Placental Explant Cultures Research Articles

Effect of Carbon Monoxide on Bacteria‐Stimulated Cytokine Production by Placental Explants

Preterm birth is frequently caused by an inflammatory response to ascending infections of the reproductive tract. Carbon monoxide (CO) has potent anti-inflammatory properties at subtoxic concentrations. Whether or not CO can modulate inflammatory responses by placental tissues is unclear. Placental explant cultures were incubated with heat-killed Escherichia coli or Ureaplasma parvum in the presence or absence of 250ppm CO for 24hr. Concentrations of cytokines relative viability of the cultures were quantified. Escherichia coli- and U.parvum-stimulated IL-1β production was significantly inhibited by CO supplementation. Escherichia coli-stimulated, but not U.parvum-stimulated, IFN-γ production was inhibited by CO. While CO inhibited PGE(2) production by unstimulated cells, no effects on bacteria-stimulated prostaglandin production were detected. CO had no effect on basal or E.coli-stimulated TNF-α production but enhanced TNF-α production by cultures stimulated with U.parvum. In addition, CO tended to improve the viability of the placental cultures. Low concentrations of CO tended to reduce proinflammatory cytokines and to promote the production of anti-inflammatory cytokines in a pathogen-specific manner. These properties suggest that CO may be useful for promoting a pro-pregnancy cytokine milieu by placental explants and may reduce the consequences of intrauterine infections.

Decreased Lectin-Like Oxidized LDL Receptor 1 (LOX-1) and Low Nrf2 Activation in Placenta Are Involved in Preeclampsia

Serum concentration of oxidized low-density lipoprotein (oxLDL) is higher in women with preeclampsia than in normal pregnant woman. Lectin-like oxLDL receptor-1 (LOX-1) is one of the scavenger receptors for oxLDL and is abundantly expressed in placenta. It is well known that oxLDL activates nuclear factor erythroid 2-related factor 2 (Nrf2), a master regulator of antioxidant and cytoprotective genes such as heme oxygenase-1 (HO-1), which play an important role in preeclampsia. However, it has yet to be elucidated whether LOX-1, along with Nrf2, participates in the pathology of preeclampsia. The objective of the study was to assess LOX-1 expression and Nrf2 activation in preeclamptic placentas and to manifest their physiological roles in preeclampsia. Expression and regulation of LOX-1, HO-1, and Nrf2 were evaluated by real-time quantitative RT-PCR and Western blotting. The functions of LOX-1 and Nrf2 were examined using an anti-LOX-1 antibody and Nrf2 activator in JAR, a choriocarcinoma cell line, and placental explants. Both LOX-1 expression and Nrf2 activation were significantly decreased in preeclamptic placentas compared with normal controls. A significant decrease in LOX-1 mRNA was found in placental explant cultures under hypoxic conditions. Activation of Nrf2 up-regulated HO-1 in both the JAR cells and placental explants. Furthermore, oxLDL increased HO-1 mRNA, whereas the blockade of LOX-1 inhibited the increase of HO-1 mRNA in JAR cells. Decreasing LOX-1 expression in preeclamptic placenta may contribute to high oxLDL concentration, low Nrf2 activation, and low HO-1 expression. These findings provide novel insights into the crucial role of LOX-1 and Nrf2 in the pathogenesis of preeclampsia.

The effect of coelomic fluid on the production of cytokines by the first trimester human placenta

