Reactive oxygen species and preterm premature rupture of membranes-a review

Histologic Evidence of Epithelial-Mesenchymal Transition and Autophagy in Human Fetal Membranes

Preterm, prelabor rupture of the human fetal membranes (pPROM) is involved in 40% of spontaneous preterm births worldwide. Cellular-level disturbances and inflammation are effectors of membrane degradation, weakening, and rupture. Maternal risk factors induce oxidative stress (OS), senescence, and senescence-associated inflammation of the fetal membranes as reported mechanisms related to pPROM. Inflammation can also arise in fetal membrane cells (amnion/chorion) due to OS-induced autophagy and epithelial-mesenchymal transition (EMT). Autophagy, EMT, and their correlation in pPROM, along with OS-induced autophagy-related changes in amnion and chorion cells in vitro, were investigated. Immunocytochemistry staining of cytokeratin-18 (epithelial marker)/vimentin (mesenchymal marker) and proautophagy-inducing factor LC3B were performed in fetal membranes from pPROM, term not in labor, and term labor. Ultrastructural changes associated with autophagy were verified by transmission electron microscopy of the fetal membranes and in cells exposed to cigarette smoke extract (an OS inducer). EMT and LC3B staining was compared in the chorion from pPROM versus term not in labor. Transmission electron microscopy confirmed autophagosome formation in pPROM amnion and chorion. In cell culture, autophagosomes were formed in the amnion with OS treatment, while autophagosomes were accumulated in both cell types with autophagy inhibition. This study documents the association between pPROMs and amniochorion autophagy and EMT, and supports a role for OS in inducing dysfunctional cells that increase inflammation, predisposing membranes to rupture.

Impact of Prematurity on the Buccal Epithelial Cells of the Neonates via Wnt/Beta-Catenin Signaling Pathway and Apoptosis

OBJECTIVE

 Understanding the reflections of prematurity is necessary for the management of neonatal complications. We focused on the impact of prematurity and related "maternal risk factors/obstetric complications" on buccal cells of the neonates via evaluation of the Wnt/β-catenin signaling pathway and apoptosis.

STUDY DESIGN

 This study consisted of "early preterm neonates (EPN) (≤34th gestational week [gw]) (n = 36)," "late preterm neonates (LPN) (34th- < 37th gw) (n = 46)," and "term neonates (control) (≥37th gw) (n = 56)." Cohort was also subclassified according to the presence of maternal risk factors, obstetric complications, and neonatal complications. Wnt/β-catenin signaling and caspase-3 activation pathways were studied immunocytochemically.

RESULTS

 Wnt/β-catenin signaling positivity was statistically more frequent at buccal smears of the EPN and LPN groups compared with controls (p < 0.001). The cutoff for gestational age at delivery in receiver operating characteristic curve with the best balance of sensitivity (67.4%) and specificity (67.3%) was 35.8th gw for determining the reduction of Wnt/β-catenin signaling positivity (p < 0.001). The study demonstrated that obstetric complications significantly affected the activity of signaling, while maternal risk factors do not have any effect on Wnt/β-catenin signaling pathway (p = 0.003 and p = 0.828, respectively). This study also demonstrated a significant relationship between Wnt/β-catenin signaling pathway and the presence of neonatal complications (p = 0.015).

CONCLUSION

 Dynamic characteristics of buccal cells are influenced by prematurity and related obstetric and neonatal problems. Buccal smear is a good tool to investigate the impact of prematurity and obstetric problems on perinatal outcome.

KEY POINTS

· Neonatal buccal cells are affected by prematurity and related obstetric/neonatal problems.. · 35.8th gw is critical for determining the reduction of Wnt/β-catenin signaling positivity.. · Obstetric and neonatal complications significantly related to Wnt/β-catenin signaling activity..

Exposure to atrazine by drinking water and the increased risk of neonatal complications in consequence: a meta-analysis

This meta-analysis evaluates the association between atrazine (ATR) exposure and small for gestational age (SGA), preterm birth (PTB), and low birth weight (LBW). A comprehensive search was done on academic databases (e.g. PubMed, Scopus, Embase, and Google Scholar) to achieve all pertinent studies up to May 2023. A pooled odd ratio (OR) and corresponding 95% confidence interval (CI) were applied to evaluate this correlation. As a result, five eligible studies met the inclusion criteria and were included in our study, and the result of the present meta-analysis showed that ATR exposure increased the risk of SGA (OR = 1.11; 95% CI = 1.03-1.20 for highest versus lowest category of ATR), PTB (OR = 1.16; 95% CI = 1.03-1.30), and LBW (OR = 1.26; 95% CI = 1.10-1.44). This meta-analysis suggests that ATR in drinking water may be a risk factor for SGA, PTB, and LBW.

Creation of a novel synthetic amniotic fluid for use in fetal therapy with in vitro testing on human amniotic membranes

BACKGROUND

Normal saline or lactated Ringer's solutions are usually infused at the time of fetal interventions; however, the effect of these fluids on the amniotic membranes has never been assessed. Given both the significant differences between the composition of normal saline solution, lactated Ringer's solution, and amniotic fluid and the significant risk of prematurity after fetal interventions, an investigation is warranted.

OBJECTIVE

This study aimed to evaluate the effect of current amnioinfusion fluids on the human amnion compared with a novel synthetic amniotic fluid.

STUDY DESIGN

Amniotic epithelial cells from term placentas were isolated and cultured per protocol. A synthetic amniotic fluid was created with similar electrolyte, pH, albumin, and glucose concentrations to human amniotic fluid, termed "Amnio-well." The cultured human amniotic epithelium was exposed to normal saline solution, lactated Ringer's solution, and Amnio-well. As a control, 1 group of cells remained in culture media. Cells were evaluated for apoptosis and necrosis. A second analysis to examine if cells could be "rescued" was performed, wherein the cells were allowed to remain in the culture media for an additional 48 hours after amnioinfusion. Subsequently, tissue testing with human amniotic membrane explants was evaluated similarly. Immunofluorescent intensity studies were undertaken to evaluate reactive oxygen species-mediated cell damage. Real-time quantitative polymerase chain reaction was used to evaluate gene expression in apoptotic pathways.

RESULTS

With simulated amnioinfusion, 44%, 52%, and 89% of amniotic epithelial cells were alive after exposure to normal saline solution, lactated Ringer's solution, and Amnio-well, respectively, compared with 85% in control (P<.001). After amnioinfusion and attempted cell rescue, 21%, 44%, 94%, and 88% of cells were alive after exposure to normal saline solution, lactated Ringer's solution, Amnio-well, and control, respectively (P<.001). In simulated amnioinfusion with full-thickness tissue explants, 68%, 80%, 93%, and 96% of cells were viable in normal saline solution, lactated Ringer's solution, Amnio-well, and control, respectively (P<.001). In culture, reactive oxygen species production was higher in normal saline solution, lactated Ringer's solution, and Amnio-well than in control (4.9-, 6.6-, and 1.8-fold higher, respectively, P<.001); however, this could be mitigated in Amnio-well by adding ulin-A-statin and ascorbic acid. Gene expression data revealed abnormal signaling in the p21 and BCL2/BAX pathways with normal saline solution compared with control (P=.006 and P=.041); changes were not seen with Amnio-well.

CONCLUSION

In vitro, normal saline and lactated Ringer's solutions caused increased amniotic membrane reactive oxygen species and cell death. The use of a novel fluid similar to human amniotic fluid led to the normalization of cellular signaling and less cell death.

