Potential role of decidual apoptosis in the pathogenesis of miscarriages

Inhibition of ferroptosis attenuate lipopolysaccharide-induced early pregnancy loss by protecting against decidual damage of stromal cells

Endometrial decidualization is critical for successful embryo implantation. Dysregulation of the immune microenvironment can disrupt normal decidualization processes, potentially resulting in early pregnancy loss. Ferroptosis, a form of cell death dependent on iron and lipid hydroperoxides, is closely associated with inflammation. In this study, we developed an inflammatory early pregnancy loss model to elucidate the mechanisms of decidual damage induced by lipopolysaccharide (LPS) and to assess whether ferroptosis contributes to LPS-induced early pregnancy loss. Through in vivo experiments, we observed that embryo implantation was significantly inhibited and endometrial decidualization was impaired during LPS-induced early pregnancy loss. LPS exposure resulted in abnormal mitochondrial morphology, reduced antioxidant capacity, accumulation of reactive oxygen species (ROS) and disruptions in iron metabolism during decidualization in mouse endometrial stromal cells (mESCs). The administration of ferroptosis inhibitors, specifically ferrostatin-1 (Fer-1) and deferoxamine (DFO), effectively reversed embryo loss and mitigated the decidual damage associated with LPS-induced early pregnancy loss. Fer-1 and DFO exhibited resistance to ferroptosis during decidualization by modulating the antioxidant system and iron metabolism in mESCs, respectively. Our findings indicate that the inhibition of ferroptosis can confer protective effects against decidual damage during LPS-induced early pregnancy loss in mice.

Decreased expression and DNA hypermethylation of syncytin-1 in human villus tissues with unexplained recurrent spontaneous abortion

Recurrent spontaneous abortion (RSA) affects approximately 5 % of women of reproductive age worldwide. The etiology and pathogenesis of approximately 50 % of RSA cases currently remain unclear, which known as unexplained RSA (URSA). Syncytin-1, an envelope protein encoded by HERV-W gene, is essential for human embryonic development. The purpose of this study was to explore the correlation between syncytin-1 expression and URSA occurrence. The villi tissues of URSA patients and patients with voluntary termination of pregnancy for non-medical reasons in early pregnancy (Control group) were collected. Compared with the Control group, syncytin-1 was abnormally low expressed in URSA villus tissues, and the HERV-W gene promoter was hypermethylated. Compared with the control group, the global DNA methylation level and the expression level of DNA methylases in the villus tissues of the URSA group had no significant difference. In addition, compared with the Control group, URSA villus tissue showed obviously abnormal apoptosis. Overexpression of syncytin-1 promoted the proliferation of HTR-8 cells and inhibited their apoptosis; while knockdown of syncytin-1 inhibited cell proliferation and promoted cell apoptosis. URSA villus tissue exhibited hypermethylation of the HERV-W gene and down-regulation of syncytin-1 expression. Syncytin-1 has the potential to be a predictive and diagnostic biomarker for URSA.

The Alteration of m6A Modification at the Transcriptome-Wide Level in Human Villi During Spontaneous Abortion in the First Trimester

A growing number of studies have demonstrated that N6 methyladenine (m⁶A) acts as an important role in the pathogenesis of reproductive diseases. Therefore, it is essential to profile the genome-wide m⁶A modifications such as in spontaneous abortion. In this study, due to the trace of human villi during early pregnancy, we performed high-throughput sequencing in villous tissues from spontaneous abortion (SA group) and controls with induced abortion (normal group) in the first trimester. Based on meRIP-seq data, 18,568 m⁶A peaks were identified. These m⁶A peaks were mainly located in the coding region near the stop codon and were mainly characterized by AUGGAC and UGGACG motif. Compared with normal group, the SA group had 2,159 significantly upregulated m⁶A peaks and 281 downregulated m⁶A peaks. Biological function analyses revealed that differential m⁶A-modified genes were mainly involved in the Hippo and Wnt signaling pathways. Based on the conjoint analysis of meRIP-seq and RNA-seq data, we identified thirty-five genes with differentially methylated m⁶A peaks and synchronously differential expression. And these genes were mainly involved in the Wnt signaling pathway, phosphatase activity regulation, protein phosphatase inhibitor activity, and transcription inhibitor activity. This study is the first to profile the transcriptome-wide m⁶A methylome in spontaneous abortion during early pregnancy, which provide novel insights into the pathogenesis and treatment of spontaneous abortion in the first trimester.