ObjectiveTo investigate the modulatory effects of coelomic fluid (CF) on the production of tumour necrosis factor-alpha (TNFα) and its receptors, TNF-R1 and TNF-R2, interferon gamma (IFNγ) and interleukin (IL)-10 by placental villous explants cultured under physiological oxygen (O2) concentration. Study designIn vitro culture of placental villous explants at atmospheric and physiological (6%) O2 levels at varying concentrations of CF. Main outcome measuresConcentration of TNFα, TNF-R1, TNF-R2, IFNγ and IL-10 in culture medium and villous explant homogenates, measured using flowcytometric bead arrays. ResultsThe median level and interquartile range of cytokines and receptors present in CF were: TNFα 0.9 pg/ml (0.85, 0.95); IFNγ 5.38 pg/ml (4.96, 6.18); IL-10 1.59 pg/ml (1.45, 1.76); TNF-R1 6043.65 pg/ml (5961.39, 6187.35) and TNF-R2 3563.52 pg/ml (3390.26, 3635.19). The PO2 of CF was 48.74 mmHg (SEM 1.59), equivalent to 6% O2.Increasing doses of CF significantly (p < 0.05) increased the levels of TNFα, TNF-R1 and TNF-R2 in the culture medium at both O2 concentrations.TNF-R1 levels measured in placental homogenate increased up to 2-fold at both O2 concentrations, but were significantly lower (1.96 fold; p = 0.03) at 6% O2 compared to 20% O2. ConclusionsThe exocoelomic cavity in humans contains high levels of both soluble TNF-R1 and TNF-R2. The addition of CF to placental tissue explants in culture modulates the placental secretion of TNFα-receptors and TNFα at both physiological and atmospheric O2 tension resulting in a concentration much higher than that found in the CF. This may contribute to the maternal inflammatory response previously reported in normal early pregnancy.

Bile Acid Signaling in Fetal Tissues: Implications for Intrahepatic Cholestasis of Pregnancy

Background/Aims: Intrahepatic cholestasis of pregnancy (ICP) is complicated by spontaneous preterm labor, fetal anoxia and unexplained fetal death. We aim to evaluate the mechanisms by which raised fetal bile acids cause placental abnormalities and fetal cardiac pathology. Methods: The study was performed using placental samples taken from ICP pregnancies, placental explant culture, neonatal and adult cardiomyocytes, and murine and human embryonic stem cell-derived cardiomyocytes. Results: Maternal cholestasis causes a placental phenotype with histological abnormalities. This can be evaluated using placental explant cultures. Taurocholate, the principal bile acid raised in the fetal compartment in ICP, causes abnormal cardiomyocyte contraction, rhythm and desynchronization of calcium dynamics. To extend our observations that the muscarinic M2 receptor plays a role in bile acid-induced arrhythmia in cardiomyocytes, we are developing a model containing mixed cell populations to represent the fetal and maternal hearts. This will be used to evaluate the underlying mechanisms to explain fetal arrhythmia in the presence of cholestasis. Conclusion: Bile acids signal via a spectrum of pathways in the placenta and the fetal heart.

Application of Human Placental Villous Tissue Explants to Study ABC Transporter Mediated Efflux of 2,4-Dinitrophenyl-S-Glutathione

The purpose of this study was to characterize the human term placental villous tissue explant culture model as a tool to study the formation and efflux of 1-chloro-2,4-dinitrobenzene (CDNB) conjugate 2,4-dinitrophenyl-S-glutathione (DNP-SG) as a model system for phase II metabolism and ATP-binding cassette (ABC) transporter-mediated cellular efflux. Placental tissue samples were obtained after cesarean section following normal pregnancies (n=9). Cultured villous tissue was monitored up to 48 h to study the effect of time in culture on biochemical parameters, formation and efflux of DNP-SG in the absence or presence of ATPase inhibitor sodium orthovanadate and the protein expression of ABC transporters - multidrug resistance associated protein 2 (MRP2), P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and enzyme glutathione-S-transferase isoform P1-1 (GSTP1-1). Villous tissue structure, tissue viability and expression of BCRP, GSTP1-1 remained unchanged, while expression of MRP2, P-gp and total tissue glutathione decreased with time in culture. Tissue integrity was unchanged up to 24 h but declined at 48 h. However, DNP-SG formation, DNP-SG efflux, and the extent of inhibition of DNP-SG efflux by sodium orthovanadate showed only minor changes through 48 h. Sodium orthovanadate decreased DNP-SG efflux, consistent with inhibition of apical ABC transporters. The results support the use of the cultured human term placental villous tissue explants model to study coordinated function of GSTP1-1 and apical ABC transporters in the formation and efflux of the model substrate DNP-SG.

