Distinct pattern of Th17/Treg cells in pregnant women with a history of unexplained recurrent spontaneous abortion

Characterization of Copy-Number Variations and Possible Candidate Genes in Recurrent Pregnancy Losses

It is well established that embryonic chromosomal abnormalities (both in the number of chromosomes and the structure) account for 50% of early pregnancy losses. However, little is known regarding the potential differences in the incidence and distribution of chromosomal abnormalities between patients with sporadic abortion (SA) and recurrent pregnancy loss (RPL), let alone the role of submicroscopic copy-number variations (CNVs) in these cases. The aim of the present study was to systematically evaluate the role of embryonic chromosomal abnormalities and CNVs in the etiology of RPL compared with SA. Over a 3-year period, 1556 fresh products of conception (POCs) from miscarriage specimens were investigated using single nucleotide polymorphism array (SNP-array) and CNV sequencing (CNV-seq) in this study, along with further functional enrichment analysis. Chromosomal abnormalities were identified in 57.52% (895/1556) of all cases. Comparisons of the incidence and distributions of chromosomal abnormalities within the SA group and RPL group and within the different age groups were performed. Moreover, 346 CNVs in 173 cases were identified, including 272 duplications, 2 deletions and 72 duplications along with deletions. Duplications in 16q24.3 and 16p13.3 were significantly more frequent in RPL cases, and thereby considered to be associated with RPL. There were 213 genes and 131 signaling pathways identified as potential RPL candidate genes and signaling pathways, respectively, which were centered primarily on six functional categories. The results of the present study may improve our understanding of the etiologies of RPL and assist in the establishment of a population-based diagnostic panel of genetic markers for screening RPL amongst Chinese women.

Immune Tolerance of the Human Decidua

The endometrium is necessary for implantation, complete development of the placenta, and a successful pregnancy. The endometrium undergoes repeated cycles of proliferation, decidualization (differentiation), and shedding during each menstrual cycle. The endometrium—including stromal, epithelial, vascular endothelial, and immune cells—is both functionally and morphologically altered in response to progesterone, causing changes in the number and types of immune cells. Immune cells make up half of the total number of endometrial cells during implantation and menstruation. Surprisingly, immune tolerant cells in the endometrium (uterine natural killer cells, T cells, and macrophages) have two conflicting functions: to protect the body by eliminating pathogenic microorganisms and other pathogens and to foster immunological change to tolerate the embryo during pregnancy. One of the key molecules involved in this control is the cytokine interleukin-15 (IL-15), which is secreted by endometrial stromal cells. Recently, it has been reported that IL-15 is directly regulated by the transcription factor heart- and neural crest derivatives-expressed protein 2 in endometrial stromal cells. In this review, we outline the significance of the endometrium and immune cell population during menstruation and early pregnancy and describe the factors involved in immune tolerance and their involvement in the establishment and maintenance of pregnancy.

Level of Foxp3, DNMTs, methylation of Foxp3 promoter region, and CD4 + CD25 + CD127low regulatory T cells in vulvar lichen sclerosus

This study is to investigate the pathogenesis of vulvar lichen sclerosus (VLS) by analyzing the level of Foxp3, DNMTs, methylation of Foxp3 promoter region, and CD4 + CD25 + CD127low Regulatory T cells (Tregs). This study enrolled 15 VLS patients and 25 controls. Lesional and extralesional vulvar skin tissues, normal vulvar skin tissues and peripheral blood were collected. Compared with the control group, Foxp3 protein in the lesional and extralesional skin of VLS group was significantly reduced. The levels of DNMT1 and DNMT3b proteins in lesional skin of VLS group were significantly increased. There was no difference in the total methylation rates of the promoter region of the Foxp3 gene. The methylation rates of CpG1, CpG4, CpG9, and CpG10 were significantly higher in lesional skin of VLS group than in control group. There was no correlation between the total methylation rates of 10 CpG sites and the level of Foxp3 and DNMT1 proteins; there was a positive correlation between Foxp3 and DNMT1 protein in lesional skin of VLS group (r = 0.675, p < 0.05), and a negative correlation (r = -0.665, p < 0.05) in extralesional skin of VLS group. However, there was no correlation of Foxp3 with DNMT3b. The number of CD4 + CD25 + CD127low Tregs VLS decreased significantly. The expression of Foxp3 protein and the quantity of CD4 + CD25 + CD127low Tregs in patients with VLS decreased, which may cause local or systemic abnormal immunosuppression of Tregs, leading to the occurrence of VLS. This may be related with methylation or DNMT1, which needs further verification.

