Programmed cell death (apoptosis) as a possible pathway to metalloproteinase activation and fetal membrane degradation in premature rupture of membranes

Prenatal exposure to Benzo[a]pyrene affects maternal-fetal outcomes via placental apoptosis

Prenatal exposure to Benzo[a]pyrene (BaP) has been suggested to increase the risk of adverse pregnancy outcomes. However, the role of placental apoptosis on BaP reproductive toxicity is poorly understood. We conducted a maternal animal model of C57BL/6 wild-type (WT) and transformation-related protein 53 (Trp53) heterozygous knockout (p53KO) mice, as well as a nested case-control study involving 83 women with PB and 82 term birth from a birth cohort on prenatal exposure to BaP and preterm birth (PB). Pregnant WT and p53KO mice were randomly allocated to BaP treatment and control groups, intraperitoneally injected of low (7.8 mg/kg), medium (35 mg/kg), and high (78 mg/kg) doses of 3,4-BaP per day and equal volume of vegetable oil, from gestational day 10.5 until delivery. Results show that high-dose BaP treatment increased the incidence of preterm birth in WT mice. The number of fetal deaths and resorptions increased with increasing doses of BaP exposure in mice. Notably, significant reductions in maternal and birth weights, increases in placental weights, and decrease in the number of livebirths were observed in higher-dose BaP groups in dose-dependent manner. We additionally observed elevated p53-mediated placental apoptosis in higher BaP exposure groups, with altered expression levels of p53 and Bax/Bcl-2. In case-control study, the expression level of MMP2 was increased among women with high BaP exposure and associated with the increased risk of all PB and moderate PB. Our study provides the first evidence of BaP-induced reproductive toxicity and its adverse effects on maternal-fetal outcomes in both animal and population studies.

Stretch Causes cffDNA and HMGB1-Mediated Inflammation and Cellular Stress in Human Fetal Membranes

Danger-associated molecular patterns (DAMPs) are elevated within the amniotic cavity, and their increases correlate with advancing gestational age, chorioamnionitis, and labor. Although the specific triggers for their release in utero remain unclear, it is thought that they may contribute to the initiation of parturition by influencing cellular stress mechanisms that make the fetal membranes (FMs) more susceptible to rupture. DAMPs induce inflammation in many different tissue types. Indeed, they precipitate the subsequent release of several proinflammatory cytokines that are known to be key for the weakening of FMs. Previously, we have shown that in vitro stretch of human amnion epithelial cells (hAECs) induces a cellular stress response that increases high-mobility group box-1 (HMGB1) secretion. We have also shown that cell-free fetal DNA (cffDNA) induces a cytokine response in FM explants that is fetal sex-specific. Therefore, the aim of this work was to further investigate the link between stretch and the DAMPs HMGB1 and cffDNA in the FM. These data show that stretch increases the level of cffDNA released from hAECs. It also confirms the importance of the sex of the fetus by demonstrating that female cffDNA induced more cellular stress than male fetuses. Our data treating hAECs and human amnion mesenchymal cells with HMGB1 show that it has a differential effect on the ability of the cells of the amnion to upregulate the proinflammatory cytokines and propagate a proinflammatory signal through the FM that may weaken it. Finally, our data show that sulforaphane (SFN), a potent activator of Nrf2, is able to mitigate the proinflammatory effects of stretch by decreasing the levels of HMGB1 release and ROS generation after stretch and modulating the increase of key cytokines after cell stress. HMGB1 and cffDNA are two of the few DAMPs that are known to induce cytokine release and matrix metalloproteinase (MMP) activation in the FMs; thus, these data support the general thesis that they can function as potential central players in the normal mechanisms of FM weakening during the normal distension of this tissue at the end of a normal pregnancy.

Hydrogen sulfide inhibits the rupture of fetal membranes throngh anti-aging pathways

INTRODUCTION

To investigate the relationship between hydrogen sulfide(H2S) and the senescence level of the fetal membranes, and to elucidate how H2S affects the integrity of the fetal membranes.

METHODS

The H2S and the senescence levels of fetal membranes, and the expressions of H2S synthase CBS and CSE were detected in the preterm (PT) group and the preterm premature ruptured membranes (pPROM) group. The effects of H2S donors and knockdown of CBS on the senescence level of amniotic epithelial cells, and the expression level of matrix metalloproteinases (MMPs) and epithelial-mesenchymal translation (EMT) were observed.

RESULTS

The level of H2S in the fetal membranes in the pPROM group is significantly lower than that in the PT group matched for gestational age. The level of H2S is negatively correlated with the senescence level of fetal membranes. Treatment with H2S donors reduced cell senescence and MMPs expression, but did not affect EMT. CBS siRNA transfection accelerated the senescence of amniotic epithelial cells, and promoted the expression of MMPs and EMT occurrence, but l-cysteine could reverse these effects.

DISCUSSION

Our study suggests that H2S, through its anti-aging effect, can influence the expression of MMPs and EMT, thereby contributing to the maintenance of fetal membrane integrity.

Analysis of Maternal and Neonatal Outcome of Patients with Preterm Prelabor Rupture of Membranes

Background

Preterm prelabor rupture of membranes (PPROM) increases risk of maternal and neonatal diseases. Expectant treatment is one major treatment for PPROM patients, but it raises concerns on infection. Currently, the optimal delivery time for PPROM patients is still unclear, and there are various outcomes for the patients with PPROM. Previous studies conducted to analyze the pregnancy outcome showed inconsistent results. The purpose of this study is to retrospectively analyze the maternal and neonatal outcomes for comparison among different latency periods of patients with PPROM at a university hospital in China.

Method

This was a retrospective study. We divided all patients with PPROM into four groups according to gestational weeks, namely, group A (GA 24-27⁺⁶), group B (GA 28-31⁺⁶), group C (GA 32-33⁺⁶), and group D (GA34-36⁺⁶). The maternal and neonatal outcomes of each group were observed, respectively. Groups B and C were separately divided into two subgroups according to the median latency period of each group, namely, B1, B2, C1, and C2. Then, the differences of pregnancy outcomes between B1 and B2, C1 and C2, were compared, respectively. A p value < 0.05 was considered statistically significant.

Result

Group A: the common maternal and neonatal complications were the increased infection index before labour, neonatal hyperbilirubinemia and neonatal respiratory distress syndrome. Groups B, C, and D: the common maternal and neonatal complications were the increased infection index before labour, fetal distress, neonatal pneumonia, neonatal hyperbilirubinemia, and patent foramen ovale. Comparison of pregnancy outcome between group B1 and group B2 showed higher incidence rate of increased infection index before labour, lower incidence rate of respiratory distress syndrome, electrolyte disturbance, and premature brain in group B2 than those in group B1. Comparison of pregnancy outcome between group C1 and group C2 showed the higher incidence of increased infection index before labour, bigger birth weight, and shorter hospital stay in group C2 than those in group C1.

Conclusion

Increased infection index before labour was common maternal complication in four groups. Neonatal hyperbilirubinemia and neonatal pneumonia were top neonatal complications in four groups. The prolongation of latency period was beneficial to newborns of patients with gestational week at 28-31⁺⁶ weeks, while it did not benefit those with gestational week beyond 32 weeks.

Efficacy of long-term indomethacin therapy in prolonging pregnancy after fetoscopic laser surgery for twin-to-twin transfusion syndrome: a collaborative cohort study

OBJECTIVE

To evaluate the efficacy of long-term indomethacin therapy (LIT) in prolonging pregnancy and reducing spontaneous preterm birth (PTB) in patients undergoing fetoscopic laser surgery (FLS) for the management of twin-to-twin transfusion syndrome (TTTS).

DESIGN

Retrospective cohort study of prospectively collected data.

SETTING

Collaborative multicentre study.

POPULATION

Five hundred and fifty-seven consecutive TTTS cases that underwent FLS.

METHODS

Long-term indomethacin therapy was defined as indomethacin use for at least 48 hours. Log-binomial regression was used to estimate the relative risk of PTB in the LIT group compared with a non-LIT group. Cox regression was used to evaluate the association between LIT use and FLS-to-delivery survival.

MAIN OUTCOME MEASURES

Gestational age (GA) at delivery.

