The potential role of pregnancy-associated plasma protein-A2 in angiogenesis and development of preeclampsia

Comparative single cell analysis reveals complex patterns of cell type and cell signaling innovations at the fetal-maternal interface

The decidual-placental interface is one of the most diverse and rapidly evolving tissues in mammals. Its origin as a chimeric fetal-maternal tissue poses a unique evolutionary puzzle. We present single-cell RNA sequencing atlases from the fetal-maternal interfaces of the opossum, a marsupial, the Malagasy common tenrec, an afrotherian with primitive reproductive features, and mouse, guinea pig, and human. Invasive trophoblast shares a common transcriptomic signature across eutherians, which we argue represents a cell type family that radiated following the evolution of hemochorial placentation. We find evidence that the eutherian decidual stromal cell evolved stepwise from a predecidual state retained in Tenrec , followed by a second decidual cell type originating in Boreoeutheria with endocrine characteristics. We reconstruct ligand-receptor signaling to test evolutionary hypotheses at scale. Novel trophoblast and decidual cell types display strong integration into signaling networks compared to other cells. Additionally, we find consistent disambiguation between fetal and maternal signaling. Using phylogenetic analysis, we infer the cell-cell signaling network of the Placental common ancestor, and identify increased rates of signaling evolution in Euarchontoglires. Together, our findings reveal novel cell type identities and cell signaling dynamics at the mammalian fetal-maternal interface.

Analysis of Predictive Information From Biomarkers Added to Clinical Models of Preeclampsia: Consideration of PAPP-A2, Activin A, and sFlt-1:PlGF Ratio

BACKGROUND

Preeclampsia remains a major cause of maternal and fetal adverse outcomes in pregnancy; however, accurate and universally acceptable predictive tools remain elusive. We investigated whether a panel of biomarkers could improve risk prediction for preeclampsia when measured at various pregnancy time points.

METHODS

In this prospective cohort study, 192 women with first-trimester high-risk singleton pregnancies were consecutively recruited from tertiary obstetrics clinics in Montréal, Canada. Clinical information (height, pre-pregnancy weight, personal and family medical history, medication use) was collected at baseline. Blood pressure was measured and blood samples collected at each trimester to quantify soluble Fms-like tyrosine kinase 1 (sFlt-1), placental growth factor (PlGF), pregnancy-associated plasma protein A2 (PAPP-A2), PAPP-A, activin A, inhibin A, follistatin, and glycosylated fibronectin. A random-effects hierarchic logistic regression model was used to relate change in biomarker levels to incidence of preeclampsia.

RESULTS

When added to a clinical model composed of maternal age, pre-pregnancy body mass index, race, and mean arterial pressure, a positive third-trimester result for both PAPP-A2 and activin A had a better positive predictive value than the sFlt-1:PlGF ratio added to the clinical model (91.67% [95% confidence interval (CI) 78.57%-100%] vs 66.67% [57.14%-100%]), while maintaining a comparable high negative predictive value (97.69% [95% CI 95.34%-100%] vs 96.00% [92.19%-99.21%]).

CONCLUSIONS

Whereas the third-trimester sFlt-1:PlGF ratio can predict short-term absence of preeclampsia, PAPP-A2 and activin A had both high positive and negative predictive values and therefore could serve as biomarkers to predict the occurrence (and absence) of preeclampsia; these findings will be validated in future studies.

Alpha-2-macroglobulin is involved in the occurrence of early-onset pre-eclampsia via its negative impact on uterine spiral artery remodeling and placental angiogenesis

BACKGROUND

Pre-eclampsia (PE) is one of the leading causes of maternal and fetal morbidity/mortality during pregnancy, and alpha-2-macroglobulin (A2M) is associated with inflammatory signaling; however, the pathophysiological mechanism by which A2M is involved in PE development is not yet understood.

METHODS

Human placenta samples, serum, and corresponding clinical data of the participants were collected to study the pathophysiologic mechanism underlying PE. Pregnant Sprague-Dawley rats were intravenously injected with an adenovirus vector carrying A2M via the tail vein on gestational day (GD) 8.5. Human umbilical artery smooth muscle cells (HUASMCs), human umbilical vein endothelial cells (HUVECs), and HTR-8/SVneo cells were transfected with A2M-expressing adenovirus vectors.

