Exosomal small RNA profiling in first-trimester maternal blood explores early molecular pathways of preterm preeclampsia

Introduction

Preeclampsia (PE) is a severe obstetrical syndrome characterized by new-onset hypertension and proteinuria and it is often associated with fetal intrauterine growth restriction (IUGR). PE leads to long-term health complications, so early diagnosis would be crucial for timely prevention. There are multiple etiologies and subtypes of PE, and this heterogeneity has hindered accurate identification in the presymptomatic phase. Recent investigations have pointed to the potential role of small regulatory RNAs in PE, and these species, which travel in extracellular vesicles (EVs) in the circulation, have raised the possibility of non-invasive diagnostics. The aim of this study was to investigate the behavior of exosomal regulatory small RNAs in the most severe subtype of PE with IUGR.

Methods

We isolated exosomal EVs from first-trimester peripheral blood plasma samples of women who later developed preterm PE with IUGR (n=6) and gestational age-matched healthy controls (n=14). The small RNA content of EVs and their differential expression were determined by next-generation sequencing and further validated by quantitative real-time PCR. We also applied the rigorous exceRpt bioinformatics pipeline for small RNA identification, followed by target verification and Gene Ontology analysis.

Results

Overall, >2700 small RNAs were identified in all samples and, of interest, the majority belonged to the RNA interference (RNAi) pathways. Among the RNAi species, 16 differentially expressed microRNAs were up-regulated in PE, whereas up-regulated and down-regulated members were equally found among the six identified Piwi-associated RNAs. Gene ontology analysis of the predicted small RNA targets showed enrichment of genes in pathways related to immune processes involved in decidualization, placentation and embryonic development, indicating that dysregulation of the induced small RNAs is connected to the impairment of immune pathways in preeclampsia development. Finally, the subsequent validation experiments revealed that the hsa_piR_016658 piRNA is a promising biomarker candidate for preterm PE associated with IUGR.

Discussion

Our rigorously designed study in a homogeneous group of patients unraveled small RNAs in circulating maternal exosomes that act on physiological pathways dysregulated in preterm PE with IUGR. Therefore, our small RNA hits are not only suitable biomarker candidates, but the revealed biological pathways may further inform us about the complex pathology of this severe PE subtype.

Decreased Expression of Placental Proteins in Recurrent Pregnancy Loss: Functional Relevance and Diagnostic Value

Miscarriages affect 50-70% of all conceptions and 15-20% of clinically recognized pregnancies. Recurrent pregnancy loss (RPL, ≥2 miscarriages) affects 1-5% of recognized pregnancies. Nevertheless, our knowledge about the etiologies and pathophysiology of RPL is incomplete, and thus, reliable diagnostic/preventive tools are not yet available. Here, we aimed to define the diagnostic value of three placental proteins for RPL: human chorionic gonadotropin free beta-subunit (free-β-hCG), pregnancy-associated plasma protein-A (PAPP-A), and placental growth factor (PlGF). Blood samples were collected from women with RPL (n = 14) and controls undergoing elective termination of pregnancy (n = 30) at the time of surgery. Maternal serum protein concentrations were measured by BRAHMS KRYPTOR Analyzer. Daily multiple of median (dMoM) values were calculated for gestational age-specific normalization. To obtain classifiers, logistic regression analysis was performed, and ROC curves were calculated. There were differences in changes of maternal serum protein concentrations with advancing healthy gestation. Between 6 and 13 weeks, women with RPL had lower concentrations and dMoMs of free β-hCG, PAPP-A, and PlGF than controls. PAPP-A dMoM had the best discriminative properties (AUC = 0.880). Between 9 and 13 weeks, discriminative properties of all protein dMoMs were excellent (free β-hCG: AUC = 0.975; PAPP-A: AUC = 0.998; PlGF: AUC = 0.924). In conclusion, free-β-hCG and PAPP-A are valuable biomarkers for RPL, especially between 9 and 13 weeks. Their decreased concentrations indicate the deterioration of placental functions, while lower PlGF levels indicate problems with placental angiogenesis after 9 weeks.

Classification of preeclampsia according to molecular clusters with the goal of achieving personalized prevention

The prevention of pre-eclampsia is difficult due to the syndromic nature and multiple underlying mechanisms of this severe complication of pregnancy. The current clinical distinction between early- and late-onset disease, although clinically useful, does not reflect the true nature and complexity of the pathologic processes leading to pre-eclampsia. The current gaps in knowledge on the heterogeneous molecular pathways of this syndrome and the lack of adequate, specific diagnostic methods are major obstacles to early screening and tailored preventive strategies. The development of novel diagnostic tools for detecting the activation of the identified disease pathways would enable early, accurate screening and personalized preventive therapies. We implemented a holistic approach that includes the utilization of different proteomic profiling methods of maternal plasma samples collected from various ethnic populations and the application of systems biology analysis to plasma proteomic, maternal demographic, clinical characteristic, and placental histopathologic data. This approach enabled the identification of four molecular subclasses of pre-eclampsia in which distinct and shared disease mechanisms are activated. The current review summarizes the results and conclusions from these studies and the research and clinical implications of our findings.