Can Oxygen Tension Contribute to an Abnormal Placental Cytokine Milieu?

OBJECTIVE The aim of this study was to determine whether culturing human placental explants under different oxygen tensions will alter expression of pro- and anti-inflammatory mediators. METHODS Placental explant cultures from second-trimester, elective, terminations-of-pregnancy were incubated under 21, 5, or 1% O(2) concentrations for 24 hr in the presence or absence of IL-10. Cytokine concentrations in the conditioned medium were quantified by immunoassay. RESULTS Culture of placental explants under 21, 5, or 1% O(2) concentrations produced hyperoxic (143 ± 1.6 mmHg), normoxic (37 ± 1.6 mmHg), and hypoxic (18.2 ± 1.6 mmHg) pO(2) levels for the maternal-fetal interface in the medium. Oxygen tension had profound effects on basal placental cytokine levels as well as on IL-10-stimulated cytokine production. IL-1β and TNF-α, but not IFN-γ production, was reduced by 21% O(2) . Moreover, 21% O(2) levels increased the anti-inflammatory cytokines IL-10 and IL-13 while 1% O(2) tended to decrease the production of these cytokines. CONCLUSIONS Five percent- O(2) incubation more accurately represents in vivo pO(2) conditions at the maternal-fetal interface. Routine culture of placental explants in room air produces a superphysiologic oxygen tension that tended to increase the production of anti-inflammatory and decrease the production of pro-inflammatory cytokines. In addition, low pO(2) may reduce responsiveness of the placenta to the anti-inflammatory actions of IL-10.

Nodal Signals through Activin Receptor-Like Kinase 7 to Inhibit Trophoblast Migration and Invasion: Implication in the Pathogenesis of Preeclampsia

Trophoblast cell invasion into the uterus is an essential process for successful pregnancy, and shallow invasion of trophoblasts into the maternal decidua is linked to preeclampsia. We have reported that Nodal, a member of the transforming growth factor-β superfamily, acts through activin receptor-like kinase 7 (ALK7) to inhibit trophoblast proliferation and to induce apoptosis. In this study, we examined the spatial and temporal expression patterns of Nodal and ALK7 in human placenta from normal and preeclamptic pregnancies and investigated whether Nodal regulated trophoblast migration and invasion. Nodal and ALK7 were detected in villous and extravillous trophoblast cell populations in early gestation, and their levels were strongly up-regulated in preeclamptic placenta. Overexpression of Nodal or constitutively active ALK7 decreased cell migration and invasion, whereas knockdown of Nodal and ALK7 had the opposite effects. In placental explant culture, treatment with Nodal inhibited trophoblast outgrowth, whereas Nodal small-interfering RNA strongly induced the expansion of explants and the migration of extravillous trophoblast cells. Nodal stimulated the secretion of tissue inhibitor of metalloproteinase-1 and inhibited matrix metalloproteinase (MMP)-2 and MMP-9 activity. These findings suggest that the Nodal/ALK7 pathway plays important roles in human placentation and that its abnormal signaling may contribute to the development of preeclampsia.

M14.5 Characterisation of high temperature requirement factor A 3 (HtrA3) in endometrial and placental lysates using isoform specific monoclonal antibodies

