Development of the placental villous tree and its consequences for fetal growth

Diagnosing placental membrane hypoxic lesions increases the sensitivity of placental examination

CONTEXT

Two relatively unknown and recently described placental membrane hypoxic lesions (laminar necrosis and microscopic chorionic pseudocysts) have never been compared with time-honored, focal (infarction), and diffuse hypoxic lesions of placental parenchyma.

OBJECTIVE

To compare the effect on placental diagnosis of the above placental membrane hypoxic lesions and chorionic disc hypoxic lesions (infarctions and global hypoxic pattern of placental injury).

DESIGN

Twenty-three clinical (maternal and fetal) and 32 gross and microscopic placental features were retrospectively compared in 4590 placentas from a placental database built during a 13-year period: 168 placentas with at least one hypoxic disc lesion (infarct or global hypoxia) and at least one membrane lesion (microscopic chorionic pseudocysts or laminar necrosis (group 1), 750 placentas with at least one hypoxic villous lesion but no membrane lesion (group 2), 480 placentas with at least one membrane lesion but no villous lesion (group 3), and 3192 placentas with no hypoxic villous or membrane lesions (group 4).

RESULTS

Several clinical and fetal conditions and placental features known to be associated with in utero hypoxia had a statistically significant correlation with the index hypoxic placental lesions, both villous and membranous. Of placentas from patients associated with clinical conditions at risk for hypoxia, 15% featured only hypoxic membrane lesions without a chorionic disc hypoxic lesion.

CONCLUSIONS

Recognizing placental membrane hypoxic lesions increases the sensitivity of placental examination in diagnosing placental hypoxia by at least 15%. The risk of in utero hypoxia is increased when microscopic chorionic pseudocysts and laminar necrosis occur in conjunction with villous hypoxic lesions.

EPIGENETIC PROGRAMMING AND FETAL GROWTH RESTRICTIONS

Normal fetal growth and development depends on multiple molecular mechanisms that coordinate both placental and fetal development. Efforts to better understand fetal/placental growth dysregulation and fetal growth restriction (FGR) are now being driven by several findings that highlight the longterm impact of FGR on susceptibility to disease. The association of poor fetal growth to perinatal medical complications is well accepted but more recent data also show that FGR is linked to common, serious adult health problems. Several large-scale human epidemiological studies from diverse countries have shown that conditions such as coronary heart disease, hypertension, stroke, type 2 diabetes mellitus, adiposity, insulin resistance and osteoporosis are more prevalent in individuals with a history of low birthweight.

eNOS, NO, and the activation of ERK and AKT signaling at mid-gestation and near-term in an ovine model of intrauterine growth restriction

Intrauterine growth restriction (IUGR) is a disease responsible for neonatal morbidity and mortality and perinatal death affecting 8% of all pregnancies. In sheep, IUGR that mimics the human IUGR disease closely can be brought on by environmental hyperthermia. Endothelial nitric oxidase synthase (eNOS) and nitric oxide (NO) are important in the regulation of blood flow in the fetal-placental circulation and are modulated by several factors including hypoxia. eNOS activity is also regulated by the phosphorylation of ERK1/2 and AKT proteins in various tissues. In a hyperthermic (HT) ovine model of IUGR with systemic hypertension and increased blood flow resistance, our objective was to determine the relationship between p-ERK, p-AKT, eNOS, and NO concentrations in the placenta, uterine, and umbilical vessels at mid-gestation and near-term. Eight pregnant ewes were exposed to hyperthermic conditions for either 55 or 80 days to induce IUGR. Sheep necropsies were performed at mid-gestation and near-term for collection of placentomes, umbilical vessels, and the uterine artery. Tissues were assessed for eNOS mRNA and protein, and p-ERK and p-AKT protein. Blood was collected for NO determination at the time of necropsy. Placental insufficiency and IUGR (PI-IUGR) pregnancies demonstrated: 1) reduced placental weight at mid-gestation and reduced placental and fetal weight near-term, 2) no changes in eNOS protein concentration in the uterine artery and umbilical vessels, but an increase in NO in umbilical vein blood at both time points, 3) no significant changes in signal transduction makers (ERK/AKT) in placental tissue at mid-gestation but a significant increase near-term in cotyledon tissues, and 4) an increase in p-AKT in the uterine vessels at term. The near-term findings of increased placental p-ERK and p-AKT proteins and umbilical vein NO concentration suggest one mechanism responsible for the increase in placental eNOS previously described in this PI-IUGR model characterized by fetal systemic hypertension and abnormal umbilical artery Doppler velocimetry.

Transforming growth factor-{beta} (TGF{beta}) receptors I/II differentially regulate TGF{beta}1 and IGF-binding protein-3 mitogenic effects in the human placenta

Maternal IGFs regulate cytotrophoblast proliferation and, thereby, placental growth and function. IGF bioavailability is controlled by IGF-binding proteins (IGFBPs); in placenta, IGFBP-3 is particularly abundant. In other systems, IGFBP-3 can regulate cellular events independently of IGFs; these effects are thought to be mediated by TGFbeta receptors (TbetaR). We have examined IGFBP-3 regulation of IGF-dependent and -independent cytotrophoblast proliferation in first-trimester placental explants and the role of TbetaRII in mediating these effects. In the presence of IGFBP-3 (50 nm), IGF-induced (10 nm) proliferation (monitored by immunohistochemical analysis of Ki67 expression and bromodeoxyuridine incorporation) was significantly reduced (P < 0.05). IGFBP-3 also reduced basal proliferation independently of IGF receptor signaling. Immunohistochemical analysis demonstrated that TGFbeta signaling molecules [TGFbeta receptor I (TbetaRI), TbetaRII, TbetaRV, Smad-2, and ERK] are expressed in syncytium and/or cytotrophoblast. TGFbeta1 (10 ng/ml) enhanced cytotrophoblast proliferation and activated both Smad-2 and ERK-1/2, whereas IGFBP-3 activated only Smad-2. The function of both TGFbeta1 and IGFBP-3 was attenuated by a TbetaRII function-blocking antibody and by small interfering RNA-mediated knockdown of TbetaRII (P < 0.05); this was accompanied by a reduction in Smad-2 activation. This study demonstrates that both TGFbeta1 and IGFBP-3 signal through TbetaRI/II to influence human cytotrophoblast proliferation. However, downstream pathways are distinct, because IGFBP-3 acts only through Smad-2, whereas TGFbeta1 also phosphorylates ERK, resulting in opposite effects on cytotrophoblast proliferation. The effects of maternal growth signals on placental growth and function therefore depend on the balance of ligands, receptors, and signaling molecules at the syncytiotrophoblast surface. Therapeutic manipulation of this balance might offer a strategy to optimize placental development and pregnancy outcome.