The imbalance of the Th17/Treg axis following equine ascending placental infection

Ascending placentitis is a leading cause of abortion in the horse, but adaptive immune response to this disease is unknown. To evaluate this, sub-acute placentitis was experimentally-induced via trans-cervical inoculation of S. zooepidemicus, and endometrium and chorioallantois was collected 8 days later (n = 6 inoculated/n = 6 control). The expression of transcripts relating to Th1, Th2, Th17, and Treg maturation was assessed via RNASeq. IHC of transcription factors relating to each subtype in the same tissues (Th1: TBX21, Th2: GATA3, Th17: IRF4, Treg: FOXp3). An immunoassay was utilized to assess circulating cytokines (Th1: IFNg, IL-2; Th2: IL-4, IL-5; Th17: IL-17, IL-6; Treg: IL-10, GM-CSF). An increase in Th1 and Th17-related transcripts were noted in the chorioallantois, although no alterations were seen in the endometrium. Th2 and Treg-related transcripts altered in a dysregulated manner, as some transcripts increased in expression while others decreased. Immunolocalization of Th1, Th2, and Th17 cells was increased in diseased chorioallantois, while no Treg cells were noted in the diseased tissue. Secreted cytokines relating to Th1 (IFNg, IL-2), Th17 (IL-6), Th2 (IL-5), and Treg (IL-10) populations increased in maternal circulation eight days after inoculation. In conclusion, the Th1/Th17 response to ascending placentitis occurs primarily in the chorioallantois, indicating the adaptive immune response to occur in fetal derived placental tissue. Additionally, ascending placentitis leads to an increase in the helper T cell populations (Th1/Th17/Th2) while decreasing the Treg response. This increase in Th17-related responses alongside a diminishing Treg-related response may precede or contribute to fetal demise, abortion, or preterm labor.

Application of Ligilactobacillus salivarius CECT5713 to Achieve Term Pregnancies in Women with Repetitive Abortion or Infertility of Unknown Origin by Microbiological and Immunological Modulation of the Vaginal Ecosystem

In this study, the cervicovaginal environment of women with reproductive failure (repetitive abortion, infertility of unknown origin) was assessed and compared to that of healthy fertile women. Subsequently, the ability of Ligilactobacillus salivarius CECT5713 to increase pregnancy rates in women with reproductive failure was evaluated. Vaginal pH and Nugent score were higher in women with reproductive failure than in fertile women. The opposite was observed regarding the immune factors TGF-β 1, TFG-β 2, and VEFG. Lactobacilli were detected at a higher frequency and concentration in fertile women than in women with repetitive abortion or infertility. The metataxonomic study revealed that vaginal samples from fertile women were characterized by the high abundance of Lactobacillus sequences, while DNA from this genus was practically absent in one third of samples from women with reproductive failure. Daily oral administration of L. salivarius CECT5713 (~9 log₁₀ CFU/day) to women with reproductive failure for a maximum of 6 months resulted in an overall successful pregnancy rate of 56%. The probiotic intervention modified key microbiological, biochemical, and immunological parameters in women who got pregnant. In conclusion, L. salivarius CECT5713 has proved to be a good candidate to improve reproductive success in women with reproductive failure.

Mifepristone regulates Tregs function mediated by dendritic cells through suppressing the expression of TGF-β

BACKGROUND

Previous studies have demonstrated that mifepristone in the daily low-dose affects the function of endometrium. These researches also implied an alteration of endometrium immune balance, which might be involved in regulating endometrial function. However, the detailed mechanisms remain to be further explored.

METHODS

In this study, the expressions of CD80, CD86, and ICAM-1 in dendritic cells (DCs), which were stimulated with different concentrations of mifepristone (20, 65, and 200 nM), were detected by FACS. After that, we further evaluated the expression of Forkhead box P3 (FOXP3) and IL-10 in Tregs, which co-cultured with mifepristone treated DCs. In mechanism, we compared the indoleamine 2,3-dioxygenase (IDO) and TGF-β expression with enzyme-linked immunosorbent assay (ELISA).

RESULTS

The results indicated that mifepristone promoted the expressions of CD80, CD86, and ICAM-1 in a dosage dependent manner. Reversely, FOXP3 and IL-10 expression levels in Tregs co-cultured with mifepristone-treated DCs were significantly decreased compared with those co-cultured with nontreated DC. Furthermore, a significant reduce in IDO and TGF-β expression was observed in DCs treated with mifepristone. By using the IDO inhibitor (1-methyl tryptophan, 1-MT) or TGF-b supplement, we confirmed that TGF-β, but not IDO could rescue the downregulation of FOXP3 and IL-10 in Tregs co-cultured with mifepristone treated DCs. All of these results suggest that mifepristone may regulate DC function by decreasing TGF-β expression, which further results in the downregulations of FOXP3 and IL-10 in Tregs.

CONCLUSION

Therefore, our research provides a theoretical basis for a potentially clinical application of mifepristone as a novel contraceptive.

Elevated Neurokinin-1 Receptor Expression in Uterine Products of Conception Is Associated With First Trimester Miscarriages

Background

Miscarriage is a common complication of early pregnancy, mostly occurring in the first trimester. However, the etiological factors and prognostic and diagnostic biomarkers are not well known. Neurokinin-1 receptor (NK-1R) is a receptor of tachykinin peptide substance P (SP) and has a role in various pathological conditions, cancers, but its association with miscarriages and significance as a clinicopathological parameter are not studied. Accordingly, the present study aimed to clarify the localization and expression for NK-1R in human retained products of conception (POC). The role of NK-1R is not known in miscarriages.