The role of neutrophils in chorioamnionitis

Chorioamnionitis, commonly referred to as intrauterine infection or inflammation, is pathologically defined by neutrophil infiltration and inflammation at the maternal-fetal interface. Chorioamnionitis is the common complication during late pregnancy, which lead to a series of serious consequences, such as preterm labor, preterm premature rupture of the fetal membranes, and fetal inflammatory response syndrome. During infection, a large number of neutrophils migrate to the chorio-decidua in response to chemokines. Although neutrophils, a crucial part of innate immune cells, have strong anti-inflammatory properties, over-activating them can harm the body while also eliminating pathogens. This review concentrated on the latest studies on chorioamnionitis-related consequences as well as the function and malfunction of neutrophils. The release of neutrophil extracellular traps, production of reactive oxygen species, and degranulation from neutrophils during intrauterine infection, as well as their pathological roles in complications related to chorioamnionitis, were discussed in detail, offering fresh perspectives on the treatment of chorioamnionitis.

Development of oxidative stress-associated disease models using feto-maternal interface organ-on-a-chip

Oxidative stress (OS) and inflammation arising from cellular derangements at the fetal membrane-decidual interface (feto-maternal interface [FMi]) is a major antecedent to preterm birth (PTB). However, it is impractical to study OS-associated FMi disease state during human pregnancy, and thus it is difficult to develop strategies to reduce the incidences of PTB. A microfluidic organ-on-chip model (FMi-OOC) that mimics the in vivo structure and functions of FMi in vitro was developed to address this challenge. The FMi-OOC contained fetal (amnion epithelial, mesenchymal, and chorion) and maternal (decidua) cells cultured in four compartments interconnected by arrays of microchannels to allow independent but interconnected co-cultivation. Using this model, we tested the effects of OS and inflammation on both fetal (fetal → maternal) and maternal (maternal → fetal) sides of the FMi and determined their differential impact on PTB-associated pathways. OS was induced using cigarette smoke extract (CSE) exposure. The impacts of OS were assessed by measuring cell viability, disruption of immune homeostasis, epithelial-to-mesenchymal transition (EMT), development of senescence, and inflammation. CSE propagated (LC/MS-MS analysis for nicotine) over a 72-hour period from the maternal to fetal side, or vice versa. However, they caused two distinct pathological effects on the maternal and fetal cells. Specifically, fetal OS induced cellular pathologies and inflammation, whereas maternal OS caused immune intolerance. The pronounced impact produced by the fetus supports the hypothesis that fetal inflammatory response is a mechanistic trigger for parturition. The FMi disease-associated changes identified in the FMi-OOC suggest the unique capability of this in vitro model in testing in utero conditions.

Maternal exposure to ambient air pollution mixture and premature rupture of membranes: Evidence from a large cohort in Southern California (2008-2018)

BACKGROUND

There is minimal evidence of relationships between maternal air pollution exposure and spontaneous premature rupture of membranes (SPROM), a critical obstetrical problem that can significantly increase maternal and fetal mortality and morbidity. No prior study has explored the PROM risk related to specific components of particulate matter with aerodynamic diameters of ≤ 2.5 µm (PM2.5). We examined associations between maternal exposure to nitrogen dioxide (NO2), ozone (O3), PM2.5, PM10, and PM2.5 constituents and SPROM.

METHODS

A large retrospective cohort study was conducted and included 427,870 singleton live births from Kaiser Permanente Southern California during 2008-2018. Monthly averages of NO2, O3 (8-h daily maximum), PM2.5, and PM10 were measured using empirical Bayesian kriging based on measurements from monitoring stations. Data on PM2.5 sulfate, nitrate, ammonium, organic matter, and black carbon were obtained from a fine-resolution model. A discrete time approach with pooled logistic regressions was used to estimate associations throughout the pregnancy and based on trimesters and gestational months. The quantile-based g-computation models were fitted to examine the effects of 1) the air pollution mixture of four pollutants of interest and 2) the mixture of PM2.5 components.

RESULTS

There were 37,857 SPROM cases (8.8%) in our study population. We observed relationships between SPROM and maternal exposure to NO2, O3, and PM2.5. PM2.5 sulfate, nitrate, ammonium, and organic matter were associated with higher SPROM risks in the single-pollutant model. Mixture analyses demonstrated that the overall effects of the air pollution mixture and PM2.5 mixture in this study were mainly driven by O3 and PM2.5 nitrate, respectively. Underweight mothers had a significantly higher risk of SPROM associated with NO2.

CONCLUSION

Our findings add to the literature on associations between air pollution exposure and SPROM. This is the first study reporting the impact of PM2.5 constituents on SPROM.

Biomarkers of oxidative stress and reproductive complications

Oxidative stress is the result of an imbalance between the formation of reactive oxygen species (ROS) and the levels of enzymatic and non-enzymatic antioxidants. The assessment of biological redox status is performed by the use of oxidative stress biomarkers. An oxidative stress biomarker is defined as any physical structure or process or chemical compound that can be assessed in a living being (in vivo) or in solid or fluid parts thereof (in vitro), the determination of which is a reproducible and reliable indicator of oxidative stress. The use of oxidative stress biomarkers allows early identification of the risk of developing diseases associated with this process and also opens up possibilities for new treatments. At the end of the last century, interest in oxidative stress biomarkers began to grow, due to evidence of the association between the generation of free radicals and various pathologies. Up to now, a significant number of studies have been carried out to identify and apply different oxidative stress biomarkers in clinical practice. Among the most important oxidative stress biomarkers, it can be mentioned the products of oxidative modifications of lipids, proteins, nucleic acids, and uric acid as well as the measurement of the total antioxidant capacity of fluids in the human body. In this review, we aim to present recent advances and current knowledge on the main biomarkers of oxidative stress, including the discovery of new biomarkers, with emphasis on the various reproductive complications associated with variations in oxidative stress levels.

Antenatal and Postnatal Sequelae of Oxidative Stress in Preterm Infants: A Narrative Review Targeting Pathophysiological Mechanisms

The detrimental effects of oxidative stress (OS) can start as early as after conception. A growing body of evidence has shown the pivotal role of OS in the development of several pathological conditions during the neonatal period, which have been therefore defined as OS-related neonatal diseases. Due to the physiological immaturity of their antioxidant defenses and to the enhanced antenatal and postnatal exposure to free radicals, preterm infants are particularly susceptible to oxidative damage, and several pathophysiological cascades involved in the development of prematurity-related complications are tightly related to OS. This narrative review aims to provide a detailed overview of the OS-related pathophysiological mechanisms that contribute to the main OS-related diseases during pregnancy and in the early postnatal period in the preterm population. Particularly, focus has been placed on pregnancy disorders typically associated with iatrogenic or spontaneous preterm birth, such as intrauterine growth restriction, pre-eclampsia, gestational diabetes, chorioamnionitis, and on specific postnatal complications for which the role of OS has been largely ascertained (e.g., respiratory distress, bronchopulmonary dysplasia, retinopathy of prematurity, periventricular leukomalacia, necrotizing enterocolitis, neonatal sepsis). Knowledge of the underlying pathophysiological mechanisms may increase awareness on potential strategies aimed at preventing the development of these conditions or at reducing the ensuing clinical burden.

The efficacy and safety of vitamin C administration to women with history of premature preterm rupture of membrane in prevention of such event in current pregnancy: Randomized controlled clinical trial

BACKGROUND

When rupture of membrane happens before onset of labor, the condition in obstetric practice is defined as "Prelabor rupture of membranes (PROM)" leading to leakage of amniotic fluid through ruptured chorioamniotic membranes and the conditions happens before 37 weeks of pregnancy the term "preterm PROM (PPROM)" is applied. Lack of vitamin C has been suggested as a predisposing factor and vitamin C supplementation has been suggested as a preventive measure.

AIM OF THE STUDY

This study was aimed to determine the efficacy and safety of administration of vitamin C women with history of premature preterm rupture of membrane in prevention of such event in current pregnancy.

PATIENTS AND METHODS

The present randomized controlled clinical trial was performed in Maternity and Children Teaching Hospital in Al-Diwaniyah province in Iraq. It included 100 women with previous history of premature preborn rupture of membrane who were randomly allocated into two groups. The first group, the study group included 55 women who received vitamin C supplementation orally staring from 14 weeks gestation and the second group, the reference group was the placebo group (n = 45). Data regarding age, previous abortion, body mass index, number of previous pregnancies and previous abortions were obtained and outcome variables included gestational age at which rupture of membrane happened, gestational age at which delivery happened and birth weight were collected.

