CX3CL1/Fractalkine as a biomarker for early pregnancy prediction of preterm premature rupture of membranes

OBJECTIVES

The objective of our study was to evaluate serum CX3CL1/Fractalkine, a monocyte/macrophage chemoattractant expressed in cytotrophoblasts and decidual cells, as a predictive biomarker for the occurrence of preterm premature rupture of membranes (PPROM).

METHODS

A case-control study of 438 pregnancies including 82 PPROM cases and 64 preterm labor with intact membranes cases with blood samples collected at first trimester, second trimester and delivery was conducted. The predictive ability of CX3CL1 and maternal risk factors for the occurrence of PPROM was assessed by receiver operating characteristic curve analysis. A second, independent cohort was prospectively constituted to confirm the case-control study results.

RESULTS

First trimester CX3CL1 was significantly increased in PPROM cases when compared to matched controls. Multivariate regression analysis highlighted a significant difference for CX3CL1 measured during the first trimester (p<0.001). Alone, CX3CL1 predicts PPROM with a 90 % sensitivity and a specificity around 40 %. The area under the receiver operating characteristic curve for PPROM prediction were 0.64 (95% confidence interval: 0.57-0.71) for first trimester CX3CL1, and 0.61 (95% confidence interval: 0.54-0.68) for maternal risk factors (body mass index<18.5 kg/m2, nulliparity, tobacco use and the absence of high school diploma). The combination of CX3CL1 and maternal risk factors significantly improved the area under the curve: 0.72 (95% confidence interval: 0.66-0.79) (p<0.001). The results were confirmed on a second independent cohort.

CONCLUSIONS

CX3CL1 is a promising blood biomarker in the early (first trimester) prediction of PPROM.

DeepMPTB: a vaginal microbiome-based deep neural network as artificial intelligence strategy for efficient preterm birth prediction

In recent decades, preterm birth (PTB) has become a significant research focus in the healthcare field, as it is a leading cause of neonatal mortality worldwide. Using five independent study cohorts including 1290 vaginal samples from 561 pregnant women who delivered at term (n = 1029) or prematurely (n = 261), we analysed vaginal metagenomics data for precise microbiome structure characterization. Then, a deep neural network (DNN) was trained to predict term birth (TB) and PTB with an accuracy of 84.10% and an area under the receiver operating characteristic curve (AUROC) of 0.875 ± 0.11. During a benchmarking process, we demonstrated that our DL model outperformed seven currently used machine learning algorithms. Finally, our results indicate that overall diversity of the vaginal microbiota should be taken in account to predict PTB and not specific species. This artificial-intelligence based strategy should be highly helpful for clinicians in predicting preterm birth risk, allowing personalized assistance to address various health issues. DeepMPTB is open source and free for academic use. It is licensed under a GNU Affero General Public License 3.0 and is available at https://deepmptb.streamlit.app/ . Source code is available at https://github.com/oschakoory/DeepMPTB and can be easily installed using Docker ( https://www.docker.com/ ).

Inflammation of Dry Eye Syndrome: A Cellular Study of the Epithelial and Macrophagic Involvement of NFAT5 and RAGE

Dry eye inflammation is a key step in a vicious circle and needs to be better understood in order to break it. The goals of this work were to, first, characterize alarmins and cytokines released by ocular surface cells in the hyperosmolar context and, second, study the role of NFAT5 in this process. Finally, we studied the potential action of these alarmins in ocular surface epithelial cells and macrophages via RAGE pathways. HCE and WKD cell lines were cultured in a NaCl-hyperosmolar medium and the expression of alarmins (S100A4, S100A8, S100A9, and HMGB1), cytokines (IL6, IL8, TNFα, and MCP1), and NFAT5 were assessed using RT-qPCR, ELISA and multiplex, Western blot, immunofluorescence, and luciferase assays. In selected experiments, an inhibitor of RAGE (RAP) or NFAT5 siRNAs were added before the hyperosmolar stimulations. HCE and WKD cells or macrophages were treated with recombinant proteins of alarmins (with or without RAP) and analyzed for cytokine expression and chemotaxis, respectively. Hyperosmolarity induced epithelial cell inflammation depending on cell type. NFAT5, but not RAGE or alarmins, participated in triggering epithelial inflammation. Furthermore, the release of alarmins induced macrophage migration through RAGE. These in vitro results suggest that NFAT5 and RAGE have a role in dry eye inflammation.

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.

Spatial Distribution and Physicochemical Properties of Respirable Volcanic Ash From the 16-17 August 2006 Tungurahua Eruption (Ecuador), and Alveolar Epithelium Response In-Vitro

Tungurahua volcano (Ecuador) intermittently emitted ash between 1999 and 2016, enduringly affecting the surrounding rural area and its population, but its health impact remains poorly documented. We aim to assess the respiratory health hazard posed by the 16-17 August 2006 most intense eruptive phase of Tungurahua. We mapped the spatial distribution of the health-relevant ash size fractions produced by the eruption in the area impacted by ash fallout. We quantified the mineralogy, composition, surface texture, and morphology of a respirable ash sample isolated by aerodynamic separation. We then assessed the cytotoxicity and pro-inflammatory potential of this respirable ash toward lung tissues in-vitro using A549 alveolar epithelial cells, by electron microscopy and biochemical assays. The eruption produced a high amount of inhalable and respirable ash (12.0-0.04 kg/m² of sub-10 μm and 5.3-0.02 kg/m² of sub-4 μm ash deposited). Their abundance and proportion vary greatly across the deposit within the first 20 km from the volcano. The respirable ash is characteristic of an andesitic magma and no crystalline silica is detected. Morphological features and surface textures are complex and highly variable, with few fibers observed. In-vitro experiments show that respirable volcanic ash is internalized by A549 cells and processed in the endosomal pathway, causing little cell damage, but resulting in changes in cell morphology and membrane texture. The ash triggers a weak pro-inflammatory response. These data provide the first understanding of the respirable ash hazard near Tungurahua and the extent to which it varies spatially in a fallout deposit.

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.

Oxidative and antioxidative stress markers in dry eye disease: A systematic review and meta-analysis

PURPOSE

To conduct a systematic review and meta-analysis on the levels of oxidative stress markers and antioxidants in dry eye disease (DED) compared with healthy subject.

METHOD

The PubMed, Cochrane Library, Embase, Science Direct and Google Scholar databases were searched on 10 January 2021 for studies reporting oxidative and antioxidative stress markers in DED and healthy controls. Main meta-analysis was stratified by type of biomarkers, type of samples (tears, conjunctival cells or biopsies), Sjögren's syndrome (SS) (patients with or without SS) and by geographical zones (Asia or Europe).

