Levels of placenta-specific tissue protein 12 (PP12) in serum during normal pregnancy and in patients with trophoblastic tumour

Further Evidence that an Episode of Premature Labor Is a Pathologic State: Involvement of the Insulin-Like Growth Factor System

INTRODUCTION

Approximately 47% of women with an episode of preterm labor deliver at term; however, their infants are at greater risk of being small for gestational age and for neurodevelopmental disorders. In these cases, a pathologic insult may disrupt the homeostatic responses sustaining pregnancy. We tested the hypothesis of an involvement of components of the insulin-like growth factor (IGF) system.

METHODS

This is a cross-sectional study in which maternal plasma concentrations of pregnancy-associated plasma protease (PAPP)-A, PAPP-A2, insulin-like growth factor-binding protein 1 (IGFBP-1), and IGFBP-4 were determined in the following groups of women: (1) no episodes of preterm labor, term delivery (controls, n = 100); (2) episode of preterm labor, term delivery (n = 50); (3) episode of preterm labor, preterm delivery (n = 100); (4) pregnant women at term not in labor (n = 61); and (5) pregnant women at term in labor (n = 61). Pairwise differences in maternal plasma concentrations of PAPP-A, PAPP-A2, IGFBP-1, and IGFBP-4 among study groups were assessed by fitting linear models on log-transformed data and included adjustment for relevant covariates. Significance of the group coefficient in the linear models was assessed via t-scores, with p < 0.05 deemed a significant result.

RESULTS

Compared to controls, (1) women with an episode of premature labor, regardless of a preterm or a term delivery, had higher mean plasma concentrations of PAPP-A2 and IGFBP-1 (each p < 0.05); (2) women with an episode of premature labor who delivered at term also had a higher mean concentration of PAPP-A (p < 0.05); and (3) acute histologic chorioamnionitis and spontaneous labor at term were not associated with significant changes in these analytes.

CONCLUSION

An episode of preterm labor involves the IGF system, supporting the view that the premature activation of parturition is a pathologic state, even in those women who delivered at term.

Epigenetic Dysregulation of Trophoblastic Gene Expression in Gestational Trophoblastic Disease

Gestational trophoblastic diseases (GTDs) have not been investigated for their epigenetic marks and consequent transcriptomic changes. Here, we analyzed genome-wide DNA methylation and transcriptome data to reveal the epigenetic basis of disease pathways that may lead to benign or malignant GTDs. RNA-Seq, mRNA microarray, and Human Methylation 450 BeadChip data from complete moles and choriocarcinoma cells were bioinformatically analyzed. Paraffin-embedded tissues from complete moles and control placentas were used for tissue microarray construction, DNMT3B immunostaining and immunoscoring. We found that DNA methylation increases with disease severity in GTDs. Differentially expressed genes are mainly upregulated in moles while predominantly downregulated in choriocarcinoma. DNA methylation principally influences the gene expression of villous trophoblast differentiation-related or predominantly placenta-expressed genes in moles and choriocarcinoma cells. Affected genes in these subsets shared focal adhesion and actin cytoskeleton pathways in moles and choriocarcinoma. In moles, cell cycle and differentiation regulatory pathways, essential for trophoblast/placental development, were enriched. In choriocarcinoma cells, hormone biosynthetic, extracellular matrix-related, hypoxic gene regulatory, and differentiation-related signaling pathways were enriched. In moles, we found slight upregulation of DNMT3B protein, a developmentally important de novo DNA methylase, which is strongly overexpressed in choriocarcinoma cells that may partly be responsible for the large DNA methylation differences. Our findings provide new insights into the shared and disparate molecular pathways of disease in GTDs and may help in designing new diagnostic and therapeutic tools.

The maternal plasma proteome changes as a function of gestational age in normal pregnancy: a longitudinal study

OBJECTIVE

Pregnancy is accompanied by dramatic physiological changes in maternal plasma proteins. Characterization of the maternal plasma proteome in normal pregnancy is an essential step for understanding changes to predict pregnancy outcome. The objective of this study was to describe maternal plasma proteins that change in abundance with advancing gestational age and determine biological processes that are perturbed in normal pregnancy.