Materials and Methods

NK-1R expression was assessed in POC and normal placental tissues by immunohistochemistry. Three- to four-micrometer-thin sections of formalin-fixed paraffin-embedded tissues were used for this purpose. Tissues were processed and then immunohistochemically stained with NK-1R antibody. Brain tissue was used as control for antibody. Protein expression was evaluated using the nuclear labeling index (%). Tissues were counterstained with 3,3'-diaminobenzidine (DAB), and microscopy was performed at 10×, 20×, and 40× magnifications.

Results

Ten human POC tissues and 10 normal placental tissues were studied by immunohistochemistry to demonstrate the localization of NK-1R. The expression of NK-1R protein was high in all the cases of both groups. NK-1R expression showed no notable differences among different cases of miscarriages as well as normal deliveries at full term regardless of the mother's age and gestational age at which the event occurred. Statistically, no difference was found in both groups, which is in agreement with our hypothesis and previous findings.

Conclusion

The expression of NK-1R was similar in all the cases, and it was intense. It shows that dysregulation of NK-1R along with its ligand SP might be involved in miscarriages and also involved in normal delivery. Our results provide fundamental data regarding this anti-NK-1R strategy. Thus, the present study recommends that SP/NK-1R system might, therefore, be considered as an emerging and promising diagnostic and therapeutic strategy against miscarriages. Hence, we report for the first time the expression and localization of NK-1R in POC. We suggest NK-1R antagonist in addition to the immunoglobulins and human chorionic gonadotropin to diagnose and treat spontaneous miscarriages.

Significance of the ratio interferon-γ/interleukin-4 in early diagnosis and immune mechanism of unexplained recurrent spontaneous abortion

OBJECTIVE

To investigate the significance of T helper type 1 (Th1)/Th2 cytokines in the pathogenesis of unexplained recurrent spontaneous abortion (URSA), and reveal the value of single cytokines and their proportions in early diagnosis.

METHODS

A total of 44 URSA patients (URSA group), 51 patients with adverse pregnancy history (ad-pregnancy group), and 42 healthy volunteers with normal pregnancy (pregnancy group) were recruited for a cross-sectional study from July 2018 to April 2019 in the Second Xiangya Hospital. Pregnancies involving chromosomal abnormalities, infection, autoimmune diseases, and anatomical abnormalities were excluded. Flow cytometry was used to determine the level of Th1/Th2 cytokines in peripheral blood.

RESULTS

The level of interleukin-6 (IL-6) in the peripheral blood of the ad-pregnancy group was significantly higher than in the other two groups. The ratio of interferon-γ (IFN-γ)/IL-4 in the URSA group was significantly higher than that of the pregnancy group. The area under the curve for IFN-γ/IL-4 was 0.821, with high diagnostic efficiency, and sensitivity as high as 84.09%.

CONCLUSION

Laboratory testing for IL-6 is not recommended for the diagnosis or monitoring of URSA. The variable IFN-γ/IL-4 can be used for the initial diagnosis of URSA to reduce the rate of missed diagnosis. This ratio was more important than the expression of a single cytokine in the Th1/Th2 immune response.

Notch1 is crucial for decidualization and maintaining the first pregnancy in the mouse†

The endometrium undergoes a pregnancy-delivery-repair cycle multiple times during the reproductive lifespan in females. Decidualization is one of the critical events for the success of this essential process. We have previously reported that Notch1 is essential for artificial decidualization in mice. However, in a natural pregnancy, the deletion of Notch1 (PgrCre/+Notch1f/f, or Notch1d/d) only affects female fertility in the first 30 days of a 6-month fertility test, but not the later stages. In the present study, we undertook a closer evaluation at the first pregnancy of these mice to attempt to understand this puzzling phenomenon. We observed a large number of pregnancy losses in Notch1d/d mice in their first pregnancy, which led to the subfertility observed in the first 30 days of the fertility test. We then demonstrated that the initial pregnancy loss is a consequence of impaired decidualization. Furthermore, we identified a group of genes that contribute to Notch1 regulated decidualization in a natural pregnancy. Gene ontogeny analysis showed that these differentially expressed genes in the natural pregnancy are involved in cell-cell and cell-matrix interactions, different from genes that have been previously identified from the artificial decidualization model, which contribute to cell proliferation and apoptosis. In summary, we determined that Notch1 is essential for normal decidualization in the mouse uterus only in the first pregnancy but not in subsequent ones.

