[Biochemistry of fetal membranes rupture]

Frontiers in the Etiology and Treatment of Preterm Premature Rupture of Membrane: From Molecular Mechanisms to Innovative Therapeutic Strategies

Preterm premature rupture of membranes (pPROM) poses a significant threat to fetal viability and increases the risk for newborn morbidities. The perinatal period of preterm infants affected by pPROM is often characterized by higher rates of mortality and morbidity, with associated risks of cerebral palsy, developmental delays, compromised immune function, respiratory diseases, and sensory impairments. pPROM is believed to result from a variety of causes, including but not limited to microbially induced infections, stretching of fetal membranes, oxidative stress, inflammatory responses, and age-related changes in the fetal-placental interface. Maternal stress, nutritional deficiencies, and medically induced procedures such as fetoscopy are also considered potential contributing factors to pPROM. This comprehensive review explores the potential etiologies leading to pPROM, delves into the intricate molecular mechanisms through which these etiologies cause membrane ruptures, and provides a concise overview of diagnostic and treatment approaches for pPROM. Based on available therapeutic options, this review proposes and explores the possibilities of utilizing a novel composite hydrogel composed of amniotic membrane particles for repairing ruptured fetal membranes, thereby holding promise for its clinical application.

Shared developmental pathways of the placenta and fetal heart

Congenital heart defects (CHD) remain the most common class of birth defect worldwide, affecting 1 in every 110 live births. A host of clinical and morphological indicators of placental dysfunction are observed in pregnancies complicated by fetal CHD and, with the recent emergence of single-cell sequencing capabilities, the molecular and physiological associations between the embryonic heart and developing placenta are increasingly evident. In CHD pregnancies, a hostile intrauterine environment may negatively influence and alter fetal development. Placental maldevelopment and dysfunction creates this hostile in-utero environment and may manifest in the development of various subtypes of CHD, with downstream perfusion and flow-related alterations leading to yet further disruption in placental structure and function. The adverse in-utero environment of CHD-complicated pregnancies is well studied, however the specific etiological role that the placenta plays in CHD development remains unclear. Many mouse and rat models have been used to characterize the relationship between CHD and placental dysfunction, but these paradigms present substantial limitations in the assessment of both the heart and placenta. Improvements in non-invasive placental assessment can mitigate these limitations and drive human-specific investigation in relation to fetal and placental development. Here, we review the clinical, structural, and molecular relationships between CHD and placental dysfunction, the CHD subtype-dependence of these changes, and the future of Placenta-Heart axis modeling and investigation.

Characterization of RAGE and CK2 Expressions in Human Fetal Membranes

At the feto-maternal interface, fetal membranes (FM) play a crucial role throughout pregnancy. FM rupture at term implicates different sterile inflammation mechanisms including pathways activated by the transmembrane glycoprotein receptor for advanced glycation end-products (RAGE) belonging to the immunoglobulin superfamily. As the protein kinase CK2 is also implicated in the inflammation process, we aimed to characterize the expressions of RAGE and the protein kinase CK2 as a candidate regulator of RAGE expression. The amnion and choriodecidua were collected from FM explants and/or primary amniotic epithelial cells throughout pregnancy and at term in spontaneous labor (TIL) or term without labor (TNL). The mRNA and protein expressions of RAGE and the CK2α, CK2α', and CK2β subunits were investigated using reverse transcription quantitative polymerase chain reaction and Western blot assays. Their cellular localizations were determined with microscopic analyses, and the CK2 activity level was measured. RAGE and the CK2α, CK2α', and CK2β subunits were expressed in both FM layers throughout pregnancy. At term, RAGE was overexpressed in the amnion from the TNL samples, whereas the CK2 subunits were expressed at the same level in the different groups (amnion/choriodecidua/amniocytes, TIL/TNL), without modification of the CK2 activity level and immunolocalization. This work paves the way for future experiments regarding the regulation of RAGE expression by CK2 phosphorylation.

Potential Therapeutic Effects of Human Amniotic Epithelial Cells on Gynecological Disorders Leading to Infertility or Abortion

The induction of feto-maternal tolerance, fetal non-immunogenicity, and the regulation of mother's immune system are essential variables in a successful pregnancy. Fetal membranes have been used as a source of stem cells and biological components in recent decades. Human amniotic epithelial cells (hAEC) have stem/progenitor characteristics like those found in the amniotic membrane. Based on their immunomodulatory capabilities, recent studies have focused on the experimental and therapeutic applications of hAECs in allograft transplantation, autoimmune disorders, and gynecological problems such as recurrent spontaneous abortion (RSA), recurrent implantation failure (RIF), and premature ovarian failure (POF). This review discusses some of the immunomodulatory features and therapeutic potential of hAECs in preventing infertility, miscarriage, and implantation failure by controlling the maternal immune system.

