Lipid profile of circulating placental extracellular vesicles during pregnancy identifies foetal growth restriction risk

Small-for-gestational age (SGA) neonates exhibit increased perinatal morbidity and mortality, and a greater risk of developing chronic diseases in adulthood. Currently, no effective maternal blood-based screening methods for determining SGA risk are available. We used a high-resolution MS/MSALL shotgun lipidomic approach to explore the lipid profiles of small extracellular vesicles (sEV) released from the placenta into the circulation of pregnant individuals. Samples were acquired from 195 normal and 41 SGA pregnancies. Lipid profiles were determined serially across pregnancy. We identified specific lipid signatures of placental sEVs that define the trajectory of a normal pregnancy and their changes occurring in relation to maternal characteristics (parity and ethnicity) and birthweight centile. We constructed a multivariate model demonstrating that specific lipid features of circulating placental sEVs, particularly during early gestation, are highly predictive of SGA infants. Lipidomic-based biomarker development promises to improve the early detection of pregnancies at risk of developing SGA, an unmet clinical need in obstetrics.

Decreased Vitamin D Levels and Altered Placental Vitamin D Gene Expression at High Altitude: Role of Genetic Ancestry

High-altitude hypoxia challenges reproduction; particularly in non-native populations. Although high-altitude residence is associated with vitamin D deficiency, the homeostasis and metabolism of vitamin D in natives and migrants remain unknown. We report that high altitude (3600 m residence) negatively impacted vitamin D levels, with the high-altitude Andeans having the lowest 25-OH-D levels and the high-altitude Europeans having the lowest 1α,25-(OH)2-D levels. There was a significant interaction of genetic ancestry with altitude in the ratio of 1α,25-(OH)2-D to 25-OH-D; with the ratio being significantly lower in Europeans compared to Andeans living at high altitude. Placental gene expression accounted for as much as 50% of circulating vitamin D levels, with CYP2R1 (25-hydroxylase), CYP27B1 (1α-hydroxylase), CYP24A1 (24-hydroxylase), and LRP2 (megalin) as the major determinants of vitamin D levels. High-altitude residents had a greater correlation between circulating vitamin D levels and placental gene expression than low-altitude residents. Placental 7-dehydrocholesterol reductase and vitamin D receptor were upregulated at high altitude in both genetic-ancestry groups, while megalin and 24-hydroxylase were upregulated only in Europeans. Given that vitamin D deficiency and decreased 1α,25-(OH)2-D to 25-OH-D ratios are associated with pregnancy complications, our data support a role for high-altitude-induced vitamin D dysregulation impacting reproductive outcomes, particularly in migrants.

Ancestry dependent balancing selection of placental dysferlin at high-altitude

Introduction: The placenta mediates fetal growth by regulating gas and nutrient exchange between the mother and the fetus. The cell type in the placenta where this nutrient exchange occurs is called the syncytiotrophoblast, which is the barrier between the fetal and maternal blood. Residence at high-altitude is strongly associated with reduced 3rd trimester fetal growth and increased rates of complications such as preeclampsia. We asked whether altitude and/or ancestry-related placental gene expression contributes to differential fetal growth under high-altitude conditions, as native populations have greater fetal growth than migrants to high-altitude. Methods: We have previously shown that methylation differences largely accounted for altitude-associated differences in placental gene expression that favor improved fetal growth among high-altitude natives. We tested for differences in DNA methylation between Andean and European placental samples from Bolivia [La Paz (∼3,600 m) and Santa Cruz, Bolivia (∼400 m)]. One group of genes showing significant altitude-related differences are those involved in cell fusion and membrane repair in the syncytiotrophoblast. Dysferlin (DYSF) shows greater expression levels in high- vs. low-altitude placentas, regardless of ancestry. DYSF has a single nucleotide variant (rs10166384;G/A) located at a methylation site that can potentially stimulate or repress DYSF expression. Following up with individual DNA genotyping in an expanded sample size, we observed three classes of DNA methylation that corresponded to individual genotypes of rs10166384 (A/A < A/G < G/G). We tested whether these genotypes are under Darwinian selection pressure by sequencing a ∼2.5 kb fragment including the DYSF variants from 96 Bolivian samples and compared them to data from the 1000 genomes project. Results: We found that balancing selection (Tajima's D = 2.37) was acting on this fragment among Andeans regardless of altitude, and in Europeans at high-altitude (Tajima's D = 1.85). Discussion: This supports that balancing selection acting on dysferlin is capable of altering DNA methylation patterns based on environmental exposure to high-altitude hypoxia. This finding is analogous to balancing selection seen frequency-dependent selection, implying both alleles are advantageous in different ways depending on environmental circumstances. Preservation of the adenine (A) and guanine (G) alleles may therefore aid both Andeans and Europeans in an altitude dependent fashion.

Automated Quantification of Blood Loss versus Visual Estimation in 274 Vaginal Deliveries

OBJECTIVE

The aim of the study is to compare quantified blood loss measurement (QBL) using an automated system (Triton QBL, Menlo Park, CA) with visual blood loss estimation (EBL) during vaginal delivery.

