Murine abortion is associated with enhanced interleukin-6 levels at the feto-maternal interface

Absence of Heme Oxygenase-1 Affects Trophoblastic Spheroid Implantation and Provokes Dysregulation of Stress and Angiogenesis Gene Expression in the Uterus

The enzyme heme oxygenase-1 (HO-1) is pivotal in reproductive processes, particularly in placental and vascular development. This study investigated the role of HO-1 and its byproduct, carbon monoxide (CO), in trophoblastic spheroid implantation. In order to deepen our understanding of the role of HO-1 during implantation, we conducted in vivo experiments on virgin and pregnant mice, aiming to unravel the cellular and molecular mechanisms. Using siRNA, HO-1 was knocked down in JEG-3 and BeWo cells and trophoblastic spheroids were generated with or without CO treatment. Adhesion assays were performed after transferring the spheroids to RL-95 endometrial epithelial cell layers. Additionally, angiogenesis, stress, and toxicity RT2-Profiler™ PCR SuperArray and PCR analyses were performed in uterine murine samples. HO-1 knockdown by siRNA impeded implantation in the 3D culture model, but this effect could be reversed by CO. Uteruses from virgin Hmox1-/- females exhibited altered expression of angiogenesis and stress markers. Furthermore, there was a distinct expression pattern of cytokines and chemokines in uteruses from gestation day 14 in Hmox1-/- females compared to Hmox1+/+ females. This study strongly supports the essential role of HO-1 during implantation. Moreover, CO appears to have the potential to compensate for the lack of HO-1 during the spheroid attachment process. The absence of HO-1 results in dysregulation of angiogenesis and stress-related genes in the uterus, possibly contributing to implantation failure.

Clinical, oral immunological and microbiological shifts during and after pregnancy

OBJECTIVES

Physiological changes and shifts in the oral microbiota composition during pregnancy may affect the maternal immune system. Uncomplicated pregnancy is associated with a T-helper (Th) 2 predominant cytokine regulation (anti-inflammatory), while oral health deterioration during pregnancy is reflected by severe gingival inflammation, a primarily Th1 cytokine phenotype (pro-inflammatory), and oral microbiome alterations. This prospective observational study aimed to evaluate Th cytokine shifts and changes in the oral microbiota composition in saliva of women before and after birth.

MATERIAL AND METHODS

Saliva (n = 96) was collected before and 6 months after birth, and medical, oral health, and periodontal status were assessed. In a multiplex immunoassay, 10 cytokines were simultaneously analyzed and cumulative Th1 and Th2 cytokine levels and Th1/Th2 ratio were calculated for all groups. Putative periodontal pathogens (n = 6) were evaluated by quantitative real-time polymerase chain reaction.

RESULTS

Th2 cytokine levels were significantly lower (p = 0.014) while pro-inflammatory cytokine levels were significantly higher (p < 0.01) during pregnancy than postpartum. Similar Th1 levels were found between the groups (p = 0.143). Th1 and Th2 cytokines positively correlated with periodontal parameters (p < 0.001) and levels of studied bacteria during pregnancy (p < 0.05).

CONCLUSIONS

This study identified a significantly increased Th1/Th2 cytokine ratio during pregnancy and a positive association with putative periodontal pathogens. This immunological and microbiological deregulation in the oral milieu during pregnancy is suggestive of a destructive inflammatory periodontal profile.

STUDY REGISTRATION

Clinical Trials.gov (Record BAP-2015).

CLINICAL RELEVANCE

Understanding altered oral immunological and microbiological regulation patterns during pregnancy may help improve the inflammatory periodontal profile in pregnant women.

Diminished miR-374c-5p negatively regulates IL (interleukin)-6 in unexplained recurrent spontaneous abortion

Unexplained recurrent spontaneous abortion (URSA) is commonly observed, and seriously affects women's reproductive health. Excessive interleukin-6 (IL-6) production has been shown to frequently occur and relate to URSA pathogenesis. In this study, the miRNA expression profile in peripheral blood mononuclear cells (PBMCs) from URSA patients and normal pregnant (NP) women was assessed by miRNA microarray and real-time quantitative reverse-transcription polymerase chain reaction (qPCR). MiRNA target prediction tools and luciferase reporter assay were used to detect direct binding between miRNAs and IL6. Functional study of administering anti-IL-6 neutralizing antibody and miR-374c-5p mimics to an URSA animal model was performed to evaluate embryo resorption rates. In the results, compared with NP women, the expression of IL-6 increased markedly in PBMCs and decidual tissues at both mRNA and protein levels, while miR-374c-5p expression decreased significantly. Prediction software and luciferase reporter assay showed that miR-374c-5p binds with IL6 3'UTR via the complementary bases. Transfection of miR-374c-5p mimics into an in vitro HeLa cell line significantly downregulated the expression of IL-6, while transfection of the miR-374c-5p inhibitor induced an opposite result. In the URSA mouse model, miR-374c-5p overexpression reduced the embryo resorption rate significantly, accompanied with decreased expression of IL-6 in the decidua. To sum up, downregulated miR-374c-5p was involved in the pathogenesis of URSA by enhancing IL-6 expression. Modulation of miR-374c-5p expression may be used to regulate IL-6 production for the treatment of URSA.

Histopathological examination of the placenta after delivery in pregnant women with COVID-19

Introduction: COVID-19 is a viral disease generated by a new coronavirus named SARS-CoV-2. The consequences of this virus on the human placenta and the newborn are still unclear. IL-6 can disturb the placenta's immunological homeostasis and be employed as an inflammatory marker for the poor prognosis of COVID-19 infection. Bax has some features like being a key protein regulating apoptotic mechanisms and plays an important role in both maintaining dynamic balance and integrity in the placenta as in many tissues. This study aims to indicate the impact of COVID-19 on inflammation and apoptotic pathways in the placenta by using IL-6 and Bax antibodies. Material and Method: COVID-19 positive (n:10) and COVID-19 negative (n:10) normotensive placentas were included. Haematoxylin-eosin staining and immunohistochemical staining (IL-6 and Bax antibodies) were applied. Statistical data of immunohistochemical (IL-6 and Bax expression) staining results were assessed by analyzing the H-score. Biochemical parameters were recorded. Group means were analyzed with a nonparametric Kruskal Wallis Test. Results: In the COVID-19 group, increased syncytial knots, fibrin deposition, inflammation, fibrinoid necrosis, neutrophil accumulation were observed. The COVID-19 group had considerably higher levels of IL-6 and Bax expression than the control group. Furthermore, COVID-19 patients had statistically lower WBC and higher CRP values than normotensive patients. Conclusion: COVID-19 has been linked to placental inflammation and trophoblast cell damage, both of which can result in major maternal and fetal problems during pregnancy. We found intense IL-6 expression in the placentas of pregnant women with COVID-19 infection. A rise in IL-6 levels triggers CRP production, and this increase is linked to the severity of COVID-19 as a risk factor. Also, we suggested that COVID-19 infection triggers the apoptotic process in placental tissue by increasing the expression of the proapoptotic Bax protein. It is clinically very significant to follow up COVID-19 positive pregnancies for maternal and fetal health. During this follow-up, IL-6 and Bax expression levels in the placenta, together with histopathological findings and serum CRP levels, can guide the evaluation of the prognosis, severity and response to treatment of the disease.

Is there any role of interleukin-6 and high sensitive C-reactive protein in predicting IVF/ICSI success? A prospective cohort study

OBJECTIVES

Studies have established a relationship between proinflammatory factors and implantation failure in IVF/ICSI cycles. Likewise, low-grade chronic inflammation is generally blamed for predisposing infertility. In the present study, we aimed to find a relationship between serum IL-6 and hs-CRP levels and IVF/ICSI cycle outcomes.

