The placenta is the interface between mother and fetus and inadequate function contributes to short and long-term ill-health. The placenta is absent from most large-scale RNA-Seq datasets. We ...therefore analyze long and small RNAs (~101 and 20 million reads per sample respectively) from 302 human placentas, including 94 cases of preeclampsia (PE) and 56 cases of fetal growth restriction (FGR). The placental transcriptome has the seventh lowest complexity of 50 human tissues: 271 genes account for 50% of all reads. We identify multiple circular RNAs and validate 6 of these by Sanger sequencing across the back-splice junction. Using large-scale mass spectrometry datasets, we find strong evidence of peptides produced by translation of two circular RNAs. We also identify novel piRNAs which are clustered on Chr1 and Chr14. PE and FGR are associated with multiple and overlapping differences in mRNA, lincRNA and circRNA but fewer consistent differences in small RNAs. Of the three protein coding genes differentially expressed in both PE and FGR, one encodes a secreted protein FSTL3 (follistatin-like 3). Elevated serum levels of FSTL3 in pregnant women are predictive of subsequent PE and FGR. To aid visualization of our placenta transcriptome data, we develop a web application ( https://www.obgyn.cam.ac.uk/placentome/ ).
Development of the human placenta is modulated heavily by the intrauterine environment. During the first trimester, development takes place in a low oxygen environment supported by histiotrophic ...nutrition from the endometrial glands. Consequently, the rate of growth of the chorionic sac is almost invariable across this period, and is remarkably uniform between individuals. Towards the end of the first trimester the intrauterine environment undergoes radical transformation in association with onset of the maternal arterial circulation and the switch to haemotrophic nutrition. The accompanying rise in intraplacental oxygen concentration poses a major challenge to placental tissues, and extensive villous remodelling takes place at this time. Later in pregnancy a wide variety of stressors are capable of affecting placental growth, but in the human, the most common are nutrient deprivation and vascular compromise. The latter is usually secondary to deficient trophoblast invasion and can induce placental oxidative stress. Closely linked to oxidative stress is endoplasmic reticulum stress, and we recently provided the first evidence that the latter plays a major role in the pathophysiology of intrauterine growth restriction. The endoplasmic reticulum is a key regulator of protein synthesis, exerting its effects through the unfolded protein response. Consequently, we observed multiple blocks to translation initiation and elongation in growth restricted placentas. Nutrient deprivation also modulates protein synthesis through the mTOR pathway, and we demonstrated interactions between this pathway and endoplasmic reticulum stress. Protein synthesis inhibition therefore appears to be a common mechanism for regulating placental development under different adverse conditions.
Endoplasmic reticulum (ER) stress is a common factor in the pathophysiology of diverse human diseases that are characterised by contrasting cellular behaviours, from proliferation in cancer to ...apoptosis in neurodegenerative disorders. Coincidently, dysregulation of AKT/PKB activity, which is the central regulator of cell growth, proliferation and survival, is often associated with the same diseases. Here, we demonstrate that ER stress modulates AKT substrate specificity in a severity-dependent manner, as shown by phospho-specific antibodies against known AKT targets. ER stress also reduces both total and phosphorylated AKT in a severity-dependent manner, without affecting activity of the upstream kinase PDK1. Normalisation to total AKT revealed that under ER stress phosphorylation of Thr308 is suppressed while that of Ser473 is increased. ER stress induces GRP78, and siRNA-mediated knock-down of GRP78 enhances phosphorylation at Ser473 by 3.6 fold, but not at Thr308. Substrate specificity is again altered. An in-situ proximity ligation assay revealed a physical interaction between GRP78 and AKT at the plasma membrane of cells following induction of ER stress. Staining was weak in cells with normal nuclear morphology but stronger in those displaying rounded, condensed nuclei. Co-immunoprecipitation of GRP78 and P-AKT(Ser473) confirmed the immuno-complex consists of non-phosphorylated AKT (Ser473 and Thr308). The interaction is likely specific as AKT did not bind to all molecular chaperones, and GRP78 did not bind to p70 S6 kinase. These findings provide one mechanistic explanation for how ER stress contributes to human pathologies demonstrating contrasting cell fates via modulation of AKT signalling.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Objective
To determine the inter‐relationships between five first‐trimester biomarkers (pregnancy associated plasma protein A PAPP‐A, alpha‐fetoprotein AFP, beta human chorionic gonadotrophin ...beta‐hCG, placenta growth factor PlGF and soluble fms‐like tyrosine kinase receptor‐1 sFlt‐1) and a range of adverse pregnancy outcomes (APOs).
Design
Prospective cohort study of nulliparous singleton pregnancy.
Setting
Cambridge, UK.
Population or Sample
4056 pregnancy outcome prediction study participants.
Methods
The biomarker concentrations were measured in maternal serum at ~12 weeks of gestation. Univariable analysis of APOs was performed using logistic regression. Multivariable analysis used best subsets logistic regression with cross‐validation.
