokine and PGE2 concentrations.

Results: TLR3 (“viral”) priming prior to TLR2/6 agonist (“bacterial”) exposure augmented the pro-inflammatory, pro-labour response in VECs, AECs, myocytes and PBMCs when compared to the effects of agonists alone. In contrast, enhanced anti-inflammatory cytokine production (IL-10) was observed in placental explants. Culturing placental explants in conditioned media derived from PBMCs primed with a TLR3 agonist enhanced TLR2/6 agonist stimulated production of IL-6 and IL-8, suggesting a differential response by the placenta to systemic inflammation compared to direct infection as a result of haematogenous spread. TLR3 agonism generally caused increased mRNA expression of TLR3 and TLR2 but not TLR6.

Conclusion: This study provides human in vitro evidence that viral infection may increase the susceptibility of women to bacterial-induced sPTB. Improved understanding of interactions between viral and bacterial components of the maternal microbiome and host immune response may offer new therapeutic options, such as antivirals for the prevention of PTB.

Role of galectin-glycan circuits in reproduction: from healthy pregnancy to preterm birth (PTB)

Growing evidence suggests that galectins, an evolutionarily conserved family of glycan-binding proteins, fulfill key roles in pregnancy including blastocyst implantation, maternal-fetal immune tolerance, placental development, and maternal vascular expansion, thereby establishing a healthy environment for the growing fetus. In this review, we comprehensively present the function of galectins in shaping cellular circuits that characterize a healthy pregnancy. We describe the current understanding of galectins in term and preterm labor and discuss how the galectin-glycan circuits contribute to key immunological pathways sustaining maternal tolerance and preventing microbial infections. A deeper understanding of the glycoimmune pathways regulating early events in preterm birth could offer the broader translational potential for the treatment of this devastating syndrome.

TLR3 expression by maternal and fetal cells at the maternal-fetal interface in normal and preeclamptic pregnancies

Inflammation and oxidative stress at the maternal-fetal interface characterize the placental dysfunction that underlies the pregnancy disorder preeclampsia. Specialized fetal trophoblasts directly interact with leukocytes at both sites of the maternal-fetal interface; the uterine wall decidua; and the placenta. TLR3 has been implicated in the harmful inflammation at the maternal-fetal interface in preeclampsia, but the cellular involvement in the decidua and placenta has not been determined. This study aimed to characterize and quantify cell-specific TLR3 expression and function at the maternal-fetal interface in normal and preeclamptic pregnancies. TLR3 expression was assessed by immunohistochemistry and quantified by a novel image-based and cell-specific quantitation method. TLR3 was expressed at the maternal-fetal interface by all decidual and placental trophoblast types and by maternal and fetal leukocytes. Placental, but not decidual, TLR3 expression was significantly higher in preeclampsia compared to normal pregnancies. This increase was attributed to placental intravillous tissue and associated with both moderate and severe placental dysfunction. TLR3 pathway functionality in the decidua and placenta was confirmed by TLR3 ligand-induced cytokine response, but the TLR3 expression levels did not correlate between the two sites. In conclusion, functional TLR3 was broadly expressed by maternal and fetal cells at both sites of the maternal-fetal interface and the placental intravillous expression was increased in preeclampsia. This suggests TLR3-mediated inflammatory involvement with local regulation at both sites of the maternal-fetal interface in normal and preeclamptic pregnancies.

Insight into the expression of toll-like receptors 2 and 4 in patients with abdominal aortic aneurysm

An abdominal aortic aneurysm (AAA) is a relatively common, life-threatening disease prevalent in persons over the age of 65. In recent years, an increasing number of studies have suggested that pattern-recognition receptors (PRRs), including Toll-like receptors (TLRs), may serve as important regulators in the development of AAAs. In this study, we evaluated the TLR2 and TLR4 expression in the aortic wall and blood of patients with AAA. The TLR2 and TLR4 mRNA expression were significantly higher in the blood of patients with AAA than in the blood of healthy volunteers (p = 0.009 and p = 0.010, respectively). The expression of TLR2 and TLR4 transcripts was also higher in the blood compared with the aortic wall tissue of AAA patients (p = 0.001 for both). Higher TLR2 protein expression was observed in the aortic wall of AAA patients compared with the blood (p = 0.026). A significantly higher concentration of TNF-α and IL-4 in patients with AAA than in healthy volunteers (p < 0.001 for both) was noticed. This study suggests that TLR2 may play a role in the inflammatory response in the aorta, both locally and systemically, in patients with AAA.

The role of innate immunity in spontaneous preterm labor: A systematic review

BACKGROUND

Immunoinflammatory response by innate immunity components is a field with increasing interest in understanding the mechanisms behind preterm labor (PTL).

OBJECTIVES

Systematic review of the role of innate immunity in spontaneous PTL.

STUDY DESIGN

PubMed, Scopus, ClinicalTrials.gov and Web of Science were searched using pregnancy AND innate OR toll-like OR natural-killer OR dendritic AND delivery OR premature OR rupture of membranes.

MAIN OUTCOME MEASURES

All article titles and abstracts were evaluated by two individuals, based in strict predefined inclusion criteria. For relevant studies, title, abstract, and full text were assessed to identify PTL and innate immunity studies, excluding multiple pregnancies, cervical insufficiency and indicated PTL.

RESULTS

From 894 articles evaluated, 101 full texts articles were assessed independently. For this systematic review 44 studies were finally included. Toll-like receptors 2 and 4 mediated immune dysfunction and inflammation can result in PTL. Moreover, PTL is linked to high levels of CD14⁺ monocytes; neutrophils seem important in inflammation-associated PTL and in pathological preterm premature rupture of membranes. Besides, decidual natural-killer cells and premature activation of dendritic cells may also participate in the etiology of PTL. Finally, dysregulation of maternal complement might increase the risk of PTL, characterized by high levels of innate lymphoid cells 2 and 3.

CONCLUSIONS

Further research is warranted to ascertain the precise role of innate immunity in PTL. Nonetheless, our results indicate that Toll-like receptors, monocytes, natural-killer cells, dendritic cells and complement have significant roles in PTL.