RESULTS

Among the 411 pregnancies included, a total of 180 patients (43.8%) received LIT after FLS and 231 patients (56.2%) did not. Median GA at fetal intervention did not differ between groups (20.4 weeks). Median GA at delivery was significantly higher in the LIT group (33.6 weeks) compared with the non-LIT group (31.1 weeks; P < 0.001). FLS-to-delivery interval was significantly longer in the LIT group (P < 0.001). The risks of PTB before 34, 32, 28 and 26 weeks of gestation were all significantly lower in the LIT group compared with the non-LIT group (relative risks 0.69, 0.51, 0.37 and 0.18, respectively). The number needed to treat with LIT to prevent one PTB before 32 weeks of gestation was four, and to prevent one PTB before 34 weeks was five.

CONCLUSION

Long-term indomethacin after FLS for TTTS was found to be associated with prolongation of pregnancy and reduced risk for PTB.

TWEETABLE ABSTRACT

Long-term indomethacin used after fetoscopic laser surgery for twin-to-twin transfusion syndrome is effective in prolonging pregnancy and reducing the risk for preterm birth; especially extreme preterm birth.

Cord serum elementomics profiling of 56 elements depicts risk of preterm birth: Evidence from a prospective birth cohort in rural Bangladesh

Maternal exposure to some individual rare earth elements and trace elements is associated with preterm birth, but few elements have been studied and little is known about the potential effect of simultaneous exposure to multiple elements. We examined individual and mixture effects of elements on preterm birth among 745 pregnant women in a prospective birth cohort in Bangladesh (2008-2011). We measured 56 elements in umbilical cord blood collected during delivery using inductively coupled plasma-mass spectrometry. Using elastic net (ENET) regularization and multivariate logistic regression, we examined independent associations between element concentrations and preterm birth. Bayesian kernel machine regression identified mixture effects of elements most critical to preterm birth, accounting for correlated exposure and interaction. ENET identified titanium (Ti), arsenic (As), and barium (Ba) as the most important predictors of shortened gestational age and preterm birth. In adjusted models, cord blood Ti (OR = 2.52; 95% CI: 1.08-5.93; P = 0.033), As (odds ratio (OR) = 1.34; 95% CI: 1.04-1.73; P = 0.023), and Ba (OR = 1.18; 95% CI: 1.02-1.38; P = 0.029) were significantly associated with preterm birth. Bayesian kernel machine regression suggested an interaction effect between As and Ba. Further, we constructed an element risk score (ERS) using estimated weights from a multivariate regression model for Ti, As, and Ba and regressed preterm birth by this score (OR = 2.72, 95% CI: 1.57-4.69; P = 3.35 × 10-4). Additionally, we observed a significant modification effect of child marriage on ERS, which means marriage before the age of 18 (Pinteraction = 0.0438). This study identified element exposures profiles in cord blood and constructed metal risk score that are jointly associated with the risk of preterm birth. Ti, As, and Ba exposure may adversely affect birth outcomes as well as child marriage may be a modifiable factor potentially affecting environmental element exposure and preterm birth.

Why Do the Fetal Membranes Rupture Early after Fetoscopy? A Review

Iatrogenic preterm premature rupture of the fetal membranes (iPPROM) remains the Achilles' heel of keyhole fetal surgery (fetoscopy) despite significant efforts in preclinical models to develop new therapies. This limited success is partially due to incomplete understanding why the fetal membranes rupture early after fetoscopy and notable differences in membrane physiology between humans and domestic species. In this review, we summarize aspects of fetoscopy that may contribute to iPPROM, the previous efforts to develop new therapies, and limitations of preclinical models commonly used in fetal membrane research.

Impact of Progesterone on Molecular Mechanisms of Preterm Premature Rupture of Membranes

The role and mechanisms of progesterone in preterm premature rupture of membranes (PPROM) remains unclear. This study aims to investigate the molecular mechanisms of action of progesterone in pre-labor full-term fetal amniotic membrane cells with and without stimulation by microbial, pro-inflammatory, or thrombogenic agents. Fetal amniotic membranes were collected from 30 women with a normal singleton pregnancy undergoing elective cesarean section at term prior to the onset of labor. The human amniotic epithelial cells isolated were pretreated with and without medroxyprogesterone acetate for 24 h. Then, cells were treated with and without TLR/NLR agonists, pro-inflammatory cytokines, or thrombin for 48 h. Semi-quantitative RT-PCR, Western blot, and caspase-3 activity measurement were performed. Progesterone stimulation decreased the expression of TLR2, TLR5, and Nod2 genes (alone and/or in combination with TLR/NLR agonists) and decreased the expression of IL-1β and IL-8 genes increased by stimulation with specific agonists for TLR2, TLR4, TLR5, Nod1, and Nod2. Moreover, progesterone decreased thrombin-induced IL-8 gene expression. Progesterone also decreased expression of Bax and Bid proteins (pro-apoptotic factors) increased by stimulation with pro-inflammatory cytokines (TNF-α, NGAL, IL-18, and IL-1β) and thrombin. Progesterone stimulation alone as well as co-stimulation with TNF-α, NGAL, IL-18, IL-1β, or thrombin with progesterone either increased, decreased, or did not change the expression of Bcl-2, Bcl-XL, or XIAP genes (anti-apoptotic factors). These data suggest progesterone plays protective roles against PPROM through anti-microbial, anti-inflammatory, and anti-thrombogenic actions on human-term fetal amniotic membrane cells. Progesterone alters pro-inflammatory cytokine- and thrombin-induced apoptosis by controlling the expression of pro-apoptotic and anti-apoptotic factors.

The role of apoptosis in the complex pathogenesis of the most common obstetrics and gynaecology diseases

Purpose

We aimed to assess the etiological role of apoptotic genes Bcl-2 and Bax in the background of major obstetric and gynaecological diseases.

Methods

Placental tissue samples were collected from 101 pregnancies with intrauterine growth restriction and 104 pregnancies with premature birth with 140 controll samples from term, eutrophic newborns. In addition, gene expression assessment of the genes Bax and Bcl-2 was performed in 101 uterine leiomyoma tissue samples at our disposal with 110 control cases. Gene expression levels were assessed by PCR method.

Results

The expression of the Bcl-2 gene was decreased in placental samples with intrauterine growth restriction. Significant overexpression of the proapoptotic Bax gene was detected in samples from premature infants. Antiapoptotic Bcl-2 gene expression was found to be significantly increased in fibroid tissues.

Conclusion

Apoptosis plays a crucial role in the development of the most common OB/GYN conditions. Decrease in the placental expression of the antiapoptotic gene Bcl-2 may upset the balance of programmed cell death.

MicroRNA Signature of Epithelial-Mesenchymal Transition in Group B Streptococcal Infection of the Placental Chorioamniotic Membranes

BACKGROUND

Infection-induced preterm birth is a major cause of neonatal mortality and morbidity and leads to preterm premature rupture of placental chorioamniotic membranes. The loss of amniotic epithelial cells and tensile strength preceding membrane rupture is poorly understood. We hypothesized that intrauterine bacterial infection induces changes in microRNA (miRNA) expression, leading to amniotic epithelial cell loss and membrane weakening.

METHODS

Ten pregnant pigtail macaques received choriodecidual inoculation of either group B Streptococcus (GBS) or saline (n = 5/group). Placental chorioamniotic membranes were studied using RNA microarray and immunohistochemistry. Chorioamniotic membranes from women with preterm premature rupture of membranes (pPROM) and normal term pregnancies were studied using transmission electron microscopy.

RESULTS

In our model, an experimental GBS infection was associated with changes in the miRNA profile in the chorioamniotic membranes consistent with epithelial to mesenchymal transition (EMT) with loss of epithelial (E-cadherin) and gain of mesenchymal (vimentin) markers. Similarly, loss of desmosomes (intercellular junctions) was seen in placental tissues from women with pPROM.

CONCLUSIONS

We describe EMT as a novel mechanism for infection-associated chorioamniotic membrane weakening, which may be a common pathway for many etiologies of pPROM. Therapy based on anti-miRNA targeting of EMT may prevent pPROM due to perinatal infection.

Maternal proximity to petrochemical industrial parks and risk of premature rupture of membranes

BACKGROUND

Living near petrochemical industries has been reported to increase the risks of adverse birth outcomes, such as low birth weight and preterm delivery. However, evidence regarding the role of petrochemical exposure in pregnancy complications remains limited. This study evaluated the association between maternal proximity to petrochemical industrial parks (PIPs) during pregnancy and the occurrence of premature rupture of membranes (PROM).