RESULTS

We included nine articles, for a total of 333 patients (628 eye samples) with DED and 165 healthy controls (451 eye samples). There is an overall increase in oxidative stress markers in DED compared with healthy controls (standard mean deviation = 2.39, 95% confidence interval 1.85-2.94), with a significant increase in lipid peroxide (1.90, 0.69-3.11), myeloperoxidase (2.17, 1.06-3.28), nitric oxide synthase 3 (2.52, 0.95-4.08), xanthine oxidase/oxidoreductase (2.41, 1.40-5.43), 4-hydroxy-2-nonenal (4HNE) (4.75, 1.67-7.84), malondialdehyde (3.00, 2.55-3.45) and reactive oxygen species (1.31, 0.94-1.68). Oxidative stress markers were higher in tears, conjunctival cells and conjunctival biopsies of DED than controls. Even if small number of studies were included for antioxidants, catalase seemed to be decreased in DED compared with healthy controls (-2.17, -3.00 to -1.34), with an increase of antioxidants in tears of DED patients without SS (1.13, 0.76-1.49).

CONCLUSION

Oxidative stress markers, and probably antioxidants, were dysregulated in DED, establishing a local oxidative environment in tears, conjunctival cells and tissues.

Dysregulation of Receptor for Advanced Glycation End Products (RAGE) Expression as a Biomarker of Keratoconus

BACKGROUND

Because of the implications of Receptor for Advanced Glycation End Products (RAGE) in keratoconus (KC), we describe a differential expression of RAGE transcripts and proteins in corneal tissues and tears of KC and healthy patients.

METHODS

Using a case-controlled study, corneal epitheliums and tears of KC and healthy subjects were obtained during corneal collagen cross-linking and photorefractive keratectomy (PKR) and during usual consultations. Quantitative reverse transcription (RT-qPCR) and Western-Blot were performed to analyze RAGE transcripts and proteins' expression in corneal tissues and tears.

RESULTS

One hundred and six patients were included in this study. The characteristics of the patients were as follows: 56 KC (25 corneal epithelium and 31 tears) and 50 control subjects (25 corneal epithelium and 25 tears). Transcripts of RAGE, HMGB1, and S100 family ligands were quantified by RT-qPCR, identifying a significantly higher expression of RAGE and HMGB1 in the healthy group than in the KC group (p = 0.03 and 0.04, respectively). Western Blot showed a significantly higher fl-RAGE expression in KC corneal epithelium than control (p < 0.001) and lower s-RAGE expression in KC tears than control (p = 0.04).

CONCLUSIONS

Linked with the inflammatory process occurring in KC pathophysiology, we propose for the first time that the RAGE expression (total and truncated forms of receptor and ligands) in KC corneal tissues and tear samples provides viable biomarkers.

Pathophysiological Implication of Pattern Recognition Receptors in Fetal Membranes Rupture: RAGE and NLRP Inflammasome

Preterm prelabor ruptures of fetal membranes (pPROM) are a pregnancy complication responsible for 30% of all preterm births. This pathology currently appears more as a consequence of early and uncontrolled process runaway activation, which is usually implicated in the physiologic rupture at term: inflammation. This phenomenon can be septic but also sterile. In this latter case, the inflammation depends on some specific molecules called “alarmins” or “damage-associated molecular patterns” (DAMPs) that are recognized by pattern recognition receptors (PRRs), leading to a microbial-free inflammatory response. Recent data clarify how this activation works and which receptor translates this inflammatory signaling into fetal membranes (FM) to manage a successful rupture after 37 weeks of gestation. In this context, this review focused on two PRRs: the receptor for advanced glycation end-products (RAGE) and the NLRP7 inflammasome.

Halogenated Agent Delivery in Porcine Model of Acute Respiratory Distress Syndrome via an Intensive Care Unit Type Device

Acute respiratory distress syndrome (ARDS) is a common cause of hypoxemic respiratory failure and death in critically ill patients, and there is an urgent need to find effective therapies. Preclinical studies have shown that inhaled halogenated agents may have beneficial effects in animal models of ARDS. The development of new devices to administer halogenated agents using modern intensive care unit (ICU) ventilators has significantly simplified the dispensing of halogenated agents to ICU patients. Because previous experimental and clinical research suggested potential benefits of halogenated volatiles, such as sevoflurane or isoflurane, for lung alveolar epithelial injury and inflammation, two pathophysiologic landmarks of diffuse alveolar damage during ARDS, we designed an animal model to understand the mechanisms of the effects of halogenated agents on lung injury and repair. After general anesthesia, tracheal intubation, and the initiation of mechanical ventilation, ARDS was induced in piglets via the intratracheal instillation of hydrochloric acid. Then, the piglets were sedated with inhaled sevoflurane or isoflurane using an ICU-type device, and the animals were ventilated with lung-protective mechanical ventilation during a 4 h period. During the study period, blood and alveolar samples were collected to evaluate arterial oxygenation, the permeability of the alveolar-capillary membrane, alveolar fluid clearance, and lung inflammation. Mechanical ventilation parameters were also collected throughout the experiment. Although this model induced a marked decrease in arterial oxygenation with altered alveolar-capillary permeability, it is reproducible and is characterized by a rapid onset, good stability over time, and no fatal complications. We have developed a piglet model of acid aspiration that reproduces most of the physiological, biological, and pathological features of clinical ARDS, and it will be helpful to further our understanding of the potential lung-protective effects of halogenated agents delivered through devices used for inhaled ICU sedation.

Human Amnion Epithelial Cells (AECs) Respond to the FSL-1 Lipopeptide by Engaging the NLRP7 Inflammasome

Context and Objectives: Inflammation is the leading mechanism involved in both physiological and pathological rupture of fetal membranes. Our aim was to obtain a better characterization of the inflammasome-dependent inflammation processes in these tissues, with a particular focus on the nucleotide-binding oligomerization domain (NOD)–like receptor, pyrin domain containing protein 7 (NLRP7) inflammasome.

Methods: The presence of NLRP7 inflammasome actors [NLRP7, apoptosis-associated speck–like protein containing a CARD domain (ASC), and caspase-1] was confirmed by reverse transcriptase–polymerase chain reaction (RT-PCR) in human amnion and choriodecidua at the three trimesters and at term. The protein concentrations were then determined by enzyme-linked immunosorbent assay in term tissues, with or without labor. The presence of Mycoplasma salivarium and Mycoplasma fermentans in human fetal membranes was investigated using a PCR approach. Human amnion epithelial cells (AECs) were treated for 4 or 20 h with fibroblast-stimulating lipopeptide-1 (FSL-1), a M. salivarium–derived ligand. Transcripts and proteins quantity was then measured by RT–quantitative PCR and Western blotting, respectively. NLRP7 and ASC colocalization was confirmed by immunofluorescence. Western blots allowed analysis of pro–caspase-1 and gasdermin D cleavage.