Adoptive transfer of Tregs: A novel strategy for cell-based immunotherapy in spontaneous abortion: Lessons from experimental models

Since half of the genes are inherited from the paternal side, the maternal immune system has to tolerate the presence of foreign paternal antigens. Regulatory T cells facilitate the development and maintenance of peripheral tissue tolerance of the fetus during pregnancy. Reduction in regulatory T cells is associated with complications of pregnancy, including spontaneous abortion. Recent studies in mouse models have shown that the adoptive transfer of Tregs can prevent spontaneous abortion in mouse models through improving maternal tolerance. Thus, adoptive cell therapy using autologous Tregs could potentially be a novel therapeutic approach for cell-based immunotherapy in women with unexplained spontaneous abortion. Besides, strategies for activating and expanding antigen-specific Tregs ex vivo and in vivo based on pharmacological agents can pave the foundation for an approach incorporating immunotherapy and pharmacotherapy. This review aims to elaborate on the current understanding of the therapeutic potential of the adoptive transfer of Tregs in the treatment of spontaneous abortion disease.

Alteration in endometrial helper T-cell subgroups in chronic endometritis

PROBLEM

The effect of chronic endometritis (CE) on the subpopulation of CD4⁺ T cells, Th1, Th2, Th17, and regulatory T cells in the endometrium is unknown.

METHOD OF STUDY

Lymphocytes were isolated from the endometrium of CE patients (n = 12) and non-CE patients (n = 7). The CD4⁺ T-cell profile was analyzed by flow cytometry and immunofluorescence.

RESULTS

In the endometrium of CE patients, there were significantly more Th1 cells among CD4⁺ cells and fewer Th2 cells in comparison to non-CE patients. No marked difference was observed in Th17 cells or Foxp3⁺ Treg cells. Moreover, the proportion of Th1 cells increased and the proportion of Th2 cells decreased as the number of CD138⁺ cells increased. Furthermore, when the localization of CD138⁺ cells and CD4⁺ cells was examined, CD4⁺ cells were found to be clustered around CD138⁺ cells in CE patients.

CONCLUSION

The CD4⁺ T-cell profile in the endometrium is altered in women with CE. This finding may help to clarify the pathophysiology and development of treatment methods for CE.

Cytokine imbalance at materno-embryonic interface as a potential immune mechanism for recurrent pregnancy loss

Recurrent pregnancy loss (RPL) is a prominent reproductive disease that distresses about 2%-5% of couples. RPL is the loss of two or more successive spontaneous pregnancies prior to the 20th week of embryo development. The commencement of pregnancy necessitates implantation of the embryo into responsive maternal decidua synchronized with the process of placentation, decidual and myometrial trophoblast incursion as well as refashioning of spiral blood arteries of uterus. The collapse of any of the processes fundamental for pregnancy success may result into an array of pregnancy problems including spontaneous pregnancy loss. Endometrium of human female manufactures an extensive range of cytokines during the proliferative and secretory stage of the menstrual cycle. These endometrial cytokines are thought as major players for making the uterus ready for embryo implantation and placental development during pregnancy. Decidual cytokines regulate the invasion of trophoblast and remodeling of spiral arteries as well as take part in immune suppression to accomplish the pregnancy. Deterrence of maternal rejection of embryo needs a regulated milieu, which takes place essentially at the embryo-maternal interface and the tissues of the uterus. The reasons of RPL remain anonymous in a large number of cases that lead to difficulties in management and severe trauma in couples. Cytokine modulatory therapies have been shown promising for preventing RPL. Further study of novel factors is wanted to establish more effective RPL treatment protocols. The present study aims to review the outcome of cytokine breach at materno-embryonic interface and the efficacy of cytokine modulatory therapies in RPL.

BuShen HuoXue Decoction Promotes Decidual Stromal Cell Proliferation via the PI3K/AKT Pathway in Unexplained Recurrent Spontaneous Abortion

BuShen HuoXue decoction (BSHXD) has been used to treat patients with unexplained recurrent spontaneous abortion (URSA). However, the chemical compounds and mechanism by which BSHXD exerts its therapeutic and systemic effects to promote the proliferation of decidual stromal cells (DSCs) has not been elucidated. This work sought to elucidate the cellular and molecular mechanism of BSHXD in terms of inflammatory factors IL-17A in DSCs in vitro because of the critical roles of inflammation, apoptosis, and immunity in the development and progression of pregnancy loss. Twelve migratory chemical compounds from BSHXD extract were qualitatively analyzed by high-performance liquid chromatography (HPLC). DSCs were collected from normal early pregnancy (NEP) and URSA to determine whether BSHXD affects IL-17A/IL17RA via the PI3K/AKT pathway. Abnormal apoptosis and activated p-AKT were observed in URSA DSCs. RhIL-17 A, LY294002 (a PI3K pathway inhibitor), and BSHXD were individually or simultaneously administered in NEP DSCs, suggesting that BSHXD restored cell proliferation without excessive stimulation and IL-17A promotes proliferation via the PI3K/AKT pathway. Using the same intervention in URSA DSCs, qRT-PCR measured the upregulated mRNA levels of IL-17 A/IL-17RA, PI3K, AKT, p-AKT, PTEN, Bcl-2, and Bcl-xL and downregulated mRNA levels of BAD and ACT1 after treatment with BSHXD. We demonstrated that BSHXD affected IL-17A/IL-17R via PI3K/AKT pathway to promote the proliferative activity of DSCs in URSA. These results provide a new insight to further clarify the relationship between inflammation and apoptosis and the mechanism of imbalance in the dynamic equilibrium between Th17/Treg immune cells at the maternal-fetal interface.