STUDY DESIGN

During 274 vaginal deliveries, both QBL and EBL were determined. The automated system batch weighs blood containing sponges, towels, pads, and other supplies and automatically subtracts their dry weights and also the measured amount of amniotic fluid. Each method was performed independently, and clinicians were blinded to the device's results.

RESULTS

Median QBL (339 mL [217-515]) was significantly greater than median EBL (300 mL [200-350]; p < 0.0001). The Pearson's correlation between EBL and QBL was poor (r = 0.520) and the Bland-Altman's limits of agreement were wide (>900 mL). QBL measured blood loss >500 mL occurred in 73 (26.6%) patients compared with 14 (5.1%) patients using visual estimation (p < 0.0001). QBL ≥  1,000 mL was recorded in 11 patients (4.0%), whereas only one patient had an EBL blood loss of 1,000 mL and none had EBL >1,000 mL (p = 0.002).

CONCLUSION

Automated QBL recognizes more patients with excessive blood loss than visual estimation. To realize the value of QBL, clinicians must accept the inadequacy of visual estimation and implement protocols based on QBL values. Further studies of clinical outcomes related to QBL are needed.

KEY POINTS

· QBL detects hemorrhage more frequently than visual estimation.. · Median QBL is significantly greater than median EBL.. · There is poor agreement between QBL and EBL..

Trophoblast invasion: Lessons from abnormally invasive placenta (placenta accreta)

The invasion of the uterine wall by extravillous trophoblast is acknowledged as a crucial component of the establishment of pregnancy however, the only part of this process that has been clearly identified is the differentiation of cytotrophoblast (CTB) into the invasive extravillous trophoblast (EVT). The control of invasion, both initiation and termination, have yet to be elucidated and even the mechanism of differentiation is unclear. This review describes our studies which are designed to characterize the intracellular mechanisms that drive differentiation. We have used the over-invasion observed in abnormally invasive placenta (AIP; placenta accreta) to further interrogate this mechanism. Our results show that first trimester CTB to EVT differentiation is accomplished via an epithelial-mesenchymal transition (EMT), with EVT displaying a metastable, mesenchymal phenotype. In the third trimester, while the invasiveness of the EVT is lost, these cells still demonstrate signs of the EMT, albeit diminished. EVT isolated from AIP pregnancies do not however, show the same degree of reduction in EMT shown by normal third trimester cells. They exhibit a more mesenchymal phenotype, consistent with a legacy of greater invasiveness. The master regulatory transcription factor controlling the EMT appears, from the observational data, to be ZEB2 (zinc finger E-box binding protein 2). We verified this by overexpressing ZEB2 in the BeWo and JEG3 trophoblast cell lines and showing that they became more stellate in shape, up-regulated the expression of EMT-associated genes and demonstrated a substantially increased degree of invasiveness. The identification of the differentiation mechanism will enable us to identify the factors controlling invasion and those aberrant processes which generate the abnormal invasion seen in pathologies such as AIP and preeclampsia.

Human placental GLUT1 glucose transporter expression and the fetal insulin-like growth factor axis in pregnancies complicated by diabetes

We have previously described regulation of syncytial GLUT1 glucose transporters by IGF-I. Despite this, it is not clear what signal regulates transplacental glucose transport. In this report we asked whether changes in GLUT1 expression and glucose transport activity in diabetic pregnancies were associated with alterations in the fetal IGF axis. Cord blood samples and paired syncytial microvillous and basal membranes were isolated from normal term pregnancies and pregnancies characterized by gestational diabetes type A2 (GDM A2) and pre-existing insulin-dependent diabetes mellitus (IDDM). Circulating IGF-I, basal membrane GLUT1 expression and glucose transporter activity were correlated with birth weight, but only in control, not diabetic groups. Basal membrane GLUT1 and transporter activity were correlated with IGF-I concentrations in control, but not diabetic groups. IGF binding protein (IGFBP) binding capacity showed a ≥50% reduction in the diabetic groups compared to control; both showed a higher level of free IGF-I. The absence of a correlation between birth weight and factors such as fetal IGF-I or GLUT1 expression in the diabetic groups suggests that IGF-I-stimulated effects may have reached a limiting threshold, such that further increases in IGF-I (or GLUT1) are without effect. These data support that fetal IGF-I acts as a fetal nutritional signal, modulating placental GLUT1 expression and birth weight via altered levels of fetal circulating IGFBPs. Diabetes appears to exert its effects on fetal and placental factors prior to the third trimester and, despite good glycemic control immediately prior to, and in the third trimester, these effects persist to term.

Accurate Assessment of Blood Loss during Cesarean Delivery Improves Estimation of Postoperative Hemoglobin

OBJECTIVE

To determine if accurate blood loss determination during cesarean delivery can improve the prediction of postoperative hemoglobin levels.

STUDY DESIGN

This is a retrospective cohort study using visually estimated blood loss (traditional, n = 2,025) versus estimates using a mobile application that photographs sponges and canisters and calculates their hemoglobin content (device, n = 756).

