Natural killer, natural killer T, helper and cytotoxic T cells in the decidua from recurrent spontaneous abortion with normal and abnormal chromosome karyotypes

Molecular mechanism of aberrant decidualization in adenomyosis leading to reduced endometrial receptivity

Patients with adenomyosis not only experience a decrease in quality of life as a result of dysmenorrhea and severe monthly flow but they are also rendered infertile. Pregnancy rates are still low among women with adenomyosis, even with assisted reproduction. According to the current study, endometrial receptivity is primarily responsible for the lower conception rate among patients with adenomyosis. Decidualization of endometrial stromal cells is the fundamental requirement for endometrial receptivity and the maintenance of a normal pregnancy, even though endometrial receptivity is made up of a variety of cells, including immune cells, endometrial epithelial cells, and endometrial stromal cells. Our overview reveals that endometriosis deficiencies are present in patients with adenomyosis. These flaws may be linked to aberrant pathways in endometrial stromal cells, such as PI3K/Akt, JAK2/STAT3, and hedgehog. Correcting the abnormal expression of molecules in endometrial stromal cells in the endometrium of patients with adenomyosis may become the focus of research to improve endometrial receptivity and increase the pregnancy rate.

Immune phenotype of the endometrium in patients with recurrent implantation failures after the transfer of genetically tested embryos in assisted reproductive technology programs

Recurrent implantation failures (RIF) in assisted reproduction programs are one of the most challenging problems. Among the factors that can adversely affect implantation, endometrial immune structural disorders may be one of the leading causes. The aim of our work was to study the immune features of the endometrium in women with RIF after genetically tested embryo transfer in comparison with fertile gestational carriers. Immune cells in endometrial samples were studied by flow cytometry and RNA expression of IL (interleukin)15, IL18, fibroblast growth factor-inducible 14 receptor (Fn14), and tumor necrosis factor-like weak inducer of apoptosis (TWEAK) by reverse polymerase chain reaction. In one-third of the cases, a unique immune profile of the endometrium, which we called the not transformed endometrial immune phenotype, was found. It is characterized by a combination of features, such as high expression of HLA-DR on natural killers (NK), increased fraction of CD16 + , and a decreased fraction of CD56bright endometrial NK. In addition, when compared to gestational carriers, patients with RIF had a greater discrepancy between IL18 mRNA expression data, reduced mean TWEAK and Fn14 levels, and increased IL18/TWEAK and IL15/Fn14 ratios. Immune abnormalities that were found in more than half of the patients (66.7 %) may be the cause of implantation failures in genetically tested embryo transfer programs.

Uterine NK cells underexpress KIR2DL1/S1 and LILRB1 in reproductive failure

A significant proportion of recurrent miscarriage, recurrent implantation failure and infertility are unexplained, and these conditions have been proposed to have an etiology of immunological dysfunction at the maternal-fetal interface. Uterine Natural Killer cells (uNK) comprise three subsets and are the most numerous immune cells found in the uterine mucosa at the time of implantation. They are thought to play an important role in successful pregnancy by regulation of extravillous trophoblast (EVT) invasion and spiral artery remodelling. Here, we examine the frequency, phenotype and function of uNK1-3 from the uterine mucosa of 16 women with unexplained reproductive failure compared to 11 controls with no reproductive problems, during the window of implantation. We report that KIR2DL1/S1 and LILRB1 expression is lower in the reproductive failure group for both uNK (total uNK, uNK 2 and 3) and pNK. We also show that degranulation activity is significantly reduced in total uNK, and that TNF-α production is lower in all uNK subsets in the reproductive failure group. Taken together, our findings suggest that reproductive failure is associated with global reduction in expression of uNK receptors important for interaction with HLA-C and HLA-G on EVT during early pregnancy, leading to reduced uNK activation. This is the first study to examine uNK subsets during the window of implantation in women with reproductive failure and will serve as a platform to focus on particular aspects of phenotype and function of uNK subsets in future studies. Further understanding of uNK dysregulation is important to establish potential diagnostic and therapeutic targets in the population of women with unexplained reproductive failure.

Number and function of uterine natural killer cells in recurrent miscarriage and implantation failure: a systematic review and meta-analysis

BACKGROUND

Uterine natural killer cells (uNK) are the most abundant lymphocytes found in the decidua during implantation and in first trimester pregnancy. They are important for early placental development, especially trophoblast invasion and transformation of the spiral arteries. However, inappropriate uNK function has been implicated in reproductive failure, such as recurrent miscarriage (RM) or recurrent implantation failure (RIF). Previous studies have mainly focussed on peripheral NK cells (pNK), despite the well-documented differences in pNK and uNK phenotype and function. In recent years, there has been an explosion of studies conducted on uNK, providing a more suitable representation of the immune environment at the maternal-foetal interface. Here, we summarize the evidence from studies published on uNK in women with RM/RIF compared with controls.

