Hypoxia and placental remodelling

Mice Placental ECM Components May Provide A Three-Dimensional Placental Microenvironment

Bioethical limitations impair deeper studies in human placental physiology, then most studies use human term placentas or murine models. To overcome these challenges, new models have been proposed to mimetize the placental three-dimensional microenvironment. The placental extracellular matrix plays an essential role in several processes, being a part of the establishment of materno-fetal interaction. Regarding these aspects, this study aimed to investigate term mice placental ECM components, highlighting its collagenous and non-collagenous content, and proposing a potential three-dimensional model to mimetize the placental microenvironment. For that, 18.5-day-old mice placenta, both control and decellularized (n = 3 per group) were analyzed on Orbitrap Fusion Lumos spectrometer (ThermoScientific) and LFQ intensity generated on MaxQuant software. Proteomic analysis identified 2317 proteins. Using ECM and cell junction-related ontologies, 118 (5.1%) proteins were filtered. Control and decellularized conditions had no significant differential expression on 76 (64.4%) ECM and cell junction-related proteins. Enriched ontologies in the cellular component domain were related to cell junction, collagen and lipoprotein particles, biological process domain, cell adhesion, vasculature, proteolysis, ECM organization, and molecular function. Enriched pathways were clustered in cell adhesion and invasion, and labyrinthine vasculature regulation. These preserved ECM proteins are responsible for tissue stiffness and could support cell anchoring, modeling a three-dimensional structure that may allow placental microenvironment reconstruction.

RNA Network Interactions During Differentiation of Human Trophoblasts

In the human placenta, two trophoblast cell layers separate the maternal blood from the villous basement membrane and fetal capillary endothelial cells. The inner layer, which is complete early in pregnancy and later becomes discontinuous, comprises the proliferative mononuclear cytotrophoblasts, which fuse together and differentiate to form the outer layer of multinucleated syncytiotrophoblasts. Because the syncytiotrophoblasts are responsible for key maternal-fetal exchange functions, tight regulation of this differentiation process is critical for the proper development and the functional role of the placenta. The molecular mechanisms regulating the fusion and differentiation of trophoblasts during human pregnancy remain poorly understood. To decipher the interactions of non-coding RNAs (ncRNAs) in this process, we exposed cultured primary human trophoblasts to standard in vitro differentiation conditions or to conditions known to hinder this differentiation process, namely exposure to hypoxia (O₂ < 1%) or to the addition of dimethyl sulfoxide (DMSO, 1.5%) to the culture medium. Using next generation sequencing technology, we analyzed the differential expression of trophoblastic lncRNAs, miRNAs, and mRNAs that are concordantly modulated by both hypoxia and DMSO. Additionally, we developed a model to construct a lncRNA-miRNA-mRNA co-expression network and inferred the functions of lncRNAs and miRNAs via indirect gene ontology analysis. This study improves our knowledge of the interactions between ncRNAs and mRNAs during trophoblast differentiation and identifies key biological processes that may be impaired in common gestational diseases, such as fetal growth restriction or preeclampsia.

Hypoxia and Mitochondrial Dysfunction in Pregnancy Complications

Hypoxia is a common and severe stress to an organism's homeostatic mechanisms, and hypoxia during gestation is associated with significantly increased incidence of maternal complications of preeclampsia, adversely impacting on the fetal development and subsequent risk for cardiovascular and metabolic disease. Human and animal studies have revealed a causative role of increased uterine vascular resistance and placental hypoxia in preeclampsia and fetal/intrauterine growth restriction (FGR/IUGR) associated with gestational hypoxia. Gestational hypoxia has a major effect on mitochondria of uteroplacental cells to overproduce reactive oxygen species (ROS), leading to oxidative stress. Excess mitochondrial ROS in turn cause uteroplacental dysfunction by damaging cellular macromolecules, which underlies the pathogenesis of preeclampsia and FGR. In this article, we review the current understanding of hypoxia-induced mitochondrial ROS and their role in placental dysfunction and the pathogenesis of pregnancy complications. In addition, therapeutic approaches selectively targeting mitochondrial ROS in the placental cells are discussed.

LncRNA MEG3 inhibits trophoblast invasion and trophoblast-mediated VSMC loss in uterine spiral artery remodeling