STUDY DESIGN

A longitudinal study included 43 normal pregnancies that had a term delivery of an infant who was appropriate for gestational age without maternal or neonatal complications. For each pregnancy, 3 to 6 maternal plasma samples (median, 5) were profiled to measure the abundance of 1125 proteins using multiplex assays. Linear mixed-effects models with polynomial splines were used to model protein abundance as a function of gestational age, and the significance of the association was inferred via likelihood ratio tests. Proteins considered to be significantly changed were defined as having the following: (1) >1.5-fold change between 8 and 40 weeks of gestation; and (2) a false discovery rate-adjusted value of P < .1. Gene ontology enrichment analysis was used to identify biological processes overrepresented among the proteins that changed with advancing gestation.

RESULTS

The following results were found: (1) Ten percent (112 of 1125) of the profiled proteins changed in abundance as a function of gestational age; (2) of the 1125 proteins analyzed, glypican-3, sialic acid-binding immunoglobulin-type lectin-6, placental growth factor, C-C motif-28, carbonic anhydrase 6, prolactin, interleukin-1 receptor 4, dual-specificity mitogen-activated protein kinase 4, and pregnancy-associated plasma protein-A had more than a 5-fold change in abundance across gestation (these 9 proteins are known to be involved in a wide range of both physiological and pathological processes, such as growth regulation, embryogenesis, angiogenesis immunoregulation, inflammation etc); and (3) biological processes associated with protein changes in normal pregnancy included defense response, defense response to bacteria, proteolysis, and leukocyte migration (false discovery rate, 10%).

CONCLUSION

The plasma proteome of normal pregnancy demonstrates dramatic changes in both the magnitude of changes and the fraction of the proteins involved. Such information is important to understand the physiology of pregnancy and the development of biomarkers to differentiate normal vs abnormal pregnancy and determine the response to interventions.

Phosphoisoforms of insulin-like growth factor binding protein-1 in appropriate-for-gestational-age and small-for-gestational-age fetuses

We analysed phosphoisoforms of insulin-like growth factor binding protein-1 (IGFBP-1) in maternal and cord sera from preterm and term fetus with different growth status. Phosphoisoforms were separated by non-SDS-polyacrylamide gel electrophoresis and detected by immunoblot. Phosphoisoforms were also analysed by anion exchange chromatography on HPLC. The proportion of non-phosphorylated IGFBP-1 to total IGFBP-1 was significantly higher in preterm fetus than in their mothers, however, the relative amounts of each IGFBP-1 isoforms were similar between preterm and term fetus. The levels of non-phosphorylated IGFBP-1 were similar between appropriate for gestational age (AGA) and small for gestational age (SGA) fetus at term, however, phosphorylated isoforms of IGFBP-1 were increased in SGA fetus compared to those of AGA fetus and the proportion of non-phosphorylated IGFBP-1 to total IGFBP-1 was lower in SGA fetus than those in AGA fetus. Thus, the profiles of non-phosphorylated and phosphorylated IGFBP-1 in the fetus varies corresponding to fetal growth suggesting that not only total amounts of IGFBP-1 but also the proportion of phosphoisoforms of IGFBP-1 is important for fetal growth.

Phosphorylated insulin-like growth factor (IGF)-binding protein-1 (IGFBP-1) inhibits while non-phosphorylated IGFBP-1 stimulates IGF-I-induced amino acid uptake by cultured trophoblast cells

The effects of phosphorylated insulin-like growth factor-binding protein (pIGFBP-1) and non-phosphorylated (npIGFBP-1) IGFBP-1 on amino acid uptake induced by IGF-I were studied using cultured trophoblast cells. Trophoblast cells obtained from term pregnancy were incubated with indicated concentrations of pIGFBP-1 or npIGFBP-1 for 24 h and further incubated with 10 nM IGF-I for 3 h. Cells were then incubated with 3H-alpha-amino isobutyric acid (3H-AIB) for 30 min. Both pIGFBP-1 and npIGFBP-1 alone had no effect on 3H-AIB uptake; however, pIGFBP-1 inhibited IGF-I-stimulated 3H-AIB uptake with an ED50 of 0.26 nM while npIGFBP-1 potentiated 3H-AIB uptake with an ED50 of 0.27 nM. Maternal IGF-I promotes fetal growth by stimulating nutrient transport in the placenta. As shown in this study, pIGFBP-1 inhibits while npIGFBP-1 stimulates this IGF-I action in the placenta. Thus, it is suggested that IGFBP-1 phosphoisoforms are also involved in fetal growth by modulating IGF-I action in the placenta.