RESULTS

In this study, we demonstrated that A2M levels were significantly increased in PE patient serum, uterine spiral arteries, and feto-placental vasculature. The A2M-overexpression rat model closely mimicked the characteristics of PE (i.e., hypertension in mid-to-late gestation, histological and ultrastructural signs of renal damage, proteinuria, and fetal growth restriction). Compared to the normal group, A2M overexpression significantly enhanced uterine artery vascular resistance and impaired uterine spiral artery remodeling in both pregnant women with early-onset PE and in pregnant rats. We found that A2M overexpression was positively associated with HUASMC proliferation and negatively correlated with cell apoptosis. In addition, the results demonstrated that transforming growth factor beta 1 (TGFβ1) signaling regulated the effects of A2M on vascular muscle cell proliferation described above. Meanwhile, A2M overexpression regressed rat placental vascularization and reduced the expression of angiogenesis-related genes. In addition, A2M overexpression reduced HUVEC migration, filopodia number/length, and tube formation. Furthermore, HIF-1α expression was positively related to A2M, and the secretion of sFLT-1 and PIGF of placental origin was closely related to PE during pregnancy or A2M overexpression in rats.

CONCLUSIONS

Our data showed that gestational A2M overexpression can be considered a contributing factor leading to PE, causing detective uterine spiral artery remodeling and aberrant placental vascularization.

Comprehensive analysis of transcriptomic profiling of 5-methylcytosin modification in placentas from preeclampsia and normotensive pregnancies

Increasing evidence suggests that RNA m5C modification and its regulators have been confirmed to be associated with the pathogenesis of many diseases. However, the distribution and biological functions of m5C in mRNAs of placental tissues remain unknown. we collected placentae from normotensive pregnancies (CTR) and preeclampsia patients (PE) to analyze the transcriptomic profiling of m5C RNA methylation through m5C RNA immunoprecipitation (UMI-MeRIP-Seq). we discovered that overall m5C methylation peaks were decreased in placental tissues from PE patients. And, 2844 aberrant m5C peaks were identified, of which respectively 1304 m5C peaks were upregulated and 1540 peaks were downregulated. The distribution of m5C peaks were mainly located in CDS (coding sequences) regions in placental tissues of both groups, but compared with the CTR group, the m5C peak in PE group before the stop code of CDS was significantly increased and even higher than the peak value after start code in CDS. Differentially methylated genes were mainly enriched in MAPK/cAMP signaling pathway. Moreover, the up-regulated genes with hypermethylated modification were enriched in the processes of hypoxia, inflammation/immune response. Finally, through analyzing the mRNA expression levels of m5C RNA methylation regulators, we found only DNMT3B and TET3 were significantly upregulated in PE samples than in control group. And they are not only negatively correlated with each other, but also closely related to those differentially expressed genes modified by differential methylation.Our findings provide new insights regarding alterations of m5C RNA modification into the pathogenic mechanisms of PE.

Placental protein levels in maternal serum are associated with adverse pregnancy outcomes in nulliparous patients

BACKGROUND

The Eunice Kennedy Shriver National Institute of Child Health and Human Development Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be was established to investigate the underlying causes and pathophysiological pathways associated with adverse pregnancy outcomes in nulliparous gravidas.

OBJECTIVE

This study aimed to study placental physiology and identify novel biomarkers concerning adverse pregnancy outcomes, including preterm birth (medically indicated and spontaneous), preeclampsia, small-for-gestational-age neonates, and stillbirth. We measured levels of placental proteins in the maternal circulation in the first 2 trimesters of pregnancy.

STUDY DESIGN

Maternal serum samples were collected at 2 study visits (6-13 weeks and 16-21 weeks), and levels of 9 analytes were measured. The analytes we measured were vascular endothelial growth factor, placental growth factor, endoglin, soluble fms-like tyrosine kinase-1, A disintegrin and metalloproteinase domain-containing protein 12, pregnancy-associated plasma protein A, free beta-human chorionic gonadotropin, inhibin A, and alpha-fetoprotein. The primary outcome was preterm birth between 20 0/7 and 36 6/7 weeks of gestation. The secondary outcomes were spontaneous preterm births, medically indicated preterm births, preeclampsia, small-for-gestational-age neonates, and stillbirth.