Main outcome measures
Pre‐eclampsia (PE), small for gestational age (SGA), including severe SGA (birthweight <3rd), fetal growth restriction (FGR), preterm birth (PTB, both induced and spontaneous iPTB and sPTB, respectively), pre‐viable loss and stillbirth, plus combinations of outcomes.
Results
Lower values of PAPP‐A, PlGF and sFlt‐1 and higher values of AFP were associated with FGR (OR for 1 SD higher value 0.59 95% CI 0.48–0.74, OR 0.56 95% CI 0.44–0.70, OR 0.68 95% CI 0.54–0.87 and OR 1.53 95% CI 1.25–1.88), severe SGA (OR 0.59 95% CI 0.49–0.72, OR 0.71 95% CI 0.57–0.87, OR 0.74 95% CI 0.60–0.91 and OR 1.41 95% CI 1.17–1.71), sPTB (OR 0.61 95% CI 0.50–0.73, OR 0.79 95% CI 0.66–0.96, OR 0.57 95% CI 0.47–0.70 and OR 1.41 95% CI 1.18–1.67) and iPTB (OR 0.72 95% CI 0.57–0.91, OR 0.62 95% CI 0.49–0.78, OR 0.71 95% CI 0.56–0.90 and OR 1.44 95% CI 1.16–1.78), respectively. When combinations of biomarkers were assessed, PAPP‐A and AFP were independently associated with severe SGA; PAPP‐A alone with PE + PTB; PlGF alone with severe PE; PlGF, beta‐hCG, AFP and PAPP‐A with the combination of PE and SGA; AFP and sFlt‐1 with sPTB; and AFP and PlGF with iPTB.
Conclusions
Combinations of first‐trimester placental biomarkers are associated with APOs. However, the patterns vary for different types of APO, indicating heterogeneity in the underlying pathophysiological pathways.
Key points
Exposure of pregnant mice to chronic hypoxia at 13% O2 induces fetal growth restriction but increases placental weight.
Sex dimorphism induces differential responses in placental weight to ...hypoxia. The male placenta is heavier than the female and is associated with less severe fetal growth restriction.
Increases in maternal arterial/venous blood spaces and higher protein kinase B (Akt)‐mechanistic target of rapamycin growth signalling could contribute to the heavier hypoxic placenta.
Placental endoplasmic reticulum stress is elevated equally in both sexes in response to hypoxia. In comparison, oxidative stress is only apparent in female placentas.
Chronic hypoxia induces down‐regulation of placental mitochondrial electron transport chain complexes protein subunits but does not cause intracellular energy depletion.
Chronic hypoxia is a common complication of pregnancy, arising through malperfusion of the placenta or pregnancy at high altitude. The present study investigated the effects of hypoxia on the growth of the placenta, which is the organ that interfaces between the mother and her fetus. Mice were housed in an hypoxic environment for the whole of gestation. An atmosphere of 13% oxygen induced fetal growth restriction (1182 ± 9 mg, n = 90 vs. 1044 ± 11 mg, n = 62, P < 0.05) but enhanced placental weight (907 ± 11 mg, n = 90 vs. 998 ± 15 mg, n = 62,P < 0.05). Stereological analyses revealed an increase in the volume of maternal blood spaces in the placenta, consistent with increased flow. At the molecular level, we observed activation of the protein kinase B (Akt)‐mechanistic target of rapamycin growth and proliferation pathway. Chronic hypoxia also triggered mild endoplasmic reticulum stress, a conserved homeostatic response that mediates translational arrest through phosphorylation of eukaryotic initiation factor 2 subunit α. Surprisingly, although subunits of the mitochondrial electron transport chain complexes were reduced at the protein level, there was no evidence of intracellular energy depletion. Finally, we demonstrated sex‐specific placental responses to chronic hypoxia. Placentas from male fetuses were heavier (1082 ± 2 mg, n = 30 vs. 928 ± 2 mg, n = 34, P < 0.05) and less susceptible to hypoxia‐induced oxidative stress than those from females. Their capacity to adapt may explain why male fetuses were significantly less growth restricted at embryonic day 18.5 than their female counterparts. These findings are consistent with the concept that male fetuses are more aggressive with respect to their nutrient demands, which may place them at greater risk of adverse outcomes under limiting conditions.
Key points
Exposure of pregnant mice to chronic hypoxia at 13% O2 induces fetal growth restriction but increases placental weight.
Sex dimorphism induces differential responses in placental weight to hypoxia. The male placenta is heavier than the female and is associated with less severe fetal growth restriction.
Increases in maternal arterial/venous blood spaces and higher protein kinase B (Akt)‐mechanistic target of rapamycin growth signalling could contribute to the heavier hypoxic placenta.
Placental endoplasmic reticulum stress is elevated equally in both sexes in response to hypoxia. In comparison, oxidative stress is only apparent in female placentas.
Chronic hypoxia induces down‐regulation of placental mitochondrial electron transport chain complexes protein subunits but does not cause intracellular energy depletion.