Extravillous trophoblasts (EVTs) migrate into uterine decidua and induce vascular smooth muscle cell (VSMC) loss through mechanisms thought to involve migration and apoptosis, achieving complete spiral artery remodeling. Long noncoding RNA maternally expressed gene 3 (MEG3) can regulate diverse cellular processes, such as proliferation and migration, and has been discovered highly expressed in human placenta tissues. However, little is known about the role of MEG3 in modulating EVT functions and EVT-induced VSMC loss. In this study, we first examined the location of MEG3 in human first-trimester placenta by in situ hybridization. Then, exogenous upregulation of MEG3 in HTR-8/SVneo cells was performed to investigate the effects of MEG3 on EVT motility and EVT capacity to displace VSMCs. Meanwhile, the molecules mediating EVT-induced VSMC loss, such as tumor necrosis factor-α (TNF-α), Fas ligand (FasL), and tumor necrosis factor-α-related apoptosis-inducing ligand (TRAIL) were detected at transcriptional and translational levels. Finally, VSMCs were cocultured with MEG3-upregulated HTR-8/SVneo to explore the role of MEG3 on EVT-mediated VSMC migration and apoptosis. Results showed that MEG3 was expressed in trophoblasts in placental villi and decidua, and MEG3 enhancement inhibited HTR-8/SVneo migration and invasion. Meanwhile, the displacement of VSMCs by HTR-8/SVneo and the expression of TNF-α, FasL and TRAIL in HTR-8/SVneo were reduced following MEG3 overexpression in HTR-8/SVneo. Furthermore, HTR-8/SVneo with MEG3 upregulation impaired VSMC migration and apoptosis. The PI3K/Akt pathway, which is possibly downstream, was inactivated in MEG3-upregulated HTR-8/SVneo. These findings suggest that MEG3 might be a negative regulator of spiral artery remodeling via suppressing EVT invasion and EVT-mediated VSMC loss.

Placental Adaptation to Early-Onset Hypoxic Pregnancy and Mitochondria-Targeted Antioxidant Therapy in a Rodent Model

The placenta responds to adverse environmental conditions by adapting its capacity for substrate transfer to maintain fetal growth and development. Early-onset hypoxia effects on placental morphology and activation of the unfolded protein response (UPR) were determined using an established rat model in which fetal growth restriction is minimized. We further established whether maternal treatment with a mitochondria-targeted antioxidant (MitoQ) confers protection during hypoxic pregnancy. Wistar dams were exposed to normoxia (21% O2) or hypoxia (13% to 14% O2) from days 6 to 20 of pregnancy with and without MitoQ treatment (500 μmol/L in drinking water). On day 20, animals were euthanized and weighed, and the placentas from male fetuses were processed for stereology to assess morphology. UPR activation in additional cohorts of frozen placentas was determined with Western blot analysis. Neither hypoxic pregnancy nor MitoQ treatment affected fetal growth. Hypoxia increased placental volume and the fetal capillary surface area and induced mitochondrial stress as well as the UPR, as evidenced by glucose-regulated protein 78 and activating transcription factor (ATF) 4 protein up-regulation. MitoQ treatment in hypoxic pregnancy increased placental maternal blood space surface area and volume and prevented the activation of mitochondrial stress and the ATF4 pathway. The data suggest that mitochondria-targeted antioxidants may be beneficial in complicated pregnancy via mechanisms protecting against placental stress and enhancing placental perfusion.

Leptin protects placental cells from apoptosis induced by acidic stress

Development of the human placenta is critical for a successful pregnancy. The placenta allows the exchange of oxygen and carbon dioxide and is crucial to manage acid-base balance within a narrow pH. It is known that low pH levels are a risk of apoptosis in several tissues. However, there has been little discussion about the effect of acidic stress in the placenta. Leptin is produced by the placenta with a trophic autocrine effect. Previous results of our group have demonstrated that leptin prevents apoptosis of trophoblast cells under different stress conditions such as serum deprivation and hyperthermia. The purpose of the present work is to evaluate acidic stress consequences in trophoblast explant survival and to determine leptin action in these conditions. For this objective, term human trophoblast explants were cultured at physiological pH (pH 7.4) and at acidic pH (pH 6.8) in the presence or absence of leptin. Western blot assays were performed to study the abundance of active caspase-3 and the p89 fragment of PARP-1. Pro-apoptotic and pro-survival members of Bcl-2 family, as Bax, t-Bid, and Bcl-2, were studied. Moreover, p53 pathway was also evaluated including Mdm-2, the main p53 regulator. Active caspase-3 and cleaved PARP-1 abundances were increased at low extracellular pH. Moreover, t-Bid levels were also augmented as well as p53 expression and phosphorylation on S46. Leptin treatment prevents the consequences of acidosis, decreasing p53 expression and increasing Mdm-2 expression. In summary, this work demonstrated for first time that low pH induces apoptosis of human trophoblast explants involving apoptotic intrinsic pathway, and leptin impairs this effect.

New data about preeclampsia: some possibilities of prevention

This concise report deals with the known effects of progestogen lack in early pregnancy with failure of implantation and blood supply to the placenta depending on proper trophoblast invasion, spiral artery remodeling, and vessel dilatation. The pathophysiology of preeclampsia will be outlined and the most recent data on the effect of dydrogesterone presented. Dydrogesterone appears to be able to reduce significantly the development of preeclampsia. The effect is related to begin with such prevention and this should be continued until 37th weeks of gestation which would also mean prevention of premature labor.