L-NAME, a nitric oxide synthase inhibitor, increases the protein expression of both executioner and inhibitor of apoptosis in the placental bed of mid-to-late pregnant rats

The involvement of nitric oxide (NO) signaling in apoptosis was examined in the placental bed of mid-to-late pregnant rats. Pregnant rats were treated with l-NAME, a nitric oxide synthase inhibitor, by subcutaneous infusion for 48 hours before the examination at day 13.5, 17.5, or 21.5. l-NAME induced apoptosis in the placental bed to a limited extent at days 13.5 and 17.5, but not at day 21.5. When the placental bed was examined at day 17.5, the protein expression of both executioner (C-Cas3) and inhibitor (XIAP) of apoptosis was increased by l-NAME, but they did not co-localized with apoptosis. It was presumed that placental bed apoptosis induced by l-NAME is regulated through the expression of both executioner and inhibitor, possibly involving protein S-nitrosylation.

Senescent Changes and Endoplasmic Reticulum Stress May Be Involved in the Pathogenesis of Missed Miscarriage

Background

Senescence is involved in many complications of pregnancy. However, whether senescent changes are also associated with missed miscarriage has not been fully investigated.

Methods

The levels of p16, p21, and γH2AX, markers of senescence, were measured in placentas collected from women with missed miscarriage by immunohistochemistry and Western blotting. Levels of misfolded proteins in missed miscarriage placentas or normal first-trimester placenta that had been treated with H₂O₂ (100 μM) or extracellular vesicles (EVs) collected from missed miscarriage placental explant culture were measured by fluorescent compound, thioflavin-T. The production of reactive oxygen species (ROS) by missed miscarriage placentas was measured by CellROX^® Deep Red.

Results

Increased levels of p16, p21, and γH2AX were presented in missed miscarriage placentas compared to controls. Increased levels of misfolded proteins were shown in missed miscarriage placentas, but not in EVs that were collected from missed miscarriage placentas. The ROS production was significantly increased in missed miscarriage placental explant cultures. Increased levels of misfolded proteins were seen in the normal first-trimester placenta that had been treated with H₂O₂ compared to untreated.

Conclusion

Our data demonstrate that there are increases in senescence and endoplasmic reticulum stress and ROS production in missed miscarriage placenta. Oxidative stress and an accumulation of misfolded proteins in missed miscarriage placentas may contribute to the changes of senescence and endoplasmic reticulum stress seen in missed miscarriage placentas.

Evaluation of Apoptosis, Proliferation, and Adhesion Molecule Expression in Trophoblastic Tissue of Women With Recurrent Spontaneous Abortion and Infected With Toxoplasma gondii