Proteomic profile of extracellular vesicles in maternal plasma of women with fetal death

OBJECTIVES

Fetal death is a complication of pregnancy caused by multiple etiologies rather than being the end-result of a single disease process. Many soluble analytes in the maternal circulation, such as hormones and cytokines, have been implicated in its pathophysiology. However, changes in the protein content of extracellular vesicles (EVs), which could provide additional insight into the disease pathways of this obstetrical syndrome, have not been examined. This study aimed to characterize the proteomic profile of EVs in the plasma of pregnant women who experienced fetal death and to evaluate whether such a profile reflected the pathophysiological mechanisms of this obstetrical complication. Moreover, the proteomic results were compared to and integrated with those obtained from the soluble fraction of maternal plasma.

METHODS

This retrospective case-control study included 47 women who experienced fetal death and 94 matched, healthy, pregnant controls. Proteomic analysis of 82 proteins in the EVs and the soluble fractions of maternal plasma samples was conducted by using a bead-based, multiplexed immunoassay platform. Quantile regression analysis and random forest models were implemented to assess differences in the concentration of proteins in the EV and soluble fractions and to evaluate their combined discriminatory power between clinical groups. Hierarchical cluster analysis was applied to identify subgroups of fetal death cases with similar proteomic profiles. A p-value of <.05 was used to infer significance, unless multiple testing was involved, with the false discovery rate controlled at the 10% level (q < 0.1). All statistical analyses were performed by using the R statistical language and environment-and specialized packages.

RESULTS

Nineteen proteins (placental growth factor, macrophage migration inhibitory factor, endoglin, regulated upon activation normal T cell expressed and presumably secreted (RANTES), interleukin (IL)-6, macrophage inflammatory protein 1-alpha, urokinase plasminogen activator surface receptor, tissue factor pathway inhibitor, IL-8, E-Selectin, vascular endothelial growth factor receptor 2, pentraxin 3, IL-16, galectin-1, monocyte chemotactic protein 1, disintegrin and metalloproteinase domain-containing protein 12, insulin-like growth factor-binding protein 1, matrix metalloproteinase-1(MMP1), and CD163) were found to have different plasma concentrations (of an EV or a soluble fraction) in women with fetal death compared to controls. There was a similar pattern of change for the dysregulated proteins in the EV and soluble fractions and a positive correlation between the log₂-fold changes of proteins significant in either the EV or the soluble fraction (ρ = 0.89, p < .001). The combination of EV and soluble fraction proteins resulted in a good discriminatory model (area under the ROC curve, 82%; sensitivity, 57.5% at a 10% false-positive rate). Unsupervised clustering based on the proteins differentially expressed in either the EV or the soluble fraction of patients with fetal death relative to controls revealed three major clusters of patients.

CONCLUSION

Pregnant women with fetal death have different concentrations of 19 proteins in the EV and soluble fractions compared to controls, and the direction of changes in concentration was similar between fractions. The combination of EV and soluble protein concentrations revealed three different clusters of fetal death cases with distinct clinical and placental histopathological characteristics.

Molecular subclasses of preeclampsia characterized by a longitudinal maternal proteomics study: distinct biomarkers, disease pathways and options for prevention

OBJECTIVES

The heterogeneous nature of preeclampsia is a major obstacle to early screening and prevention, and a molecular taxonomy of disease is needed. We have previously identified four subclasses of preeclampsia based on first-trimester plasma proteomic profiles. Herein, we expanded this approach by using a more comprehensive panel of proteins profiled in longitudinal samples.

METHODS

Proteomic data collected longitudinally from plasma samples of women who developed preeclampsia (n=109) and of controls (n=90) were available from our previous report on 1,125 proteins. Consensus clustering was performed to identify subgroups of patients with preeclampsia based on data from five gestational-age intervals by using select interval-specific features. Demographic, clinical, and proteomic differences among clusters were determined. Differentially abundant proteins were used to identify cluster-specific perturbed KEGG pathways.

RESULTS

Four molecular clusters with different clinical phenotypes were discovered by longitudinal proteomic profiling. Cluster 1 involves metabolic and prothrombotic changes with high rates of early-onset preeclampsia and small-for-gestational-age neonates; Cluster 2 includes maternal anti-fetal rejection mechanisms and recurrent preeclampsia cases; Cluster 3 is associated with extracellular matrix regulation and comprises cases of mostly mild, late-onset preeclampsia; and Cluster 4 is characterized by angiogenic imbalance and a high prevalence of early-onset disease.

CONCLUSIONS

This study is an independent validation and further refining of molecular subclasses of preeclampsia identified by a different proteomic platform and study population. The results lay the groundwork for novel diagnostic and personalized tools of prevention.

Placental galectins regulate innate and adaptive immune responses in pregnancy

Introduction

Galectins are master regulators of maternal immune responses and placentation in pregnancy. Galectin-13 (gal-13) and galectin-14 (gal-14) are expressed solely by the placenta and contribute to maternal-fetal immune tolerance by inducing the apoptosis of activated T lymphocytes and the polarization of neutrophils toward an immune-regulatory phenotype.Furthermore, their decreased placental expression is associated with pregnancy complications, such as preeclampsia and miscarriage. Yet, our knowledge of the immunoregulatory role of placental galectins is incomplete.