METHODS

A total of 129 patients who consented to participate and attended the IVF unit of our department for the treatment of infertility have been enrolled in this prospective cohort study. Serum levels of high sensitive C-reactive protein and interleukin 6 have been detected at the beginning of the IVF/ICSI ovulation induction cycle. Cycle outcomes have been compared between patients with and without clinical pregnancy achievement following ART treatments. IVF/ICSI cycle outcomes of these two groups were also comparable except the number of >14 mm follicles, retrieved oocytes, metaphase II oocytes, and fertilized oocytes (2 pronuclei) which were in favor of the clinical pregnancy group.

RESULTS

Mean serum hs-CRP levels were 3.08 mg/L (0.12-35.04) and 2.28 mg/L (0.09-22.52) patients with and without clinical pregnancy respectively. Mean serum IL-6 levels were 2 pg/mL (1-10.2) and 2 pg/mL (1-76.9) patients with and without clinical pregnancy respectively. Both tests were found to be statistically insignificant in predicting the success of the ART cycle in terms of implantation, clinical pregnancy, miscarriage, and live birth.

CONCLUSIONS

In the present study, we have not found any significant effect of hs-CRP and IL-6 levels in the IVF cycle. However, in the light of this and previous studies, large-scale research may prove the exact influence of these markers on IVF success.

The imbalance of TNF and IL-6 levels and FOXP3 expression at the maternal-fetal interface is involved in adverse pregnancy outcomes in a susceptible murine model of congenital toxoplasmosis

Vertical transmission of Toxoplasma gondii leads to adverse pregnancy outcomes depending on the time at which the infection occurs and the immunological state of the mother. C57BL/6 and BALB/c mice have been described as susceptible and resistant mouse lineages to congenital T. gondii infection, respectively. This study aimed to elucidate the systemic and local cytokine profile of pregnant mice infected with T. gondii and whether the expression of the transcription factor FOXP3, related to T regulatory cells, is associated with the resistance/susceptibility of these lineages of mice in the context of experimental congenital toxoplasmosis. For this purpose, C57BL/6 and BALB/c females were orally infected with the T. gondii ME-49 strain on the day of vaginal plug detection or day 14 of gestation, examined 7 or 5 days later, respectively, as models of early and late pregnancy. Cytokine levels were measured systemically and in the uterus/placenta. Additionally, the uterus/placenta were evaluated macroscopically for resorption rates and histologically for parasite and FOXP3 immunostaining. The FOXP3 protein expression was also evaluated by western blotting assay. It was found that, during early pregnancy, the infection leads to high IFN-γ, TNF and IL-6 levels systemically, with the TNF levels being higher in C57BL/6 mice. At the maternal-fetal interface, the infection induced high levels of IFN-γ in both mouse lineages; however, higher levels were observed in BALB/c, while high TNF and IL-6 levels were found in C57BL/6, but not in BALB/c mice. In contrast, in late gestation, T. gondii interfered less strongly with the cytokine profile. In early pregnancy, a reduction of FOXP3 expression at the maternal-fetal interface of infected mice was also observed, and the reduction was larger in C57BL/6 compared with BALB/c mice. Additionally, the parasite was seldom found in the uterus/placenta. Thus, the worse pregnancy outcomes observed in C57BL/6 mice were associated with higher TNF systemically, and TNF and IL-6 at the maternal-fetal interface, with lower FOXP3 expression.

Association of gastrointestinal parasite burden, serum cytokines and hormones concentrations, and pregnancy in Angus-cross beef cows

The objective was to elucidate the relationships among gastrointestinal (GI) parasite load, serum cytokines (Th 1 - Interleukin (IL) 2, Interferon (IFN) γ and Tumor necrosis factor (TNF) α; Th 2- IL4, IL6, and IL10) levels, hormones (progesterone, cortisol, 8-epi-prostaglandin F2 alpha (isoprostane), prolactin, substance-p, and prostaglandin F metabolites) concentrations, and pregnancy in beef cattle. Angus-cross beef cows (n = 700; age, 3-8 y) were blocked by age and body condition score (BCS, 1-9), and were randomly assigned to treatment (n = 350, TRT, 50 mg of eprinomectin/50 kg BW, im) or control (n = 350, CON, no treatment) on Day -30. Cows were synchronized using Controlled Internal Drug Release insert (CIDR) + CO-Synch protocol and artificially inseminated at a fixed time on Day 0 (66 h after CIDR removal). Fecal samples were collected to determine fecal egg count per gram (FEG, McMaster method) on Days -30, -23, -16, -7, 7, 0, 16 and 23, and blood samples were collected on Days -7, 0, 7, 16 and 23. Serum cytokines were determined on Days -7, 0, 7, 16 and 23, and circulating hormones were measured on Day 16. BCS were recorded on Day 16 following artificial insemination (AI), and pregnancy status was diagnosed on Day 30 and 60. Pregnancy/AI varied among treatment groups on Day 30 [TRT, 62.0% (217/350); CON, 54.9% (192/350) (P = 0.05)] and Day 60 [TRT, 60.9% (213/350); CON, 51.7% (181/350) (P < 0.05)]. Pregnancy loss between 30 and 60 days for TRT and CON groups were 1.8% (4/217) and 5.7% (11/192), respectively (P < 0.05). The BCS on Day 16 did not differ among treatment groups (P> 0.1). Four groups of 40 cows were selected based on their pregnancy status and treatment: pregnant, TRT; non-pregnant, TRT; pregnant, CON; and non-pregnant, CON to compare the mean FEG, cytokines, and hormones levels. The FEG and cytokine concentrations were significantly (P < 0.05) influenced by treatment, pregnancy status, day, treatment by pregnancy status, and treatment by day. Day 16 hormone concentrations were considerably influenced by treatment, pregnancy status, and treatment by pregnancy. Although FEG on Day -30 did not differ among the groups (P> 0.1), it was lower in treated, pregnant cows compared with cows in other three groups from Day -23 onwards (P < 0.05). Overall and pairwise comparisons showed that serum concentrations of Type 1 cytokines, IL2, IFNγ, and TNFα were lower (P < 0.05) from gestational Day 7 onwards in treated, pregnant cows compared with cows in other three groups. In contrast, serum concentrations of Type 2 cytokines, IL4, IL6 and IL10 were greater (P < 0.05) from gestational Day 7 onwards in treated, pregnant cows compared with cows in other groups. Serum concentrations of progesterone was greater and other hormones were lower for pregnant cows in TRT group compared to cows in other groups on gestational Day 16. In conclusion, GI parasite load was reduced; Th 1 cytokines levels were decreased; Th 2 cytokines concentrations were increased; progesterone level was increased; and cortisol, substance-P, prolactin, isoprostane, and PGFM were decreased in pregnant, TRT cows. These changes also resulted in an increase in P/AI. It is plausible that direct and bidirectional host-parasite interactions mediated by cytokines and hormones may have promoted maternal tolerance of an immunologically diverse conceptus and the establishment of pregnancy.

Eutherian-Specific Gene TRIML2 Attenuates Inflammation in the Evolution of Placentation

Evolution of highly invasive placentation in the stem lineage of eutherians and subsequent extension of pregnancy set eutherians apart from other mammals, that is, marsupials with short-lived placentas, and oviparous monotremes. Recent studies suggest that eutherian implantation evolved from marsupial attachment reaction, an inflammatory process induced by the direct contact of fetal placenta with maternal endometrium after the breakdown of the shell coat, and shortly before the onset of parturition. Unique to eutherians, a dramatic downregulation of inflammation after implantation prevents the onset of premature parturition, and is critical for the maintenance of gestation. This downregulation likely involved evolutionary changes on maternal as well as fetal/placental side. Tripartite-motif family-like2 (TRIML2) only exists in eutherian genomes and shows preferential expression in preimplantation embryos, and trophoblast-derived structures, such as chorion and placental disc. Comparative genomic evidence supports that TRIML2 originated from a gene duplication event in the stem lineage of Eutheria that also gave rise to eutherian TRIML1. Compared with TRIML1, TRIML2 lost the catalytic RING domain of E3 ligase. However, only TRIML2 is induced in human choriocarcinoma cell line JEG3 with poly(I:C) treatment to simulate inflammation during viral infection. Its knockdown increases the production of proinflammatory cytokines and reduces trophoblast survival during poly(I:C) stimulation, while its overexpression reduces proinflammatory cytokine production, supporting TRIML2’s role as a regulatory inhibitor of the inflammatory pathways in trophoblasts. TRIML2’s potential virus-interacting PRY/SPRY domain shows significant signature of selection, suggesting its contribution to the evolution of eutherian-specific inflammation regulation during placentation.