Pregnant women who develop preeclampsia exhibit higher circulating levels of the soluble VEGF receptor-1 (sFlt-1). Recent findings suggest that soluble Flt-1 may contribute to the pathogenesis of preeclampsia by binding and neutralizing vascular endothelial growth factors (VEGF) and placental growth factor (PlGF). Existing literature identifies sFlt-1 as a 100 kDa glycoprotein, a product of an mRNA splice variant. We hypothesized that sFlt-1 expression may be more complex with multiple variants of sFlt-1 as well as multiple sources during normal pregnancy and preeclampsia. Using a combination of affinity purification of sFlt-1 by heparin-agarose and epitope specific antibodies, we performed Western blot analysis with epitope specific antibodies for sFlt-1. Plasma of preeclamptic women exhibits significantly higher amounts of a novel 145 kDa variant of sFlt-1, along with the 100 kDa isoform. We identified sFlt-1 variants in the conditioned medium from placental explant cultures that are hypoxia responsive with varying sizes, including 185, 145,100 and 60 kDa forms, as well as antigenicity. The 145 kDa was similar in antigenicity to the 100 kDa found in plasma whereas the 185 and 60 kDa sFlt-1 demonstrated different epitopes. Deglycosylation studies also confirm that there are multiple sFlt-1 polypeptides. Co-immunoprecipitation with VEGF suggests that these different sFlt isoforms can bind VEGF and therefore, may be of functional importance. Finally, comparison of sFlt-1 in the conditioned medium obtained from cultured cytotrophoblasts, peripheral blood mononuclear cells (PBMCs) and human uterine microvascular cells (HUtMVECs) exhibit mainly the100 kDa sFlt-1. Collectively these data suggest the presence of multiple isoforms of sFlt-1 in the circulation of women with preeclampsia as well as in uncomplicated pregnancies and the possibility of multiple sources. Placental hypoxia may contribute to sFlt-1 over expression but other regulatory mechanisms cannot be ruled out.

The Liver X Receptor (LXR) and its Target Gene ABCA1 are Regulated Upon Low Oxygen in Human Trophoblast Cells: A Reason for Alterations in Preeclampsia?

Objectives The Liver X receptors (LXR) alpha and beta and their target genes such as the ATP-binding cassette (ABC) transporters have been shown to be crucially involved in the regulation of cellular cholesterol homeostasis. The aim of this study was to characterize the role of LXR alpha/beta in the human placenta under normal physiological circumstances and in preeclampsia. Study design We investigated the expression pattern of the LXRs and their target genes in the human placenta during normal pregnancy and in preeclampsia. Placental explants and cell lines were studied under different oxygen levels and pharmacological LXR agonists. Main outcome measures Gene expressions (Taqman PCR) and protein levels (Western Blot) were combined with immunohistochemistry to analyze the expression of LXR and its target genes. Results In the human placenta, LXRA and LXRB expression increased during normal pregnancy. This was paralleled by the expression of their prototypical target genes, e.g., the cholesterol transporter ABCA1. Interestingly, early-onset preeclamptic placentae revealed a significant upregulation of ABCA1. Culture of JAr trophoblast cells and human first trimester placental explants under low oxygen lead to increased expression of LXRA and ABCA1 which was further enhanced by the LXR agonist T0901317. Conclusions LXRA together with ABCA1 are specifically expressed in the human placenta and can be regulated by hypoxia. Deregulation of this system in early preeclampsia might be the result of placental hypoxia and hence might have consequences for maternal-fetal cholesterol transport.

Changes in the Metabolic Footprint of Placental Explant-Conditioned Medium Cultured in Different Oxygen Tensions from Placentas of Small for Gestational Age and Normal Pregnancies

Being born small for gestational age (SGA) confers significantly increased risks of perinatal morbidity and mortality. Accumulating evidence suggests that an SGA fetus results from a poorly perfused and abnormally developed placenta. Some of the placental features seen in SGA, such as abnormal cell turnover and impaired nutrient transport, can be reproduced by culture of placental explants in hypoxic conditions. Metabolic footprinting offers a hypothesis-generating strategy to investigate factors absorbed by and released from this tissue in vitro. Previously, metabolic footprinting of the conditioned culture media has identified differences in placental explants cultured under normoxic and hypoxic conditions and between normal pregnancies and those complicated by pre-eclampsia. In this study we aimed to examine the differences in the metabolic footprint of placental villous explants cultured at different oxygen (O 2) tensions between women who deliver an SGA baby ( n = 9) and those from normal controls ( n = 8). Placental villous explants from cases and controls were cultured for 96 h in 1% (hypoxic), 6% (normoxic) and 20% (hyperoxic) O 2. Metabolic footprints were analysed by Ultra Performance Liquid Chromatography coupled to an electrospray hybrid LTQ-Orbitrap Mass Spectrometry (UPLC-MS). 574 metabolite features showed significant difference between SGA and normal at one or more of the oxygen tensions. SGA explant media cultured under hypoxic conditions was observed, on a univariate level, to exhibit the same metabolic signature as controls cultured under normoxic conditions in 49% of the metabolites of interest, suggesting that SGA tissue is acclimatised to hypoxic conditions in vivo. No such behaviour was observed under hyperoxic culture conditions. Glycerophospholipid and tryptophan metabolism were highlighted as areas of particular interest.

