microRNA expression in the cervix during pregnancy is associated with length of gestation

The Response of the miRNA Profiles of the Thyroid Gland to the Artificial Photoperiod in Ovariectomized and Estradiol-Treated Ewes

The photoperiod has been considered to be a key environmental factor in sheep reproduction, and some studies have shown that the thyroid gland plays an important role in mammalian reproduction, but the molecular mechanism is still unclear. In this study, we used the artificial-light-controlled, ovariectomized, and estradiol-treated model (OVX + E2 model); healthy and consistent 2-3-year-old Sunite multiparous ewes were collected; and thyroids were collected for testing, combined with RNA-seq technology and bioinformatics analysis, to analyze the effects of different photoperiods (long photoperiod treatment for 42 days, LP42; short photoperiod treatment for 42 days, SP42; SP42 transferred to LP42, SPLP42) on the variations in the miRNA profiles of the thyroid gland. A total of 105 miRNAs were differentially expressed in the thyroid gland, most of which were new miRNAs. Through GO and KEGG enrichment analysis, the results showed that the photoperiod response characteristics of Sunite ewes were affected by Olfactory transduction, Wnt signaling pathways, and Apelin signaling pathways. A different illumination time may have a certain influence on the downstream of these pathways, which leads to the change in animal estrus state. In addition, lncRNA-mRNA-miRNA network analysis revealed the target binding sites of identified miRNAs in DE-circRNA and DE-mRNA, such as Novel_369, Novel_370, Novel_461, and so on. The results of this study will provide some new insights into the function of miRNA and the changes in sheep thyroid glands under different photoperiods.

Recent Advances and Challenges in the Early Diagnosis and Treatment of Preterm Labor

Preterm birth (PTB) is the primary cause of neonatal mortality and long-term disabilities. The unknown mechanism behind PTB makes diagnosis difficult, yet early detection is necessary for controlling and averting related consequences. The primary focus of this work is to provide an overview of the known risk factors associated with preterm labor and the conventional and advanced procedures for early detection of PTB, including multi-omics and artificial intelligence/machine learning (AI/ML)- based approaches. It also discusses the principles of detecting various proteomic biomarkers based on lateral flow immunoassay and microfluidic chips, along with the commercially available point-of-care testing (POCT) devices and associated challenges. After briefing the therapeutic and preventive measures of PTB, this review summarizes with an outlook.

Emerging role of toll-like receptors signaling and its regulators in preterm birth: a narrative review

INTRODUCTION

Despite intensive research, preterm birth (PTB) rates have not decreased significantly in recent years due to a lack of understanding of the underlying causes and insufficient treatment options for PTB. We are committed to finding promising biomarkers for the treatment of PTB.

METHODS

An extensive search of the literature was conducted with MEDLINE/PubMed, and in total, 151 studies were included and summarized in the present review.

RESULTS

Substantial evidence supports that the infection and/or inflammatory cascade associated with infection is an early event in PTB. Toll-like receptor (TLR) is a prominent pattern recognition receptor (PRR) found on both immune and non-immune cells, including fetal membrane cells. The activation of TLR downstream molecules, followed by TLR binding to its ligand, is critical for infection and inflammation, leading to the involvement of the TLR signaling pathway in PTB. TLR ligands are derived from microbial components and molecules released by damaged and dead cells. Particularly, TLR4 is an essential TLR because of its ability to recognize lipopolysaccharide (LPS). In this comprehensive overview, we discuss the role of TLR signaling in PTB, focus on numerous host-derived genetic and epigenetic regulators of the TLR signaling pathway, and cover ongoing research and prospective therapeutic options for treating PTB by inhibiting TLR signaling.

CONCLUSION

This is a critical topic because TLR-related molecules and mechanisms may enable obstetricians to better understand the physiological changes in PTB and develop new treatment and prevention strategies.

Immunomodulation of cytokine signalling at feto-maternal interface by microRNA-223 and -150-5p in infection-associated spontaneous preterm birth

Spontaneous preterm birth (sPTB) is a global health concern and it is the most prevalent cause of infant mortality and morbidity with occurrence rate of 5 - 18% worldwide. Studies suggest infection and infection-driven activation of inflammatory responses are the potential risk factors for sPTB. MicroRNAs (miRNAs) are thought to control the expression of several immune genes, making them crucial components of the intricate immune regulatory network and the dysregulation of miRNAs in placenta has been associated to several pregnancy-related complications. However, studies on possible role of miRNAs in immunomodulation of cytokine signalling in infection-associated sPTB are scarce. Present study aimed to investigate expression/ correlation of a few circulating miRNAs (miR-223, -150-5p, -185-5p, -191-5p), miRNA target genes and associated cytokines in sPTB women found infected with Chlamydia trachomatis/ Mycoplasma hominis/ Ureaplasma urealyticum. Non-heparinized blood and placental sample were collected from 140 sPTB and 140 term women visiting Safdarjung hospital, New Delhi (India) for conducting PCR and RT-PCR for pathogen detection and miRNA/ target gene/ cytokine expression, respectively. Common target genes of differentially expressed miRNAs were obtained from databases. The correlation between select target genes/ cytokines and serum miRNAs was determined by Spearman's rank correlation. 43 sPTB were infected with either pathogen and a significant upregulation of serum miRNAs was observed. However, miR-223 and 150-5p showed maximum fold-change (4.78 and 5.58, respectively) in PTB versus control group. IL-6ST, TGF-β R3 and MMP-14 were important target genes among 454 common targets, whereas, IL-6 and TGF-β were associated cytokines. miR-223 and 150-5p showed significant negative correlation with IL-6ST/ IL-6/ MMP-14 and positive correlation with TGF-β R3/ TGF-β. A significant positive correlation was found between IL-6ST and IL-6, TGF-β R3 and TGF-β. However, miR-185-5p and 191-5p were not significantly correlated. Although post-transcriptional validation is required, yet on the basis of mRNA findings, the study concludes that miR-223 and 150-5p are apparently of clinical importance in regulation of inflammatory processes during infection-associated sPTB.

Cervical microRNA expression and spontaneous preterm birth

BACKGROUND

Preterm birth remains a major public health issue affecting 10% of all pregnancies and increases risks of neonatal morbidity and mortality. Approximately 50% to 60% of preterm births are spontaneous, resulting from preterm premature rupture of membranes or preterm labor. The pathogenesis of spontaneous preterm birth is incompletely understood, and prediction of preterm birth remains elusive. Accurate prediction of preterm birth would reduce infant morbidity and mortality through targeted patient referral to hospitals equipped to care for preterm infants. Two previous studies have analyzed cervical microRNAs in association with spontaneous preterm birth and the length of gestation, but the extent to which microRNAs serve as predictive biomarkers remains unknown.

OBJECTIVE

This study aimed to examine associations between cervical microRNA expression and spontaneous preterm birth, with the specific goal of identifying a subset of microRNAs that predict spontaneous preterm birth.

STUDY DESIGN

We performed a prospective, nested, case-control study of 25 cases with spontaneous preterm birth and 49 term controls. Controls were matched to cases in a 2:1 ratio on the basis of age, parity, and self-identified race. Cervical swabs were collected at a mean gestational age of 17.1 (4.8) weeks of gestation, and microRNAs were analyzed using a quantitative polymerase chain reaction array. Normalized microRNA expression was compared between cases and controls, and a false discovery rate of 0.2 was applied to account for multiple comparisons. Histopathologic analysis of slides of cervical swab samples was performed to quantify leukocyte burden for adjustment in conditional regression models. We explored the use of Relief-based unsupervised identification of top microRNAs and support vector machines to predict spontaneous preterm birth. We performed microRNA enrichment analysis to explore potential biologic targets and pathways in which up-regulated microRNAs might be involved.

