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Human Reproduction Update Jun 2022Uterine natural killer cells (uNK) are the most abundant lymphocytes found in the decidua during implantation and in first trimester pregnancy. They are important for... (Meta-Analysis)
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.
Topics: Abortion, Habitual; Cytokines; Embryo Implantation; Endometrium; Female; Humans; Killer Cells, Natural; Placenta; Pregnancy; Uterus
PubMed: 35265977
DOI: 10.1093/humupd/dmac006 -
Frontiers in Immunology 2022Recurrent spontaneous abortion (RSA) is defined as two or more pregnancy loss, affecting the happiness index of fertility couples. The mechanisms involved in the...
Recurrent spontaneous abortion (RSA) is defined as two or more pregnancy loss, affecting the happiness index of fertility couples. The mechanisms involved in the occurrence of RSA are not clear to date. The primary problem for the maternal immune system is how to establish and maintain the immune tolerance to the semi-allogeneic fetuses. During the pregnancy, decidual macrophages mainly play an important role in the immunologic dialogue. The purpose of this study is to explore decidual macrophages, and to understand whether there is a connection between these cells and RSA by analyzing their phenotypes and functions. Pubmed, Web of Science and Embase were searched. The eligibility criterion for this review was evaluating the literature about the pregnancy and macrophages. Any disagreement between the authors was resolved upon discussion and if required by the judgment of the corresponding author. We summarized the latest views on the phenotype, function and dysfunction of decidual macrophages to illuminate its relationship with RSA.
Topics: Pregnancy; Humans; Female; Decidua; Abortion, Habitual; Macrophages; Abortion, Induced
PubMed: 36569856
DOI: 10.3389/fimmu.2022.994888 -
American Journal of Reproductive... Feb 2018Parturition at term is characterized by inflammatory overload in both feto-maternal tissues. Despite the large number of individual studies on changes in inflammatory... (Review)
Review
Parturition at term is characterized by inflammatory overload in both feto-maternal tissues. Despite the large number of individual studies on changes in inflammatory biomarkers linked to labor, a comprehensive profile of them in each of the uterine compartments is not available to better understand their mechanistic contributions to labor. This systematic review investigated the pro- and anti-inflammatory biomarkers reported in intra-uterine tissues (amnion, chorion, decidua, placenta, and myometrium) at term labor. We conducted a systematic review of studies on pro- and anti-inflammatory biomarkers (mRNA and/or protein) reported in feto-maternal tissues during normal human term labor, published in English (1980-2016), in 3 electronic data bases. From a total of 3712 citations, 172 were included for final review. Each tissue expresses a unique set of biomarkers at the time of term labor, but there is significant overlap between tissues. All tissues had IL-6, IL-8, IL-1β, COX-2, PGE-2, TNF-α, and hCAP18 in common at term labor. Common and unique inflammatory biomarkers are expressed in various feto-maternal compartments at term labor. Increase in pro-inflammatory markers in all gestational tissue signifies their harmonious functional role in promoting labor. Anti-inflammatory markers at term labor are hardly reported.
Topics: Animals; Antimicrobial Cationic Peptides; Biomarkers; Cathelicidins; Cyclooxygenase 2; Female; Humans; Inflammation; Inflammation Mediators; Metalloporphyrins; Parturition; Pregnancy; Uterus
PubMed: 29076197
DOI: 10.1111/aji.12776 -
BMC Medical Genomics Jun 2015Preterm birth (PTB), or birth before 37 weeks of gestation, is the leading cause of newborn death worldwide. PTB is a critical area of scientific study not only due to... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Preterm birth (PTB), or birth before 37 weeks of gestation, is the leading cause of newborn death worldwide. PTB is a critical area of scientific study not only due to its worldwide toll on human lives and economies, but also due to our limited understanding of its pathogenesis and, therefore, its prevention. This systematic review and meta-analysis synthesizes the landscape of PTB transcriptomics research to further our understanding of the genes and pathways involved in PTB subtypes.
METHODS
We evaluated published genome-wide pregnancy studies across gestational tissues and pathologies, including those that focus on PTB, by performing a targeted PubMed MeSH search and systematically reviewing all relevant studies.
RESULTS
Our search yielded 2,361 studies on gestational tissues including placenta, decidua, myometrium, maternal blood, cervix, fetal membranes (chorion and amnion), umbilical cord, fetal blood, and basal plate. Selecting only those original research studies that measured transcription on a genome-wide scale and reported lists of expressed genetic elements identified 93 gene expression, 21 microRNA, and 20 methylation studies. Although 30 % of all PTB cases are due to medical indications, 76 % of the preterm studies focused on them. In contrast, only 18 % of the preterm studies focused on spontaneous onset of labor, which is responsible for 45 % of all PTB cases. Furthermore, only 23 of the 10,993 unique genetic elements reported to be transcriptionally active were recovered 10 or more times in these 134 studies. Meta-analysis of the 93 gene expression studies across 9 distinct gestational tissues and 29 clinical phenotypes showed limited overlap of genes identified as differentially expressed across studies.