RESULTS

Vitamin C was able to significantly increase the GA at rupture or membrane (p = 0.033), form 29.00 ± 2.92 weeks to 30.11 ± 2.21 weeks. Vitamin C was also able to significantly increase the GA at birth (p = 0.019), form 32.04 ± 2.88 weeks to 33.31 ± 2.43 weeks. In addition, Vitamin C was also able to significantly increase the birth weight (p = 0.019) from 1951.10 ± 869.72 gram to 2409.10 ± 613.44 gram.

CONCLUSION

Vitamin C Administration to women with previous history of Premature Preterm Rupture of Membrane is efficient and safe in prevention of such event in current pregnancy.

Epithelial to mesenchymal transition (EMT) of feto-maternal reproductive tissues generates inflammation: a detrimental factor for preterm birth

Human pregnancy is a delicate and complex process where multiorgan interactions between two independent systems, the mother, and her fetus, maintain pregnancy. Intercellular interactions that can define homeostasis at the various cellular level between the two systems allow uninterrupted fetal growth and development until delivery. Interactions are needed for tissue remodeling during pregnancy at both fetal and maternal tissue layers. One of the mechanisms that help tissue remodeling is via cellular transitions where epithelial cells undergo a cyclic transition from epithelial to mesenchymal (EMT) and back from mesenchymal to epithelial (MET). Two major pregnancy-associated tissue systems that use EMT, and MET are the fetal membrane (amniochorion) amnion epithelial layer and cervical epithelial cells and will be reviewed here. EMT is often associated with localized inflammation, and it is a well-balanced process to facilitate tissue remodeling. Cyclic transition processes are important because a terminal state or the static state of EMT can cause accumulation of proinflammatory mesenchymal cells in the matrix regions of these tissues and increase localized inflammation that can cause tissue damage. Interactions that determine homeostasis are often controlled by both endocrine and paracrine mediators. Pregnancy maintenance hormone progesterone and its receptors are critical for maintaining the balance between EMT and MET. Increased intrauterine oxidative stress at term can force a static (terminal) EMT and increase inflammation that are physiologic processes that destabilize homeostasis that maintain pregnancy to promote labor and delivery of the fetus. However, conditions that can produce an untimely increase in EMT and inflammation can be pathologic. These tissue damages are often associated with adverse pregnancy complications such as preterm prelabor rupture of the membranes (pPROM) and spontaneous preterm birth (PTB). Therefore, an understanding of the biomolecular processes that maintain cyclic EMT-MET is critical to reducing the risk of pPROM and PTB. Extracellular vesicles (exosomes of 40-160 nm) that can carry various cargo are involved in cellular transitions as paracrine mediators. Exosomes can carry a variety of biomolecules as cargo. Studies specifically using exosomes from cells undergone EMT can carry a pro-inflammatory cargo and in a paracrine fashion can modify the neighboring tissue environment to cause enhancement of uterine inflammation.

Possible Involvement of miR-98 in the Regulation of PGRMC1 During Decidualization

Human endometrial stromal cells (ESCs) differentiate into decidual cells for embryo implantation during the mid-secretory phase of the menstrual cycle. Decidualization is characterized by enhanced production of insulin-like growth factor-binding protein 1 (IGFBP1) and prolactin (PRL) by ESCs and their morphological transformation into polygonal cells. Progesterone (P4) receptor membrane component 1 (PGRMC1) is a member of a P4-binding complex implicated in function in female reproduction. In this study, we explored the mechanisms that regulate PGRMC1 during decidualization of human ESCs. Immunohistochemical analysis of endometrial samples showed that PGRMC1 was expressed in endometrial glandular and luminal epithelial cells and stromal cells throughout the menstrual cycle; however, the protein level in stroma was reduced in the secretory phase. Incubation of ESCs with dibutyryl (db)-cAMP and P4 in vitro, which induces decidualization, decreased the PGRMC1 protein abundance. Further, treatment with a PGRMC1-targeting siRNA or PGRMC1 inhibitor (AG-205) promoted mRNA expression of the db-cAMP/P4- and db-cAMP-induced decidual markers IGFBP1 and PRL. Moreover, the microRNA miR-98, a potential repressor of PGRMC1, was upregulated during decidualization, and transfection of ESCs with a miR-98 mimic decreased the PGRMC1 protein level. These findings suggest that miR-98-mediated downregulation of endometrial PGRMC1 may promote decidualization for the establishment of pregnancy.

Fetal inflammatory response at the fetomaternal interface: A requirement for labor at term and preterm

Human parturition at term and preterm is an inflammatory process synchronously executed by both fetomaternal tissues to transition them from a quiescent state t an active state of labor to ensure delivery. The initiators of the inflammatory signaling mechanism can be both maternal and fetal. The placental (fetal)-maternal immune and endocrine mediated homeostatic imbalances and inflammation are well reported. However, the fetal inflammatory response (FIR) theories initiated by the fetal membranes (amniochorion) at the choriodecidual interface are not well established. Although immune cell migration, activation, and production of proparturition cytokines to the fetal membranes are reported, cellular level events that can generate a unique set of inflammation are not well discussed. This review discusses derangements to fetal membrane cells (physiologically and pathologically at term and preterm, respectively) in response to both endogenous and exogenous factors to generate inflammatory signals. In addition, the mechanisms of inflammatory signal propagation (fetal signaling of parturition) and how these signals cause immune imbalances at the choriodecidual interface are discussed. In addition to maternal inflammation, this review projects FIR as an additional mediator of inflammatory overload required to promote parturition.

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.

Role of prolidase activity and oxidative stress biomarkers in unexplained infertility

OBJECTIVE

Our aim was to explore the significance of serum prolidase enzyme activity and oxidative stress in women with unexplained infertility (UEI).

METHODS

In this case-control study (n = 160; 86 cases; 74 controls) prolidase enzyme activity and total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), and vitamin E were measured in plasma using enzyme-linked immunosorbent assays.

RESULTS

Prolidase enzyme activity and TAS levels were particularly higher in the patient group (P = 0.013, P = 0.001, respectively). Decreased OSI levels were detected in the patient group (P = 0.001). There was a positive relationship of prolidase with vitamin E in both patient and control groups (r = 0.892, P = 0.001, and r = 0.659, P = 0.001, respectively). A positive, but weak, relationship was identified between prolidase activity and TOS levels and also between vitamin E and TOS levels in the UEI group (r = 0.265, P = 0.049, and r = 0.288, P = 0.014, respectively). No association was found between prolidase and TOS levels or between vitamin E and TOS levels in the control group (r = 0.0097, P = 0.527, and r = 0.085, P = 0.610, respectively).

CONCLUSION

Our results showed an association between serum prolidase activity and oxidative stress in UEI patients. Further studies including greater groups are required to show the role of reactive oxygen species in UEI.

Association between prenatal rare earth elements exposure and premature rupture of membranes: Results from a birth cohort study

BACKGROUND

The widespread exploitation and application of rare earth elements (REE) have led to the risk of human exposure and might result in the adverse health effect on pregnant women. However, no epidemiological studies have explored the associations between prenatal REE exposure and premature rupture of membranes (PROM).

OBJECTIVE

We aimed to investigate the associations of maternal urinary REE levels with the risk of PROM.

METHODS

A total of 4897 mother-newborn pairs were recruited from a birth cohort study in Wuhan, China. Urinary concentrations of REE were measured by inductively coupled plasma mass spectrometry (ICP-MS). The associations of prenatal REE exposure with PROM were evaluated using logistic regression models. False discovery rate (FDR) was applied to adjust for multiple testing. Weighted quantile sum (WQS) regression was used to estimate the association of urinary REE mixture with PROM.