RESULTS

Of the 754 microRNAs on the polymerase chain reaction array, 346 were detected in ≥75% of participants' cervical swabs. Average cervical microRNA expression was significantly higher in cases of spontaneous preterm birth than in controls (P=.01). There were 95 significantly up-regulated individual microRNAs (>2-fold change) in cases of subsequent spontaneous preterm birth compared with term controls (P<.05; q<0.2). Notably, miR-143, miR-30e-3p, and miR-199b were all significantly up-regulated, which is consistent with the 1 previous study of cervical microRNA and spontaneous preterm birth. A Relief-based, novel variable (feature) selection machine learning approach had low-to-moderate prediction accuracy, with an area under the receiver operating curve of 0.71. Enrichment analysis revealed that identified microRNAs may modulate inflammatory cell signaling.

CONCLUSION

In this prospective nested case-control study of cervical microRNA expression and spontaneous preterm birth, we identified a global increase in microRNA expression and up-regulation of 95 distinct microRNAs in association with subsequent spontaneous preterm birth. Larger and more diverse studies are required to determine the ability of microRNAs to accurately predict spontaneous preterm birth, and mechanistic work to facilitate development of novel therapeutic interventions to prevent spontaneous preterm birth is warranted.

Transcriptomic analysis of the human placenta reveals trophoblast dysfunction and augmented Wnt signalling associated with spontaneous preterm birth

Preterm birth (PTB) is the leading cause of death in under-five children. Worldwide, annually, over 15 million babies are born preterm and 1 million of them die. The triggers and mechanisms of spontaneous PTB remain largely unknown. Most current therapies are ineffective and there is a paucity of reliable predictive biomarkers. Understanding the molecular mechanisms of spontaneous PTB is crucial for developing better diagnostics and therapeutics. To address this need, we conducted RNA-seq transcriptomic analysis, qRT-PCR and ELISA on fresh placental villous tissue from 20 spontaneous preterm and 20 spontaneous term deliveries, to identify genes and signalling pathways involved in the pathogenesis of PTB. Our differential gene expression, gene ontology and pathway analysis revealed several dysregulated genes (including OCLN, OPTN, KRT7, WNT7A, RSPO4, BAMBI, NFATC4, SLC6A13, SLC6A17, SLC26A8 and KLF8) associated with altered trophoblast functions. We identified dysregulated Wnt, oxytocin and cellular senescence signalling pathways in preterm placentas, where augmented Wnt signalling could play a pivotal role in the pathogenesis of PTB due to its diverse biological functions. We also reported two novel targets (ITPR2 and MYLK2) in the oxytocin signalling pathways for further study. Through bioinformatics analysis on DEGs, we identified four key miRNAs, - miR-524-5p, miR-520d-5p, miR-15a-5p and miR-424-5p - which were significantly downregulated in preterm placentas. These miRNAs may have regulatory roles in the aberrant gene expressions that we have observed in preterm placentas. We provide fresh molecular insight into the pathogenesis of spontaneous PTB which may drive further studies to develop new predictive biomarkers and therapeutics.

Biomarkers for Preterm Delivery

Preterm birth occurring before the thirty-seventh gestational week complicates 4.5%-18% of pregnancies worldwide. The pathogenesis of spontaneous preterm delivery is not fully understood. Among the factors held to be responsible for its pathogenesis, the most emphasized is the inflammatory process. Studies in terms of the prediction of preterm delivery are basically divided into 3 categories: 1) Prediction in pregnant women who are asymptomatic and without risk factors, 2) Prediction in pregnant women who are asymptomatic and have risk factors, 3) Prediction in symptomatic pregnant women who have threatened preterm labour. In this chapter, the topic of biomarkers in relation to preterm delivery is discussed. The most commonly used markers in published studies are fetal fibronectin, cervical pIGFBP-1 and cervical length measurement by transvaginal ultrasound. For prediction in symptomatic pregnant women applying to the hospital with threatened preterm labour, the markers used are fetal fibronection, insulin-like growth factors (IGFs) and inflammatory markers. Preterm labour prediction with markers checked in the first and second trimesters are fetal fibronection, insulin-like growth factors (IGFs), micro RNAs, progesterone, circulating microparticles (CMPs), inflammatory markers, matrix metalloproteinases, aneuploidy syndrome screening test parameters and other hormones.

Elevated miR-29c-5p Expression in Nipple Aspirate Fluid Is Associated with Extremely High Mammographic Breast Density

Simple Summary

High mammographic density is a known risk factor for breast cancer. However, the underlying mechanisms of high mammographic density development and breast cancer are unknown. MicroRNAs are potential biomarkers indicative of carcinogenesis and can be assessed in nipple aspirate fluid. We used nipple aspirate fluid from women with very low and extremely high mammographic density to examine differences in expression of multiple miRNAs between both extremes in the spectrum of mammographic density. We found that hsa-miR-29c-5p was upregulated in an extremely high mammographic density context and potential targets were identified that might provide clues of the relationship between high mammographic density and breast cancer risk. Understanding the relationship between high mammographic density and breast cancer is of great value for early breast cancer diagnosis and treatment. With our research we provide new insight into this relationship and further research could determine the effects of dysregulated hsa-miR-29c-5p on the identified candidate targets.

Abstract

High mammographic density (MD) is associated with an increased risk of breast cancer, however the underlying mechanisms are largely unknown. This research aimed to identify microRNAs (miRNAs) that play a role in the development of extremely dense breast tissue. In the discovery phase, 754 human mature miRNAs were profiled in 21 extremely high MD- and 20 very low MD-derived nipple aspirate fluid (NAF) samples from healthy women. In the validation phase, candidate miRNAs were assessed in a cohort of 89 extremely high MD and 81 very low MD NAF samples from healthy women. Independent predictors of either extremely high MD or miRNA expression were identified by logistic regression and linear regression analysis, respectively. mRNA targets and pathways were identified through miRTarBase, TargetScan, and PANTHER pathway analysis. Statistical analysis identified four differentially expressed miRNAs during the discovery phase. During the validation, linear regression (p = 0.029; fold change = 2.10) and logistic regression (p = 0.048; odds ratio = 1.38) showed that hsa-miR-29c-5p was upregulated in extremely high MD-derived NAF. Identified candidate mRNA targets of hsa-miR-29c-5p are CFLAR, DNMT3A, and PTEN. Further validation and exploration of targets and downstream pathways of has-miR-29c-5p will provide better insight into the processes involved in the development of high MD and in the associated increased risk of breast cancer.

Prenatal and early childhood critical windows for the association of nephrotoxic metal and metalloid mixtures with kidney function

INTRODUCTION

As renal development and maturation processes begin in utero and continue through early childhood, sensitive developmental periods arise during which metal exposures can program subclinical nephrotoxicity that manifests later in life. We used novel dentine biomarkers of established nephrotoxicants including arsenic (As), cadmium (Cd), lead (Pb), chromium (Cr), and lithium (Li), and their mixtures, to identify critical windows of exposure-associated kidney function alterations in preadolescents.

METHODS

Participants included 353 children in the Programming Research in Obesity Growth, Environment and Social Stressors (PROGRESS) longitudinal birth cohort study based in Mexico City. Estimated glomerular filtration rate (eGFR) was assessed in 8-12 year old children using serum cystatin C measures. Pre- and postnatal metal(loid) concentrations were assessed in weekly increments by analyzing deciduous teeth with laser ablation-inductively coupled plasma-mass spectrometry. We used reverse distributed lag models (rDLMs) and lagged Weighted Quantile Sum (L-WQS) regression to examine time-varying associations between weekly perinatal metal(loid) exposure or metal(loid) mixtures and preadolescent eGFR while adjusting for age, sex, BMI z-score, SES and prenatal tobacco smoke exposure.

RESULTS

We identified a critical window of susceptibility to Pb exposure, in the late 3rd trimester (5 weeks prior to birth) during which higher Pb exposure was associated with children's increased eGFR. When all elements were assessed as a mixture, we identified late 2nd/early 3rd trimester (weeks 8-17 of gestation) as a window of vulnerability associated with decreased eGFR, with Li and Cr contributing the greatest weights to the association. When stratified by sex, we observed stronger effects among boys than girls.

CONCLUSIONS

Using tooth-matrix biomarkers, we identified discrete developmental exposure windows wherein Pb and metal(loid) mixtures were associated with altered preadolescent kidney function.