Results: NLRP7, ASC, and caspase-1 transcripts were expressed in both sheets of human fetal membranes during all pregnancy stages, but only ASC protein expression was increased with labor. In addition, M. salivarium and M. fermentans were detected for the first time in human fetal membranes. NLRP7 and caspase-1 transcripts, as well as NLRP7, ASC, and pro–caspase-1 protein levels, were increased in FSL-1–treated AECs. The NLRP7 inflammasome assembled around the nucleus, and pro–caspase-1 and gasdermin D were cleaved into their mature forms after FSL-1 stimulation.

Conclusion: Two new mycoplasmas, M. salivarium and M. fermentans, were identified in human fetal membranes, and a lipopeptide derived from M. salivarium was found to induce NLRP7 inflammasome formation in AECs.

Advanced Glycation End Products and Receptor (RAGE) Promote Wound Healing of Human Corneal Epithelial Cells

Purpose

We used a human corneal epithelial cell (HCE) line to determine the involvement of the advanced glycation end products (AGEs) / receptor for AGEs (RAGE) couple in corneal epithelium wound healing.

Methods

After wounding, HCE cells were exposed to two major RAGE ligands (HMGB1 and AGEs), and wound healing was evaluated using the in vitro scratch assay. Following wound healing, the HCE cells were used to study the influence of the RAGE ligands on HCE proliferation, invasion, and migration. Activation of the nuclear factor (NF)-κB signaling pathway by the AGEs/RAGE couple was tested using a luciferase reporter assay. Functional transcriptional regulation by this pathway was confirmed by quantification of expression of the connexin 43 target gene. For each experiment, specific RAGE involvement was confirmed by small interfering RNA treatments.

Results

AGEs treatment at a dose of 100 µg/mL significantly improved the wound healing process in a RAGE-dependent manner by promoting cell migration, whereas HMGB1 had no effect. No significant influence of the AGEs/RAGE couple was observed on cell proliferation and invasion. However, this treatment induced an early activation of the NF-κB pathway and positively regulated the expression of the target gene, connexin 43, at both the mRNA and protein levels.

Conclusions

Our results demonstrate that the RAGE pathway is activated by AGEs treatment and is involved in the promotion of corneal epithelial wound healing. This positive action is observed only during the early stages of wound healing, as illustrated by the quick activation of the NF-κB pathway and induction of connexin 43 expression.

Occurrence of a RAGE-Mediated Inflammatory Response in Human Fetal Membranes

Context:

Sterile inflammation has been shown to play a key role in the rupture of the fetal membranes (FMs). Moreover, an early and exacerbated runaway inflammation can evolve into a preterm premature rupture of membranes and lead to potential preterm birth. In this context, we investigated the receptor for advanced glycation end products (RAGE), an axis implied in physiological sterile inflammation, in conjunction with two major ligands: AGEs and High-Mobility Group Box 1 (HMGB1). Our first objective was to determine the spatiotemporal expression profiles of the different actors of the RAGE-signaling axis in human FMs, including its intracellular adaptors Diaphanous-1 and Myd88. Our second goal was to evaluate the functionality of RAGE signaling in terms of FMs inflammation.

Methods

The presence of the actors (RAGE, HMGB1, Myd88, and Diaphanous-1) at the mRNA level was investigated by reverse transcription quantitative polymerase chain reaction (RT-qPCR) in the human amnion and choriodecidua at the three trimesters and at term. Measurements were conducted at two distinct zones: the zone of intact morphology (ZIM) and the zone of altered morphology (ZAM). Then, proteins were quantified using Western blot analysis, and their localization was evaluated by immunofluorescence in term tissues. In addition, pro-inflammatory cytokine secretion was quantified using a Multiplex assay after the treatment of amnion and choriodecidua explants with two RAGE ligands (AGEs and HMGB1) in the absence or presence of a RAGE inhibitor (SAGEs).

Results

The FMs expressed the RAGE-signaling actors throughout pregnancy. At term, RNA and protein overexpression of the RAGE, HMGB1, and Diaphanous-1 were found in the amnion when compared to the choriodecidua, and the RAGE was overexpressed in the ZAM when compared to the ZIM. The two RAGE ligands (AGEs and HMGB1) induced differential cytokine production (IL1β and TNFα) in the amnion and choriodecidua.

Conclusion

Considered together, these results indicate that RAGE signaling is present and functional in human FMs. Our work opens the way to a better understanding of FMs weakening dependent on a RAGE-based sterile inflammation.

Study of sRAGE, HMGB1, AGE, and S100A8/A9 Concentrations in Plasma and in Serum-Extracted Extracellular Vesicles of Pregnant Women With Preterm Premature Rupture of Membranes

Preterm premature rupture of membranes (PPROM), defined as rupture of fetal membranes prior to 37 weeks of gestation, complicates approximately 2–4% of pregnancies and is responsible for 40% of all spontaneous preterm births. PPROM arises from complex pathophysiological pathways with a key actor: inflammation. Sterile inflammation is a feature of senescence-associated fetal membrane maturity. During specific steps of sterile inflammation, cells also release highly inflammatory damage-associated molecular pattern markers (DAMPs), such as high-mobility group box 1 (HMGB1) or S100A8/A9, known to link and activate the receptor for advanced glycation end products (RAGE). The objective of this study was to measure longitudinally during pregnancy concentrations of the soluble form of RAGE (sRAGE) and its main ligands (AGE, HMGB1, S100A8/A9) in blood specimens. We studied 246 pregnant women (82 with PPROM and 164 matched control pregnant women without complications) from a cohort of 7,866 pregnant women recruited in the first trimester and followed during pregnancy until delivery. sRAGE, AGE, HMGB1, and S100A8/A9 concentrations were measured in plasma and in serum-extracted extracellular vesicles from first trimester (T1), second trimester (T2), and delivery (D). In plasma, we observed, in both PPROM and control groups, (i) a significant increase of HMGB1 concentrations between T1 vs. T2, T1 vs. D, but not between T2 vs. D; (ii) a significant decrease of sRAGE concentrations between T1 and T2 and a significant increase between T2 and D; (iii) a significant decrease of AGE from T1 to D; (iv) no significant variation of S100A8/A9 between trimesters. In intergroup comparisons (PPROM vs. control group), there were no significant differences in time variation taking into account the matching effects. There was a correlation between plasma and serum-extracted extracellular vesicle concentrations of sRAGE, AGE, HMGB1, and S100A8/A9. Our results suggest that the rupture of fetal membranes (physiological or premature) is accompanied by a variation in plasma concentrations of sRAGE, HMGB1, and AGE. The study of RAGE and its main ligands in extracellular vesicles did not give additional insight into the pathophysiological process conducting to PPROM.