Estrogen regulation of placental angiogenesis and fetal ovarian development during primate pregnancy

During human and nonhuman primate pregnancy, an extensive blood vessel network is established within the villous placenta to support fetal growth and follicles develop within the fetal ovary to provide a pool of oocytes for reproductive function in adulthood. These two important developmental events occur in association with a progressive increase in placental estrogen production and levels. This review will describe the developmental processes required for placental vascularization and fetal follicular maturation and recent studies which show that estrogen has an important role in regulating these events.

[Placenta and preeclampsia: relationships between anatomical lesions and clinical symptoms]

The histopathological examination of the placenta is part of the investigational workout since it is a convenient method of examining the central organ involved in the disease process. Characteristic lesions are the vascular placental lesions, and even though their discovery is neither necessary nor specific, they become all the more suggestive of the disease as they are found to be numerous. These vascular lesions are characterized by a microscopic involvement of the basal layer also termed atherosis, associated with uteroplacental artery displasia and its consequences: Infarction, retroplacental haematoma plus all other microscopic injuries of the placenta. These are mainly found in the severe forms of the disease and are usually associated with a placental underdevelopment and IUGR.

Placental growth factor in the first trimester: relationship with maternal factors and placental Doppler studies

OBJECTIVE

Placental growth factor (PlGF) is a potent angiogenic factor that impacts on early placental vascular development. It was our aim to clarify relationships between PlGF and first-trimester maternal/placental factors that are related to placental development.

METHODS

Prospectively enrolled patients at 11-14 weeks' gestation had serum PlGF measurement by enzyme-linked immunosorbent assay. Results were related to maternal age, parity, race, body mass index, mean arterial blood pressure (MAP), smoking/caffeine use and parameters of placental blood flow resistance.

RESULTS

In 110 consecutive patients PlGF levels ranged between 1.0 and 176.1 pg/mL, showing a linear relationship with gestational age (GA) (PlGF = (1.4251 x GA) -74.951, r(2) = 0.0765, F = 8.941, P = 0.03). PlGF did not relate to maternal demographics but negatively correlated with MAP (Spearman rho = -0.191, P < 0.05). Bilateral uterine artery notching was associated with lower PlGF (40.7 (range, 1.01-131.6) vs. 51.1 (range, 6.4-176.1) pg/mL; Mann-Whitney P = 0.034.). A trend to lower levels was also observed when umbilical artery end-diastolic flow was absent (37.1 (range, 6.8-95) vs. 49.3 (range, 1.01-176.1) pg/mL; P = 0.05).

CONCLUSION

PlGF in the first trimester is related to maternal cardiovascular factors and placental Doppler findings that are associated with subsequent placental dysfunction. The utility of this parameter as a first-trimester screening tool on a population basis requires further investigation.

Differential expression of VE-cadherin and VEGFR2 in placental syncytiotrophoblast during preeclampsia - New perspectives to explain the pathophysiology

The pathophysiology of preeclampsia includes an unbalanced syncytiotrophoblast renewal from the underlying cytotrophoblast and increased necrotic/aponecrotic shedding of syncytiotrophoblast particles into the maternal circulation. These non-apoptotic syncytiotrophoblast fragments cause the maternal endothelial dysfunction underlying the syndrome of preeclampsia. In order to understand the pathophysiological changes at the fetomaternal interface in preeclampsia we studied the expression of VE-cadherin and vascular endothelial growth factor receptor-2 (VEGFR2) in preeclampsia. We show that VE-cadherin is expressed in the syncytiotrophoblast and is upregulated in fusing BeWo cells, while inhibition of VE-cadherin expression by siRNA does not block BeWo cell fusion. Our immunohistochemistry data show lower VE-cadherin expression in early onset preeclampsia compared to early controls. In late onset preeclampsia VE-cadherin was significantly more expressed compared to late controls. Concurrently VE-cadherin expression decreased significantly in control pregnancies towards term, but not in pregnancies complicated by preeclampsia. VEGFR2 expression was significantly reduced in all cases of preeclampsia compared to control placentas. Because of their close interaction in barrier function regulation we speculate that sustained expression of VE-cadherin in late onset preeclampsia could counteract VEGFR2 deficiency by enhancing survival pathway stimulation in the syncytiotrophoblast, thus preventing further decompensation of unbalanced villous trophoblast turnover.

Gene expression in the placenta: maternal stress and epigenetic responses

Successful placental development is crucial for optimal growth, development, maturation and survival of the embryo/fetus into adulthood. Numerous epidemiologic and experimental studies have demonstrated the profound influence of intrauterine environment on life, and the diseases to which one is subject as an adult. For the most part, these invidious influences, whether maternal hypoxia, protein or caloric deficiency or excess, and others, represent types of maternal stress. In the present review, we examine certain aspects of gene expression in the placenta as a consequence of maternal stressors. To examine these issues in a controlled manner, and in a species in which the genome has been sequenced, most of these reported studies have been performed in the mouse. Although each individual maternal stress is characterized by up- or down-regulation of specific genes in the placenta, functional analysis reveals some patterns of gene expression common to the several forms of stress. Of critical importance, these genes include those involved in DNA methylation and histone modification, cell cycle regulation, and related global pathways of great relevance to epigenesis and the developmental origins of adult health and disease.

Vascularization in first-trimester chorionic villi in complicated and uncomplicated pregnancies

OBJECTIVE

The purpose of this study was to investigate possible altered chorionic vascularization patterns that are seen already in the first trimester of pregnancies that are complicated by hypertensive disorders or intrauterine growth restriction (IUGR) in the third trimester of pregnancy.

STUDY DESIGN

After chorionic villous sampling, surplus of villi were stored, and a selection was made of pregnancies that were complicated further by hypertensive disorders (n = 26), normotensive IUGR (n = 13), and matched control subjects (n = 60). Vascular parameters of these villi were analyzed with a video-image-analysis system.

RESULTS

In pregnancies that are complicated by early-onset hypertensive disorders and IUGR, the mean distance of the peripheral vessels to the intervillous space and the total of the distances (central and peripheral) are significantly smaller, compared with control subjects (9.3% and 13.8% for hypertensive disorders and 12.2% and 16.1% for IUGR, respectively).

CONCLUSION

Differences in vascularization patterns in the placenta already in the first trimester of pregnancies that are complicated later by hypertensive disorders or IUGR confirm the hypothesis of early changes by means of more vessels and more peripheral vessels that are located in chorionic villi.