RESULTS

With one unit increase (μg/g creatinine) in natural log-transformed urinary REE levels (Ce, Yb, La, Pr, Nd, Eu, Gd, Dy, Ho, Er, Tm), the adjusted ORs (95% CIs) for the PROM were from 1.143 (1.078, 1.211) to 1.317 (1.223, 1.419), and the associations were still observed after FDR adjustment (all P_FDRs < 0.05). The associations were stronger among male infants than female infants. Furthermore, the urinary REE mixture was also associated with the risk of PROM, a quartile increase in the WQS index of REE resulted in ORs (95% CI) for the PROM of 1.494 (1.356, 1.645) in the adjusted model.

CONCLUSIONS

Our findings suggested that prenatal exposure to REE (Ce, Yb, La, Pr, Nd, Eu, Gd, Dy, Ho, Er, and Tm) and REE mixture were associated with the increased risk of PROM. Further studies from different populations are needed to confirm the associations and to explore the mechanisms.

Novel Insights into the Regulatory Role of Nuclear Factor (Erythroid-Derived 2)-Like 2 in Oxidative Stress and Inflammation of Human Fetal Membranes

Fetal membrane dysfunction in response to oxidative stress (OS) is associated with adverse pregnancy outcomes. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is one of the regulators of innate OS response. This study evaluated changes in Nrf2 expression and its downstream targets heme oxygenase (HO-1) and peroxisome proliferator-activated receptor gamma (PPARγ) in fetal membranes during OS and infection in vitro. Furthermore, we tested the roles of sulforaphane (SFN; an extract from cruciferous vegetables) and trigonelline (TRN; an aromatic compound in coffee) in regulating Nrf2 and its targets. Fetal membranes (n = 6) collected at term were placed in an organ explant system were treated with water-soluble cigarette smoke extract (CSE), an OS inducer (1:10), and lipopolysaccharide (LPS; 100 ng/mL). Nrf2 expression, expression, its enhancement by sulforaphane (SFN, 10 µM/mL) and down regulation by TRN (10uM/mL) was determined by western blots. Expression of Nrf2 response elements PPARγ (western) heme oxygenase (HO-1), and IL-6 were quantified by ELISA. CSE and LPS treatment of fetal membranes increased nrf2, but reduced HO-1 and PPARγ and increased IL-6. Co-treatment of SFN, but not with TRN, with CSE and LPS increased Nrf2 substantially, as well as increased HO-1 and PPARγ and reduced IL-6 expression. Risk factor-induced Nrf2 increase is insufficient to generate an antioxidant response in fetal membranes. Sulforaphane may enhance innate antioxidant and anti-inflammatory capacity by increasing NRF-2 expression.

Toxicant Disruption of Immune Defenses: Potential Implications for Fetal Membranes and Pregnancy

In addition to providing a physical compartment for gestation, the fetal membranes (FM) are an active immunological barrier that provides defense against pathogenic microorganisms that ascend the gravid reproductive tract. Pathogenic infection of the gestational tissues (FM and placenta) is a leading known cause of preterm birth (PTB). Some environmental toxicants decrease the capacity for organisms to mount an immune defense against pathogens. For example, the immunosuppressive effects of the widespread environmental contaminant trichloroethylene (TCE) are documented for lung infection with Streptococcus zooepidemicus. Group B Streptococcus (GBS; Streptococcus agalactiae) is a bacterial pathogen that is frequently found in the female reproductive tract and can colonize the FM in pregnant women. Work in our laboratory has demonstrated that a bioactive TCE metabolite, S-(1, 2-dichlorovinyl)-L-cysteine (DCVC), potently inhibits innate immune responses to GBS in human FM in culture. Despite these provocative findings, little is known about how DCVC and other toxicants modify the risk for pathogenic infection of FM. Infection of the gestational tissues (FM and placenta) is a leading known cause of PTB, therefore toxicant compromise of FM ability to fight off infectious microorganisms could significantly contribute to PTB risk. This Perspective provides the current status of understanding of toxicant-pathogen interactions in FM, highlighting knowledge gaps, challenges, and opportunities for research that can advance protections for maternal and fetal health.

Porphyromonas gingivalis and adverse pregnancy outcomes: a review on its intricate pathogenic mechanisms

Porphyromonas gingivalis (P. gingivalis), a Gram-negative facultative anaerobe of the oral cavity, is associated with the onset of various adverse pregnancy outcomes. P. gingivalis is linked with the development of preeclampsia, preterm labour, spontaneous abortion, gestational diabetes, foetal growth restriction, and misconception. The unique virulence factors, surface adhesions, enzymes of P. gingivalis can directly injure and alter the morphology, microbiome the foetal and maternal tissues. P. gingivalis can even exaggerate the production of cytokines, free radicals and acute-phase proteins in the uterine compartment that increases the risk of myometrial contraction and onset of preterm labour. Although evidence confirms the presence of P. gingivalis in the amniotic fluid and placenta of women with poor pregnancy outcomes, the intricate molecular mechanisms by which P. gingivalis initiates various antenatal and postnatal maternal and foetal complications are not well explained in the literature. Therefore, the present review aims to comprehensively summarise and highlight the recent and unique molecular pathogenic mechanisms of P. gingivalis associated with adverse pregnancy outcomes.

Comparison of the accuracy and reliability of the AmniSure, AMNIOQUICK, and AL-SENSE tests for early diagnosis of premature rupture of membranes

OBJECTIVE

To compare the accuracy and reliability of the AmniSure, AMNIOQUICK, and AL-SENSE tests with conventional tests to diagnose suspected premature rupture of membranes (PROM).

METHODS

A prospective cohort study of 60 pregnant women at 25-36 weeks of pregnancy with suspected PROM was conducted between January and April 2015. AmniSure (Qiagen Sciences LLC, Germantown, MD, USA), AMNIOQUICK (BIOSYNEX, Strasbourg, France), and AL-SENSE (Common Sense Ltd, Caesarea, Israel) tests were performed after conventional tests (ultrasonography, pooling, nitrazine, and fern tests) and women were followed-up for 7 days. Sensitivity, specificity, and diagnostic accuracy, among others, were assessed and compared.

RESULTS

For women with a confirmed diagnosis of PROM, the sensitivity and specificity of conventional tests were 93.7% and 100.0%, respectively; diagnostic accuracy was 98.3%. Sensitivity, specificity, and diagnostic accuracy were all 100.0% for AmniSure. Sensitivity, specificity, and diagnostic accuracy for AMNIOQUICK were 75.0%, 97.7%, and 91.6%, respectively. Sensitivity, specificity, and diagnostic accuracy were 75.0%, 86.3%, 83.3%, respectively, for the AL-SENSE pad test.

CONCLUSION

The AmniSure test was most sensitive and specific for diagnosing PROM compared with the other tests and is reliable and usable.

Maternal serum thiol/disulfide homeostasis in pregnancies complicated by fetal hypoxia

We aimed to evaluate maternal serum thiol/disulphide homeostasis in pregnancies complicated by fetal distress (FD). A total of 100 patients beyond the 34th week of pregnancy were included in this study, and they were divided into two groups. The study group included 50 patients who had been diagnosed with FD; the control group was composed of 50 patients who had shown no signs of FD and who had undergone an elective (previous) caesarean section (CS). The native thiol, total thiol and native thiol/total thiol (%) concentrations were lower in Group 1 patients than Group 2 patients (p < .001). The disulphide, disulphide/native thiol (%) and disulphide/total thiol (%) concentrations were higher in Group 1 patients than Group 2 patients (p < .001). This study suggests that maternal thiol/disulphide homeostasis is impaired in pregnancies complicated by FD.IMPACT STATEMENTWhat is already known about this subject? Oxidative stress (OS) has previously been investigated in FD. This study reports for the first time a new novel and automatic measurement method.What do the results of this study add? This study shows that the thiol balance shifts in the direction of disulphide in the cases of FD.What are the implications of these findings for clinical practice and further research? Thiol balance can be used for the timely diagnosis of FD.