METHODS

We performed a population-based 1:3 case-control study by using the 2004-2014 Taiwanese Birth Certificate Database. Birth records reported as stillbirth or bearing congenital anomalies were excluded. Cases were newborns reported to have PROM, whereas controls were randomly sampled from those without any pregnancy complications by matching birth year and urbanization index of the residential township. The proximity to PIPs was evaluated by calculating the distance to the nearest PIP of the maternal residential township during pregnancy. Furthermore, petrochemical exposure opportunity, accounting for monthly prevailing wind direction, was quantified during the entire gestational period. We applied conditional logistic regression models to evaluate the associations.

RESULTS

In total, 29371 PROM cases were reported during the study period, with a corresponding 88113 healthy controls sampled. The results revealed that living within a 3-km radius of PIPs during pregnancy would increase the risk of PROM (odds ratio [OR] = 1.76, 95% CI: 1.66-1.87). Furthermore, compared with the lowest exposed group, those with high petrochemical exposure opportunity had a significantly increased risk of PROM occurrence (OR = 1.69-1.75). The adverse effects remained robust in the subgroup analysis for both term- and preterm-PROM.

CONCLUSIONS

The results of the present work provide evidence that living near PIPs during pregnancy would increase the risk of PROM, and additional studies are warranted to confirm our findings.

Mechanism of Human Fetal Membrane Biomechanical Weakening, Rupture and Potential Targets for Therapeutic Intervention

Using a novel in vitro model system combining biochemical/histologic with bioengineering approaches has provided significant insights into the physiology of fetal membrane weakening and rupture along with potential mechanistic reasons for lack of efficacy of currently clinically used agents to prevent preterm premature rupture of the membranes (pPROM) and preterm births. Likewise, the model has also facilitated screening of agents with potential for preventing pPROM and preterm birth.

Dynamic measurement of amnion thickness during loading by speckle pattern interferometry

INTRODUCTION

In previous studies on the mechanical parameters of amnions (AM), there is a limitation due to the lack of an accurate thickness measurement, which is an important parameter for determining AM-specific mechanical properties. As a bottleneck, the characterization of the basic mechanical properties of AM are greatly restricted, even with the proposal of fracture criteria.

METHOD

First, the initial thickness of the AM is estimated by the interpolated-volume-area method. Second, through combinations of our self-developed mini-biaxial tensile device with speckle pattern interferometry, this is the first time that researchers can accurately obtain the AM thickness at each transient moment in the process of loading.

RESULTS

Based on the experimental results, an accurate stress-strain curve could be obtained. Two important mechanical parameters-the fracture energy density and amnion rupture modulus-could be extracted as 0.184±0.036MPa and 108.57±17.32MPa, respectively. The fracture energy density and amnion rupture modulus provide objective criteria and a scientific basis for the evaluation of AM rupture.

DISCUSSION

The tensile stress-strain curve of a normal human amnion shows a distinct J-shape. This proves that the experimental results are basically reliable. Both important parameters --the fracture energy density and amnion rupture modulus, can be calculated from the stress-strain curve. Extracting these two parameters is critical for the evaluation and prediction of ROM, PROM and PPROM.

Modeling ascending infection with a feto-maternal interface organ-on-chip

Maternal infection (i.e., ascending infection) and the resulting host inflammatory response are risk factors associated with spontaneous preterm birth (PTB), a major pregnancy complication. However, the path of infection and its propagation from the maternal side to the fetal side have been difficult to study due to the lack of appropriate in vitro models and limitations of animal models. A better understanding of the propagation kinetics of infectious agents and development of the host inflammatory response at the feto-maternal (amniochorion-decidua, respectively) interface (FMi) is critical in curtailing host inflammatory responses that can lead to PTB. To model ascending infection and determine inflammatory responses at the FMi, we developed a microfluidic organ-on-chip (OOC) device containing primary cells from the FMi (decidua, chorion, and amnion [mesenchyme and epithelium]) and collagen matrix harvested from primary tissue. The FMi-OOC is composed of four concentric circular cell/collagen chambers designed to mimic the thickness and cell density of the FMi in vivo. Each layer is connected by arrays of microchannels filled with type IV collagen to recreate the basement membrane of the amniochorion. Cellular characteristics (viability, morphology, production of nascent collagen, cellular transitions, and migration) in the OOC were similar to those seen in utero, validating the physiological relevance and utility of the developed FMi-OOC. The ascending infection model of the FMi-OOC, triggered by exposing the maternal (decidua) side of the OOC to lipopolysaccharide (LPS, 100 ng mL-1), shows that LPS propagated through the chorion, amnion mesenchyme, and reached the fetal amnion within 72 h. LPS induced time-dependent and cell-type-specific pro-inflammatory cytokine production (24 h decidua: IL-6, 48 h chorion: GM-CSF and IL-6, and 72 h amnion mesenchyme and epithelium: GM-CSF and IL-6). Collectively, this OOC model and study successfully modeled ascending infection, its propagation, and distinct inflammatory response at the FMi indicative of pathologic pathways of PTB. This OOC model provides a novel platform to study physiological and pathological cell status at the FMi, and is expected to have broad utility in the field of obstetrics.

IL-37 Exerts Anti-Inflammatory Effects in Fetal Membranes of Spontaneous Preterm Birth via the NF-κB and IL-6/STAT3 Signaling Pathway

Spontaneous preterm birth (sPTB), defined as delivery before 37 weeks of gestation, is thought to be a multifactorial syndrome. However, the inflammatory imbalance at the maternal-fetal interface promotes excessive secretion of inflammatory factors and induces apoptosis and degradation of the extracellular matrix (ECM), which can subsequently lead to preterm birth. As an anti-inflammatory molecule in the IL-1 family, interleukin-37 (IL-37) mainly plays an inhibiting role in a variety of inflammatory diseases. However, as a typical inflammatory disease, no previous studies have been carried out to explore the role of IL-37 in sPTB. In this study, a series of molecular biological experiments were performed in clinical samples and human amniotic epithelial cell line (Wistar Institute Susan Hayflick (WISH)) to investigate the deficiency role of IL-37 and the potential mechanism. Firstly, the results indicated that the expression of IL-37 in human peripheral plasma and fetal membranes was significantly decreased in the sPTB group. Afterward, it is proved that IL-37 could significantly suppress the production of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) in WISH cells. Simultaneously, once silence IL-37, LPS-induced apoptosis and activity of matrix metalloproteinases (MMPs) 2 and 9 were significantly increased. In addition, the western blot data showed that IL-37 performed its biological effects by inhibiting the NF-κB and IL-6/STAT3 pathway. In conclusion, our results suggest that IL-37 limits excessive inflammation and subsequently inhibits ECM remodeling and apoptosis through the NF-κB and IL-6/STAT3 signaling pathway in the fetal membranes.

The Role of Danger Associated Molecular Patterns in Human Fetal Membrane Weakening

The idea that cellular stress (including that precipitated by stretch), plays a significant role in the mechanisms initiating parturition, has gained considerable traction over the last decade. One key consequence of this cellular stress is the increased production of Danger Associated Molecular Patterns (DAMPs). This diverse family of molecules are known to initiate inflammation through their interaction with Pattern Recognition Receptors (PRRs) including, Toll-like receptors (TLRs). TLRs are the key innate immune system surveillance receptors that detect Pathogen Associated Molecular Patterns (PAMPs) during bacterial and viral infection. This is also seen during Chorioamnionitis. The activation of TLR commonly results in the activation of the pro-inflammatory transcription factor Nuclear Factor Kappa-B (NF-kB) and the downstream production of pro-inflammatory cytokines. It is thought that in the human fetal membranes both DAMPs and PAMPs are able, perhaps via their interaction with PRRs and the induction of their downstream inflammatory cascades, to lead to both tissue remodeling and weakening. Due to the high incidence of infection-driven Pre-Term Birth (PTB), including those that have preterm Premature Rupture of the Membranes (pPROM), the role of TLR in fetal membranes with Chorioamnionitis has been the subject of considerable study. Most of the work in this field has focused on the effect of PAMPs on whole pieces of fetal membrane and the resultant inflammatory cascade. This is important to understand, in order to develop novel prevention, detection, and therapeutic approaches, which aim to reduce the high number of mothers suffering from infection driven PTB, including those with pPROM. Studying the role of sterile inflammation driven by these endogenous ligands (DAMPs) activating PRRs system in the mesenchymal and epithelial cells in the amnion is important. These cells are key for the maintenance of the integrity and strength of the human fetal membranes. This review aims to (1) summarize the knowledge to date pertinent to the role of DAMPs and PRRs in fetal membrane weakening and (2) discuss the clinical potential brought by a better understanding of these pathways by pathway manipulation strategies.