Delineating differential regulatory signatures of the human transcriptome in the choriodecidua and myometrium at term labor

Preterm deliveries remain the leading cause of neonatal morbidity and mortality. Current therapies target only myometrial contractions and are largely ineffective. As labor involves multiple coordinated events across maternal and fetal tissues, identifying fundamental regulatory pathways of normal term labor is vital to understanding successful parturition and consequently labor pathologies. We aimed to identify transcriptomic signatures of human normal term labor of two tissues: in the fetal-facing choriodecidua and the maternal myometrium. Microarray transcriptomic data from choriodecidua and myometrium following term labor were analyzed for functional hierarchical networks, using Cytoscape 2.8.3. Hierarchically high candidates were analyzed for their regulatory casual relationships using Ingenuity Pathway Analysis. Selected master regulators were then chemically inhibited and effects on downstream targets were assessed using real-time quantitative PCR (RT-qPCR). Unbiased network analysis identified upstream molecular components in choriodecidua including vimentin, TLR4, and TNFSF13B. In the myometrium, candidates included metallothionein 2 (MT2A), TLR2, and RELB. These master regulators had significant differential gene expression during labor, hierarchically high centrality in community cluster networks, interactions amongst the labor gene set, and strong causal relationships with multiple downstream effects. In vitro experiments highlighted MT2A as an effective regulator of labor-associated genes. We have identified unique potential regulators of the term labor transcriptome in uterine tissues using a robust sequence of unbiased mathematical and literature-based in silico analyses. These findings encourage further investigation into the efficacy of predicted master regulators in blocking multiple pathways of labor processes across maternal and fetal tissues, and their potential as therapeutic approaches.

Changes in fetal membrane histology with cervical insufficiency and transabdominal cerclage

OBJECTIVE

To determine whether term fetal membranes from transabdominal cerclage (TAC) patients have favorable characteristics compared with membranes from patients without TAC.

METHODS

A prospective study of consecutive pregnant women who had undergone TAC and were delivered by elective cesarean after 37 weeks before the onset of labor at Cliniques universitaires Saint-Luc, Brussels, between January 2015 and June 2016. Membranes were collected from two areas: overlying the cervix and located far from the cervix. Membrane thickness, 15-hydroxyprostaglandin dehydrogenase (PGDH), toll-like receptor-2 (TLR2) expression, and senescence were measured and compared between the TAC group and a control group without TAC enrolled using the same study criteria.

RESULTS

In the cervical area of the TAC group, the chorion was significantly thicker (P=0.003). PGDH and TLR2 expression were also significantly increased in the cervical area of the TAC group (P=0.021 and P=0.043, respectively). Senescence was significantly decreased in the TAC group (P=0.001).

CONCLUSION

A significant relationship between chorion thickening and increase in PGDH and TLR2 expression and decrease in senescence was reported in the cervical area of membranes in the TAC group. These membrane changes could prevent triggering of parturition and may account for favorable outcomes and clinical success in pregnancies with TAC.

Toll-like receptor 9, maternal cell-free DNA and myometrial cell response to CpG oligodeoxynucleotide stimulation

PROBLEM

Among mechanisms triggering onset of parturition, it has been recently postulated that Toll-Like Receptor (TLR)9 engagement by cell-free DNA (cfDNA) triggers inflammation, myometrial contractions, and labor in absence of infection. The current study evaluated whether direct (myometrial) or indirect (decidual) TLR9 engagement enhances human myometrial contractility.

METHOD OF STUDY

Toll-like receptor 9 expression and cellular localization were surveyed by immunohistochemistry of placenta, fetal membranes, and myometrium in term (gestational age [GA]: >37 weeks) labor (TL, n = 7) or term non-labor (TNL, n = 7) tissues. Non-pregnant myometrium (n = 4) served as reference. TLR9 mRNA expression relative to other TLRs was evaluated through the mining of an RNA-seq dataset and confirmed by RT-PCR. Immortalized human myometrial cells (hTERT-HM) were treated with incremental concentrations of TLR9 agonist ODN2395, TNF-α, or LPS. Secreted cytokines were quantified by multiplex immunoassay, and contractility was assessed by an in-gel cell contraction assay (n = 9). Induction of hTERT-HM contractility was also evaluated indirectly following exposure to conditioned media from primary term decidual cells (n = 4) previously stimulated with ODN2395.

RESULTS

Toll-like receptor 9 immunostaining in placenta and amniochorion was strongest in decidual cells, but unrelated to labor. TLR9 staining intensity was significantly decreased in TL compared with TNL myometrium (P = 0.002). Although total cfDNA in maternal circulation increased in TL (P = 0.025 vs TNL), difference in cffDNA was non-significant. Myometrial TLR9 mRNA levels were unaffected by contractile status and far less abundant than other pro-inflammatory TLRs. hTERT-HM contractility was enhanced by LPS (P = 0.002) and TNF-α (P = 0.003), but not by ODN2395 (P = 0.345) or supernatant of TLR9-stimulated decidual cells.

CONCLUSION

Myometrial and decidual TLR9 are unlikely to directly regulate human parturition.

Peculiarities of the Expression of TLR4 and Inhibitor of TLR-Cascade Tollip in the Placenta in Earlyand Late-Onset Preeclampsia

We studied the peculiarities of the expression of TLR4 and its inhibitor Tollip in placentas obtained from women aged 23-40 years with early- and late-onset preeclampsia. Histological examination of placental tissue (hematoxylin and eosin staining) and immunohistochemical analysis with primary monoclonal antibodies to TLR4 and Tollip were performed on serial paraffin sections. It was found that the expression of TLR4 increased with increasing gestation term in both the syncytiotrophoblast and vascular endothelium of the placental villi (p<0.05). The expression of TLR4 in syncytiotrophoblast and in the endothelium in early preeclampsia was also significantly (p<0.00001) higher than in the reference group (preterm birth before 34 weeks gestation). In the vascular endothelium of placental villi, the expression of TLR4 in placentas from women with early-onset preeclampsia was higher than in late-onset preeclampsia (p=0.002), while Tollip was lower in early-onset preeclampsia than in the reference group. In preeclampsia, especially in early-onset preeclampsia, marked changes in the expression of TLR4 and Tollip in the placental tissue were detected; the severity of preeclampsia correlated with the degree of damage to the placental villi.

Toll-like receptor 4 activation on human amniotic epithelial cells is a risk factor for pregnancy loss

Background:

Maternal–fetal tolerance plays a fundamental role in the maintenance of pregnancy. However, this immunological tolerance can be influenced by intrauterine infections. Human amniotic epithelial cells (hAECs) have immunomodulatory effects and respond to invading pathogens through expressing various toll-like receptors (TLRs). We hypothesize that bacteria or bacterial products affect the immunosuppressive effects of hAECs through TLR stimulation. Here, we investigated how a successful pregnancy can be threatened by TLR4 activation on hAECs on lipopolysaccharide (LPS) engagement.