Maternal exposure to ambient fine particulate matter and risk of premature rupture of membranes in Wuhan, Central China: a cohort study

BACKGROUND

The associations between maternal exposure to ambient PM_2.5 during pregnancy and the risk of premature rupture of membranes (PROM) and preterm premature rupture of membranes (PPROM) are controversial. And no relevant study has been conducted in Asia. This study aimed to determine the association between maternal exposure to ambient PM_2.5 during pregnancy and the risk of (P)PROM.

METHODS

A cohort study including all singleton births in a hospital located in Central China from January 2015 through December 2017 was conducted. Multivariable logistic regression models, stratified analysis, generalized additive model, and two-piece-wise linear regression were conducted to evaluate how exposure to ambient PM_2.5 during pregnancy is associated with the risks of PROM and PPROM.

RESULTS

A total of 4364 participants were included in the final analysis, where 11.71 and 2.34% of births were complicated by PROM and PPROM, respectively. The level of PM_2.5 exhibited a degree of seasonal variation, and its median concentrations were 63.7, 59.3, 55.8, and 61.8 μg/m³ for the first trimester, second trimester, third trimester, and the whole duration of pregnancy, respectively. After adjustment for potential confounders, PROM was positively associated with PM_2.5 exposure (per 10 μg/m³) [Odds Ratio (OR) = 1.14, 95% Confidence Interval (CI), 1.02-1.26 for the first trimester; OR = 1.09, 95% CI, 1.00-1.18 for the second trimester; OR = 1.13, 95% CI, 1.03-1.24 for the third trimester; OR = 1.35, 95% CI, 1.12-1.63 for the whole pregnancy]. PPROM had positive relationship with PM_2.5 exposure (per 10 μg/m³) (OR = 1.17, 95% CI, 0.94-1.45 for first trimester; OR = 1.11, 95% CI, 0.92-1.33 for second trimester; OR = 1.19, 95% CI, 0.99-1.44 for third trimester; OR = 1.53, 95% CI, 1.03-2.27 for the whole pregnancy) Positive trends between the acute exposure window (mean concentration of PM_2.5 in the last week and day of pregnancy) and risks of PROM and PPROM were also observed.

CONCLUSIONS

Exposure to ambient PM_2.5 during pregnancy was associated with the risk of PROM and PPROM.

Gestational hypertension and pre-eclampsia and risk of spontaneous premature rupture of membranes: A population-based cohort study

OBJECTIVE

To examine whether gestational hypertension and pre-eclampsia are associated with spontaneous premature rupture of membranes (PROM).

METHODS

A retrospective, population-based cohort study was conducted in Hebei, Zhejiang, and Jiangsu provinces in China from 1993 to 1995. After excluding women with missing data of exposure and outcome, history of chronic hypertension, multiple births, and babies with major birth defects and ambiguous sex, this study comprised 199 231 singleton live births. Logistic regression was used to evaluate the association, adjusting for potential confounders.

RESULTS

The incidence of PROM was 17.7% and 8.9% in women with gestational hypertension and pre-eclampsia, respectively, and 5.9% for the normotensive group. Compared with normotension, gestational hypertension was associated with an increase in the odds of PROM of 4.21 times (95% confidence interval [CI] 3.77-4.70), while pre-eclampsia had an increase of 2.27 times (95% CI 1.78-2.88). Additionally, women with hypertensive disorders of pregnancy had higher risks for term PROM (adjusted risk ratio [RR] 3.83, 95% CI 3.43-4.27) than preterm PROM (adjusted RR 3.10, 95% CI 2.18-4.41). Consistent results of the association were also observed in the sensitivity analyses.

CONCLUSION

Gestational hypertension and pre-eclampsia were associated with an increased risk for PROM. Increased odds were observed for term PROM compared with preterm PROM.

Insulin-like growth factor binding protein-1 predicts preterm premature rupture of membranes in twin pregnancies

PURPOSE

Mechanisms leading to preterm premature rupture of membranes (PPROM) remain incompletely defined. Based on the elevated occurrence of PPROM in twin gestations and recent studies of the involvement of insulin-like growth factor binding protein-1 (IGFBP-1) in the inhibition of collagen production we hypothesized that serum IGFBP-1 levels might be predictive of susceptibility to PPROM in women with twins.

METHODS

In this prospective study peripheral blood was obtained from 58 women with twin gestations prior to 20 weeks gestation and sera analyzed by ELISA for concentrations of IGFBP-1. Demographic and clinical outcome data were subsequently obtained and associations between IGFBP-1 and PPROM were analyzed by the Mann-Whitney test and receiver operator curve (ROC) analysis.

RESULTS

Eight of our subjects developed PPROM. They did not differ from the other women in demographics, medical history or current pregnancy outcome parameters. However, median IGFBP-1 levels were higher in women who subsequently developed PPROM (59.3 ng/ml) than in the other women (46.6 ng/ml) (p = 0.042). Using a cutoff value of 53.9 ng/ml the circulating IGFBP-1 level predicted development of PPROM with a sensitivity of 74%, specificity of 75%, a negative predictive value of 97% and a positive predictive value of 20%.

CONCLUSIONS

Pending validation in larger studies the findings suggest that determination of serum IGFBP-1 levels in women with twin pregnancies may predict the later development of PPROM.

In vitro and in vivo activities of flavonoids – apigenin, baicalin, chrysin, scutellarin – in regulation of hypertension – a review for their possible effects in pregnancy-induced hypertension

Flavonoids and their conjugates are the most important group of natural chemical compounds in drug discovery and development. The search for pharmacological activity and new mechanisms of activity of these chemical compounds, which may inhibit mediators of inflammation and influence the structure and function of endothelial cells, can be an interesting pharmacological strategy for the prevention and adjunctive treatments of hypertension, especially induced by pregnancy. Because cardiovascular diseases have multi-factorial pathogenesis these natural chemical compounds with wide spectrum of biological activities are the most interesting source of new drugs. Extracts from one of the most popular plant used in Traditional Chinese Medicine, Scutellaria baicalensis Georgi could be a very interesting source of flavonoids because of its exact content in quercetin, apigenin, chrysin and scutellarin as well as in baicalin. These flavonoids exert vasoprotective properties and many activities such as: anti-oxidative via several pathways, anti-in-flammatory, anti-ischaemic, cardioprotective and anti-hypertensive. However, there is lack of summaries of results of studies in context of potential and future application of flavonoids with determined composition and activity. Our review aims to provide a literature survey of in vitro, in vivo and ex vivo pharmacological studies of selected flavonoids (apigenin, chrysin and scutellarin, baicalin) in various models of hypertension carried out in 2008–2018.

Differential response of immortalized human amnion mesenchymal and epithelial cells against oxidative stress

Cells are equipped with various antioxidant defense factors to antagonize insults from reactive oxygen species (ROS), thus the antioxidant capacity has been characterized by a variety of cellular responses during the pathophysiological processes. Amniotic cells have been extensively applied in clinical practice for burn treatment, corneal repair, and tissue regeneration. However, the antioxidative properties of amniotic cells have not yet been fully understood. Therefore, the current study was aimed to observe the response of amniotic cells against ROS stimuli, and to investigate the underlying molecular mechanisms. The immortalized human amniotic mesenchymal cells (iHAMs) and immortalized human amniotic epithelial cells (iHAEs) were used. The human skin fibroblast (HSF) was used as a control cell line. Changes in intracellular ROS generation, cell viability, and cellular morphology were investigated to reveal the response of amniotic cells against oxidative stresses induced by x-rays and hydrogen peroxide. In addition, expression of apoptosis-related proteins and response to antioxidative stress was also examined. The intracellular ROS level and cell apoptosis in iHAMs was remarkably increased. iHAEs showed relatively high resistance to ROS stimulation, which can be attributed to the high SOD2 expression and up-regulation of Nrf2, HO-1 after x-rays exposure. In contrast, iHAMs were found sensitive to oxidative damage. Expression of caspase-3, caspase-8 and BAX was increased, whereas down-regulation of Bcl-xL, Nrf2, HO-1, and TrxR-1. Taken together, findings have highlighted the characterization of response of amniotic derived epithelial and mesenchymal cells to oxidative stress. In physiological processes, iHAMs may play an important role to maintain the homeostasis of the pregnancy environment. However, under oxidative stimulations, iHAEs provides protection against oxidative damage in amnion tissue.