Noncoding RNAs Carried by Extracellular Vesicles in Endocrine Diseases

RNA molecules are essential and fine regulators of important biological processes. Their role is well documented also in the endocrine system, both in physiological and pathological conditions. Increasing interest is arising about the function and the importance of noncoding RNAs shuttled by extracellular vesicles (EVs). In fact, EV membrane protects nucleic acids from enzyme degradation. Nowadays, the research on EVs and their cargoes, as well as their biological functions, faces the lack of standardization in EV purification. Here, the main techniques for EV isolation are discussed and compared for their advantages and vulnerabilities. Despite the possible discrepancy due to methodological variability, EVs and their RNA content are reported to be key mediators of intercellular communication in pathologies of main endocrine organs, including the pancreas, thyroid, and reproductive system. In particular, the present work describes the role of RNAs contained in EVs in pathogenesis and progression of several metabolic dysfunctions, including obesity and diabetes, and their related manifestations. Their importance in the establishment and progression of thyroid autoimmunity disorders and complicated pregnancy is also discussed. Preliminary studies highlight the attractive possibility to use RNAs contained in EVs as biomarkers suggesting their exploitation for new diagnostic approaches in endocrinology.

Placental Exosomes as Early Biomarker of Preeclampsia: Potential Role of Exosomal MicroRNAs Across Gestation

CONTEXT

There is a need to develop strategies for early prediction of patients who will develop preeclampsia (PE) to establish preventive strategies to reduce the prevalence and severity of the disease and their associated complications.

OBJECTIVE

The objective of this study was to investigate whether exosomes and their microRNA cargo present in maternal circulation can be used as early biomarker for PE.

DESIGN, SETTING, PATIENTS, AND INTERVENTIONS

A retrospective stratified study design was used to quantify total exosomes and placenta-derived exosomes present in maternal plasma of normal (n = 32 per time point) and PE (n = 15 per time point) pregnancies. Exosomes present in maternal circulation were determined by nanoparticle tracking analysis. An Illumina TruSeq® Small RNA Library Prep Kit was used to construct a small RNA library from exosomal RNA obtained from plasma samples.

RESULTS

In presymptomatic women, who subsequently developed PE, the concentration of total exosomes and placenta-derived exosomes in maternal plasma was significantly greater than those observed in controls, throughout pregnancy. The area under the receiver operating characteristic curves for total exosome and placenta-derived exosome concentrations were 0.745 ± 0.094 and 0.829 ± 0.077, respectively. In total, over 300 microRNAs were identified in exosomes across gestation, where hsa-miR-486-1-5p and hsa-miR-486-2-5p were identified as the candidate microRNAs.

CONCLUSIONS

Although the role of exosomes during PE remains to be fully elucidated, we suggest that the concentration and content of exosomes may be of diagnostic utility for women at risk for developing PE.

Prevalence of Intervillous Thrombi Is Increased in Placentas from Pregnancies Complicated by Diabetes

Intervillous thrombus (IVT) is a placental pathology of unclear cause. One possible cause is that IVT protects against fetomaternal transfusion due to trophoblastic disruption. A role for hyperglycemia in trophoblast apoptosis has been suggested. We sought to determine whether placentas from pregnancies complicated by diabetes had an increased incidence of IVT. Medical records of 206 patients with type 1 diabetes (n = 39), type 2 diabetes (n = 37), and gestational diabetes (GDM, n = 130) at the Massachusetts General Hospital were identified. Placental pathology reports were reviewed to determine prevalence of IVT. Gestational and maternal age-matched controls were selected from the pathology archives consisting of placentas examined only for the indication of group B streptococcus screen positivity; controls were confirmed euglycemic and reviewed for IVT. Fisher exact test was used for statistical analysis. An increased incidence of IVT was present in all diabetics (type 1, type 2, and GDM; 32 of 206; 15.5%; P = 0.04) and GDM exclusively (22 of 130; 16.9%; P = 0.03) versus controls (7 of 99; 7.1%). IVT were also increased in patients with type 1 diabetes (4 of 39; 10.3%) and type 2 diabetes (6 of 37; 16.2%) compared to controls (7 of 99; 7.1%), but the results did not attain statistical significance (P = 0.73 and 0.19, respectively). The incidence of IVT was increased in the placentas of patients with diabetes as a group (type 1, type 2, and GDM), and in patients with GDM in particular. This is the first report of an association between diabetes and an increased incidence of placental IVT.