Expression of trophoblast derived prostaglandin E2 receptor 2 (EP2) is reduced in patients with recurrent miscarriage and EP2 regulates cell proliferation and expression of inflammatory cytokines

BACKGROUD

Prostaglandin E2 (PGE2), an inflammatory mediator, modulates cytokines, regulates immune responses in reproductive processes and stimulates inflammatory reactions via the prostaglandin E2 receptor 2 (EP2). However, the regulatory effects of EP2 signaling on trophoblasts and its role in unexplained recurrent miscarriage (uRM) remains unclear.

PATIENTS AND METHODS

A total of 19 placentas from patients with a history of more than two consecutive pregnancy losses of unknown cause (uRM group) and placentas of 19 healthy patients following a legal termination of their pregnancy were used for PGE2 receptor (EP1, EP2 and EP4) expression analyses via immunohistochemistry. Double immunofluorescence was also used to identify EP2 expressing cells in the decidua. Finally, HTR-8/SVneo cells were used to clarify the role of EP2 in in vitro experiments.

RESULTS

The expression of EP2 and EP4 was found to be reduced in the syncytiotrophoblast and decidua of uRM patients. A selective EP2 receptor antagonist (PF-04,418,948) reduced the proliferation and secretion of ß-hCG, inhibited interleukin -6 (IL-6) and interleukin-8 (IL-8) and up-regulated the production of the tumor necrosis factor-α (TNF-α) and plasminogen activator inhibitor type 1 (PAI-1) in HTR-8/SVneo cells in vitro.

CONCLUSION

PGE2-EP2 signaling pathway may represent a novel therapy option for uRM. The involvement of EP2 in uRM acts perhaps via inflammatory cytokines and indicates that the PGE2-EP2 signaling pathway might represent an unexplored etiology for uRM.

IκBNS and IL-6 expression is differentially established in the uterus of pregnant healthy and infected mice

During pregnancy, NF-κB plays an important role for embryo implantation and the onset of labor. Regulated IL-6 production, under transcriptional control of NF-κB, is essential for a successful pregnancy outcome and the atypical regulator IκBNS is involved in this process. Previously, we showed that IκBNS negatively regulates IL-6 in uterine tissues during mouse estrous cycle. In this work, we analyzed if IκBNS and IL-6 expression in pregnant mice under physiological or L. monocytogenes-infected conditions would remain as observed in estrous cycle. In the healthy pregnancy IL-6 was highly expressed during implantation/placentation and labor stages but decreased during fetal development and post-partum stages. In contrast, in mice infected before pregnancy, IL-6 expression was not increased in the implantation stage, and its regulator IκBNS increased more in the infected condition rather than in the healthy pregnancy. IκBNS expression was reduced in post-implantation infection, allowing for IL-6 overexpression. The IκBNS-unrelated cytokine IL-36γ, used as inflammatory cytokine marker, was severely increased in the infected uterine tissues. When we analyzed the effect of infection over the fetuses, we found that pre-implantation infection caused the resorption (rejection) of some products, while the post-implantation infection restricted the intrauterine growth of fetuses. The results suggest that in the uterine tissue of pregnant mice the regulatory effect of IκBNS over IL-6 is more evident in an infection status rather than in a healthy condition.

Regulatory B cells with IL-35 and IL-10 expression in a normal and abortion-prone murine pregnancy model

PROBLEM

Interleukin 35 is a relatively newly discovered cytokine that is produced by regulatory B cells (Bregs) and contributes to their suppressive function, which may contribute to fetal tolerance development and pregnancy maintenance. Therefore, the aim of this study was to determine the frequency of Bregs and expression of IL-35 and IL-10 in these cells in a normal and abortion-prone murine pregnancy model.

METHODS OF STUDY

The frequency of Bregs and expression level of IL-35 and IL-10 in these cells were measured in peripheral blood, uterine draining lymph nodes, uterus, and decidua using flow cytometry. The analysis was performed on days 3 and 14 of pregnancy in normal mice (CBA/JxBALB/c) and abortion-prone (CBA/JxDBA/2J) murine pregnancy model.

RESULTS

A decreased percentage of Breg cells expressing IL-35 on day 3 of pregnancy in the uterine draining lymph nodes and in peripheral blood in mice from the abortion group compared with the normal pregnancy group was observed. A similar decrease was also observed in the Breg cells population producing IL-10 in peripheral blood. In the uterus (3 dpc) and decidua (14 dpc), a lower percentage of CD19⁺ IL-35⁺ was also noted in the abortion-prone model.

CONCLUSION

We indicated that the early stages of abortion-prone pregnancy (3 dpc) in mice were characterized by diminished frequency of B cells producing IL-35 at both local and peripheral levels. These results and the observed lower level of IL-35 in women suffering from recurrent spontaneous abortion suggest that IL-35 may be involved in the maintenance of pregnancy.

A diet enriched in longer chain omega-3 fatty acids reduced placental inflammatory cytokines and improved fetal sustainability of C57BL/6 mice

Omega (n)-3 polyunsaturated fatty acids (PUFA) are important regulators of inflammatory response that may impact pregnancy outcome. The effects of breeding chow diets containing n-3 PUFA from either fish oil (FO) or soybean oil (SO) were investigated on tissue fatty acid composition, inflammatory cytokines and pregnancy outcome. Female C57BL/6 mice (7 weeks old) were fed FO or SO diets for 2 weeks before mating and throughout pregnancy. Animals were sacrificed before and during pregnancy at day 6.5, 12.5 and 18.5. The FO diet increased the incorporation of n-3 PUFA in placenta, with a concomitant decrease in the concentration of pro-inflammatory cytokines. The FO diet increased the mRNA expression of placental specific PUFA transporter, which coincided with accretion of n-3 PUFA in fetal brain. Sites of fetal resorption were noticeable in the SO group but not in the FO group. N-3 PUFA may improve fetal sustainability via altering cytokine levels.

The role of Th17/Treg-mediated immunoregulation in abortion mice

In the study, we investigated the immune factors related to T helper 17 (Th17) cells and T regulatory (Treg) cells in spontaneous abortion mice. The expression of Th17 was analyzed by interleukin (IL)-6, IL-17A secretion, RAR-related orphan receptor γt (RORγt) expression, and proportion of CD4+IL-17+ cells. The levels of IL-10, transforming growth factor β (TGF-β), Foxp3, and CD4+Foxp3+ cells were presented the Treg expression. Higher embryo absorption rate was found in spontaneous abortion group than that in normal pregnancy group ( P < 0.01). Compared with the normal pregnancy mice, spontaneous abortion mice showed higher levels of IL-6 and IL-17A and lower levels of IL-10 and TGF-β in serum and in decidua ( P < 0.05). Furthermore, the expressions of Foxp3 and CD4+Foxp3+ cells were significantly decreased in spontaneous abortion mice than those in normal pregnancy mice ( P < 0.05). However, the levels of RORγt and CD4+IL-17+ cells remarkably increased in spontaneous abortion mice ( P < 0.05). The results reveal that Th17/Treg cells may play a vital role in immunoregulation during pregnancy.