Recurrent spontaneous abortion is an obstetric complication with undefined causes. Apoptosis, proliferation, and adhesion are considered important factors in the pathogenesis of abortion. This work aimed to determine Bax and Bcl-2 as a proapoptotic and antiapoptotic protein, Ki67 and P27kip as proliferative and antiproliferative proteins, and E-cadherin and CD44 as adhesion molecules in the trophoblastic tissues in cases with recurrent miscarriage. Immunohistochemistry and quantitative polymerase chain reaction analysis of Bax, Bcl-2, Ki67, P27kip, E-cadherin, and CD44 in paraffin-embedded sections of placental tissues obtained from 108 women were divided into 3 categories: 66 Toxoplasma gondii-positive women with recurrent abortion, 22 T. gondii-negative women with recurrent abortion, and 20 women with no history of abortion as a control group. The mean ratio of the expression of Bax and P27kip proteins was 35.3% and 36.1%, which is significantly higher than that of the second group (19.88 and 20.02%), and the third group (12.3% and 10.98%), while the mean ratio of the expression of Bcl-2, Ki67, E-cadherin, and CD44 proteins was 12.35%, 11.23%, 10.32%, and 9.97%, which is significantly lower than that of the second group (33.75%, 13.18%, 21.88%, and 23.29%) and that of the third group (38.58%, 39.27%, 37.98%, and 35.79%). The presence of proapoptotic protein (Bax) and antiproliferative protein (P27kip) at high levels and the presence of antiapoptotic protein (Bcl-2), proliferative protein (Ki67), and adhesion molecules (E-cadherin and CD44) in lower levels in the T. gondii-positive group clarify the mechanism involved in the induction of abortion and loss of pregnancy.

Long non-coding RNA H19 regulates Bcl-2, Bax and phospholipid hydroperoxide glutathione peroxidase expression in spontaneous abortion

Spontaneous abortion (SA) is the most frequently occurring pregnancy disorder and is a serious threat to women's health. Identifying novel risk factors and the molecular mechanisms underlying SA are important. The present study reported that the RNA expression levels of long non-coding RNA H19 were lower in SA group compared with those in the control group, and the expression of Bax was increased and levels of Bcl-2 and phospholipid hydroperoxide glutathione peroxidase (GPX4) were decreased in SA group at both the mRNA and protein levels. H19 expression was positively correlated with Bcl-2 and GPX4 expression and negatively linked with Bax levels. It was demonstrated that silencing H19 downregulated Bcl-2 and GPX4 expression and upregulated Bax expression at both the mRNA and protein levels in HTR-8/SVneo trophoblast cells. In conclusion, the present findings suggested that H19 has important roles in SA by promoting apoptosis and ferroptosis.

FasL on decidual macrophages mediates trophoblast apoptosis: A potential cause of recurrent miscarriage

Macrophages can induce Fas ligand (FasL)-mediated apoptosis, and the deregulation of apoptosis is known to be associated with recurrent miscarriage (RM). The aim of the present study was to investigate the possible involvement of FasL in macrophage-mediated trophoblast apoptosis and its potential role in RM. Human decidual and placental villous tissues were collected from 81 women (21 for the RM group, 26 for the spontaneous abortion group and 34 for the control group) at 7-9 weeks of gestation. The distribution changes of macrophages and the expression of FasL on macrophages were evaluated by immunohistochemical, immunofluorescence and western blot analyses. A macrophage and trophoblast co-culture model was used to determine the effects of FasL on the apoptosis of trophoblasts. The results indicated that CD86⁺ macrophage populations in decidual tissues were significantly increased, accompanied by reduced CD163⁺ macrophages in the abortion and RM groups. Furthermore, the distribution of CD68⁺ macrophages was also significantly altered in specimens from the abortion and RM groups, and they were observed to have infiltrated into the trophoblast cells. In addition, elevated expression of FasL on CD68⁺ and CD86⁺ macrophages in the decidua was observed in the spontaneous abortion and RM groups of patients, and FasL was demonstrated to mediate the induction of trophoblast apoptosis by macrophages in co-culture. These results indicate that the aberration of macrophage-induced FasL-mediated apoptosis may represent one of the causes of RM.