Association of bisphenol A or bisphenol S exposure with oxidative stress and immune disturbance among unexplained recurrent spontaneous abortion women

Human exposure to environmental chemicals might play a role in the pathogenesis of unexplained recurrent spontaneous abortion (URSA). Bisphenol A (BPA) and bisphenol S (BPS) have been suggested to affect reproductive health. However, the mechanism remains unclear. To explore the association between BPA and BPS exposure and oxidative stress and immune homeostasis, we conducted a cross-sectional study and revealed BPA and BPS levels in relation to these two factors which were supposed to be implicated in miscarriage. 111 URSA patients were recruited and we analyzed urinary BPA and BPS concentrations, oxidative stress biomarkers (8-hydroxydeoxyguanosine and 8-isoprostane) and serum immune balance biomarkers (IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p70, IL-13, TNF-α, TGF-β and IFN-γ). Multivariable linear regression models were used to evaluate the correlation between bisphenols exposure and outcome biomarkers. After adjustment for age, BMI, menstrual cycle, and parity history, creatinine-adjusted BPA was significantly associated with increases in 8-isoprostane (β = 0.74, 95% CI = 0.07, 1.41; p = 0.031) and IFN-γ (β = 0.18, 95% CI = 0.00, 0.36; p = 0.046). No statistical correlation between BPS and biomarkers of oxidative stress or immune balance was observed when all participants were analyzed. Further analysis revealed that in the subgroup of BPS > limit of detection (0.01 ng/ml), creatinine-adjusted BPS was significantly associated with increases in IL-10 (β = 0.22, 95% CI = 0.00, 0.45; p = 0.048). Our findings suggested that BPA and BPS exposure might be related to oxidative stress and immune imbalance in URSA patients. Overall, our work might suggest potential pathogenic and aetiological associations among the bisphenols, biomarkers and URSA, which offers hypotheses for further studies.

circ-ZUFSP regulates trophoblasts migration and invasion through sponging miR-203 to regulate STOX1 expression

Recurrent spontaneous abortion (RSA), defined as two or more consecutive pregnancy losses before 12 weeks of gestation with or without previous live births. Circular RNAs (circRNAs) are a novel class of endogenous noncoding RNAs that play important roles in gene expression regulation and trophoblasts function during embryo development. This study aimed to evaluate the function mechanism of circRNAs regulating trophoblasts function in the occurrence and progression RSA. Through overexpression and down-regulation of circ-ZUFSP, we investigated the effect of circ-ZUFSP on the function of trophoblasts and found loss of circ-ZUFSP suppressed trophoblasts migration and invasion in vitro. Moreover, loss of circ-ZUFSP regulated trophoblasts migration and invasion via regulation of miR-203. Furthermore, STOX1 was revealed to a target of miR-203, and down-regulation of STOX1 reversed circ-ZUFSP enhanced cell invasion, suggesting that circ-ZUFSP might regulate STOX1 expression through sponging miR-203 in HTR-8/SVneo cells. In addition, low expression of circ-ZUFSP, STOX1 and high expression of miR-203 were testified in placental tissues of RSA mice. Our study demonstrated a molecular mechanism of circ-ZUFSP regulating trophoblasts migration and invasion, which might provide a novel indicator for early diagnosis and potential treatment of RSA.

Functional significance of lymphocytes in pregnancy and lymphocyte immunotherapy in infertility: A comprehensive review and update

During pregnancy, the fetal-maternal interface underlies several dynamic alterations to permit the fetus to be cultivated and developed in the uterus, in spite of being identifies by the maternal immune system. A large variety of decidual leukocyte populations, including natural killer cells, NKT cells, innate lymphoid cells, dendritic cells, B cells, T cells, subpopulations of helper T cells play a vital role in controlling the trophoblast invasion, angiogenesis as well as vascular remodeling. In contrast, several regulatory immunosuppressive mechanisms, including regulatory T cells, regulatory B cells, several cytokines and mediators are involved in maintain the homeostasis of immune system in the fetal-maternal interface. Nonetheless, aberrant alterations in the balance of immune inflammatory or immunosuppressive arms have been associated with various pregnancy losses and infertilities. As a result, numerous strategies have been developed to revers dysregulated balance of immune players to increase the chance of successful pregnancy. Lymphocyte immunotherapy has been developed through utilization of peripheral white blood cells of the husband or others and administered into the mother to confer an immune tolerance for embryo's antigens. However, the results have not always been promising, implying to further investigations to improve the approach. This review attempts to clarify the involvement of lymphocytes in contributing to the pregnancy outcome and the potential of lymphocyte immunotherapy in treatment of infertilities with dysregulated immune system basis.