Amniotic Fluid Angiopoietin-1, Angiopoietin-2, and Soluble Receptor Tunica Interna Endothelial Cell Kinase-2 Levels and Regulation in Normal Pregnancy and Intraamniotic Inflammation-Induced Preterm Birth

Angiopoietin-1 (Ang-1) and Ang-2 act selectively on endothelial cells by engaging the Tunica interna endothelial cell kinase-2 (Tie2) receptor. A soluble form of Tie2 (sTie2) blocks angiopoietin bioactivity. The aim of the study was to characterize changes and expression patterns of Ang-1, Ang-2, and sTie2 in amniotic fluid (AF) and placenta during human pregnancy and intraamniotic inflammation (IAI)-induced preterm birth. We conducted a cross-sectional study at a tertiary university hospital. AF levels of Ang-1, Ang-2, and sTie2 were evaluated in 176 women during second trimester (n = 40), third trimester (n = 37), and preterm labor (positive IAI, n = 50; negative IAI, n = 49). Placenta and cord blood of select women were analyzed. Ang-1, Ang-2, sTie2, and IL-6 were evaluated by ELISA. Real-time PCR measured Ang-1, Ang-2, and Tie2 placental mRNA levels. Placenta was immunostained for Ang-1 and Ang-2. Placental explant cultures were stimulated with lipopolysaccharide, Pam3Cys, and modulators of protein synthesis/secretion (cycloheximide, monensin, and brefeldin A). In normal pregnancy, the levels and ratios of AF Ang-1, Ang-2, and sTie2 varied with gestational age (GA) (P < 0.001). PCR revealed corresponding changes in placental Ang-1 and Ang-2, but not Tie2, mRNA. IAI raised AF Ang-1, Ang-2, and sTie2 above the expected level for GA without affecting their placental mRNA. Ang-2 immunoreactivity appeared enhanced in areas of villous edema. AF Ang-2/Ang-1 ratio was an important determinant of cord blood IL-6 (P < 0.001). Ex-vivo, sTie2 release was increased by Golgi disrupting but not bacterial mimic agents. Ang-1, Ang-2, and sTie2 are physiological constituents of AF that are GA and IAI regulated. Ang-2/Ang-1 ratio may play a role in modulating the fetal inflammatory response to IAI. Placental sTie2 shedding likely involves a Golgi-mediated mechanism.

Placental transport and in vitro effects of Bisphenol A

Bisphenol A (BPA), an estrogen-like chemical, leaches from consumer products potentially causing human exposure. To examine the effects of BPA exposure during pregnancy, we performed studies using the BeWo trophoblast cell line, placental explant cultures, placental perfusions and skin diffusion models, all of human origin. Results showed BPA cytotoxicity in BeWo cells with an apparent EC50 at 100–125 μM. BPA exposure significantly increased β-hCG secretion and caspase-3 expression in placental explants at an environmentally relevant concentration of 1 nM. In the transport studies, a rapid transfer of BPA was observed across the term placentae and the BeWo cell monolayer. Further, transdermal transport of BPA was observed. These results indicate that fetal BPA exposure through placental exchange occurs with potential adverse implications for placental and fetal development. This battery of test systems within the realm of human implantation and fetal development represents important elements in risk assessment of reproductive toxicity.

