Chiara Mandò

Epigenetic modulation of the IGF2/H19 imprinted domain in human embryonic and extra-embryonic compartments and its possible role in fetal growth restriction

Genomic imprinting, resulting in parent-of-origin-dependent gene expression, is mainly achieved by DNA methylation. IGF2 and H19, belonging to the same cluster of imprinted genes and regulated by ICR1, DMR2 and H19 promoter elements, play a major role in fetal/placental growth. Using quantitative approaches, we explored the epigenetic modulation of IGF2/H19 during human development in 60 normal and 66 idiopathic IUGR (Intrauterine Growth Restriction) pregnancies, studying embryonic (cord blood) and extraembryonic (placenta and umbilical cord) tissues. We found ICR1 normal methylation levels (~50%) and H19 promoter/DMR2 hypomethylation in extra-embryonic tissues. In contrast, in embryonic samples the three loci displayed normal methylation values comparable to those in postnatal blood. This feature is stably maintained throughout gestation and does not vary in IUGR cases. We reported asymmetric allelic expression of H19 and IGF2 as a common feature in pre- and post-natal tissues, independent of H19 promoter and DMR2 methylation levels. In addition, we excluded in IUGR posttranscriptional IGF2 interference possibly related to miRNA 483-3p (IGF2, intron 2) expression defects. Through LINE1 methylation analysis, we observed a methylation gradient with increasing methylation from pre- to post-natal life. The involvement of UPD (Uniparental Disomy) in IUGR aetiology was excluded. Our data indicate that: i) ICR1 3 methylation status is a necessary and sufficient condition to drive the imprinting of IGF2 and H19 present in embryonic as well as in extra-embryonic tissues; ii) hypomethylation of H19 promoter and DMR2 does not influence the expression pattern of IGF2 and H19; iii) there is a gradient of global methylation, increasing from extra-embryonic to embryonic and adult tissues. Finally, because of placental hypomethylation, cautions should be exercised in diagnosis of imprinting diseases using chorionic villi.

Maternal predictors of intrauterine growth restriction.

Purpose of review Intrauterine growth restriction (IUGR) occurs when fetal growth rate falls below the genetic potential and affects a significant number of pregnancies, but still no therapy has been developed for this pregnancy disease. This article reviews the most recent findings concerning maternal characteristics and behaviours predisposing to IUGR as well as maternal early markers of the disease. A comprehensive understanding of factors associated with IUGR will help in providing important tools for preventing and understanding adverse outcomes. Recent findings Maternal nutritional status, diet and exposure to environmental factors are increasingly acknowledged as potential factors affecting fetal growth both by altering nutrient availability to the fetus and by modulating placental gene expression, thus modifying placental function. Summary Assessing nutritional and environmental factors associated with IUGR, and the molecular mechanisms by which they may have a role in the disease onset, is necessary to provide comprehensive and common guidelines for maternal care and recommended behaviours. Moreover, maternal genetic predispositions and early serum markers may allow a better and more specific monitoring of high risk pregnancies, optimizing the timing of delivery.

Maternal blood mitochondrial DNA content during normal and intrauterine growth restricted (IUGR) pregnancy.

OBJECTIVE We investigated mitochondrial DNA (mtDNA) content in the maternal circulation of normal pregnancies of different gestational ages and in pregnancies complicated by intrauterine growth restriction (IUGR). STUDY DESIGN We examined 70 maternal blood samples: 13 nonpregnant women; 45 normal pregnancies, divided into the 3 trimesters; and 12 pregnancies complicated by IUGR. MtDNA content was determined by real-time quantitative polymerase chain reaction, using a genomic control and a target gene. RESULTS A highly significant progressive reduction in circulating mtDNA was observed in pregnant women of first, second, and third trimesters and compared to nonpregnant women (mean value: 237, 188, 144, and 283, respectively; P < .001). Moreover, mtDNA was significantly increased in women carrying IUGR fetuses compared to women with normal pregnancies (430 vs 144; P < .001). CONCLUSION MtDNA could provide new insight into the mechanisms that occur during physiological gestation. Furthermore, mtDNA content may help recognize the IUGR disease in pregnancy.