CONCLUSIONS
Overall, profiles of differentially expressed genes were highly heterogeneous both between as well as within clinical subtypes and tissues as well as between studies of the same clinical subtype and tissue. These results suggest that large gaps still exist in the transcriptomic study of specific clinical subtypes as well in the generation of the transcriptional profile of well-studied clinical subtypes; understanding the complex landscape of prematurity will require large-scale, systematic genome-wide analyses of human gestational tissues on both understudied and well-studied subtypes alike.
Topics: DNA Methylation; Female; Gene Expression Profiling; Gene Expression Regulation, Developmental; Genome-Wide Association Study; Humans; Phenotype; Placenta; Pregnancy; Premature Birth; Risk Factors; Term Birth; Transcriptome
PubMed: 26044726
DOI: 10.1186/s12920-015-0099-8 -
Human Reproduction Update 2009Adaptation of the maternal immune response to accommodate the semi-allogeneic fetus is necessary for pregnancy success, and disturbances in maternal tolerance are... (Review)
Review
BACKGROUND
Adaptation of the maternal immune response to accommodate the semi-allogeneic fetus is necessary for pregnancy success, and disturbances in maternal tolerance are implicated in infertility and reproductive pathologies. T regulatory (Treg) cells are a recently discovered subset of T-lymphocytes with potent suppressive activity and pivotal roles in curtailing destructive immune responses and preventing autoimmune disease.
METHODS
A systematic review was undertaken of the published literature on Treg cells in the ovary, testes, uterus and gestational tissues in pregnancy, and their link with infertility, miscarriage and pathologies of pregnancy. An overview of current knowledge on the generation, activation and modes of action of Treg cells in controlling immune responses is provided, and strategies for manipulating regulatory T-cells for potential applications in reproductive medicine are discussed.
RESULTS
Studies in mouse models show that Treg cells are essential for maternal tolerance of the conceptus, and that expansion of the Treg cell pool through antigen-specific and antigen non-specific pathways allows their suppressive actions to be exerted in the critical peri-implantation phase of pregnancy. In women, Treg cells accumulate in the decidua and are elevated in maternal blood from early in the first trimester. Inadequate numbers of Treg cells or their functional deficiency are linked with infertility, miscarriage and pre-eclampsia.
CONCLUSIONS
The potency and wide-ranging involvement of Treg cells in immune homeostasis and disease pathology indicates the considerable potential of these cells as therapeutic agents, raising the prospect of their utility in novel treatments for reproductive pathologies.
Topics: Abortion, Spontaneous; Animals; Cytokines; Dendritic Cells; Female; Humans; Immune Tolerance; Indoleamine-Pyrrole 2,3,-Dioxygenase; Infertility; Male; Mice; Models, Immunological; Ovary; Pregnancy; Pregnancy Complications; Prostaglandins; Semen; Signal Transduction; T-Lymphocytes, Regulatory; Testis; Toll-Like Receptors
PubMed: 19279047
DOI: 10.1093/humupd/dmp004 -
Frontiers in Immunology 2021Several studies report the role of Regulatory T-cells (Tregs) in the pathophysiology of pregnancy adverse outcomes. (Meta-Analysis)
Meta-Analysis
BACKGROUND
Several studies report the role of Regulatory T-cells (Tregs) in the pathophysiology of pregnancy adverse outcomes.
OBJECTIVE
The aim of this systematic review and meta-analysis was to determine whether there is an association between regulatory T cell levels and pregnancy adverse outcomes (PAOs), including pre-eclampsia and preterm birth (PTB).
METHOD
Literature searches were conducted in PubMed/MEDLINE, Embase, and Cochrane CENTRAL databases. Inclusion criteria were original articles (clinical trials, case-control studies and cohort studies) comparing Tregs, sampled from the decidua or maternal blood, in healthy pregnant women women with pre-eclampsia or PTB. The outcome was standardised mean difference (SMD) in Treg numbers. The tau-squared (Tau²), inconsistency index (I²), and chi-squared (χ²) test quantified heterogeneity among different studies. Analyses were performed in RevMan software V.5.4.0 for Mac using a random-effects model with outcome data reported with 95% confidence intervals (CI). This study was prospectively registered with PROSPERO (CRD42020205469). PRISMA guidelines were followed.