A cut-off value for systemic immune-inflammation index in the prediction of adverse neonatal outcomes in preterm premature rupture of the membranes

AIM

To determine a cut-off value for systemic immune-inflammation index (SII)(neutrophil × platelet /lymphocyte) in the prediction of adverse neonatal outcomes in preterm premature rupture of the membranes (PPROM).

METHODS

This retrospective cohort study was conducted among singleton pregnancies with PPROM. Cases were divided into two main groups: Group 1) PPROM diagnosed at 24th-28th weeks of gestation and Group 2) PPROM diagnosed at >28th-34th weeks of gestation. Thereafter, main study groups were divided into two subgroups: Subgroup A: pregnancies with favorable neonatal outcomes and Subgroup B: pregnancies with composite adverse neonatal outcomes. Subgroups were compared in terms of demographic features, clinical characteristics, laboratory test results and SII values. Furthermore, cut-off values of SII for the prediction of composite adverse neonatal outcomes were determined for two main groups. A Mann-Whitney U test was conducted to compare the median values and the chi-square test was used to compare categorical variables among the groups. Receiver operating characteristic (ROC) curves were used to assess the performance of SII value in predicting composite adverse neonatal outcomes.

RESULTS

Significant differences were observed for median platelet and SII values between the subgroups (P < 0.001 for both in group 1 and P = 0.002 and P = 0.005, respectively, in group 2). Cut-off values of 1695.14 10⁹ /L (83.3% sensitivity, 85.7% specificity) and 1430.90 × 10⁹ /L (71.4% sensitivity, 75.7% specificity) for composite adverse neonatal outcomes were determined, respectively in group 1 and 2 according to the ROC curve analysis.

CONCLUSION

SII may be used as an additional indicator for the prediction of adverse neonatal outcomes in PPROM.

Critical Impact of Human Amniotic Membrane Tension on Mitochondrial Function and Cell Viability In Vitro

Amniotic cells show exciting stem cell features, which has led to the idea of using living cells of human amniotic membranes (hAMs) in toto for clinical applications. However, under common cell culture conditions, viability of amniotic cells decreases rapidly, whereby reasons for this decrease are unknown so far. Recently, it has been suggested that loss of tissue tension in vivo leads to apoptosis. Therefore, the aim of this study was to investigate the effect of tissue distention on the viability of amniotic cells in vitro. Thereby, particular focus was put on vital mitochondria-linked parameters, such as respiration and ATP synthesis. Biopsies of hAMs were incubated for 7–21 days either non-distended or distended. We observed increased B-cell lymphoma 2-associated X protein (BAX)/B-cell lymphoma (BCL)-2 ratios in non-distended hAMs at day seven, followed by increased caspase 3 expression at day 14, and, consequently, loss of viability at day 21. In contrast, under distention, caspase 3 expression increased only slightly, and mitochondrial function and cellular viability were largely maintained. Our data suggest that a mechano-sensing pathway may control viability of hAM cells by triggering mitochondria-mediated apoptosis upon loss of tension in vitro. Further studies are required to elucidate the underlying molecular mechanisms between tissue distention and viability of hAM cells.

Toll-like receptor 4 activation on human amniotic epithelial cells is a risk factor for pregnancy loss

Background:

Maternal–fetal tolerance plays a fundamental role in the maintenance of pregnancy. However, this immunological tolerance can be influenced by intrauterine infections. Human amniotic epithelial cells (hAECs) have immunomodulatory effects and respond to invading pathogens through expressing various toll-like receptors (TLRs). We hypothesize that bacteria or bacterial products affect the immunosuppressive effects of hAECs through TLR stimulation. Here, we investigated how a successful pregnancy can be threatened by TLR4 activation on hAECs on lipopolysaccharide (LPS) engagement.

Materials and Methods:

hAECs were isolated from the amniotic membrane received from six healthy pregnant women. The immunophenotyping of hAECs was studied by flow cytometry. The isolated hAECs (4 × 10⁵ cells/ml) were cultured in 24-well plates in the presence or absence of LPS (5 μg/ml). After 24, 48, and 72 h of incubation, the culture supernatants of hAECs were collected, and the levels of interleukin-5 (IL-5), IL-6, IL-1β, tumor necrosis factor-alpha (TNF-α), transforming growth factor-beta 1 (TGF-β1), and prostaglandin E2 (PGE2) were measured by enzyme-linked immunosorbent assay.

Results:

TLR4 activation showed a stimulatory effect on TGF-β1 production of hAECs (P < 0.001–0.05). PGE2 production of LPS-stimulated hAECs was significantly increased (P < 0.01–0.05). Moreover, TLR4 could induce TNF-α and IL-1β production of hAECs (P < 0.0001–0.01), while this effect was not observed on IL-6 production of hAECs. The IL-5 was produced at a very low level in two culture supernatants of hAECs, in which its production was independent of LPS effect.

Conclusion:

TLR4 activation by bacterial components on hAECs may be a potential risk factor for pregnancy complications.

Drastic induction of MMP-7 by cortisol in the human amnion: implications for membrane rupture at parturition

Preterm premature rupture of fetal membranes precedes 30-40% of preterm births. Activation of matrix metalloproteases (MMPs) is the one of the major causes of extracellular matrix (ECM) degradation in membrane rupture. Increased cortisol, regenerated by 11β-hydroxysteroid dehydrogenase 1 in the amnion at parturition, is known to participate in a number of parturition-pertinent events. However, whether cortisol has a role in the regulation of MMPs in the membranes is not known. Here, we addressed this issue using human amnion tissue, the most tensile layer of the membranes. RNA-sequencing revealed that cortisol induced MMP7 expression dramatically in amnion fibroblasts, which was confirmed by real-time quantitative RT-PCR and Western blotting analysis in cortisol-treated amnion explants and fibroblasts. Measurement of collagen IV α5 chain (COL4A5), a substrate for MMP-7, showed that cortisol reduced its extracellular abundance, which was blocked by an antibody against MMP-7. Moreover, increased MMP-7 but decreased COL4A5 abundance was observed in the amnion tissue following labor-initiated spontaneous rupture of membranes. Mechanistic studies showed that cortisol increased the phosphorylation of c-Jun and the expression of c-Fos, the 2 major components of activated protein 1 (AP-1), respectively. The knocking down of c-Fos or c-Jun significantly attenuated the induction of MMP7 expression by cortisol. Chromatin immunoprecipitation assays showed that cortisol stimulated the enrichment of c-Fos and c-Jun at the AP-1 binding site in the MMP7 promoter. The data suggest that induction of MMP7 by cortisol via AP-1 may be a contributing factor to ECM degradation in membrane rupture at parturition.-Wang, L.-Y., Wang, W.-S., Wang, Y.-W., Lu, J.-W., Lu, Y., Zhang, C.-Y., Li, W.-J., Sun, K., Ying, H. Drastic induction of MMP-7 by cortisol in the human amnion: implications for membrane rupture at parturition.

The effect of lipopolysaccharide on anti-inflammatory and pro-inflammatory cytokines production of human amniotic epithelial cells

Intrauterine infection is a major cause of immune imbalance at the maternal-fetal interface, which leads to spontaneous abortion, premature rupture of the fetal membranes, and preterm birth. Human amniotic epithelial cells (hAECs) play a fundamental role in the maintenance of pregnancy. We hypothesize that bacteria influence the immunomodulatory effects of hAECs through stimulation of Toll-like receptors (TLRs). Here, we investigated how lipopolysaccharide (LPS) as a bacterial component affects anti-inflammatory and pro-inflammatory cytokines production of hAECs. Human placentas were obtained from six healthy pregnant women and hAECs were isolated. The phenotypic characteristics of hAECs were determined by flow cytometry. The hAECs (4 × 10⁵ cells/ml) were cultured in the presence or absence of LPS (5 μg/ml). The viability of the cells was assessed and culture supernatants of hAECs were collected after 24, 48 and 72 h of incubation. The levels of transforming growth factor-beta1 (TGF-β1), interleukin-4 (IL-4), tumor necrosis factor-alpha (TNF-α), interleukin-17 A (IL-17A), and interferon-gamma (IFN-γ) were measured by ELISA. Our data showed that LPS treatment did not affect the viability of hAECs, while had a stimulatory effect on TGF-β1 production of hAECs (p < 0.001). A significant reduction in IL-4 production of LPS-stimulated hAECs was observed (p < 0.05). LPS enhanced the production of TNF-α and IL-17 A of hAECs (p < 0.05-0.0001). The IFN-γ level was only detectable in two culture supernatants of hAECs, and the level was unchanged after stimulation with LPS. Based on these findings, LPS may play a pivotal role in immune imbalance at the feto-maternal interface through affecting anti-inflammatory and pro-inflammatory cytokines production of hAECs.