Materials and Methods:

hAECs were isolated from the amniotic membrane received from six healthy pregnant women. The immunophenotyping of hAECs was studied by flow cytometry. The isolated hAECs (4 × 10⁵ cells/ml) were cultured in 24-well plates in the presence or absence of LPS (5 μg/ml). After 24, 48, and 72 h of incubation, the culture supernatants of hAECs were collected, and the levels of interleukin-5 (IL-5), IL-6, IL-1β, tumor necrosis factor-alpha (TNF-α), transforming growth factor-beta 1 (TGF-β1), and prostaglandin E2 (PGE2) were measured by enzyme-linked immunosorbent assay.

Results:

TLR4 activation showed a stimulatory effect on TGF-β1 production of hAECs (P < 0.001–0.05). PGE2 production of LPS-stimulated hAECs was significantly increased (P < 0.01–0.05). Moreover, TLR4 could induce TNF-α and IL-1β production of hAECs (P < 0.0001–0.01), while this effect was not observed on IL-6 production of hAECs. The IL-5 was produced at a very low level in two culture supernatants of hAECs, in which its production was independent of LPS effect.

Conclusion:

TLR4 activation by bacterial components on hAECs may be a potential risk factor for pregnancy complications.

Analysis of host Toll-like receptor 3 and RIG-I-like receptor gene expression in patients with abdominal aortic aneurysm

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a vascular disease relatively common in the elderly population. Although some events that contribute to the development and progression of AAA are known, there are limited data examining the association of Toll-like receptor 3 (TLR3) and RIG-I-like receptor expression with the pathogenesis of AAAs. In this study, we investigated the gene and protein expression of TLR3 and RIG-I-like receptors (RIG-I and MDA5) in aortic wall and blood of AAA patients and examined the relationship between their expression and immune response.

METHODS

Total RNA was extracted from aortic wall tissues and blood samples collected from 20 patients with AAA and blood samples of 17 healthy volunteers without aortic aneurysm. To evaluate the DDX58 (RIG-I), IFIH1 (MDA5), and TLR3 gene expression level, quantitative real-time polymerase chain reaction was used. Extracellular cytokine and pattern recognition receptor levels were quantified by enzyme-linked immunosorbent assays.

RESULTS

TLR3, RIG-I, and MDA5 were constitutively expressed in both aortic tissues and blood samples from AAA patients and healthy volunteers. In patients with AAA, higher TLR3 expression in aortic tissues than in blood was found (P = .004). The DDX58 messenger RNA expression was higher in blood of patients with AAA compared with healthy subjects (P = .021). A significantly higher level of plasma interleukin 4 was noticed in patients with AAA than in healthy individuals (P = .008).

CONCLUSIONS

This study suggests that RIG-I and TLR3 seem to be important factors in the pathogenesis of AAA.

The effect of lipopolysaccharide on anti-inflammatory and pro-inflammatory cytokines production of human amniotic epithelial cells

Intrauterine infection is a major cause of immune imbalance at the maternal-fetal interface, which leads to spontaneous abortion, premature rupture of the fetal membranes, and preterm birth. Human amniotic epithelial cells (hAECs) play a fundamental role in the maintenance of pregnancy. We hypothesize that bacteria influence the immunomodulatory effects of hAECs through stimulation of Toll-like receptors (TLRs). Here, we investigated how lipopolysaccharide (LPS) as a bacterial component affects anti-inflammatory and pro-inflammatory cytokines production of hAECs. Human placentas were obtained from six healthy pregnant women and hAECs were isolated. The phenotypic characteristics of hAECs were determined by flow cytometry. The hAECs (4 × 10⁵ cells/ml) were cultured in the presence or absence of LPS (5 μg/ml). The viability of the cells was assessed and culture supernatants of hAECs were collected after 24, 48 and 72 h of incubation. The levels of transforming growth factor-beta1 (TGF-β1), interleukin-4 (IL-4), tumor necrosis factor-alpha (TNF-α), interleukin-17 A (IL-17A), and interferon-gamma (IFN-γ) were measured by ELISA. Our data showed that LPS treatment did not affect the viability of hAECs, while had a stimulatory effect on TGF-β1 production of hAECs (p < 0.001). A significant reduction in IL-4 production of LPS-stimulated hAECs was observed (p < 0.05). LPS enhanced the production of TNF-α and IL-17 A of hAECs (p < 0.05-0.0001). The IFN-γ level was only detectable in two culture supernatants of hAECs, and the level was unchanged after stimulation with LPS. Based on these findings, LPS may play a pivotal role in immune imbalance at the feto-maternal interface through affecting anti-inflammatory and pro-inflammatory cytokines production of hAECs.

Regulation of human placental drug transporters in HCV infection and their influence on direct acting antiviral medications

INTRODUCTION

The objectives of this study were to determine how HCV infection affects placental drug transporters, and to determine the role of drug transporters on the cellular accumulation of direct-acting antiviral drugs in human trophoblasts.

METHODS

Eighty-four ABC and SLC transporter genes were first screened in normal and HCV infected pregnant women using PCR profiler array. The changes in expression were confirmed by qPCR and Western blot. The impact of selected drug transporters on the cellular accumulation of radiolabeled antiviral drugs sofosbuvir, entecavir, and tenofovir was measured in primary human trophoblasts (PHT) and BeWo b30 cells in the presence or absence of transporter-specific inhibitors. PHT were then treated with CL097, ssRNA40, and imquimod to determine the impact of Toll-like receptor (TLR) 7/8 activation on drug transporter expression.

RESULTS

The expression of the ABC efflux transporters ABCB1/P-gp and ABCG2/BCRP was increased in placenta of women with HCV, while the nucleoside transporters SLC29A1/ENT1 and SLC29A2/ENT2 remained unchanged. The accumulation of sofosbuvir and tenofovir was unaffected by inhibition of these transporters in trophoblast cells. Entecavir accumulation was decreased by the inhibition of ENT2. P-gp and BCRP inhibition enhanced entecavir accumulation in BeWo b30, but not PHT. Overall, there was little effect of TLR7/8 activation on these drug transporters, and the accumulation of entecavir in PHT.

DISCUSSION

The data suggest that expression of placental drug transporters and selection of antiviral drug may impact fetal drug exposure in pregnancies complicated by HCV infections.