OBJECTIVE AND RATIONALE

The objectives of this systematic review and meta-analysis are to evaluate: differences in uNK level in women with RM/RIF compared with controls; pregnancy outcome in women with RM/RIF stratified by high and normal uNK levels; correlation between uNK and pNK in women with RM/RIF; and differences in uNK activity in women with RM/RIF compared with controls.

SEARCH METHODS

MEDLINE, EMBASE, Web of Science and Cochrane Trials Registry were searched from inception up to December 2020 and studies were selected in accordance with PRISMA guidelines. Meta-analyses were performed for uNK level, pregnancy outcome and uNK/pNK correlation. Narrative synthesis was conducted for uNK activity. Risk of bias was assessed by ROBINS-I and publication bias by Egger's test.

OUTCOMES

Our initial search yielded 4636 articles, of which 60 articles were included in our systematic review. Meta-analysis of CD56+ uNK level in women with RM compared with controls showed significantly higher levels in women with RM in subgroup analysis of endometrial samples (standardized mean difference (SMD) 0.49, CI 0.08, 0.90; P = 0.02; I2 88%; 1100 women). Meta-analysis of CD56+ uNK level in endometrium of women with RIF compared with controls showed significantly higher levels in women with RIF (SMD 0.49, CI 0.01, 0.98; P = 0.046; I2 84%; 604 women). There was no difference in pregnancy outcome in women with RM/RIF stratified by uNK level, and no significant correlation between pNK and uNK levels in women with RM/RIF. There was wide variation in studies conducted on uNK activity, which can be broadly divided into regulation and receptors, uNK cytotoxicity, cytokine secretion and effect of uNK on angiogenesis. These studies were largely equivocal in their results on cytokine secretion, but most studies found lower expression of inhibitory receptors and increased expression of angiogenic factors in women with RM.

WIDER IMPLICATIONS

The observation of significantly increased uNK level in endometrium of women with RM and RIF may point to an underlying disturbance of the immune milieu culminating in implantation and/or placentation failure. Further research is warranted to elucidate the underlying pathophysiology. The evidence for measuring pNK as an indicator of uNK behaviour is sparse, and of limited clinical use. Measurement of uNK level/activity may be more useful as a diagnostic tool, however, a standardized reference range must be established before this can be of clinical use.

The Role of Type I and Type II NKT Cells in Materno-Fetal Immunity

NKT cells represent a small but significant immune cell population as being a part of and bridging innate and adaptive immunity. Their ability to exert strong immune responses via cytotoxicity and cytokine secretion makes them significant immune effectors. Since pregnancy requires unconventional maternal immunity with a tolerogenic phenotype, investigation of the possible role of NKT cells in materno-fetal immune tolerance mechanisms is of particular importance. This review aims to summarize and organize the findings of previous studies in this field. Data and information about NKT cells from mice and humans will be presented, focusing on NKT cells characteristics during normal pregnancy in the periphery and at the materno-fetal interface and their possible involvement in female reproductive failure and pregnancy complications with an immunological background.

Pro- and Anti-Inflammatory Cytokines in the First Trimester-Comparison of Missed Miscarriage and Normal Pregnancy

The advantage in response of Th2 over Th1 is observed in normal pregnancy in peripheral blood. A disturbance of this balance can lead to symptoms of miscarriage and pregnancy loss. The aim of this study was to evaluate the pro- and anti-inflammatory cytokines in sera of women who were diagnosed with missed miscarriage in the first trimester and to compare this systemic immune response to the response in women with normal pregnancy. The study group consisted of 61 patients diagnosed with missed miscarriage. In total, 19 healthy women with uncomplicated first trimester created the control group. Cytokines were determined in the maternal serum by ELISA. The analysis included INF-γ, TNF-α, Il-1β, Il-4, Il-5, Il-6, Il-9, Il-10, Il-13 and TGF-β1. Th1 cytokine levels in the study group reached slightly higher values for INF-γ, Il-1β and slightly lower for IL-6 and TNF-α. In turn, Th2 cytokine levels in the study group were slightly higher (Il-9, Il-13), significantly higher (Il4, p = 0.015; Il-5, p = 0.0003) or showed no differences with the control group (Il-10). Slightly lower concentration involved only TGF-β1. Analysis of the correlation between levels of pro- and anti-inflammatory cytokines resulted in some discrepancies, without showing predominance of a specific immune response. The results did not confirm that women with missed miscarriage had an advantage in any type of immune response in comparison to women with normal pregnancy.