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.

Incidence and risk factors of preterm premature rupture of membranes in singleton pregnancies at Siriraj Hospital

AIM

To obtain the incidence of preterm premature rupture of membranes (PPROM) at Siriraj Hospital during 2012-2016 and to identify its possible risk factors in singleton pregnancies.

METHODS

This study was a retrospective case-control study. The institutional ethical committee has approved the study. The medical records of eligible cases were reviewed. To assess the risk factors of PPROM, the data of the cases with PPROM in 2016 were compared with the data of pregnant women who did not have PPROM and delivered at term. Fifteen variables of interest were studied.

RESULTS

During the 5-year period, there were 43 727 deliveries at Siriraj Hospital and 1280 (2.93%) cases had PPROM. In 2016, 252 pregnant women were diagnosed PPROM and data of 199 cases were compared with the data of 199 control cases. Mean latency period was 2 days and mean gestational age at birth was 34.7 weeks in PPROM group. Logistic regression analysis showed that diabetes mellitus, poor weight gain and history of previous preterm birth were the factors that significantly associated with PPROM, with adjusted odds ratio (OR) 3.22 (95% confidence interval [CI] 1.47-7.05), 2.58 (95% CI 1.63-4.07) and 8.81 (95% CI 2.81-28.69), respectively (P < 0.05), while multiparity decreased the risk of PPROM (adjusted OR = 0.36, 95% CI 0.23-0.57) (P < 0.001).

CONCLUSION

The incidence of PPROM during 5-year period was 2.93%. Diabetes mellitus, poor maternal weight gain and history of previous preterm birth significantly increased risk of PPROM while multigravida reduced the risk.

Oxidative Stress as Cause, Consequence, or Biomarker of Altered Female Reproduction and Development in the Space Environment

Oxidative stress has been implicated in the pathophysiology of numerous terrestrial disease processes and associated with morbidity following spaceflight. Furthermore, oxidative stress has long been considered a causative agent in adverse reproductive outcomes. The purpose of this review is to summarize the pathogenesis of oxidative stress caused by cosmic radiation and microgravity, review the relationship between oxidative stress and reproductive outcomes in females, and explore what role spaceflight-induced oxidative damage may have on female reproductive and developmental outcomes.

Differential expression and methylation of integrin subunit alpha 11 and thrombospondin in the amnion of preterm birth

Objective

This study aimed to investigate the association between preterm birth and epigenetic mechanisms in the amnion.

Methods

We examined the association between differentially methylated regions (DMRs) and differentially expressed genes (DEG) using a cytosine-phosphate-guanine methylation array and whole-transcriptome sequencing from the amnion (preterm birth, n=5; full term, n=5). We enrolled 35 participants for mRNA expression analysis and pyrosequencing: 16 full-term and 19 preterm subjects. We compared the association of integrin subunit alpha 11 (ITGA11) and thrombospondin 2 (THBS2) gene methylation status with mRNA expression in the amnion.

Results

In the preterm birth group, methylation of ITGA11 and THBS2 genes was significantly lower (ITGA11 gene: 60.30% vs. 73.16%, P<0.05; THBS2 gene: 64.59% vs. 73.16%, P<0.05), and the expression of the genes was significantly higher than that in the full-term group (ITGA11 gene: 14.20 vs. 1.57, P<0.01; THBS2 gene: 1.18 vs. 10.34, P<0.05).

Conclusion

Methylation of the ITGA11 and THBS2 genes in the amnion was associated with preterm birth. Thus, ITGA11 and THBS2 gene methylation status in the amnion may be valuable in explaining the mechanism underlying preterm birth.

Roles of Progesterone Receptor Membrane Component 1 in Oxidative Stress-Induced Aging in Chorion Cells

INTRODUCTION

Oxidative stress-mediated fetal membrane cell aging is activated prematurely in preterm premature rupture of membranes (PPROMs). The mechanism of this phenomenon is largely understudied. Progesterone receptor membrane component 1 (PGRMC1) has been recognized as a potential protective component for maintaining fetal membrane integrity and healthy pregnancies. We aimed to investigate the effects of oxidative stress (represented by hydrogen peroxide [H₂O2]) on fetal membrane and chorion cell senescence, p38 mitogen-activated protein kinase (MAPK) phosphorylation, and sirtuin 3 (SIRT3) and to examine the roles of PGRMC1 in these effects.

METHODS

Following serum starvation for 24 hours, full-thickness fetal membrane explants and primary chorion cells were treated with H₂O2 at 100, 300, and 500 µM for 24 hours. Cells were fixed for cell senescence-associated β-galactosidase assay. Cell lysates were harvested for quantitive reverse transcription polymerase chain reaction to quantify SIRT3 messenger RNA. Cell lysates were harvested for Western blot to semi-quantify SIRT3 protein and p38 MAPK phosphorylation levels, respectively. To examine the role of PGRMC1, primary chorion cells underwent the same treatment mentioned above following PGRMC1 knockdown using validated PGRMC1-specific small-interfering RNA.

RESULTS

Hydrogen peroxide significantly induced cell senescence and p38 MAPK phosphorylation, and it significantly decreased SIRT3 expression in full-thickness fetal membrane explants and chorion cells. These effects were enhanced by PGRMC1 knockdown.

DISCUSSION

This study further demonstrated that oxidative stress-induced cell aging is one of the mechanisms of PPROM and PGRMC1 acts as a protective element for maintaining fetal membrane integrity by inhibiting oxidative stress-induced chorion cell aging.

Predictors of thallium exposure and its relation with preterm birth

Thallium (Tl) is a well-recognized hazardous toxic heavy metal that has been reported to have embryotoxicity and fetotoxicity. However, little is known about its association with preterm birth (PTB) in humans. We aimed to evaluate the predictors of Tl exposure and assessed its relation with PTB. The study population included 7173 mother-infant pairs from a birth cohort in Wuhan, China. Predictors of Tl concentrations were explored using linear regression analyses, and associations of Tl exposure with risk of PTB or gestational age at birth were estimated using logistic regression or generalized linear models. The geometric mean and median values of urinary Tl concentrations were 0.28 μg/L (0.55 μg/g creatinine) and 0.29 μg/L (0.53 μg/g creatinine). We found that maternal urinary Tl concentrations varied by gestational weight gain, educational attainment, multivitamin and iron supplementations. Women with Tl concentrations higher than 0.80 μg/g creatinine were at higher risk of giving birth prematurely versus those with Tl concentrations lower than 0.36 μg/g creatinine [adjusted odds ratio (95% confidence interval (CI)): 1.55 (1.05, 2.27)], and the association was more pronounced in PTB with premature rupture of membranes (PROM) rather than in PTB without PROM. About 3-fold increase in creatinine-corrected Tl concentrations were associated with 0.99-day decrease in gestational length (95% CI: -1.36, -0.63). This is the first report on the associations between maternal Tl exposure and the risk of PTB.

Computer modeling tools to understand the causes of preterm birth

The mechanical integrity of the soft tissue structures supporting the fetus may play a role in maintaining a healthy pregnancy and triggering the onset of labor. Currently, the level of mechanical loading on the uterus, cervix, and fetal membranes during pregnancy is unknown, and it is hypothesized that the over-stretch of these tissues contributes to the premature onset of contractility, tissue remodeling, and membrane rupture, leading to preterm birth. The purpose of this review article is to introduce and discuss engineering analysis tools to evaluate and predict the mechanical loads on the uterus, cervix, and fetal membranes. Here we will explore the potential of using computational biomechanics and finite element analysis to study the causes of preterm birth and to develop a diagnostic tool that can predict gestational outcome. We will define engineering terms and identify the potential engineering variables that could be used to signal an abnormal pregnancy. We will discuss the translational ability of computational models for the better management of clinical patients. We will also discuss the process of model validation and the limitations of these models. We will explore how we can borrow from parallel engineering fields to push the boundary of patient care so that we can work toward eliminating preterm birth.