Systematic review of preterm birth multi-omic biomarker studies

Preterm birth (PTB) is one of the leading causes of deaths in infants under the age of five. Known risk factors of PTB include genetic factors, lifestyle choices or infection. Identification of omic biomarkers associated with PTB could aid clinical management of women at high risk of early labour and thereby reduce neonatal morbidity. This systematic literature review aimed to identify and summarise maternal omic and multi-omic (genomics, transcriptomics, proteomics and metabolites) biomarker studies of PTB. Original research articles were retrieved from three databases: PubMed, Web of Science and Science Direct, using specified search terms for each omic discipline. PTB studies investigating genomics, transcriptomics, proteomics or metabolomics biomarkers prior to onset of labour were included. Data were collected and reviewed independently. Pathway analyses were completed on the biomarkers from non-targeted omic studies using Reactome pathway analysis tool. A total of 149 omic studies were identified; most of the literature investigated proteomic biomarkers. Pathway analysis identified several cellular processes associated with the omic biomarkers reported in the literature. Study heterogeneity was observed across the research articles, including the use of different gestation cut-offs to define PTB. Infection/inflammatory biomarkers were identified across majority of papers using a range of targeted and non-targeted approaches.

Downregulation of miR-21 is Involved in the Pathogenesis of Infection-Induced Preterm Birth by Targeting NF-κB

Infection-induced preterm birth (PTB) is contributing to the main factors of increased maternal and fetal morbidity and mortality. Infections and inflammation are often accompanied by histologic chorioamnionitis. Recently, several studies have uncovered that miR-21 and NF-κB are associated with pathological processes of pregnant women. However, the role of miR-21 in infection-induced PTB remains unclear. This study aimed to determine whether miR-21 is involved in the pathogenesis of infection-induced PTB by regulating NF-κB. In this study, we found that the expression of miR-21 was significantly decreased in placental tissues of lipopolysaccharides (LPS)-induced infectious PTB mice model, accompanied by the increase of NF-κB, IL-6, and TNF-α (P < 0.05). Luciferase reporter gene assays showed that NF-κB was a validated target of miR-21. Furthermore, cell transfection experiments showed that miR-21 overexpression significantly decreased NF-κB mRNA expression compared with the miR-control group and blank group. Conversely, miR-21 inhibitor can enhance NF-κB mRNA expression. After the treatment of miR-21 mimics, miR-21 expression was obviously increased compared with the LPS group, accompanied by the decrease of NF-κB, TNF-α, and IL-6 mRNA expression (P < 0.05). What's more, miR-21 expression was negatively correlated with NF-κB (r=-0.87, P < 0.01). Overall, the study findings indicate that miR-21 may contribute to the pathogenesis of infection-induced PTB by upregulating the target NF-κB and that miR-21 may be a new potential therapeutic target for infection-induced PTB.

Early childhood fluoride exposure and preadolescent kidney function

BACKGROUND

Early-life renal maturation is susceptible to nephrotoxic environmental chemicals. Given the widespread consumption of fluoride and the global obesity epidemic, our main aim was to determine whether childhood fluoride exposure adversely affects kidney function in preadolescence, and if adiposity status modifies this association.

METHODS

Our study included 438 children from the PROGRESS cohort. Urinary fluoride (uF) was assessed at age 4 by diffusion analysis; outcomes studied included estimated glomerular filtration rate (eGFR), blood urea nitrogen (BUN), selected kidney proteins and blood pressure measured at age 8-12 years. We modeled the relationship between uF and outcomes, and adjusted for body mass index (BMI), age, sex, and socioeconomic status.

RESULTS

The median uF concentration was 0.67 μg/mL. We observed null associations between 4-year uF and preadolescent eGFR, although effect estimates were in the expected inverse direction. A single unit increase in ln-transformed uF was associated with a 2.2 mL/min decrease in cystatin C-based eGFR (95% CI: 5.8, 1.4; p = 0.23). We observed no evidence of sex-specific effects or effect modification by BMI status. Although uF was not associated with BMI, among children with obesity, we observed an inverse association (β: 4.8; 95% CI: 10.2, 0.6; p = 0.08) between uF and eGFR.

CONCLUSIONS

Low-level fluoride exposure in early childhood was not associated with renal function in preadolescence. However, given the adverse outcomes of chronic fluoride consumption it is possible that the preadolescent age was too young to observe any effects. Longitudinal follow-up in this cohort and others is an important next step.

Critical windows of perinatal particulate matter (PM2.5) exposure and preadolescent kidney function

Air pollution exposure, especially particulate matter ≤2.5 μm in diameter (PM2.5), is associated with poorer kidney function in adults and children. Perinatal exposure may occur during susceptible periods of nephron development. We used distributed lag nonlinear models (DLNMs) to examine time-varying associations between early life daily PM2.5 exposure (periconceptional through age 8 years) and kidney parameters in preadolescent children aged 8-10 years. Participants included 427 mother-child dyads enrolled in the PROGRESS birth cohort study based in Mexico City. Daily PM2.5 exposure was estimated at each participant's residence using a validated satellite-based spatio-temporal model. Kidney function parameters included estimated glomerular filtration rate (eGFR), serum cystatin C, and blood urea nitrogen (BUN). Models were adjusted for child's age, sex and body mass index (BMI) z-score, as well as maternal education, indoor smoking report and seasonality (prenatal models were additionally adjusted for average first year of life PM2.5 exposure). We also tested for sex-specific effects. Average perinatal PM2.5 was 22.7 μg/m3 and ranged 16.4-29.3 μg/m3. Early pregnancy PM2.5 exposures were associated with higher eGFR in preadolescence. Specifically, we found that PM2.5 exposure between weeks 1-18 of gestation was associated with increased preadolescent eGFR, whereas exposure in the first 14 months of life after birth were associated with decreased eGFR. Specifically, a 5 μg/m3 increase in PM2.5 during the detected prenatal window was associated with a cumulative increase in eGFR of 4.44 mL/min/1.732 (95%CI: 1.37, 7.52), and during the postnatal window we report a cumulative eGFR decrease of -10.36 mL/min/1.732 (95%CI: -17.68, -3.04). We identified perinatal windows of susceptibility to PM2.5 exposure with preadolescent kidney function parameters. Follow-up investigating PM2.5 exposure with peripubertal kidney function trajectories and risk of kidney disease in adulthood will be critical.

Genome and transcriptome profiling of spontaneous preterm birth phenotypes

Preterm birth (PTB) occurs before 37 weeks of gestation. Risk factors include genetics and infection/inflammation. Different mechanisms have been reported for spontaneous preterm birth (SPTB) and preterm birth following preterm premature rupture of membranes (PPROM). This study aimed to identify early pregnancy biomarkers of SPTB and PPROM from the maternal genome and transcriptome. Pregnant women were recruited at the Liverpool Women’s Hospital. Pregnancy outcomes were categorised as SPTB, PPROM (≤ 34 weeks gestation, n = 53), high-risk term (HTERM, ≥ 37 weeks, n = 126) or low-risk (no history of SPTB/PPROM) term (LTERM, ≥ 39 weeks, n = 188). Blood samples were collected at 16 and 20 weeks gestation from which, genome (UK Biobank Axiom array) and transcriptome (Clariom D Human assay) data were acquired. PLINK and R were used to perform genetic association and differential expression analyses and expression quantitative trait loci (eQTL) mapping. Several significant molecular signatures were identified across the analyses in preterm cases. Genome-wide significant SNP rs14675645 (ASTN1) was associated with SPTB whereas microRNA-142 transcript and PPARG1-FOXP3 gene set were associated with PPROM at week 20 of gestation and is related to inflammation and immune response. This study has determined genomic and transcriptomic candidate biomarkers of SPTB and PPROM that require validation in diverse populations.

miR-21 differentially regulates IL-1β and IL-10 expression in human decidual cells infected with streptococcus B