11β-HSD1 in Human Fetal Membranes as a Potential Therapeutic Target for Preterm Birth

Human parturition is a complex process involving interactions between the myometrium and signals derived from the placenta, fetal membranes, and fetus. Signals originating from fetal membranes are crucial components that trigger parturition, which is clearly illustrated by the labor-initiating consequence of membrane rupture. It has been recognized for a long time that among fetal tissues in late gestation the fetal membranes possess the highest capacity for cortisol regeneration by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). However, the exact role of this unique feature remains a mystery. Accumulating evidence indicates that this extra-adrenal source of cortisol may serve as an upstream signal for critical events in human parturition, including enhanced prostaglandin and estrogen synthesis as well as extracellular matrix remodeling. This may explain why such high capacity for cortisol regeneration develops in human fetal membranes at late gestation. Therefore, inhibition of 11β-HSD1 may provide a potential therapeutic target for prevention of preterm birth. This review summarizes the current understanding of the functional role of cortisol regeneration by 11β-HSD1 in human fetal membranes.

PROM and Labour Effects on Urinary Metabolome: A Pilot Study

Since pathologies and complications occurring during pregnancy and/or during labour may cause adverse outcomes for both newborns and mothers, there is a growing interest in metabolomic applications on pregnancy investigation. In fact, metabolomics has proved to be an efficient strategy for the description of several perinatal conditions. In particular, this study focuses on premature rupture of membranes (PROM) in pregnancy at term. For this project, urine samples were collected at three different clinical conditions: out of labour before PROM occurrence (Ph1), out of labour with PROM (Ph2), and during labour with PROM (Ph3). GC-MS analysis, followed by univariate and multivariate statistical analysis, was able to discriminate among the different classes, highlighting the metabolites most involved in the discrimination.

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.

The preterm cervix reveals a transcriptomic signature in the presence of premature prelabor rupture of membranes

BACKGROUND

Premature prelabor rupture of fetal membranes accounts for 30% of all premature births and is associated with detrimental long-term infant outcomes. Premature cervical remodeling, facilitated by matrix metalloproteinases, may trigger rupture at the zone of the fetal membranes overlying the cervix. The similarities and differences underlying cervical remodeling in premature prelabor rupture of fetal membranes and spontaneous preterm labor with intact membranes are unexplored.

OBJECTIVES

We aimed to perform the first transcriptomic assessment of the preterm human cervix to identify differences between premature prelabor rupture of fetal membranes and preterm labor with intact membranes and to compare the enzymatic activities of matrix metalloproteinases-2 and -9 between premature prelabor rupture of fetal membranes and preterm labor with intact membranes.

STUDY DESIGN

Cervical biopsies were collected following preterm labor with intact membranes (n = 6) and premature prelabor rupture of fetal membranes (n = 5). Biopsies were also collected from reference groups at term labor (n = 12) or term not labor (n = 5). The Illumina HT-12 version 4.0 BeadChips microarray was utilized, and a novel network graph approach determined the specificity of changes between premature prelabor rupture of fetal membranes and preterm labor with intact membranes. Quantitative reverse transcription-polymerase chain reaction and Western blotting confirmed the microarray findings. Immunofluorescence was used for localization studies and gelatin zymography to assess matrix metalloproteinase activity.

RESULTS

PML-RARA-regulated adapter molecule 1, FYVE-RhoGEF and PH domain-containing protein 3 and carcinoembryonic antigen-ralated cell adhesion molecule 3 were significantly higher, whereas N-myc downstream regulated gene 2 was lower in the premature prelabor rupture of fetal membranes cervix when compared with the cervix in preterm labor with intact membranes, term labor, and term not labor. PRAM1 and CEACAM3 were localized to immune cells at the cervical stroma and NDRG2 and FGD3 were localized to cervical myofibroblasts. The activity of matrix metalloproteinase-9 was higher (1.22 ± 4.403-fold, P < .05) in the cervix in premature prelabor rupture of fetal membranes compared with preterm labor with intact membranes.

CONCLUSION

We identified 4 novel proteins with a potential role in the regulation of cervical remodeling leading to premature prelabor rupture of fetal membranes. Our findings contribute to the studies dissecting the mechanisms underlying premature prelabor rupture of fetal membranes and inspire further investigations toward the development of premature prelabor rupture of fetal membranes therapeutics.

Redefining 3Dimensional placental membrane microarchitecture using multiphoton microscopy and optical clearing

INTRODUCTION

Remodeling of human placental membranes (amniochorionic or fetalmembrane) throughout gestation, a necessity to accommodate increasing uterine volume, involves continuous alterations (replacement of cells and remodeling of extracellular matrix). Methodologic limitations have obscured microscopic determination of cellular and layer-level alterations. This study used a combination of advanced imaging by multiphoton autofluorescence microscopy (MPAM) and second harmonic generation (SHG) microscopy along with tissue optical clearing to characterize the 3Dimensional multilayer organization of placental membranes.

METHODS

Placental membranes biopsies (6 mm) collected from term, not-in-labor cesarean deliveries (n = 7) were fixed in 10% formalin (native) or treated with 2,2'-thiodiethanol to render them transparent for deeper imaging. Native and cleared tissues were imaged using MPAM (cellular autofluorescence) and SHG (fibrillar collagen). Depth z-stacks captured the amnion epithelium, underlying matrix layers, and in the cleared biopsies, the decidua layer.

RESULTS

MPAM and SHG revealed fetal membrane epithelial topography and collagen organization in multiple matrix layers. Term amnion layers showed epithelial shedding and gaps. Optical clearing provided full-depth imaging with improved visualization of collagen structure, mesenchymal cells in extracellular matrix layers, and decidua morphology. Layer thicknesses measured by imaging corroborated with histology. Mosaic tiling of MPAM/SHG image stacks allowed large area visualization of entire biopsies.

CONCLUSION

MPAM-SHG microscopy allowed for study of this multi-layered tissue and revealed shedding, gap formation, and other structural changes. This approach could be used to study structural changes associated with membranes as well as other uterine tissues to better understand events in normal and abnormal parturition.

Expression patterns of the chromosome 21 MicroRNA cluster (miR-99a, miR-125b and let-7c) in chorioamniotic membranes

Trisomy 21 (T21) is the most common chromosome abnormality in humans and is associated with a spectrum of phenotypes, including cognitive impairment, congenital heart defects and immune system defects. In addition, T21 is also associated with abnormalities of fetal membranes including chorioamniotic separation, delayed fusion of the chorioamniotic membranes, defects in syncytiotrophoblast formation, as well as amniocyte senescence. There is evidence indicating miRNAs encoded by sequences on chromosome 21 (Chr-21) are involved in several of the cognitive and neurological phenotypes of T21, but the role of Chr-21 derived miRNAs in fetal membrane abnormalities associated with T21 has not been investigated. In the current study, we determined the expression patterns of three miRNAs derived from a cluster on Chr-21 - hsa-miR-99a, hsa-miR-125b and hsa-let-7c in chorioamniotic membranes obtained from term pregnancies with spontaneous rupture (n = 20). Tissue and location specific expression patterns within the chorioamniotic membranes were identified. The rupture zone in the choriodecidua had distinct expression patterns compared to other fetal membrane locations. Despite the increased gene dosage associated with T21, the expression of all three miRNAs was reduced in cultured T21 amniocytes as compared to cultured euploid amniocytes. In silico analysis of experimentally validated targets of the three miRNAs suggest these Chr-21 derived miRNAs play a potential role in fetal membrane rupture and the fetal membrane defects associated with T21.