Enhanced expression of IFI16 and RIG-I in human third-trimester placentas following HSV-1 infection

The innate immune response in the placenta depends on the ability of maternal immune cells and fetal trophoblast cells to detect and eliminate invading pathogens through germline-encoded pattern recognition receptors (PRRs). In the present study, we analysed the transcripts and protein expression of interferon (IFN)-inducible protein (IFI)16, melanoma differentiation-associated protein 5 (MDA5), RIG-I-like receptor (RIG-I) and Toll-like receptor (TLR)-3 in third-trimester human placentas and investigated cytokine profiles generated during herpes simplex type 1 (HSV-1) infection. Decidual and chorionic villous biopsies (38-42 weeks of gestation) were obtained from healthy women immediately after a caesarean section. The expression of the DDX58 (RIG-I), IFIH1 (MDA5), IFI16 and TLR3 transcripts was measured using quantitative real-time polymerase chain reaction (qRT-PCR). Extracellular cytokine and PRRs levels were then quantified by enzyme-linked immunosorbent assays (ELISAs). All examined PRRs genes, including DDX58, IFIH1, IFI16 and TLR3, were expressed constitutively at the mRNA and protein levels in the placental biopsies. The concentration of the IFI16 protein was increased in HSV-1-infected decidual and chorionic villous explants compared to those of mock-infected tissues (P = 0·029). Higher protein expression levels of RIG-I in both the maternal and fetal parts of the placenta were found (P = 0·009 and P = 0·004, respectively). In addition, increased production of IFN-β by HSV-1-infected tissues was noticed (P = 0·004 for decidua, P = 0·032 for chorionic villi). No significant differences in the IFN-α, interleukin (IL)-6 and IL-8 levels were found. These results showed that HSV-1 infection can enhance the expression of IFI16 and RIG-I proteins in the human term placenta.

Innate immune responses to toll-like receptor stimulation are altered during the course of pregnancy

During pregnancy the maternal immune system has to develop tolerance towards the developing fetus. These changes in maternal immunity can result in increased severity of certain infections, but also in amelioration of autoimmune diseases. Pregnancy-related hormones have been suggested to play a central role in the adaptation of the maternal immune system, but their specific effects on innate immune function is not well understood. In a longitudinal study of pregnant women, we investigated innate immune cell function in response to toll-like receptors (TLR) 4 and 7 stimulation, two TLR pathways playing a critical role in early innate immune recognition of bacteria and viruses. IFNα production by TLR7-stimulated pDCs was decreased in early pregnancy, and increased towards the end of pregnancy. In contrast, pro-inflammatory TLR4-induced TNFα production by monocytes was increased during early pregnancy, but declined after the first trimester. Changes in cytokine production were associated with changes in pregnancy-related hormones and monocyte subpopulations over the course of pregnancy. These data demonstrating a significant association between pregnancy-related hormones and modulation of innate immune responses mediated by TLRs provide novel insights into the immunological adaptations occurring during pregnancy.

Meta-Analysis of Maternal and Fetal Transcriptomic Data Elucidates the Role of Adaptive and Innate Immunity in Preterm Birth

Preterm birth (PTB) is the leading cause of newborn deaths around the world. Spontaneous preterm birth (sPTB) accounts for two-thirds of all PTBs; however, there remains an unmet need of detecting and preventing sPTB. Although the dysregulation of the immune system has been implicated in various studies, small sizes and irreproducibility of results have limited identification of its role. Here, we present a cross-study meta-analysis to evaluate genome-wide differential gene expression signals in sPTB. A comprehensive search of the NIH genomic database for studies related to sPTB with maternal whole blood samples resulted in data from three separate studies consisting of 339 samples. After aggregating and normalizing these transcriptomic datasets and performing a meta-analysis, we identified 210 genes that were differentially expressed in sPTB relative to term birth. These genes were enriched in immune-related pathways, showing upregulation of innate immunity and downregulation of adaptive immunity in women who delivered preterm. An additional analysis found several of these differentially expressed at mid-gestation, suggesting their potential to be clinically relevant biomarkers. Furthermore, a complementary analysis identified 473 genes differentially expressed in preterm cord blood samples. However, these genes demonstrated downregulation of the innate immune system, a stark contrast to findings using maternal blood samples. These immune-related findings were further confirmed by cell deconvolution as well as upstream transcription and cytokine regulation analyses. Overall, this study identified a strong immune signature related to sPTB as well as several potential biomarkers that could be translated to clinical use.

Lipopolysaccharide and cAMP modify placental calcitriol biosynthesis reducing antimicrobial peptides gene expression

PROBLEM

Calcitriol, the hormonal form of vitamin D₃ (VD), stimulates placental antimicrobial peptides expression; nonetheless, the regulation of calcitriol biosynthesis in the presence of bacterial products and its consequence on placental innate immunity have scarcely been addressed.

METHOD OF STUDY

We investigated how some bacterial products modify placental VD metabolism and its ability to induce antimicrobial peptides gene expression.

RESULTS

Cultured human trophoblasts biosynthesized calcitriol only in the presence of its precursor calcidiol, a process that was inhibited by cyclic-AMP but stimulated by lipopolysaccharide (LPS). Intracrine calcitriol upregulated cathelicidin, S100A9, and β-defensins (HBDs) gene expression, while LPS further stimulated HBD2 and S100A9. Unexpectedly, LPS significantly repressed cathelicidin basal mRNA levels and drastically diminished calcidiol ability to induce it. Meanwhile, cyclic-AMP, which is used by many microbes to avoid host defenses, suppressed calcitriol biosynthesis, resulting in significant inhibition of most VD-dependent microbicidal peptides gene expression.

CONCLUSION

While LPS stimulated calcitriol biosynthesis, cyclic-AMP inhibited it. LPS downregulated cathelicidin mRNA expression, whereas cyclic-AMP antagonized VD-dependent-upregulation of most antimicrobial peptides. These findings reveal LPS and cyclic-AMP involvement in dampening placental innate immunity, highlighting the importance of cyclic-AMP in the context of placental infection and suggesting its participation to facilitate bacterial survival.

The expression of Toll-like receptor 5 in preterm histologic chorioamnionitis

Spontaneous preterm birth is often caused by chorioamnionitis. Toll-like receptors (TLRs) have a role in the response of the innate immune system. The role of TLR5 in chorioamnionitis remains unclear: however, TLR5 was reported to have a significantly stronger effect on the induction of interleukin (IL)-6 when compared with other TLRs in amniotic epithelial cells. The aim of this study was to investigate TLR5 expression in placentas with preterm histologic chorioamnionitis (HCA). The expression levels of TLR5 were evaluated in the amnions, chorions, deciduae and villi with and without HCA using immunohistochemistry. The co-localization of IL-6 or IL-8 with TLR5 was examined by immunofluorescence. The production of IL-6 was examined in primary tissue cultured fetal membranes treated with and without the TLR5 agonist. The protein expression of TLR5 was significantly increased in amnions with HCA (p<0.05) and showed a trend toward an increase in chorions with HCA, whereas no significant difference was detected in the villi and decidua. TLR5 co-localized with IL-6 and IL-8 in amnions and chorions. IL-6 showed a significant increase (p<0.05) with the TLR5 agonist. These results suggest that TLR5 plays a role in the pathogenesis of preterm HCA and IL-6 production.