Placental Iron Transport and Maternal Absorption

The iron need in pregnancy is significantly higher in comparison to that in the nonpregnant state. The iron absorbed during pregnancy is used for expansion of the maternal erythrocyte mass, to fulfill the fetus’s iron needs, to create placenta, and to cope with blood loss at delivery. Term neonates have a total body store of about 1 g of iron, all derived from the mother. Despite the overall increase in nutritional requirements, biochemical, metabolic, and physiological adjustments of the maternal organism happen in order to meet the extra demands and to support the homeostasis of iron. In all healthy pregnant women with sufficient iron stores, the increased iron absorption is coupled with the mobilization of iron stores. Unfortunately, iron deficiency during pregnancy is alarmingly common. The function of placental transport determines the composition of umbilical cord blood providing nutrients and oxygen to the fetus to ensure appropriate fetal growth. Iron in the developing fetus is accumulated against a concentration gradient and, in the case of maternal iron deficiency, the placenta can protect the fetus significantly through the increased expression of placental transferrin receptor together with a rise in divalent metal transporter 1 (DMT1). Despite the resistance of the fetus to maternal deficiency, any stress that alters placental development or function may have consequences for the developing fetus. Despite its central importance in fetal development, little is known about the mechanism of iron transfer across the placenta. Consequently, it is crucial to understand the molecular basis of placental iron transport in order to optimize the iron intake recommendation, reducing adverse pregnancy outcomes for both the mother and her child.

Angiotensin-Converting Enzyme and Adducin-1 Polymorphisms in Women With Preeclampsia and Gestational Hypertension

The angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism and the Adducin-1 (ADD1) G460W nonsense single nucleotide polymorphism (SNP) have previously been associated to hypertension, whereas their association with preeclampsia (PE) and gestational hypertension (GH) is still controversial. We genotyped ACE I/D, ADD1 G460W, and ADD1 S586C polymorphisms in 672 unrelated pregnant women: 204 PE (81/204 mild PE), 56 GH, and 412 controls, evaluating both their single and combined effects on these pathologies. The genotype combination of the 3 polymorphisms was not statistically different in cases versus controls, nor were ACE and ADD1 polymorphisms in GH. Nevertheless, the distribution of ACE genotypes was different in PE. This was confirmed in mild PE, whereas no significance was found in severe PE. This could suggest that different factors may lead to mild and severe PE, with ACE polymorphism playing a more important role in the mild form.

Placental fatty acid transport in maternal obesity

Pregestational obesity is a significant risk factor for adverse pregnancy outcomes. Maternal obesity is associated with a specific proinflammatory, endocrine and metabolic phenotype that may lead to higher supply of nutrients to the feto-placental unit and to excessive fetal fat accumulation. In particular, obesity may influence placental fatty acid (FA) transport in several ways, leading to increased diffusion driving force across the placenta, and to altered placental development, size and exchange surface area. Animal models show that maternal obesity is associated with increased expression of specific FA carriers and inflammatory signaling molecules in placental cotyledonary tissue, resulting in enhanced lipid transfer across the placenta, dislipidemia, fat accumulation and possibly altered development in fetuses. Cell culture experiments confirmed that inflammatory molecules, adipokines and FA, all significantly altered in obesity, are important regulators of placental lipid exchange. Expression studies in placentas of obese-diabetic women found a significant increase in FA binding protein-4 expression and in cellular triglyceride content, resulting in increased triglyceride cord blood concentrations. The expression and activity of carriers involved in placental lipid transport are influenced by the endocrine, inflammatory and metabolic milieu of obesity, and further studies are needed to elucidate the strong association between maternal obesity and fetal overgrowth.

SNAT2 expression and regulation in human growth-restricted placentas

Background:Amino acid placental delivery is reduced in human intrauterine growth–restricted (IUGR) fetuses, and the activity of placental amino transporters has been consistently shown to be decreased in in vitro studies. We hypothesized lower placental expression and localization of sodium-coupled neutral amino acid transporter 2 (SNAT2 (also known as SLC38A2)), altered levels of intron-1 methylation, and altered distribution of single-nucleotide polymorphisms in human IUGR vs. normal pregnancies.Methods:We studied 88 IUGR and 84 control placentas from singleton pregnancies at elective caesarean section. SNAT2 expression was investigated by real-time PCR and immunohistochemistry. Intron-1 methylation levels were analyzed by pyrosequencing, and single-nucleotide polymorphism distribution was analyzed by allelic discrimination.Results:mRNA levels were significantly decreased in IUGR placentas with reduced umbilical blood flows. Syncytiotrophoblast immunostaining was lower in IUGR placentas than in control placentas. Methylation levels were steadily low in both IUGR and control placentas. SNP genotype and allele frequencies did not differ between the two groups.Conclusion:This is the first study investigating SNAT2 expression and regulation mechanisms in human IUGR placentas. We confirm previous results obtained in rats and cell cultures that support the fundamental role of SNAT2 in fetal growth and well-being, as well as a possible role of oxygen levels in regulating SNAT2 expression, indicating the relevance of hypoxia in IUGR.