Small Molecule, Big Prospects: MicroRNA in Pregnancy and Its Complications

MicroRNAs are small, noncoding RNA molecules that regulate target gene expression in the posttranscriptional level. Unlike siRNA, microRNAs are "fine-tuners" rather than "switches" in the regulation of gene expression; thus they play key roles in maintaining tissue homeostasis. The aberrant microRNA expression is implicated in the disease process. To date, numerous studies have demonstrated the regulatory roles of microRNAs in various pathophysiological conditions. In contrast, the study of microRNA in pregnancy and its associated complications, such as preeclampsia (PE), fetal growth restriction (FGR), and preterm labor, is a young field. Over the last decade, the knowledge of pregnancy-related microRNAs has increased and the molecular mechanisms by which microRNAs regulate pregnancy or its associated complications are emerging. In this review, we focus on the recent advances in the research of pregnancy-related microRNAs, especially their function in pregnancy-associated complications and the potential clinical applications. Here microRNAs that associate with pregnancy are classified as placenta-specific, placenta-associated, placenta-derived circulating, and uterine microRNA according to their localization and origin. MicroRNAs offer a great potential for developing diagnostic and therapeutic targets in pregnancy-related disorders.

Role of Exosomes in Placental Homeostasis and Pregnancy Disorders

The human placenta is a unique organ that performs the function of the majority of fetal organs across gestation. How the placenta communicates with maternal tissues to prepare them for pregnancy is not fully understood. Recently, it has been established that placental cells can communicate with maternal tissues to regulate their biological function via extracellular vesicles (EVs). EVs are subclassified into exosomes or microvesicles (MVs) according to their size, cell or tissue of origin, functions, and physical features. Exosomes are a specific type of EVs from an endocytic origin, while MVs are released via budding from the plasma membrane. With regards to pregnancy, the role of EVs has been described in several functions such as immune responses and maternal metabolic adaptation to gestation. Interestingly, EVs of placental origin can be detected in a variety of body fluids including urine and blood, and have been identified in the maternal circulation at as early as 6 weeks of gestation. Moreover, the number of exosomes across gestation is higher in complications of pregnancies such as preeclampsia and gestational diabetes mellitus compared to normal pregnancies. Circulating exosomes contains proteins and RNAs that are representative of the cell of origin, including surface and cytoplasmic protein, messenger RNA, and micro-RNAs. Finally, exosomes are capable of transferring their contents to other cells and regulating the biological function of the target cell. In this review, we will discuss the effect of the maternal microenvironment on secretion and content of placenta-derived EVs, and how this may lead to complications of pregnancies with a special emphasis on exosomes.

HLA-G expression is regulated by miR-365 in trophoblasts under hypoxic conditions

INTRODUCTION

Hypoxia occurs in the first trimester of placental development and is implicated in the regulation of trophoblast differentiation. Prolonged hypoxic conditions in the placenta are related to the development of preeclampsia. MicroRNAs (miRNAs) are noncoding, single-stranded RNAs that modulate gene expression by targeting messenger RNA. We hypothesized that, under hypoxic conditions, trophoblasts may have a unique miRNA profile that may play a critical role in placental development.

METHODS

Total RNA was extracted from human trophoblast, HChEpC1b, exposed to normoxia (20% O2) or hypoxia (2% O2) for 24 h, and the miRNA expression profiles were investigated using a microRNA array. Several differential miRNAs were selected and validated using real-time reverse transcription PCR. We identified potential targets of these miRNAs using in silico analysis. We confirmed a potential target protein by western blot analysis and luciferase assays.

RESULTS

The expression of miR-365 was significantly upregulated under hypoxic conditions. In silico analysis showed that miR-365 targeted human leukocyte antigen (HLA)-G. Both hypoxic conditions and overexpression of miR-365 inhibited the expression of HLA-G proteins. The overexpression of miR-365 also decreased the activity of the luciferase reporter containing the 3'-untranslated region (UTR) of HLA-G with the predicted miR-365-binding site.

DISCUSSION

HLA-G is a non-classical HLA class-Ib molecule that is expressed mainly in extravillous trophoblasts and which plays a key role in maintaining immune tolerance at the maternal-fetal interface. Our results indicate that miR-365 targets the HLA-G 3' UTR to repress its expression. The expression of miR-365 may play an important role in human placental development and in immunoprotection of the semiallogenic embryo.

Molecular mechanisms of maternal vascular dysfunction in preeclampsia

In preeclampsia, as a heterogeneous syndrome, multiple pathways have been proposed for both the causal as well as the perpetuating factors leading to maternal vascular dysfunction. Postulated mechanisms include imbalance in the bioavailability and activity of endothelium-derived contracting and relaxing factors and oxidative stress. Studies have shown that placenta-derived factors [antiangiogenic factors, microparticles (MPs), cell-free nucleic acids] are released into the maternal circulation and act on the vascular wall to modify the secretory capacity of endothelial cells and alter the responsiveness of vascular smooth muscle cells to constricting and relaxing stimuli. These molecules signal their deleterious effects on the maternal vascular wall via pathways that provide the molecular basis for novel and effective therapeutic interventions.