Induction of Amnion Epithelial Apoptosis by Cortisol via tPA/Plasmin System

Rupture of fetal membranes (ROM) can initiate parturition at both term and preterm birth. Apoptosis of the amnion epithelium plays a key role in structural remodeling of the membranes preceding ROM. However, the causative factors for apoptosis remain unidentified. Toward the end of gestation, a feed-forward regeneration of cortisol via 11β-hydroxysteroid dehydrogenase 1 exists in the fetal membranes. Here, we have examined whether cortisol accumulation is a causative factor for amnion cells apoptosis. By using primary human amnion epithelial and fibroblast cells, we demonstrated cortisol induced apoptosis specifically in epithelial cells but not in fibroblasts via reciprocal regulation of tissue-type plasminogen activator (tPA)/plasmin system. Cortisol increased PLAT expression, the gene encoding tPA, via glucocorticoid receptor binding to a glucocorticoid response element in PLAT promoter, thereby increasing plasmin activity in epithelial cells. Further study revealed that a Fas-mediated extrinsic apoptotic pathway was involved in the induction of epithelial cells apoptosis by cortisol, which was blocked by inhibiting either tPA or plasmin. Consistently, cortisol increased cleaved-caspase-3 and tPA abundance in amnion tissue explants. Moreover, the abundance of cortisol, cleaved-caspase-3, and tPA was significantly increased in amnion tissue after labor-initiated spontaneous rupture of membranes. In conclusion, local accumulation of cortisol is a causative factor for amnion epithelial apoptosis via activation of tPA/plasmin system toward the end of gestation. This may contribute to the ROM at both term and preterm birth.

The Role of Matrix Degrading Enzymes and Apoptosis in Repture of Membranes

Prematurity is the third leading cause of perinatal death, and preterm premature rupture of the membranes (pPROM) is associated with approximately 20-50% of all preterm births. The etiologic factors described for pPROM and preterm labor (PTL) are the same, although the clinical presentation (pPROM vs PTL) differs among patients. The reason for this disparity is unknown and poses a therapeutic dilemma. Several etiologic factors have been described for PTL and pPROM. PTL and pPROM are associated with overwhelming host inflammatory response. Many of these pro-inflammatory factors (inflammatory cytokine release) are common in both conditions; however, the clinical presentation differs. The objective of this review is to explain the differential expression pattern of matrix metalloproteinases (MMPs) and pro-apoptotic elements in human fetal membranes in pPROM and PTL and how they interact to present different clinical outcomes during pregnancy.

The physiology of fetal membrane weakening and rupture: Insights gained from the determination of physical properties revisited

Rupture of the fetal membranes (FM) is precipitated by stretch forces acting upon biochemically mediated, pre-weakened tissue. Term FM develop a para-cervical weak zone, characterized by collagen remodeling and apoptosis, within which FM rupture is thought to initiate. Preterm FM also have a weak region but are stronger overall than term FM. Inflammation/infection and decidual bleeding/abruption are strongly associated with preterm premature FM rupture (pPROM), but the specific mechanisms causing FM weakening-rupture in pPROM are unknown. There are no animal models for study of FM weakening and rupture. Over a decade ago we developed equipment and methodology to test human FM strength and incorporated it into a FM explant system to create an in-vitro human FM weakening model system. Within this model TNF (modeling inflammation) and Thrombin (modeling bleeding) both weaken human FM with concomitant up regulation of MMP9 and cellular apoptosis, mimicking the characteristics of the spontaneous FM rupture site. The model has been enhanced so that test agents can be applied directionally to the choriodecidual side of the FM explant consistent with the in-vivo situation. With this enhanced system we have demonstrated that the pathways involving inflammation/TNF and bleeding/Thrombin induced FM weakening overlap. Furthermore GM-CSF production was demonstrated to be a critical common intermediate step in both the TNF and the Thrombin induced FM weakening pathways. This model system has also been used to test potential inhibitors of FM weakening and therefore pPROM. The dietary supplement α-lipoic acid and progestogens (P4, MPA and 17α-hydroxyprogesterone) have been shown to inhibit both TNF and Thrombin induced FM weakening. The progestogens act at multiple points by inhibiting both GM-CSF production and GM-CSF action. The use of a combined biomechanical/biochemical in-vitro human FM weakening model system has allowed the pathways of fetal membrane weakening to be delineated, and agents that may be of clinical use in inhibiting these pathways to be tested.

Oxidative stress damage-associated molecular signaling pathways differentiate spontaneous preterm birth and preterm premature rupture of the membranes

STUDY HYPOTHESIS

In women with preterm premature rupture of the membranes (PPROM), increased oxidative stress may accelerate premature cellular senescence, senescence-associated inflammation and proteolysis, which may predispose them to rupture.

STUDY FINDING

We demonstrate mechanistic differences between preterm birth (PTB) and PPROM by revealing differences in fetal membrane redox status, oxidative stress-induced damage, distinct signaling pathways and senescence activation.

WHAT IS KNOWN ALREADY

Oxidative stress-associated fetal membrane damage and cell cycle arrest determine adverse pregnancy outcomes, such as spontaneous PTB and PPROM.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

Fetal membranes and amniotic fluid samples were collected from women with PTB and PPROM. Molecular, biochemical and histologic markers were used to document differences in oxidative stress and antioxidant enzyme status, DNA damage, secondary signaling activation by Ras-GTPase and mitogen-activated protein kinases, and activation of senescence between membranes from the two groups.

MAIN RESULTS AND THE ROLE OF CHANCE

Oxidative stress was higher and antioxidant enzymes were lower in PPROM compared with PTB. PTB membranes had minimal DNA damage and showed activation of Ras-GTPase and ERK/JNK signaling pathway with minimal signs of senescence. PPROM had higher numbers of cells with DNA damage, prosenescence stress kinase (p38 MAPK) activation and signs of senescence.

LIMITATIONS, REASONS FOR CAUTION

Samples were obtained retrospectively after delivery. The markers of senescence that we tested are specific but are not sufficient to confirm senescence as the pathology in PPROM.

WIDER IMPLICATIONS OF THE FINDINGS

Oxidative stress-induced DNA damage and senescence are characteristics of fetal membranes from PPROM, compared with PTB with intact membranes. PTB and PPROM arise from distinct pathophysiologic pathways. Oxidative stress and oxidative stress-induced cellular damages are likely determinants of the mechanistic signaling pathways and phenotypic outcome.

STUDY FUNDING AND COMPETING INTERESTS

This study is supported by developmental funds to Dr R. Menon from the Department of Obstetrics and Gynecology at The University of Texas Medical Branch at Galveston and funds to Dr M. Kacerovský from the Ministry of Health Czech Republic (UHHK, 001799906). The authors report no conflict of interest.

Sulfasalazine augments a pro-inflammatory response in interleukin-1β-stimulated amniocytes and myocytes

Preterm birth occurs in 10% of pregnancies and is a major cause of neonatal morbidity and mortality. The majority of cases of early preterm labour are associated with infection/inflammation, which places the fetal central nervous system at risk. Targeting immune activation is therefore an appealing therapeutic strategy for the prevention of preterm labour and neonatal brain injury. The expression of many labour-associated and inflammatory-response genes is controlled by the transcription factors nuclear factor-κB (NF-κB) and activator protein-1 (AP-1), which makes them therapeutic targets of interest. Sulfasalazine (SASP) has been shown to inhibit NF-κB and reduce lipopolysaccharide-induced cytokine concentrations in fetal membrane explants and reduce the rate of Escherichia coli-induced preterm labour in mice. Its effects upon AP-1 in the context of pregnancy are unknown. In this study the effect of SASP on interleukin-1β (IL-1β) -induced NF-κB and AP-1 activity, cytokine production and cyclo-oxygenase-2 (COX-2) expression was examined in amniocytes and myocytes. A supra-therapeutic concentration (5 mm) was required to inhibit IL-1β-induced NF-κB (P < 0·0001) in amniocytes and IL-1β-induced NF-κB (P < 0·01), AP-1 (P < 0·01) and COX-2 (P < 0·05) in myocytes. Despite inhibiting IL-1β-induced cytokines, a basal increase in IL-6 (P < 0·01), IL-8 (P < 0·0001) and tumour necrosis factor-α (TNF-α) (P < 0·001) was seen with 5 mm SASP in amniocytes, and significant cytotoxic effects were seen in myocytes. The therapeutic concentration of 0·015 mm had no inhibitory effects on pro-inflammatory mediators, but led to an augmented response to IL-1β-induced IL-6 (P < 0·01), IL-8 (P < 0·05) and TNF-α (P < 0·05) in amniocytes and IL-8 (P < 0·05) in myocytes. SASP is therefore an unlikely therapeutic candidate for the prevention of inflammation-induced preterm labour.