Risk Factors and Outcomes of Preterm Premature Rupture of Membranes in a Cohort of 6968 Pregnant Women Prospectively Recruited

We revisited risk factors and outcomes related to the preterm premature rupture of membranes (PPROM). A total of 7866 pregnant women were recruited during 5 years at their first prenatal visit to the perinatal clinic of the institution. We compared three groups (women without prematurity, women with spontaneous preterm labor with intact membranes (sPL with IM), women with PPROM) regarding 60 criteria about characteristics, lifestyle, medical, gynecological, obstetrical history of mothers, medication during pregnancy, events at delivery, and complications in neonates. Logistic regression analyses adjusting for potential confounding factors were used. Of the 6968 women selected, 189 (2.8%) presented a PPROM, and 225 (3.2%) an sPL with IM. The specific risk factors for PPROM were body mass index (BMI) <18.5 kg/m² (adjusted odds ratio, aOR: 2.00 (1.09-3.67)), history of PPROM (aOR: 2.75 (1.19-6.36)), nulliparity (aOR: 2.52 (1.77-3.60)), gestational diabetes (aOR: 1.87 (1.16-2.99)), and low level of education (aOR: 2.39 (1.20-4.78)). The complications associated with PPROM were abruption placentae, cesarean, APGAR 5' <4, birth weight <2500 g, stillbirth, neonatal jaundice, and hospitalization of mother and neonates. All these complications were also associated with sPL with IM. Our study confirms some of the risk factors of PPROM and highlights a new one: gestational diabetes. Outcomes of PPROM are related to prematurity.

Retinoic Acid Pathway Regulation of Vascular Endothelial Growth Factor in Ovine Amnion

Vascular endothelial growth factor (VEGF) has been proposed as an important regulator of amniotic fluid absorption across the amnion into the fetal vasculature on the surface of the placenta. However, the activators of VEGF expression and action in the amnion have not been identified. Using the pregnant sheep model, we aimed to investigate the presence of the retinoic acid (RA) pathway in ovine amnion and to determine its effect on VEGF expression. Further, we explored relationships between RA receptors and VEGF and tested the hypothesis that RA modulates intramembranous absorption (IMA) through induction of amnion VEGF in sheep fetuses subjected to altered IMA rates. Our study showed that RA receptor isoforms were expressed in sheep amnion, and RA response elements (RAREs) were identified in ovine RARβ and VEGF gene promoters. In ovine amnion cells, RA treatment upregulated RARβ messenger RNA (mRNA) and increased VEGF transcript levels. In sheep fetuses, increases in IMA rate was associated with elevated VEGF mRNA levels in the amnion but not in the chorion. Further, RARβ mRNA was positively correlated with VEGF mRNA levels in the amnion and not chorion. We conclude that an RA pathway is present in ovine fetal membranes and that RA is capable of inducing VEGF. The finding of a positive relationship between amnion VEGF and RARβ during altered IMA rate suggests that the retinoid pathway may play a role through VEGF in regulating intramembranous transport across the amnion.

Cigarette smoke condensate affects the retinoid pathway in human amnion

INTRODUCTION

The preterm premature rupture of membranes (PPROM) is a frequent pathology responsible of more than 30% of preterm births. Tobacco smoking is one of the most frequently described risk factors identified and contributes to the pre term weakening of fetal membranes. As previously demonstrated, all-trans retinoic acid (atRA) regulates several genes involved in the extracellular matrix dynamics, an essential actor in fetal membrane ruptures. We hypothesized that cigarette smoke may affect this pathway in human amnion.

METHODS

Amnion was obtained from full-term fetal membranes collected from non-smoking women after cesarean births and used either as explants or for the isolation of derived epithelial cells. The pro-healing and transcriptomic effects of atRA were studied by a scratch assay experiment and quantitative RT-PCR, respectively, after treatment with dimethyl sulfoxyde (DMSO), atRA, DMSO + cigarette smoke condensate (CSC), or atRA + CSC.

RESULTS

Our results show a strong alteration of the retinoid pathway after CSC treatment on amnion-derived epithelial cells and explants. We first demonstrated that CSC inhibits the activity of the RARE reporter gene in amnion-derived epithelial cells. Then, atRA's effects on both the transcription of its target genes and wound healing were demonstrated to be inhibited or at least decreased by the CSC in human amnion epithelial cells.

DISCUSSION

Here, we demonstrated that CSC altered the retinoid signal, already known to have roles in fetal membrane physiopathology. These results highlight a potential negative action of maternal smoking on the retinoid pathway in human amnion and more generally on pregnancy.

Retinoic Acid Engineered Amniotic Membrane Used as Graft or Homogenate: Positive Effects on Corneal Alkali Burns

Purpose

Alkali burns are the most common, severe chemical ocular injuries, their functional prognosis depending on corneal wound healing efficiency. The purpose of our study was to compare the benefits of amniotic membrane (AM) grafts and homogenates for wound healing in the presence or absence of previous all-trans retinoic acid (atRA) treatment.

Methods

Fifty male CD1 mice with reproducible corneal chemical burn were divided into five groups, as follows: group 1 was treated with saline solution; groups 2 and 3 received untreated AM grafts or grafts treated with atRA, respectively; and groups 4 and 5 received untreated AM homogenates or homogenates treated with atRA, respectively. After 7 days of treatment, ulcer area and depth were measured, and vascular endothelial growth factor (VEGF) and matrix metalloproteinase 9 (MMP-9) were quantified.

Results

AM induction by atRA was confirmed via quantification of retinoic acid receptor β (RARβ), a well-established retinoic acid-induced gene. Significant improvements of corneal wound healing in terms of ulcer area and depth were obtained with both strategies. No major differences were found between the efficiency of AM homogenates and grafts. This positive action was increased when AM was pretreated with atRA. Furthermore, AM induced a decrease in VEGF and MMP-9 levels during the wound healing process. The atRA treatment led to an even greater decrease in the expression of both proteins.

Conclusions

Amnion homogenate is as effective as AM grafts in promoting corneal wound healing in a mouse model. A higher positive effect was obtained with atRA treatment.

Myocilin expression is regulated by retinoic acid in the trabecular meshwork-derived cellular environment

Glaucoma is the leading cause of irreversible blindness and is usually classified as angle closure and open angle glaucoma (OAG). Primary open angle glaucoma represents the most frequent clinical presentation leading to ganglion cell death and optic nerve degeneration as a main consequence of an intraocular pressure' (IOP) increase. The mechanisms of this IOP increase in such pathology remain unclear but one protein called Myocilin could be a part of the puzzle in the trabecular meshwork (TM). Previously described to be transcriptionally regulated by glucocorticoids, the comprehension of the trabecular regulation of Myocilin' expression has only weakly progressed since 15 years. Due to the essential molecular and cellular implications of retinoids' pathway in eye development and physiology, we investigate the potential role of the retinoic acid in such regulation and expression. This study demonstrates that the global retinoids signaling machinery is present in immortalized TM cells and that Myocilin (MYOC) expression is upregulated by retinoic acid alone or combined with a glucocorticoid co-treatment. This regulation by retinoic acid acts through the MYOC promoter which contains a critical cluster of four retinoic acid responsive elements (RAREs), with the RARE-DR2 presenting the strongest effect and binding the RARα/RXRα heterodimer. All together, these results open up new perspectives for the molecular understanding glaucoma pathophysiology and provide further actionable clues on Myocilin gene regulation.