Role of Regulatory T Cells in Regulating Fetal-Maternal Immune Tolerance in Healthy Pregnancies and Reproductive Diseases

Regulatory T cells (Tregs) are a specialized subset of T lymphocytes that function as suppressive immune cells and inhibit various elements of immune response in vitro and in vivo. While there are constraints on the number or function of Tregs which can be exploited to evoke an effective anti-tumor response, sufficient expansion of Tregs is essential for successful organ transplantation and for promoting tolerance of self and foreign antigens. The immune-suppressive property of Tregs equips this T lymphocyte subpopulation with a pivotal role in the establishment and maintenance of maternal tolerance to fetal alloantigens, which is necessary for successful pregnancy. Elevation in the level of pregnancy-related hormones including estrogen, progesterone and human chorionic gonadotropin promotes the recruitment and expansion of Tregs, directly implicating these cells in the regulation of fetal-maternal immune tolerance. Current studies have provided evidence that a defect in the number or function of Tregs contributes to the etiology of several reproductive diseases, such as recurrent spontaneous abortion, endometriosis, and pre-eclampsia. In this review, we provide insight into the underlying mechanism through which Tregs contribute to pregnancy-related immune tolerance and demonstrate the association between deficiencies in Tregs and the development of reproductive diseases.

Pregnancy immune tolerance at the maternal-fetal interface

Pregnancy is a natural process that poses an immunological challenge because non-self fetus must be accepted. During the pregnancy period, the fetus as 'allograft' inherits maternal and also paternal antigens. For successful and term pregnancy, the fetus is tolerated and nurtured enjoying immune privileges that minimize the risk of being rejected by maternal immune system. Multiple mechanisms contribute to tolerate the semi-allogeneic fetus. Here, we summarize the recent progresses on how the maternal immune system actively collaborates to maintain the immune balance and maternal-fetal tolerance.

Reduced frequency and functional defects of CD4+CD25highCD127low/- regulatory T cells in patients with unexplained recurrent spontaneous abortion

BACKGROUND

Unexplained recurrent spontaneous abortion (URSA) is defined as two or more consecutive pregnancy losses, generally of unknown cause; it is related to a failure of fetal-maternal immunological tolerance. Regulatory T cells (Tregs) exert immunosuppressive effects, which are essential to maintain fetal-maternal immunological tolerance and regulate immune balance. In this study, we used the specific cell-surface phenotype of CD4⁺CD25^highCD127^low/- Tregs to investigate the number and suppressive function of Tregs isolated from the peripheral blood of patients with URSA with the aim of expanding our understanding of their role in URSA.

METHODS

We isolated a relatively pure population of peripheral CD4⁺CD25^highCD127^low/- Tregs and CD4⁺CD25^- responder T cells (Tresps) from the patients with URSA and normal fertile nonpregnant control women via fluorescence-activated cell sorting. We compared the frequency, suppressive capacity, and forkhead box transcription factor P3 (FOXP3) expression of Tregs in the peripheral blood between patients with URSA and normal controls.

RESULTS

The frequency of CD4⁺CD25^highCD127^low/- Tregs in the peripheral blood was lower in URSA patients than in the controls (P < 0.05). The mean fluorescence intensity of FOXP3 and FOXP3 mRNA expression in Tregs was also significantly lower in the URSA patients (P < 0.01). Tregs suppressed the activity of autologous Tresps stimulated with anti-CD3/CD28 beads in a concentration-dependent manner, with the strongest suppression occurring in cocultures with a 1:1 Treg:Tresp ratio in both groups; however, patient-derived Tregs exhibited a poorer capacity to suppress the proliferation of autologous Tresps than the Tregs from normal controls (P < 0.01). Moreover, Tregs isolated from URSA patients inhibited the proliferation of Tresps from normal controls less potently than the Tregs from normal controls (P < 0.01), and Tresps from URSA patients were less effectively suppressed by autologous Tregs than by those from normal controls (P < 0.01). Tresp activity were intact in both groups.

CONCLUSIONS

We observed a lower frequency of peripheral CD4⁺CD25^highCD127^low/- Tregs with lower FOXP3 expression in the peripheral blood of URSA patients. In addition, highly purified Tregs from patients with URSA exhibited impaired suppressive effects. The defect in immune regulation in URSA patients appears to be primarily related to impaired Tregs, and not to increased resistance of Tresps to suppression. Our findings reveal a potential novel therapeutic target for URSA.

Placental endovascular extravillous trophoblasts (enEVTs) educate maternal T-cell differentiation along the maternal-placental circulation

Objectives

During human pregnancy, the endothelial cells of the uterine spiral arteries (SPA) are extensively replaced by a subtype of placental trophoblasts, endovascular extravillous trophoblasts (enEVTs), thus establishing a placental‐maternal circulation. On this pathway, foetus‐derived placental villi and enEVTs bath into the maternal blood that perfuses along SPA being not attacked by the maternal lymphocytes. We aimed to reveal the underlying mechanism of such immune tolerance.