Insulin-related growth factor binding protein-1 levels in ovum donation pregnancies

The finding that endometrial maturation may be delayed following hormone replacement therapy has suggested that a generalised endometrial dysfunction may exist in ovum recipients. In order to investigate this suggestion further, circulating levels of IGFBP-1 were measured in samples taken throughout pregnancies conceived either spontaneously or following ovum donation. When analysed at two-weekly intervals, the serum levels of IGFBP-1 in ovum donation pregnancies failed to show the expected peak towards the end of the first trimester and were significantly reduced at week ten (U = 364.5, p = 0.0002) and twelve (U = 138.0, p = 0.0047). For the remainder of pregnancy, circulating IGFBP-1 levels were similar in both groups. The birth weight of children born to the ovum donation group was not significantly different from a normal control group, suggesting that circulating levels of IGFBP-1 in early pregnancy do not reflect local function and that IGFBP-1 does not have an essential function (in relation to birth weight) in early pregnancy.

Secretory proteins of the endometrium--potential markers for endometrial dysfunction

In contrast to our detailed knowledge of endometrial structure, the study of endometrial function is still in its infancy. It seems likely that most of the changes that occur in the endometrium during the cycle are directed towards the promotion of implantation, and that the proteins secreted by the tissue have a role to play in the maintenance of pregnancy. One approach to the study of these proteins has been the incubation of endometrium in vitro with labelled amino acid precursors, and this method has revealed that in early pregnancy two proteins are quantitatively more important than the others synthesized and secreted by the endometrium. One of these proteins is a homologue of beta-lactoglobulin, also known as alpha 2-PEG, PP14 or PEP. It is synthesized by endometrial glands and no other source has been identified. Its synthesis is induced in the luteal phase of the menstrual cycle, rises to a peak in the early weeks of pregnancy and then rapidly declines as the decidua spongiosa is replaced by decidua compacta. The direction of its secretion appears to be into the amniotic fluid, and its function may be to transport a vitamin or other essential substance to the early conceptus: another possible function is immunosuppression. The protein can be measured in peripheral blood and may be useful as a marker of the effect of progesterone-or its lack of effect, as in the inadequate luteal phase. The other quantitatively important endometrial protein is IGF binding protein, which is produced mainly by stromal fibroblasts in the late luteal phase of the cycle. During the cycle the contribution of the endometrium to serum levels of IGF-BP is slight, but in pregnancy, as the amount of decidua compacta increases, levels in peripheral blood rise, with peaks at 18-24 weeks and at 36-40 weeks. The function of the protein may be to protect the mother by inhibiting IGF, or to enable IGF to stimulate the growth of endometrial stroma. Links between this protein and disorders of fetal growth have been suggested. The diversity of the possible functions of these proteins, and the continuing uncertainty over their roles, underline the complexity of endometrial functions.(ABSTRACT TRUNCATED AT 400 WORDS)

Placental protein 12 (PP 12), a decidual protein, in pregnancy complicated by diabetes with retinopathy

Placental protein 12 (IGF-bp/PP 12) is a soluble tissue antigen produced in the decidua. PP 12 was measured in the 3rd trimester of diabetic pregnancy complicated by retinopathy. The mean values of the healthy control group between 28 and 34 and between 35 and 39 weeks gestation were 108 +/- 39 micrograms/l and 124 +/- 47 micrograms/l, respectively. The equivalent values in diabetic pregnancies complicated by retinopathy were 200 +/- 80 micrograms/l and 204 +/- 81 micrograms/l, respectively; both these PP 12 values were significantly (P less than 0.05) above the values in the control group. There was no significant difference between benign and proliferative retinopathy. The increased PP 12 levels in the presence of diabetic retinopathy are probably caused by decidual degeneration.