Methods

This study aimed to investigate the effects of recombinant gal-13 and gal-14 on cell viability, apoptosis, and cytokine production of peripheral blood mononuclear cells (PBMCs) and the signaling pathways involved.

Results

Herein, we show that gal-13 and gal-14 bind to the surface of non-activated PBMCs (monocytes, natural killer cells, B cells, and T cells) and increase their viability while decreasing the rate of their apoptosis without promoting cell proliferation. We also demonstrate that gal-13 and gal-14 induce the production of interleukin (IL)-8, IL-10, and interferon-gamma cytokines in a concentration-dependent manner in PBMCs. The parallel activation of Erk1/2, p38, and NF-ĸB signaling evidenced by kinase phosphorylation in PBMCs suggests the involvement of these pathways in the regulation of the galectin-affected immune cell functions.

Discussion

These findings provide further evidence on how placenta-specific galectins assist in the establishment and maintenance of a proper immune environment during a healthy pregnancy.

The role of neutrophil activation in determining the outcome of pregnancy and modulation by hormones and/or cytokines

Neutrophils are often exclusively considered as a first-line innate immune defence, able to rapidly kill or trap pathogens and causing in case of over-activation tissue damage. In the female reproductive tract, however, the presence and activity of neutrophils seems to be tightly regulated. Major players in orchestrating this regulation are cyclical steroid sex hormones present during the menstrual cycle and pregnancy. This review describes the role of sex hormones in regulating directly or indirectly the functionality of neutrophils, the role of neutrophils during fertilization and pregnancy and in controlling viral, fungal and bacterial infection. This review also discusses the consequence of overt neutrophil activation in pregnancy pathologies.

Evolutionary origins of the placental expression of chromosome 19 cluster galectins and their complex dysregulation in preeclampsia

INTRODUCTION

The dysregulation of maternal-fetal immune tolerance is one of the proposed mechanisms leading to preeclampsia. Galectins are key regulator proteins of the immune response in vertebrates and maternal-fetal immune tolerance in eutherian mammals. Previously we found that three genes in a Chr19 cluster encoding for human placental galectin-13 (PP13), galectin-14 and galectin-16 emerged during primate evolution and may confer immune tolerance to the semi-allogeneic fetus.

MATERIALS AND METHODS

This study involved various methodologies for gene and protein expression profiling, genomic DNA methylation analyses, functional assays on differentiating trophoblasts including gene silencing, luciferase reporter and methylation assays. These methods were applied on placental specimens, umbilical cord blood cells, primary trophoblasts and BeWo cells. Genomic DNA sequences were analyzed for transposable elements, transcription factor binding sites and evolutionary conservation.

RESULTS AND DISCUSSION

The villous trophoblastic expression of Chr19 cluster galectin genes is developmentally regulated by DNA methylation and induced by key transcription factors of villous placental development during trophoblast fusion and differentiation. This latter mechanism arose via the co-option of binding sites for these transcription factors through promoter evolution and the insertion of an anthropoid-specific L1PREC2 transposable element into the 5' untranslated region of an ancestral gene followed by gene duplication events. Among placental Chr19 cluster galectin genes, the expression of LGALS13 and LGALS14 is down-regulated in preterm severe preeclampsia associated with SGA. We reveal that this phenomenon is partly originated from the dysregulated expression of key transcription factors controlling trophoblastic functions and galectin gene expression. In addition, the differential DNA methylation of these genes was also observed in preterm preeclampsia irrespective of SGA.

CONCLUSIONS

These findings reveal the evolutionary origins of the placental expression of Chr19 cluster galectins. The complex dysregulation of these genes in preeclampsia may alter immune tolerance mechanisms at the maternal-fetal interface.

Placental Protein 13 (PP13) - A Placental Immunoregulatory Galectin Protecting Pregnancy

Galectins are glycan-binding proteins that regulate innate and adaptive immune responses, and some confer maternal-fetal immune tolerance in eutherian mammals. A chromosome 19 cluster of galectins has emerged in anthropoid primates, species with deep placentation and long gestation. Three of the five human cluster galectins are solely expressed in the placenta, where they may confer additional immunoregulatory functions to enable deep placentation. One of these is galectin-13, also known as Placental Protein 13 (PP13). It has a "jelly-roll" fold, carbohydrate-recognition domain and sugar-binding preference resembling other mammalian galectins. PP13 is predominantly expressed by the syncytiotrophoblast and released from the placenta into the maternal circulation. Its ability to induce apoptosis of activated T cells in vitro, and to divert and kill T cells as well as macrophages in the maternal decidua in situ, suggests important immune functions. Indeed, mutations in the promoter and an exon of LGALS13 presumably leading to altered or non-functional protein expression are associated with a higher frequency of preeclampsia and other obstetrical syndromes, which involve immune dysregulation. Moreover, decreased placental expression of PP13 and its low concentrations in first trimester maternal sera are associated with elevated risk of preeclampsia. Indeed, PP13 turned to be a good early biomarker to assess maternal risk for the subsequent development of pregnancy complications caused by impaired placentation. Due to the ischemic placental stress in preterm preeclampsia, there is increased trophoblastic shedding of PP13 immunopositive microvesicles starting in the second trimester, which leads to high maternal blood PP13 concentrations. Our meta-analysis suggests that this phenomenon may enable the potential use of PP13 in directing patient management near to or at the time of delivery. Recent findings on the beneficial effects of PP13 on decreasing blood pressure due to vasodilatation in pregnant animals suggest its therapeutic potential in preeclampsia.