RESULTS

The correlation between the actual and predicted postoperative day 1 hemoglobin value (PPO1 Hgb) was better in the device group (R ² = 0.519, correlation = 0.720) than in the traditional group (R ² = 0.429, correlation = 0.655) (p = 0.005). For patients in the device group where the estimated blood loss was >1,000 mL (n = 53), the PPO1 Hgb was also better correlated with the actual value (R ² = 0.319, correlation = 0.565) than the predictions using visually estimated blood loss for those patients in the device group whose visual estimation was >1,000 mL (n = 32) (R ² = 0.035, correlation = 0.187) (p = 0.027).

CONCLUSION

Implementation of a device that accurately measures blood loss allows for a better prediction of postoperative day 1 hemoglobin concentration than is possible using visual blood loss estimation. This improvement was seen in the entire patient group and was particularly prominent in patients with blood losses of > 1,000 mL.

ZEB2, a master regulator of the epithelial-mesenchymal transition, mediates trophoblast differentiation

STUDY QUESTION

Does the upregulation of the zinc finger E-box binding homeobox 2 (ZEB2) transcription factor in human trophoblast cells lead to alterations in gene expression consistent with an epithelial-mesenchymal transition (EMT) and a consequent increase in invasiveness?

SUMMARY ANSWER

Overexpression of ZEB2 results in an epithelial-mesenchymal shift in gene expression accompanied by a substantial increase in the invasive capacity of human trophoblast cells.

WHAT IS KNOWN ALREADY

In-vivo results have shown that cytotrophoblast differentiation into extravillous trophoblast involves an epithelial-mesenchymal transition. The only EMT master regulatory factor which shows changes consistent with extravillous trophoblast EMT status and invasive capacity is the ZEB2 transcription factor.

STUDY DESIGN, SIZE, DURATION

This study is a mechanistic investigation of the role of ZEB2 in trophoblast differentiation. We generated stable ZEB2 overexpression clones using the epithelial BeWo and JEG3 choriocarcinoma lines. Using these clones, we investigated the effects of ZEB2 overexpression on the expression of EMT-associated genes and proteins, cell morphology and invasive capability.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We used lentiviral transduction to overexpress ZEB2 in BeWo and JEG3 cells. Stable clones were selected based on ZEB2 expression and morphology. A PCR array of EMT-associated genes was used to probe gene expression. Protein measurements were performed by western blotting. Gain-of-function was assessed by quantitatively measuring cell invasion rates using a Transwell assay, a 3D bioprinted placenta model and the xCelligenceTM platform.

MAIN RESULTS AND THE ROLE OF CHANCE

The four selected clones (2 × BeWo, 2 × JEG3, based on ZEB2 expression and morphology) all showed gene expression changes indicative of an EMT. The two clones (1 × BeWo, 1 × JEG3) showing >40-fold increase in ZEB2 expression also displayed increased ZEB2 protein; the others, with increases in ZEB2 expression <14-fold did not. The two high ZEB2-expressing clones demonstrated robust increases in invasive capacity, as assessed by three types of invasion assay. These data identify ZEB2-mediated transcription as a key mechanism transforming the epithelial-like trophoblast into cells with a mesenchymal, invasive phenotype.

LARGE SCALE DATA

PCR array data have been deposited in the GEO database under accession number GSE116532.

LIMITATIONS, REASONS FOR CAUTION

These are in-vitro studies using choriocarcinoma cells and so the results should be interpreted in view of these limitations. Nevertheless, the data are consistent with in-vivo findings and are replicated in two different cell lines.

WIDER IMPLICATIONS OF THE FINDINGS

The combination of these data with the in-vivo findings clearly identify ZEB2-mediated EMT as the mechanism for cytotrophoblast differentiation into extravillous trophoblast. Having characterized these cellular mechanisms, it will now be possible to identify the intracellular and extracellular regulatory components which control ZEB2 and trophoblast differentiation. It will also be possible to identify the aberrant factors which alter differentiation in invasive pathologies such as preeclampsia and abnormally invasive placenta (AKA accreta, increta, percreta).

STUDY FUNDING AND COMPETING INTEREST(s)

Funding was provided by the Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine and Surgery at Hackensack Meridian Health, Hackensack, NJ. The 3D bioprinted placental model work done in Drs Kim and Fisher's labs was supported by the Children's National Medical Center. The xCELLigence work done in Dr Birge's lab was supported by NIH CA165077. The authors declare no competing interests.

Preoperative cystoscopy could determine the severity of placenta accreta spectrum disorders: An observational study

AIM

In the surgical treatment of placenta accreta spectrum disorders, cystoscopy for prophylactic stent placement is performed to protect the ureters from potential injury. Despite its frequent use, the use of cystoscopy in assessing the severity of these disorders has not been explored. Our objective was to find out if the abnormal findings documented during cystoscopy are associated with disease severity.

METHODS

In this retrospective, observational cohort study (n = 56), the bladder wall was evaluated at the time of ureteral stent placement via cystoscopy in prenatally diagnosed placenta accreta spectrum cases. Three abnormal findings were commonly present in these cases: bulging of the posterior bladder wall, neovascularization and arterial pulsatility in the area of neovascularization. These findings were stratified according to severity in histologically confirmed specimens. Continuous variables were compared via two-tailed t-tests and Wilcoxon rank sum tests. Categorical data were evaluated using logistic regression analysis.