Glibenclamide inhibits NLRP3 inflammasome-mediated IL-1β secretion in human trophoblasts

Infection-associated pregnancy complications cause premature delivery. Caspase-1 is involved in the maturation of interleukin (IL)-1β, which is activated by the NLRP3 inflammasome. To characterize the significance of the NLRP3 inflammasome pathway in the placenta, the effects of activators and inhibitors on NLRP3-related molecules were examined using isolated primary trophoblasts. Caspase-1 and IL-1β mRNA expression was markedly increased in response to lipopolysaccharide (LPS), a toll-like receptor (TLR)4 ligand. Treatment with the potassium ionophore nigericin significantly increased the level of activated caspase-1. Treatment with either LPS or nigericin stimulated IL-1β secretion, whereas pretreatment with the ATP-sensitive K⁺ channel inhibitor glibenclamide, the Rho-associated coiled-coil kinase inhibitor Y-27632, or a caspase-1 inhibitor significantly decreased nigericin-induced IL-1β secretion. In addition, dibutyryl-cAMP, which induces trophoblast differentiation, decreased expression of NLRP3, caspase-1, and IL-1β. These findings suggest that trophoblasts can secrete IL-1β through the NLRP3/caspase-1 pathway, which is suppressed by glibenclamide, and that the TLR4-mediated NLRP3 inflammasome pathway is more likely to be stimulated in undifferentiated than differentiated trophoblasts. Our data support the hypothesis that inhibition of the NLRP3 inflammasome can suppress placental inflammation-associated disorders.

Role of Innate Immunity in Preeclampsia: A Systematic Review

Innate immune system dysfunction has been known to be a key player in preeclampsia (PE). Activation of the maternal innate immunity may be triggered by invading microorganisms or endogenous ligands, which are detected by different pattern recognition receptors (PRRs). Although some studies have linked PRR activation to PE, it is still unclear if dysregulated PRR expression is associated with the development of this complication. Therefore, we conducted a systematic review of the literature, searching articles that evaluated associations of PRRs with PE. Twenty-six studies met the inclusion criteria: 20 of them analyzed PRR expressions and 6 studies investigated the association between PRR polymorphisms and PE. Among the PRRs, only few studies analyzed retinoic acid-inducible gene I-like helicase (RLH) and/or toll-like receptor (TLR)-1, 5, 6, 7, 8, and 9 expressions in immune cells or placentas from women with PE and controls; thus, it is inconclusive if these PRRs are involved in PE. Results from the 10 studies that analyzed TLR-2 expressions in women with PE and controls are also contradictory. The majority of the studies that investigated TLR-3 and -4 expressions indicate that these PRRs are increased in placenta or immune cells from women with PE compared to pregnant control woman. To date, polymorphisms in TLR-2, - 3, and - 4 and nucleotide-binding oligomerization domain-like receptor 2 genes do not seem to be associated with PE development. No study has evaluated the association between polymorphisms in genes codifying other TLRs or RLHs genes. In conclusion, available data in literature support a role for TLR-3 and TLR-4 in the pathogenesis of PE.

TLR2, TLR3 and TLR5 regulation of pro-inflammatory and pro-labour mediators in human primary myometrial cells

Preterm birth continues to be a significant global health care issue, due to our lack of understanding of the mechanisms that drive human labour and delivery. Toll-like receptors (TLRs) are essential in triggering an inflammatory response in human gestational tissues, leading to the production of pro-inflammatory and pro-labour mediators, and thus preterm birth. The aims of this study were to determine whether the adaptor molecules associated with TLR2, TLR3 and TLR5 signalling are involved in human myometrium. Primary human myometrial cells were transfected with siRNA against TIRAP, IRAK1, IRAK4, TAK1and stimulated with bacterial product fsl-1 (TLR2); TRIF, TRADD, TRAF6, RIP1, TAK1 and stimulated with dsRNA viral analogue poly(I:C) (TLR3); IRAK1, IRAK4, TAK1 and stimulated with bacterial product flagellin (TLR5), and assayed for production of pro-inflammatory and pro-labour mediators. Cells transfected with TIRAP, IRAK1, IRAK4 or TAK1 all showed a decrease in fsl-1-induced expression of cytokines (IL-1α, IL-1β, IL-6), chemokines (GRO-α, IL-8, MCP-1), adhesion molecule ICAM-1, cyclooxygenase (COX)-2 mRNA and release of PGF_2α and MMP-9 expression. Cells transfected with TRIF, TRAF6, RIP1 or TAK1 all decreased production of poly(I:C)-induced IL-1α, IL-1β, IL-6, GRO-α, IL-8, MCP-1, ICAM-1 and MMP-9 expression. Cells transfected with IRAK1, IRAK4 or TAK1 all showed decreased expression of flagellin-induced cytokine and chemokine expression, ICAM-1 and MMP-9 expression. Lastly, transfection with these siRNAs decreased fsl-1, poly(I:C) and flagellin-induced NF-κB transcriptional activity. Our study signifies that these adaptor molecules are necessary for the proper production of cytokines, chemokines and pro-labour mediators after TLR ligation.

Expression and function of NOD-like receptors by human term gestation-associated tissues

INTRODUCTION

Nucleotide-binding oligomerization domain (NOD)-like receptors or NOD-like receptors (NLRs) have been implicated in several disease pathologies associated with inflammation. Since local and systemic inflammation is a hallmark of both term and preterm labour, a role for NLRs at the materno-fetal interface has been postulated.

METHODS

Gene expression and immunolocalisation of NLR family members in human placenta, choriodecidua, and amnion were examined. Tissue explants were used to examine the response to activators of NOD1 (Tri-DAP), NOD2 (MDP) and NLRP3 (nigericin). Cell/tissue-free supernatants were examined for the production of interleukin (IL)-1β, IL-6, IL-8 and IL-10 using specific ELISAs.

RESULTS

Expression of transcripts for NOD1, NOD2, NLRP3, NLRC4, NLRX1, NLRP1 and NAIP and protein expression of NOD1, NOD2 and NLRP3 were a broad feature of all term gestation-associated tissues. Production of cytokines was increased significantly in response to all ligands in placenta and choriodecidua, except for MDP-induced IL-10. Similarly, there was a significant in the amnion except for MDP induced IL-1β and IL-10 response to either agonist. IL-1β production was dependent on caspase-1 regardless of agonist used or tissue examined.