Chorioamnionitis (ChA) modifies CX3CL1 (fractalkine) production by human amniotic epithelial cells (HAEC) under normoxic and hypoxic conditions

Background

Chemokine CX3CL1 possesses unique properties, including combined adhesive and chemotactic functions. Human amniotic epithelial cells (HAEC) show expression of CX3CL1 receptor (CX3CR1) and produce CX3CL1 in response to both physiologic and pathologic stimuli. Chorioamnionitis (ChA) is a common complication of pregnancy and labour. ChA is often accompanied by local hypoxia because of the high oxygen consumption at the site of inflammation. We examined comparatively (ChA-complicated vs. normal pregnancy) CX3CR1 expression and the effects of hypoxia, lipopolysaccharide (LPS), and CX3CR1 blockade on CX3CL1 production in HAEC cultured in vitro.

Methods

HAEC have been isolated using trypsinization, and cultured under normoxia (20% O₂) vs. hypoxia (5% O₂). According to the experimental design, LPS (1 μg/ml) and neutralizing anti-CX3CR1 antibodies were added at respective time points. Mean CX3CL1 concentration in the supernatant samples were determined by ELISA. Expression of immunostained CX3CR1 was analyzed using quantitative morphometry.

Results

We have found that the mean levels of CX3CL1 and CX3CR1 expression were remarkably (p < 0.05) higher in ChA, compared to normal pregnancy. Significantly increased expression of CX3CR1 was observed in ChA during both normoxia and hypoxia. Hypoxia exposure produced decrease in the mean concentration of CX3CL1 in both groups, however this reduction was stronger in normal pregnancy. In normoxia, LPS-evoked rise in the mean concentration of CX3CL1 was higher (p < 0.05) in normal pregnancy. This response was positively correlated with CX3CR1 expression. Blockade of CX3CR1 canceled the secretory response to LPS in all groups.

Conclusions

ChA-complicated pregnancy up-regulates CX3CR1 in HAEC cultured in vitro with simultaneous increase in CX3CL1 production. Hypoxia-resistant production of CX3CL1 may be responsible for ChA-related complications of pregnancy and labor.

CX3CL1 (fractalkine) and TNFα production by perfused human placental lobules under normoxic and hypoxic conditions in vitro: the importance of CX3CR1 signaling

Objective

Inflammation and hypoxia activate the fractalkine (CX3CL1) receptor (CX3CR1)-related signaling pathway. Tumor necrosis factor alpha (TNFα) induces CX3CL1, influencing a mechanism of CX3CL1 autoregulation by CX3CR1 expression. We compared spontaneous and lipopolysaccharide (LPS)-induced CX3CL1 and TNFα production by human placenta under normoxic vs. hypoxic conditions, with respect to CX3CR1 expression and its functional status.

Methods

Placental lobules of term placentae (N = 24) were perfused extracorporeally. CX3CL1 and TNFα concentrations were measured in the perfusion fluid by ELISA. LPS, anti-CX3CR1 antibodies and pirfenidone were used in respective subgroups. After perfusion, CX3CR1 expression was estimated in placental tissue using quantitative immunohistochemistry, and the final results were adjusted for the mean microvascular density.

Results

The highest increase in CX3CL1 concentration in response to LPS was observed in hypoxia (p < 0.05). Unlike in normoxia, anti-CX3CR1 administration in hypoxia significantly reduced the LPS-evoked response. CX3CR1 expression was augmented by hypoxia and reached 260.9 ± 41 (% ±SEM) of the reference value in normoxia. Positive immunostaining for CX3CR1 corresponded to the vascular endothelium. Pirfenidone inhibited hypoxia + LPS-related increase in TNFα production and prevented the up-regulation of CX3CR1.

Conclusion

The modulatory influence of TNFα on CX3CR1 expression in hypoxia and CX3CL1/CX3CR1 interaction may serve as a compensatory mechanism to preserve or augment the pro-inflammatory course of intercellular interactions in placental endothelium.

Fractalkine (CX3CL1) and its receptor CX3CR1 may contribute to increased angiogenesis in diabetic placenta

Chemokine CX3CL1 is unique, possessing the ability to act as a dual agent: chemoattractant and adhesive compound. Acting via its sole receptor CX3CR1, CX3CL1 participates in many processes in human placental tissue, including inflammation and angiogenesis. Strongly upregulated by hypoxia and/or inflammation-induced inflammatory cytokines secretion, CX3CL1 may act locally as a key angiogenic factor. Both clinical observations and histopathological studies of the diabetic placenta have confirmed an increased incidence of hypoxia and inflammatory reactions with defective angiogenesis. In this study we examined comparatively (diabetes class C complicated versus normal pregnancy) the correlation between CX3CL1 content in placental tissue, the mean CX3CR1 expression, and density of the network of placental microvessels. A sandwich enzyme immunoassay was applied for CX3CL1 measurement in placental tissue homogenates, whereas quantitative immunohistochemical techniques were used for the assessment of CX3CR1 expression and the microvascular density. Significant differences have been observed for all analyzed parameters between the groups. The mean concentration of CX3CL1 in diabetes was increased and accompanied by augmented placental microvessel density as well as a higher expression of CX3CR1. In conclusion, we suggest involvement of CX3CL1/CX3CR1 signaling pathway in the pathomechanism of placental microvasculature remodeling in diabetes class C.