Lymphocytes in Placental Tissues: Immune Regulation and Translational Possibilities for Immunotherapy

Immune modulation at the fetomaternal interface is crucial to ensure that the fetal allograft is not rejected. In the present review, the focus is to describe basic functions of lymphocyte populations and how they may contribute to fetomaternal immune regulation, as well as determining what proportions and effector functions of these cells are reported to be present in placental tissues in humans. Also explored is the possibility that unique cell populations at the fetomaternal interface may be targets for adoptive cell therapy. Increasing the understanding of immune modulation during pregnancy can give valuable insight into other established fields such as allogeneic hematopoietic stem cell transplantation and solid organ transplantation. In these settings, lymphocytes are key components that contribute to inflammation and rejection of either patient or donor tissues following transplantation. In contrast, an allogeneic fetus eludes rejection by the maternal immune system.

Increase in complement iC3b is associated with anti-inflammatory cytokine expression during late pregnancy in mice

Immunological tolerance between fetal allograft and mother is crucial for pregnancy establishment and maintenance; however, these mechanisms particularly those during the latter part of pregnancy have not been definitively elucidated. The aim of this study was to examine the presence and potential function of innate immunity characteristic to the middle to late pregnancy. We first characterized up-regulated proteins in decidua from day 11 pregnant (P11) mice using 2D-PAGE, followed by MALDI-TOF/MS analysis. These analyses identified increased complement component 3 (C3) and its derivatives in P11 decidua. We then found that in the decidual tissues, C3 mRNA increased on P15 and remained high on P19. C3 is converted to C3b and then iC3b by complement component factor I (Cfi) and complement receptor 1-like protein (Crry), both of which were present in P19 placentas. In addition, iC3b proteins and its receptor CR3 (Cd11b/Cd18) in decidual and placental tissues increased toward the latter phase of pregnancy. Moreover, CR3 subunit CD11b protein was predominantly localized to spongiotrophoblast layer in the P19 placenta. Because iC3b is known to induce anti-inflammatory cytokine production, the analysis was extended to examine changes in pro- and anti-inflammatory cytokines, Il12, Il10, and Tgfb1. Il12 expression decreased in P15 and P19 placenta, while high mRNA expression of Il10 and Tgfb1 was found in P19 placental tissues. Furthermore, placental Il10 and Tgfb1 mRNAs were down-regulated when pregnant mice were treated with an anti-C3 antibody, detecting C3, C3b and iC3b. These results indicated that C3 derivatives, in particular, iC3b and its receptor CR3 were up-regulated at the fetal-maternal interface, and suggest that iC3b may regulate the placental expression of anti-inflammatory cytokines, IL10 and TGFB1, during the latter phase of pregnancy.

The T helper type 17/regulatory T cell paradigm in pregnancy

T helper type 17 (Th17) and regulatory T (Treg) cells are active players in the establishment of tolerance and defence. These attributes of the immune system enmesh to guarantee the right level of protection. The healthy immune system, on the one hand, recognizes and eliminates dangerous non-self pathogens and, on the other hand, protects the healthy self. However, there are circumstances where this fine balance is disrupted. In fact, in situations such as in pregnancy, the foreign fetal antigens challenge the maternal immune system and Treg cells will dominate Th17 cells to guarantee fetal survival. In other situations such as autoimmunity, where the Th17 responses are often overwhelming, the immune system shifts towards an inflammatory profile and attacks the healthy tissue from the self. Interestingly, autoimmune patients have meliorating symptoms during pregnancy. This connects with the antagonist role of Th17 and Treg cells, and their specific profiles during these two immune challenging situations. In this review, we put into perspective the Th17/Treg ratio during pregnancy and autoimmunity, as well as in pregnant women with autoimmune conditions. We further review existing systems biology approaches that study specific mechanisms of these immune cells using mathematical modelling and we point out possible future directions of investigation. Understanding what maintains or disrupts the balance between these two opponent yet reciprocal cells in healthy physiological settings, sheds light into the development of innovative pharmacological approaches to fight pregnancy loss and autoimmunity.

Disrupted PI3K p110δ Signaling Dysregulates Maternal Immune Cells and Increases Fetal Mortality In Mice

Maternal immune cells are an integral part of reproduction, but how they might cause pregnancy complications remains elusive. Macrophages and their dual function in inflammation and tissue repair are thought to play key yet undefined roles. Altered perinatal growth underpins adult morbidity, and natural killer (NK) cells may sustain fetal growth by establishing the placental blood supply. Using a mouse model of genetic inactivation of PI3K p110δ, a key intracellular signaling molecule in leukocytes, we show that p110δ regulates macrophage dynamics and NK-cell-mediated arterial remodeling. The uterus of dams with inactive p110δ had decreased IFN-γ and MHC class II^low macrophages but enhanced IL-6. Poor vascular remodeling and a pro-inflammatory uterine milieu resulted in fetal death or growth retardation. Our results provide one mechanism that explains how imbalanced adaptations of maternal innate immune cells to gestation affect offspring well-being with consequence perinatally and possibly into adulthood.

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Genetic inactivation of p110δ in pregnant mice perturbs maternal immune cells

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Uterine NK cells produce less cytokines, resulting in fetal growth restriction

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Inflammatory macrophages are overrepresented, resulting in increased fetal loss

Isolation of Leukocytes from the Murine Tissues at the Maternal-Fetal Interface

Immune tolerance in pregnancy requires that the immune system of the mother undergoes distinctive changes in order to accept and nurture the developing fetus. This tolerance is initiated during coitus, established during fecundation and implantation, and maintained throughout pregnancy. Active cellular and molecular mediators of maternal-fetal tolerance are enriched at the site of contact between fetal and maternal tissues, known as the maternal-fetal interface, which includes the placenta and the uterine and decidual tissues. This interface is comprised of stromal cells and infiltrating leukocytes, and their abundance and phenotypic characteristics change over the course of pregnancy. Infiltrating leukocytes at the maternal-fetal interface include neutrophils, macrophages, dendritic cells, mast cells, T cells, B cells, NK cells, and NKT cells that together create the local micro-environment that sustains pregnancy. An imbalance among these cells or any inappropriate alteration in their phenotypes is considered a mechanism of disease in pregnancy. Therefore, the study of leukocytes that infiltrate the maternal-fetal interface is essential in order to elucidate the immune mechanisms that lead to pregnancy-related complications. Described herein is a protocol that uses a combination of gentle mechanical dissociation followed by a robust enzymatic disaggregation with a proteolytic and collagenolytic enzymatic cocktail to isolate the infiltrating leukocytes from the murine tissues at the maternal-fetal interface. This protocol allows for the isolation of high numbers of viable leukocytes (>70%) with sufficiently conserved antigenic and functional properties. Isolated leukocytes can then be analyzed by several techniques, including immunophenotyping, cell sorting, imaging, immunoblotting, mRNA expression, cell culture, and in vitro functional assays such as mixed leukocyte reactions, proliferation, or cytotoxicity assays.

Decidual cytokines and pregnancy complications: focus on spontaneous miscarriage

The establishment of pregnancy requires the co-ordinated implantation of the embryo into the receptive decidua, placentation, trophoblast invasion of the maternal decidua and myometrium in addition to remodelling of the uterine spiral arteries. Failure of any of these steps can lead to a range of pregnancy complications, including miscarriage, pre-eclampsia, fetal growth restriction, placenta accreta and pre-term birth. Cytokines are small multifunctional proteins often derived from leucocytes and have primarily been described through their immunomodulatory actions. The maternal-fetal interface is considered to be immunosuppressed to allow development of the semi-allogeneic placental fetal unit. However, cytokine profiles of the decidua and different decidual cell types suggest that the in vivo situation might be more complex. Data suggest that decidual-derived cytokines not only play roles in immunosuppression, but also in other aspects of the establishment of pregnancy, including the regulation of trophoblast invasion and spiral artery remodelling. This review focuses on the potential role of decidua-derived cytokines in the aetiology of unexplained spontaneous miscarriage.