Methods

In situ hybridization, immunofluorescence, ELISA and FCM assay were performed to examine TGF‐β1 expression and distribution of regulatory T cells (Tregs) along the placental‐maternal circulation route. The primary enEVTs, interstitial extravillous trophoblasts (iEVTs) and decidual endothelial cells (dECs) were purified by FACS, and their conditioned media were collected to treat naïve CD4⁺ T cells. Treg differentiation was measured by FLOW and CFSE assays.

Results

We found that enEVTs but not iEVTs or dECs actively produced TGF‐β1. The primary enEVTs significantly promoted naïve CD4⁺ T‐cell differentiation into immunosuppressive FOXP3⁺ Tregs, and this effect was dependent on TGF‐β1. In recurrent spontaneous abortion (RSA) patients, an evidently reduced proportion of TGF‐β1–producing enEVTs and their ability to educate Tregs differentiation were observed.

Conclusions

Our findings demonstrate a unique immune‐regulatory characteristic of placental enEVTs to develop immune tolerance along the placental‐maternal circulation. New insights into the pathogenesis of RSA are also suggested.

Analysis of chromosomes and the T helper 17 and regulatory T cell balance in patients with recurrent spontaneous abortion

The present study investigated the genetic etiology and possible immunological pathogenesis of recurrent spontaneous abortion by analyzing chromosome abnormalities, and the balance between T helper 17 (Th17) and regulatory T (Treg) cells. A total of 54 patients with recurrent spontaneous abortion were selected. The villus and decidual tissues, and peripheral venous blood were collected from each patient. Villus chromosome analysis was performed by high-throughput gene sequencing. Flow cytometry was used to detect Th17 and Treg cells in patients without chromosome abnormalities (n=30) and the control group (normal pregnancy; n=32). Immunoglobulin (IG) combined with human chorionic gonadotropin hormone (HCG) treatment was given to patients without chromosome abnormalities (n=30). Changes in the expression levels of Th17 and Treg cells before and after treatment were compared with patients with successful pregnancy (n=18). Before treatment, compared with the control group, the proportion of Th17 cells in peripheral blood and decidual tissue was increased and the proportion of Treg cells decreased. After treatment, compared with patients before treatment, the proportion of Th17 cells decreased and Treg cells increased, and the Th17 and Treg cells balance was reversed with a biased towards Treg cells. The present results suggested that the Th17 and Treg cell immune imbalance may be an important immune factor in recurrent spontaneous abortion. IG combined with HCG therapy may improve pregnancy outcomes by reversing the imbalance between Th17 and Treg cells.

Destruction in maternal-fetal interface of URSA patients via the increase of the HMGB1-RAGE/TLR2/TLR4-NF-κB signaling pathway

AIMS

HMGB1 has been reported to play a crucial role in the physiological and pathophysiological responses during pregnancy. However, it is still unknown whether excessively expressed HMGB1 at the maternal-fetal interface related to Unexplained Recurrent Spontaneous Abortion (URSA). This study was designed to investigate the local capability of HMGB1 in the pathology of URSA, determined the distributions and characteristics of HMGB1, its receptors (RAGE/TLR2/TLR4) and important signaling molecule NF-κB p65 expression at the maternal-fetal interface，as well as compared the differences of HMGB1 expression between the URSA group, control group and aspirin treatment group.

MATERIAL AND METHODS

H&E staining, Western blot analysis, immunofluorescence assay and immunohistochemical staining were applied to determine the effect of HMGB1 and its receptors at the maternal-fetal interface. ELISA was utilized to detect the concentration of HMGB1 in plasma.

KEY FINDINGS

Our study demonstrated that the activation of the HMGB1-RAGE/TLR2/TLR4-NF-κB pathway at the maternal-fetal interface may have occurred in the URSA group. HMGB1 concentration in plasma was higher in the URSA group than the control group. Furthermore, the levels of HMGB1 of subjects with URSA could be reduced by administrating low doses of aspirin (ASPL).

SIGNIFICANCE

This is the first report indicating the roles of HMGB1 at the maternal-fetal interface of URSA patients and broadening the horizons for clinical treatment of URSA. HMGB1-RAGE/TLR2/TLR4-NF-κB signaling pathway may be activated at the maternal-fetal interface in URSA and account for its pathogenesis. HMGB1 have the potential to be promising biomarkers in prevention and therapy of URSA.

The immune system and microbiome in pregnancy

Hormonal changes during pregnancy instigate numerous physiological changes aimed at the growth and delivery of a healthy baby. A careful balance between immunological tolerance against fetal antigens and immunity against infectious agents needs to be maintained. A three-way interaction between pregnancy hormones, the immune system and our microbiota is now emerging. Recent evidence suggests that microbial alterations seen during pregnancy may help maintain homeostasis and aid the required physiological changes occurring in pregnancy. However, these same immunological and microbial alterations may also make women more vulnerable during pregnancy and the post-partum period, especially regarding immunological and infectious diseases. Thus, a further understanding of the host-microbial interactions taking place during pregnancy may improve identification of populations at risk for adverse pregnancy outcomes.