RESULTS

Neovascularization affected 84%, bulging 71% and pulsatility 54% of the cases. Bulging and neovascularization increased with disease severity. Pulsatility occurred exclusively in percretas. Bulging was associated with a 12-fold (OR = 11.6, 95% CI 2.94-46.33, P = 0.0005) increased likelihood of percreta and neovascularization with a 17-fold (OR = 17.06, 95% CI 2.98-97.79, P = 0.0014) increase. Neovascularization and/or the presence of bulging of the bladder have high positive predictive value for placenta increta and percreta (91.5% and 95.0%, respectively). Cystoscopy can be used to assess the severity of placenta accreta spectrum cases preoperatively, especially when placentation is over the previous uterine scar and is in proximity to the bladder wall.

Increased incidence of respiratory distress syndrome in neonates of mothers with abnormally invasive placentation

BACKGROUND

The incidence of abnormally invasive placentation (AIP) is increasing. Most of these pregnancies are delivered preterm. We sought to characterize neonatal outcomes in AIP pregnancies.

METHODS

In this retrospective case-control study (2006-2015), AIP neonates (n = 108) were matched to two controls each for gestational age, antenatal glucocorticoid exposure, sex, plurity, and delivery mode. Medical records were reviewed for neonatal and maternal characteristics/outcomes. Univariate and multivariate Poisson regressions were performed to determine relative risk ratios (RR).

RESULTS

There were no mortalities. All neonatal outcomes were similar except for respiratory distress syndrome (RDS), which affected 37% of AIP neonates (versus 21% of controls). AIP neonates required respiratory support (64.8% vs. 51.9%) and continuous positive airway pressure (53.7% vs. 42.1%) for a longer duration. Univariate regression yielded elevated RRs for RDS for AIP (RR 1.78, 95% CI 1.24-2.54), placenta previa (RR = 1.94, 95% CI 1.36-2.76), and placenta previa with bleeding (RR 2.29, 95% CI 1.36-3.86). One episode of bleeding had a RR of 2.43 (95% CI 1.57-3.76), 2 or more episodes had a RR of 2.95 (95% CI 1.96-4.44), and bleeding/abruption as the delivery indication had a RR of 2.57 (95% CI 1.82-3.64). A multivariate regression stratifying for AIP and evaluating the combined and individual associations of AIP, bleeding, placenta previa, and GA, resulted in elevated RRs for placenta previa alone (RR 2.16, 95% CI 1.15-4.06) and placenta previa and bleeding (RR 1.69, 95% CI 1.001-2.85).

CONCLUSIONS

The increased incidence of RDS at later gestational ages in AIP is driven by placenta previa. AIP neonates required respiratory support for a longer duration than age-matched controls. Providers should be prepared to counsel expectant parents and care for affected neonates.

Clinical Experience with the Implementation of Accurate Measurement of Blood Loss during Cesarean Delivery: Influences on Hemorrhage Recognition and Allogeneic Transfusion

OBJECTIVE

This article compares hemorrhage recognition and transfusion using accurate, contemporaneous blood loss measurement versus visual estimation during cesarean deliveries.

STUDY DESIGN

A retrospective cohort study using visually estimated blood loss (traditional, n = 2,025) versus estimates using a mobile application that photographs sponges and canisters and calculates their hemoglobin content (device, n = 756).

RESULTS

Blood loss > 1,000 mL was recognized in 1.9% of traditional visual estimation patients, while measured blood loss of > 1,000 mL occurred in 8.2% of device patients (p < 0.0001). In both groups, this was accompanied by a greater decrease in transfusion-adjusted hemoglobin levels than occurred in patients without hemorrhage (p < 0.0001). Despite similar transfusion rates (1.6% in both groups), fewer red cell units were given to transfused patients in the device group (1.83 ± 0.58 versus 2.56 ± 1.68 units; p = 0.038). None of the patients in the device group received plasma or cryoprecipitate. Seven patients in the traditional group received these products (p = 0.088). Device use was associated with shorter hospital stays (4.0 ± 2.3 versus 4.4 ± 2.9 days; p = 0.0006).

CONCLUSION

The device identified hemorrhages more frequently than visual estimation. Device-detected hemorrhages appeared clinically relevant. Blood product transfusion was reduced possibly due to earlier recognition and treatment, although further studies are needed to verify the conclusion.