Matrix metalloproteinases: inflammatory regulators of cell behaviors in vascular formation and remodeling

Abnormal angiogenesis and vascular remodeling contribute to pathogenesis of a number of disorders such as tumor, arthritis, atherosclerosis, restenosis, hypertension, and neurodegeneration. During angiogenesis and vascular remodeling, behaviors of stem/progenitor cells, endothelial cells (ECs), and vascular smooth muscle cells (VSMCs) and its interaction with extracellular matrix (ECM) play a critical role in the processes. Matrix metalloproteinases (MMPs), well-known inflammatory mediators are a family of zinc-dependent proteolytic enzymes that degrade various components of ECM and non-ECM molecules mediating tissue remodeling in both physiological and pathological processes. MMPs including MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-12, and MT1-MMP, are stimulated and activated by various stimuli in vascular tissues. Once activated, MMPs degrade ECM proteins or other related signal molecules to promote recruitment of stem/progenitor cells and facilitate migration and invasion of ECs and VSMCs. Moreover, vascular cell proliferation and apoptosis can also be regulated by MMPs via proteolytically cleaving and modulating bioactive molecules and relevant signaling pathways. Regarding the importance of vascular cells in abnormal angiogenesis and vascular remodeling, regulation of vascular cell behaviors through modulating expression and activation of MMPs shows therapeutic potential.

Placental regulation of maternal-fetal interactions and brain development

A variety prenatal insults are associated with the incidence of neurodevelopmental disorders such as schizophrenia, autism and cerebral palsy. While the precise mechanisms underlying how transient gestational challenges can lead to later life dysfunctions are largely unknown, the placenta is likely to play a key role. The literal interface between maternal and fetal cells resides in the placenta, and disruptions to the maternal or intrauterine environment are necessarily conveyed to the developing embryo via the placenta. Placental cells bear the responsibility of promoting maternal tolerance of the semiallogeneic fetus and regulating selective permeability of nutrients, gases, and antibodies, while still providing physiological protection of the embryo from adversity. The placenta's critical role in modulating immune protection and the availability of nutrients and endocrine factors to the offspring implicates its involvement in autoimmunity, growth restriction and hypoxia, all factors associated with the development of neurological complications. In this review, we summarize primary maternal-fetal interactions that occur in the placenta and describe pathways by which maternal insults can impair these processes and disrupt fetal brain development. We also review emerging evidence for placental dysfunction in the prenatal programming of neurodevelopmental disorders.

Ascorbate prevents placental oxidative stress and enhances birth weight in hypoxic pregnancy in rats

This study isolated the effects of maternal hypoxia independent of changes in maternal nutrition on maternal circulatory and placental molecular indices of oxidative stress and determined whether maternal antioxidant treatment conferred protection. Pregnant rats were subjected to normoxic pregnancy or 13% O2 chronic hypoxia for most of gestation with and without maternal treatment with vitamin C in the drinking water. Maternal hypoxia with and without vitamin C did not affect maternal food or water intake and led to a significant increase in maternal and fetal haematocrit. At gestational day 20, maternal plasma urate and L-cysteine concentrations, and placental levels of 4-hydroxynonenal and heat shock protein 70 were increased while placental heat shock protein 90 levels were decreased in hypoxic pregnancy. The induction of maternal circulatory and placental molecular indices of oxidative stress in hypoxic pregnancies was prevented by maternal treatment with vitamin C. Maternal hypoxia during pregnancy with or without vitamin C increased placental weight, but not total or compartmental volumes. Maternal treatment with vitamin C increased birth weight in both hypoxic and normoxic pregnancies. The data show that maternal hypoxia independent of maternal undernutrition promotes maternal and placental indices of oxidative stress, effects that can be prevented by maternal treatment with vitamin C in hypoxic pregnancy. While vitamin C may not be the ideal candidate of choice for therapy in pregnant women, and taking into consideration differences in ascorbic acid metabolism between rats and humans, the data do underlie that antioxidant treatment may provide a useful intervention to improve placental function and protect fetal growth in pregnancy complicated by fetal hypoxia.