Downstream targets of homeobox gene HLX show altered expression in human idiopathic fetal growth restriction

Fetal growth restriction (FGR), a clinically significant pregnancy disorder, is poorly understood at the molecular level. This study investigates idiopathic FGR associated with placental insufficiency. Previously, we showed that the homeobox gene HLX is expressed in placental trophoblast cells and that HLX expression is significantly decreased in human idiopathic FGR. Here, we used the novel approach of identifying downstream targets of HLX in cell culture to detect potentially important genes involved in idiopathic FGR. Downstream targets were revealed by decreasing HLX expression in cultured trophoblast cells with HLX-specific small interfering RNAs to model human idiopathic FGR and comparing these levels with controls using a real-time PCR-based gene profiling system. Changes in candidate HLX target mRNA levels were verified in an independent trophoblast cell line, and candidate target gene expression was assessed in human idiopathic FGR-affected placentae (n = 25) compared with gestation-matched controls (n = 25). The downstream targets RB1 and MYC, cell cycle regulatory genes, showed significantly increased mRNA levels in FGR-affected tissues compared with gestation-matched controls, whereas CCNB1, ELK1, JUN, and CDKN1 showed significantly decreased mRNA levels (n = 25, P < 0.001, t-test). The changes for RB1 and CDKN1C were verified by Western blot analysis in FGR-affected placentae compared with gestation-matched controls (n = 6). We conclude that cell cycle regulatory genes RB1, MYC, CCNB1, ELK1, JUN, and CDKN1C, which control important trophoblast cell functions, are targets of HLX.

Placental mammalian target of rapamycin and related signaling pathways in an ovine model of intrauterine growth restriction

OBJECTIVE

Both phosphorylated (p) mammalian target of rapamycin (mTOR) and protein S6 kinase 1 (p70S6K) are known to regulate protein synthesis and are affected during intrauterine growth restriction (IUGR). We studied the mTOR pathway during hyperthermia (HT)-induced IUGR in sheep.

STUDY DESIGN

Beginning at 40 days gestational age, 4 ewes were exposed to HT for 55 days and 4 were exposed for 80 days to induce IUGR. Western blot analyses were performed for mTOR, p70S6K, 4E-binding protein 1, extracellularly regulated kinase (ERK), and AKT.

RESULTS

HT animals showed: smaller fetuses and placentas near term; reduced placental weight at midgestation; increased p-mTOR, p-ERK, and p-AKT; decreased p70S6K in the near-term cotyledons; decreased p- p70S6K; and increased p-ERK in the caruncles (maternal) near term.

CONCLUSION

Near-term IUGR ovine cotyledons showed up-regulation of p-mTOR, whereas p70S6K was decreased. This suggests that the changes in placental mTOR signaling proteins could be driven by the fetal stress observed near term in this model of IUGR.

Enhanced circulating retinol and non-esterified fatty acids in pregnancies complicated with intrauterine growth restriction

IUGR (intrauterine growth restriction) increases the incidence of perinatal complications and, although several placental transport functions have been shown to be altered in pregnancies complicated by IUGR, the mechanism behind it is not well understood. The aim of the present study was to investigate factors in maternal and cord blood plasma from normal and IUGR-complicated pregnancies associated with the body weight of newborns. At the time of Caesarean section, 24 women with IUGR pregnancies were compared with a group of 30 normal controls with AGA (appropriate gestational age) fetuses who were studied at Caesarean section, which took place 5 weeks later than IUGR pregnancies, and also to a group of 25 non-delivered gestational age-matched control pregnant women (AGA-35wk). Maternal plasma retinol, gamma- and alpha-tocopherol, NEFAs (non-esterified fatty acids), and palmitic, palmitoleic, gamma-linolenic and arachidonic acids were higher in women with IUGR pregnancies than in AGA-35wk controls, whereas stearic and alpha-linolenic acids were lower. Smaller differences were found when comparing these variables for IUGR and AGA women. However, umbilical vein plasma gamma-tocopherol, cholesterol, triacylglycerols and NEFAs were higher in the IUGR group than in the AGA group, whereas arachidonic acid was lower. Maternal plasma retinol and NEFAs were the only variables negatively correlated with birthweight when multiple linear regressions were analysed. In conclusion, the increased levels of circulating retinol and NEFAs in maternal plasma are negatively associated with birth and placental weights, which may reflect an impaired placental transfer in IUGR pregnancies. As retinoids are involved in the control of gene transcription, it is proposed that a decrease in placental transfer of retinol could underlie the metabolic dysfunction of IUGR pregnancies.

Effects of exposure to pesticides during pregnancy on placental maturity and weight of newborns: A cross-sectional pilot study in women from the Chihuahua State, Mexico

It is known that pesticides cross the placental barrier and can cause alterations in the development of placental structures resulting in adverse effects in reproduction. The objectives of this study were to investigate the effects of pesticide exposure during pregnancy on placental maturity and to evaluate the relationship between placental maturity, gestational age and birth weight. We collected the placentas from singleton pregnancies from women exposed (n = 9) and non-exposed (n = 45 full-term and n = 31 preterm) to pesticides as evaluated geographically, by questionnaire and by acetylcholinesterase levels. Placental morphometry from the central and peripheral regions was examined by microscopy and staining with hematoxylin and eosin. The placental maturity index (PMI) was estimated by dividing the number of epithelial plates in terminal villi to their thickness in 1 mm2 of the placental parenchyma. Gestational age, birth weight and the following characteristics of the mother were also recorded: pre-pregnancy body mass index, weight gain during pregnancy and hemoglobin concentrations. Birth weight and the gestational age were correlated with PMI (r = .54 and r = .44, respectively; p < .01). Pesticide exposure was associated with a higher PMI (beta = 7.38, p = .01) after adjusting by variables related to placental maturity. In conclusion, the results suggest a relationship between prenatal exposure to pesticides and placental maturity and may potentially affect the nutrient transport from the mother to the fetus.

Serum pentraxin-3 levels at 11 to 14 weeks' gestation: association with maternal and placental characteristics

OBJECTIVE

Pentraxin (PTX)-3 is an inflammatory molecule that may be increased in the first trimester in pregnancies with subsequent preeclampsia. We measured first-trimester serum PTX-3 and correlated levels with maternal/placental factors related to placental development.

STUDY DESIGN

Prospectively enrolled women had ultrasound, physical examination, and blood draw at 11-14 weeks. PTX-3 determined by enzyme-linked immunosorbent assay was related to maternal age, parity, race, body mass index (BMI), mean arterial blood pressure (MAP), smoking/caffeine, and uterine/umbilical artery Doppler pulsatility index (PI).

RESULTS

In 111 patients PTX-3 levels ranged from 0.2-13.8 ng/mL. Spearman correlation between PTX-3 and gestational age (rho = 0.096), maternal age (rho = -0.049), BMI (rho = -0.07), MAP (rho = -0.085), mean uterine artery PI (rho = 0.150), and umbilical artery PI (rho = -0.021) was nonsignificant (all P > .05). Similarly, PTX-3 distribution was unaffected by smoking/caffeine use, BMI >30, MAP >100 mm Hg, or uterine artery notching (P > .05 for all).

CONCLUSION

First-trimester PTX-3 is unrelated to maternal characteristics and placental Doppler.