Biochemical clinical factors associated with missed abortion independent of maternal age: A retrospective study of 795 cases with missed abortion and 694 cases with normal pregnancy

The incidence of fertile women with missed abortion dramatically increased in recent years, while very few serum indices have been identified for the diagnosis of missed abortion. The aim of this study was to identify related factors for missed abortion through a retrospective study of serum indices.A total of 795 cases of women with missed abortion and 694 cases of women with normal pregnancy between March 2014 and March 2017 were included in the present study. The diagnosis of missed abortion was based on clinical history, clinical examination, and transvaginal ultrasound findings. The final diagnosis of missed abortion was based on assessment of pregnancy structures (i.e., a gestational sac without fetal heart rate) via transvaginal ultrasound. We evaluated the clinical values of 4 serum indices and their relationship to missed abortion: gamma-glutamyltransferase (GGT), lactate dehydrogenase (LDH), adenosine deaminase (ADA), and fibrinogen (FIB).The serum levels of GGT, ADA, and FIB showed statistically significant differences comparing women who experienced missed abortion with women who had normal pregnancies (controls). Among women with missed abortion, the levels of GGT and ADA were dramatically increased (GGT: P < .0001; ADA: P = .0459), while FIB levels were slightly lower (P = .0084) compared to controls. The LDH levels exhibited a non-significant trend toward lower levels in the missed abortion group (P = .3951). Interestingly, the observed significant increase in serum GTT levels among women with missed abortion was not affected by maternal age.This study found that GTT may be a useful marker which was associated with missed abortion, indicating its potential clinical roles in missed abortion.

FOXO3a is essential for murine endometrial decidualization through cell apoptosis during early pregnancy

Embryo implantation is essential for normal pregnancy, and the process of decidualization is critical for embryo implantation. However, the mechanism of decidualization during early pregnancy is still unknown. Forkhead box O3a (FOXO3a) is the most important functional transcription factor of the forkhead box family and is a highly conserved transcription factor of apoptosis-related genes. In the mouse uterus, FOXO3a was found to be expressed regularly from Days 1-7 of early pregnancy. Upon further exploration, it was found that FOXO3a was expressed at significantly higher levels at the implantation site than at the interimplantation site on Days 5-7 of pregnancy. Under artificial decidualization, FOXO3a was highly expressed in the first and second decidual zones. After decidualization, the expression of FOXO3a was significantly increased both in vivo and vitro. In primary stromal cells, apoptosis was reduced by decreased expression of FOXO3a after inducing decidualization. Moreover, when FOXO3a-small interfering RNA was transfected into the uteri of mice, the expression of decidualization- and apoptosis-related factors was impaired. Thus, FOXO3a might play an important role in decidualization during early pregnancy, and cell apoptosis might be one of pathways for FOXO3a-regulated decidualization.

Abnormal expression of microRNA-575 leads to missed abortion through regulating apoptosis and angiogenesis

Numerous microRNA (miR) are important for placental development and function. miR-575 has been demonstrated to be upregulated in maternal placenta in patients who have experienced a miscarriage. The present study aimed to explore the role of abnormal expression of miR-575 in missed abortion (MA) and to further analyze the potential molecular mechanisms. Embryo villus tissue samples were extracted from 10 childless women with MA and 10 fertile women without a history of MA. Additionally, human choriocarcinoma cells, JEG-3, were used in the present study, which were transfected with miR-575 mimic, inhibitor and scramble. The expression of miR-575 in embryo villus tissues and in JEG-3 cells was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Apoptosis in villus tissues of patients with MA and in JEG-3 cells of miR-575 mimic, inhibitor and scramble groups were detected by flow cytometry. Furthermore, the expression levels of apoptosis-related proteins, including B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax) and phosphorylated (p)-p53, and angiogenesis-related proteins, including vascular endothelial growth factor (VEGF) and angiopoietin 2 (Ang-2), were measured by RT-qPCR and western blotting. Additionally, the target of miR-575 was predicted and clarified by luciferase reporter assay. miR-575 was significantly overexpressed in MA villus tissue compared with normal tissue (P<0.05). The percentage of apoptotic cells in MA embryo villus tissue was significantly higher than that in normal tissue (P<0.05). After JEG-3 cells were transfected with miR-575 inhibitor, the expression of miR-575 and the percentage of apoptotic cells decreased significantly compared with the control (P<0.05). MiR-575 suppression significantly increased the expression of Bcl-2 (P<0.05), and decreased the expressions of Bax (P<0.05) and p-p53 (P<0.01) compared with the control. Furthermore, miR-575 suppression significantly increased the expressions of angiogenesis-related proteins, Ang-2 and VEGF (P<0.01). Superoxide dismutase 2 was identified as the target of miR-575. Therefore, abnormal expression of miR-575 may lead to MA through regulating apoptosis and angiogenesis. Inhibition of miR-575 may inhibit apoptosis and promote angiogenesis in MA.