Developmental programming of cardiovascular dysfunction by prenatal hypoxia and oxidative stress

Fetal hypoxia is a common complication of pregnancy. It has been shown to programme cardiac and endothelial dysfunction in the offspring in adult life. However, the mechanisms via which this occurs remain elusive, precluding the identification of potential therapy. Using an integrative approach at the isolated organ, cellular and molecular levels, we tested the hypothesis that oxidative stress in the fetal heart and vasculature underlies the molecular basis via which prenatal hypoxia programmes cardiovascular dysfunction in later life. In a longitudinal study, the effects of maternal treatment of hypoxic (13% O(2)) pregnancy with an antioxidant on the cardiovascular system of the offspring at the end of gestation and at adulthood were studied. On day 6 of pregnancy, rats (n = 20 per group) were exposed to normoxia or hypoxia ± vitamin C. At gestational day 20, tissues were collected from 1 male fetus per litter per group (n = 10). The remaining 10 litters per group were allowed to deliver. At 4 months, tissues from 1 male adult offspring per litter per group were either perfusion fixed, frozen, or dissected for isolated organ preparations. In the fetus, hypoxic pregnancy promoted aortic thickening with enhanced nitrotyrosine staining and an increase in cardiac HSP70 expression. By adulthood, offspring of hypoxic pregnancy had markedly impaired NO-dependent relaxation in femoral resistance arteries, and increased myocardial contractility with sympathetic dominance. Maternal vitamin C prevented these effects in fetal and adult offspring of hypoxic pregnancy. The data offer insight to mechanism and thereby possible targets for intervention against developmental origins of cardiac and peripheral vascular dysfunction in offspring of risky pregnancy.

Morphological and functional alterations in the aorta of the chronically hypoxic fetal rat

In human pregnancy, reduced placental perfusion has been associated with fetal aortic thickening. However, the relative contributions of fetal undernutrition versus fetal underoxygenation to triggering alterations in fetal cardiovascular development remain uncertain. Here, we isolate the effects of chronic fetal hypoxia on fetal cardiovascular development in a specific rodent model of chronic fetal hypoxia independent of changes in nutrition during pregnancy. Pregnant rats were housed under normoxic (21% O(2)) or hypoxic (13% O(2)) conditions from day 6 to day 20 of gestation. At day 20, pups and placentas were weighed. Fetal thoraces were fixed for quantitative histological analysis of the aorta. In a separate group, fetal aortic reactivity was assessed via in vitro wire myography. The experiments controlled for sex and within-litter variation. Placental weight was increased and fetal weight maintained in hypoxic pregnancy. Hypoxic pregnancy led to a 176% increment in wall thickness and a 170% increment in the wall-to-lumen area ratio of the fetal aorta. Fetal aortic vascular reactivity was markedly impaired, showing reduced constrictor and relaxant responsiveness in hypoxic pregnancy. Chronic developmental hypoxia independent of changes in nutrition has profound effects on the morphology and function of the fetal aorta in a mammalian species.

Fetal hypoxia and programming of matrix metalloproteinases

Fetal hypoxia adversely affects the brain and heart development, yet the mechanisms responsible remain elusive. Recent studies indicate an important role of the extracellular matrix in fetal development and tissue remodeling. The matrix metalloproteinases (MMPs) and their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs) have been implicated in a variety of physiological and pathological processes in the cardiovascular and central nervous systems. This review summarizes current knowledge of the mechanisms by which fetal hypoxia induces the imbalance of MMPs, TIMPs and collagen expression patterns, resulting in growth restriction and aberrant tissue remodeling in the developing heart and brain. Collectively, this information could lead to the development of preventive diagnoses and therapeutic strategies in the fetal programming of cardiovascular and neurological disorders.

Epigenetic regulation of matrix metalloproteinases and their collagen substrates in cancer

Our review covers the recent epigenetic data that are focused on matrix metalloproteinases (MMPs), their inhibitors (tissue inhibitors of MMPs; TIMPs) and collagen substrates. Twenty-four MMPs, four TIMPs and at least 28 collagen types are known in humans. The MMP activity regulates the functionality of multiple extracellular matrix proteins, cytokines, growth factors and cell signaling and adhesion receptors. Aberrantly enhanced MMP proteolysis affects multiple cell functions, including proliferation, migration and invasion. This aberrant MMP proteolysis is frequently recorded in cancer. Recent evidence, however, indicates that several MMPs function as tumor suppressors in cancer. Their inhibition could have pro-tumorigenic effects (making them anti-targets), counterbalancing the benefits of target inhibition and leading to adverse effects in cancer patients. The current epigenetic data suggest that there are distinct multi-layered epigenetic mechanisms that regulate MMPs, TIMPs and collagens. We show that in certain cancer types, epigenetic signatures of selected MMPs exhibit stem cell-like characteristics. Epigenetic mechanisms appear to play an especially important role in glioblastoma multiforme. Glioblastomas/gliomas synthesize de novo and then deposit collagens into the brain parenchyma. The collagen deposition, combined with an enhanced MMP activity in glioblastomas/gliomas, facilitates rapid invasion of tumor cells through the brain. It is tempting to hypothesize that the epigenetic mechanisms which control MMPs, TIMPs and collagens and, consequently, tumor cell invasion, represent promising drug targets and that in the near future these targets will be challenged pharmacologically.

