Machiko Suzuki

Comparative gene expression profiling of placentas from patients with severe pre-eclampsia and unexplained fetal growth restriction

BackgroundIt has been well documented that pre-eclampsia and unexplained fetal growth restriction (FGR) have a common etiological background, but little is known about their linkage at the molecular level. The aim of this study was to further investigate the mechanisms underlying pre-eclampsia and unexplained FGR.MethodsWe analyzed differentially expressed genes in placental tissue from severe pre-eclamptic pregnancies (n = 8) and normotensive pregnancies with or (n = 8) without FGR (n = 8) using a microarray method.ResultsA subset of the FGR samples showed a high correlation coefficient overall in the microarray data from the pre-eclampsia samples. Many genes that are known to be up-regulated in pre-eclampsia are also up-regulated in FGR, including the anti-angiogenic factors, FLT1 and ENG, believed to be associated with the onset of maternal symptoms of pre-eclampsia. A total of 62 genes were found to be differentially expressed in both disorders. However, gene set enrichment analysis for these differentially expressed genes further revealed higher expression of TP53-downstream genes in pre-eclampsia compared with FGR. TP53-downstream apoptosis-related genes, such as BCL6 and BAX, were found to be significantly more up-regulated in pre-eclampsia than in FGR, although the caspases are expressed at equivalent levels.ConclusionsOur current data indicate a common pathophysiology for FGR and pre-eclampsia, leading to an up-regulation of placental anti-angiogenic factors. However, our findings also suggest that it may possibly be the excretion of these factors into the maternal circulation through the TP53-mediated early-stage apoptosis of trophoblasts that leads to the maternal symptoms of pre-eclampsia.

Increased levels of pregnancy-associated plasma protein-A2 in the serum of pre-eclamptic patients

Pregnancy-associated plasma protein-A and -A2 (PAPP-A and -A2) are proteases that cleave insulin-like growth factor-binding proteins (IGFBPs), resulting in local activation of IGF signaling pathways. Here, we examined PAPP-A and -A2 mRNA and protein levels in placenta and maternal sera from women with pre-eclampsia and compared them with samples from uncomplicated pregnancy. PAPP-A2 but not PAPP-A mRNA and protein were elevated in pre-eclamptic placenta (P < 0.01). PAPP-A2 is normally produced in placental syncytiotrophoblast cells and maternal decidua. PAPP-A2 in syncytiotrophoblast cells was dramatically increased in pre-eclampsia. Maternal serum concentrations of PAPP-A2 but not PAPP-A were also significantly elevated in pre-eclampsia as compared with uncomplicated pregnancy. mRNA levels of IGFBP5, a specific substrate for PAPP-A2 protease activity, were also significantly increased, suggesting a potential role for IGFBP5 in fetal and placental growth suppression during pre-eclampsia. However, IGFBP5 protein levels were not increased in placenta from pre-eclampsia, possibly due to cleavage by up-regulated PAPP-A2. These data might imply that PAPP-A2 may be up-regulated in pre-eclamptic pregnancy to compensate for IGFBP5-mediated suppression of the IGF pathway, although final birthweights are still low in pre-eclamptic pregnancy.

The etiological role of allogeneic fetal rejection in pre-eclampsia.

It has been demonstrated that allogeneic fetal rejection in normal pregnancy is prevented by placental indoleamine 2,3‐dioxygenase (IDO). Further, an immunological etiology has been implicated in pre‐eclampsia.

Mouse model for allogeneic immune reaction against fetus recapitulates human pre-eclampsia.

Aim:  We have previously demonstrated that mRNA expression and enzyme activity levels of placental indoleamine 2,3‐dioxygenase (IDO), which degrades L‐tryptophan and blocks the proliferation of T cells, are significantly low in patients with severe pre‐eclampsia. From this observation, we hypothesized that induction of maternal allogeneic immune reaction by reduced IDO activity is one of the causes of pre‐eclampsia.

Upregulation of HtrA4 in the placentas of patients with severe pre-eclampsia

High temperature requirement A (HtrA) family proteins are serine proteases that may serve in the quality control of misfolded or mislocalized proteins. Recently, possible involvements of HtrA1 in the normal development of the placenta and in the pathogenesis of pre-eclampsia were reported. In this study, we characterized HtrA4, a previously uncharacterized HtrA protein family member, in pre-eclampsia. Elevated expression levels of placental HtrA4 in pre-eclampsia patients were observed by qRT-PCR. Western blotting also showed an increased production of HtrA4 at the protein level in pre-eclamptic placentas. In normal chorionic villi, HtrA4 protein was more abundant in the cytoplasm of cytotrophoblasts than in syncytiotrophoblasts. In contrast, the amount of HtrA4 protein in syncytiotrophoblasts was dramatically increased in pre-eclamptic placentas. Circulating HtrA4 was detected at higher levels in sera from women with pre-eclampsia than from those with normotensive pregnancies. Serum HtrA4 levels were higher in patients with early onset and inversely correlated with the weights of the newborn and placenta. Furthermore, serum levels correlated with serum PAPP-A and PAPP-A2 levels, indicating a functional role for HtrA4 in the common pathway. These data suggest that increased HtrA4 may be involved in the onset of pre-eclampsia, and elevated levels in sera imply a potential application as a biomarker for this disorder.