Plasma soluble vascular endothelial growth factor receptor-1 concentration is elevated prior to the clinical diagnosis of pre-eclampsia

OBJECTIVE

Accumulating evidence suggests that the balance between vascular endothelial growth factor (VEGF), placental growth factor (PIGF), and their receptors is important for effective vasculogenesis, angiogenesis, and placental development. Recently, the soluble form of VEGFR-1 (sVEGFR-1), an antagonist to VEGF and PIGF, has been implicated in the pathophysiology of pre-eclampsia. Plasma sVEGFR-1 concentration is elevated in pre-eclampsia at the time of clinical diagnosis and correlates with the severity of the disease. The purpose of this study was to determine whether the concentrations of sVEGFR-1 in plasma of pre-eclamptic patients change prior to the clinical manifestations of the disease.

METHODS

A longitudinal case-control study was conducted in normal pregnant women (n = 44) and patients with pre-eclampsia (n = 44). Blood sampling was performed at six intervals: (1) 7-16 weeks; (2) 16-24 weeks; (3) 24-28 weeks; (4)28-32 weeks; (5) 32-36 weeks; and (6) more than 37 weeks of gestation. To examine the relationship between plasmasVEGFR-1 concentration and interval to clinical diagnosis of pre-eclampsia, plasma samples of pre-eclamptic patients at different gestational ages were stratified according to the interval from blood sampling to clinical development of the disease into five groups: (1) at clinical manifestation; (2) 2-5 weeks; (3) 6-10 weeks; (4) 11-16 weeks; and (5) 17-25 weeks before clinical manifestations. Plasma concentrations of sVEGFR-1 were determined by enzyme-linked immunoassay. Parametric statistics and repeated measure procedures were used for the analysis.

RESULTS

The mean plasma sVEGFR-1 concentration in pre-eclamptic patients before the clinical manifestation of the disease was significantly higher than in normal pregnant women at 24-28, 28-32, and 32-37 weeks of gestation (p = 0.02,p < 0.001, and p < 0.001, respectively). In contrast, no significant differences in the mean plasma sVEGFR-1 concentration between patients with pre-eclampsia and normal pregnant women were observed both at 7-16 weeks and 16-24 weeks of gestation (p= 0.1 and p= 0.9). Similarly, the mean plasma sVEGFR-1 concentration was significantly higher in pre-eclamptic patients than in normal pregnant women at clinical manifestation, at 2-5 weeks (mean 3.8 weeks), and at 6-10 weeks (mean 8.2 weeks) prior to the development of clinical pre-eclampsia (p < 0.001, p < 0.001, and p = 0.002,respectively). Among patients with early-onset pre-eclampsia (defined as gestational age of 34 weeks or less), the mean plasma sVEGFR-1 concentration was significantly higher in pre-eclampsia (before clinical diagnosis) than in normal pregnant women at 24-28 (mean 26.4) weeks of gestation (p = 0.008). In contrast, among patients with the late-onset disease(defined as gestational age of more than 34 weeks), plasma sVEGFR-1 concentration in pre-clinical pre-eclampsia was significantly higher than in normal pregnant women at 28-32 (mean 30.2) weeks of gestation (p < 0.001).

CONCLUSIONS

Plasma sVEGFR-1 concentration is elevated in pre-eclampsia prior to the clinical diagnosis of the disease. This elevation began 6-10 weeks prior to the clinical manifestations, and the increase was more pronounced at 2-5 weeks before the diagnosis, as well as at clinical presentation. Furthermore, in early-onset pre-eclampsia, plasma concentration ofsVEGFR-1 is elevated earlier than the late-onset disease.

Doppler ultrasonography in obstetrics: from the diagnosis of fetal anemia to the treatment of intrauterine growth-restricted fetuses

After the adoption of the use of umbilical artery and middle cerebral artery peak systolic velocity in high-risk pregnancies and in pregnancies that are at risk of having an anemic fetus, the main focus of Doppler ultrasonography in obstetrics today is intrauterine growth-restricted fetuses. What is most needed at this time are (1) training of sonographers and sonologists on how to perform a Doppler study, (2) an international classification of intrauterine growth-restricted fetuses, and (3) a study of the natural history of intrauterine growth-restricted fetuses that might contribute to a better understanding of the intrauterine growth-restriction process and to standard treatment of intrauterine growth-restricted fetuses. Future investigations, which would include randomized studies, could be designed from the results of such studies.

In vitro spheroid model of placental vasculogenesis: does it work?

Placental vascular development begins very early in pregnancy and is characterized by construction of a primitive vascular network in a low-oxygen environment. In vitro three-component assays of this process are scarce. In this study, a complex three-dimensional spheroid model for in vitro studies of placental vasculogenesis with regard to cell-cell interactions between cytotrophoblasts (CTs), villous stromal cells and endothelial precursor cells was established. Microscopic and immunohistochemical analyses of the spheroids showed structural and differentiation patterns resembling the structure and differentiation of early placental chorionic villous tissue (in regard to the expression of multiple markers cytokeratin-7, vimentin, CD34, CD31). The authenticity of this model to in vivo events allowed investigation of placental vascular development and trophoblast invasion under physiological and pathological conditions. Particularly enhanced spheroidal expression of SDF-1alpha and its receptor CXCR4, the major chemokine system in embryonic vasculogenesis, in a low-oxygen environment was detected. In addition, our model confirmed previously described invasive phenotype of trophoblasts through collagen under low- (physiologic), but not high- (pathologic) oxygen concentrations. Therefore, the three-dimensional spheroid model consisting of major placental cell types proved to be an appropriate system to investigate early placental vessel development under both physiological and pathological conditions.

Etoposide induces TRP53-dependent apoptosis and TRP53-independent cell cycle arrest in trophoblasts of the developing mouse placenta

Abnormal regulation of placental apoptosis and proliferation has been implicated in placental disorders. Recently, several DNA-damaging agents were reported to induce excessive apoptosis and reduce cell proliferation in the placenta; however, the molecular pathways of these toxic effects on the placenta are unclear. The aim of the present study was to determine the involvement of TRP53, a tumor suppressor that mediates cellular responses to DNA damage, in the induction of apoptosis and cell cycle arrest in the developing placenta. For this purpose, we treated pregnant mice on Day 12 of gestation with 10 mg/kg of etoposide and 5-Gy gamma irradiation, potent inducers of DNA damage. We found an increase in the number of trophoblastic apoptoses 8 and 24 h after etoposide injection and 6 and 24 h after irradiation in the placental labyrinth zone. The number of mitoses and DNA syntheses in trophoblasts decreased after treatment. The accumulation and phosphorylation of TRP53 protein were detected 8 and 6 h after etoposide injection and irradiation, respectively. In Trp53-deficient placentas, the induction of etoposide-induced trophoblastic apoptosis is abrogated, while the reduction of proliferation occurred similarly as in wild-type placentas. CDC2A, a regulator of G2/M progression, was inactivated by phosphorylation after etoposide injection and irradiation, suggesting that the cell cycle was arrested at the G2/M border by treatment. Our study demonstrated that etoposide injection induced TRP53-dependent apoptosis and TRP53-independent cell cycle arrest in labyrinthine trophoblasts, providing insights into the molecular pathway of placental disorders.