Increased cystic fibrosis transmembrane conductance regulators expression and decreased epithelial sodium channel alpha subunits expression in early abortion: findings from a mouse model and clinical cases of abortion

The status of the maternal endometrium is vital in regulating humoral homeostasis and for ensuring embryo implantation. Cystic fibrosis transmembrane conductance regulators (CFTR) and epithelial sodium channel alpha subunits (ENaC-α) play an important role in female reproduction by maintaining humoral and cell homeostasis. However, it is not clear whether the expression levels of CFTR and ENaC-α in the decidual component during early pregnancy are related with early miscarriage. CBA×DBA/2 mouse mating has been widely accepted as a classical model of early miscarriage. The abortion rate associated with this mating was 33.33% in our study. The decidua of abortion-prone CBA female mice (DBA/2 mated) had higher CFTR mRNA and protein expression and lower ENaC-α mRNA and protein expression, compared to normal pregnant CBA mice (BLAB/C mated). Furthermore, increased CFTR expression and decreased ENaC-α expression were observed in the uterine tissue from women with early miscarriage, as compared to those with successful pregnancy. In conclusion, increased CFTR expression and decreased ENaC-α expression in the decidua of early abortion may relate with failure of early pregnancy.

To drive or be driven: the path of a mouse model of recurrent pregnancy loss

This review is an example of the use of an animal model to try to understand the immune biology of pregnancy. A well-known model of recurrent spontaneous pregnancy loss is put in clinical, historical, and theoretical context, with emphasis on T cell biology.

Profile of maternal CD4 T-cell effector function during normal pregnancy and in women with a history of recurrent miscarriage

The traditional paradigm suggests that during normal pregnancy maternal immunological tolerance of the allogenic fetus is association with a maternal T-lymphocyte shift from a Th1 to a Th2 phenotype, with the opposite effect reported in patients with recurrent miscarriage. However, studies on maternal peripheral blood are conflicting. In the present study, we characterized the maternal CD4 T-cell effector subsets, including the recently described Th17 subset, during normal pregnancy (cross-sectional cohort, n=71; longitudinal cohort, n=17) and contrasted this with women with recurrent miscarriage (n=24). Longitudinal analysis of peripheral blood from normal pregnancy demonstrated a fall in the percentage of Th17 cells between the first and second trimester (P≤0.05), but no significant changes were observed across gestation or the post-natal period in Th1 or Th2 subsets. In contrast, in women with a history of recurrent miscarriage, an elevated proportion of Th17 (0.314% compared with 0.097%; P=0.0009) and Th1 (12.4% compared with 5.3%; P=0.0002) cells was detected. The suggestion that Th17 cells may have a role in the normal events of implantation and early pregnancy requires further evaluation and mechanistic studies. The results of the present study, by conducting a careful longitudinal analysis, demonstrate that a peripheral Th1/Th2 shift is not a requirement for normal pregnancy. By contrast, the profound increase in Th1 and Th17 cells in women with recurrent miscarriage indicates that peripheral immunological dysfunction may be important in this group specifically, and these assays may be important in guiding therapeutic interventions in this group and warrant further investigation to determine whether they are predictive of outcome or responses to immunomodulatory therapy.

Altered expression of interleukin-6, interleukin-8 and their receptors in decidua of women with sporadic miscarriage

STUDY QUESTION

Are alterations in decidual expression of interleukin (IL)-6 and IL-8 associated with sporadic miscarriage?

SUMMARY ANSWER

IL-6 and IL-8 secretion from decidual uterine natural killer (uNK) cells and macrophages isolated from women with spontaneous miscarriage was reduced compared with normal controls.

WHAT IS KNOWN ALREADY

Miscarriage is a common gynaecological problem with huge financial and personal implications. Eleven to twenty per cent of all clinically recognized pregnancies are lost before the 20th week of gestation, with miscarriages often being divided into early (≤ 12 completed weeks from last menstrual period) and late (≥ 13 weeks). Spiral artery remodelling is a key feature of early pregnancy; failure of this process has been implicated in sporadic miscarriage. The molecular triggers that initiate spiral artery remodelling are not clear, although cytokines such as IL-6 and IL-8 may play a role.

STUDY DESIGN, SIZE, DURATION

This was a laboratory-based study using decidual and placental bed biopsy samples from women with sporadic miscarriage (n = 30) and termination of pregnancy controls (n = 30).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Total adherent decidual cells, CD10(+) stromal cells, CD14(+) macrophages and CD56(+) uNK cells were isolated from decidua from apparently normal pregnancies that were terminated at either 8-10 or 12-14 weeks' gestation. In addition, CD14(+) macrophages and CD56(+) uNK cells were isolated from decidua from sporadic miscarriage at 8-10 weeks' gestation. Secreted IL-8 was measured in all isolated cell populations, while IL-6 was measured in CD14(+) macrophages and CD56(+) uNK cells from both sporadic miscarriage and normal controls. Placental bed biopsies were taken from women after sporadic miscarriage or termination of pregnancy at ≤ 12 completed weeks' or >13 weeks' gestational age, formalin-fixed, paraffin-embedded and immunostained for IL-6, IL-6Rα, GP130, IL-8, CXCR1, CXCR2 and CD13 (aminopeptidase N). Staining intensity for each factor was assessed in extravillous trophoblast cell populations, myometrial and decidual stroma, myometrial and decidual spiral arteries and decidual glandular epithelium. A CPA model was used to assess the potential role of IL-6 and IL-8 in spiral artery remodelling.

MAIN RESULTS AND THE ROLE OF CHANCE

IL-8 was secreted by total adherent decidual cells, CD10(+) stromal cells and CD14(+) macrophages at both 8-10 and 12-14 weeks' gestation, with CD14(+) cells secreting the highest levels. Both CD14(+) and CD56(+) cells isolated from decidua of early sporadic miscarriage produced lower IL-6 (P = 0.04, P = 0.01, respectively) and IL-8 levels (P = 0.0007, P = 0.002, respectively) compared with normal cases. In addition, altered expression of IL-6, IL-8 and their receptors was observed in various cell types in placental bed (myometrial stroma, glandular epithelium, interstitial extravillous trophoblast cells, vascular smooth muscle cells and endothelial cells) in sporadic miscarriage, particularly from later gestational ages. IL-6 and IL-8 disrupted vascular smooth muscle morphology and organization in an in vitro model of spiral artery remodelling.

LIMITATIONS, REASONS FOR CAUTION

By the nature of sampling at the time of miscarriage, it was not possible to ascertain the cause or effect in the observed alterations of levels of IL-6 and IL-8 in sporadic miscarriage.

WIDER IMPLICATIONS OF THE FINDINGS

Alterations in the expression of IL-6, IL-8 and their receptors may be associated with the aetiology of sporadic miscarriage, especially given the potential role of these cytokines in the regulation of trophoblast invasion and spiral artery remodelling.

STUDY FUNDING/COMPETING INTEREST(S)

This project was supported by funding from Wellbeing of Women (RG1000). The authors have no competing interests to declare.

TRIAL REGISTRATION NUMBER

Not applicable.

HO-1 as modulator of the innate immune response in pregnancy

PROBLEM

The immune modulatory effect of heme oxygenase-1 (HO-1) is well documented in studies about sepsis and transplantation. This work evaluates the influence of HO-1 on the innate immune response during pregnancy.

METHOD OF STUDY

Human first-trimester trophoblasts derived from normal pregnancies or spontaneous abortions were analyzed for their basal HO-1, BCL-associated athanogene-1 (Bag-1), and cytokine production before and after LPS treatment. In vivo, pregnant Hmox1+/+ and Hmox1+/- female mice were treated with LPS, and the production of Bag-1 was evaluated.

RESULTS

Human trophoblasts up-regulated the expression of both HO-1 and pro-inflammatory cytokines after LPS treatment, whereas the basal level of HO-1 was higher in normal pregnancies. In vivo, HO-1 deficiency provoked diminished Bag-1 level upon LPS treatment.