Preterm prelabor rupture of the membranes: A disease of the fetal membranes

Preterm prelabor rupture of the membranes (pPROM) remains a significant obstetric problem that affects 3-4% of all pregnancies and precedes 40-50% of all preterm births. pPROM arises from complex, multifaceted pathways. In this review, we summarize some old concepts and introduce some novel theories related to pPROM pathophysiology. Specifically, we introduce the concept that pPROM is a disease of the fetal membranes where inflammation-oxidative stress axis plays a major role in producing pathways that can lead to membrane weakening through a variety of processes. In addition, we report microfractures in fetal membranes that are likely sites of tissue remodeling during gestation; however, increase in number and morphometry (width and depth) of these microfractures in pPROM membranes suggests reduced remodeling capacity of membranes. Microfractures can act as channels for amniotic fluid leak, and inflammatory cell and microbial migration. Further studies on senescence activation and microfracture formation and their role in maintaining membrane homeostasis are needed to fill the knowledge gaps in our understanding of pPROM as well as provide better screening (biomarker and imaging based) tools for predicting women at high risk for pPROM and subsequent preterm birth.

Pigment epithelial-derived factor in human fetal membranes

OBJECTIVE

Our main objective was to document, pigment epithelial-derived factor (PEDF), a secreted serine protease inhibitor with anti-angiogenic, anti-inflammatory, and anti-oxidant properties, expression in human fetal membranes from preterm prelabor rupture of the membranes (pPROM) and in in vitro cultures stimulated with cigarette smoke extract (CSE) or lipopolysaccharides (LPS), two major risk factors for pPROM (behavioral and bacterial, respectively).

METHOD

We documented PEDF mRNA expression in clinical samples of fetal membranes from patients with pPROM using quantitative RT-PCR. Also, mRNA and protein levels were documented in fetal membranes (from normal term cesarean sections [not in labor]) in an organ explant system stimulated with CSE or lipopolysaccharide (LPS). Immunohistochemistry (IHC) was used to localize PEDF in fetal membranes.

RESULTS

We report no changes in PEDF mRNA expression in pPROM compared to term births (p = .59) or after treatment with CSE or LPS. However, by adding sulforaphane the PEDF mRNA expression increased significantly p < .000032. PEDF was localized to both amnion and chorion layers, but no difference was seen in staining intensities after CSE or LPS treatment compared to control.

CONCLUSIONS

PEDF, a product of fetal membrane cells, is unaltered in pPROM or after exposure to risk factors of pPROM. The antioxidant stimulating substance sulforaphane contribute to an increase in PEDF mRNA in fetal membranes.

Adult Consequences of Extremely Preterm Birth: Cardiovascular and Metabolic Diseases Risk Factors, Mechanisms, and Prevention Avenues

Extremely preterm babies are exposed to various sources of injury during critical stages of development. The extremely preterm infant faces premature transition to ex utero physiology and undergoes adaptive mechanisms that may be deleterious in the long term because of permanent alterations in organ structure and function. Perinatal events can also directly cause structural injury. These disturbances induce morphologic and functional changes in their organ systems that might heighten their risks for later adult chronic diseases. This review examines the pathophysiology of programming of long-term health and diseases after preterm birth and associated perinatal risk factors.

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.

The relationship between the latency period, infection markers, and oxidant and antioxidant states in women with preterm premature rupture of membranes

BACKGROUND

A major cause of perinatal morbidity and mortality has been reported to be preterm premature rupture of membranes (PPROM). Our objective was to evaluate oxidant-antioxidant balance, infection parameters, time interval between rupture of membranes and delivery (latency period), and the relationship among all these parameters.

METHODS

Seventy-five cases with PPROM between 24 and 34 gestational weeks were included in the study. A control group of 41 women who gave birth at term were considered as the control group. The relationship among maternal plasma total oxidative stress (TOS), malondialdehyde (MDA), total antioxidant status (TAS), leukocyte counts, CRP, vitamin C and E levels, gestational week, neonatal birthweight, and latency period was evaluated.

RESULTS

In cases with PPROM, rupture occurred at an average of 29.4 gestational weeks and premature babies were born at an average of 31.6 gestational weeks. The mortality rate of babies born to PPROM women was 18.7% (14/75) died at or following birth. In the PPROM group, TOS, MDA, and leukocyte counts were found to be significantly higher compared to the control group (p < 0.001). Besides, a significant negative correlation was detected among the latency period, TOS, CRP, and leukocyte counts (p < 0.05).

CONCLUSIONS

Appropriate treatment protocols that strengthen antioxidant defense systems and taking into consideration the signs of infection can decrease the incidence of PPROM and/or mortality rates of babies born to PPROM women.

Anti-inflammatory Elafin in human fetal membranes

OBJECTIVE

Elafin is a low molecular weight protein with antileukoproteinase, anti-inflammatory, antibacterial and immunomodulating properties. The profile of Elafin in fetal membranes is not well characterized. This study determined the changes in Elafin expression and concentration in human fetal membrane from patients with preterm prelabor rupture of membranes (PPROM) and in vitro in response to intra-amniotic polymicrobial pathogens.

METHOD

Elafin messenger RNA (mRNA) expressions were studied in fetal membranes from PPROM, normal term as well as in normal term not in labor membranes in an organ explant system treated (24 h) with lipopolysaccharide (LPS), using quantitative reverse transcription-polymerase chain reaction (RT-PCR). Enzyme-linked immunosorbent assay (ELISA) measured Elafin concentrations in culture supernatants from tissues treated with LPS and polybacterial combinations of heat-inactivated Mycoplasma hominis (MH), Ureaplasma urealyticum (UU) and Gardnerella vaginalis (GV).

RESULTS

Elafin mRNA expression in fetal membranes from women with PPROM was significantly higher compared to women who delivered at term after normal pregnancy (5.09±3.50 vs. 11.71±2.21; P<0.05). In vitro, LPS-stimulated membranes showed a significantly increased Elafin m-RNA expression (P<0.05). However, the protein levels after LPS stimulation was not changed. Similarly, polymicrobial-treated fetal membranes also showed no changes in Elafin protein concentrations compared to untreated controls.

CONCLUSION

Higher Elafin expression in PPROM fetal membranes suggests a host response to an inflammatory pathology. However, lack of Elafin response to LPS and polymicrobial treatment is indicative of the minimal anti-inflammatory impact of this molecule in fetal membranes.

A Review on Various Uses of N-Acetyl Cysteine

N-acetyl cysteine (NAC), as a nutritional supplement, is a greatly applied antioxidant in vivo and in vitro. NAC is a precursor of L-cysteine that results in glutathione elevation biosynthesis. It acts directly as a scavenger of free radicals, especially oxygen radicals. NAC is a powerful antioxidant. It is also recommended as a potential treatment option for different disorders resulted from generation of free oxygen radicals. Additionally, it is a protected and endured mucolytic drug that mellows tenacious mucous discharges. It has been used for treatment of various diseases in a direct action or in a combination with some other medications. This paper presents a review on various applications of NAC in treatment of several diseases.

The relationship between macro- and micro-nutrients intake and risk of preterm premature rupture of membranes in pregnant women of Isfahan

BACKGROUND

Since preterm premature rupture of membranes (PPROM) is one of the most important complications of pregnancy and its relationship with nutrition status have not been surveyed comprehensively, we decided to study the relationship of maternal received nutrients (36 macro- and micro-nutrients) in three trimesters and PPROM which could be considered as a unique study.

MATERIALS AND METHODS

In this prospective cohort study, data was collected by filling a questionnaire through interviews with 620 pregnant women who had no parameters to affect pregnancy outcome. 48-hr dietary recalls were completed for eligible women at 11th-15th, 26th, 34th-37th weeks of gestation. Physical activity was also assessed using a standard questionnaire. Also pregnant mother's reproductive and demographic characteristic and supplementation are considered.