DISCUSSION

Term human gestation-associated tissues express functional NLRs which likely play a role in both sterile and pathogen-driven inflammatory responses at the materno-fetal interface.

Human gestation-associated tissues express functional cytosolic nucleic acid sensing pattern recognition receptors

The role of viral infections in adverse pregnancy outcomes has gained interest in recent years. Innate immune pattern recognition receptors (PRRs) and their signalling pathways, that yield a cytokine output in response to pathogenic stimuli, have been postulated to link infection at the maternal-fetal interface and adverse pregnancy outcomes. The objective of this study was to investigate the expression and functional response of nucleic acid ligand responsive Toll-like receptors (TLR-3, -7, -8 and -9), and retinoic acid-inducible gene 1 (RIG-I)-like receptors [RIG-I, melanoma differentiation-associated protein 5 (MDA5) and Laboratory of Genetics and Physiology 2(LGP2)] in human term gestation-associated tissues (placenta, choriodecidua and amnion) using an explant model. Immunohistochemistry revealed that these PRRs were expressed by the term placenta, choriodecidua and amnion. A statistically significant increase in interleukin (IL)-6 and/or IL-8 production in response to specific agonists for TLR-3 (Poly(I:C); low and high molecular weight), TLR-7 (imiquimod), TLR-8 (ssRNA40) and RIG-I/MDA5 (Poly(I:C)LyoVec) was observed; there was no response to a TLR-9 (ODN21798) agonist. A hierarchical clustering approach was used to compare the response of each tissue type to the ligands studied and revealed that the placenta and choriodecidua generate a more similar IL-8 response, while the choriodecidua and amnion generate a more similar IL-6 response to nucleic acid ligands. These findings demonstrate that responsiveness via TLR-3, TLR-7, TLR-8 and RIG-1/MDA5 is a broad feature of human term gestation-associated tissues with differential responses by tissue that might underpin adverse obstetric outcomes.

Microbial Vertical Transmission during Human Pregnancy

Congenital infections with pathogens such as Zika virus, Toxoplasma gondii, Listeria monocytogenes, Treponema pallidium, parvovirus, HIV, varicella zoster virus, Rubella, Cytomegalovirus, and Herpesviruses are a major cause of morbidity and mortality worldwide. Despite the devastating impact of microbial infections on the developing fetus, relatively little is known about how pathogens associated with congenital disease breach the placental barrier to transit vertically during human pregnancy. In this Review, we focus on transplacental transmission of pathogens during human gestation. We introduce the structure of the human placenta and describe the innate mechanisms by which the placenta restricts microbial access to the intrauterine compartment. Based on current knowledge, we also discuss the potential pathways employed by microorganisms to overcome the placental barrier and prospects for the future.

A critical assessment of the "sterile womb" and "in utero colonization" hypotheses: implications for research on the pioneer infant microbiome

After more than a century of active research, the notion that the human fetal environment is sterile and that the neonate's microbiome is acquired during and after birth was an accepted dogma. However, recent studies using molecular techniques suggest bacterial communities in the placenta, amniotic fluid, and meconium from healthy pregnancies. These findings have led many scientists to challenge the "sterile womb paradigm" and propose that microbiome acquisition instead begins in utero, an idea that would fundamentally change our understanding of gut microbiota acquisition and its role in human development. In this review, we provide a critical assessment of the evidence supporting these two opposing hypotheses, specifically as it relates to (i) anatomical, immunological, and physiological characteristics of the placenta and fetus; (ii) the research methods currently used to study microbial populations in the intrauterine environment; (iii) the fecal microbiome during the first days of life; and (iv) the generation of axenic animals and humans. Based on this analysis, we argue that the evidence in support of the "in utero colonization hypothesis" is extremely weak as it is founded almost entirely on studies that (i) used molecular approaches with an insufficient detection limit to study "low-biomass" microbial populations, (ii) lacked appropriate controls for contamination, and (iii) failed to provide evidence of bacterial viability. Most importantly, the ability to reliably derive axenic animals via cesarean sections strongly supports sterility of the fetal environment in mammals. We conclude that current scientific evidence does not support the existence of microbiomes within the healthy fetal milieu, which has implications for the development of clinical practices that prevent microbiome perturbations after birth and the establishment of future research priorities.

Interleukin 4 and interleukin 13 downregulate the lipopolysaccharide-mediated inflammatory response by human gestation-associated tissues

Inflammation is a key feature of preterm and term labor. Proinflammatory mediators are produced by gestation-associated tissues in response to pathogen-associated molecular patterns and damage-associated molecular patterns. Interleukin (IL)4, IL10, and IL13 are anti-inflammatory cytokines with potential as anti-inflammatory therapies to prevent preterm birth. The objective of this study was to determine if IL4 and IL13 exert anti-inflammatory effects on lipopolysaccharide (LPS)-stimulated production of proinflammatory cytokines produced by human term gestation-associated tissues (placenta, choriodecidua, and amnion). Both IL4 and IL13 reduced LPS-stimulated IL1B and macrophage inflammatory protein1A; this effect diminished with delay to exposure to either cytokine. There was no effect on LPS-stimulated prostaglandin production. Interleukin 4 receptor alpha (IL4RA) was expressed throughout the placenta, choriodecidua, and amnion, and the inhibitory effects of IL4 and IL13 were IL4RA dependent. Combined IL4 and IL13 did not enhance the anti-inflammatory potential of either cytokine; however, a combination of IL4 and IL10 had a greater anti-inflammatory effect than either cytokine alone. These findings demonstrate that human term gestation-associated tissues are responsive to the anti-inflammatory cytokines IL4 and IL13, which could downregulate LPS-induced cytokine production in these tissues. Anti-inflammatory cytokines might offer an adjunct to existing therapeutics to prevent adverse obstetric outcome.