Evaluation of T cell cytokines and their role in recurrent miscarriage

Recurrent miscarriage (RM) is defined as two or more consecutive pregnancy losses that affect approximately 5% of conceived women worldwide. RM is a multi-factorial reproductive problem and has been associated with parental chromosomal abnormalities, embryonic chromosomal rearrangements, uterine anomalies, autoimmune disorders, endocrine dysfunction, thrombophilia, life style factors, and maternal infections. However, the exact cause is still undecided in remaining 50% of cases. Immunological rejection of the embryo due to exacerbated maternal immune reaction against paternal embryonic antigens has been set forth as one of the significant reason for RM. The accurate means that shield the embryo during normal pregnancy from the attack of maternal immune network and dismissal are inadequately implicit. However, it is suggested that the genetically irreconcilable embryo escapes maternal immune rejection due to communication among many vital cytokines exuded at maternal-embryonic interface both by maternal and embryonic cells. Previous investigations suggested the Th1/Th2 dominance in altered immunity of RM patients, according to which the allogenic embryo flees maternal T cell reaction by inclining the Th0 differentiation toward Th2 pathway resulting into diminished pro-inflammatory Th1 immunity. However, recently pro-inflammatory Th17 cells and immunoregulatory Treg cells have been discovered as essential immune players in RM besides Th1/Th2 components. Cytokines are believed to develop a complicated regulatory network so as to establish a state of homeostasis between the semi-allogenic embryo and the maternal immune system. However, an adverse imbalance among cytokines at maternal-embryonic interface perhaps due to their gene polymorphisms may render immunoregulatory means not enough to re-establish homeostasis and thus may collapse pregnancy.

NK cell subsets in idiopathic recurrent miscarriage and renal transplant patients

The present review article compares NK cell subsets and cytokine patterns determined in the peripheral blood as well as results of functional in-vitro assays using peripheral NK cells of idiopathic recurrent miscarriage (iRM) patients with corresponding results obtained in female healthy controls and female renal transplant recipients with good long-term graft function. Immune mechanisms, inducing transplant rejection in long-term transplant recipients might also be able to induce rejection of semi-allogeneic fetal cells in patients with iRM. Consequently, the immune status of transplant recipients with good stable long-term graft function should be different from the immune status of iRM patients. iRM patients show a strong persistent cytotoxic NK cell response in the periphery. Simultaneously, immunostimulatory Th1 as well as immunosuppressive Th2 type lymphocytes in the blood are strongly activated but plasma levels of immunosuppressive Th2 type cytokines are abnormally low. In-vitro, unstimulated NK cell cultures of iRM patients show a strong spontaneous TGF-ß1 release in the supernatant but lower TGF-ß1 levels after stimulation with tumor cell line K562, suggesting strong consumption of TGF-ß1 by pre-activated NK cells of iRM patients that might contribute to the low systemic Th2 type plasma levels. iRM patients do not show a systemic switch to a Th2 type cytokine pattern and one might hypothesize that low TGF-ß plasma levels indicate low TGF-ß levels in the micromilieu immediately before fetal rejection. Persistent TGF-ß deficiency implies a persistent unfavorable micromilieu for pregnancy resulting in failing tolerance induction due to lack of TGF-ß, a condition that might contribute to iRM.

Endometrial Immune Dysfunction in Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL) represents an unresolved problem for contemporary gynecology and obstetrics. In fact, it is not only a relevant complication of pregnancy, but is also a significant reproductive disorder affecting around 5% of couples desiring a child. The current knowledge on RPL is largely incomplete, since nearly 50% of RPL cases are still classified as unexplained. Emerging evidence indicates that the endometrium is a key tissue involved in the correct immunologic dialogue between the mother and the conceptus, which is a condition essential for the proper establishment and maintenance of a successful pregnancy. The immunologic events occurring at the maternal-fetal interface within the endometrium in early pregnancy are extremely complex and involve a large array of immune cells and molecules with immunoregulatory properties. A growing body of experimental studies suggests that endometrial immune dysregulation could be responsible for several, if not many, cases of RPL of unknown origin. The present article reviews the major immunologic pathways, cells, and molecular determinants involved in the endometrial dysfunction observed with specific application to RPL.

Biomarkers in Fetomaternal Tolerance

Multiple mechanisms of tolerance operate in the immune cross-talk at the fetomaternal interface, contributing to successful pregnancy outcome. The cross-talk includes interaction between various cell subsets and between cytokines and molecules of the endocrine system. A depiction of how all these components interact with each other and contribute to tolerance of the fetus is not clearly understood. Dysregulation in one or more of these mechanisms leads to fetal loss. Few effective biomarkers are available that can safely predict fetal loss. This review discusses some potential biomarkers that can predict failure of tolerance at the fetomaternal interface.