"Trophoblast islands of the chorionic connective tissue" (TICCT): a novel placental histologic feature

INTRODUCTION

We found isolated or clustered trophoblasts in the chorionic connective tissue of the extraplacental membranes, and defined this novel histologic feature as the "trophoblast islands of the chorionic connective tissue" (TICCT). This study was conducted to determine the clinical significance of TICCT.

METHODS

Immunohistochemistry for cytokeratin-7 was performed on the chorioamniotic membranes (N = 2155) obtained from singleton pregnancies of 1199 uncomplicated term and 956 preterm deliveries. The study groups comprised 1236 African-American and 919 Hispanic women. Gestational age ranged from 24(+0) weeks to 41(+6) weeks. Multiple logistic regression analysis was performed to investigate the magnitude of association between patient characteristics and the presence of TICCT.

RESULTS

The likelihood of TICCT was significantly associated with advancing gestational age both in term (OR: 1.29, 95% CI: 1.16-1.45, p < 0.001) and preterm deliveries (OR: 1.19, 95% CI: 1.07-1.32, p = 0.001) . Hispanic women were less likely than African-American women to have TICCT across gestation in term (OR: 0.23, 95% CI: 0.18-0.31, p < 0.001) and preterm pregnancies (OR: 0.41, 95% CI: 0.29-0.58, p < 0.001). Women with a female fetus were significantly more likely to have TICCT than women with a male fetus, in both term (OR: 1.64, 95% CI: 1.28-2.11, p < 0.001) and preterm gestations (OR: 2.04, 95% CI: 1.46-2.85, p < 0.001). TICCT was 40% less frequent in the presence of chronic placental inflammation [term (OR: 0.60, 95% CI: 0.45-0.81, p = 0.001) and preterm gestations (OR: 0.58, 95% CI: 0.40-0.84, p = 0.003)] and in parous women at term (OR: 0.60, 95% CI: 0.44-0.81, p = 0.001).

CONCLUSIONS

Our findings suggest that the duration of pregnancy, fetal sex, and parity may influence the behavior of extravillous trophoblast and placental mesenchymal cells.

IFPA Meeting 2012 Workshop Report II: epigenetics and imprinting in the placenta, growth factors and villous trophoblast differentiation, role of the placenta in regulating fetal exposure to xenobiotics during pregnancy, infection and the placenta

Workshops are an important part of the IFPA annual meeting as they allow for discussion of specialized topics. At IFPA meeting 2012 there were twelve themed workshops, four of which are summarized in this report. These workshops related to various aspects of placental biology: 1) epigenetics and imprinting in the placenta; 2) growth factors and villous trophoblast differentiation; 3) role of the placenta in regulating fetal exposure to xenobiotics during pregnancy; 4) infection and the placenta.

Placental protein 13 (PP13/galectin-13) undergoes lipid raft-associated subcellular redistribution in the syncytiotrophoblast in preterm preeclampsia and HELLP syndrome

OBJECTIVE

To investigate placental protein 13 (PP13) localization in relation to cytoskeleton and lipid rafts in preeclampsia and HELLP syndrome.

STUDY DESIGN

Placental cryosections from patients with preeclampsia and HELLP, and controls were stained for PP13, actin, PLAP (lipid raft marker), and CD71 (nonraft marker). BeWo cells exposed to stress conditions were stained for PP13 and actin. Protein localizations were investigated by confocal microscopy, PP13 concentrations by ELISA.

RESULTS

PP13-actin colocalization was increased in syncytiotrophoblast juxtamembrane regions in term/preterm preeclampsia and HELLP. PP13-CD71 colocalization was decreased and PP13-PLAP proximity was increased in preterm but not term preeclampsia and HELLP. PP13-release from BeWo cells was inhibited by cytoskeleton disruption, and augmented by Ca2+-influx and ischemic stress.

CONCLUSION

The actin cytoskeleton, probably in connection with lipid rafts, controls trophoblastic "nonclassical" PP13 export. PP13 is released from the syncytiotrophoblast in preterm preeclampsia and HELLP, mimicked in BeWo cells by ischemic stress, suggesting PP13 is a placental alarmin.

Microarray profiling reveals that placental transcriptomes of early-onset HELLP syndrome and preeclampsia are similar

BACKGROUND

The involvement of the placenta in the pathogenesis of preeclampsia and HELLP syndrome is well established, and placental lesions are also similar in these two syndromes. Here we aimed to examine the placental transcriptome and to identify candidate biomarkers in early-onset preeclampsia and HELLP syndrome.

