Multi-omics reveals the switch role of abnormal methylation in the regulation of decidual macrophages function in recurrent spontaneous abortion

RSA, recurrent spontaneous abortion, often causes serious physical damage and psychological pressure in reproductive women with unclarified pathogenesis. Abnormal function of decidual cells and aberrant DNA methylation have been reported to cause RSA, but their association remains unclear. Here, we integrated transcriptome, DNA methylome, and scRNA-seq to clarify the regulatory relationship between DNA methylation and decidual cells in RSA. We found that DNA methylation mainly influenced the function of decidual macrophages (DMs), of which four hub genes, HLA-A, HLA-F, SQSTM1/P62, and Interferon regulatory factor 7 (IRF7), related to 22 hypomethylated CpG sites, regulated 16 hub pathways to participate in RSA pathogenesis. In particular, using transcription factor analysis, it is suggested that the upregulation of IRF7 transcription was associated with enhanced recruitment of the transcription factor STAT1 by the hypomethylated promoter region of IRF7. As the current research on DNA methylation of macrophages in the uterine microenvironment of RSA is still blank, our systematic picture of abnormal DNA methylation in regulating DM function provides new insights into the role of DNA methylation in RSA occurrence, which may aid in further prevention and treatment of RSA.

Prophylaxis of decidual CD68+/CD163+ macrophage disbalance in extracorporeal fertilized women

The demographic crisis that prevailed in Ukraine in recent years, the state of war as a result of the aggression of the Russian Federation, reproductive losses among women of childbearing age are one of the most urgent problems in modern obstetrics and gynecology. One of the most effective methods of correcting impaired reproductive function is in vitro fertilization.

The purpose of this work

is to develop a pharmacological complex for the prevention of imbalance of CD68+/CD163+ decidual macrophages in vitro fertilized women.

Materials and methods

105 pregnant women who were divided into 3 groups took part in the study. The first group included 20 women whose pregnancy occurred and is proceeding physiologically. The second group consisted of 85 women who became pregnant as a result of in vitro fertilization, including 37 pregnant women who refused prophylactic correction of the threat of premature birth, and 48 pregnant women who received prophylactic correction of the threat of premature birth: complex prescription of vitamin D3 2000 IU orally 2 times a day, micronized progesterone 200 mg 2 times a day and l-arginine aspartate 1000 mg 4 times a day, starting from 18 to 20 weeks of pregnancy.

Results

In women who refused prophylactic correction of the threat of premature birth, a local increase in the activity of inducible NO-synthase and concentration of tumor necrosis factor-α, and a decrease in the activity of arginase and in the level of interleukin-10 were observed in the cervical mucus. They have a lower expression of CD163+ on placental decidual macrophages and an increased expression of CD68+, which indicates a shift in the polarization of macrophages from an anti-inflammatory to a pro-inflammatory phenotype. The use of prophylactic treatment brings the studied parameters closer to the results of women in whom pregnancy occurred physiologically.

Conclusions

In women who became pregnant as a result of in vitro fertilization, at 28-30 weeks of pregnancy, changes specific for pro-inflammatory phenotype of decidual macrophages were observed. Complex administration of vitamin D3, micronized progesterone and l-arginine aspartate lead to restoration of anti-inflammatory phenotype of decidual macrophages.

miR-146a-5p enhances embryo survival in unexplained recurrent spontaneous abortion by promoting M2 polarization of decidual macrophages

Unexplained recurrent spontaneous abortion (URSA) is one of the most challenging conditions in the reproductive field, and macrophage M1/M2 polarization disorder is involved in URSA pathogenesis, although the relevant mechanisms are undefined. miR-146a-5p possesses an immunoregulatory role and is expressed in decidual immune cells, and this study aims to investigate its effect on decidual macrophage polarization and therapeutic prospects in URSA, which has never been reported. The levels of M1/M2 markers in the deciduae and the miR-146a-5p expression in the decidual macrophages of URSA and healthy pregnant women were first detected and analyzed. Then, the in vitro effect of miR-146a-5p on the M1/M2 polarization and the secretion of inflammatory cytokines was investigated in Tamm-Horsfall protein-1 (THP-1)-induced macrophages. Finally, the in vivo immunotherapeutic effect of miR-146a-5p on embryo survival and the potential mechanisms were evaluated in a murine model of immune-based URSA. As a result, the abnormal M1/M2 polarization, which showed a shift towards the M1 phenotype and correlated with the decreased expression of miR-146a-5p, was verified in human URSA decidual macrophages. miR-146a-5p could inhibit M1 polarization, promote M2 polarization, and result in an anti-inflammatory microenvironment in THP-1-induced macrophages. The intravenous injection of exogenous miR-146a-5p in the first trimester of pregnant URSA mice significantly reduced the embryo resorption rate and promoted the M2 polarization of decidual macrophages. In conclusion, miR-146a-5p enhances embryo survival in URSA by promoting decidual macrophage polarization toward an M2 phenotype, giving new ideas and potential targets for subsequent research on the pathogenesis and immunotherapeutic strategies of URSA.