Abnormal Expression of TRAIL Receptors in Decidual Tissue of Chlamydia trachomatis-Infected Rats During Early Pregnancy Loss

Chlamydia trachomatis is the scientific name of pathogenic bacteria causing infection that has been linked to spontaneous abortion. In this study, the expression pattern of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL; a cytokine related to cell apoptosis) and its receptors was monitored in the decidua of C trachomatis-infected pregnant rats during early gestation to investigate the potential role of this molecular system in C trachomatis-induced spontaneous abortion. The data showed that C trachomatis infection significantly altered the messenger RNA (mRNA) expression of the receptors; death receptor (DR) 4 and DR5 increased, but decoy receptor (DcR) 1 and DcR2 decreased. Consistent with mRNA data, immunohistochemical staining of TRAIL and its receptors indicated that both DR4 and DR5 protein levels were elevated in infected tissues, primarily, decidual cells, decidual vessel wall, and uterine glands, whereas DcR1 and DcR2 showed lower levels compared to the noninfected group. Although receptor expression was altered, there was no difference detected in TRAIL expression. The observed altered expression of TRAIL receptors in C trachomatis-infected rats compared to noninfected rats during the embryo implantation phase suggests a possible mechanism for spontaneous abortion due to apoptosis and therefore failed embryo implantation. In addition, the observed increase in caspase-3 levels in infected cells further supports this finding. Taken together, the data presented in this study suggests C trachomatis infection altered the expression of TRAIL receptors, thus representing a general mechanism for C trachomatis-induced spontaneous abortion in C trachomatis-infected rats during early pregnancy loss.

Increased apoptosis rate of human decidual cells and cytotrophoblasts in patients with recurrent spontaneous abortion as a result of abnormal expression of CDKN1A and Bax

In the present study, we analyzed the proliferation and apoptosis of trophoblasts and human decidual cells in patients with recurrent spontaneous abortion and the related cellular pathway mechanism. Thirty-four patients with recurrent abortion and 30 healthy pregnant women undergoing planned artificial abortion were selected. The trophoblast and decidual cells were collected by negative pressure aspiration technique. TUNEL method was used to detect the apoptosis rate. Immunohistochemical method was used for detection of TP53 protein. Quantitative real-time PCR was used for detection of the relative expression level of CDKN1A and Bax mRNA. It was found that the cell apoptosis rate in the recurrent miscarriage group was significantly increased and the expression levels of TP53 protein, CDKN1A and Bax mRNA were also significantly increased (p<0.05). In conclusion, the trophoblast and decidual cells of patients with recurrent abortion were obviously apoptotic, which was probably related to abnormal expression of the CDKN1A and Bax genes mediated by TP53 protein through cellular pathways.

Association between p53 polymorphism at codon 72 and recurrent spontaneous abortion