Serum PP12, PP14, SP1 and hCG values in the 28 days after the LH-surge in patients who do and do not conceive after artificial insemination or in vitro fertilization

Serum levels of PP12 (somatomedin binding protein), PP14 (beta lactoglobulin homologue), Schwangerschaftsprotein 1 (SP1) and of human chorionic gonadotropin (hCG) were simultaneously measured in patients being treated for infertility in the 28 days after the LH-surge. PP14 levels were similar in the 14 days after the LH-surge in the patients who conceived when compared with those who did not and a high PP14 level was only indicative of pregnancy at 21 days after the LH-surge. hCG and SP1 levels behaved similarly in pregnant subjects. PP12 levels did not change significantly in the 28-days after the LH-surge.

Beta lactoglobulin homologue placental protein 14 (PP14) in serum of patients with trophoblastic disease and non-trophoblastic gynecologic malignancy

Serum levels of beta lactoglobulin homologue placental protein 14 (PP14) were measured by a sensitive radioimmunoassay in various trophoblastic diseases and non-trophoblastic gynecologic malignancies. While trace amounts of protein were detected in sera of non-pregnant subjects (22.3 +/- 13.7 micrograms/l), during first half of normal pregnancy a dramatic rise of serum-PP14 levels was demonstrable with a peak-value at 7th-10th week of gestation, followed by a decline thereafter. Serial determinations of PP14 have been performed in 31 patients with trophoblastic tumour (20 hydatidiform moles, 4 invasive moles and 7 choriocarcinomas). In patients with hydatidiform moles and invasive moles (273.5 +/- 106.5 micrograms/l and 162.2 +/- 109.6 micrograms/l) respective values before therapy were much exceeding the non-pregnant controls. After therapy there was a rapid decline of the serum-PP14 levels within two weeks. In patients with choriocarcinoma the PP14 values were moderately elevated (66.4 +/- 25.7 micrograms/l), and declined following the remission of disease. In 32 gynecological tumours (21 carcinomas of the cervix, 4 endometrial carcinomas, 5 ovarian carcinomas, 2 carcinomas of the vulva) the pretreatment levels were not different to normal controls.

New placental proteins: chemistry, physiology and clinical use

In the past decade, several new placental proteins have been isolated and studied. The 'pregnancy-specific' beta 1-glycoprotein (SP1) is a major placental product with unusual physicochemical properties that has been extensively investigated, but its biological function remains uncertain. Pregnancy-associated plasma protein A (PAPP-A), a glycoprotein of mol. wt 400,000, has effects in vitro on the coagulation and complement cascades, probably by its properties of protease inhibition. Placental protein 5 (PP5) may be involved in the coagulation and fibrinolytic systems, and in follicle maturation and semen liquefaction. 'Placental protein 12' (PP12) is not a product of the placenta at all; it appears to be produced in the female genital tract under the influence of progesterone and may also be produced by proliferating liver cells. Further study may reveal new roles for these placental proteins beyond their traditional roles as tumour markers.

Placental protein 12 (PP12): a new test for the prediction of the small-for-gestational-age infant

The circulating levels of placental protein 12 (PP12) and placental lactogen (hPL) were measured in 501 women between 36 and 41 weeks gestation. There was a significant positive association between hPL levels and infant birthweight and a significant negative association in the case of PP12 levels. The clinical efficiency of elevated PP12 levels in the prediction of low-birthweight infant at term compared favourably with that of reduced hPL levels.

Serum levels of placenta-specific tissue protein 12 (PP12) in pregnancies complicated by pre-eclampsia, diabetes or twins

PP12 is one of the recently discovered soluble tissue antigens of the placenta. During normal pregnancy maternal serum PP12 levels rise during the first 18 weeks reaching a mean peak value of 139.9 +/- 40.26 micrograms/l; after that there is a fall to a mean value of 111.9 +/- 42.39 micrograms/l between 28 and 40 weeks. Significantly higher mean serum PP12 levels were found in the third trimester in two high risk pregnancy groups (281.09 +/- 117.08 micrograms/l in pre-eclamptic toxaemia and 203.71 +/- 73.77 micrograms/l in diabetes) while serum PP12 levels remained normal (114.94 +/- 58.06 micrograms/l) in twin pregnancy. The increase of serum PP12 concentration in toxaemia and in diabetes may be of considerable diagnostic significance.