Differential expression of toll-like receptors in the human placenta across early gestation

Toll-like receptors (TLRs) are an essential component of the innate immune system. While a number of studies have described TLR expression in the female reproductive tract, few have examined the temporal expression of TLRs within the human placenta. We hypothesized that the pattern of TLR expression in the placenta changes throughout the first and second trimester, coincident with physiological changes in placental function and the demands of innate immunity. We collected first and second trimester placental tissue and conducted quantitative PCR analysis for TLRs 1-10, followed by immunohistochemistry to define the cell specific expression pattern of a subset of these receptors. Except for the very earliest time points, RNA expression for TLRs 1-10 was stable out to 20 weeks gestation. However, the pattern of protein expression evolved over time. Early first trimester placenta demonstrated a strong, uniform pattern predominantly in the inner villous cytotrophoblast layer. As the placenta matured through the second trimester, both the villous cytotrophoblasts and the pattern of TLR expression within them became disorganized and patchy, with putative Hofbauer cells now identifiable in the tissue also staining positive. We conclude from this data that placental TLR expression changes over the course of gestation, with a tight barrier of TLRs forming a wall of defense along the cytotrophoblast layer in the early first trimester that breaks down as pregnancy progresses. These data are relevant to understanding placental immunity against pathogen exposure throughout pregnancy and may aid in our understanding of the vulnerable period for fetal exposure to pathogens.

Positive Correlation between Enhanced Expression of TLR4/MyD88/NF-κB with Insulin Resistance in Placentae of Gestational Diabetes Mellitus

Insulin resistance (IR) is a critical factor of the pathophysiology of Gestational diabetes mellitus (GDM). Studies on key organs involved in IR, such as livers and adipose tissues, showed that Toll-like receptor 4 (TLR4) can regulate insulin sensitivity. As a maternal-fetal interface with multi-functions, placentae could contribute to the development of IR for GDM. Thus, we investigated the expressions of TLR4/Myeloid Differentiation factor 88 (MyD88)/Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-kB) in term placentae from 33 GDM women and 36 healthy pregnant women with normal glucose tolerance, evaluated local and systemic IR and furthermore identified the association between placental TLR4 and IR. TLR4 protein was expressed in various cells of term placenta, particularly in syncytiotrophoblast of villi. Compared with normal pregnancy, the expression of TLR4/MyD88/NF-kB pathway increased in the placenta of GDM (p<0.05), and these differences were more pronounced in the maternal section of the placenta and the syncytiotrophoblast of villi. In addition, more severe IR was observed in the placenta of GDM patients than the control group, evidenced with higher pIRS-1(ser312) (p<0.001) and lower IRS-1 (p<0.05) as well as pAkt proteins (p<0.01). The expression of TLR4 in placentae is positively correlated with local IR (pIRS-1: r = 0.76, p <0.001 and pAkt: r = -0.47, p <0.001) and maternal fasting (r = 0.42, p <0.01), one-hour (r = 0.52, p <0.01) and two-hour glucose (r = 0.54, p <0.01) at OGTT. We found an that enhanced expression of the TLR4-MyD88-NF-kB pathway occurs in GDM placentae, which positively correlates with heightened local IR in placentae and higher maternal hyperglycemia. The TLR4/MyD88/NF-kB pathway may play a potential role in the development of IR in placentae of GDM.

Exposure to stimulatory CpG oligonucleotides during gestation induces maternal hypertension and excess vasoconstriction in pregnant rats

Bacterial infections increase risk for pregnancy complications, such as preeclampsia and preterm birth. Unmethylated CpG DNA sequences are present in bacterial DNA and have immunostimulatory effects. Maternal exposure to CpG DNA induces fetal demise and craniofacial malformations; however, the effects of CpG DNA on maternal cardiovascular health have not been examined. We tested the hypothesis that exposure to synthetic CpG oligonucleotides (ODNs) during gestation would increase blood pressure and cause vascular dysfunction in pregnant rats. Pregnant and nonpregnant female rats were treated with CpG ODN (ODN 2395) or saline (Veh) starting on gestational day 14or corresponding day for the nonpregnant groups. Exposure to CpG ODN increased systolic blood pressure in pregnant (Veh: 121 ± 2 mmHg vs. ODN 2395: 134 ± 2 mmHg,P< 0.05) but not in nonpregnant rats (Veh: 111 ± 2 mmHg vs. ODN 2395: 108 ± 5 mmHg,P> 0.05). Mesenteric resistance arteries from pregnant CpG ODN-treated rats had increased contractile responses to U46619 [thromboxane A2(TxA2) mimetic] compared with arteries from vehicle-treated rats [Emax(%KCl), Veh: 87 ± 4 vs. ODN 2395: 104 ± 4,P< 0.05]. Nitric oxide synthase (NOS) inhibition increased contractile responses to U46619, and CpG ODN treatment abolished this effect in arteries from pregnant ODN 2395-treated rats. CpG ODN potentiated the involvement of cyclooxygenase (COX) to U46619-induced contractions. In conclusion, exposure to CpG ODN during gestation induces maternal hypertension, augments resistance artery contraction, increases the involvement of COX-dependent mechanisms and reduces the contribution of NOS-dependent mechanisms to TxA2-induced contractions in mesenteric resistance arteries.

Inflammation and preterm birth

Preterm birth is the leading cause of neonatal morbidity and mortality. Although the underlying causes of pregnancy-associated complication are numerous, it is well established that infection and inflammation represent a highly significant risk factor in preterm birth. However, despite the clinical and public health significance, infectious agents, molecular trigger(s), and immune pathways underlying the pathogenesis of preterm birth remain underdefined and represent a major gap in knowledge. Here, we provide an overview of recent clinical and animal model data focused on the interplay between infection-driven inflammation and induction of preterm birth. Furthermore, here, we highlight the critical gaps in knowledge that warrant future investigations into the interplay between immune responses and induction of preterm birth.

Excessive TLR9 signaling contributes to the pathogenesis of spontaneous abortion through impairment of Treg cell survival by activation of Caspase 8/3

BACKGROUND

The pregnant uterine microenvironment is repleted with Toll-like receptors (TLRs), however, their roles of these receptors in establishing tolerance to growing fetus are largely unknown.

RESULT

Decidual TLR1, TLR3, TLR4, TLR8 and TLR9 gene expressions were significantly over-expressed in patients of spontaneous abortion compared with elective abortion with normal pregnancy. In particular, the expression of TLR4 and TLR9 mRNA was considerably higher than that of remaining TLRs. We mimic TLR9 signal with combination of its pathogenic ligand CpG ODN and antagonists ODN in a well-established abortion-prone CBA/J×DBA/2 model. CpG ODN dramatically boosted fetal loss and lowered the proportion of Regulatory cells (Treg cells) in vivo. CpG ODN directly triggered the impaired survival and increased activity of Caspase 8/3 of Treg cells in vitro. These effects were blocked by antagonist ODN.

CONCLUSION

Excessive TLR9 signaling contributed to maternal-fetal tolerance disruption via an effect on Treg cell survival by activation of Caspase 8/3.