RESULTS
From 4,085 unique studies identified, 36 were included in qualitative synthesis, and 34 were included in quantitative synthesis (meta-analysis). In total, there were 1,783 participants in these studies: healthy controls=964, pre-eclampsia=759, PTB=60. Thirty-two studies compared Tregs in healthy pregnant women and women with pre-eclampsia, and 30 of these sampled Tregs from peripheral blood showing significantly higher Treg numbers in healthy pregnancies (SMD; 1.46; 95% CI, 1.03-1.88; I²=92%). Four studies sampled Tregs from the maternal decidua showing higher Tregs in healthy pregnancies (SMD, 0.76; 95% CI, -0.13-1.65; I²=84%). No difference was found in the number of Tregs between early late pre-eclampsia (SMD,-1.17; 95% CI, -2.79-0.44; I²=94%). For PTB, two studies compared Tregs sampled from the peripheral blood with a tendency for higher Tregs in healthy pregnancies but this did not reach significance (SMD, 2.18; 95% CI, -1.34-5.70; I²=96%). Subcohort analysis using Treg analysis (flow cytometry qPCR immunofluorescence tissue staining) showed similar associations.
CONCLUSION
Lower Tregs in pregnancy, sampled from the maternal peripheral blood, are associated with pre-eclampsia. There is a need for further studies to confirm a relationship between low Tregs and PTB. As the precise mechanisms by which Tregs may mediate pre-eclampsia and PTB remain unclear, further fundamental research is necessary to elucidate the underlying processes and highlight the causative link.
SYSTEMATIC REVIEW REGISTRATION
PROSPERO, identifier CRD42020205469.
Topics: Adult; CD4 Lymphocyte Count; Female; Humans; Phenotype; Predictive Value of Tests; Pregnancy; Pregnancy Complications; Pregnancy Outcome; Risk Assessment; Risk Factors; T-Lymphocytes, Regulatory
PubMed: 34777347
DOI: 10.3389/fimmu.2021.737862 -
Journal of Reproductive Immunology Jun 2020Regulatory T cells (Tregs) are essential in tolerizing the maternal immune system toward the semi-allogeneic embryo. In this systematic review, we evaluated the...
Regulatory T cells (Tregs) are essential in tolerizing the maternal immune system toward the semi-allogeneic embryo. In this systematic review, we evaluated the association of levels and function of Tregs in peripheral blood and decidua with recurrent miscarriage (RM), defined as two unexplained miscarriages. We included 18 studies. Ten studies showed a significantly decreased level of Tregs in peripheral blood of non-pregnant women with RM, compared to controls (p < 0.05). In pregnant women with RM, levels of Tregs in the peripheral blood were significantly lower compared to control groups (p = 0.0004), as shown in nine studies. Moreover, seven studies described a decrease of Treg levels in the placenta of pregnant women with RM (p < 0.0001) compared to controls. Accordingly, the median of the relative changes (MRC) between cases and controls in the non-pregnant group (peripheral blood), and the two pregnant groups (peripheral blood and decidua) were -0.18 (-0.27-0), -0.26 (-0.35 to -0.17), and -0.52 (0.63--0.31), respectively. In addition to the assessment of Tregs by phenotype, six out of the 18 included studies investigated the functionality of these cells. These studies showed a lower inhibitory effect of Tregs cells on the proliferation of effector T cells of women with RM compared to fertile women. Also, the expression of IL-10 and TGF-beta was diminished. This systematic review shows that Treg levels and their function are significantly decreased in peripheral blood and decidua of pregnant and non-pregnant women with RM. This underlines the hypothesis that Tregs play a role in the pathogenesis of RM.
Topics: Abortion, Habitual; Female; Forkhead Transcription Factors; Humans; Immune Tolerance; Interleukin-10; Placenta; Pregnancy; T-Lymphocytes, Regulatory; Transforming Growth Factor beta
PubMed: 32199194
DOI: 10.1016/j.jri.2020.103105 -
Fertility and Sterility Jun 2022Implantation is a critical step in the establishment of a successful pregnancy, depending on a complex immune-endocrine dialogue between the developing embryo and... (Meta-Analysis)
Meta-Analysis Review
Implantation is a critical step in the establishment of a successful pregnancy, depending on a complex immune-endocrine dialogue between the developing embryo and maternal endometrium. Research suggests that altered immunity in the maternal decidua results in implantation impairment and failure. Immunomodulatory drugs have, thus, been widely used in assisted conception to aid embryo implantation, despite an absence of consensus on their effectiveness and safety. We conducted a systematic review and meta-analysis of interventional studies investigating the use of immunomodulators in women undergoing assisted reproduction. Evidence was uncertain of an effect for most of the included interventions, owing to heterogeneous findings and a paucity of high-quality studies. For certain patient subgroups, however, the use of specific immunomodulatory therapies may offer some benefit. There is a need for further large randomized controlled trials to corroborate these findings.