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.

Aquaporins and Fetal Membranes From Diabetic Parturient Women: Expression Abnormalities and Regulation by Insulin

CONTEXT

During pregnancy, aquaporins (AQPs) expressed in fetal membranes are essential for controlling the homeostasis of the amniotic volume, but their regulation by insulin was never explored in diabetic women.

OBJECTIVE

The aim of our study was to investigate the involvement of AQPs 1, 3, 8, and 9 expressed in fetal membranes in diabetic parturient women and the control of their expression by insulin.

DESIGN AND PARTICIPANTS

From 129 fetal membranes in four populations (controls, type 1, type 2 [T2D], and gestational diabetes [GD]), we established an expression AQP profile. In a second step, the amnion was used to study the control of the expression and functions of AQPs 3 and 9 by insulin.

MAIN OUTCOMES AND MEASURES

The expression of transcripts and proteins of AQPs was studied by quantitative RT-PCR and ELISA. We analyzed the regulation by insulin of the expression of AQPs 3 and 9 in the amnion. A tritiated glycerol test enabled us to measure the impact of insulin on the functional characteristics. Using an inhibitor of phosphatidylinositol 3-kinase, we analyzed the insulin intracellular signaling pathway.

RESULTS

The expression of AQP3 protein was significantly weaker in groups T2D and GD. In nondiabetic fetal membranes, we showed for the amnion (but not for the chorion) a significant repression by insulin of the transcriptional expression of AQPs 3 and 9, which was blocked by a phosphatidylinositol 3-kinase inhibitor.

CONCLUSION

In fetal membranes, the repression of AQP3 protein expression and functions observed in vivo is allowed by the hyperinsulinism described in pregnant women with T2D or GD.

Metabolic disturbances of the vitamin A pathway in human diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a common life-threatening congenital anomaly resulting in high rates of perinatal death and neonatal respiratory distress. Some of the nonisolated forms are related to single-gene mutations or genomic rearrangements, but the genetics of the isolated forms (60% of cases) still remains a challenging issue. Retinoid signaling (RA) is critical for both diaphragm and lung development, and it has been hypothesized that subtle disruptions of this pathway could contribute to isolated CDH etiology. Here we used time series of normal and CDH lungs in humans, in nitrofen-exposed rats, and in surgically induced hernia in rabbits to perform a systematic transcriptional analysis of the RA pathway key components. The results point to CRPBP2, CY26B1, and ALDH1A2 as deregulated RA signaling genes in human CDH. Furthermore, the expression profile comparisons suggest that ALDH1A2 overexpression is not a primary event, but rather a consequence of the CDH-induced lung injury. Taken together, these data show that RA signaling disruption is part of CDH pathogenesis, and also that dysregulation of this pathway should be considered organ specifically.

DNA methyl transferases are differentially expressed in the human anterior eye segment

PURPOSE

DNA methylation is an epigenetic mark involved in the control of genes expression. Abnormal epigenetic events have been reported in human pathologies but weakly documented in eye diseases. The purpose of this study was to establish DNMT mRNA and protein expression levels in the anterior eye segment tissues and their related (primary or immortalized) cell cultures as a first step towards future in vivo and in vitro methylomic studies.

METHODS

Total mRNA was extracted from human cornea, conjunctiva, anterior lens capsule, trabeculum and related cell cultures (cornea epithelial, trabecular meshwork, keratocytes for primary cells; and HCE, Chang, B-3 for immortalized cells). cDNA was quantified by real-time PCR using specific primers for DNMT1, 2, 3A, 3B and 3L. Immunolocalization assays were carried out on human cornea using specific primary antibodies for DNMT1, 2 and 3A, 3B and 3L.

RESULTS

All DNMT transcripts were detected in human cornea, conjunctiva, anterior lens capsule, trabeculum and related cells but showed statistically different expression patterns between tissues and cells. DNMT2 protein presented a specific and singular expression pattern in corneal endothelium.

CONCLUSIONS

This study produced the first inventory of the expression patterns of DNMTs in human adult anterior eye segment. Our research highlights that DNA methylation cannot be ruled out as a way to bring new insights into well-known ocular diseases. In addition, future DNA methylation studies using various cells as experimental models need to be conducted with attention to approach the results analysis from a global tissue perspective.

Regulation of DNA methylation patterns by CK2-mediated phosphorylation of Dnmt3a

DNA methylation is a central epigenetic modification that is established by de novo DNA methyltransferases. The mechanisms underlying the generation of genomic methylation patterns are still poorly understood. Using mass spectrometry and a phosphospecific Dnmt3a antibody, we demonstrate that CK2 phosphorylates endogenous Dnmt3a at two key residues located near its PWWP domain, thereby downregulating the ability of Dnmt3a to methylate DNA. Genome-wide DNA methylation analysis shows that CK2 primarily modulates CpG methylation of several repeats, most notably of Alu SINEs. This modulation can be directly attributed to CK2-mediated phosphorylation of Dnmt3a. We also find that CK2-mediated phosphorylation is required for localization of Dnmt3a to heterochromatin. By revealing phosphorylation as a mode of regulation of de novo DNA methyltransferase function and by uncovering a mechanism for the regulation of methylation at repetitive elements, our results shed light on the origin of DNA methylation patterns.

[Medical indoor environment counsellor (MIEC) in Burgundy: evaluation by physicians and patients]

Since December 2009, chest physicians and allergologists in Burgundy have been able to call upon a medical indoor environment counsellor (MIEC). The consultations are free for the patient and are undertaken following a medical referal after systematic cutaneous prick tests.

AIMS

To describe the indications, the distribution of prescriptions and to measure the impact of the counsellor's visits on the first 100 patients at 6 months and on the physicians at 18 months.

METHOD

Telephone interviews with the 67 physicians (whether prescribers or not) concerning their motivation and/or expectations, and with the first 100 patients concerning follow up of the recommendations.

RESULTS

Seventy percent of the physicians replied (n=47). The satisfaction of prescribers (n=22) was 8.42/10. The indications were rhinitis and a poorly controlled asthma. The requests concerned the search for dust mite (50%) and moulds (46%). Eighty-four percent of the physicians discussed the MIEC's report with the patients. The patients' symptoms were rhinitis (79%), asthma (57%) and conjunctivitis (33%). The Acarex test(®), performed in cases of positive prick tests to house dust mites (n=72), was strongly positive for 67 patients. Sixteen mould samples out of 21 were above the standard concentrations. Sixty-nine patients had followed the recommendations of the MIEC.