Intrauterine infections caused by bacteria like group B streptococcus (GBS) and the subsequent activation of the maternal inflammatory response have been long suspected to be the underlying cause of preterm labor. The inflammatory network triggered by maternal decidua has been widely described and includes the secretion of pro- and anti-inflammatory cytokines as IL-1β and IL-10; however, the mechanisms that regulate their secretion have not been completely elucidated. MicroRNAs (miRNAs) are critical modulators of the inflammatory response by regulating cytokine expression in several cell types. Here, we explored the role of miR-21 in the expression of IL-1β and IL-10 in human decidual stromal cells (DSCs) exposed in vitro to GBS. We observed that IL1B and IL10 expression at the mRNA level was increased in DSCs after GBS infection. IL-10 but not IL-1β secretion was detected in the culture supernatants. We found a higher miR-21 expression (22-fold) in infected DSCs as compared with non-infected cells. miR-21 functional analysis revealed that DSCs transfected with an antagomiR vs. miR-21 significantly increased the secretion of IL-1β but decreased that of IL-10 in DSCs cells infected with GBS. Our results suggest that miR-21 participates in balancing the inflammatory response in infected decidua through at least IL-1β and IL-10 regulation. This is the first study attributing a functional role of miR-21 in the regulation of key molecules involved in the inflammatory response in infected DSCs, providing new insights into the epigenetic control of human decidual inflammation.

Role of epigenetics in parturition and preterm birth

Preterm birth occurs worldwide and is associated with high morbidity, mortality, and economic cost. Although several risk factors associated with parturition and preterm birth have been identified, mechanisms underlying this syndrome remain unclear, thereby limiting the implementation of interventions for prevention and management. Known triggers of preterm birth include conditions related to inflammatory and immunological pathways, as well as genetics and maternal history. Importantly, epigenetics, which is the study of heritable phenotypic changes that occur without alterations in the DNA sequence, may play a role in linking social and environmental risk factors for preterm birth. Epigenetic approaches to the study of preterm birth, including analyses of the effects of microRNAs, long non-coding RNAs, DNA methylation, and histone modification, have contributed to an improved understanding of the molecular bases of both term and preterm birth. Additionally, epigenetic modifications have been linked to factors already associated with preterm birth, including obesity and smoking. The prevention and management of preterm birth remains a challenge worldwide. Although epigenetic analysis provides valuable insights into the causes and risk factors associated with this syndrome, further studies are necessary to determine whether epigenetic approaches can be used routinely for the diagnosis, prevention, and management of preterm birth.

Clinical and immunological aspects of microRNAs in neonatal sepsis

Neonatal sepsis constitutes a highly relevant public health challenge and is the most common cause of infant morbidity and mortality worldwide. Recent studies have demonstrated that during infection epigenetic changes may occur leading to reprogramming of gene expression. Post-transcriptional regulation by short non-coding RNAs (e.g., microRNAs) have recently acquired special relevance because of their role in the regulation of the pathophysiology of sepsis and their potential clinical use as biomarkers. ~22-nucleotide of microRNAs are not only involved in regulating multiple relevant cellular and molecular functions, such as immune cell function and inflammatory response, but have also been proposed as good candidates as biomarkers in sepsis. Nevertheless, establishing clinical practice guidelines based on microRNA patterns as biomarkers for diagnosis and prognosis in neonatal sepsis has yet to be achieved. Given their differential expression across tissues in neonates, the release of specific microRNAs to blood and their expression pattern can differ compared to sepsis in adult patients. Further in-depth research is necessary to fully understand the biological relevance of microRNAs and assess their potential use in clinical settings. This review provides a general overview of microRNAs, their structure, function and biogenesis before exploring their potential clinical interest as diagnostic and prognostic biomarkers of neonatal sepsis. An important part of the review is focused on immune and inflammatory aspects of selected microRNAs that may become biomarkers for clinical use and therapeutic intervention.

Prenatal urinary concentrations of phenols and risk of preterm birth: exploring windows of vulnerability

OBJECTIVE

To explore windows of vulnerability to prenatal urinary phenol concentrations and preterm birth.

DESIGN

Prospective cohort.

SETTING

A large fertility center in Boston, Massachusetts.

PATIENT(S)

A total of 386 mothers who sought fertility treatment and gave birth to a singleton between 2005 and 2018.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Singleton live birth with gestational age <37 completed weeks.

RESULT(S)

Compared with women with non-preterm births, urinary bisphenol A (BPA) concentrations were higher across gestation among women with preterm births, particularly during mid-to-late pregnancy and among those with female infants. Second trimester BPA concentrations were associated with preterm birth (Risk Ratio [RR] 1.24; 95%CI: 0.92, 1.69), which was primarily driven by female (RR 1.40; 95%CI: 1.04, 1.89) and not male (RR 0.85; 95%CI 0.50, 1.46) infants. First trimester paraben concentrations were also associated with preterm birth (RR 1.17; 95%CI: 0.94, 1.46) and similarly the association was only observed for female (RR 1.46; 95% CI: 1.10, 1.94) and not male infants (RR 0.94; 95%CIC: 0.72, 1.23). First trimester urinary bisphenol S concentrations showed a suggested risk of preterm birth (RR 1.25; 95%CI: 0.82, 1.89), although the small case numbers precluded sex-specific examination.

CONCLUSION(S)

We found preliminary evidence of associations between mid-to-late pregnancy BPA and early pregnancy paraben concentrations with preterm birth among those with female infants only. Preterm birth risk may be compound, sex, and window specific. Given the limited sample size of this cohort, results should be confirmed in larger studies, including fertile populations.

Prenatal blood lead levels and reduced preadolescent glomerular filtration rate: Modification by body mass index

BACKGROUND

For the developing kidney, the prenatal period may represent a critical window of vulnerability to environmental insults resulting in permanent nephron loss. Given that the majority of nephron formation is complete in the 3rd trimester, we set out to test whether 1) prenatal lead exposure is associated with decreased preadolescent kidney function and 2) whether preadolescent obesity acts synergistically with early life lead exposure to reduce kidney function.

METHODS

Our study included 453 mother-child pairs participating in the PROGRESS birth cohort. We assessed prenatal blood lead levels (BLLs) in samples collected in the 2nd and 3rd trimesters and at delivery, as well as tibial and patellar bone lead measures assessed one-month postpartum. Preadolescent estimated glomerular filtration rate (eGFR) was derived from serum levels of creatinine and/or cystatin C measured at age 8-12 years. We applied linear regression to assess the relationship between prenatal bone and BLL with preadolescent eGFR, and adjusted for covariates including age, sex, BMI z-score, indoor tobacco smoke exposure, and socioeconomic status. We also examined sex-specific associations and tested for effect modification by BMI status.

RESULTS

We observed null associations between prenatal lead exposure and eGFR. However, in interaction analyses we found that among overweight children, there was an inverse association between BLL (assessed at 2nd and 3rd trimester and at delivery) and preadolescent eGFR. For example, among overweight participants, a one ln-unit increase in 2nd trimester BLL was associated with a 10.5 unit decrease in cystatin C-based eGFR (95% CI: -18.1, -2.8; p = 0.008). Regardless of lead exposure, we also observed null relationships between BMI z-score and eGFR overall, as well as among overweight participants. However, among participants with preadolescent obesity, we observed a significant 5.9-unit decrease in eGFR. We observed no evidence of sex-specific effects.

CONCLUSIONS

Our findings, if confirmed in other studies, suggest a complex interplay between the combined adverse effects of adiposity and perinatal lead exposure as they relate to adolescent kidney function. Future studies will assess kidney function and adiposity trajectories through adolescence to better understand environmental risk factors for kidney function decline.