CONCLUSION

HO-1 deficiency causes an inflammatory immune reaction and diminished expression of protective molecules in trophoblasts. Thus, HO-1 emerges as one important modulator of innate immune responses in pregnancy.

Interleukin-6 in pregnancy and gestational disorders

IL6 is a multifunctional cytokine with pivotal roles in the inflammatory response and in directing T cell differentiation in adaptive immunity. IL6 is widely expressed in the female reproductive tract and gestational tissues, and exerts regulatory functions in embryo implantation and placental development, as well as the immune adaptations required to tolerate pregnancy. Here, we summarise the current understanding of how membrane-bound and soluble receptors mediate IL6 signalling to regulate leukocytes and non-haemopoietic cells. We review the published literature regarding the expression and actions of IL6 in the uterus, decidua and placenta, and studies implicating this cytokine in pregnancy disorders. Elevated IL6 is frequently evident in the altered cytokine profiles characteristic of unexplained infertility, recurrent miscarriage, preeclampsia and preterm delivery. Notably, there is compelling evidence indicating altered systemic IL6 trans-signalling in women prone to recurrent miscarriage, with excessive IL6 bioavailability potentially inhibiting generation of CD4+ T regulatory cells required for pregnancy tolerance. Insufficient local IL6 may also contribute to fetal loss, since IL6 expression is reduced in the endometrium of women with recurrent miscarriage, and in the fetal-placental tissue of CBA×DBA/2 mice. Consistent with the role of IL6 in key reproductive events, Il6 null mutant mice exhibit elevated fetal resorption and delayed parturition. Investigation of the association between IL6 signalling components and T cell responses in pregnant women, as well as detailed analysis of the maternal immune response in IL6-deficient mice, is now required to define the mechanisms by which this cytokine exerts influence on reproductive success.

Smoking during pregnancy influences the maternal immune response in mice and humans

OBJECTIVE

During pregnancy the maternal immune system has to adapt its response to accommodate the fetus. The objective of this study was to analyze the effects of smoking on the maternal immune system.

STUDY DESIGN

First-trimester decidual tissue and peripheral blood of smoking and nonsmoking women were analyzed by real time reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometry. A mouse model was used to further analyze the effects of smoking. Murine tissue was analyzed by flow cytometry, real-time RT-PCR, and immunohistochemistry.

RESULTS

Smoking caused lower percentages of viable pups in mice and lower birthweights in humans. Smoking mothers, both mice and human, had more natural killer cells and inflammatory macrophages locally, whereas systemically they had lower percentages of regulatory T cells than nonsmoking controls.

CONCLUSION

Maternal smoke exposure during pregnancy influences local and systemic immune responses in both women and mice. Such changes may be involved in adverse pregnancy outcomes in smoking individuals.

Soluble BAFF-R produced by decidual stromal cells plays an inhibitory role in monocytes and macrophages

A sophisticated immunological regulation between decidual stromal cells (DSC) and monocytes and macrophages is essential for the successful symbiosis of the mother and her fetus, but the mechanisms remain incompletely understood. The mRNA and proteins of B lymphocyte stimulator (BAFF, also known as BLys) and its receptor, BAFF-R (also known as BR3, CD268 or TNFRSF17), have been detected in both first-trimester and term placentas, but whether BAFF or BAFF-R participates in the cross-talk between DSC and monocytes and macrophages in the first-trimester pregnancy has not been described. This study found that purified DSC extensively shed BAFF-R and that polyinosinic:polycytidylic acid (poly(I:C); a synthetic toll-like receptor (TLR) 3 agonist) dramatically up-regulated BAFF-R secretion, suggesting that release of these soluble proteins was an inherent property of DSC and its induction might have relevance to TLR-3-mediated signal transduction. When monocytes were cultured with the supernatants of resting DSC or poly(I:C)-treated DSC, the proliferation of CD14(+)HLA-DR(+) monocytes (P=0.025 and 0.045) and the secretion levels of tumour necrosis factor α (P=0.035 and 0.031) and interleukin 6 (P=0.021 and 0.035) were significantly increased after the BAFF-R was blocked. Soluble BAFF-R may play inhibitory roles in monocytes and macrophages.

Disruption of gap junctions reduces biomarkers of decidualization and angiogenesis and increases inflammatory mediators in human endometrial stromal cell cultures

CONTEXT

Uterine decidualization is critical to embryonic implantation and sustained pregnancy.

OBJECTIVE

To evaluate the role of gap junction intercellular communications and connexin (Cx) proteins in the morphological and biochemical differentiation of decidualized human endometrial stromal cell (ESC) cultures.

DESIGN

Translational cell biological study.

SETTING

Academic medical center.

PATIENTS

Endometrial tissue was provided by five healthy reproductive age women on no hormonal medication, undergoing laparoscopy in the early proliferative phase of the menstrual cycle.

INTERVENTIONS

Endometrial biopsy under general anesthesia, establishment and decidualization of ESC with 10 nM 17β-estradiol, 100 nM progesterone and 0.5 mM dibutyryl-cAMP (E/P/c), and manipulation of gap junctions in vitro via a combination of pharmacological or transgenic approaches.

MAIN OUTCOME MEASURES

Decidualized ESC evaluated morphologically for epithelioid transformation, gap junctions by dye diffusion and Cx43, prolactin, VEGF and IL-6 expression by RT-PCR, Western and ELISA methods.

RESULTS

Cx43 accumulation and functional gap junctions between decidualized ESC increase concomitantly with morphological differentiation following E/P/c treatment. Disruption of gap junctions using pharmacological inhibitors or Cx43 shRNA prevents morphological differentiation and inhibits prolactin and VEGF secretion. By contrast, IL-6 secretion from decidualized ESC is augmented by both approaches.

CONCLUSIONS

The findings suggest that decidualized ESC function as a coordinated secretory organ to regulate embryonic implantation via intercellular cooperation mediated by gap junctions. When adjacent cells can communicate through these junctions, decidual prolactin and VEGF secretion appears to be optimized for vascular development of the placental bed. Conversely, when intercellular communications are disrupted, angiogenesis is impaired and an inflammatory state is induced.

Fetomaternal immunotolerance

Implantation of mammalian conceptus in uterine cavity is the result of evolutionary adaptation, through high level of physiological procedures to ensure its success. However the majority of pregnancy losses occur before or during implantation. It is expected that exploring and defining the molecular and physiological road map during the crucial time of implantation will enable us to decode and effectively treat fertility defects. Immunological, hormonal and molecular factors participate in the feto-maternal cross talk during implantation and designate the effectiveness of the process. The atypical expression of major histocompatibility complex and other protein-antigens, such as Fas/FasL and petformin in human trophoblast, the modified function of cellular constituents of the feto-maternal interface, as well as the specific role of some hormones and cytokines, represent substantive parameters of feto-maternal immunotolerance during implantation.

Downregulation of cilia-localized Il-6Rα by 17β-estradiol in mouse and human fallopian tubes

The action of interleukin-6 (IL-6) impacts female reproduction. Although IL-6 was recently shown to inhibit cilia activity in human fallopian tubes in vitro, the molecular mechanisms underlying IL-6 signaling to tubal function remain elusive. Here, we investigate the cellular localization, regulation, and possible function of two IL-6 receptors (IL-6Rα and gp130) in mouse and human fallopian tubes in vivo. We show that IL-6Rα is restricted to the cilia of epithelial cells in both mouse and human fallopian tubes. Exogenous 17β-estradiol (E2), but not progesterone (P4), causes a time-dependent decrease in IL-6Rα expression, which is blocked by the estrogen receptor (ER) antagonist ICI-182,780. Exposure of different ER-selective agonists propyl-(1H)-pyrazole-1,3,5-triyl-trisphenol or 2,3-bis-(4-hydroxyphenyl)-propionitrile demonstrated an ER subtype-specific regulation of IL-6Rα in mouse fallopian tubes. In contrast to IL-6Rα, gp130 was detected in tubal epithelial cells in mice but not in humans. In humans, gp130 was found in the muscle cells and was decreased in the periovulatory and luteal phases during the reproductive cycles, indicating a species-specific expression and regulation of gp130 in the fallopian tube. Expression of tubal IL-6Rα and gp130 in IL-6 knockout mice was found to be normal; however, E2 treatment increased IL-6Rα, but not gp130, in IL-6 knockout mice when compared with wild-type mice. Furthermore, expression levels of IL-6Rα, but not gp130, decreased in parallel with estrogenic accelerated oocyte-cumulus complex (OCC) transport in mouse fallopian tubes. Our findings open the posibility that cilia-specific IL-6Rα may play a role in the regulation of OCC transport and suggest an estrogen-regulatory pathway of IL-6Rα in the fallopian tube.