Effect of impaired glucose tolerance during pregnancy on the expression of VEGF receptors in human placenta

The aim of the present study was to determine the expression of vascular endothelial growth factor (VEGF) receptors VEGFR-1, VEGFR-2 and VEGFR-3 in placentas from pregnancies complicated by altered glycaemia. Placentas from women with physiological pregnancies (Group 1), pregnancies complicated by minor degree of glucose intolerance (MDGI, Group 2) and by gestational diabetes mellitus (GDM) treated with insulin (Group 3) were collected. Immunohistochemistry, RT-PCR and western blot were employed to evaluate receptor expression. In the three study groups, VEGFR-1 immunoreactivity was detected in all the placental components. VEGFR-2 immunoreactivity was observed in the vessels of all the placentas from Groups 1 and 2, but only in some placentas of Group 3. VEGFR-3 reactivity was observed in all the components of Group 1; in Groups 2 and 3 reactivity was observed in some portions of the trophoblast or the whole trophoblast, and in the stroma. VEGFR-1 and VEGFR-2 mRNA levels in Groups 2 and 3 were significantly higher compared with Group 1, whereas those of VEGFR-3 were significantly lower. Receptor protein levels were significantly lower in Groups 2 and 3 compared with Group 1. These findings demonstrated dysregulation of expression of the three placental receptors, both in GDM and in MDGI.

What is spared by fetal brain-sparing? Fetal circulatory redistribution and behavioral problems in the general population

Intrauterine growth restriction has been linked to infant behavioral problems. While typically only birth weight is examined, here the authors assessed fetal circulatory redistribution, also called the "brain-sparing effect," which is a fetal adaptive reaction to placental insufficiency. They aimed to investigate whether fetal circulatory redistribution protects against behavioral problems. Within the Generation R Study (Rotterdam, the Netherlands, 2003-2007), fetal circulation variables for the umbilical artery and the middle and anterior cerebral arteries were assessed with Doppler ultrasound in late pregnancy. Ratios between placental resistance and cerebral resistance were related to behavioral problems, as measured by the Child Behavior Checklist, in 935 toddlers aged 18 months. The umbilical/anterior cerebral ratio was associated with the Total Problems summary score from the Child Behavior Checklist (per standard-deviation increase, odds ratio = 1.2, 95% confidence interval: 1.0, 1.5). Children with higher umbilical/anterior cerebral ratios had higher risks of internalizing problems, emotional reactivity, somatic complaints, and attention problems. A high umbilical/middle cerebral ratio was related to higher scores on the Internalizing and Somatic Complaints scales. The authors conclude that infants with circulatory redistribution in gestation are more likely to have behavioral problems. This suggests that "brain-sparing" does not completely spare the brain and indicates underlying pathology with consequences for later behavior.

Maternal risk factors for abnormal placental growth: the national collaborative perinatal project

Background

Previous studies of maternal risk factors for abnormal placental growth have focused on placental weight and placental ratio as measures of placental growth. We sought to identify maternal risk factors for placental weight and two neglected dimensions of placental growth: placental thickness and chorionic plate area.

Methods

We conducted an analysis of 24,135 mother-placenta pairs enrolled in the National Collaborative Perinatal Project, a prospective cohort study of pregnancy and child health. We defined growth restriction as < 10^th percentile and hypertrophy as > 90^th percentile for three placental growth dimensions: placental weight, placental thickness and chorionic plate area. We constructed parallel multinomial logistic regression analyses to identify (a) predictors of restricted growth (vs. normal) and (b) predictors of hypertrophic growth (vs. normal).

Results

Black race was associated with an increased likelihood of growth restriction for placental weight, thickness and chorionic plate area, but was associated with a reduced likelihood of hypertrophy for these three placental growth dimensions. We observed an increased likelihood of growth restriction for placental weight and chorionic plate area among mothers with hypertensive disease at 24 weeks or beyond. Anemia was associated with a reduced likelihood of growth restriction for placental weight and chorionic plate area. Pre-pregnancy BMI and pregnancy weight gain were associated with a reduced likelihood of growth restriction and an increased likelihood of hypertrophy for all three dimensions of placental growth.

Conclusion

Maternal risk factors are either associated with placental growth restriction or placental hypertrophy not both. Our findings suggest that the placenta may have compensatory responses to certain maternal risk factors suggesting different underlying biological mechanisms.

PPAR-gamma signaling pathway in placental development and function: a potential therapeutic target in the treatment of gestational diseases

BACKGROUND

PPAR-gamma is a target for the treatment of metabolic disorders, as Pioglitazone and Rosiglitazone are already used against type 2 diabetes. Pleiotropic functions, such as antiproliferative and anti-inflammatory effects against several pathological states, including cardiovascular disease and cancer, are currently being explored in clinical studies.

OBJECTIVE

Evidence indicates that PPAR-gamma is expressed in the placenta, playing a crucial role in placental development and function, while PPAR-gamma ligands appear to modulate fetal membrane signals. Thus, in the last few years, the pivotal role of PPAR-gamma in placental biology has been the focus of extensive research, as diabetes appears to be the most common metabolic dysfunction in pregnancy.

METHODS

We aim to present data concerning the expression of PPAR-gamma in animal and human placenta, underlining its significance in normal placental development and several gestational diseases. The effects of PPAR-gamma ligands as modulators of placental biology in normal and certain pathological conditions are also discussed.

RESULTS/CONCLUSION

Current research provides substantial evidence that PPAR-gamma plays a pivotal role in placental biology and may reveal new perspectives in the treatment of gestational diseases.

Modeling the variability of shapes of a human placenta

BACKGROUND

Placentas are generally round/oval in shape, but "irregular" shapes are common. In the Collaborative Perinatal Project data, irregular shapes were associated with lower birth weight for placental weight, suggesting variably shaped placentas have altered function.

METHODS

(I) Using a 3D one-parameter model of placental vascular growth based on Diffusion Limited Aggregation (an accepted model for generating highly branched fractals), models were run with a branching density growth parameter either fixed or perturbed at either 5-7% or 50% of model growth. (II) In a data set with detailed measures of 1207 placental perimeters, radial standard deviations of placental shapes were calculated from the umbilical cord insertion, and from the centroid of the shape (a biologically arbitrary point). These two were compared to the difference between the observed scaling exponent and the Kleiber scaling exponent (0.75), considered optimal for vascular fractal transport systems. Spearman's rank correlation considered p<0.05 significant.

RESULTS

(I) Unperturbed, random values of the growth parameter created round/oval fractal shapes. Perturbation at 5-7% of model growth created multilobate shapes, while perturbation at 50% of model growth created "star-shaped" fractals. (II) The radial standard deviation of the perimeter from the umbilical cord (but not from the centroid) was associated with differences from the Kleiber exponent (p=0.006).