Extracellular vesicle microRNA in early versus late pregnancy with birth outcomes in the MADRES study

Circulating miRNA may contribute to the development of adverse birth outcomes. However, few studies have investigated extracellular vesicle (EV) miRNA, which play important roles in intercellular communication, or compared miRNA at multiple time points in pregnancy. In the current study, 800 miRNA were profiled for EVs from maternal plasma collected in early (median: 12.5 weeks) and late (median: 31.8 weeks) pregnancy from 156 participants in the MADRES Study, a health disparity pregnancy cohort. Associations between miRNA and birth weight, birth weight for gestational age (GA), and GA at birth were examined using covariate-adjusted robust linear regression. Differences by infant sex and maternal BMI were also investigated. Late pregnancy measures of 13 miRNA were associated with GA at birth (P_FDR<0.050). Negative associations were observed for eight miRNA (miR-4454+ miR-7975, miR-4516, let-7b-5p, miR-126-3p, miR-29b-3p, miR-15a-5p, miR-15b-5p, miR-19b-3p) and positive associations for five miRNA (miR-212-3p, miR-584-5p, miR-608, miR-210-3p, miR-188-5p). Predicted target genes were enriched (P_FDR<0.050) in pathways involved in organogenesis and placental development. An additional miRNA (miR-107), measured in late pregnancy, was positively associated with GA at birth in infants born to obese women (P_FDR for BMI interaction = 0.011). In primary analyses, the associations between early pregnancy miRNA and birth outcomes were not statistically significant (P_FDR≥0.05). However, sex-specific associations were observed for early pregnancy measures of 37 miRNA and GA at birth (P_FDR for interactions<0.050). None of the miRNA were associated with fetal growth measures (P_FDR≥0.050). Our findings suggest that EV miRNA in both early and late pregnancy may influence gestational duration.

Racial and ethnic representation in epigenomic studies of preterm birth: a systematic review

Aim: We conducted a systematic review evaluating race/ethnicity representation in DNA methylomic studies of preterm birth. Data sources: PubMed, EMBASE, CINHAL, Scopus and relevant citations from 1 January 2000 to 30 June 2019. Study appraisal & synthesis methods: Two authors independently identified abstracts comparing DNA methylomic differences between term and preterm births that included race/ethnicity data. Results: 16 studies were included. Black and non-Hispanic Black deliveries were well represented (28%). However, large studies originating from more than 95% White populations were excluded due to unreported race/ethnicity data. Most studies were cross-sectional, allowing for reverse causation. Most studies were also racially/ethnically homogeneous, preventing direct comparison of DNA methylomic differences across race/ethnicities. Conclusion: In DNA methylomic studies, Black women and infants were well represented. However, the literature has limitations and precludes drawing definitive conclusions.

Pregnancy-associated changes in cervical noncoding RNA

Aim: To identify pregnancy-associated changes in cervical noncoding RNA (ncRNA), including miRNA and long noncoding RNA (lncRNA), and their potential effects on biologic processes. Materials & methods: We enrolled 21 pregnant women with term deliveries (≥37 weeks' gestation) in a prospective cohort and collected cervical swabs before 28 weeks' gestation. We enrolled 21 nonpregnant controls. We analyzed miRNA, lncRNA and mRNA expression, applying a Bonferroni correction. Results: Five miRNA and three lncRNA were significantly differentially (>twofold change) expressed. Putative miRNA targets are enriched in genes mediating organogenesis, glucocorticoid signaling, cell adhesion and ncRNA machinery. Conclusion: Differential cervical ncRNA expression occurs in the setting of pregnancy. Gene ontology classification reveals biological pathways through which miRNA may play a biologic role in normal pregnancy physiology.

Length of gestation and birth weight are associated with indices of combined kidney biomarkers in early childhood

Infants born prematurely or with low birth weights are more susceptible to kidney dysfunction throughout their lives. Multiple proteins measured in urine are noninvasive biomarkers of subclinical kidney damage, but few studies have examined the joint effects of multiple biomarkers. We conducted an exploratory study of 103 children in the Programing Research in Obesity, Growth, Environment, and Social Stressors (PROGRESS) longitudinal birth cohort, and measured nine proteins selected a priori in banked spot urine samples collected at ages 4-6. The goal of our study was to explore the combined effects of kidney damage biomarkers previously associated with birth outcomes. To do this, we generated kidney biomarker indices using weighted quantile sum regression and assessed associations with length of gestation or birth weight. A decile increase in each kidney biomarker index was associated with 2-day shorter gestations (β = -2.0, 95% CI: -3.2, -0.9) and 59-gram lower birth weights (β = -58.5, 95% CI: -98.3, -18.7), respectively. Weights highlighting the contributions showed neutrophil gelatinase-associated lipocalin (NGAL) (60%) and osteopontin (19%) contributed most to the index derived for gestational age. NGAL (66%) and beta-2-microglobulin (10%) contributed most to the index derived for birth weight. Joint analyses of multiple kidney biomarkers can provide integrated measures of kidney dysfunction and improved statistical assessments compared to biomarkers assessed individually. Additionally, shorter gestations and lower birth weights may contribute to subclinical kidney damage measurable in childhood.

MicroRNA-548 regulates high mobility group box 1 expression in patients with preterm birth and chorioamnionitis

High mobility group box 1 (HMGB1) is a prototypic alarmin and plays an important role in the pathogenesis of inflammatory process in spontaneous preterm birth. This study was conducted to compare the levels of HMGB1 in amniotic fluid and amnion membranes in women with chorioamnionitis/intra-amniotic inflammation to the levels in healthy controls. We also aimed to elucidate the involvement of microRNA-548 (miR-548) in regulating HMGB1 expression and its function in human amniotic epithelial cells (hAECs). A bioinformatics analysis predicted the binding of HMGB1 by the miR-548 cluster. A repressed and forced expression assay in hAECs was performed to investigate the causal relationship between the miR-548 cluster and HMGB1. The levels of HMGB1 in amniotic fluid and amnion membranes were significantly higher in patients with intra-amniotic inflammation/chorioamnionitis than in those without inflammation. The miR-548 was significantly under-expressed in amnion membranes from patients with chorioamnionitis than in normal term controls. Repressed expression of miR-548 up-regulated HMGB1 expression in hAECs and increased its release from hAECs. Moreover, forced expression of miR-548 suppressed HMGB1 and inflammatory cytokines in hAECs, which increased when treated with lipopolysaccharide. These results suggest miR-548 can alter the inflammatory responses in hAECs, and might be involved in the pathogenesis of preterm birth by regulating HMGB1.

Microbial supernatants from Mobiluncus mulieris, a bacteria strongly associated with spontaneous preterm birth, disrupts the cervical epithelial barrier through inflammatory and miRNA mediated mechanisms

Recent human clinical studies have identified Mobiluncus mulieris, a fastidious strict anaerobic bacterium present in the cervicovaginal (CV) space, as being strongly associated with spontaneous preterm birth (sPTB). However, the molecular mechanisms that underlie this association remain unknown. As disruption of the cervical epithelial barrier has been shown to contribute to the premature cervical remodeling that precedes sPTB, we hypothesize that M. mulieris, a microbe strongly associated with sPTB in humans, has the ability to alter cervical epithelial function. We investigated if bacteria-free supernatants of M. mulieris were able to disrupt the cervical epithelial barrier through immunological and epigenetic based mechanisms in an in vitro model system. Ectocervical cells were treated with supernatant from cultured M. mulieris and epithelial cell permeability, immune cytokines and microRNAs (miRNAs) were investigated. M. mulieris supernatant significantly increased cell permeability and the expression of two inflammatory mediators associated with cervical epithelial breakdown, IL-6 and IL-8. Moreover, treatment of the ectocervical cells with the M. mulieris supernatant also increased the expression of miRNAs that have been associated with either sPTB or a shorter gestational length in humans. Collectively, these results suggest that M. mulieris induces molecular and functional changes in the cervical epithelial barrier thought to contribute to the pathogenesis of sPTB, which allows us to hypothesize that targeting CV bacteria such as M. mulieris could provide a therapeutic opportunity to reduce sPTB rates.

Prenatal salivary sex hormone levels and birth-weight-for-gestational age

OBJECTIVE

To determine whether prenatal sex hormones from maternal saliva are associated with birth-weight-for-gestational age.