Analysis of Nitric Oxide Metabolism as a Placental or Maternal Factor Underlying the Etiology of Pre-Eclampsia

Background:Defective nitric oxide (NO)-mediated vasodilation is widely regarded as an underlying cause of hypertension in pre-eclampsia, although there are also arguments against this hypothesis. Methods:We examined both the mRNA levels and the presence of a Glu298Asp substitution in the NO synthase (NOS) gene, as well as the NO metabolite concentration, in placentas and maternal sera from women with pre-eclampsia and in normotensive pregnant controls (25–40 vs. 24–41 weeks of gestation). Results:Pre-eclamptic and control placentas did not show any significant differences in their NO metabolite levels or their NOS expression levels as measured by quantitative RT-PCR. In addition, we did not find any association between pre-eclampsia and the occurrence of the Glu298Asp amino acid substitution in the NOS gene. In contrast, high maternal circulating NO metabolites were evident in severe pre-eclampsia (p < 0.0001). Although a positive correlation between circulating NO metabolites and blood pressure was not observed, uterine artery resistance measured by ultrasound was found to positively correlate with the maternal NO levels. Conclusions:Our current data suggest that an altered placental NOS pathway is unlikely to be the primary cause of pre-eclampsia and that the activation of this pathway is possibly in response to maternal symptoms.

Decreased expression of apelin in placentas from severe pre-eclampsia patients.

Objective: It is well documented that anti-angiogenic factors are likely to play essential roles in the etiology of pre-eclampsia. Apelin is a small peptide that may potentially act as an angiogenic factor. The expression of apelin was examined at the RNA and protein levels in this study. Methods: We compared the expression of apelin, examined using quantitative reverse-transcription polymerase chain reaction, western blotting, enzyme-linked immunosorbent assay and immunostaining, between pre-eclamptic patients and normotensive controls. Results: Apelin messenger RNA is significantly decreased in pre-eclamptic placentas compared with normotensive pregnancies (p < 0.05). Apelin protein levels are also lower in pre-eclamptic placentas than the controls but higher in the maternal circulation in pre-eclampsia patients. Immunohistochemical signals for apelin and its receptor APJ were detected mainly in the cytoplasm of syncytiotrophoblasts in chorionic villi and trophoblast-lineage cells in the decidua of term placentas. In early gestation, stronger APJ signals were observed at the cellular membrane. Conclusions: A functional role of the apelin--APJ system is likely in early gestation, and this raises the possibility that a dysfunctional apelin--APJ system contributes to the onset of pre-eclampsia via decreased angiogenic activity in placental implantation.

Genetic Variation in the Indoleamine 2,3‐Dioxygenase Gene in Pre‐eclampsia

Citation Nishizawa H, Kato T, Ota S, Nishiyama S, Pryor‐Koishi K, Suzuki M, Tsutsumi M, Inagaki H, Kurahashi H, Udagawa Y. Genetic variation in the indoleamine 2,3‐Dioxygenase gene in pre‐eclampsia. Am J Reprod Immunol 2010; 64: 68–76

A rare synaptonemal complex protein 3 gene variant in unexplained female infertility.

Synaptonemal complex protein 3 (SYCP3) plays a critical role in homologous chromosome pairing and recombination in meiosis, and mice deficient in this gene show infertility in males and subfertility in females. The aim of our current study was to determine whether genetic alterations in the SYCP3 gene are associated with female infertility in humans. We examined sequence variations of the SYCP3 gene in genomic DNA from 88 Japanese women with unexplained infertility and 165 samples obtained from a fertile control group. Case-control study using seven tagging single nucleotide polymorphisms revealed no significant association between common SYCP3 variants and unexplained infertility. However, only infertile women were homozygous for the minor allele of a novel rare variant in the coding region, c.666A>G (222Q>Q). The minor allele frequency was significantly higher in the infertile cohort (P< 0.05). This variant is predicted to create a cryptic splice site, although the expression of a mini-gene harboring the variant in HeLa cells or mouse testis did not demonstrate any effects on gene splicing. Our current findings therefore suggest that the c.666A>G variant in the SYCP3 gene might possibly contribute to female infertility in humans, although larger studies are needed to assess the possible effects of SYCP3 gene variation on human female infertility.

CD9 Gene Variations Are Not Associated with Female Infertility in Humans

Background/Aims: To determine whether genetic alterations in the CD9 gene are associated with female infertility in humans. Methods: We sequenced the entire coding region of this gene in 86 Japanese women with unexplained infertility and further conducted a case-control study of six tagging single nucleotide polymorphisms (SNPs) in this gene using an additional 164 samples obtained from a fertile control group. Results: No disease-causing mutation in the CD9 gene was evident in these samples and no significant association between the tagging SNPs and the studied cohort was identified. Conclusions: Our findings do not support the hypothesis that genetic alterations of the CD9 gene cause female infertility in humans.