Dysregulation of the Amniotic PPARγ Pathway by Phthalates: Modulation of the Anti-Inflammatory Activity of PPARγ in Human Fetal Membranes

Phthalates are reprotoxic pollutants that are omnipresent in the environment. Detectable in amniotic fluid, these compounds (with the most concentrated being mono-2-ethylhexyl phthalate (MEHP)) are in direct contact with fetal membranes (FMs). They can lead to the premature rupture of FMs by deregulating cellular and molecular pathways, such as, for example, the nuclear transcription factor peroxysome proliferator-activated receptor gamma (PPARγ) pathway. The objective was to study the impact of MEHP on the PPARγ pathway in FMs using amnion and choriodecidua across the three trimesters of pregnancy and the amniotic epithelial AV3 cell model by analyzing (i) PPARγ expression (mRNA and proteins) using RT-qPCR and Western blot assays; (ii) cytotoxicity and cell viability following MEHP treatment by lactate dehydrogenase (LDH) measurement and using Cell-counting Kit 8; and (iii) modulation by MEHP of PPARγ transcriptional activity (using a reporter gene assay) and PPARγ anti-inflammatory properties (by measuring IL6 and IL8 levels). PPARγ is expressed in the human amnion and choriodecidua during the three trimesters of pregnancy and in amniotic cells. In the AV3 cell line, MEHP is not cytotoxic and does not reduce cell viability, but it reduces PPARγ activity, here induced by a classical agonist without influencing its expression. MEHP also reduces PPARγ’s anti-inflammatory properties. In conclusion, PPARγ signaling is dysregulated by MEHP; this paves the way for future explorations to highlight the hypothesis of phthalates as an amniotic PPARγ disruptor that can explain the premature rupture of FMs.

Physiological TLR4 regulation in human fetal membranes as an explicative mechanism of a pathological preterm case

The integrity of human fetal membranes is crucial for harmonious fetal development throughout pregnancy. Their premature rupture is often the consequence of a physiological phenomenon that has been exacerbated. Beyond all the implied biological processes, inflammation is of primary importance and is qualified as ‘sterile’ at the end of pregnancy. In this study, complementary methylomic and transcriptomic strategies on amnion and choriodecidua explants obtained from the altered (cervix zone) and intact fetal membranes at term and before labour were used. By cross-analysing genome-wide studies strengthened by in vitro experiments, we deciphered how the expression of toll-like receptor 4 (TLR4), an actor in pathological fetal membrane rupture, is controlled. Indeed, it is differentially regulated in the altered zone and between both layers by a dual mechanism: (1) the methylation of TLR4 and miRNA promoters and (2) targeting by miRNA (let-7a-2 and miR-125b-1) acting on the 3’-UTR of TLR4. Consequently, this study demonstrates that fine regulation of TLR4 is required for sterile inflammation establishment at the end of pregnancy and that it may be dysregulated in the pathological premature rupture of membranes.

Effects of histone H4 hyperacetylation on inhibiting MMP2 and MMP9 in human amniotic epithelial cells and in premature rupture of fetal membranes

Histone modification is closely associated with several diseases. The aim of the current study was to investigate the associations among histone acetylation, matrix metalloproteinases (MMPs) and premature rupture of membranes (PROM) during pregnancy. A total of 180 puerperants were divided into three groups: i) Preterm-PROM (PPROM), ii) term-PROM (TPROM) and iii) full-term labor (FTL). Enzyme-linked immunosorbent assay (ELISA) kits and western blotting were used to determine the protein concentrations of MMP2, MMP9, histone deacetylase (HDAC)1, HDAC2 and HDAC6, and the protein levels of histone H4 lysine (H4K)5 and H4K8 acetylation, respectively, in three types of fetal membranes. Additionally, human amniotic epithelial cells were used to determine the effects of the HDAC inhibitors droxinostat and chidamide on cell viability, histone acetylation and the levels of MMP2, MMP9, HDAC1, HDAC2 and HDAC6 in vitro, using the Cell Counting Kit-8 assay, western blotting and ELISA, respectively. Furthermore, the effects of droxinostat and chidamide on the invasion and migration abilities of human amniotic epithelial cells were investigated using transwell assays. In fetal membranes, the activities of MMP2 and MMP9 increased in PPROM, but decreased in TPROM. Further, the expression of HDAC1 was decreased and histone hyperacetylation was increased in both PPROM and TRPOM. In vitro experiments revealed that 5 µM droxinostat and 0.5 µM chidamide selectively decreased the level of HDAC and induced acetylation of H4K5 and H4K8. Additionally, the aforementioned HDAC inhibitors reduced human amniotic epithelial cell viability, invasion and migration, and decreased the expression levels of MMP2 and MMP9. The current study revealed a high expression level of MMP2 and MMP9 in PPROM compared with TPROM and FL tissue, which was in accordance with previously published studies. Furthermore, the in vitro tests performed in the current study revealed the effect of histone H4 hyperacetylation on inhibiting MMP2 and MMP9 levels in vitro was similar to that observed in TPROM. The results obtained in the current study may be used as a theoretical guide for clinical treatment of premature rupture of membranes.