CONCLUSIONS

A dynamical DLA model recapitulates multilobate and "star" placental shapes via changing fractal branching density. We suggest that (1) irregular placental outlines reflect deformation of the underlying placental fractal vascular network, (2) such irregularities in placental outline indicate sub-optimal branching structure of the vascular tree, and (3) this accounts for the lower birth weight observed in non-round/oval placentas in the Collaborative Perinatal Project.

Placental expression of insulin-like growth factor-I, fibroblast growth factor-basic and neural cell adhesion molecule in pregnancies with small for gestational age fetuses

OBJECTIVE

To investigate placental expression of insulin-like growth factor-I (IGF-I), fibroblast growth factor-basic (FGF-b) and neural cell adhesion molecule (N-CAM) regarding the pathogenesis of pregnancies with small for gestational age (SGA) fetuses.

STUDY DESIGN

An immunohistochemical analysis using anti-IGF-I, anti-FGF-b and anti-N-CAM antibodies was carried out on 4% paraformaldehyde-fixed placental tissues of third trimester pregnancies complicated with SGA fetuses (n=12) and subjects exhibiting appropriately grown fetuses (n=10). Immunostaining patterns of chorionic villi and amniochorionic membranes were assessed.

RESULT

IGF-I, FGF-b and N-CAM immunostainings in chorionic villi demonstrated significantly increased immunoreactivities in cytotrophoblasts of SGA cases, whereas increased IGF-I immunostaining in syncitiotrophoblasts and increased N-CAM immunostaining in capillary endothelium were noted in the same group. IGF-I, FGF-b and N-CAM immunostainings in amniochorionic membranes revealed significantly decreased IGF-I immunoreactivities in extravillous trophoblasts and increased IGF-I immunoreactivities in decidual cells of SGA cases, while significantly decreased N-CAM immunoreactivities in both decidual cells and extravillous trophoblasts were noted. FGF-b immunostaining revealed no significant differences in both extravillous trophoblasts and decidual cells of SGA cases.

CONCLUSION

Increased placental expression of IGF-I, FGF-b and N-CAM may act in an autocrine and/or paracrine manner to restore the impaired trophoblastic proliferation, migration and metabolism at all gestational stages by means of a positive feedback mechanism.

An animal model of placental insufficiency-induced intrauterine growth restriction

Intrauterine growth restriction (IUGR), often associated with functional placental insufficiency, results in increased perinatal mortality and morbidity. For obvious reasons, many questions regarding the progression of IUGR pregnancies cannot be addressed experimentally in humans, predicating the use of animal models. Although no animal model fully recapitulates human pregnancy, the pregnant sheep has been used extensively to investigate maternal-fetal interactions. In sheep, surgical placement of catheters in both the maternal and fetal vasculature allows repeated sampling from nonanesthetized pregnancies. Considerable insight has been gained on placental oxygen and nutrient transfer and utilization from use of pregnant sheep, often confirmed in the human once appropriate technologies became available. This review will focus on one sheep model, used to examine the impact of placental insufficiency-induced IUGR on oxygen and nutrient transport and utilization.

Maternal Tgif is required for vascularization of the embryonic placenta

The mammalian placenta is the site of exchange of nutrients and waste between mother and embryo. In humans, placental insufficiency can result in intrauterine growth retardation, perinatal death and spontaneous abortion. We show that in C57BL/6J mice a null mutation in the gene encoding the transcriptional corepressor, Tgif, causes placental defects. The major defects are decreased vascularization of the placenta, due to a decrease in the fetal blood vessels, and decreased expression of the gap junction protein Gjb2 (Cx26). These defects result in severe growth retardation in a proportion of Tgif null embryos in Tgif heterozygous mothers, and an overall growth delay in Tgif null animals. Placental defects are much more severe if the mother also completely lacks Tgif function, and placentas from heterozygous Tgif embryos are defective in a Tgif null mother. Embryo transfer experiments show that even the placenta from a wild type embryo is compromised in the absence of maternal Tgif. These results demonstrate that Tgif functions in the normal development of the placenta, and suggest a role for maternal factors in regulating the morphogenesis of embryonically-derived placental tissues.

The maternal plasma soluble vascular endothelial growth factor receptor-1 concentration is elevated in SGA and the magnitude of the increase relates to Doppler abnormalities in the maternal and fetal circulation

OBJECTIVES

The soluble form of vascular endothelial growth factor receptor-1 (sVEGFR-1), an antagonist to vascular endothelial growth factor and placental growth factor, has been implicated in the pathophysiology of preeclampsia. Preeclampsia and pregnancy complicated with small for gestational age (SGA) fetuses share some pathophysiologic derangements, such as failure of physiologic transformation of the spiral arteries, endothelial cell dysfunction, and leukocyte activation. The objectives of this study were to: (1) determine whether plasma concentrations of sVEGFR-1 in mothers with SGA fetuses without preeclampsia at the time of diagnosis are different from those in patients with preeclampsia or normal pregnant women, and (2) examine the relationship between plasma concentrations of sVEGFR-1 and Doppler velocimetry in uterine and umbilical arteries in patients with preeclampsia and those with SGA.

STUDY DESIGN

A cross-sectional study was conducted to determine the concentrations of the soluble form of VEGFR-1 in plasma obtained from normal pregnant women (n = 135), women with SGA fetuses (n = 53), and patients with preeclampsia (n = 112). Patients with SGA fetuses and those with preeclampsia were sub-classified according to the results of uterine and umbilical artery Doppler velocimetry examinations. Plasma concentrations of sVEGFR-1 were determined by an ELISA. Since these concentrations change with gestational age, differences among various subgroups were statistically estimated with the delta value, defined as the difference between the observed and expected plasma sVEGFR-1 concentration. The expected values were derived from regression analysis of plasma sVEGFR-1 concentrations in normal pregnancy. Regression analysis and univariate and multivariate analysis were employed.

RESULTS

(1) Mothers with SGA fetuses had a mean plasma concentration of sVEGFR-1 higher than normal pregnant women (p < 0.001), but lower than patients with preeclampsia (p < 0.001). (2) Among patients with SGA fetuses, only those with abnormal uterine artery Doppler velocimetry had a mean plasma sVEGFR-1 concentration significantly higher than normal pregnant women (p < 0.001). (3) Among mothers with SGA fetuses in whom Doppler velocimetry was performed (n = 41), those with abnormalities in both the uterine and umbilical artery velocimetry had the highest mean delta of sVEGFR-1 plasma concentration (mean +/- standard deviation (SD): 0.69 +/- 0.29). Conversely, patients who had normal Doppler velocimetry in both uterine and umbilical arteries had the lowest mean delta (mean +/- SD: 0.09 +/- 0.29) of sVEGFR-1 plasma concentrations (ANOVA; p < 0.001). (4) Among patients with preeclampsia in whom Doppler velocimetry was performed (n = 69), those with abnormalities in both the uterine and umbilical artery velocimetry had the highest mean delta sVEGFR-1 plasma concentration (mean +/- SD: 1.01 +/- 0.22) among all groups classified (ANOVA; p < 0.001). (5) Among patients with SGA and those with preeclampsia, there was a relationship (Chi-square for trend p < 0.001 for both) between the severity of Doppler velocimetry abnormalities and the proportion of patients who had high delta sVEGFR-1 plasma concentrations (defined as a concentration two standard deviations (2SD) above the mean delta of normal pregnant women). (6) Multiple regression analysis suggested that the diagnostic category (e.g., SGA or preeclampsia), Doppler abnormalities, and gestational age at blood sampling were associated with an increase in plasma sVEGFR-1 concentrations (p < 0.001).