Toxoplasma gondii: effect of maternal infection in the development of lymphoid organs of BALB/c neonates

Toxoplasmosis is one of the worldwide parasitic zoonoses. Alterations in the lymphopoietic system are still poorly studied. We analyzed lymphoid organs of BALB/c mice neonates from Toxoplasma gondii-intraperitoneally-infected mothers on 19th day of gestation, with 30 tachyzoites of strain RH. Normal non-infected pregnant females were used as controls. At 7 days after birth, animals were classified as neonates from infected (NIM) and neonates from non-infected mothers (NNIM). Weight of the thymus and number of thymic cells in NIM were decreased, percentage of apoptosis was significantly increased. Decrease in lymphocytes and monocytes and an increase of plasma cells were observed in bone marrow of NIM. Peripheral blood of NIM showed an increase of monocytes and neutrophils and a decrease in lymphocytes. Infection of the mother during the last day of gestation provokes in the neonates changes in the lymphoid organs that could explain survival of 75% of them.

Mechanisms behind flare of renal lupus during murine pregnancy

The outcome of pregnancy in systemic lupus erythematosus is still controversial. The authors recently reported the disappearance of the manifestation of the skin disease but a diminished survival rate in lupus-prone animals undergoing several pregnancies. It was postulated that lupus-prone animals must have subclinical renal symptoms at an early age and that immune and hormonal changes during pregnancy exacerbate immune reactions in the kidneys, leading to a shortened life span. Here, the authors analysed changes at day 14 of pregnancy in lupus-prone LPR (MRL/lpr) mice and MRL controls regarding cytokines, regulatory T (Treg) cells and deposition of immunocomplexes. Worsened kidney function was observed during pregnancy, even in the absence of lupus signs. This was accompanied by renal inflammation and higher interferon-gamma and interleukin-10 levels. C3 and immunoglobulin G deposition was enhanced in kidney and placenta from lupus-prone pregnant animals. Pregnancy enhanced the levels of Treg cells in control animals but not in lupus-prone animals. As pregnancy-induced Treg cells were shown to be specific for paternal antigens it is not to be expected that these Treg cells can help to destroy autoreactive cells. The authors conclude that early subclinical kidney disease in lupus-prone animals exacerbates during pregnancy. Albeit obtained with an experimental animal model, their data are potentially of importance for lupus patients of reproductive age.

Antigen-presenting cells and materno-fetal tolerance: an emerging role for dendritic cells

During pregnancy, a delicate balance of innate and adaptive immune responses at the maternal-fetal interface promotes survival of the semi-allogeneic embryo and, at the same time, allows effective immunity to protect the mother from environmental pathogens. As in other tissues, antigen handling and processing in the decidualized endometrium constitutes a primary event in the onset of immune responses and is therefore likely to determine their stimulatory or tolerogenic nature. Maternal antigen-presenting cells [macrophages and dendritic cells (DCs)] are scattered throughout the decidualized endometrium during all stages of pregnancy and appear to be important players in this feto-maternal immune adjustment. This review focuses on the characterization of decidual macrophages and DCs, as well as their involvement in cell-cell interactions within the decidual leukocyte network, which are likely to influence uterine and placental homeostasis as well as the local maternal immune responses to the fetus during pregnancy.

Cytokines: Important for implantation?

PROBLEM

Cytokines are obviously very important in an established pregnancy, but what about human embryo implantation?

METHODS

Literature review.

RESULTS

We first discuss the necessity and limits of animal models, and then review the few cytokines which have been demonstrated by knock-out methods to be absolutely necessary for embryo implantation using in animal models. We then review what is known or discussed about the role of other cytokines as deduced from quantitative and/or qualitative dysregulation in animals and in humans.

CONCLUSIONS

Cytokines are indeed involved in implantation as they are in ongoing pregnancy and delivery. Relevance to infertility and recurrent pregnancy loss is discussed.

Interleukin 10 Regulates Inflammatory Cytokine Synthesis to Protect Against Lipopolysaccharide-Induced Abortion and Fetal Growth Restriction in Mice1

Interleukin 10 (IL10) is a potent immune-regulating cytokine and inhibitor of inflammatory cytokine synthesis. To evaluate the anti-inflammatory role of IL10 in pregnancy, the response of genetically IL10-deficient mice to low-dose lipopolysaccharide (LPS)-induced abortion was examined. When IL10-null mutant C57Bl/6 (Il10(-/-)) and control (Il10(+/+)) mice were administered low-dose LPS on Day 9.5 of gestation, IL10 deficiency predisposed to fetal loss accompanied by growth restriction in remaining viable fetuses, with an approximately 10-fold reduction in the threshold dose for 100% abortion. After LPS administration, inflammatory cytokines tumor necrosis factor-alpha (TNFA) and IL6 were markedly increased in serum, uterine, and conceptus tissues in Il10(-/-) mice compared with Il10(+/+) mice, with elevated local synthesis of Tnfa and Il6 mRNAs in the gestational tissues. IL1A and IL12p40 were similarly elevated in serum and gestational tissues, whereas interferon gamma (IFNG) and soluble TNFRII content were unchanged in the absence of IL10. Recombinant IL10 rescued the increased susceptibility to LPS-induced fetal loss in Il10(-/-) mice but did not improve outcomes in Il10(+/+) mice. IL10 genotype also influenced the responsiveness of mice to a TNFA antagonist, etanercept. Fetal loss in Il10(-/-) mice was partly alleviated by moderate or high doses of etanercept, whereas Il10(+/+) mice were refractory to high-dose etanercept, consistent with attenuation by IL10 status of TNFA bioavailability after etanercept treatment. These data show that IL10 modulates resistance to inflammatory stimuli by downregulating expression of proinflammatory cytokines TNFA, IL6, IL1A, and IL12, acting to protect against inflammation-induced pathology in the implantation site.

Immunology of pregnancy: cellular mechanisms allowing fetal survival within the maternal uterus

Pregnancy success remains a fascinating phenomenon to immunologists as it defies the immunological rules of rejection. Although it was previously thought that the maternal immune system does not see the fetus, it is now well documented that fetal cells reach the maternal body and encounter host immune cells. Natural tolerance mechanisms following this interaction remain to be fully elucidated. This article reviews the current literature on mechanisms of adaptive immunity, with emphasis on regulatory T cells and heme oxygenase 1 (HO-1). We propose a scenario in which regulatory T cells create a tolerant microenvironment at the fetal-maternal interface characterised by the presence of tolerance-associated molecules such as HO-1, which has been shown to be of vital importance for fetal survival.

Mechanisms of implantation

Successful embryo implantation in mammals requires the co-ordinated development of a blastocyst competent to implant and an adhesive endometrium. Given the indispensable role of implantation for the furtherance of the species, a number of molecular mechanisms have evolved to regulate the process. A variety of molecules, produced by embryo as well as maternal tissue participates in the cross-talk between the implanting blastocyst and the endometrium. The interplay between the various molecules and the routes in which they are involved is beginning to be elucidated. Because impaired implantation represents the most important limiting factor in the establishment of pregnancy, it is believed that research in the field will allow clinicians to improve the respective rates. This paper reviews certain groups of molecules that are considered to have key roles in the mechanisms of implantation.

hCMV induced IL-6 release in trophoblast and trophoblast like cells

BACKGROUND

Human cytomegalovirus (hCMV) infection of the trophoblasts is a crucial event in virus transmission from mother to child, being one responsible factor for intrauterine infection of the unborn. Differences of virus replication in trophoblasts depending on time point of pregnancy and degree of differentiation of trophoblasts might influence this transmission. Furthermore, immunological reactions of the trophoblasts to hCMV infection might be important defence mechanisms too.