Regulation of the matricellular proteins CYR61 (CCN1) and NOV (CCN3) by hypoxia-inducible factor-1{alpha} and transforming-growth factor-{beta}3 in the human trophoblast

It is known that a hypoxic environment is critical for trophoblast migration and invasion and is fundamental for appropriate placental perfusion. Because cysteine-rich 61 (CYR61, CCN1) and nephroblastoma overexpressed (NOV, CCN3) are expressed in the extravillous trophoblast and expression levels are deregulated in preeclampsia, we investigated their regulation properties in first-trimester placental explants and in JEG3 choriocarcinoma cells upon a physiological low oxygen tension of 1-3%. In placental explants, both proteins were expressed in the extravillous trophoblast cells and were increased upon hypoxia. JEG3 cells revealed a significant up-regulation of CYR61 and NOV intracellular as well as secreted protein upon hypoxic treatment accompanied by the stabilization of the hypoxia-inducible factor-1alpha (HIF-1alpha). Treatment with dimethyloxalylglycine to mimic hypoxia and silencing of HIF-1alpha using small interfering RNA revealed that only the increase in intracellular protein expression seems to be dependent on HIF-1alpha but obviously not the secretion process. Moreover, recombinant TGF-beta3 was able to further enhance the amount of intracellular CCN proteins as well as secreted CYR61 levels under hypoxia. These results indicate that low oxygen levels trigger elevation of intracellular as well as secreted CYR61 and NOV protein probably in two independent pathways. Addition of recombinant CYR61 and NOV proteins increases migration as well as invasion properties of JEG3 trophoblast cells, which strengthen their role in supporting trophoblast migration invasion properties. In summary, CYR61 and NOV are regulated by HIF-1alpha and TGF-beta3 in the trophoblast cell line JEG3, and their enhanced secretion could be implicated in appropriate placental invasion.

MiR-205 silences MED1 in hypoxic primary human trophoblasts

Acting through degradation of target mRNA or inhibition of translation, microRNAs (miRNAs) regulate development, differentiation, and cellular response to diverse cues. We analyzed changes in miRNA expression in human placental trophoblasts exposed to hypoxia, which may result from hypoperfusion and placental injury. Using an miRNA microarray screen, confirmed by Northern blot analysis, we defined a set of seven miRNAs (miR-93, miR-205, miR-224, miR-335, miR-424, miR-451, and miR-491) that are differentially regulated in primary trophoblasts exposed to hypoxia. We combined in silico prediction of miRNA targets with gene expression profiling data to identify a series of potential targets for the miRNAs, which were further analyzed using luciferase reporter assays. Among experimentally confirmed targets, we found that the transcriptional coactivator MED1, which plays an important role in placental development, is a target for miR-205. Using gain- and loss-of-function assays, we confirmed that miR-205 interacts with a specific target in the 3'-UTR sequence of MED1 and silences MED1 expression in human trophoblasts exposed to hypoxia, suggesting that miR-205 plays a role in trophoblast injury.

Trophoblast-mediated spiral artery remodelling: a role for apoptosis

In the first 20 weeks of pregnancy a number of important changes take place in the maternal uterine vasculature. Vascular endothelial and smooth muscle cells are lost from the spiral arteries and are replaced by fetal trophoblast cells. The resulting increase in blood flow to the intervillous space ensures that the fetus receives the nutrients and respiratory gases required for growth. Failure of the vessels to remodel sufficiently is a common feature of pregnancy pathologies such as early pregnancy loss, intrauterine growth restriction and pre-eclampsia. Although there is evidence to suggest that some vascular changes occur prior to trophoblast invasion, it is clear that in the absence of trophoblast invasion the remodelling of the spiral arteries is reduced. The cellular and molecular mechanisms by which trophoblasts influence vessel structure have been little studied. Trophoblasts synthesize and release a plethora of cytokines and growth factors including members of the tumour necrosis factor family such as tumour necrosis factor alpha, Fas-ligand and tumour necrosis factor-related apoptosis-inducing ligand. Recent studies suggest that these factors may be important in regulating the remodelling process by inducing both endothelial cell and vascular smooth muscle cell apoptosis.

Three-dimensional context regulation of metastasis

Tumor progression ensues within a three-dimensional microenvironment that consists of cellular and non-cellular components. The extracellular matrix (ECM) and hypoxia are two non-cellular components that potently influence metastasis. ECM remodeling and collagen cross-linking stiffen the tissue stroma to promote transformation, tumor growth, motility and invasion, enhance cancer cell survival, enable metastatic dissemination, and facilitate the establishment of tumor cells at distant sites. Matrix degradation can additionally promote malignant progression and metastasis. Tumor hypoxia is functionally linked to altered stromal-epithelial interactions. Hypoxia additionally induces the expression of pro-migratory, survival and invasion genes, and up-regulates expression of ECM components and modifying enzymes, to enhance tumor progression and metastasis. Synergistic interactions between matrix remodeling and tumor hypoxia influence common mechanisms that maximize tumor progression and cooperate to drive metastasis. Thus, clarifying the molecular pathways by which ECM remodeling and tumor hypoxia intersect to promote tumor progression should identify novel therapeutic targets.