RESULTS

A total of 10,038 eligible gravidas were enrolled in the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be cohort, from which a nested case-control study was performed comparing 800 cases with preterm birth (466 spontaneous preterm births, 330 medically indicated preterm births, and 4 unclassified preterm births), 568 with preeclampsia, 406 with small-for-gestational-age birth, and 49 with stillbirth with 911 controls who delivered at term without complications. Although levels of each analyte generally differed between cases and controls at 1 or 2 visits, the odds ratios revealed a <2-fold difference between cases and controls in all comparisons. Receiver operating characteristic curves, generated to determine the relationship between analyte levels and preterm birth and the other adverse pregnancy outcomes, resulted in areas under the receiver operating characteristic curves that were relatively low (range, 0.50-0.64) for each analyte. Logistic regression modeling demonstrated that areas under the receiver operating characteristic curves for predicting adverse pregnancy outcomes were greater using baseline clinical characteristics and combinations of analytes than baseline characteristics alone, but areas under the receiver operating characteristic curves remained relatively low for each outcome (range, 0.65-0.78).

CONCLUSION

We have found significant associations between maternal serum levels of analytes evaluated early in pregnancy and subsequent adverse pregnancy outcomes in nulliparous gravidas. However, the test characteristics for these analytes do not support their use as clinical biomarkers to predict adverse pregnancy outcomes, either alone or in combination with maternal clinical characteristics.

Fear Stress During Pregnancy Affects Placental m6A-Modifying Enzyme Expression and Epigenetic Modification Levels

As the hub connecting mother and offspring, the placenta’s normal development is vital for fetal growth. Fear stress can cause some structural alterations in the placenta and affect placental development and function. N6-methyladenosine (m6A) is the most common mRNA modification and is involved in regulating the development of the placenta and embryo. There are no reports on the potential role of m6A modification in placental damage caused by fear stress during pregnancy. In this study, we demonstrated that fear stress during pregnancy increases the levels of methylated enzymes (METTL3, METTL14, and WTAP), decreases the levels of demethylase FTO, and increases the overall methylation levels in the placenta of pregnant rats. MeRIP-seq data analysis revealed 22,010 m6A peaks associated with 12,219 genes in the placenta of the model and 21,060 m6A peaks associated with 11,730 genes in the placenta of the control. The peaks were mainly concentrated in the coding region and the 3ʹ untranslated region. In addition, 50 genes with abnormal modification and expression (double aberrant genes) were screened out by combining MeRIP-seq and RNA-seq data. Mefv, Erbb2, and Cgas were selected from 50 double aberrant genes, and MeRIP-qPCR and real-time quantitative polymerase chain reaction were used to verify their modification and expression levels. Our findings suggest that m6A modifications play an important role in placental dysfunction induced by fear stress during pregnancy.

RNA profiles reveal signatures of future health and disease in pregnancy

Maternal morbidity and mortality continue to rise, and pre-eclampsia is a major driver of this burden1. Yet the ability to assess underlying pathophysiology before clinical presentation to enable identification of pregnancies at risk remains elusive. Here we demonstrate the ability of plasma cell-free RNA (cfRNA) to reveal patterns of normal pregnancy progression and determine the risk of developing pre-eclampsia months before clinical presentation. Our results centre on comprehensive transcriptome data from eight independent prospectively collected cohorts comprising 1,840 racially diverse pregnancies and retrospective analysis of 2,539 banked plasma samples. The pre-eclampsia data include 524 samples (72 cases and 452 non-cases) from two diverse independent cohorts collected 14.5 weeks (s.d., 4.5 weeks) before delivery. We show that cfRNA signatures from a single blood draw can track pregnancy progression at the placental, maternal and fetal levels and can robustly predict pre-eclampsia, with a sensitivity of 75% and a positive predictive value of 32.3% (s.d., 3%), which is superior to the state-of-the-art method2. cfRNA signatures of normal pregnancy progression and pre-eclampsia are independent of clinical factors, such as maternal age, body mass index and race, which cumulatively account for less than 1% of model variance. Further, the cfRNA signature for pre-eclampsia contains gene features linked to biological processes implicated in the underlying pathophysiology of pre-eclampsia.

Cilengitide Inhibits Neovascularization in a Rabbit Abdominal Aortic Plaque Model by Impairing the VEGF Signaling

Background

Cilengitide is a selective α_vβ₃ and α_vβ₅ integrin inhibitor. We sought to investigate the effect of cilengitide on the neovascularization of abdominal aortic plaques in rabbits and explore its underlying antiangiogenic mechanism on human umbilical vein endothelial cells (HUVECs).

Materials and Methods

For the in vivo experiment, the abdominal aortic plaque model of rabbits was established and injected with different doses of cilengitide or saline for 14 consecutive days. Conventional ultrasound (CUS) and contrast-enhanced ultrasound (CEUS) were applied to measure the vascular structure and blood flow parameters. CD31 immunofluorescence staining was performed for examining neovascularization. Relative expressions of vascular endothelial growth factor (VEGF) and integrin of the plaque were determined. For in vitro experiments, HUVECs were tested for proliferation, migration, apoptosis, and tube formation in the presence of different doses of cilengitide. Relative expressions of VEGF, integrin, and Ras/ERK/AKT signaling pathways were determined for the exploration of underlying mechanism.