STUDY DESIGN

We measured salivary progesterone, testosterone, estradiol, dehydroepiandrosterone (DHEA), and cortisone in 504 pregnant women in a Mexico City cohort. We performed linear and modified Poisson regression to examine associations of log-transformed hormones with birth-weight-for-gestational age z-scores and the risk of small-for-gestational age (SGA) and large-for-gestational age (LGA) adjusting for maternal age, sex, BMI, parity, smoking, education, and socioeconomic status.

RESULTS

In total, 15% of infants were SGA and 2% were LGA. Each interquartile range increment in testosterone/estradiol ratio was associated with a 0.12 decrement in birth-weight-for-gestational age z-score (95% CI: -0.27 to -0.02) and a 50% higher risk of SGA versus appropriate-for-gestational age (AGA) (95% CI: 1.13-1.99).

CONCLUSION

Higher salivary testosterone/estradiol ratios may affect fetal growth, and identifying the predictors of hormone levels may be important to optimizing fetal growth.

First Trimester Circulating MicroRNA Biomarkers Predictive of Subsequent Preterm Delivery and Cervical Shortening

Preterm birth (PTB) is the leading cause of infant death and disability worldwide. The onset of preterm uterine contractions is preceded by asymptomatic cervical remodelling and ripening, which can be seen on trans-vaginal ultrasound as cervical shortening. This study aimed to identify plasma miRNA biomarkers that predict preterm birth and/or cervical shortening. We collected serial plasma samples from pregnant women prospectively from 12 to 22 weeks gestation. The nCounter miRNA assay was used to identify differentially expressed miRNAs associated with spontaneous PTB and/or cervical shortening (n = 16 term no short, n = 13 preterm, n = 24 short). Predictive values of the miRNA biomarkers were confirmed in an independent validation cohort consisting of 96 women who delivered at term, 14 preterm and 21 early cervical shortening at <20 weeks gestation. Nine miRNAs (hsa-let-7a-5p, hsa-miR-374a-5p, hsa-miR-15b-5p, hsa-miR-19b-3p, hsa-miR-23a-3p, hsa-miR-93-5p, hsa-miR-150-5p, hsa-miR-185-5p and hsa-miR-191-5p) were differentially expressed (P < 0.001) in women subsequently experiencing PTB or cervical shortening. Hsa-miR-150-5p had the strongest ability to predict PTB (AUC = 0.8725) and cervical shortening (AUC = 0.8514). Plasma miRNAs in the first trimester can predict PTB and cervical shortening in women at risk of preterm delivery. This is a key period in pregnancy when early identification of PTB risk allows time to deliver outcome-modifying interventions.

Predicting the target genes of miRNAs in preterm via targetscore algorithm

Compared with normal neonates, preterm infants have an immature immune system which causes them to have a higher morbidity rate and even death. In order to reduce the mortality of newborns, we need to find the target genes which affect the preterm and understand their mechanism. It has been verified that microRNA (miRNA)-200 and miRNA-182 are closely related to the incidence of preterm. Therefore, it is significant to predict the target genes which are regulated by them for further understanding the mechanism of preterm. We chose the targetscore method for calculating the variational Bayesian-Gaussian mixture model (VB-GMM) as the target genes prediction method. It is designed for condition-specific target predictions and not limited to predict conserved genes, so the results are more accurate than previous sequence-based target prediction algorithms. In this study, our major contribution is to predict the target mRNAs of the chosen miRNAs with the gene expression profiles and a new method, which can effectively improve the accuracy of the prediction.

Environmental Contaminants Exposure and Preterm Birth: A Systematic Review

Preterm birth is an obstetric condition associated with a high risk of infant mortality and morbidities in both the neonatal period and later in life, which has also a significant public health impact because it carries an important societal economic burden. As in many cases the etiology is unknown, it is important to identify environmental factors that may be involved in the occurrence of this condition. In this review, we report all the studies published in PubMed and Scopus databases from January 1992 to January 2019, accessible as full-text articles, written in English, including clinical studies, original studies, and reviews. We excluded articles not written in English, duplicates, considering inappropriate populations and/or exposures or irrelevant outcomes and patients with known risk factors for preterm birth (PTB). The aim of this article is to identify and summarize the studies that examine environmental toxicants exposure associated with preterm birth. This knowledge will strengthen the possibility to develop strategies to reduce the exposure to these toxicants and apply clinical measures for preterm birth prevention.

Prenatal lead exposure modifies the effect of shorter gestation on increased blood pressure in children

BACKGROUND

High blood pressure (BP) in childhood is frequently renal in origin and a risk factor for adult hypertension and cardiovascular disease. Shorter gestations are a known risk factor for increased BP in adults and children, due in part to a nephron deficit in children born preterm. As nephrogenesis is incomplete until 36 weeks gestation, prenatal lead exposure occurring during a susceptible period of renal development may contribute to programming for later life renal disease. The relationship between shorter gestation and children's BP has not yet been explored to identify i) critical windows using nonlinear piecewise models or ii) combined with other early life risk factors such as prenatal lead exposure.

OBJECTIVES

(1) To evaluate the nonlinear relationship between lower gestational age and childhood BP measured at 4-6 years of age, and (2) to investigate modification by prenatal lead exposure.

METHODS

In a prospective longitudinal birth cohort, we assessed 565 children between 4 and 6 years of age (mean: 4.8 years) in the PROGRESS cohort in Mexico City, Mexico. Gestational age at delivery was calculated using maternal report of last menstrual period (LMP) and confirmed with Capurro physical examination at birth. We measured pregnant women's blood lead levels (BLLs) in the second trimester via inductively coupled plasma-mass spectrometry and children's BP using an automated device. We performed both linear and nonlinear piecewise regression analyses to examine associations of gestational age with children's BP adjusting for children's age, sex, height, prenatal exposure to smoke, and maternal socioeconomic status. We stratified to assess modification by prenatal lead exposure, and used a data-adaptive approach to identify a lead cutpoint.

RESULTS

Maternal second trimester BLLs ranged from 0.7 to 17.8 μg/dL with 112 (20%) women above the CDC guideline level of 5 μg/dL. In adjusted linear regression models, a one week reduction in gestational age was associated with a 0.5 mm Hg (95%CI: 0.2, 0.8) increase in SBP and a 0.4 mm Hg (95%CI 0.1, 0.6) increase in DBP. Our nonlinear models suggested evidence for different magnitude estimates on either side of an estimated join-point at 35.9 weeks' gestation, but did not reach statistical significance. However, when stratified by prenatal lead exposure, we identified a cutpoint lead level of concern of 2.5 μg/dL that suggested an interaction between gestational age and blood lead. Specifically, for BLLs ≥ 2.5 μg/dL, SBP was 1.6 (95%CI: 0.3, 2.9) mm Hg higher per each week reduction in gestational age among children born before 37.0 weeks; and among children born after 37.0 weeks, this relationship was attenuated yet remained significant [β: 0.9, 95%CI (0.2, 1.6)]. At BLLs below 2.5 μg/dL, there was no appreciable association between lower gestational age and SBP.

CONCLUSIONS

Our findings suggest that shorter gestation combined with higher prenatal lead exposure contributes to a higher risk of increased SBP at 4-6 years of age, particularly among infants born <37 weeks gestation. Our results underscore the importance of preventing prenatal lead exposure - even levels as low as 2.5 μg/dL - especially among pregnant women at risk for preterm birth. Given that high BP in childhood is a risk factor for adult hypertension and cardiovascular disease later in life, these results may have implications that extend across the life span.