An imbalance of the IL-33/ST2-AXL-efferocytosis axis induces pregnancy loss through metabolic reprogramming of decidual macrophages

During embryo implantation, apoptosis is inevitable. These apoptotic cells (ACs) are removed by efferocytosis, in which macrophages are filled with a metabolite load nearly equal to the phagocyte itself. A timely question pertains to the relationship between efferocytosis-related metabolism and the immune behavior of decidual macrophages (dMΦs) and its effect on pregnancy outcome. Here, we report positive feedback of IL-33/ST2-AXL-efferocytosis leading to pregnancy failure through metabolic reprogramming of dMΦs. We compared the serum levels of IL-33 and sST2, along with IL-33 and ST2, efferocytosis and metabolism of dMΦs, from patients with normal pregnancies and unexplained recurrent pregnancy loss (RPL). We revealed disruption of the IL-33/ST2 axis, increased apoptotic cells and elevated efferocytosis of dMΦs from patients with RPL. The dMΦs that engulfed many apoptotic cells secreted more sST2 and less TGF-β, which polarized dMΦs toward the M1 phenotype. Moreover, the elevated sST2 biased the efferocytosis-related metabolism of RPL dMΦs toward oxidative phosphorylation and exacerbated the disruption of the IL-33/ST2 signaling pathway. Metabolic disorders also lead to dysfunction of efferocytosis, resulting in more uncleared apoptotic cells and secondary necrosis. We also screened the efferocytotic molecule AXL regulated by IL-33/ST2. This positive feedback axis of IL-33/ST2-AXL-efferocytosis led to pregnancy failure. IL-33 knockout mice demonstrated poor pregnancy outcomes, and exogenous supplementation with mouse IL-33 reduced the embryo losses. These findings highlight a new etiological mechanism whereby dMΦs leverage immunometabolism for homeostasis of the microenvironment at the maternal-fetal interface.

Downregulation of EZH2 in Trophoblasts Induces Decidual M1 Macrophage Polarization: a Potential Cause of Recurrent Spontaneous Abortion

Macrophages are known to be pivotal for ensuring the establishment of the immune tolerance microenvironment at the maternal–fetal interface. In particular, trophoblasts stay in close contact with decidual macrophages (DMs), which have been reported to play an active role in the modulation of the polarization of DMs. Thus, any dysfunction of trophoblasts might be associated with certain pregnancy‐related complications, such as recurrent spontaneous abortion (RSA). Enhancer of zeste homolog 2 (EZH2) is an important epigenetic regulatory gene that has been previously shown to be related to immune regulation. The present study assessed the expression of EZH2 in villi tissue obtained from healthy controls and RSA patients. Trophoblasts conditioned medium was collected to incubate macrophages differentiated from the THP‐1 cell line. The expression and function of EZH2 in trophoblasts were knocked down either by the use of siRNA or GSK126 as an inhibitor. Our results show a significant decrease in the expression of EZH2 in villi tissue from RSA patients as compared to healthy controls. Further, the inhibition of expression or function of EZH2 in trophoblasts promoted M1 macrophage polarization, which might be involved in the pathogenesis of RSA. Moreover, the suppression of EZH2 was found to affect the secretion of immune and inflammatory cytokines in trophoblasts. Altogether, these results indicated the importance of EZH2 in the regulation of immune functions of trophoblasts and thus highlighted its potential to be explored as a therapeutic target to prevent and treat pregnancy loss.

Pharmacological activation of rev-erbα suppresses LPS-induced macrophage M1 polarization and prevents pregnancy loss

BACKGROUND

Circadian rhythm is an important player for reproduction. Rev-erbα, a significant clock gene, is involved in regulating cell differentiation, inflammation and metabolism. Macrophage polarization plays crucial roles in immune tolerance at the maternal-fetus interface, which also modulates the initiation and resolution of inflammation. Alteration of macrophage polarization induces adverse pregnancy outcomes such as infertility, recurrent spontaneous abortion and preterm labor.

RESULTS

Decidual macrophages from LPS-induced mice abortion model displayed M1-like bias, accompanied by decreased expression of Rev-erbα. SR9009, an agonist of Rev-erbα, may reduce lipopolysaccharide (LPS)-induced M1 polarization of macrophages via activation of PI3K but not NF-κB signaling pathway. Furthermore, SR9009 could reduce M1-like polarization of decidual macrophages induced by LPS and attenuate LPS-induced resorption rates in mice model.

CONCLUSIONS

Both in vivo and in vitro experiments demonstrated that the pharmacological activation of Rev-erbα using SR9009 could attenuate the effect of LPS on macrophage polarization and protect pregnancy. This study may provide a potential therapeutic strategy for miscarriage induced by inflammation.