Results

CEUS showed modestly increased size and eccentricity index (EI) of plaques in the control group. Different degrees of reduced size and EI of plaques were observed in two cilengitide treatment groups. The expressions of VEGF and integrin in the plaque were inhibited after 14 days of cilengitide treatment. The neovascularization and apoptosis of the abdominal aorta were also significantly alleviated by cilengitide treatment. For in vitro experiments, cilengitide treatment was found to inhibit the proliferation, migration, and tube formation of HUVECs. However, cilengitide did not induce the apoptosis of HUVECs. A higher dose of cilengitide inhibited the mRNA expression of VEGF-A, β₃, and β₅, but not α_V. Lastly, cilengitide treatment significantly inhibited the Ras/ERK/AKT pathway in the HUVECs. Conclusions. This study showed that cilengitide effectively inhibited the growth of plaque size by inhibiting the angiogenesis of the abdominal aortic plaques and blocking the VEGF-mediated angiogenic effect on HUVECs.

PAPPA2 Promote the Proliferation of Dermal Papilla Cells in Hu Sheep (Ovis aries) by Regulating IGFBP5

Hu sheep (Ovis aries) is a rare white sheep breed, with four different types of lambskin patterns that have different values. However, the genetic mechanisms underlying different types of pattern formation remains unclear. This research aimed to characterize the molecular mechanism of differentially expressed gene PAPPA2 affecting the pattern type of Hu sheep's lambskin at the cellular level. Thus, RT-qPCR, EdU and Cell Cycle detection were used to explore the effect of PAPPA2 and IGFBP5 (a protein that can be hydrolyzed by PAPPA2) on the proliferation of dermal papilla cells (DPCs) after overexpression or interference with PAPPA2 and IGFBP5. The expression level of PAPPA2 in straight DPCs was 4.79 ± 1.84 times higher than curved. Overexpression of PAPPA2 promoted the proliferation of DPCs and also increased the expression of IGFBP5. Conversely, overexpression of IGFBP5 reduced the proliferation of DPCs. However, the proliferation of DPCs was restored by co-overexpression of PAPPA2 and IGFBP5 compared with overexpression of IGFBP5 alone. Thus, PAPPA2 can affect the proliferation of DPCs through regulating IGFBP5 and then participate in lambskin pattern determination. Overall, we preliminarily clarified the critical role played by PAPPA2 during the formation of different pattern in Hu sheep lambskin.

Dysfunction of Shh signaling activates autophagy to inhibit trophoblast motility in recurrent miscarriage

In early pregnancy, the placenta anchors the conceptus and supports embryonic development and survival. This study aimed to investigate the underlying functions of Shh signaling in recurrent miscarriage (RM), a serious disorder of pregnancy. In the present study, Shh and Gli2 were mainly observed in cytotrophoblasts (CTBs), Ptch was mainly observed in syncytiotrophoblasts (STBs), and Smo and Gli3 were expressed in both CTBs and STBs. Shh signaling was significantly impaired in human placenta tissue from recurrent miscarriage patients compared to that of gestational age-matched normal controls. VEGF-A and CD31 protein levels were also significantly decreased in recurrent miscarriage patients. Furthermore, inhibition of Shh signaling impaired the motility of JAR cells by regulating the expression of Gli2 and Gli3. Intriguingly, inhibition of Shh signaling also triggered autophagy and autolysosome accumulation. Additionally, knockdown of BECN1 reversed Gant61-induced motility inhibition. In conclusion, our results showed that dysfunction of Shh signaling activated autophagy to inhibit trophoblast motility, which suggests the Shh pathway and autophagy as potential targets for RM therapy.

PAPP-A2 and Inhibin A as Novel Predictors for Pregnancy Complications in Women With Suspected or Confirmed Preeclampsia

Background

We aimed to evaluate the value of inhibin A and PAPP‐A2 (pregnancy‐associated plasma protein‐A2) as novel biomarkers in the prediction of preeclampsia‐related complications and how they compare with angiogenic biomarkers.