Common Cervicovaginal Microbial Supernatants Alter Cervical Epithelial Function: Mechanisms by Which Lactobacillus crispatus Contributes to Cervical Health

Cervicovaginal (CV) microbiota is associated with vaginal health and disease in non-pregnant women. Recent studies in pregnant women suggest that specific CV microbes are associated with preterm birth (PTB). While the associations between CV microbiota and adverse outcomes have been demonstrated, the mechanisms regulating the associations remain unclear. As the CV space contains an epithelial barrier, we postulate that CV microbiota can alter the epithelial barrier function. We investigated the biological, molecular, and epigenetic effects of Lactobacillus crispatus, Lactobacillus iners, and Gardnerella vaginalis on the cervical epithelial barrier function and determined whether L. crispatus mitigates the effects of lipopolysaccharide (LPS) and G. vaginalis on the cervical epithelial barrier as a possible mechanism by which CV microbiota mitigates disease risk. Ectocervical and endocervical cells treated with L. crispatus, L. iners, and G. vaginalis bacteria-free supernatants alone or combined were used to measure cell permeability, adherens junction proteins, inflammatory mediators, and miRNAs. Ectocervical and endocervical permeability increased after L. iners and G. vaginalis exposure. Soluble epithelial cadherin increased after exposure to L. iners but not G. vaginalis or L. crispatus. A Luminex cytokine/chemokine panel revealed increased proinflammatory mediators in all three bacteria-free supernatants with L. iners and G. vaginalis having more diverse inflammatory effects. L. iners and G. vaginalis altered the expression of cervical-, microbial-, and inflammatory-associated miRNAs. L. crispatus mitigated the LPS or G. vaginalis-induced disruption of the cervical epithelial barrier and reversed the G. vaginalis-mediated increase in miRNA expression. G. vaginalis colonization of the CV space of a pregnant C57/B6 mouse resulted in 100% PTB. These findings demonstrate that L. iners and G. vaginalis alter the cervical epithelial barrier by regulating adherens junction proteins, cervical immune responses, and miRNA expressions. These results provide evidence that L. crispatus confers protection to the cervical epithelial barrier by mitigating LPS- or G. vaginalis-induced miRNAs associated with cervical remodeling, inflammation, and PTB. This study provides further evidence that the CV microbiota plays a role in cervical function by altering the cervical epithelial barrier and initiating PTB. Thus, targeting the CV microbiota and/or its effects on the cervical epithelium may be a potential therapeutic strategy to prevent PTB.

Long noncoding RNA expression in the cervix mid-pregnancy is associated with the length of gestation at delivery

Infants born preterm are at increased risk of multiple morbidities and mortality. Why some women deliver preterm remains poorly understood. Prior studies have shown that cervical microRNA expression and DNA methylation are associated with the length of gestation. However, no study has examined the role of long noncoding RNAs (lncRNAs) in the cervix during pregnancy. To determine whether expression of lncRNAs is associated with length of gestation at delivery, we analyzed RNA from cervical swabs obtained from 78 women during pregnancy (mean 15.5, SD 5.0, weeks of gestation) who were participating in the Spontaneous Prematurity and Epigenetics of the Cervix (SPEC) Study in Boston, MA, USA. We used a PCR-based platform and found that 9 lncRNAs were expressed in at least 50% of the participants. Of these, a doubling of the expression of TUG1, TINCR, and FALEC was associated with shorter lengths of gestation at delivery [2.8 (95% CI: 0.31, 5.2); 3.3 (0.22, 6.3); and 4.5 (7.3, 1.6) days shorter respectively]. Of the lncRNAs analyzed, none was statistically associated with preterm birth, but expression of FALEC was 2.6-fold higher in women who delivered preterm vs. term (P = 0.051). These findings demonstrate that lncRNAs can be measured in cervical samples obtained during pregnancy and are associated with subsequent length of gestation at delivery. Further, this study supports future work to replicate these findings in other cohorts and perform mechanistic studies to determine the role of lncRNAs in the cervix during pregnancy.

The Role of miRNAs as Biomarkers for Pregnancy Outcomes: A Comprehensive Review

Several studies showed that altered expression of the miRNA-ome in maternal circulation or in placental tissue may reflect not only gestational disorders, such as preeclampsia, spontaneous abortion, preterm birth, low birth weight, or macrosomia, but also prenatal exposure to environmental pollutants. Generally, the relationships between environmental exposure, changes in miRNA expression, and gestational disorders are explored separately, producing conflicting findings. However, validation of tissue-accessible biomarkers for the monitoring of adverse pregnancy outcomes needs a systematic methodological approach that takes also into account early-life environmental exposure. To achieve this goal, exposure to xenochemicals, endogenous agents, and diet should be assessed. This study has the aim to provide a comprehensive review on the role of miRNAs as potential biomarkers for adverse pregnancy outcomes and prenatal environmental exposure.

Expression profile of C19MC microRNAs in placental tissue of patients with preterm prelabor rupture of membranes and spontaneous preterm birth

The aim of the study was to demonstrate that preterm birth (PTB) is associated with altered C19MC microRNA expression profile in placental tissues. Gene expression of 15 placental specific microRNAs (miR-512-5p, miR-515-5p, miR-516-5p, miR-517-5p, miR-518b, miR-518f-5p, miR-519a, miR-519d, miR-519e-5p, miR-520a-5p, miR-520h, miR-524-5p, miR-525-5p, miR-526a and miR-526b-5p) was compared between groups: 34 spontaneous PTB, 108 preterm prelabor rupture of membranes (PPROM) and 20 term in labor pregnancies. Correlation between variables including relative microRNA quantification in placental tissues and the gestational age at delivery, white blood cell (WBC) count at admission and serum levels of C-reactive protein at admission in patients with PPROM and PTB was determined. Expression profile of microRNAs was different between PPROM and term in labor pregnancies, PTB and term in labor pregnancies, and between gestational age-matched PPROM and PTB groups. When compared with term in labor pregnancies, while C19MC microRNAs showed a downregulation in PPROM pregnancies (miR-525-5p), in PTB pregnancies C19MC microRNAs were upregulated (miR-515-5p, miR-516-5p, miR-518b, miR-518f-5p, miR-519a, miR-519e-5p, miR-520a-5p, miR-520h, and miR-526b-5p) or showed a trend to upregulation (miR-519d and miR-526a). In comparison to PTB pregnancies, the PPROM group demonstrated a significant portion of downregulated C19MC microRNAs (miR-516-5p, miR-517-5p, miR-518b, miR-518f-5p, miR-519a, miR-519d, miR-519e-5p, miR-520a-5p, miR-520h, miR-525-5p, miR-526a and miR-526b-5p). In the group of PPROM pregnancies, a weak negative correlation between the gestational age at delivery and microRNA gene expression in placental tissue for all examined C19MC microRNAs was observed. PTB pregnancies showed a positive correlation (miR-512-5p, miR-515-5p, miR-519e-5p) or a trend to positive correlation (miR-516-5p, miR-518b, miR-520h) between particular C19MC microRNAs and maternal WBC count at admission. Our study demonstrates that upregulation of C19MC microRNAs is a characteristic phenomenon of PTB. PPROM pregnancies have a tendency to produce lower levels of miR-525-5p. All examined C19MC microRNAs displayed decreased expression with advancing gestational age in PPROM group.

Maternal plasma miRNAs as biomarkers during mid-pregnancy to predict later spontaneous preterm birth: a pilot study

More than 10% of babies are born too early resulting in over 15 million preterm births and more than one million new-born deaths globally. Although women with a previous spontaneous preterm birth (SPTB) are considered at high risk for recurrence, the majority occur in women without prior history. Prediction of SPTB risk allows for improved care and potential for targeting novel and existing therapeutics to prevent SPTB, which may result in improved outcomes for infant and mother. In this pilot study, a miRNA array was used to analyse plasma from healthy women in their first pregnancy at 20 weeks of gestation who then went on to deliver either at term or experience SPTB at 28-32 weeks. We identified specific miRNA expression profiles that differentiated between those mothers who delivered at term or delivered following SPTB. miR302b, miR1253 and a clustering of miR548 miRNAs were underexpressed in SPTB cases compared to term controls. Conversely, miR223 was elevated in mothers that later experienced a SPTB. The circulating miRNAs identified in the present study may therefore be attractive candidates as non-invasive biomarkers for the early prediction of SPTB. Further larger studies are now warranted to investigate the potential clinical utility of these markers.