p53 gene plays an important role in apoptosis, which is necessary for successful invasion of trophoblast cells. The change from an arginine (Arg) to a proline (Pro) at codon 72 can influence the biological activity of p53, which predisposes to an increased risk of recurrent spontaneous abortion (RSA). In order to investigate the association between p53 polymorphism at codon 72 and RSA, we conducted this meta-analysis. Pubmed, Embase and Web of science were used to identify the eligible studies. Odds ratio (OR) with 95% confidence interval (CI) was used to evaluate the strength of the association. Six studies containing 937 cases of RSA and 830 controls were included, and there was one study deviated from Hardy-Weinberg equilibrium (HWE). There was a significant association between p53 polymorphism at codon 72 and RSA in recessive model (Pro/Pro vs. Pro/Arg+Arg/Arg; OR=1.60, 95% CI: 1.14-2.24) and co-dominant model (Pro/Pro vs. Arg/Arg; OR=1.47, 95% CI: 1.02-2.12) whether the study that was deviated from HWE was eliminated or not. A significant association was observed in allelic model (Pro vs. Arg; OR=1.28, 95% CI: 1.04-1.57) after exclusion of the study that was deviated from HWE. No association was noted in recessive model (Pro/Pro+Pro/Arg vs. Arg/Arg; OR=1.05, 95% CI: 0.86-1.30) and co-dominant model (Pro/Arg vs. Arg/Arg; OR=0.96, 95% CI: 0.77-1.19). Subgroup analysis by ethnicity also indicated a significant association between p53 polymorphism at codon 72 and RSA in Caucasian group. No heterogeneity and publication bias were found. Our meta-analysis implied that p53 polymorphism at codon 72 carries high maternal risk of RSA.

Blocking Endogenous Leukemia Inhibitory Factor During Placental Development in Mice Leads to Abnormal Placentation and Pregnancy Loss

The placenta forms the interface between the maternal and fetal circulation and is critical for the establishment of a healthy pregnancy. Specialized trophoblast cells derived from the embryonic trophectoderm play a pivotal role in the establishment of the placenta. Leukemia inhibitory factor (LIF) is one of the predominant cytokines present in the placenta during early pregnancy. LIF has been shown to regulate trophoblast adhesion and invasion in vitro, however its precise role in vivo is unknown. We hypothesized that LIF would be required for normal placental development in mice. LIF and LIFRα were immunolocalized to placental trophoblasts and fetal vessels in mouse implantation sites during mid-gestation. Temporally blocking LIF action during specific periods of placental development via intraperitoneal administration of our specific LIFRα antagonist, PEGLA, resulted in abnormal placental trophoblast and vascular morphology and reduced activated STAT3 but not ERK. Numerous genes regulating angiogenesis and oxidative stress were altered in the placenta in response to LIF inhibition. Pregnancy viability was also significantly compromised in PEGLA treated mice. Our data suggest that LIF plays an important role in placentation in vivo and the maintenance of healthy pregnancy.

Crystallin αB acts as a molecular guard in mouse decidualization: regulation and function during early pregnancy

Although decidualization is crucial for the establishment of successful pregnancy, the molecular mechanism underlying decidualization remains poorly understood. Crystallin αB (CryAB), a small heat shock protein (sHSP), is up-regulated and phosphorylated in mouse decidua. In mouse primary endometrial stromal cells, CryAB is induced upon progesterone treatment via HIF1α. In addition, CryAB is strongly phosphorylated through the p38-MAPK pathway under stress or during in vitro decidualization. Knockdown of CryAB results in the increase of apoptosis of stromal cells and inhibits decidualization under oxidative or inflammatory stress. Our data indicate that CryAB protects decidualization against stress conditions.

Apoptosis and p53 expression in the placental villi of females with unexplained recurrent spontaneous abortion

The aim of this study was to explore the level of apoptosis and p53 expression in the placental villi of patients with unexplained recurrent spontaneous abortion (URSA). Fifty-three pregnant females with URSA and 32 pregnant females who required an induced abortion were selected as the subjects of this study. Placental villus tissues were collected from June 2010 to June 2012 and quantitative polymerase chain reaction (qPCR) and immunohistochemical analysis were performed to determine the mRNA and protein levels of p53 in the placental villus tissues. The level of apoptosis in the tissues was studied using terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) assay. The mRNA and protein expression levels of p53 in the URSA group were significantly higher than those in the control group (P<0.05). Furthermore, the levels of apoptosis were increased markedly in the URSA group compared with the control group (P<0.05). In conclusion, the placental villi of patients with URSA express a high level of p53, which may result in cell apoptosis and lead to recurrent spontaneous abortion.