Oxidative stress damage as a detrimental factor in preterm birth pathology

Normal term and spontaneous preterm births (PTB) are documented to be associated with oxidative stress (OS), and imbalances in the redox system (balance between pro- and antioxidant) have been reported in the maternal-fetal intrauterine compartments. The exact mechanism of labor initiation either at term or preterm by OS is still unclear, and this lack of understanding can partially be blamed for failure of antioxidant supplementation trials in PTB prevention. Based on recent findings from our laboratory, we postulate heterogeneity in host OS response. The physiologic (at term) and pathophysiologic (preterm) pathways of labor are not mediated by OS alone but by OS-induced damage to intrauterine tissues, especially fetal membranes of the placenta. OS damage affects all major cellular elements in the fetal cells, and this damage promotes fetal cell senescence (aging). The aging of the fetal cells is predominated by p38 mitogen activated kinase (p38MAPK) pathways. Senescing cells generate biomolecular signals that are uterotonic, triggering labor process. The aging of fetal cells is normal at term. However, aging is premature in PTB, especially in those PTBs complicated by preterm premature rupture of the membranes, where elements of redox imbalances and OS damage are more dominant. We postulate that fetal cell senescence signals generated by OS damage are likely triggers for labor. This review highlights the mechanisms involved in senescence development at term and preterm by OS damage and provides insight into novel fetal signals of labor initiation pathways.

Synergy and interactions among biological pathways leading to preterm premature rupture of membranes

Preterm premature rupture of membranes (PPROM) occurs in 1% to 2% of births. Impact of PPROM is greatest in low- and middle-income countries where prematurity-related deaths are most common. Recent investigations identify cytokine and matrix metalloproteinase activation, oxidative stress, and apoptosis as primary pathways to PPROM. These biological processes are initiated by heterogeneous etiologies including infection/inflammation, placental bleeding, uterine overdistention, and genetic polymorphisms. We hypothesize that pathways to PPROM overlap and act synergistically to weaken membranes. We focus our discussion on membrane composition and strength, pathways linking risk factors to membrane weakening, and future research directions to reduce the global burden of PPROM.

Histological evidence of oxidative stress and premature senescence in preterm premature rupture of the human fetal membranes recapitulated in vitro

Preterm prelabor rupture of the membranes (pPROM) may lead to preterm births (PTBs). We investigated premature senescence of fetal membranes in women with pPROM and spontaneous PTB with intact membranes (<34 weeks) and the inducibility fetal membrane senescence phenotype by oxidative stress in vitro. IHC was performed for p53, p21, and phospho (p)-p38 mitogen-activated protein kinase (MAPK) as markers of senescence phenotype in pPROM, PTBs, and term births. Term fetal membranes were exposed to cigarette smoke extract to induce oxidative stress. Western blots documented p-p53 and p-p38 MAPK. Transmission electron microscopy assessed cellular morphologic features in clinical and cigarette smoke extract-treated membranes. A total of 80% of pPROM cells and >60% of term cells were positive for all three senescence phenotype markers, and concentrations were higher than in PTBs (P < 0.05). p53 staining was comparable in membranes from PTB and term birth pregnancies, whereas only <30% and <45% of cells were positive for p21 and p38 MAPK, respectively. In vitro cigarette smoke extract exposure increased p-p38 MAPK without any detectable change in p-p53 MAPK. Enlargement of organelles consistent with senescence phenotype was evident in pPROM and term membranes in vivo and after cigarette smoke extract treatment in vitro but was less apparent in PTBs. Histologic and biochemical resemblance of pPROM and term membranes suggests premature senescence of the membranes is a mechanistic feature in pPROM, and this can be phenocopied in an in vitro model.

Group B streptococcal infection of the choriodecidua induces dysfunction of the cytokeratin network in amniotic epithelium: a pathway to membrane weakening

Early events leading to intrauterine infection remain poorly defined, but may hold the key to preventing preterm delivery. To determine molecular pathways within fetal membranes (chorioamnion) associated with early choriodecidual infection that may progress to preterm premature rupture of membranes (PPROM), we examined the effects of a Group B Streptococcus (GBS) choriodecidual infection on chorioamnion in a nonhuman primate model. Ten chronically catheterized pregnant monkeys (Macaca nemestrina) at 118–125 days gestation (term = 172 days) received choriodecidual inoculation of either GBS (n = 5) or saline (n = 5). Cesarean section was performed in the first week after GBS or saline inoculation. RNA extracted from chorioamnion (inoculation site) was profiled by microarray. Single gene, Gene Set, and Ingenuity Pathway Analysis results were validated using qRT-PCR (chorioamnion), Luminex (amniotic fluid, AF), immunohistochemistry, and transmission electron microscopy (TEM). Despite uterine quiescence in most cases, significant elevations of AF cytokines (TNF-α, IL-8, IL-1β, IL-6) were detected in GBS versus controls (p<0.05). Choriodecidual infection resolved by the time of cesarean section in 3 of 5 cases and GBS was undetectable by culture and PCR in the AF. A total of 331 genes were differentially expressed (>2-fold change, p<0.05). Remarkably, GBS exposure was associated with significantly downregulated expression of multiple cytokeratin (CK) and other cytoskeletal genes critical for maintenance of tissue tensile strength. Immunofluorescence revealed highly significant changes in the CK network within amniocytes with dense CK aggregates and retraction from the cell periphery (all p = 0.006). In human pregnancies affected by PPROM, there was further evidence of CK network retraction with significantly shorter amniocyte foot processes (p = 0.002). These results suggest early choriodecidual infection results in decreased cellular membrane integrity and tensile strength via dysfunction of CK networks. Downregulation of CK expression and perturbations in the amniotic epithelial cell intermediate filament network occur after GBS choriodecidual infection, which may contribute to PPROM.

Group B Streptococcus (GBS) is one cause of preterm birth, stillbirth, and fetal brain injury. GBS is present in the vagina and is thought to ascend into the uterus of some women where it can cause placental inflammation and preterm birth. Understanding the earliest events in the placenta that lead to preterm birth is elusive in humans, because the placenta cannot be studied until after birth. Here, we use a nonhuman primate model to show that an early GBS infection can damage the structural support of the fetal membranes, specifically the cytokeratin network in the epithelium of the amnion (one part of the membranes). Next, we obtained human placentas to show that this cytokeratin network was also damaged in human patients that had preterm premature rupture of the membranes, a major cause of preterm birth. Our work is important in understanding why fetal membranes may rupture prematurely, which may lead to early interventions to prevent membrane damage after placental infection and preterm birth.

Air pollution and preterm premature rupture of membranes: a spatiotemporal analysis

Preterm premature rupture of membranes (PROM) is the leading identifiable predisposing factor for preterm birth. Although maternal exposure to air pollution can potentially have an impact on preterm PROM, there is no available evidence on such an impact. In this study, based on 5,555 singleton births occurring in Barcelona, Spain (2002-2005), we investigated the associations of maternal exposure to nitrogen dioxide, nitrogen oxides, and particulate matter with aerodynamic diameters of ≤2.5 µm (PM2.5), 2.5 µm-10 µm, and ≤10 µm and PM2.5 light absorption with preterm PROM and gestational age at the rupture of membranes (ROM). We utilized temporally adjusted land-use regression models to predict pollutant levels at each subject's home address during each week of her pregnancy. We conducted matched (according to the length of exposure) case-control analyses to estimate the preterm PROM risk associated with 1 interquartile-range increase in exposure levels during the entire pregnancy and during the last 3 months prior to ROM. We found an increase in preterm PROM risk of up to 50% (95% confidence interval: 4, 116) and a 1.3-day (95% confidence interval: -1.9, -0.6) reduction in gestational age at ROM associated with PM2.5 absorbance, nitrogen dioxide exposure, and nitrogen oxide exposure during the entire pregnancy and the last 3 months prior to ROM.