Topics: Embryo Implantation; Endometrium; Female; Fertilization in Vitro; Humans; Immunotherapy; Infertility; Pregnancy
PubMed: 35618357
DOI: 10.1016/j.fertnstert.2022.04.015 -
The Cochrane Database of Systematic... Oct 2008Fetal fibronectin (FFN) is an extracellular matrix glycoprotein localized at the maternal-fetal interface of the amniotic membranes, between chorion and decidua, where... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Fetal fibronectin (FFN) is an extracellular matrix glycoprotein localized at the maternal-fetal interface of the amniotic membranes, between chorion and decidua, where it is concentrated in this area between decidua and trophoblast. In normal conditions, FFN is found at very low levels in cervico-vaginal secretions. Levels greater than or equal to 50 ng/mL at or after 22 weeks have been associated with an increased risk of spontaneous preterm birth. In fact, FFN is one of the best predictors of preterm birth in all populations studied so far, and can help selecting which women are at significant risk for preterm birth.
OBJECTIVES
To assess the effectiveness of management based on knowledge of FFN testing results for preventing preterm birth.
SEARCH STRATEGY
We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (January 2008), MEDLINE (1966 to December 2007) and all references in identified articles.
SELECTION CRITERIA
Randomized controlled trials of pregnant women between the gestational ages of 22 and 34 weeks screened with FFN for risk of preterm birth. Studies included are based exclusively on knowledge of FFN results versus no such knowledge, and we have excluded studies including women with only positive or only negative FFN results.
DATA COLLECTION AND ANALYSIS
All four authors assessed studies for inclusion and quality and extracted data.
MAIN RESULTS
We identified 13 trials, of which five were eligible for inclusion. The five included studies randomized 474 women, of which 235 were randomized to knowledge and 249 to no knowledge of FFN.Preterm birth less than 37 weeks was significantly decreased with management based on knowledge of FFN results (15.6%) versus controls without such knowledge (28.6%; risk ratio 0.54; 95% confidence interval 0.34 to 0.87). All other outcomes for which there were available data (preterm birth at less than 34, 32, or 28 weeks; gestational age at delivery; birthweight less than 2500 grams; perinatal death; maternal hospitalization; tocolysis; steroids for fetal lung maturity; and time to evaluate) were similar in the two groups. No other maternal or neonatal outcome was available for meaningful analysis.
AUTHORS' CONCLUSIONS
Although FFN is commonly used in labor and delivery units to help in the management of women with symptoms of preterm labor, currently there is not sufficient evidence to recommend its use. Since this review found an association between knowledge of FFN results and a lower incidence of preterm birth before 37 weeks, further research should be encouraged.
Topics: Biomarkers; Female; Fetus; Fibronectins; Humans; Pregnancy; Premature Birth; Randomized Controlled Trials as Topic
PubMed: 18843732
DOI: 10.1002/14651858.CD006843.pub2 -
American Journal of Reproductive... Dec 2018Oxidative stress (OS) plays a role in uterine tissue remodeling during pregnancy and parturition. While p38 MAPK is an OS-response kinase, a precise functional role is...
Oxidative stress (OS) plays a role in uterine tissue remodeling during pregnancy and parturition. While p38 MAPK is an OS-response kinase, a precise functional role is unknown. Therefore, we conducted a systematic review of literature on p38 MAPK expression, activation, and function in reproductive tissues throughout pregnancy and parturition, published between January 1980 and August 2017, using four electronic databases (Web of Science, PubMed, Medline, and CoCHRANE). We identified 418 reports; 108 were selected for full-text evaluation and 74 were included in final review. p38 MAPK was investigated using feto-maternal primary or immortalized cells, tissue explants, and animal models. Western blot was most commonly used to report phosphorylated (active) p38 MAPK. Human placenta (27), chorioamniotic membranes (14), myometrium (13), decidua (8), and cervix (1) were the studied tissues. p38 MAPK's functions were tissue and gestational age dependent. Isoform specificity was hardly reported. p38 MAPK activity was induced by ROS or proinflammatory cytokines to promote cell signaling linked to cell fate, primed uterus, ripened cervix, and proinflammatory cytokine/chemokine production. In 35 years, reports on p38 MAPK's role during pregnancy and parturition are scarce and current literature is insufficient to provide a comprehensive description of p38 MAPK's mechanistic role during pregnancy and parturition.
Topics: Animals; Disease Models, Animal; Female; Gene Expression Regulation; Genitalia, Female; Humans; Inflammation; Oxidative Stress; Parturition; Pregnancy; Reproduction; Signal Transduction; p38 Mitogen-Activated Protein Kinases
PubMed: 30178469
DOI: 10.1111/aji.13047