Functional regulation of decidual macrophages during pregnancy

A successful pregnancy requires that the maternal immune system recognizes and tolerates the semi-allogeneic fetus without compromising the capability of protecting both mother and fetus from various pathogens. Decidual macrophages present unique phenotypes to play a key role in the establishment of the immunological aspects of maternal-fetal interaction. Dysfunction of decidual macrophages gives rise to pregnancy complications such as preeclampsia, recurrent spontaneous miscarriage, preterm labor and fetal growth restriction. Here, we reviewed the latest knowledge on the origin, differentiation, unique phenotype and function of macrophages in normal pregnancy and in pregnancy complications. We mainly focused on the significant roles of decidual macrophages in the process of extravillous trophoblast invasion, spiral arterial remodeling, decidual stromal cells cultivation and immune tolerance maintenance in normal pregnancy, and their pathological roles in pregnancy-related complications, offering more integrated information in maternal-fetal immunity.

Exosomes released from decidual macrophages deliver miR-153-3p, which inhibits trophoblastic biological behavior in unexplained recurrent spontaneous abortion

BACKGROUND

Spontaneous abortion is a common disease in human pregnancy. Increasing evidence suggests that proper function of trophoblasts and immune balance of the maternal-fetal interface are crucial for successful pregnancy. Macrophages are involved in the maternal-fetal immune microenvironment. However, mechanisms associated with how macrophages impair trophoblasts' function in spontaneous abortion remain to be explored.

METHODS

Firstly, the characteristics of the isolated macrophage-derived exosomes were verified by TEM and Western blot. Then, we established the co-culture of macrophage-derived exosomes with trophoblasts, and explored the role of the exosomes in trophoblasts. Moreover, expression of miR-153-3p in the macrophage-derived exosomes was detected. A miR-153-3p mimic was transfected into trophoblasts to investigate its function in the biological functions of trophoblast cells. MRNA and protein expressions were detected by qRT-PCR and Western blot. CCK8 assay was performed to measure cell proliferation and Transwell assay was utilized to examine migration of trophoblasts.

RESULTS

Compared with those in normal pregnant women, decidual macrophage-derived exosomes from unexplained recurrent spontaneous abortion (URSA) patients suppressed the proliferation and migration of trophoblast cells through the IDO/STAT3 pathway. MiR-153-3p was highly expressed in exosomes released from decidual macrophages of URSA patients. Transfecting miR-153-3p mimics into trophoblast cells directly inhibited IDO genes, which suppressed STAT3 pathway activation, regulating the biological behavior of trophoblast cells.

CONCLUSIONS

This study outlines the role of decidual macrophage-derived exosomal miR-153-3p in successful pregnancy maintenance, paving a new approach for the development of novel treatments for URSA.

Decidual macrophage M1 polarization contributes to adverse pregnancy induced by Toxoplasma gondii PRU strain infection

Recent evidence indicates that macrophages at the maternal-fetal interface adapt to a phenotype characterized by alternative activation (M2 polarization) and exhibit immunosuppressive functions that favor the maintenance of pregnancy. The bias of M2 decidual macrophages toward M1 has been clinically linked to pregnancy-related complications, such as preeclampsia and preterm delivery. The aim of this study was to investigate the effect of Toxoplasma gondii PRU strain infection on the bias of decidual macrophage polarization and its contribution to adverse pregnancy outcomes. A mouse model with adverse pregnancy outcome was established by infection with T. gondii PRU strain and the expression levels of functional molecules in decidual macrophages of mice were measured. The results showed that T. gondii infection caused seriously adverse pregnancy outcome in mice. The placentae of infected mice showed obvious congestion and inflammatory cell infiltration. The expression of CD206, MHC-II, and arginase-1 considered as M2 markers was decreased in decidual macrophages after T. gondii infection, whereas the expression of CD80, CD86, iNOS, and cytokines TNF-α and IL-12 considered as M1 markers was increased. Furthermore, iNOS-positive expression was observed in the decidua basalis of infected mice. Our results indicated that T. gondii infection was responsible for the bias of M2 decidual macrophages toward M1, which changes the immunosuppressive microenvironment at the maternal-fetal interface and contributes to adverse pregnancy outcomes.

The Role of Decidual Macrophages During Normal and Pathological Pregnancy

Macrophages perform many specific functions including host defense, homeostasis, angiogenesis, and tissue development. Macrophages are the second most abundant leukocyte population in the non-pregnant endometrium and pregnant decidua and likely play a central role in the establishment and maintenance of normal pregnancy. Importantly, aberrantly activated uterine macrophages can affect trophoblast function and placental development, which may result in various adverse pregnancy outcomes ranging from pre-eclampsia to fetal growth restriction or demise. Only by fully understanding the roles of macrophage in pregnancy will we be able to develop interventions for the treatment of these various pregnancy complications. This review discusses the general origin and classification of monocytes and macrophages and focuses on the phenotype and functional roles of decidual macrophage at the maternal-fetal interface in normal pregnancy, as well as discussing the potential contribution of the abnormal state of these cells to various aspects of pregnancy pathologies.