CONCLUSIONS

These observations provide support for the participation of the soluble receptor of vascular endothelial growth factor in the pathophysiology of SGA with abnormal uterine artery Doppler velocimetry and preeclampsia. An excess of sVEGFR-1 is released into the maternal circulation of patients with preeclampsia and those with SGA fetuses, as abnormalities of impedance to blood flow involve uterine and umbilical circulation.

Angiogenic, hyperpermeability and vasodilator network in utero-placental units along pregnancy in the guinea-pig (Cavia porcellus)

BACKGROUND

The angiogenic and invasive properties of the cytotrophoblast are crucial to provide an adequate area for feto-maternal exchange. The present study aimed at identifying the localization of interrelated angiogenic, hyperpermeability and vasodilator factors in the feto-maternal interface in pregnant guinea-pigs.

METHODS

Utero-placental units were collected from early to term pregnancy. VEGF, Flt-1, KDR, B2R and eNOS were analyzed by immunohistochemistry, and the intensity of the signals in placenta and syncytial streamers was digitally analysed. Flt1 and eNOS content of placental homogenates was determined by western blotting. Statistical analysis used one-way analysis of variance and Tukey's Multiple Comparison post-hoc test.

RESULTS

In the subplacenta, placental interlobium and labyrinth VEGF, Flt-1, KDR, B2R and eNOS were expressed in all stages of pregnancy. Syncytial streamers in all stages of gestation, and cytotrophoblasts surrounding myometrial arteries in early and mid pregnancy - and replacing the smooth muscle at term - displayed immunoreactivity for VEGF, Flt-1, KDR, eNOS and B2R. In partly disrupted mesometrial arteries in late pregnancy cytotrophoblasts and endothelial cells expressed VEGF, Flt-1, KDR, B2R and eNOS. Sections incubated in absence of the first antibody, or in presence of rabbit IgG fraction and mouse IgG serum, yielded no staining. According to the digital analysis, Flt-1 increased in the placental interlobium in days 40 and 60 as compared to day 20 (P = 0.016), and in the labyrinth in day 60 as compared to days 20 and 40 (P = 0.026), while the signals for VEGF, KDR, B2R, and eNOS showed no variations along pregnancy. In syncytial streamers the intensity of VEGF immunoreactivity was increased in day 40 in comparison to day 20 (P = 0.027), while that of B2R decreased in days 40 and 60 as compared to day 20 (P = 0.011); VEGF, Flt-1, KDR, B2R and eNOS expression showed no variations. Western blots for eNOS and Flt-1 in placental homogenates showed no significant temporal differences along pregnancy.

CONCLUSION

The demonstration of different angiogenic, hyperpermeability and vasodilator factors in the same cellular protagonists of angiogenesis and invasion in the pregnant guinea-pig, supports the presence of a functional network, and strengthens the argument that this species provides an adequate model to understand human pregnancy.

The IGF axis and placental function. a mini review

It is well known that the insulin-like growth factor (IGF) axis is an important regulator of foetal growth and in recent years, it has been suggested that the ligands IGF-I and IGF-II may, in part, mediate this effect by promoting proper placental development and function. In other tissues, IGF effects on metabolism, proliferation and differentiation are primarily mediated via IGF binding protein-regulated interaction of IGFs with the type 1 IGF receptor and therefore here, we review the placental expression and postulated role, of each of the IGF axis components and discuss the cellular mechanisms through which these effects are exerted.

Ethnic heterogeneity in the longitudinal effects of placental vascular blood flow on birthweight

OBJECTIVE

Our goals were: (1) to estimate the longitudinal trends in uterine artery (UtArt) and umbilical artery (UmArt) resistance indices (RIs) in different ethnic strata; (2) to estimate time-dependent changes across gestation in the influence of variation in UtArt and UmArt RI on variation in birthweight in different ethnic strata; and (3) to determine the optimum set of UtArt and UmArt RIs for predicting birthweight in different ethnic strata.

STUDY DESIGN

Analyses were carried out on data collected in a prospective study of 535 multiethnic gravidas recruited from the Cedars-Sinai Medical Center (Los Angeles, CA). Baseline maternal characteristics were recorded at time of entry into the study. UtArt and UmArt RIs were measured on 3 occasions during pregnancy (visit 1, 16-20 weeks' gestation; visit 2, 21-29 weeks' gestation; and visit 3, 30-36 weeks' gestation). The outcome for this study was gestational age-adjusted birthweight (aBW).

RESULTS

The average UtArt and UmArt RI decreased steadily across gestation for all ethnicities. The average UtArt RI at each visit and the average rate of change between visits were not significantly different among the ethnicities. However, the UmArt RI measured at visit 3 and its rate of change in the last trimester were significantly different among the ethnic groups (P < .02). After adjustment for traditional risk factors for fetal growth restriction, the magnitude and rate of change of UtArt RI significantly predicted aBW only in Hispanic women, whereas the magnitude and rate of change of UmArt RI predicted aBW only in African American women. The most parsimonious combination of UtArt and UmArt RI measurements at visits 1, 2, and 3 that predicted statistically significant variation in aBW differed by ethnicity.

CONCLUSION

The relationships between aBW and longitudinally collected measures of UtArt and UmArt RI depend on the context defined by ethnicity and time of measurement after adjusting for a parsimoniously selected subset of traditional risk factors.

Severe intrauterine growth restriction pregnancies have increased placental endoglin levels: hypoxic regulation via transforming growth factor-beta 3

Endoglin, a co-receptor for transforming growth factor (TGF)-beta 1 and -beta 3 is expressed in the human placenta and plays an important role in the pathogenesis of preeclampsia. Because preeclampsia is associated with hypoxia, and because TGF-beta 3 is overexpressed in preeclamptic pregnancies, we examined the effect of oxygen and TGF-beta 3 on placental endoglin expression and investigated its expression in pathological models of placental hypoxia such as intrauterine growth restriction (IUGR) pregnancies. Endoglin expression was high at 4 to 9 weeks of gestation, when oxygen tension is low, and decreased after 10 weeks, when oxygen tension increases. Exposure of villous explants to low oxygen (3% O2) resulted in elevated expression of both membrane and soluble endoglin compared to standard conditions (20% O2). Moreover, addition of TGF-beta 3 to villous explants under low oxygen conditions increased the expression of endoglin compared to nontreated explants whereas addition of TGF-beta 3-neutralizing antibodies inhibited the low oxygen stimulatory effect on endoglin expression. Endoglin and soluble endoglin expression were significantly increased in placentas of IUGR singletons compared to controls and in the IUGR twin placentas relative to both the control co-twin and the normal twins. These data demonstrate that oxygen regulates the placental expression of endoglin via TGF-beta 3. Reduced placental perfusion leading to placental hypoxia might contribute to the increased expression of endoglin in IUGR pregnancies.