Prophylactic Hypogastric Artery Ligation during Placenta Percreta Surgery: A Retrospective Cohort Study

Objective  To evaluate if prophylactic hypogastric artery ligation (HAL) decreases surgical blood loss and blood products transfused. Study Design  This is a retrospective cohort study comparing patients with placenta percreta undergoing prophylactic HAL at the time of cesarean hysterectomy versus those who did not. Data were presented as means ± standard deviations, proportions, or medians with interquartile ranges. Demographic and clinical data were compared in the groups using Student's t -test for normally distributed data or the Mann-Whitney U test for nonnormally distributed data. Fisher's exact test was used for proportions and categorical variables. Data are reported as significant where p was <0.05. Results  There were 26 patients included in the control group with no HAL and 11 patients included in the study group. Estimated blood loss for the study group was 1,000 mL versus 800 mL in the control. Units of PRCBs transfused were 4.5 units in the study group versus 2 units for the control group. None of these measures were found to be statistically significant. Conclusion  Our data suggest there was no benefit in the use of prophylactic HAL in decreasing surgical blood loss or amount of blood products transfused in patients who had a cesarean hysterectomy performed for placenta percreta. Précis  Prophylactic HAL does not decrease blood loss during surgery for placenta percreta.

Serial Uterine Artery Embolization for the Treatment of Placenta Percreta in the First Trimester: A Case Report

Two patients with placenta percreta underwent uterine artery embolization (UAE) for abnormally invasive placenta (AIP) in the first trimester. Patient 1 had a 9-week cervical ectopic, while Patient 2 had a 9-week cesarean scar pregnancy. Elective termination of pregnancy was performed in both patients. UAE was performed with tris-acryl gelatin microspheres as well as gelfoam until stasis and was repeated in cases of revascularization. Both patients were followed with US/MRI/MRA scans and β-hCG levels. Revascularization occurred in both patients following UAE, requiring multiple embolizations to achieve complete placental involution. Serial bland UAE may be an effective technique in the treatment of first-trimester AIP, with the distinct advantage of maintaining a patient's fertility.

LEVEL OF EVIDENCE

Level IV.

The importance of bladder volume in the ultrasound diagnosis of placenta accreta spectrum disorders

OBJECTIVE

To assess how a quantifiable measure of vascularity-i.e. abnormal confluence (A_con ) in the subplacental myometrium observed by three-dimensional power-Doppler ultrasonography-changes with different bladder volumes.

METHODS

In a prospective observational study, women referred to a tertiary UK center with suspected PAS disorders were recruited between August 2016 and May 2017. The largest area of confluent three-dimensional power-Doppler signal (A_con ) at the uteroplacental interface was estimated under two bladder volumes differing by at least 200 mL.

RESULTS

A_con was calculated for 14 women, of whom seven were subsequently found to have PAS disorders. For these seven women, log(A_con ) was significantly greater when measured with a filled bladder than when measured with an unfilled bladder (P<0.001).

CONCLUSION

Objective evidence was found for a quantifiable difference in vascularity in the myometrium with bladder volume among women with PAS disorders. This difference has sufficient magnitude to influence the potential of A_con as a diagnostic marker.

Application of a novel mass spectrometric (MS) method to examine exposure to Bisphenol-A and common substitutes in a maternal fetal cohort

The use of Bisphenol A (BPA) has widely been replaced in consumer products by analogs BPB, BPE, BPF, BPS, and BPAF. Recent studies have linked these substitutes to similar adverse health outcomes as BPA, including disruption of endocrine pathways in animal and human studies. We designed a novel MS method, developed specifically for this study, to capture the most relevant BPA alternatives, BPB, BPE, BPF, BPS, BPAF and 4-NP in human blood and urine to quantify potential in utero exposures. To our knowledge, this is the first study to explore in utero exposure to these BPA analogs and the first U.S. study to test for BPA in maternal/fetal pairs. The method was run on 30 paired maternal urine and fetal cord blood samples from mothers undergoing elective Caesarean sections. 90% of mothers and 77% of babies tested positive for at least one BP analog. 83% of mothers tested positive for BPAF, 60% for BPS, 57% for BPB, 17% for BPF and 7% for BPA. 57% of babies tested positive for BPAF and 50% for BPF. BPA and BPB were detected in one cord blood sample each. BPS was not detected in cord blood. BPE was not detected in any fetal cord blood or maternal urine samples. These findings demonstrate the pervasiveness of some BP analogs in pregnant women and their babies at birth.

Down-regulation of the placental BCRP/ABCG2 transporter in response to hypoxia signaling

INTRODUCTION

The BCRP/ABCG2 efflux transporter protects the developing fetus by limiting the transplacental transfer of drugs and chemicals and prevents the apoptosis of trophoblasts. The purpose of this study was to determine whether hypoxia-related signaling alters placental BCRP expression and function in vitro and in human pregnancies.

METHODS

Human BeWo choriocarcinoma cells were treated with the hypoxia mimetic, cobalt chloride (CoCl₂), or 3% oxygen for 24-48 h. Activation of HIF-1α signaling and regulation of BCRP was assessed using qPCR, ELISA, western blotting and a fluorescent substrate transport assay. In addition, healthy term placentas from high altitude pregnancies with chronic hypoxia were assessed for BCRP expression.

RESULTS

CoCl₂ and 3% oxygen increased HIF-1α protein signaling and decreased the mRNA and protein expression of BCRP by 30-75% in BeWo cells. Reduced BCRP expression corresponded with impaired efflux activity during hypoxia as evidenced by accumulation of the substrate Hoechst 33342. A number of transcription factors known to regulate BCRP, including AHR, NRF2 and PPARγ, were also coordinately down-regulated by 3% oxygen in BeWo cells. Moreover, women who gave birth at a high altitude (3100 m) exhibited signs of chronic placental hypoxia, including enhanced protein expression of the HIF-1α target GLUT1, and had reduced BCRP levels in microvillous membranes compared to women at a moderate altitude (1600 m).