CONCLUSION

The impact of the MIEC visits was perceived as positive by the physicians and the patients. The medico-economic impact warrants further evaluation.

[Rupture of membranes: pathophysiology, diagnosis, consequences and management]

Rupture of membranes (ROM) depends on mechanical stretch, extracellular matrix components imbalance and increased apoptosis. It occurs in 2 to 3% of all pregnancies before 37 weeks' gestation (WG) and in up to 10% at term. Main consequences are labor induction and risk of maternal-fetal infection. ROM is associated with one third of preterm births and about 20% of perinatal mortality. This review deals with recent knowledge concerning ROM including diagnosis and management. In many cases, ROM is easily identified by clinical examination. In other cases, the use of vaginal pH appears to be less efficient than the use of immunochromatographic strips based on IGFBP-1 or PAMG-1 detection. Before 34WG, conservative management consists in in utero transfer, antibioprophylaxis and corticosteroids. After 37WG, delivery is the most appropriate option. Between 34 and 37WG, recent studies demonstrate that induction of labour does not improve pregnancy outcomes. Therefore, expectant management can be the first option between 34 and 37WG when no active infection is suspected especially in case of unfavourable cervix.

[Implications of retinoid pathway in human fetal membranes: study of target genes]

Retinoids (active derivatives of vitamin A) were already demonstrated to be important morphogenes and their implication at the placental and fetal level was already established. A new field of research is now developed in order to show their role on fetal membranes constituted by amnion and chorion. To describe the role of retinoids on these membranes, our studies were focused on target gene research. Firstly, all metabolism enzymes needed to vitamin A pathways were demonstrated to be present and active in signal transduction. Secondly, a bioinformatic analysis was performed to assess a list of potential target genes that could be classified in different biological pathways (inflammation, retinoids, hormones, vascularization, extracellular matrix and water homeostasis). Then, it was demonstrated that the gene coding for PLAT, implied in the degradation of extracellular matrix during programmed or premature rupture of membranes, is regulated by retinoids in a two steps mechanism. Finally, preliminary data showed that some aquaporins, which control water transport across membranes, are expressed and regulated by retinoids in the fetal membranes. A disregulation in pathologies like oligo or poly-hydramnios can be anticipated. Improvement of our knowledge about the retinoid implications is a key point in order to obtain a precise and complete documented cartography of the vitamin A (regulating) in amniotic membranes (regulated) that will permit the development of new diagnostic and therapeutic strategies.

Retinoids regulate human amniotic tissue-type plasminogen activator gene by a two-step mechanism

The collagenolytic effects of the tissue-type plasminogen activator (t-PA) leading to extracellular matrix degradation are clearly involved in the physiopathology of human foetal membranes rupture. Nevertheless, the regulation of t-PA gene expression in extraembryonic developmental contexts remains unknown. The aim of our study is to propose the retinoic acids (RAs) as molecular regulators of t-PA expression in foetal membranes. RA induced t-PA mRNA and proteins in a time-dependent manner in amniotic membrane explants and Wistar Institute Susan Hayflick (WISH) cells. Furthermore, the use of cycloheximide revealed a two-step regulation of t-PA gene. Gene reporter assays confirmed that the RA-induced t-PA gene expression occurred through interactions of retinoid receptors (RARs and RXRs) with a DR5 response element located at –7 kb from the transcription site. Site-directed mutagenesis of this region of the t-PA promoter showed that SP1 factor was also retinoid-mediated induction, and immunoprecipitation assays revealed that SP1 and RAR/RXR interacted physically. Chromatin immunoprecipitation demonstrated that interactions between RARs, RXRs and t-PA promoter were time dependent: RAR-α/RXR-α bound DR5 motif before and up to 12 hrs of RA exposure, and RAR-β/RXR-α bound DR5 response element after 12 hrs of RA treatment. Finally, experiments using shRNA and RAR-β-specific antagonist revealed that reducing RAR-β induction decreased t-PA induction. Altogether, our results established that the RA-mediated regulation of t-PA in human foetal membranes occurred through two steps, with a major role played by RAR-β.

Molecular and metabolic retinoid pathways in the human ocular surface

PURPOSE

To maintain its integrity, the human ocular surface (cornea and conjunctiva) has an absolute requirement for vitamin A and its active derivatives, the retinoic acids. These retinoids regulate transcriptional levels of target genes through the activation of members of a super-family of ligand-dependant nuclear receptors that feature retinoic acid receptors (RAR) alpha, beta, and gamma as well as retinoid X receptors (RXR) alpha, beta, and gamma. The expression patterns of these receptors have been partial characterized in rabbit, mouse, and human cornea and conjunctiva, but systematic tissue and cellular expression of the three RARs and three RXRs had to be completed at the adult human ocular surface. The first objective of our work was to define their expression patterns in term of genes and proteins for total human conjunctiva, cornea, and the major cell types comprising the adult human ocular surface. The second objective was to demonstrate the presence of different enzymes transforming vitamin A to retinoic acid and the functionality of this metabolic pathway in the corneal epithelium.

METHODS

Total mRNA was extracted from human total cornea, conjunctiva, corneal epithelial cells (primary culture and established cell line), corneal keratocytes (primary culture), corneal endothelial cells (established cell line), and conjunctival epithelial cells (established cell line) and was submitted to reverse transcription-polymerase chain reaction (RT-PCR) analysis to determine the expression patterns of the RARs and RXRs using specific primers. Immunological staining (via histochemistry and cellular chemistry) experiments were performed to better localize RAR and RXR proteins in the ocular surface at tissue and cellular levels. We also checked mRNA expression of cellular retinol binding proteins (CRBPs) and cellular retinoic acid binding proteins (CRABPs) with the enzymes involved in retinoic acid generation, i.e., alcohol dehydrogenases (ADHs) and retinal dehydrogenases (RALDHs) or degradation (Cyp26 family members). The enzymatic generation of functional retinoids was confirmed using epithelial corneal cells treated with specific inhibitors of retinol metabolism.

RESULTS

RAR alpha, RAR gamma, and RXR alpha are expressed in the cornea, conjunctiva, and all of their constitutive cells, whereas RXR gamma and RXR beta were never detected in the cornea or conjunctiva. RAR beta was absent in primary cultures of corneal keratinocytes. ADH3, ADH4, dehydrogenase/reductase (SDR family) 4 (DHRS4), dehydrogenase/reductase (SDR family) 9 (DHRS9), RALDH1, and RALDH3 are expressed in the ocular surface, as were the retinoid-binding proteins CRBP1, CRABP1, and CRABP2. Retinol dehydrogenase 4 (RODH4) was only detected in the conjunctiva. Corneal epithelial cells convert retinol into retinoic acid using an enzymatic pathway.