Mst3 Plays an Important Role in Hypoxia‐induced placental Apoptosis in Preeclampsia

Preeclampsia, a disorder unique to humans, affects 5‐10% of all pregnancies, and remains a leading cause of fetal and maternal morbidity and mortality. A key histopathologic correlation is shallow invasion and aberrant remodeling of maternal spiral arteries, leading to decreased uteroplacental perfusion and hypoxia. In preeclampic human placenta, hypoxia is thought to be the main cause to elevate oxidative stress and induced trophoblast cell death. Recently, mammalian Ste20‐like protein kinase 3 (Mst3) was found to be elevated in human preeclampic placenta that exhibit extensive sign of apoptosis, suggesting the participation of Mst3 in preeclampsia. Hypoxia is postulated to induce the expression of Mst3 and the apoptosis of human placenta during preeclampsia. The role of Mst3 in hypoxia‐induced apoptosis was demonstrated in both human placental explant culture and the human trophoblast cell line 3A‐sub‐E. Further studies show that, in human trophoblast, hypoxia may induce the expression of Mst3 via oxidative stress and the activation of JNK. The activated Mst3 then triggers apoptosis of human trophoblasts by both caspase‐dependent and independent pathways. (The work was supported by National Science Council, ROC (Taiwan) under Contract No. NSC‐97‐2311‐B‐009‐001‐MY3)

Novel Soluble Flt-1 Isoforms in Plasma and Cultured Placental Explants from Normotensive Pregnant and Preeclamptic Women

Pregnant women who develop preeclampsia exhibit higher circulating levels of the soluble VEGF receptor-1 (sFlt-1). Recent findings suggest that soluble Flt-1 may contribute to the pathogenesis of preeclampsia by binding and neutralizing vascular endothelial growth factors (VEGF) and placental growth factor (PlGF). Existing literature identifies sFlt-1 as a 100 kDa glycoprotein, a product of an mRNA splice variant. We hypothesized that sFlt-1 expression may be more complex with multiple variants of sFlt-1 as well as multiple sources during normal pregnancy and preeclampsia. Using a combination of affinity purification of sFlt-1 by heparin-agarose and epitope specific antibodies, we performed Western blot analysis with epitope specific antibodies for sFlt-1. Plasma of preeclamptic women exhibits significantly higher amounts of a novel 145 kDa variant of sFlt-1, along with the 100 kDa isoform. We identified sFlt-1 variants in the conditioned medium from placental explant cultures that are hypoxia responsive with varying sizes, including 185, 145,100 and 60 kDa forms, as well as antigenicity. The 145 kDa was similar in antigenicity to the 100 kDa found in plasma whereas the 185 and 60 kDa sFlt-1 demonstrated different epitopes. Deglycosylation studies also confirm that there are multiple sFlt-1 polypeptides. Co-immunoprecipitation with VEGF suggests that these different sFlt isoforms can bind VEGF and therefore, may be of functional importance. Finally, comparison of sFlt-1 in the conditioned medium obtained from cultured cytotrophoblasts, peripheral blood mononuclear cells (PBMCs) and human uterine microvascular cells (HUtMVECs) exhibit mainly the100 kDa sFlt-1. Collectively these data suggest the presence of multiple isoforms of sFlt-1 in the circulation of women with preeclampsia as well as in uncomplicated pregnancies and the possibility of multiple sources. Placental hypoxia may contribute to sFlt-1 over expression but other regulatory mechanisms cannot be ruled out.

Early Gene Expression and Morphogenesis of the Murine Chorioallantoic Placenta In vivo and In vitro