DISCUSSION

This study provides novel insight into the regulation of the placental BCRP transporter by hypoxia, which may be important for exposure of the fetus to chemicals during early development and in hypoxia-related pregnancy disorders.

Placental origins of adverse pregnancy outcomes: potential molecular targets: an Executive Workshop Summary of the Eunice Kennedy Shriver National Institute of Child Health and Human Development

Although much progress is being made in understanding the molecular pathways in the placenta that are involved in the pathophysiology of pregnancy-related disorders, a significant gap exists in the utilization of this information for the development of new drug therapies to improve pregnancy outcome. On March 5-6, 2015, the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health sponsored a 2-day workshop titled Placental Origins of Adverse Pregnancy Outcomes: Potential Molecular Targets to begin to address this gap. Particular emphasis was given to the identification of important molecular pathways that could serve as drug targets and the advantages and disadvantages of targeting these particular pathways. This article is a summary of the proceedings of that workshop. A broad number of topics were covered that ranged from basic placental biology to clinical trials. This included research in the basic biology of placentation, such as trophoblast migration and spiral artery remodeling, and trophoblast sensing and response to infectious and noninfectious agents. Research findings in these areas will be critical for the formulation of the development of future treatments and the development of therapies for the prevention of a number of pregnancy disorders of placental origin that include preeclampsia, fetal growth restriction, and uterine inflammation. Research was also presented that summarized ongoing clinical efforts in the United States and in Europe that has tested novel interventions for preeclampsia and fetal growth restriction, including agents such as oral arginine supplementation, sildenafil, pravastatin, gene therapy with virally delivered vascular endothelial growth factor, and oxygen supplementation therapy. Strategies were also proposed to improve fetal growth by the enhancement of nutrient transport to the fetus by modulation of their placental transporters and the targeting of placental mitochondrial dysfunction and oxidative stress to improve placental health. The roles of microRNAs and placental-derived exosomes, as well as messenger RNAs, were also discussed in the context of their use for diagnostics and as drug targets. The workshop discussed the aspect of safety and pharmacokinetic profiles of potential existing and new therapeutics that will need to be determined, especially in the context of the unique pharmacokinetic properties of pregnancy and the hurdles and pitfalls of the translation of research findings into practice. The workshop also discussed novel methods of drug delivery and targeting during pregnancy with the use of macromolecular carriers, such as nanoparticles and biopolymers, to minimize placental drug transfer and hence fetal drug exposure. In closing, a major theme that developed from the workshop was that the scientific community must change their thinking of the pregnant woman and her fetus as a vulnerable patient population for which drug development should be avoided, but rather be thought of as a deprived population in need of more effective therapeutic interventions.

Cesarean scar pregnancy is a precursor of morbidly adherent placenta

OBJECTIVE

To provide further sonographic, clinical and histological evidence that Cesarean scar pregnancy (CSP) is a precursor to and an early form of second- and third-trimester morbidly adherent placenta (MAP).

METHODS

This is a report of 10 cases of CSP identified early, in which the patients decided to continue the pregnancy, following counseling that emphasized the possibility of both significant pregnancy complications and a need for hysterectomy. Pregnancies were followed at 2-4-week intervals with ultrasound scans and customary monitoring. The aim was for patients to reach near term or term and then undergo elective Cesarean delivery and, if necessary, hysterectomy. Charts, ultrasound images, operative reports and histopathological examinations of the placentae were reviewed.

RESULTS

The ultrasound diagnosis of CSP was made before 10 weeks. By the second trimester, all patients exhibited sonographic signs of MAP. Nine of the 10 patients delivered liveborn neonates between 32 and 37 weeks. In the tenth pregnancy, progressive shortening of the cervix and intractable vaginal bleeding prompted termination, with hysterectomy, at 20 weeks. Two other patients in the cohort had antepartum complications (bleeding at 33 weeks in one case and contractions at 32 weeks in the other). All patients underwent hysterectomy at the time of Cesarean delivery, with total blood loss ranging from 300 to 6000 mL. Placenta percreta was the histopathological diagnosis in all 10 cases.

CONCLUSION

The cases in this series validate the hypothesis that CSP is a precursor of MAP, both sharing the same histopathology. Our findings provide evidence that can be used to counsel patients with CSP, to enable them to make an informed choice between first-trimester termination and continuation of the pregnancy, with its risk of premature delivery and loss of uterus and fertility.