Environmental chemicals and preterm birth: Biological mechanisms and the state of the science

PURPOSE OF REVIEW

Preterm birth is a significant worldwide health problem of uncertain origins. The extant body of literature examining environmental contaminant exposures in relation to preterm birth is extensive but results remain ambiguous for most organic pollutants, metals and metalloids, and air pollutants. In the present review we examine recent epidemiologic studies investigating these associations, and identify recent advances and the state of the science. Additionally, we highlight biological mechanisms of action in the pathway between chemical exposures and preterm birth, including inflammation, oxidative stress, and endocrine disruption, that deserve more attention in this context.

RECENT FINDINGS

Important advances have been made in the study of the environment and preterm birth, particularly in regard to exposure assessment methods, exploration of effect modification by co-morbidities and exposures, and in identification of windows of vulnerability during gestation. There is strong evidence for an association between maternal exposure to some persistent pesticides, lead, and fine particulate matter, but data on other contaminants is sparse and only suggestive trends can be noted with the current data.

SUMMARY

Beyond replicating current findings, further work must be done to improve understanding of mechanisms underlying the associations observed between environmental chemical exposures and preterm birth. By examining windows of vulnerability, disaggregating preterm birth by phenotypes, and measuring biomarkers of mechanistic pathways in these epidemiologic studies we can improve our ability to detect associations with exposure, provide additional evidence for causality in an observational setting, and identify opportunities for intervention.

Bacterial and cytokine mixtures predict the length of gestation and are associated with miRNA expression in the cervix

AIM

Bacterial vaginosis may lead to preterm birth through epigenetic programming of the inflammatory response, specifically via miRNA expression.

METHODS

We quantified bacterial 16S rRNA, cytokine mRNA and 800 miRNA from cervical swabs obtained from 80 women at 16-19 weeks' gestation. We generated bacterial and cytokine indices using weighted quantile sum regression and examined associations with miRNA and gestational age at delivery.

RESULTS & DISCUSSION

Each decile of the bacterial and cytokine indices was associated with shorter gestations (p < 0.005). The bacterial index was associated with miR-494, 371a, 4286, 185, 320e, 888 and 23a (p < 0.05). miR-494 remained significant after false discovery rate correction (q < 0.1). The cytokine index was associated with 27 miRNAs (p < 0.05; q < 0.01).

CONCLUSION

Future investigation into the role of bacterial vaginosis- and inflammation-associated miRNA and preterm birth is warranted.

Novel concepts on pregnancy clocks and alarms: redundancy and synergy in human parturition

The signals and mechanisms that synchronize the timing of human parturition remain a mystery and a better understanding of these processes is essential to avert adverse pregnancy outcomes. Although our insights into human labor initiation have been informed by studies in animal models, the timing of parturition relative to fetal maturation varies among viviparous species, indicative of phylogenetically different clocks and alarms; but what is clear is that important common pathways must converge to control the birth process. For example, in all species, parturition involves the transition of the myometrium from a relaxed to a highly excitable state, where the muscle rhythmically and forcefully contracts, softening the cervical extracellular matrix to allow distensibility and dilatation and thus a shearing of the fetal membranes to facilitate their rupture. We review a number of theories promulgated to explain how a variety of different timing mechanisms, including fetal membrane cell senescence, circadian endocrine clocks, and inflammatory and mechanical factors, are coordinated as initiators and effectors of parturition. Many of these factors have been independently described with a focus on specific tissue compartments.In this review, we put forth the core hypothesis that fetal membrane (amnion and chorion) senescence is the initiator of a coordinated, redundant signal cascade leading to parturition. Whether modified by oxidative stress or other factors, this process constitutes a counting device, i.e. a clock, that measures maturation of the fetal organ systems and the production of hormones and other soluble mediators (including alarmins) and that promotes inflammation and orchestrates an immune cascade to propagate signals across different uterine compartments. This mechanism in turn sensitizes decidual responsiveness and eventually promotes functional progesterone withdrawal in the myometrium, leading to increased myometrial cell contraction and the triggering of parturition. Linkage of these processes allows convergence and integration of the gestational clocks and alarms, prompting a timely and safe birth. In summary, we provide a comprehensive synthesis of the mediators that contribute to the timing of human labor. Integrating these concepts will provide a better understanding of human parturition and ultimately improve pregnancy outcomes.

Epigenetics: linking social and environmental exposures to preterm birth

Preterm birth remains a leading cause of infant mortality and morbidity. Despite decades of research, marked racial and socioeconomic disparities in preterm birth persist. In the Unites States, more than 16% of African-American infants are born before 37 wk of gestation compared with less than 11% of white infants. While income and education differences predict a portion of these racial disparities, income and education are proxies of the underlying causes rather than the true cause. How these differences lead to the pathophysiology remains unknown. Beyond tobacco smoke exposure, most preterm birth investigators overlook environment exposures that often correlate with poverty. Environmental exposures to industrial contaminants track along both socioeconomic and racial/ethnic lines due to cultural variation in personal product use, diet, and residential geographical separation. Emerging evidence suggests that environmental exposure to metals and plasticizers contribute to preterm birth and epigenetic modifications. The extent to which disparities in preterm birth result from interactions between the social and physical environments that produce epigenetic modifications remains unclear. In this review, we highlight studies that report associations between environmental exposures and preterm birth as well as perinatal epigenetic sensitivity to environmental contaminants and socioeconomic stressors.

Epigenetics-a potential mediator between air pollution and preterm birth

Preterm birth is a major cause of infant morbidity and mortality and a potential risk factor for adult chronic disease. With over 15 million infants born preterm worldwide each year, preterm birth poses a global health concern. There is a possible association between air pollution and preterm birth, though studies have been inconsistent, likely due to variation in study design. How air pollution induces health effects is uncertain; however, studies have repeatedly demonstrated the effects of air pollution on epigenetic modifications. More recent evidence suggests that epigenetics may, in turn, be linked to preterm birth. Discovery of environmentally modifiable epigenetic processes connected to preterm birth may help to identify women at risk of preterm birth, and ultimately lead to development of new preterm birth prevention measures.

Identification and functional analysis of microRNA in myometrium tissue from spontaneous preterm labor

Spontaneous preterm labor is an important complication in perinatology characterized by early onset myometrium contractions leading to labor at preterm. However, the exact mechanism that maintain uterine quiescence and promote increased uterine contractility during labor were incompletely defined. MicroRNAs is a class of short non-coding RNAs that regulate gene expression at the post-transcriptional level by binding the 3' untranslated region of target mRNAs and play an important role in biological process and cellular functions. We hypothesized we could find differentially expressed microRNAs in the myometrium of women in spontaneous preterm labor. Thus, a microarray analysis of miRNAs of preterm myometrium was performed. 18 out of the 2006 detected microRNAs were found to be significantly dysregulated in myometrium in labor verse not in labor at preterm. Biological validation by quantitative real-time polymerase chain reaction confirms us a consistence rate of 83.3% (5 out of 6) with microarray analysis. The target genes for validated microRNAs were predicted by three algorithms (PicTar, TargetScan, and miRanda). Most of the potential targets of the miRNAs were relevant to positive regulation of cardiac muscle hypertrophy, reduction of cytosolic calcium ion concentration and relaxation of cardiac muscle as well as prostate cancer, adherents junction, regulation of actin cytoskeleton and regulation and other factor-regulated calcium reabsorption. Our result illustrates a characteristic microRNA profile in myometrium tissues and provides a new understanding of the process involved in spontaneous preterm labor.

Altered miRNA expression in the cervix during pregnancy associated with lead and mercury exposure

AIM

Toxic metals including lead and mercury are associated with adverse pregnancy outcomes. This study aimed to assess the association between miRNA expression in the cervix during pregnancy with lead and mercury levels.

MATERIALS & METHODS

We obtained cervical swabs from pregnant women (n = 60) and quantified cervical miRNA expression. Women's blood lead, bone lead and toenail mercury levels were analyzed. We performed linear regression to examine the association between metal levels and expression of 74 miRNAs adjusting for covariates.

RESULTS

Seventeen miRNAs were negatively associated with toenail mercury levels, and tibial bone lead levels were associated with decreased expression of miR-575 and miR-4286.

CONCLUSION

The findings highlight miRNAs in the human cervix as novel responders to maternal chemical exposure during pregnancy.