Effects of aspirin, vitamin D3, and progesterone on pregnancy outcomes in an autoimmune recurrent spontaneous abortion model

High proportions of placental lymphocytes expressing DX5+/CD25+/FOXP3+/CD45+/CD4+ are beneficial to maintain immune tolerance and improve pregnancy outcomes. This study aimed to compare and evaluate the therapeutic effects of aspirin, vitamin D3 (VitD3), and progesterone on the autoimmune recurrent spontaneous abortion (RSA) model. The autoimmune RSA mouse model was constructed, and the embryo loss rate was calculated for each group. Then, primary mouse placental lymphocytes were isolated, and the expression of DX5+/CD25+/FOXP3+/CD45+/CD4+ was detected through flow cytometry. The serum levels of anti-cardiolipin antibody (ACA), β2-GP1, CXCL6, IFN-γ, and IL-6 were measured by ELISA to evaluate the proportion of Th1 and Th2 cells. Autoimmune RSA significantly increased the embryo loss rate, which was improved by aspirin, VitD3, and progesterone treatment, and progesterone treatment had the best effect among the three treatments. The positive expression of DX5+/CD25+/FOXP3+/CD45+/CD4+ in the VitD3 and progesterone groups was significantly higher than that in the autoimmune RSA group, and the expression was highest in the progesterone treatment group. In the plasma of autoimmune RSA mice, the ACA, β2-GP1, CXCL6, and IFN-γ levels were significantly higher and the IL-6 level was lower than the levels in control mice. All these changes could be reversed by aspirin and progesterone treatment. In conclusion, aspirin, VitD3 and progesterone treatment improved pregnancy outcomes in autoimmune RSA mice by regulating the Th1/Th2 balance and cytokines, and progesterone had the best effect of the three treatments.

Imbalance of growth factors mRNA expression associated with oxidative stress in the early pregnancy loss

OBJECTIVE

The aim of this study was to examine the role of growth factors associated with angiogenesis and oxidative stress in the pathogenesis of spontaneous miscarriage.

METHODS

We performed a comparative mRNA expression analysis of VEGF, PlGF, Flt-1, Angiogenin and Endoglin using Real-Time PCR, in the placenta and decidua collected from 12 patients presenting with spontaneous abortion and from 14 women undergoing induced abortion, during the first and second trimester of pregnancy.

RESULTS

The mRNA expression of Flt-1 was significantly upregulated in the placenta of spontaneous abortions (5.17-fold, IQR: 2.72-9.11, p < 0.01). The placental expression of the soluble isoforms of Flt-1, sFlt-1 e15a and sFlt-1 i13, was also significantly upregulated in spontaneous abortions (sFlt-1 e15a: 2.35-fold, IQR: 0.98-2.83, p < 0.01; sFlt-1 i13: 3.47-fold, IQR: 2.37-5.08, p < 0,05). Placental tmFlt-1, PlGF and Endoglin showed a tendency of higher expression levels in spontaneous abortions, although they did not reach statistical significance (tmFlt-1: 7.42-fold, IQR: 3.58-14.32; PlGF: 2.36-fold, IQR: 0.90-4.12; Endoglin: 1.97-fold, IQR: 1.18-2.43). VEGF and Angiogenin mRNA expression in induced, as well as in spontaneous abortions, did not convey any statistically significant difference. In the decidua, the expression levels of Flt-1 and its splice variants sFlt-1 e15a, sFlt-1 i13 and tmFlt-1 did not show any statistically significant differences, as was the case for the rest of the herein examined growth factors.

CONCLUSIONS

In this study, we observed higher levels of sFlt-1 mRNA expression in the placenta of spontaneous abortions, while expression of other growth factors in placenta and decidua remained constant. This suggests that an imbalance of sFlt-1 expression in the placenta might contribute to the pathogenesis of spontaneous abortion, probably via oxidative stress, providing a possible biomarker for prompt identification of this condition.

Characterizing the immune cell population in the human fetal membrane

PROBLEM

This study localized CD45⁺ immune cells and compared changes in their numbers between term, not in labor (TNIL) and term, labor (TL) human fetal membranes.

METHOD OF STUDY

Fetal membranes (amniochorion) from normal TNIL and TL subjects were analyzed by immunohistochemistry (IHC), immunofluorescence (IF), and flow cytometry for evidence of total (CD45⁺ ) immune cells as well as innate immune cells (neutrophils, macrophages and NK cells) using specific markers. Fetal origin of immune cells was determined using polymerase chain reaction (PCR) for SRY gene in Y chromosome.

RESULTS

CD45⁺ cells were localized in human fetal membranes for both TNIL and TL. A threefold increase in CD45⁺ cells was seen in TL fetal membranes of (7.73% ± 2.35) compared to TNIL (2.36% ± 0.78). This increase is primarily contributed by neutrophils. Macrophages and NK cells did not change in the membranes between TNIL and TL. Leukocytes of fetal origin are present in the fetal membranes.