Regulation of human trophoblast GLUT1 glucose transporter by insulin-like growth factor I (IGF-I)

Glucose transport to the fetus across the placenta takes place via glucose transporters in the opposing faces of the barrier layer, the microvillous and basal membranes of the syncytiotrophoblast. While basal membrane content of the GLUT1 glucose transporter appears to be the rate-limiting step in transplacental transport, the factors regulating transporter expression and activity are largely unknown. In view of the many studies showing an association between IGF-I and fetal growth, we investigated the effects of IGF-I on placental glucose transport and GLUT1 transporter expression. Treatment of BeWo choriocarcinoma cells with IGF-I increased cellular GLUT1 protein. There was increased basolateral (but not microvillous) uptake of glucose and increased transepithelial transport of glucose across the BeWo monolayer. Primary syncytial cells treated with IGF-I also demonstrated an increase in GLUT1 protein. Term placental explants treated with IGF-I showed an increase in syncytial basal membrane GLUT1 but microvillous membrane GLUT1 was not affected. The placental dual perfusion model was used to assess the effects of fetally perfused IGF-I on transplacental glucose transport and syncytial GLUT1 content. In control perfusions there was a decrease in transplacental glucose transport over the course of the perfusion, whereas in tissues perfused with IGF-I through the fetal circulation there was no change. Syncytial basal membranes from IGF-I perfused tissues showed an increase in GLUT1 content. These results demonstrate that IGF-I, whether acting via microvillous or basal membrane receptors, increases the basal membrane content of GLUT1 and up-regulates basal membrane transport of glucose, leading to increased transepithelial glucose transport. These observations provide a partial explanation for the mechanism by which IGF-I controls nutrient supply in the regulation of fetal growth.

Maternal and fetoplacental hypoxia do not alter circulating angiogenic growth effectors during human pregnancy

One causal model of preeclampsia (PE) postulates that placental hypoxia alters the production of angiogenic growth effectors (AGEs), causing an imbalance leading to maternal endothelial cell dysfunction. We tested this model using the natural experiment of high-altitude (HA) residence. We hypothesized that in HA pregnancies 1) circulating soluble fms-like tyrosine kinase 1 (sFlt-1) is increased and placental growth factor (PlGF) decreased, and 2) AGE concentrations correlate with measures of hypoxia. A cross-sectional study of healthy pregnancies at low altitude (LA) (400 m) versus HA (3600 m) compared normal (n = 80 at HA, n = 90 at LA) and PE pregnancies (n = 20 PE at HA, n = 19 PE at LA). Blood was collected using standard serum separation and, in parallel, by a method designed to inhibit platelet activation. AGEs were measured by enzyme-linked immunosorbent assays. AGEs did not differ between altitudes in normal or PE pregnancies. AGE concentrations were unrelated to measures of maternal or fetal hypoxia. PlGF was lower and sFlt-1 higher in PE, but overlapped considerably with the range observed in normal samples. PlGF correlated with placental mass in both normal and PE pregnancies. The contribution of peripheral cells to the values measured for AGEs was similar at LA and HA, but was greater in PE than in normotensive women. Hypoxia, across a wide physiological range in pregnancy, does not alter levels of circulating AGEs in otherwise normal pregnancies. Peripheral cell release of AGEs with the hemostasis characteristic of standard blood collection is highly variable and contributes to a doubling of the amount of sFlt-1 measured in PE as compared to normal pregnancies.

Maternal and fetal outcomes in placenta accreta after institution of team-managed care

INTRODUCTION

Placenta accreta significantly contributes to maternal morbidity and mortality. We evaluated whether planned delivery and experienced, team-managed surgical intervention results in improved outcomes. We also examined whether risk factors differed for accreta, increta, and percreta and evaluated whether excess lower segment uterine vascularity correlates with disease severity.

METHODS

We retrospectively analyzed patients before versus after institution of a management protocol. Of the 58 044 deliveries over 10 years, there were 67 women whose pregnancies were histopathologically confirmed as placenta accreta, increta, or percreta (1/866). Clinical outcome measures were estimated blood loss (EBL), packed red blood cells (pRBCs) transfused, maternal and fetal complications, intensive care unit admission, and length of stay.

RESULTS

There were no maternal or infant deaths. In the managed cohort, EBL was reduced by 48% (P < .001), intraoperative pRBCs transfused by 40% (P < .01), total transfused pRBCs per case by 50% (P < .01), and surgical intensive care unit admissions by >50% (P < .01). Assessment of maternal risk factors by diagnosis revealed marked differences between accreta versus increta and percreta. Clinically assessed excess vascularity of the lower uterine segment correlated with disease severity. The incidence of neonatal complications was similar in both cohorts.

CONCLUSIONS

Targeted delivery at 34 weeks and team-managed diagnosis, treatment, and care of patients with placenta accreta were associated with improved maternal, but not neonatal outcomes.