The Role of Epithelial to Mesenchymal Transition in Human Amniotic Membrane Rupture

CONTEXT

Biochemical weakening of the amnion is a major factor preceding preterm premature rupture of membranes (PPROMs), leading to preterm birth. Activation of matrix metalloproteinases (MMPs) is known to play a key role in collagen degradation of the amnion; however, epithelial to mesenchymal transition (EMT) that is also induced by MMP activation has not been investigated as a mechanism for amnion weakening.

OBJECTIVE

To measure amniotic EMT associated with vaginal delivery (VD) compared with unlabored cesarean sections (CSs), and to assess changes in amniotic mechanical strength with pharmacologic inhibitors and inducers of EMT, thus testing the hypothesis that EMT is a key biochemical event that promotes amniotic rupture.

FINDINGS

(1) Amnions taken from VD contained a significantly increased number of mesenchymal cells relative to epithelial cells compared with unlabored CS by fluorescence-activated cell sorting analysis (60% vs 10%); (2) tumor necrosis factor (TNF)-α stimulation of amniotic epithelial cells increased expression of the mesenchymal marker vimentin after 2 days; (3) EMT inhibitor, etodolac, significantly increased the time and mechanical pressure required to rupture the amnion; and (4) TNF-α and another pharmacologic EMT inducer, ethacridine, decreased the time and mechanical pressure required for amnion rupture, further confirming that the mesenchymal phenotype significantly weakens the amnion.

CONCLUSIONS

This work demonstrated amniotic cell EMT was associated with labor and EMT decreased the tensile strength of the amnion. These findings suggest a role for EMT in the pathophysiology of PPROM and may provide a basis for development of therapies to prevent preterm labor.

All-trans retinoic acid promotes wound healing of primary amniocytes through the induction of LOXL4, a member of the lysyl oxidase family

Thirty percent of preterm births directly result from preterm premature rupture of fetal membranes (PPROM). Clinical management currently proposes using a collagen plug to mechanically stop loss of amniotic fluid. Vitamin A and its active metabolite (retinoic acid) have well-known pro-healing properties and could thus make good candidates as a proposable adjuvant to this mechanical approach. Here we investigate the molecular mechanisms involved in the pro-healing properties of all-trans retinoic acid (atRA) in fetal membranes via an approach using an in vitro primary amniocyte wound model and transcriptomics. The results demonstrate that atRA promotes migration in primary amniocytes, improving wound healing in vitro by up to 90%. This effect is mediated by the induction of LOXL4, which plays a crucial role in the dynamics of the extracellular matrix by regulating collagen reticulation. This new insight into how atRA exerts its pro-healing properties prompts us to propose using atRA as a candidate strategy to help prevent future PPROM.

Meta-analysis of studies on biochemical marker tests for the diagnosis of premature rupture of membranes: comparison of performance indexes

Background

Premature rupture of the membranes (PROM) is most commonly diagnosed using physical examination; however, accurate decision making in ambiguous cases is a major challenge in current obstetric practice. As this may influence a woman’s subsequent management, a number of tests designed to assist with confirming a diagnosis of PROM are commercially available. This study sought to evaluate the published data for the accuracy of two amniotic fluid-specific biomarker tests for PROM: insulin-like growth factor binding protein-1 (IGFBP-1 – Actim® PROM) and placental alpha microglobulin-1 (PAMG-1 – AmniSure®).

Methods

Main analysis included all PubMed referenced studies related to Actim® PROM and AmniSure® with available data to extract performance rates. To compare accuracy, a comparison of pooled indexes of both rapid tests was performed. Studies in which both tests were used in the same clinical population were also analysed. Membrane status, whether it was known or a suspected rupture, and inclusion or not of women with bleeding, were considered.

Results

All the available studies published in PubMed up to April 2013 were reviewed. Data were retrieved from 17 studies; 10 for Actim® PROM (n = 1066), four for AmniSure® (n = 1081) and three studies in which both biomarker tests were compared directly. The pooled analysis found that the specificity and positive predictive value were significantly higher for AmniSure® compared with Actim® PROM. However, when 762 and 1385 women with known or suspected rupture of membranes, respectively, were evaluated, AmniSure® only remained significantly superior in the latter group. Furthermore, when the two tests were compared directly in the same study no statistically significant differences were observed. Remarkably, women with a history or evidence of bleeding were excluded in all four studies for AmniSure®, in two Actim® PROM studies and in two of the three studies reporting on both tests.

Conclusions

No differences were observed in the performance of the two tests in studies where they were used under the same clinical conditions or in women with known membrane status. Although AmniSure® performed better in suspected cases of PROM, this may need further analysis as exclusion of bleeding may not be representative of the real clinical presentation of women with suspected PROM.

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.

Acephaly: further evidence for disruption but not for amniotic bands

Complete absence of the fetal head in singleton pregnancies is a very rare defect; to our knowledge there are only 7 reported cases. Decapitation by amniotic bands has been considered as the most probable cause. However, in none of the described cases except one were amniotic bands, constriction rings, or other related findings observed, raising the possibility that mechanisms other than amputation by amniotic bands are involved. We present a further case of acephaly and discuss the role of amniotic bands and alternative mechanisms of decapitation and a possible sequence of events leading to acephaly.