In vitro progesterone modulation on bacterial endotoxin-induced production of IL-1β, TNFα, IL-6, IL-8, IL-10, MIP-1α, and MMP-9 in pre-labor human term placenta

BACKGROUND

During human pregnancy, infection/inflammation represents an important factor that increases the risk of developing preterm labor. The purpose of this study was to determine if pre-treatment with progesterone has an immunomodulatory effect on human placenta production of endotoxin-induced inflammation and degradation of extracellular matrix markers.

METHODS

Placentas were obtained under sterile conditions from pregnancies delivered at term before the onset of labor by cesarean section. Explants from central cotyledons of 10 human placentas were pre-treated with different concentrations of progesterone (0.01, 01, 1.0 μM) and then stimulated with 1000 ng/mL of LPS of Escherichia coli. Cytokines TNFα, IL-1β, IL-6, IL-8, MIP-1α, IL-10 concentrations in the culture medium were then measured by specific ELISA. Secretion profile of MMP-9 was evaluated by ELISA and zymogram. Statistical differences were determined by one-way ANOVA followed by the appropriate ad hoc test; P < 0.05 was considered statistically significant.

RESULTS

In comparison to the explants incubated with vehicle, the LPS treatment led to a significant increase in the level of all cytokines. In comparison to the explants treated only with LPS, pre-treatment with 0.01-1.0 μM progesterone significantly blunted (73, 56, 56, 75, 25, 48 %) the secretion of TNF-α, IL-1β, IL-6, IL-8, MIP-1α, IL-10, respectively. The MMP-9 induced by LPS treatment was inhibited only with the highest concentration of progesterone. Mifepristone (RU486) blocked the immunosuppressive effect of progesterone.

CONCLUSIONS

The present results support the concept that progesterone could be part of the compensatory mechanism that limits the inflammation-induced cytotoxic effects associated with an infection process during gestation.

Novel Noncompetitive IL-1 Receptor-Biased Ligand Prevents Infection- and Inflammation-Induced Preterm Birth

Preterm birth (PTB) is firmly linked to inflammation regardless of the presence of infection. Proinflammatory cytokines, including IL-1β, are produced in gestational tissues and can locally upregulate uterine activation proteins. Premature activation of the uterus by inflammation may lead to PTB, and IL-1 has been identified as a key inducer of this condition. However, all currently available IL-1 inhibitors are large molecules that exhibit competitive antagonism properties by inhibiting all IL-1R signaling, including transcription factor NF-κB, which conveys important physiological roles. We hereby demonstrate the efficacy of a small noncompetitive (all-d peptide) IL-1R-biased ligand, termed rytvela (labeled 101.10) in delaying IL-1β-, TLR2-, and TLR4-induced PTB in mice. The 101.10 acts without significant inhibition of NF-κB, and instead selectively inhibits IL-1R downstream stress-associated protein kinases/transcription factor c-jun and Rho GTPase/Rho-associated coiled-coil-containing protein kinase signaling pathways. The 101.10 is effective at decreasing proinflammatory and/or prolabor genes in myometrium tissue and circulating leukocytes in all PTB models independently of NF-κB, undermining NF-κB role in preterm labor. In this work, biased signaling modulation of IL-1R by 101.10 uncovers a novel strategy to prevent PTB without inhibiting NF-κB.

Functional activity but not gene expression of toll-like receptors is decreased in the preterm versus term human placenta

INTRODUCTION

Toll-like receptor (TLR) activity within gestation-associated tissues might have a role in normal pregnancy progression as well as adverse obstetric outcomes such as preterm birth (PTB).

METHODS

The expression and activity of TLRs 1-9 in placentas collected following preterm vaginal delivery after infection-associated preterm labour (IA-PTL) at 25-36 weeks of gestation (preterm-svd, n = 10) were compared with those obtained after normal vaginal delivery at term (term-laboured; n = 17). Placental explants were cultured in the presence of agonists for TLR2, 3, 4, 5, 7, 8 and 9 and cytokine production after 24 h examined. Expression of TLR transcripts was determined using real time quantitative PCR.

RESULTS

Reactivity to all agonists except CpG oligonucleotides was observed indicating that other than TLR9 all of the receptors studied yielded functional responses both term and preterm. Significantly less TNFα and IL-6, but not IL-10, were produced by preterm than term samples in response to all TLR agonists. Changes in TLR mRNA expression did not underlie functional differences in the preterm and term groups; nor does a pre-exposure/tolerance model mimic this finding. While glucocorticoids suppressed cytokine production in an in vitro model using term tissue the association between lower gestational age and decreased cytokine outputs suggests a temporally regulated response.

DISCUSSION

Pro-inflammatory cytokine output in response to multiple TLR ligands was decreased in the preterm compared to the term placenta but gene expression for each TLR tended to be similar. Reduced cytokine production by the preterm placenta in response to stimulation of TLRs therefore must be regulated at the post-transcriptional level in a gestational age dependent manner.

Impact of bacterial and viral challenge on multidrug resistance in first- and third-trimester human placenta

The ABC transporters P-glycoprotein (P-gp, official gene symbol ABCB1) and breast cancer resistance protein (BCRP, official gene symbol ABCG2) protect the conceptus from exposure to toxins and xenobiotics present in the maternal circulation. Viral or bacterial challenges alter expression of placental multidrug transporters in rodents. We hypothesized that exposure to lipopolysaccharide (LPS, bacterial antigen) and polyinosinic-polycytidylic acid (poly(I:C), viral antigen) would decrease P-gp and BCRP in the human placenta. Placental explants from first and third trimesters were challenged with 0.1 to 10 μg/mL LPS or 1 to 50 μg/mL poly(I:C) for 4 or 24 hours; mRNA levels, protein expression, and localization were assessed by quantitative real-time PCR, Western blot analysis, and immunohistochemistry, respectively. Toll-like receptor (TLR)-3 and TLR-4 mRNA expression increased from the first to third trimester (P < 0.01), and the receptors localized to cytotrophoblasts in the first trimester and to syncytiotrophoblasts in the third trimester. LPS exposure in first-trimester explants decreased (P < 0.001) ABCB1 and ABCG2 mRNA and protein levels. In contrast, poly(I:C) decreased (P < 0.05) ABCB1, TLR-3, and TLR-4 mRNA levels in the third trimester but not first trimester. LPS and poly(I:C) treatments increased (P < 0.01) IL-8 and chemokine ligand 2. Results suggest that bacterial infections likely alter exposure of the conceptus to toxins and drugs during early pregnancy, whereas viral infections may disrupt fetal protection in later stages of pregnancy.