RESULTS

The mean value of received saturated fatty acids, polyunsaturated fatty acids and energy, in the first trimester (P < 0.001, P = 0.007, and P < 0.001 respectively), the mean values of calcium, sodium intake in the second trimester (P = 0.045, P = 0.006, and P = 0.004 respectively), Vitamins C, A (mg), β-carotene, cartenoids intake in the second trimester (P = 0.03, P = 0.001, P = 0.007, and P = 0.01 respectively), and higher Vitamin C intake during the first trimester (P = 0.02) was significantly greater among subjects with PPROM compared to the others.

CONCLUSIONS

The mean value of mentioned received nutrients in subjects who experienced PPROM later in pregnancy was higher than the others, which is independent of demographic and reproductive characteristic, estimated physical activity, and supplementation. Therefore, these findings could be considered in the nutritional programming for pregnant women to manage the risk of PPROM.

Oxidative stress in pregnancy and reproduction

Oxidative stress is implicated in the pathophysiology of many reproductive complications including infertility, miscarriage, pre-eclampsia, fetal growth restriction and preterm labour. The presence of excess reactive oxygen species can lead to cellular damage of deoxyribonucleic acids, lipids and proteins. Antioxidants protect cells from peroxidation reactions, limiting cellular damage and helping to maintain cellular membrane integrity. There is overwhelming evidence for oxidative stress causing harm in reproduction. However, there is sparse evidence that supplementation with commonly used antioxidants (mostly vitamins C and E) makes any difference in overcoming oxidative stress or reversing disease processes. There may be potential for antioxidant therapy to ameliorate or prevent disease, but this requires a thorough understanding of the mechanism of action and specificity of currently used antioxidants.

Prenatal Exposure to Nitrosatable Drugs, Dietary Intake of Nitrites, and Preterm Birth

Prenatal exposure to nitrosatable drugs, including secondary or tertiary amines, has been associated with preterm birth. Associations may be accentuated by higher intakes of dietary nitrites because of the increased formation of N-nitroso compounds. Using data from mothers of babies without major birth defects (controls) from the National Birth Defects Prevention Study, we examined the relationship between nitrosatable drug exposure in conjunction with dietary nitrite intake and preterm birth among 496 mothers of preterm infants and 5,398 mothers with full-term deliveries in 1997-2005. A protective association was observed with a high intake of plant nitrites (adjusted hazard ratio (AHR) = 0.72, 95% confidence interval (CI): 0.53, 0.97). Secondary amines in conjunction with high nitrite intake were associated with preterm birth during the first (AHR = 1.84, 95% CI: 1.14, 2.98), second (AHR = 1.89, 95% CI: 1.17, 3.07), and third (AHR = 2.00, 95% CI: 1.22, 3.29) trimesters. The adjusted hazard ratios for tertiary amine use in the third trimester by increasing tertiles of nitrite intake were 0.67 (95% CI: 0.35, 1.31), 1.25 (95% CI: 0.71, 2.19), and 2.02 (95% CI: 1.17, 3.49). Prenatal exposure to nitrosatable drugs, particularly secondary and tertiary amines, in conjunction with higher levels of dietary nitrite intake may increase the risk of preterm birth.

Granulocytic Myeloid-Derived Suppressor Cells Accumulate in Human Placenta and Polarize toward a Th2 Phenotype

Tolerance induction toward the semiallogeneic fetus is crucial to enable a successful pregnancy; its failure is associated with abortion or preterm delivery. Skewing T cell differentiation toward a Th2-dominated phenotype seems to be pivotal in maternal immune adaption, yet underlying mechanisms are incompletely understood. Myeloid-derived suppressor cells (MDSCs) are innate immune cells that mediate T cell suppression and are increased in cord blood of healthy newborns and in peripheral blood of pregnant women. In this study, we demonstrate that granulocytic MDSCs (GR-MDSCs) accumulate in human placenta of healthy pregnancies but are diminished in patients with spontaneous abortions. Placental GR-MDSCs effectively suppressed T cell responses by expression of arginase I and production of reactive oxygen species and were activated at the maternal-fetal interface through interaction with trophoblast cells. Furthermore, GR-MDSCs isolated from placenta polarized CD4(+) T cells toward a Th2 cytokine response. These results highlight a potential role of GR-MDSCs in inducing and maintaining maternal-fetal tolerance and suggest them as a promising target for therapeutic manipulation of pregnancy complications.

Umbilical cord blood markers of oxidative stress in pregnancies complicated by preterm prelabor rupture of membranes

OBJECTIVE

To determine umbilical cord blood total antioxidant capacity (TAC), ferric reducing antioxidant power (FRAP), thiobarbituric acid-reacting substances (TBARS), advanced glycation end products (AGEs) and markers of oxidative stress in pregnancies complicated by preterm prelabor rupture of membranes (PPROM) and their associations with microbial invasion of the amniotic cavity (MIAC) and/or histological chorioamnionitis (HCA), funisitis and selected aspects of short-term neonatal morbidity.

MATERIALS AND METHODS

One hundred and sixty-five women with singleton pregnancies complicated by PPROM were included in this study. Blood samples were obtained by venipuncture from the umbilical cord vein after the delivery of the newborn. The umbilical cord blood concentrations of TAC, FRAP, TBARS and AGEs were measured.

RESULTS

The presence of MIAC, HCA and funisitis did not show differences in the umbilical cord blood TAC, FRAP, TBARS and AGEs concentrations. Positive correlations were found between the gestational age at sampling and umbilical cord blood TAC and AGEs concentrations (TAC: rho = 0.26; p = 0.001; AGEs: rho = 0.35; p < 0.0001). There was no association between umbilical cord blood TAC, FRAP, TBARS and AGEs concentrations and selected aspects of short-term neonatal morbidity.

CONCLUSIONS

Oxidative stress is associated with PPROM, as indicated by the presence of markers tested in the umbilical cord blood; however, the evaluated oxidative stress markers are not influenced by the presence of MIAC and/or HCA, and funisitis or subsequent development of selected aspects of short-term neonatal morbidity.

Repeated measures of urinary oxidative stress biomarkers during pregnancy and preterm birth

OBJECTIVE

The purpose of this study was to investigate oxidative stress as a mechanism of preterm birth in human subjects; we examined associations between urinary biomarkers of oxidative stress that were measured at multiple time points during pregnancy and preterm birth.

STUDY DESIGN

This nested case-control study included 130 mothers who delivered preterm and 352 mothers who delivered term who were originally recruited as part of an ongoing prospective birth cohort at Brigham and Women's Hospital. Two biomarkers that included 8-hydroxydeoxyguanosine (8-OHdG) and 8-isoprostane were measured in urine samples that were collected at up to 4 time points (median 10, 18, 26, and 35 weeks) during gestation.

RESULTS

Urinary concentrations of 8-isoprostane and 8-OHdG decreased and increased, respectively, as pregnancy progressed. Average levels of 8-isoprostane across pregnancy were associated with increased odds of spontaneous preterm birth (adjusted odds ratio, 6.25; 95% confidence interval, 2.86-13.7), and associations were strongest with levels measured later in pregnancy. Average levels of 8-OHdG were protective against overall preterm birth (adjusted odds ratio, 0.19; 95% confidence interval, 0.10-0.34), and there were no apparent differences in the protective effect in cases of spontaneous preterm birth compared with cases of placental origin. Odds ratios for overall preterm birth were more protective in association with urinary 8-OHdG concentrations that were measured early in pregnancy.

CONCLUSION

Maternal oxidative stress may be an important contributor to preterm birth, regardless of subtype and timing of exposure during pregnancy. The 2 biomarkers that were measured in the present study had opposite associations with preterm birth; an improved understanding of what each represents may help to identify more precisely important mechanisms in the pathway to preterm birth.