Methods and Results

Making use of a secondary analysis of a prospective, multicenter, observational study, intended to evaluate the usefulness of sFlt‐1 (soluble Fms‐like tyrosine kinase‐1)/PlGF (placental growth factor) ratio, we measured inhibin A and PAPP‐A2 levels in 524 women with suspected/confirmed preeclampsia. Women had a median gestational age of 35 weeks (range, 20–41 weeks) while preeclampsia occurred in 170 (32%) women. Levels of inhibin A and PAPP‐A2 were significantly increased in women with preeclampsia and in maternal perfusate of preeclamptic placentas. Inhibin A and PAPP‐A2 (C‐index = 0.73 and 0.75) significantly improved the prediction of maternal complications when added on top of the traditional criteria; gestational age, parity, proteinuria, and diastolic blood pressure (C‐index = 0.60). PAPP‐A2 was able to improve the C‐index from 0.75 to 0.77 when added on top of the sFlt‐1/PlGF ratio for the prediction of maternal complications. To discriminate fetal/neonatal complications on top of traditional criteria, inhibin A and PAPP‐A2 showed additive value (C‐index = 0.79 to 0.80 and 0.82, respectively) but their discriminative ability remained inferior to that of sFlt‐1/PlGF ratio or PlGF. Interestingly, the PAPP‐A2/PlGF ratio alone showed remarkable value to predict pregnancy complications, being superior to sFlt‐1/PlGF ratio in the case of maternal complications.

Conclusions

Inhibin A and PAPP‐A2 show significant potential to predict preeclampsia‐related pregnancy complications and might prove beneficial on top of the angiogenic markers.

Aberrant hydroxymethylation of ANGPTL4 is associated with selective intrauterine growth restriction in monochorionic twin pregnancies

Selective intrauterine growth restriction (sIUGR) is a severe complication in monochorionic (MC) twin pregnancies, and it carries increased risks of poor prognosis. Current data suggest that vascular anastomoses and unequal placental sharing may be the key contributor to discordant foetal growth. While MC twins derive from a single zygote and have almost identical genetic information, the precise mechanisms remain unknown. DNA hydroxymethylation is a newly discovered epigenetic feature associated with gene regulation and modification. Here, we investigate discordant hydroxymethylation patterns between two placental shares of sIUGR and analyse the potential role of aberrant hydroxymethylation of angiopoietin-like 4 (ANGPTL4) in placental dysplasia. Hydroxymethylation DNA immunoprecipitation (hMeDIP)-chip and mRNA sequencing were performed to identify hydroxymethylation-associated genes. Real-time qPCR, western blotting, and immunohistochemistry were used to confirm ANGPTL4 expression. The mechanisms regulating ANGPTL4 were investigated by cell migration assay, invasion assay, viability assay, and apoptotic ratio assays, western blotting and hMeDIP-qPCR. Decreased ANGPTL4 was detected in the smaller placental shares of sIUGR. ANGPTL4 knockdown suppressed trophoblast invasiveness and migration, which possibly occurred through hypoxia inducible factor 1α (HIF-1α) and HIF-1 signalling pathway. Hypoxia leads to aberrant expression of ANGPTL4 and HIF-1α, positively correlated with their aberrant hydroxymethylation levels in promoter regions. Aberrant hydroxymethylation of ANGPTL4 may contribute to placental impairment by the HIF-1 signalling pathway in smaller placental shares of sIUGR.

Uteroplacental Ischemia Is Associated with Increased PAPP-A2

Residence at high altitude (> 2500 m) has been associated with an increased frequency of preeclampsia. Pappalysin-2 (PAPP-A2) is an insulin-like growth factor binding protein-5 (IGFBP-5) protease that is elevated in preeclampsia, and up-regulated by hypoxia in placental explants. The relationships between PAPP-A2, altitude, and indices of uteroplacental ischemia are unknown. We aimed to evaluate the association of altitude, preeclampsia, and uterine artery flow or vascular resistance with PAPP-A2 levels. PAPP-A2, uterine artery diameter, volumetric blood flow, and pulsatility indices were measured longitudinally in normotensive Andean women residing at low or high altitudes in Bolivia and in a separate Andean high-altitude cohort with or without preeclampsia. PAPP-A2 levels increased with advancing gestation, with the rise tending to be greater at high compared to low altitude, and higher in early-onset preeclamptic compared to normotensive women at high altitude. Uterine artery blood flow was markedly lower and pulsatility index higher in early-onset preeclamptic normotensive women compared to normotensive women. PAPP-A2 was unrelated to uterine artery pulsatility index in normotensive women but positively correlated in the early-onset preeclampsia cases. We concluded that PAPP-A2 is elevated at high altitude and especially in cases of early-onset preeclampsia with Doppler indices of uteroplacental ischemia.