CONCLUSIONS

For the first time, we have established an exhaustive description of the expressions patterns of RARs, RXRs, ADHs, RALDHs, CRBP, and CRABPs in the human ocular surface. Our results for the human ocular surface demonstrated the presence of all the metabolic and molecular actors of the retinoic acid signaling pathway. We also demonstrated the enzymatic conversion of retinol into active retinoids in the corneal environment.

Viral oncoproteins target the DNA methyltransferases

Small DNA tumour viruses have evolved a number of mechanisms to drive nondividing cells into S phase. Virally encoded oncoproteins such as adenovirus E1A and human papillomavirus (HPV) E7 can bind an array of cellular proteins to override proliferation arrest. The DNA methyltransferase Dnmt1 is the major mammalian enzyme responsible for maintaining CpG methylation patterns in the cell following replication. One of the hallmarks of tumour cells is disrupted DNA methylation patterns, highlighting the importance of the proper regulation of DNA methyltransferases in normal cell proliferation. Here, we show that adenovirus 5 E1A and HPV-16 E7 associate in vitro and in vivo with the DNA methyltransferase Dnmt1. Consistent with this interaction, we find that E1A and E7 can purify DNA methyltransferase activity from nuclear extracts. These associations are direct and mediated by the extreme N-terminus of E1A and the CR3 zinc-finger domain of E7. Furthermore, we find that a point mutant at leucine 20 of E1A, a residue known to be critical for its transformation functions, is unable to bind Dnmt1 and DNA methyltransferase activity. Finally, both E1A and E7 can stimulate the methyltransferase activity of Dnmt1 in vitro. Our results provide the first indication that viral oncoproteins bind and regulate Dnmt1 enzymatic activity. These observations open up the possibility that this association may be used to control cellular proliferation pathways and suggest a new mechanism by which small DNA tumour viruses can steer cells through the cell cycle.

Activation of the human pregnancy-specific glycoprotein PSG-5 promoter by KLF4 and Sp1

Pregnancy-specific glycoproteins (PSGs) are major placental proteins thought to be essential for the maintenance of gestation. Little is known about the regulation of expression of the 11 genes encoding these proteins. It was previously demonstrated that Krüppel-like factor 6 (KLF6) and specific-protein 1 (Sp1) bind to conserved sequence within the PSG-5 gene promoter. Informatics analysis revealed the presence of one potential binding site for Krüppel-like factor 4 (KLF4), in the PSG-5 promoter, suggesting a potential transcriptional regulator role for KLF4. Using gene promoter-reporter transfections and X-ChIP assays, we demonstrated that KLF4 is an activator of the PSG-5 promoter by binding to a KLF consensus like binding which includes the Core Promoter Element region (-147/-140). Furthermore, we used previous data showing the binding of Sp1 transcription factor to a GT-box (-443/-437) and co-transfection assays with KLF4 and Sp1 to demonstrate the strong synergic activity of these two factors on the PSG-5 promoter.

The Polycomb group protein EZH2 directly controls DNA methylation

The establishment and maintenance of epigenetic gene silencing is fundamental to cell determination and function. The essential epigenetic systems involved in heritable repression of gene activity are the Polycomb group (PcG) proteins and the DNA methylation systems. Here we show that the corresponding silencing pathways are mechanistically linked. We find that the PcG protein EZH2 (Enhancer of Zeste homolog 2) interacts-within the context of the Polycomb repressive complexes 2 and 3 (PRC2/3)-with DNA methyltransferases (DNMTs) and associates with DNMT activity in vivo. Chromatin immunoprecipitations indicate that binding of DNMTs to several EZH2-repressed genes depends on the presence of EZH2. Furthermore, we show by bisulphite genomic sequencing that EZH2 is required for DNA methylation of EZH2-target promoters. Our results suggest that EZH2 serves as a recruitment platform for DNA methyltransferases, thus highlighting a previously unrecognized direct connection between two key epigenetic repression systems.

Transcriptional control of the human pregnancy-specific glycoprotein 5 gene is dependent on two GT-boxes recognized by the ubiquitous specificity protein 1 (Sp1) transcription factor

Pregnancy-specific glycoprotein 5 gene (PSG-5) belongs to the human pregnancy-specific glycoprotein family, encoded by eleven highly similar and transcriptionally active genes. High levels of PSG biosynthesis are restricted to the placenta syncytiotrophoblast and are essential for the maintenance of normal gestation in mammalian species. We have investigated here the nature of the transcription factors that recognize the FP1 (-455/-433) and the CPE (-147/-140) regulatory sequences that significantly contribute to basal PSG-5 promoter activity. Both elements bear a similar GT-box motif; and DNA-protein complex formation, as well as promoter activity, is largely dependent on the integrity of these GT-box sequences. Gel shift, super gel shift and UV-crosslinking experiments clearly demonstrate that the ubiquitous specificity protein 1 (Sp1) is the major transcription factor involved in complex formation with both cis-acting elements in normal term placenta tissue and in PSG-non-expressing COS-7 cells. Furthermore, transfection experiments indicate that Sp1 activates PSG-5 promoter constructs. In addition, we show that Sp1 is indeed co-expressed with PSG genes in the syncytiotrophoblast cells, stressing its potential role in the in vivo regulation of PSG expression.

Placental expression of SCO-spondin during mouse and human development

During mammalian development, the placenta is a transitory but indispensable structure for a harmonious gestation involving several biological processes, such as adhesion, differentiation, apoptosis or cellular guidance. Nevertheless, the molecular pathways implicated during the placentation are still not totally understood. We previously described, the subcommissural organ (SCO)-spondin, a member of the 'thrombospondin' super-family, which is strongly expressed during mammalian central nervous system development. This extra-cellular matrix glycoprotein shows a unique arrangement of several conserved domains, including thrombospondin type 1 repeats, low-density lipoprotein receptor type A domains, two epidermal growth factor-like domains, and N- and C-terminal von Willebrand factor cysteine-rich domains. The presence of these domains strongly suggests the SCO-spondin involvement in cellular events occurring during placental development and physiology. In order to define this new role of SCO-spondin during development, we demonstrated its expression at relevant steps of gestation in human and mouse placenta, using RT-PCR, immunohistochemistry and Western-blot experiments. These data initiate further insights into the molecular and genetic functions of the neuronal gene SCO-spondin during trophoblastic and more globally during placental physiology and development.

Regulation of corneal keratin-12 gene expression by the human Krüppel-like transcription factor 6

PURPOSE

The keratin-12 (K12) protein is essential for the integrity of the corneal epithelium. This study was conducted to investigate the possible involvement of Krüppel-like factor 6 (KLF6) in the corneal regulation of K12 gene expression, in view of the presence of one KLF6 potential binding site in the human K12 promoter and the known role of KLF6 in regulating keratin gene expression.