We sought to assess the ratio of sFlt-1 (soluble fms-like tyrosine kinase 1) to PlGF (placental growth factor) in maternal serum as a screening test for preeclampsia in unselected nulliparous women ...with a singleton pregnancy. We studied 4099 women recruited to the POP study (Pregnancy Outcome Prediction) (Cambridge, United Kingdom). The sFlt-1:PlGF ratio was measured using the Roche Cobas e411 platform at ≈20, ≈28, and ≈36 weeks of gestational age (wkGA). Screen positive was defined as an sFlt-1:PlGF ratio >38, but higher thresholds were also studied. At 28 wkGA, an sFlt-1:PlGF ratio >38 had a positive predictive value (PPV) of 32% for preeclampsia and preterm birth, and the PPV was similar comparing women with low and high prior risk of disease. At 36 wkGA, an sFlt-1:PlGF ratio >38 had a PPV for severe preeclampsia of 20% in high-risk women and 6.4% in low-risk women. At 36 wkGA, an sFlt-1:PlGF ratio >110 had a PPV of 30% for severe preeclampsia, and the PPV was similar comparing low- and high-risk women. Overall, at 36 wkGA, 195 (5.2%) women either had an sFlt-1:PlGF ratio of >110 or an sFlt-1:PlGF ratio >38 plus maternal risk factors: 43% of these women developed preeclampsia, about half with severe features. Among low-risk women at 36 wkGA, an sFlt-1:PlGF ratio ≤38 had a negative predictive value for severe preeclampsia of 99.2%. The sFlt-1:PlGF ratio provided clinically useful prediction of the risk of the most important manifestations of preeclampsia in a cohort of unselected nulliparous women.
Fetal growth restriction (FGR) is the major single cause of stillbirth
and is also associated with neonatal morbidity and mortality
, impaired health and educational achievement in childhood
and with ...a range of diseases in later life
. Effective screening and intervention for FGR is an unmet clinical need. Here, we performed ultrahigh performance liquid chromatography-tandem mass spectroscopy (UPLC-MS/MS) metabolomics on maternal serum at 12, 20 and 28 weeks of gestational age (wkGA) using 175 cases of term FGR and 299 controls from the Pregnancy Outcome Prediction (POP) study, conducted in Cambridge, UK, to identify predictive metabolites. Internal validation using 36 wkGA samples demonstrated that a ratio of the products of the relative concentrations of two positively associated metabolites (1-(1-enyl-stearoyl)-2-oleoyl-GPC (P-18:0/18:1) and 1,5-anhydroglucitol) to the product of the relative concentrations of two negatively associated metabolites (5α-androstan-3α,17α-diol disulfate and N1,N12-diacetylspermine) predicted FGR at term. The ratio had approximately double the discrimination as compared to a previously developed angiogenic biomarker
, the soluble fms-like tyrosine kinase 1:placental growth factor (sFLT1:PlGF) ratio (AUC 0.78 versus 0.64, P = 0.0001). We validated the predictive performance of the metabolite ratio in two sub-samples of a demographically dissimilar cohort, Born in Bradford (BiB), conducted in Bradford, UK (P = 0.0002). Screening and intervention using this metabolite ratio in conjunction with ultrasonic imaging at around 36 wkGA could plausibly prevent adverse events through enhanced fetal monitoring and targeted induction of labor.
Placentas can exhibit chromosomal aberrations that are absent from the fetus
. The basis of this genetic segregation, which is known as confined placental mosaicism, remains unknown. Here we ...investigated the phylogeny of human placental cells as reconstructed from somatic mutations, using whole-genome sequencing of 86 bulk placental samples (with a median weight of 28 mg) and of 106 microdissections of placental tissue. We found that every bulk placental sample represents a clonal expansion that is genetically distinct, and exhibits a genomic landscape akin to that of childhood cancer in terms of mutation burden and mutational imprints. To our knowledge, unlike any other healthy human tissue studied so far, the placental genomes often contained changes in copy number. We reconstructed phylogenetic relationships between tissues from the same pregnancy, which revealed that developmental bottlenecks genetically isolate placental tissues by separating trophectodermal lineages from lineages derived from the inner cell mass. Notably, there were some cases with full segregation-within a few cell divisions of the zygote-of placental lineages and lineages derived from the inner cell mass. Such early embryonic bottlenecks may enable the normalization of zygotic aneuploidy. We observed direct evidence for this in a case of mosaic trisomic rescue. Our findings reveal extensive mutagenesis in placental tissues and suggest that mosaicism is a typical feature of placental development.
We sought to determine whether pre-eclampsia, spontaneous preterm birth or the delivery of infants who are small for gestational age were associated with the presence of bacterial DNA in the human ...placenta. Here we show that there was no evidence for the presence of bacteria in the large majority of placental samples, from both complicated and uncomplicated pregnancies. Almost all signals were related either to the acquisition of bacteria during labour and delivery, or to contamination of laboratory reagents with bacterial DNA. The exception was Streptococcus agalactiae (group B Streptococcus), for which non-contaminant signals were detected in approximately 5% of samples collected before the onset of labour. We conclude that bacterial infection of the placenta is not a common cause of adverse pregnancy outcome and that the human placenta does not have a microbiome, but it does represent a potential site of perinatal acquisition of S. agalactiae, a major cause of neonatal sepsis.
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