METHODS

Placental specimens were obtained at C-sections from women with early-onset preeclampsia and HELLP syndrome, and from controls who delivered preterm or at term. After histopathological examination, fresh-frozen placental specimens were used for microarray profiling and validation by qRT-PCR. Differential expression was analysed using log-linear models while adjusting for gestational age. Gene ontology and pathway analyses were used to interpret gene expression changes. Tissue microarrays were constructed from paraffin-embedded placental specimens and immunostained.

RESULTS

Placental gene expression was gestational age-dependent among preterm and term controls. Out of the 350 differentially expressed genes in preeclampsia and 554 genes in HELLP syndrome, 224 genes (including LEP, CGB, LHB, INHA, SIGLEC6, PAPPA2, TREM1, and FLT1) changed in the same direction (elevated or reduced) in both syndromes. Many of these encode proteins that have been implicated as biomarkers for preeclampsia. Enrichment analyses revealed similar biological processes, cellular compartments and biological pathways enriched in early-onset preeclampsia and HELLP syndrome; however, some processes and pathways (e.g., cytokine-cytokine receptor interaction) were over-represented only in HELLP syndrome.

CONCLUSION

High-throughput transcriptional and tissue microarray expression profiling revealed that placental transcriptomes of early-onset preeclampsia and HELLP syndrome largely overlap, underlying a potential common cause and pathophysiologic processes in these syndromes. However, gene expression changes may also suggest a more severe placental pathology and pronounced inflammatory response in HELLP syndrome than in preeclampsia.

Leptin receptor (LEPR) SNP polymorphisms in HELLP syndrome patients determined by quantitative real-time PCR and melting curve analysis

Background

Several studies have shown overexpression of leptin in microarray experiments in pre-eclampsia (PE) and in hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome. We decided to study four leptin receptor (LEPR) SNP polymorphisms in HELLP syndrome patients by using quantitative real-time PCR and melting curve analysis.

Methods

DNA was isolated from blood samples from 83 normotensive pregnant women and 75 HELLP syndrome patients. Four SNPs, LEPR c.326A>G (K109), LEPR c.668A>G (Q223R), LEPR c.1968G>C (K656N) and LEPR c.3024A>G (S1008) were determined by quantitative real-time PCR and melting curve analysis. Investigators were blinded to clinical outcomes.

Results

LEPR c.326A>G, LEPR c.668A>G, LEPR c.1968G>C and LEPR c.3024A>G allele, genotype and haplotype polymorphisms were not different in HELLP syndrome patients and normotensive healthy pregnants. There were strong linkage disequilibrium (LD) between loci c.326A>G and c.6687A>G (D' = 0.974), and c.668A>G and c.1968G>C (D' = 0.934), and c.326A>G and c.1968G>C (D' = 0.885), and c.1968G>C and c.3024A>G (D' = 1.0). However, linkages of c.3024A>G with c.668A>G (D' = 0.111) and c.326A>G (D' = 0.398) were weak. The Hardy-Weinberg equilibrium was observed for all polymorphisms. However the LEPR c.326A>G AG genotype was twice more frequent and the (AG AG GG AG) haplotype was three times more frequent in HELLP syndrome patients. The introduced quantitative real-time PCR combined with melting curve analysis is a fast and reliable method for the determination of LEPR SNPs.

Conclusion

Although certain LEPR haplotypes are more frequent in HELLP syndrome, we conclude that there is no compelling evidence that the four studied LEPR SNP polymorphisms associated with the development of HELLP syndrome.

The effect of gestational age and labor on placental growth hormone in amniotic fluid

OBJECTIVE

Placental growth hormone (PGH) is produced by trophoblast. This hormone becomes detectable in maternal serum during the first trimester of pregnancy. Its concentration increases as term approaches and becomes undetectable within one hour of delivery. PGH has important biological properties, including somatogenic (growth promotion), lactogenic, and lipolytic activity. Recently, PGH has been detected in amniotic fluid (AF) of midtrimester pregnancies. The purpose of this study was to determine whether PGH concentrations in AF change with advancing gestational age and in labor at term.

DESIGN

AF was assayed for PGH concentrations in samples obtained from patients undergoing genetic amniocentesis between 14 and 18 weeks of gestation (n=67), normal patients at term not in labor (n=24), and pregnant women at term in labor (n=51). PGH concentrations were determined by ELISA. Non-parametric statistics were used for analysis.

RESULTS

(1) PGH was detected in all AF samples; (2) patients in the midtrimester had a higher median concentration of PGH in AF than those at term (midtrimester: median: 3140.5 pg/ml; range: 1124.2-13886.5 vs. term: median: 2021.1pg/ml; range: 181.6-8640.8; p<0.01); (3) there was no difference in the median concentration of PGH between women at term, not in labor, and those in labor (term not in labor: median: 2113.4pg/ml; range: 449.3-8640.8 vs. term in labor: median: 2004.1pg/ml; range: 181.6-8531.5; p=0.73).