Background In mice the exchange of oxygen and nutrients between mother and fetus occurs in the chorioallantoic placenta where fetal capillaries come in close proximity with maternal blood perfusing trophoblast-lined sinusoids. Despite its critical importance, quantitative in vivo gene expression over the initial stages of chorioallantoic placental development has not been described, nor are there in vitro systems recapitulating the critical syncytiotrophoblast differentiation step in its formation. Here we describe molecular events that occur during the onset of chorioallantoic morphogenesis in mice in vivo, and in placental explant and whole conceptus cultures in vitro. Results Chorioallantoic morphogenesis began immediately following allantoic fusion with the chorion in vivo, and was associated with significant upregulation of syncytiotrophoblast associated mRNA ( Gcm1 and Syncytin A). However mouse placentas with chorioallantoic point attachment cultured with the allantois or as whole conceptuses did not upregulate Gcm1 and/or Syncytin A, suggesting that syncytiotrophoblast differentiation did not occur in vitro. Failure of morphogenesis appeared to be due to failure to sustain in vitro the chorionic trophoblast cells from which the syncytiotrophoblast cells are derived. In vitro culture conditions did support the upregulation of ectoplacental cone marker Tpbpα, maintenance of giant cell marker Pl1, and maintenance of Fgfr2 expression; all of which mimicked in vivo events observed over this developmental interval. Conclusions We conclude that chorionic trophoblast maintenance and the early events that occur in vivo between chorioallantoic point attachment and primary villous formation are dependent on undefined intrauterine factors that were not present in the in vitro culture system. Nevertheless, in vitro culture conditions were appropriate to reproduce in vivo expression levels of Fgfr2, Pl1, and Tpbpα in placental explants.

Oxygen and the liberation of placental factors responsible for vascular compromise

Maternal endothelial activation in pre-eclampsia is attributed to the release of unknown factors from a hypoperfused placenta. To further characterize these factors, we have used a serum-free placental villous explant culture model and investigated the effect of the liberated soluble factors produced on human endothelial cell cultures. Term placental villous explants from uncomplicated pregnancies were cultured for 4 days in 20, 6 or 1% O2 to mimic placental hyperoxia, normoxia and hypoxia. Medium collected from viable explants was applied to cultured human uterine microvascular endothelial cells. Medium conditioned by hypoxic explants caused a significant decrease in endothelial cell ATP levels and mitochondrial dehydrogenase activity, suggestive of a reduced metabolic rate. An additional reduction in mitochondrial membrane potential and increased endothelial cell death occurred as the oxygen concentration to which explants had been exposed decreased. Effects of the hypoxic explant medium were also seen ex vivo in a wire myography model of myometrial artery function, with increased vasoconstriction and attenuated vasodilation following exposure to hypoxic explant medium. These results suggest that hypoxia (1% O2) may stimulate the release of soluble factors from the placenta, which have an adverse effect on endothelial cell metabolism and mitochondrial integrity in vitro. These potentially pathogenic factors are now being characterized.

Expression and protein localisation of IGF2in the marsupial placenta

BackgroundIn eutherian mammals, genomic imprinting is critical for normal placentation and embryo survival. Insulin-like growth factor 2 (IGF2) is imprinted in the placenta of both eutherians and marsupials, but its function, or that of any imprinted gene, has not been investigated in any marsupial. This study examines the role of IGF2 in the yolk sac placenta of the tammar wallaby, Macropus eugenii.ResultsIGF2 mRNA and protein were produced in the marsupial placenta. Both IGF2 receptors were present in the placenta, and presumably mediate IGF2 mitogenic actions. IGF2 mRNA levels were highest in the vascular region of the yolk sac placenta. IGF2 increased vascular endothelial growth factor expression in placental explant cultures, suggesting that IGF2 promotes vascularisation of the yolk sac.ConclusionThis is the first demonstration of a physiological role for any imprinted gene in marsupial placentation. The conserved imprinting of IGF2 in this marsupial and in all eutherian species so far investigated, but not in monotremes, suggests that imprinting of this gene may have originated in the placenta of the therian ancestor.