Differential gene expression of somatotrophic and growth factors in response to in vivo hypoxia in human placenta

OBJECTIVE

Hypoxia-inducible transcription factors (HIFs) have been characterized as the most important regulators of O(2)-dependent gene transcription. We investigated expression of HIF-dependent growth factors and HIF-independent somatotrophic factors in term placenta in response to hypoxic ischemia.

STUDY DESIGN

Our cross-sectional in vivo analysis included term placentas of gestations complicated by the following: (1) birth asphyxia (n = 22); (2) chronic hypoxic ischemia (n = 22); and (3) controls (n = 28). Gene expression of leptin, insulin-like growth factor (IGF)-1, IGF-2, ghrelin, and human placental growth hormone (hPGH) were measured by TaqMan reverse transcriptase-polymerase chain reaction.

RESULTS

Acute and chronic hypoxia significantly increased leptin messenger ribonucleic acid (mRNA) levels, compared with controls (P < .001). Augmented IGF-2 mRNA levels were present in chronic hypoxia (P < .001) but not in birth asphyxia. IGF-1, ghrelin, and hPGH mRNA levels did not change in relation to hypoxia.

CONCLUSION

IGF-2 and leptin are suggested to be involved in adaptive response to hypoxic ischemia in term placenta with differential transcriptional regulation related to the duration of hypoxia.

Hypoxia enhances the expression of follistatin-like 3 in term human trophoblasts

Hypoxic injury hinders placental differentiation and alters trophoblast gene expression. We tested the hypothesis that the expression of follistatin-like 3 (FSTL3), a member of the follistatin family of proteins, is modulated by hypoxia in primary human trophoblast (PHT). Using immunofluorescence of human term placental villi we detected the expression of FSTL3 protein in placental villi, primarily in trophoblasts. We verified this finding in cultured term PHT cells. Basal expression of FSTL3 transcript in cultured PHT cells, determined using quantitative PCR, was stable over the culture period. Importantly, when compared to culture in FiO(2)=20% or FiO(2)=8%, PHT cells cultured in FiO(2) <1% exhibited a 4-6 fold increase in FSTL3 mRNA expression as early as 4h in hypoxia. Whereas cellular FSTL3 protein was unchanged in hypoxia, we found that hypoxia increased the level of FSTL3 in the medium. Lastly, the exposure of PHT cells to either the hypoxia-mimetic cobalt chloride or the proline hydroxylase inhibitor dimethyloxaloylglycine upregulated the expression of FSTL3 transcript. Our data indicate that hypoxia enhances the expression of FSTL3 and its release from PHT cells. Our finding that hypoxia-mimetic agents enhance FSTL3 expression implicates HIF1alpha in this process.

Gene expression patterns in the hypoxic murine placenta: a role in epigenesis?

Hypoxia has been identified as a major stress or in placental and fetal development. To test the hypothesis that hypoxic stress responses are associated with gene expression changes, the authors measured gene expression in the mouse placenta in response to 48 hours of hypoxia. Embryonic day 15.5 pregnant mice were exposed to 48 hours of hypoxia (10.5% O(2)), after which the Affymetrix Mouse 430A_2.0 array was used to measure gene expression changes in the placenta. The authors observed 171 probe sets, corresponding to 163 genes, that were regulated by hypoxia (P < .01). Ninety genes were upregulated, and 73 were downregulated. The authors functionally annotated the regulated genes and examined overrepresented functional categories. Among the upregulated and downregulated genes, several overrepresented functional categories were observed. Upregulated genes included those involved in metabolism, oxygen transport, proteolysis, cell death, metabolism of reactive oxygen species, and DNA methylation. Genes involved in transcription, cell cycle regulation, and cell structure were downregulated. Microarray analysis has allowed the description of the genetic responses to hypoxia in the mouse placenta. The observation that hypoxia upregulates reactive oxygen species metabolism, in conjunction with DNA methylation enzymes, suggests that hypoxia may contribute to long-term epigenetic changes in stressed fetal tissues and organs.

Ontogeny of endothelial nitric oxide synthase mRNA in an ovine model of fetal and placental growth restriction

OBJECTIVE

To determine: 1) placental eNOS mRNA concentration across gestation in normal ovine pregnancy and in an ovine model of intrauterine growth restriction (IUGR), and 2) placental eNOS protein concentration in early ovine pregnancy.

STUDY DESIGN

A total of 24 sheep were studied with 12 ewes placed in hyperthermic (HT) conditions to induce IUGR and 12 were kept in control conditions. HT and control animals underwent euthanasia at 3 developmental time points (55, 95, & 130 days gestational age; dGA) in ovine placental & fetal development.

RESULTS

Compared to controls, HT pregnancies showed 1) no differences in fetal weights at 55 dGA and 95dGA with significant reductions at 130 dGA, 2) significantly smaller placentae at 95 and 130 dGA with a trend for a reduction at 55 dGA, 3) significant decreases in cotyledon eNOS mRNA at 95 and 130 dGA, 4) a significant increase in caruncle eNOS mRNA expression at 130 dGA, 5) significant increase in eNOS protein in the caruncle, but not in the cotyledon at 55 dGA.

CONCLUSION

Placental eNOS concentration is transcriptionally regulated at mid-gestation, while additional post-transcriptional regulation is also involved during early and late gestation in this model of placental and fetal growth restriction.

Placenta: angiogenesis and vascular assessment through three-dimensional power Doppler ultrasonography

The placenta is fundamental for fetal development. It combines the functions of an endocrine organ, kidneys, lungs and intestines, purifying catabolites, oxygenating and nourishing the conceptus. Its fetal portion is the largest part develops from the chorionic sac. The maternal portion, which is smaller, is originated in the endometrium, more specifically in the decidua basalis. The placenta starts its function closer to the fourth week of gestation, when anatomical arrangements for the physiological exchanges are already established. The circulatory function of the placenta appears at an early stage of embryo-placental development and it is strongly related to fetal growth, to the placental size and to uterine and umbilical blood flows. Therefore, an adequate placental angiogenesis is critical for the establishment of a normal placental vascularization with consequent normal development of the fetus. In this review article, the authors discuss about placental ontogeny, focusing on the main aspects of its normal development, and about the recent advances in ultrasonography for the study of the vascular architecture of the placenta through three-dimensional power Doppler ultrasonography.