CONCLUSIONS

(1) PGH is detectable in AF at both mid- and third trimesters; (2) the median AF concentration of PGH is significantly lower at term when compared to the second trimester; (3) labor at term is not associated with changes in the AF concentration of PGH. The role of this unique placental hormone now found in the fetal compartment requires further investigation.

Prediction of preeclampsia - a workshop report

Understanding the mechanisms of disease responsible for the syndrome of preeclampsia as well as early risk assessment is still a major challenge. The concentrations of circulating proteins in maternal blood such as placental growth factor, soluble vascular endothelial growth factor receptor-1 and soluble endoglin are altered weeks before the onset of clinical symptoms of the syndrome. Recently, other proteins in maternal serum, such as activin A, inhibin A, PAPP-A, and PP13 have been suggested to be of value in first trimester risk assessment. Since preeclampsia is a syndrome, it seems unlikely that a single test will predict all forms of preeclampsia. This realization has led to the formulation of a new conceptual framework suggesting that a combination of markers (biochemical and/or biophysical) may be required to conduct comprehensive risk assessment for the syndrome.

The use of high-dimensional biology (genomics, transcriptomics, proteomics, and metabolomics) to understand the preterm parturition syndrome

High-dimensional biology (HDB) refers to the simultaneous study of the genetic variants (DNA variation), transcription (messenger RNA [mRNA]), peptides and proteins, and metabolites of an organ, tissue, or an organism in health and disease. The fundamental premise is that the evolutionary complexity of biological systems renders them difficult to comprehensively understand using only a reductionist approach. Such complexity can become tractable with the use of "omics" research. This term refers to the study of entities in aggregate. The current nomenclature of "omics" sciences includes genomics for DNA variants, transcriptomics for mRNA, proteomics for proteins, and metabolomics for intermediate products of metabolism. Another discipline relevant to medicine is pharmacogenomics. The two major advances that have made HDB possible are technological breakthroughs that allow simultaneous examination of thousands of genes, transcripts, and proteins, etc., with high-throughput techniques and analytical tools to extract information. What is conventionally considered hypothesis-driven research and discovery-driven research (through "omic" methodologies) are complementary and synergistic. Here we review data which have been derived from: 1) genomics to examine predisposing factors for preterm birth; 2) transcriptomics to determine changes in mRNA in reproductive tissues associated with preterm labour and preterm prelabour rupture of membranes; 3) proteomics to identify differentially expressed proteins in amniotic fluid of women with preterm labour; and 4) metabolomics to identify the metabolic footprints of women with preterm labour likely to deliver preterm and those who will deliver at term. The complementary nature of discovery science and HDB is emphasised.

Cloning, sequencing, structural and molecular biological characterization of placental protein 20 (PP20)/human thiamin pyrophosphokinase (hTPK)

Full-length cDNAs of placental protein 20 (PP20) were cloned by screening a human placental cDNA library, which encode a 243 amino acid protein, identical to human thiamin pyrophosphokinase (hTPK) as confirmed by protein sequence analysis. Genomic alignment showed that the PP20/hTPK gene contains 9 exons. It is abundantly expressed in placenta, as numerous EST clones were identified. As thiamine metabolism deficiencies have been seen in placental infarcts previously, these indicate that PP20/hTPK may have a role in placental diseases. Analysis of the 1kb promoter region showed numerous putative transcription factor binding sites, which might be responsible for the ubiquitous PP20/hTPK expression. This may also be in accordance with the presence of the protein in tissues responsible for the regulation of the exquisite balance between cell division, differentiation and survival. TPK activity of the purified and recombinant protein was proved by mass spectrometry with electrospray ionization. By Western blot, PP20/hTPK was found in all human normal and tumorous adult and fetal tissues in nearly equal amounts, but not in sera. By immunohistochemical and immunofluorescent confocal imaging methods, diffuse labelling in the cytoplasm of the syncytiotrophoblasts and weak staining of the trophoblasts were observed, and the amount of PP20/hTPK decreased from the first trimester to the end of gestation. A 3D model of PP20/hTPK was computed (PDB No.: 1OLY) by homology modelling. A high degree of structural homology showed that the thiamin binding site was highly similar to that of the mouse enzyme, but highly different from the bacterial ones. Comparison of the catalytic centre sequences revealed differences, raising the possibility of designing new drugs which specifically inhibit bacterial and fungal enzymes without affecting PP20/hTPK and offering the possibility for safe antimicrobial therapy during pregnancy.