CONCLUSION

The fetal membranes without decidua contain a small proportion of immune cells. Some of these immune cells in the fetal membrane are fetal in origin. There is a moderate increase of immune cells in the fetal membranes at term labor; however, it is unclear whether this is a cause or consequence of labor. Further functional studies are needed to determine their contribution to membrane inflammation associated with parturition.

The expression of intracellular cytokines of decidual natural killer cells in unexplained recurrent pregnancy loss

OBJECTIVE

This study aims to investigate the expression levels of TNF-α, IFN-γ, IL-4, and IL-10 in dNK cells and determine whether or not the MAPK signal pathway is involved in the regulation of cytokine secretion by dNK cells at the maternal-fetal interface.

METHODS

In this study, we collected decidua specimens from patients with apparently normal pregnant and unexplained recurrent pregnancy loss (URPL) and extracted dNK cells by enzymatic digestion. Then the expression of cytokines were analyzed by flow cytometry and Real-Time PCR respectively.

RESULTS

The secretions of both IFN-γ and TNF-α in dNK cells in URPL were significantly higher than those in normal pregnancy. Furthermore, p38/MAPK inhibitors can inhibit the secretion of four cytokines in normal pregnancy, while in URPL cases, p38/MAPK inhibitors only significantly inhibit the secretion of IL-4 and IFN-γ. ERK inhibitors had no effect on the expression of all four cytokines and JNK/MAPK inhibitors varied on different cytokines.

CONCLUSION

URPL is associated with a NK1 cytokine profile. MAPK signaling pathway is involved in the regulation of cytokine secretion by decidual NK cells at maternal-fetal interface.

Novel pathways of inflammation in human fetal membranes associated with preterm birth and preterm pre-labor rupture of the membranes

Spontaneous preterm birth (PTB) and preterm pre-labor rupture of the membranes (pPROM) are major pregnancy complications. Although PTB and pPROM have common etiologies, they arise from distinct pathophysiologic pathways. Inflammation is a common underlying mechanism in both conditions. Balanced inflammation is required for fetoplacental growth; however, overwhelming inflammation (physiologic at term and pathologic at preterm) can lead to term and preterm parturition. A lack of effective strategies to control inflammation and reduce the risk of PTB and pPROM suggests that there are several modes of the generation of inflammation which may be dependent on the type of uterine tissue. The avascular fetal membrane (amniochorion), which provides structure, support, and protection to the intrauterine cavity, is one of the key contributors of inflammation. Localized membrane inflammation helps tissue remodeling during pregnancy. Two unique mechanisms that generate balanced inflammation are the progressive development of senescence (aging) and cyclic cellular transitions: epithelial to mesenchymal (EMT) and mesenchymal to epithelial (MET). The intrauterine build-up of oxidative stress at term or in response to risk factors (preterm) can accelerate senescence and promote a terminal state of EMT, resulting in the accumulation of inflammation. Inflammation degrades the matrix and destabilizes membrane function. Inflammatory mediators from damaged membranes are propagated via extracellular vesicles (EV) to maternal uterine tissues and transition quiescent maternal uterine tissues into an active state of labor. Membrane inflammation and its propagation are fetal signals that may promote parturition. This review summarizes the mechanisms of fetal membrane cellular senescence, transitions, and the generation of inflammation that contributes to term and preterm parturitions.

Changes of γδT cell subtypes during pregnancy and their influences in spontaneous abortion

A successful pregnancy is a complicated process that involves the precisely timed regulation of endocrine as well as immune system. Despite increasing knowledge about immunology in gestation, the studies of immune cells in endometrium and decidua are still fragmented. Dynamic data is lacking on the transition of pre-pregnancy endometrial lymphocytes to initial pregnancy states as well as to second/third-trimester status. Here, we determined the composition of Gamma delta (γδ) T cells in endometrium and decidua from women with normal pregnancy and unexplained spontaneous abortion. We found that the frequency of γδT cells is fluctuating over the course of pregnancy, and these changes were regulated by progesterone. Different from peripheral blood, Vδ1⁺ γδT cells accounted for the majority in endometrium and early-pregnancy decidua of healthy women, and endometrial stromal cells (ESCs) may involve in Vδ1/ Vδ2 shift directly. Moreover, an increase in the percentage of γδT cells with Vδ2 subset predominant in early-pregnancy decidua was associated with unexplained spontaneous abortion. Our results unraveled the precise timing of γδT cells occurring during pregnancy and the close relationship among endocrine, immune cells and pregnancy, which can further help understand and solve the problem of infertility and unexplained spontaneous abortion.