METHODS

RT-PCR, Western blot analysis, and immunolocalization experiments were used to investigate the expression of KLF6 mRNA and protein in five human total corneas. The same experimental design was used to explore human corneal epithelial (HCE) cells in 20 patients and a HCE cell line. The ability of the KLF6 protein to modulate K12 promoter activity was studied in the HCE cell line, by transient transfections with a KLF6 expression plasmid and promoter-reporter gene assays. Gel-shift assays were performed to confirm the interactions between the KLF6 protein and specific sequences of the K12 promoter.

RESULTS

The presence of KLF6 transcripts and proteins in human total corneal extracts was demonstrated. Immunohistofluorescence experiments showed positive staining specifically present in the corneal epithelial layer. KLF6 transcripts and proteins were also present in corneal epithelial cells in 20 patients and the HCE cell line. Transient transfections of KLF6 showed statistical transactivation of the K12 promoter in HCE cells. The gel-shift assay showed a physical interaction between KLF6 and the K12 promoter.

CONCLUSIONS

The expression of KLF6 in HCE cells and its role in the regulation of K12 gene expression were demonstrated.

PAV-1, a new rat hepatic stellate cell line converts retinol into retinoic acid, a process altered by ethanol

During liver fibrogenesis or long term culture, hepatic stellate cells (HSCs) evolved from "quiescent" to activated phenotype called "myofibroblast-like", a transition prevented by retinoic acid (RA). Little is known about RA generation by HSCs. Our study aimed to check the ability of these cells to produce RA from retinol (Rol) and the alterations of this metabolic step by ethanol. To study this metabolic pathway, primary cultures of HSCs represent the most physiological model but technically suffer several drawbacks. To circumvent these problems, an immortalized rat HSC line (named PAV-1) has been established. We validated PAV-1 cell line as a convenient model to study retinoids metabolism by HSCs. Then, we showed that PAV-1 cells express Rol-binding proteins (RBPs), enzymes and nuclear receptors involved in RA signaling pathway. We also demonstrated in situ generation of functional all-trans-RA (ATRA), using transient transfections with a RA-sensitive reporter gene, in situ modulation of tissue transglutaminase (tTG) activity and HPLC experiments. This production was Rol dose-dependent; 4-methylpyrazole, citral, and ethanol-inhibited which argues in favor of an enzymatic process.In conclusion, we first demonstrate in situ RA generation from Rol in a newly immortalized rat HSC line, named PAV-1. Inhibition of RA production by ethanol in PAV-1 and recent data, suggesting fundamental role of RA to prevent fibrosis development in the liver, allow us to hypothesize that Rol metabolism could be a primary target for ethanol during development of hepatic fibrosis.

Human choriocarcinoma cell line JEG-3 produces and secretes active retinoids from retinol

Vitamin A (retinol) and its active derivatives (the retinoids) are essential for growth and development of the mammalian fetus. Maternally-derived retinol has to pass through the placenta to reach the developing fetus. Despite its apparent importance, little is known about placental metabolism of retinol, and particularly placental production and/or secretion of active retinoids. It has been previously considered that retinoids are recruited from the uterine environment to influence placental development and function during gestation. We have studied retinoid metabolism in the human choriocarcinoma cell line JEG-3 and demonstrate, for the first time, that active retinoids are produced endogenously by the JEG-3 cell line from retinol. These retinoids induce gene expression from a retinoic acid-responsive enhancer element reporter plasmid and modulate placental transglutaminase activity. Furthermore, retinoids are secreted from JEG-3, as shown by the activation of retinoic acid-responsive beta lacZ reporter cells grown in conditioned media. These results suggest that there could be an active role for trophoblast-derived retinoids during human development.

Use of transgenic mice model for understanding the placentation: towards clinical applications in human obstetrical pathologies?

The mammalian embryo and fetus are unable to develop without a well-established, functional placenta. This transitory yet indispensable structure attaches the conceptus to the uterus and establishes the vascular connections necessary for nutrient and gaseous exchange between maternal and fetal compartments. Genetic targeting strategy allows the generation of mice lacking a specific gene. Such approaches reveal: (i) the high incidence of mutant embryonic or fetal death in utero, and (ii) the extraembryonic (placental) causes of these deaths. Due to the similarities presented between mouse and human placenta, we propose to use the potential of mouse targeting experiments as a model in order to understand human obstetrical pathologies. In this paper, we first review genes that have been demonstrated to be required in mice for implantation, choriovitelline and chorioallantoic placentation. Using examples (integrins, homeoboxs, hepatocyte growth factor or epidermal growth factor receptor...) we demonstrate the reality and efficiency of such an approach. Other candidate genes (receptor of leukemia inhibitory factor, Wnt2 or retinoic acid receptor alpha...) in order to understand, prevent and treat human obstetrical pathologies.

Co-localization of KLF6 and KLF4 with pregnancy-specific glycoproteins during human placenta development

Pregnancy-specific glycoproteins (PSGs) are major placental proteins essential for the maintenance of normal gestation. However, little is known about their gene expression regulation during placentation. It was previously demonstrated that the human core promoter binding protein recently renamed Krüppel-like factor (KLF) 6 binds to a highly conserved sequence within the PSG promoters and is mainly expressed in human term placenta. Here, we determined the expression pattern of the 13 other KLFs during human placental development. We demonstrate that eight KLFs exhibit specific expression patterns in human placental tissues and membranes, in favor of a functional cooperation of specific KLFs during placentation. In addition, we demonstrate that KLF6, KLF4 and PSG proteins are co-expressed in same cell types of placental villi and membranes. This experimental evidence further strengthens the potential cross talk of both transcription factors for PSG gene regulation in vivo.

Esterification of vitamin A by the human placenta involves villous mesenchymal fibroblasts

Vitamin A (retinol) and its active derivatives (retinoic acids) are essential for growth and development of the mammalian fetus. Maternally derived retinol must pass the placenta to reach the developing fetus. Despite its apparent importance, little is known concerning placental transfer and metabolism of retinol, and particularly of placental production and storage of retinyl esters. To elucidate this metabolic pathway, we incubated, in the presence of retinol, 1) human full-term placental explants and 2) primary cultures of major cells types contributing to placental function: trophoblasts and villous mesenchymal fibroblasts. We used HPLC to determine the types and concentrations of retinyl esters produced by these explants and cells. About 14% of total cellular retinol in placental explants was esterified. The most abundant esters were myristate and palmitate. Primary cell cultures showed that fibroblasts efficiently produced retinyl esters, but trophoblasts did not. In both types of experiments, no retinyl esters were detected in the culture medium, suggesting that retinyl esters were produced for storage purpose. These results suggest that villous mesenchymal fibroblasts are primary sites of retinol esterification and storage in the placenta.