Extremely high maternal alkaline phosphatase serum concentration with syncytiotrophoblastic origin

An extremely high alkaline phosphatase (AP) concentration (3609 IU/litre) was found in a 20 year old primigravida at 37 week's gestation, prompting an examination of its histological and cellular origin. Immunohistochemistry and western blots using antibodies against AP, Ki-67, phospho-protein kinase B (Akt), phospho-p44/42 mitogen activated protein kinase/extracellular signal regulated kinase 1/2 (MAPK/Erk1/2), phospho-glycogen synthase kinase-3beta (GSK-3beta), phospho-stress activated protein kinase/c-Jun N-terminal kinase, total-Akt, total-GSK-3beta, and phospho-p38-MAPK were carried out on index and control placental samples of the same gestational age. Compared with controls, staining of the index placenta showed minimal AP labelling of the brush border and remarkable positivity of the intervillous space. Cytotrophoblastic proliferation was 8-10% in the index placenta compared with 1-2% in controls. The index placenta also had raised concentrations of protein kinases with important roles in cell differentiation. The proliferation and differentiation rates of the cytotrophoblasts were found to be five times higher in index samples than in controls. It is hypothesised that loss of syncytial membranes in immature villi led to increased AP concentrations in the maternal circulation and decreased AP staining of the placenta. Loss of the syncytium might also stimulate increased proliferation of villous cytotrophoblasts, which would then fuse and maintain the syncytium.

Homology modelling and molecular dynamics studies of human placental tissue protein 13 (galectin-13)

The primary structure of the newly sequence analysed placental tissue protein 13 (PP13) was highly homologous to several members of the beta-galactoside-binding S-type lectin (galectin) family. By homology modelling, the three-dimensional structure of PP13 was built based on high-resolution crystal structures of homologues and also their characteristic 'jellyroll' fold was found in the case of PP13. Our model has been deposited in the Brookhaven Protein Data Bank. By multiple sequence alignment and structure-based secondary structure prediction, we underlined the structural similarity of PP13 with its homologues. The secondary structure of PP13 was identical with 'proto-type' galectins consisting of a five- and a six-stranded beta-sheet, joined by two alpha-helices, and galectins' highly conserved carbohydrate-recognition domain (CRD) was also present in PP13. Of the eight consensus residues in the CRD, four identical and three conservatively substituted were shared by PP13. By docking simulations PP13 possessed sugar-binding activity with highest affinity to N-acetyllactosamine and lactose typical of most galectins. All ligands were docked into the putative CRD of PP13. Based on several lines of evidence discussed in this paper demonstrating that PP13 is a novel galectin, PP13 was also designated galectin-13. These computational results provide some new insights into the possible role and importance of PP13 in various processes of the human body and can be of help in the initial steps of further functional research.

Molecular cloning and characterization of placental tissue protein 18 (PP18a)/human mitochondrial branched-chain aminotransferase (BCATm) and its novel alternatively spliced PP18b variant

Five different insert-length cDNAs encoding for soluble placental tissue protein 18 (PP18) variants were isolated by screening a human placental cDNA library using monospecific anti-PP18 serum. Sequence analysis of the longest clone showed that the insert contains an open reading frame encoding for a 392 residue-long protein with a 27 amino acid mitochondrial targeting sequence. The mature protein-designated PP18a-is 41.264 kDa consisting of 365 residues and is identical to the previously isolated and characterized PP18 antigen described in 1985. We also found a new, alternatively spliced cDNA encoding for a 300 residue-long, 33.776 kDa protein, which was designated PP18b. Alignment search of the protein databank showed that PP18a is almost entirely identical to the human mitochondrial branched-chain aminotransferase, while PP18b is its newly discovered splicing variant. We detected the two PP18 variants in normal adult and fetal human tissues besides the mitochondrial (only PP18a) and cytosolic (only PP18b) fractions of term placenta with chemiluminescence Western blot analysis. The 41 kDa PP18a variant was expressed ubiquitously, while the 33 kDa PP18b variant was found in smaller amounts in nearly all tissues. Trace amounts of the variants were present in the sera of non-pregnant healthy controls, as well as in pregnant women, but there was no real change in serum levels during pregnancy. In conclusion, PP18 variants are not specific for the placenta. Aminotransferase activity of placental origin PP18 antigens was verified by structural analysis and by a coupled branched-chain aminotransferase/glutamate dehydrogenase assay.

Overexpression of placental tissue protein 17b/TIP47 in cervical dysplasias and cervical carcinoma

In our previous Western- and Northern-blot investigations, high over-expression of placental protein 17b/TIP47 was detected in extracts of human cervical carcinoma tissues compared to normal conditions of the cervical tissue. PP17b serum levels were also elevated in untreated cervical carcinoma patients compared to healthy controls. In the present study, the expression pattern of PP17 proteins was investigated in various cervical dysplasias and in cervical carcinoma tissue specimens by the streptavidin-biotin immunoperoxidase technique using PP17-specific antiserum. In normal third-trimester human placentas, which served as positive controls, mainly cytoplasmic PP17 immunostaining of syncytiotrophoblasts and chorionic trophoblasts was observed. Normal human uterine cervical squamous and glandular epithelia were negative or weakly positive, while in low grade dysplasias (CIN I-II) only the cytoplasms of dysplastic cells were weakly positive or positive; in high grade dysplasias (CIN III/ISC) cytoplasms of the dysplastic cells were strongly positive. Normal and superficial cells in the differentiated zones were negative in all tissue specimens. In cases of invasive epithelial cervical carcinomas, small basal-type tumour cells were mostly negative whilst cells with squamous differentiation were strongly positive for PP17. Our hypotheses for this newly detected phenomenon are briefly discussed.