OBJECTIVES

hCMV replication and interleukin-6 release in trophoblasts and trophoblast like cells (choriocarcinoma cells) was investigated.

STUDY DESIGN

Trophoblasts from term and 1st trimester placentas were isolated and infected with hCMV. hCMV production and release to the supernatant as well as interleukin-6 release and interleukin-6 mRNA production by these infected cells was measured. Choriocarcinoma cell lines (JEG-3, JAR) were treated the same. Non-infected trophoblasts were used as controls.

RESULTS

In 1st trimester trophoblast, term trophoblasts and JEG-3 permissive hCMV replication was observed, although with different kinetics and efficiency. In JAR no complete virus replication was seen. High levels of interleukin-6 were measured in the supernatants of all hCMV infected cells immediately after infection. IL-6 mRNA upregulation was seen 48 h after infection in those cell types replication of hCMV occurred (1st trimester trophoblasts, term trophoblasts, JEG-3). At that time-point hCMV immediate early proteins appeared. In JARs no virus production and no IL-6 mRNA upregulation was seen, and IL-6 levels in the supernatant of these hCMV infected cells declined significantly until day 6 after infection compared to mock infected cells.

CONCLUSION

These observations show that hCMV replication is influenced by the degree of trophoblast differentiation. Interleukin-6 is upregulated by hCMV infection, but is independent of complete virus replication.

Uterine and serum cytokine arrays in the mouse during estrus

Cytokines govern uterine immunology and embryo receptivity and are increasingly recognized for their embryotrophic roles. While supplementing culture media with cytokines may improve embryo development/viability in vitro, little is known about their physiological profiles in vivo, and hence which are likely to be uterine immunoregulators and embryotrophins. Therefore, this study profiled 23 cytokines in uterine fluid and serum from individual naturally cycling estrous mice. Samples were analyzed by fluid-phase multiplex immunoassays for interleukin (IL)-1alpha, IL-1beta, IL-2, IL-3, IL-4, IL-5, IL-6, IL-10, IL-12 (p40), IL-12 (p70), IL-13, IL-17, eotaxin, granulocyte-colony stimulating factor (G-CSF), granulocyte macrophage-colony stimulating factor (GM-CSF), interferon (IFN)-gamma, keratinocyte-derived chemokine (KC), monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1alpha MIP)-1beta regulated upon activation, normal T-cell expressed and secreted (RANTES) and tumor necrosis factor (TNF)-alpha. There was a marked divergence in cytokine concentrations between uterine fluid and serum. The former was dominated by G-CSF, eotaxin, KC and IL-1alpha, and had significantly higher levels of IL-1beta, IL-2, IL-3, IL-4, IL-6, IL-9, GM-CSF, MIP-1alpha, MIP-1beta and RANTES. Serum had significantly higher IL-12 (p40), IL-12 (p70), IL-17 and IFN-gamma concentrations. No significant differences in IL-5, IL-10, IL-13, MCP-1 or TNF-alpha profiles were noted. These data indicated a strict compartmentalization of uterine cytokines, with G-CSF as a major cytokine at estrous. Results are discussed with respect to immune cell function, post-coital paternal antigen processing, estrous cyclicity, and endometrial angiogenesis, cell turnover and differentiation.

The role of regulatory T cells in alloantigen tolerance

The diversification mechanism used by the adaptive immune system to maximize the recognition of foreign antigens has the side effect of generating autoreactivity. This effect is counteracted by deletion of cells expressing receptors with high affinity to self (central tolerance) and suppression of autoreactive cells by regulatory T cells (Tregs; peripheral tolerance). This understanding led to the notion that Tregs represent a specialized subset of autoreactive T cells with inhibitory function. The process of generating a diverse repertoire of receptors recognizing antigen presented by major histocompatibility complex (MHC) intrinsically leads to the generation of cells recognizing foreign MHC (alloantigen). The precursor frequency of T cells responding to alloantigen is substantially higher than that responding to any exogenous antigen. The only physiological context in which this becomes a problem is placental viviparity. Although the maternal immune system has no intrinsic mechanism to distinguish between a pathogen and paternally derived fetal alloantigen, it has to neutralize the former and tolerate the latter. We review the function of Tregs from this perspective and propose that they may have evolved to promote tolerance to alloantigen in the context of pregnancy.

Regulatory T cells in pregnancy

Tolerance mechanisms are responsible for the survival of the fetus within the maternal uterus without being attacked by the cells of the maternal immune system despite their direct contact. Regulatory T cells (Treg) were claimed to be important players in the tolerance towards the fetus bearing alloantigens. Recent evidence confirmed an augmentation in the number of Treg during pregnancy and, most importantly, diminished numbers of Treg were associated with immunological rejection of the fetus. This could be prevented by adoptively transferring CD4(+)/CD25(+) Treg cells from normal pregnant mice into abortion-prone animals. Treg prevented abortion while creating a transient tolerant microenvironment characterized by high levels of TGF-beta, LIF, and HO-1. Downregulated levels of Treg were accordingly also reported during human miscarriage. Furthermore, we have evidence suggesting that, to be protective, Treg need to be activated by male antigens during pregnancy.

Hormonal and cytokine regulation of early implantation

Implantation of the blastocyst into the endometrium is a delicately controlled process and a prerequisite for the furtherance of the mammalian species. A complex network of molecules is involved in preparing both the endometrium and blastocyst for a successful interaction. However, the exact molecular steps are poorly understood. Studies so far have shown that disruption of certain pathways results in fertility defects. Impaired implantation is currently considered to be the most important limiting factor for the establishment of viable pregnancies in assisted reproduction. It is expected that elucidating the molecular background of the process will enable accurate diagnosis and effective treatment of infertility.

Potential role of toll-like receptor 3 in a murine model of polyinosinic-polycytidylic acid-induced embryo resorption

OBJECTIVE

To investigate the potential role that toll-like receptor 3 (TLR3) may play in a murine model of polyinosinic-polycytidylic acid (polyIC)-induced embryo resorption.

DESIGN

An animal model-based study on induced embryo resorption.

SETTING

University animal laboratory.

ANIMAL(S)

Pathogen-free animals housed under barrier conditions and monitored for health status. Pregnant BALB/c mouse mated by C57BL/6 male was used as a model of allogeneic gestation.

INTERVENTION(S)

The administration of polyIC was performed to establish a murine model of induced embryo resorption, with or without TLR3 blocking by multiple injection of mAb against this receptor.

MAIN OUTCOME MEASURE(S)

Flow cytometric analysis was performed to detect the percentage of CD45(+)DX5+ and DX5(+)CD69+ cell subsets, with the DX5 antigen used as a common natural killer (NK) cell marker, and CD69 as a marker for activated NK cells, respectively.

RESULT(S)

In the allogeneic mating model, BALB/cxC57BL/6, both the CD45(+)DX5+ and DX5(+)CD69+ cell percentages were significantly elevated upon polyIC stimulation at the absence of anti-TLR3 administration but were kept unchanged if the female mice were pretreated with anti-TLR3 monoclonal antibody. Accordingly, the resorption rate of embryos was boosted by polyIC administration, but this effect could be abrogated by pretreatment of anti-TLR3 mAb.

CONCLUSION(S)

The engagement of polyIC with TLR3 may be critical to the activation of NK cells infiltrated at the feto-maternal interface, subsequently resulting in an increase in embryo resorption.