Angiotensin II mimics the hypoxic effect on regulating trophoblast proliferation and differentiation in human placental explant cultures

Regulation of cytotrophoblast differentiation toward extravillous trophoblasts (EVTs) is critical for establishing successful pregnancy. Previous studies have focused primarily on the factors promoting the differentiation, while inhibitory regulators except hypoxia have been less documented. In this study, to test our hypothesis that angiotensin II (Ang II) would inhibit EVT differentiation, we investigated the effects of Ang II on trophoblast outgrowth and the expression of molecules associated with the proliferation and invasion of trophoblasts using human first trimester villous explant cultures. Ang II increased EVT outgrowth and the number of cells in cell columns. Moreover, Ang II-treated explants exhibited increased Ki67 and integrin α5 immunoreactivity in EVTs as well as matrix metalloproteinase-2 activity in the conditioned media, and decreased α1 integrin immunoreactivity, which are compatible with the features of the proliferative phenotype EVTs. These effects of Ang II were similar to those of hypoxia (3% O 2). Ang II stimulated the expression of hypoxia inducible factor-1α at both mRNA and protein levels, and also enhanced the expression of plasminogen activator inhibitor-1 (PAI-1). Data presented herein suggest a possible role for Ang II in impairing trophoblast differentiation toward an invasive phenotype, which might be associated with shallow invasion in preeclamptic placentas.

Evidence for Interleukin‐10‐Mediated Inhibition of Cyclo‐ oxygenase‐2 Expression and Prostaglandin Production in Preterm Human Placenta

Interleukin-10 (IL-10) is thought to be a key cytokine for the maintenance of pregnancy. Here we examined the expression profiles of IL-10 and cyclo-oxygenase-2 (COX-2), and the effect of IL-10 on COX-2 expression and prostaglandin release in the human placenta from preterm labor deliveries associated with chorioamnionitis. Placental tissues from preterm labor and term labor deliveries were processed for ex vivo placental explant culture system. IL-10 expression was assessed by enzyme-linked immunosorbent assay (ELISA) and immunohistochemical (IHC) analysis. COX-2 expression was evaluated by IHC, Western blotting and reverse transcriptase-polymerase chain reaction. Prostaglandin E2 (PGE2) release was measured by ELISA. IL-10 was significantly reduced in chorioamnionitis-associated preterm labor as well as in term labor placental tissues compared with second trimester normal pregnancy samples obtained from elective terminations. Similar results were obtained with freshly isolated cytotrophoblasts from these deliveries. As expected, COX-2 mRNA was detected at significant levels in tissues from term and preterm labor deliveries compared with no labor term deliveries. Importantly, IL-10 inhibited COX-2 expression in cultured placental explants from preterm labor deliveries, but not from term labor samples. Inhibition of COX-2 expression coincided with reduced PGE2 release. These results demonstrate the importance of IL-10 in countering inflammation associated with preterm labor, and suggest that term and preterm parturition may, in part, represent different conditions.

Hypoxia Up-regulated Angiogenin and Down-regulated Vascular Cell Adhesion Molecule-i Expression and Secretion in Human Placental Trophoblasts

Many processes that are involved in cellular invasion, including blastocyst implantation, placental development, and rapidly growing tumors, occur in reduced oxygen environments. It has been surmised that oxygen tension could regulate the cytotrophoblast ability to differentiate and, as a consequence, to express proteins that are critical for placentation. The objective of the current investigation was therefore to test the hypothesis that placental tissues and trophoblast cells in culture, under low oxygen tension, release angiogenic factors that could affect vascular behavior and invasive potential, thus providing a link between abnormal placentation and maternal vascular abnormality. Functionally active term placental explant culture and trophoblast cultures were used to demonstrate the secretion profiles of angiogenin and vascular cell adhesion molecule-1 (VCAM-1), and the real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR) technique was employed to demonstrate the mRNA expression under both normoxic and hypoxic conditions. A significant increase in the secretion (P <.01) and mRNA expression (P <.01) of angiogenin and a significant decrease in the secretion (P <.04) and mRNA expression (P <.03) of VCAM-1 from both term placental explants and trophoblast cultures subjected to hypoxia in vitro were observed. Because the primary defect in uteroplacental insufficiency is placental maldevelopment probably associated with hypoxia in situ, this study provides molecular evidence to indicate that the differential expression and secretion of angiogenic factors may play an important role in these pathologic conditions.