Isolation and sequence analysis of a cDNA encoding human placental tissue protein 13 (PP13), a new lysophospholipase, homologue of human eosinophil Charcot-Leyden Crystal protein

Expression of placental tissue protein 13 (PP13) in different human tissues was investigated by chemiluminescence Western blot analysis using monospecific anti-PP13 serum. In term placentae we detected a 16 kDa single protein band immunochemically identical to the purified PP13 antigen. After investigation of 26 types of human fetal and adult tissue, PP13 was also found in certain other normal and tumorous tissue extracts. It is not secreted into circulation as we could not find PP13 in sera of pregnant women. A full length cDNA with 578 bp insert was isolated by screening a human placental cDNA library with anti-PP13 serum. The open reading frame of the cDNA encodes for a 139-residue-long protein with a predicted molecular mass of 16.118 kDa, identical to the previously isolated and characterized PP13 antigen described in 1983. By alignment search of the protein databank PP13 is highly homologous (69 per cent) to the 16.5 kDa human eosinophil Charcot-Leyden Crystal protein, a unique dual-function lysophospholipase, a member of the beta-galactoside binding S-type animal lectin superfamily. Northern blot analysis revealed a 600 bp PP13 mRNA, detected only in placental tissue from 16 types of human healthy adult tissue. Lysophospholipase activity of PP13 was confirmed by(1)H and(31)P nuclear magnetic resonance (NMR) measurements.

Is placental tissue protein 17b/TIP47 a new factor in cervical cancer genesis?

We identified novel members of the placental tissue protein 17 (PP17) protein family which consists of different-size variants of PP17; cDNAs of PP17a and PP17b variants have also been cloned and sequence analyzed. By Western-blot analysis in cervical carcinoma tissues we found overexpression of PP17b. Compared to healthy controls a mean five-fold increase in the amount of PP17b was also detected in the sera of untreated cervical carcinoma patients, which declined after radical operations. In our recent findings, in sera of inoperable cervical carcinoma patients, we also found elevated PP17b levels which did not change after irradiation. By Northern-blot analyses we confirmed PP17b overexpression in cervical carcinoma tissues and also the alternative splicing of PP17 mRNAs in various normal human tissues. Presently, the amino acid sequence of TIP47--a mannose-6-phosphate receptor cargo selection device--turned out to be identical to that of PP17b. Due to its oncodevelopmental function, PP17b/TIP47 is more than likely to be connected to HSV-2 infection, which is probably one of the main etiopathogenic agents of cervical carcinoma along with the HPV virus, and may open a new trend in the research of pathological processes in human uterine cervical cancer.

Cloning and sequencing of human oncodevelopmental soluble placental tissue protein 17 (PP17): homology with adipophilin and the mouse adipose differentiation-related protein

Using a monospecific anti-PP17 antiserum, we detected 4 different molecular-weight PP17 immunoreactive proteins (31,500 kD PP17a, 48, 000 kD PP17b, 60,900 kD PP17c and 74,000 kD PP17d) in different normal adult and fetal human tissues, and in term placenta, by chemiluminescence Western blot analysis. These proteins are overexpressed in cervix carcinoma tissue. Furthermore, increased amounts of PP17b are secreted into the circulation in cervix carcinoma patients; after radical surgery, PP17b serum levels are decreased, and the protein probably has an oncodevelopmental significance. cDNAs were isolated from a human placental cDNA library with the monospecific anti-PP17 antiserum. Sequence analysis of the clones showed that they encode for the 251 residue long PP17a variant, which is identical to the previously isolated and characterized PP17 antigen described in 1983. An alignment search of the protein databank showed that PP17a is homologous to human adipophilin and mouse adipose differentiation-related protein. PP17c turned out to be a dimer of PP17a, while PP17b and PP17d immunoreactive proteins recently detected on Western blots require further investigations.

Cloning and sequence analysis of cDNAs encoding human placental tissue protein 17 (PP17) variants

Using monospecific anti-PP17 serum with chemiluminescence Western-blot analysis, we detected different molecular-mass variants of human soluble placental tissue protein 17 (PP17) in different normal adult and fetal human tissues besides term placenta. 13 cDNAs with three different insert lengths encoding PP17 variants were isolated by screening a human placental cDNA library. Sequence analysis of the shortest clones showed that the inserts contain the same open reading frame encoding PP17a variant (28,129 kDa) consisting of 251 residues, which is identical to the previously isolated and characterised PP17 antigen described in 1983. The ubiquitous PP17b variant is encoded by longer clones and contains 434 residues with a predicted molecular mass of 47,208 kDa. Compared to normal conditions, these newly discovered PP17 variants are overexpressed in cervix carcinoma tissue, as are their three different-size messenger RNAs in HeLa cell line. Increased amounts of PP17b are secreted into the circulation in cervix carcinoma patients. We also observed a typical elevation in serum levels of PP17 variants during healthy pregnancy. An alignment search of the protein databank showed that PP17a and PP17b are homologous to adipose tissue differentiation and lipid-droplet-associated proteins: human adipophilin, mouse adipose differentiation-related protein and rat perilipin A and B.