Sex specific adaptations in placental biometry of overweight and obese women

INTRODUCTION Placental biometry at birth has been shown to predict chronic disease in later life. We hypothesized that maternal overweight/obesity, a state of low-grade inflammation and risk factor for adverse pregnancy outcome, could negatively influence placental development and that differences would be sex-specific. METHODS 696 women (537 normal-weight, NW; 112 overweight, OW; 47 obese, OB) with singleton uncomplicated pregnancies were prospectively enrolled at term delivery. Gestational age, maternal (age, height, pre-pregnancy BMI, gestational weight gain -GWG, hemoglobin, hematocrit and glycemia), fetal (weight, length, ponderal index, cranial circumference) and placental (weight, diameters) data were collected. Placental area, thickness and efficiency (fetal/placental weight ratio, F/P) were calculated. RESULTS GWG was within standard recommendations in OB, while OW exceeded it. Placental weight was significantly higher in OW versus NW, but not in OB, leading to significantly higher placental thickness and lower F/P in this group. In the total population, a significant interaction effect between maternal BMI and fetal sex on placental weight and efficiency was found. Indeed, differences in placental parameters were present only in female offspring. DISCUSSION In our population of OW and OB uncomplicated pregnancies only OW women, presenting GWG over standard recommendations, had thicker and less efficient placentas. We also reported different placental adaptation depending on fetal sex, with significant changes only in female fetuses. This may be part of a female-specific strategy aiming to ensure survival if another adverse event occurs. Customized counseling according to maternal BMI and fetal sex should be evaluated in clinical care.

Effects of different regimens of iron prophylaxis on maternal iron status and pregnancy outcome: a randomized control trial

Abstract Purpose: Iron supplementation is associated with side effects and overload risk. We compared different regimens of iron supplementation on maternal hematological status and pregnancy outcome in a cohort of healthy pregnant women. Materials and methods: Eighty non-anemic women with a normal singleton pregnancy were recruited at 11–13 weeks and randomized into controls (C; n = 20) and groups supplemented with ferrous iron 30 mg (FI; n = 20), liposomal iron 14 mg (Sideral® Pharmanutra, Pisa PI, Italy) (LI14; n = 20) and liposomal iron 28 mg/daily (LI28; n = 20) up to 6 weeks post-partum. Longitudinal maternal blood samples for iron markers were collected. Data on birth outcome were recorded. The treatment effect was evaluated using a mixed-effect regression model. Results: Both LI28 and LI14 groups showed significantly higher hemoglobin and ferritin concentrations compared with controls. Birth weight showed a trend to increase with supplementation, resulting in higher birth weight in the LI28 group compared with controls (3499 ± 464.1 g and 3092 ± 469.5 g, respectively, p < 0.01). Conclusions: Our data show the effectiveness of 28 mg and 14 mg LI on maternal anemia prevention, as previously reported with FI 40 mg. LI has similar effects of higher doses of ferrous iron on maternal hematological parameters, thus allowing to reduce iron doses and side effects.

Impaired Angiogenic Potential of Human Placental Mesenchymal Stromal Cells in Intrauterine Growth Restriction

Human placental mesenchymal stromal cells (pMSCs) have never been investigated in intrauterine growth restriction (IUGR). We characterized cells isolated from placental membranes and the basal disc of six IUGR and five physiological placentas. Cell viability and proliferation were assessed every 7 days during a 6‐week culture. Expression of hematopoietic, stem, endothelial, and mesenchymal markers was evaluated by flow cytometry. We characterized the multipotency of pMSCs and the expression of genes involved in mitochondrial content and function. Cell viability was high in all samples, and proliferation rate was lower in IUGR compared with control cells. All samples presented a starting heterogeneous population, shifting during culture toward homogeneity for mesenchymal markers and occurring earlier in IUGR than in controls. In vitro multipotency of IUGR‐derived pMSCs was restricted because their capacity for adipocyte differentiation was increased, whereas their ability to differentiate toward endothelial cell lineage was decreased. Mitochondrial content and function were higher in IUGR pMSCs than controls, possibly indicating a shift from anaerobic to aerobic metabolism, with the loss of the metabolic characteristics that are typical of undifferentiated multipotent cells.