Class I to III histone deacetylases differentially regulate inflammation-induced matrix metalloproteinase 9 expression in primary amnion cells

Matrix metalloproteinase (MMP) 9 plays an important role in the degradation of the extracellular matrix in fetal membranes, and pathological activation of MMP-9 can lead to preterm birth. In nongestational tissues, modulation of histone deacetylases (HDACs) regulates MMP-9 expression. The aim of this study was to determine whether class I to III HDACs regulate MMP-9 expression and activity in primary amnion cells. Class I and II HDAC regulation of MMP-9 was assessed using the general class I and II HDAC inhibitors (HDACi) trichostatin A (TSA) and suberoylanilide hydroxamic acid (SAHA), the class I HDACi MS-275, and the class II HDACi MC1568. Class III HDAC regulation of MMP-9 was assessed using the SIRT1 activators resveratrol and SRT1720 as well as SIRT1 small interfering RNA (siRNA). Primary amnion epithelial cells were incubated with 1 ng/mL interleukin (IL) 1β in the absence or presence of 0.3 μmol/L TSA, 5 μmol/L SAHA, 2.5 μmol/L MS-275, 2.5 μmol/L MC1568, 50 μmol/L resveratrol, or 10 μmol/L SRT1720 for 20 hours. We found that the class I and II HDACi TSA and SAHA and the class II HDACi MC1568 significantly decreased IL-β-induced MMP-9 gene and pro-MMP-9 expression in primary amnion cells. There was, however, no effect of the class I HDACi MS-275 on IL-β-induced MMP-9 expression. On the other hand, inhibition of class III HDAC SIRT1 using siRNA significantly augmented IL-1β-induced MMP-9, and SIRT1 activation using resveratrol and SRT1720 inhibited IL-1β-induced MMP-9 expression. In summary, class I to III HDACs differentially regulate inflammation-induced MMP-9 expression in primary amnion cells.

FOXM1 is lower in human fetal membranes after spontaneous preterm labour and delivery

Spontaneous preterm birth is usually associated with infection, inflammation or both. Forkhead box (FOX) M1 (FOXM1), a member of the FOX family of transcription factors, has been associated with inflammation. The aim of this study was to determine whether FOXM1 regulates the expression and release of pro-labour mediators in human gestational tissues. FOXM1 mRNA and protein expression were determined in fetal membranes from women at (1) preterm no labour: Caesarean section with no labour and (2) preterm labour: after spontaneous labour and delivery. Primary amnion cells were utilised to investigate the effect of small interfering RNA (siRNA)-mediated gene silencing of FOXM1 on pro-labour mediators. Spontaneous preterm labour decreased FOXM1 gene and nuclear protein expression. FOXM1 silencing in primary amnion cells increased interleukin (IL)-1β-induced pro-inflammatory cytokines (IL-6 and IL-8 mRNA expression and secretion), cyclooxygenase (COX)-2 expression and subsequent prostaglandin (PG)E2 and PGF2α release as well as gene expression and secretion of the matrix-degrading enzyme matrix metalloproteinase 9 (MMP-9). In conclusion, spontaneous preterm labour is associated with decreased FOXM1 expression in fetal membranes.

Effect of supracervical apposition and spontaneous labour on apoptosis and matrix metalloproteinases in human fetal membranes

Background. Apoptosis and matrix metalloproteinase (MMP-9) are capable of hydrolysing components of the extracellular matrix and weakening the fetal membranes which leads to eventual rupture, a key process of human parturition. The aim of this study was to determine the effect of supracervical apposition and spontaneous labour on apoptosis and MMP-9 in human fetal membranes at term. Methods. Fetal membranes were obtained from term non-labouring supracervical site (SCS) and compared to (i) a paired distal site (DS) or (ii) site of rupture (SOR) after spontaneous labour onset. Results. The expression of the proapoptotic markers Bax, Smac, Fas, FasL, caspase-3, and PARP, was significantly higher in the non-labouring SCS chorion compared to paired DS. Bax, Smac, FasL, caspase-3, and PARP staining was higher in the non-labouring SCS fetal membranes than that in the post-labour SOR. MMP-9 expression and activity were higher in the post-labour SOR fetal membranes compared to non-labouring SCS fetal membranes. Conclusion. Components of the apoptotic signalling pathways and MMP-9 may play a role in rupture and labour. Non-labouring SCS fetal membranes display altered morphology and altered apoptotic biochemical characteristics in preparation for labour, while the laboured SOR displays unique MMP characteristics.

The chorion layer of fetal membranes is prematurely destroyed in women with preterm premature rupture of the membranes

Preterm premature rupture of the membranes (PPROM) is an important etiology of preterm birth and source of significant neonatal morbidity. We propose that PPROM occurs in the setting of long-standing altered tissue remodeling, which creates a vulnerable environment for the fetal membranes and pregnancy. We tested the hypothesis that PPROM is the result of tissue remodeling in the fetal membranes, specifically the chorion, and this weakening of the chorion compromises the protection provided to the amnion. The purpose of this study was to quantify thickness and apoptosis in the choriodecidua of fetal membranes in patients with PPROM, preterm labor (PTL), preterm no labor (PTNL), and women with term labor (TERM). We conducted a retrospective evaluation of fetal membrane samples from 86 placentas. Immunohistochemistry was performed using a cytokeratin antibody, and mean chorion cellular thickness was compared between each clinical group. To evaluate chorion apoptosis, fetal membranes from patients with PPROM, PTL, and TERM were stained with the M30 antibody, and the degree of cellular apoptosis was determined. Statistical analysis was performed using analysis of variance with corrections for multiple comparisons. The chorion cellular layer was thinner in patients with PPROM compared to patients with PTNL and TERM (62, 140, and 169 µm, respectively, P < .0001), though not significantly different from PTL (95 µm, P > .05). The percentage of apoptotic cells within the chorion among the patients with PPROM was greater compared to PTL and TERM (24.2%, 13.1%, and 8.4%, respectively, P < .001). The chorion cellular layer is thinner and demonstrates increased apoptosis in PPROM compared to patients with PTL, PTNL, and TERM, suggesting differential remodeling between clinical phenotypes.

The role of apoptosis in preterm premature rupture of the human fetal membranes

PURPOSE

The present study was designed to examine apoptotic cell death via the caspase-dependent pathway in human fetal membranes.

METHODS

Amniotic membrane samples were collected from three groups of women: group 1, women with preterm premature rupture of fetal membranes (PPROM) after cesarean delivery (n = 10), group 2, women with preterm labor (PTL) with intact membranes after cesarean delivery (n = 9) and group 3, women with term labor and vaginal delivery after an uncomplicated pregnancy (controls) (n = 11).

RESULTS

Active caspase-3 immunopositivity (ACPI) of the PPROM group was significantly higher than that of the control group (p < 0.05). ACPI was higher in the PTL with intact membranes group as compared to the control group; however, it did not reach statistical significance (p > 0.05).

CONCLUSION

Active caspase-3 positivity is increased in the fetal membranes of those women with PPROM.

Gene expression patterns of the Bcl-2 and Bax genes in preterm birth

OBJECTIVE

The apoptotic genes Bax and Bcl-2 are both involved in the pathogenesis of preterm delivery in conjunction with additional factors. We characterized gene expression patterns of these apoptotic regulatory genes as well as relevant environmental factors.

DESIGN

A gene expression study with evaluation of clinical data.

SETTING

Semmelweis University, Budapest, Hungary.

SAMPLE

Human placental samples from 104 preterm and 140 full-term pregnancies.

METHODS

Gene tests were performed using real-time PCR to assess gene expression patterns of Bax and Bcl-2 in human placental samples. Clinical data were collected from our computerized database.

MAIN OUTCOME MEASURES

Apoptotic gene expression pattern and clinical information against the background of preterm delivery.

RESULTS

In placental samples from preterm delivery pregnancies, expression of the Bcl-2 gene was unchanged, whereas the Bax gene was overexpressed. Placental gene expression of Bax in preterm delivery was dependent on gestational age with gestational weeks 28-32 and 32-36 associated with overexpression, and no overexpression in gestational weeks 24-28. Preterm delivery began with premature rupture of membranes in 70.2% and spontaneous uterine activity in 29.8%.

CONCLUSIONS

The Bax gene was overexpressed in preterm delivery, whereas expression of the Bcl-2 gene remained unchanged. After the 28(th) gestational week, apoptosis appears to be a key factor in the pathogenesis of preterm delivery.

Extracellular matrix dynamics and fetal membrane rupture

The extracellular matrix (ECM) plays an important role in determining cell and organ function: (1) it is an organizing substrate that provides tissue tensile strength; (2) it anchors cells and influences cell morphology and function via interaction with cell surface receptors; and (3) it is a reservoir for growth factors. Alterations in the content and the composition of the ECM determine its physical and biological properties, including strength and susceptibility to degradation. The ECM components themselves also harbor cryptic matrikines, which when exposed by conformational change or proteolysis have potent effects on cell function, including stimulating the production of cytokines and matrix metalloproteinases (MMPs). Collectively, these properties of the ECM reflect a dynamic tissue component that influences both tissue form and function. This review illustrates how defects in ECM synthesis and metabolism and the physiological process of ECM turnover contribute to changes in the fetal membranes that precede normal parturition and contribute to the pathological events leading to preterm premature rupture of membranes (PPROM).