Evidence for extraplacental sources of circulating angiogenic growth effectors in human pregnancy

Pregnancy complications such as preeclampsia (PE) and intrauterine growth restriction (IUGR) are associated with reduced blood flow, contributing to placental and fetal hypoxia. Placental hypoxia is thought to cause altered production of angiogenic growth effectors (AGEs), reflected in the circulation of mother and fetus. Vascular endothelial growth factor (VEGF), placental growth factor (PlGF) and their soluble binding protein (sFlt-1) are, in turn, postulated as being causally involved in PE via induction of systemic endothelial cell dysfunction. To dissect the role of AGEs, accurate measurement is of great importance. However, the values of AGEs are highly variable, contributing to heterogeneity in their association (or lack thereof) with preeclampsia. To test the hypothesis that variability may be due to peripheral cell release of AGEs we obtained blood samples from normal healthy pregnant women (n = 90) and the cord blood of a subset of their neonates using standard serum separation and compared results obtained in parallel samples collected into reagents designed to inhibit peripheral cell activation (sodium citrate, theophylline, adenosine and dipyridamole-CTAD). AGEs were measured by ELISA. CTAD collection reduced maternal and fetal free VEGF by 83%, and 98%, respectively. Free PlGF was decreased by 29%, maternal sFlt-1 by >20% and fetal sFlt-1 by 59% in the CTAD-treated vs. serum sample (p < 0.0001). In summary blood collection techniques can profoundly alter measured concentrations of AGEs in mother and fetus. This process is highly variable, contributes to variation reported in the literature, and renders questionable the true impact of alteration in AGEs on pregnancy pathologies.

Global protein synthesis in human trophoblast is resistant to inhibition by hypoxia

Placental growth and function depend on syncytial cell processes which require the continuing synthesis of cellular proteins. The substantial energy demands of protein synthesis are met primarily from oxidative metabolism. Although the responses of individual proteins produced by the syncytiotrophoblast to oxygen deprivation have been investigated previously, there is no information available on global protein synthesis in syncytiotrophoblast under conditions of hypoxia. These studies were designed to test the hypothesis that syncytial protein synthesis is decreased in a dose-dependent manner by hypoxia. Experiments were performed to measure amino acid incorporation into proteins in primary syncytiotrophoblast cells exposed to oxygen concentrations ranging from 0 to 10%. Compared to cells exposed to normoxia (10% O₂), no changes were observed following exposure to 5% or 3% O₂, but after exposure to 1% O₂, protein synthesis after 24 and 48 h decreased by 24% and 23% and with exposure to 0% O₂, by 65% and 50%. As a consequence of these results, we hypothesized that global protein synthesis in conditions of severe hypoxia was being supported by glucose metabolism. Additional experiments were performed therefore to examine the role of glucose in supporting protein synthesis. These demonstrated that at each oxygen concentration there was a significant, decreasing linear trend in protein synthesis as glucose concentration was reduced. Under conditions of near-anoxia and in the absence of glucose, protein synthesis was reduced by >85%. Even under normoxic conditions (defined as 10% O₂) and in the presence of oxidative substrates, reductions in glucose were accompanied by decreases in protein synthesis. These experiments demonstrate that syncytiotrophoblast cells are resistant to reductions in protein synthesis at O₂ concentrations greater than 1%. This could be explained by our finding that a significant fraction of protein synthesis in the syncytiotrophoblast is sustained by glycolytic metabolism. This suggests that with increasing degrees of chronic hypoxia there is a shift from oxidative to glycolytic pathways, allowing a substantial degree of protein synthesis to be maintained.

Glucose transporter 3 (GLUT3) protein expression in human placenta across gestation

Conflicting information regarding expression of GLUT3 protein in the human placenta has been reported and the localization and pattern of expression of GLUT3 protein across gestation has not been clearly defined. The objective of this study was characterization of syncytial GLUT3 protein expression across gestation. We hypothesized that GLUT3 protein is present in the syncytial microvillous membrane and that its expression decreases over gestation. GLUT3 protein was measured in samples from a range of gestational ages (first to third trimester), with human brain and human bowel used as a positive and negative control respectively. As an additional measure of specificity, we transfected BeWo choriocarcinoma cells, a trophoblast cell line expressing GLUT3, with siRNA directed against GLUT3 and analyzed expression by Western blotting. GLUT3 was detected in the syncytiotrophoblast at all gestational ages by immunohistochemistry. Using Western blotting GLUT3 was detected as an integral membrane protein at a molecular weight of ∼50 kDa in microvillous membranes from all trimesters but not in syncytial basal membranes. The identity of the primary antibody target was confirmed by demonstrating that expression of the immunoblotting signal in GLUT3 siRNA-treated BeWo was decreased to 18 ± 6% (mean ± SEM) of that seen in cells transfected with a non-targeting siRNA. GLUT3 expression in microvillous membranes detected by Western blot decreased through the trimesters such that expression in the second trimester (wks 14-26) was 48 ± 7% of that in the first trimester and by the third trimester (wks 31-40) only 34 ± 10% of first trimester expression. In addition, glucose uptake into BeWo cells treated with GLUT3 siRNA was reduced to 60% of that measured in cells treated with the non-targeting siRNA. This suggests that GLUT3-mediated uptake comprises approximately 50% of glucose uptake into BeWo cells. These results confirm the hypothesis that GLUT3 is present in the syncytial microvillous membrane early in gestation and decreases thereafter, supporting the idea that GLUT3 is of greater importance for glucose uptake early in gestation.

IFPA Meeting 2010 Workshops Report II: Placental pathology; trophoblast invasion; fetal sex; parasites and the placenta; decidua and embryonic or fetal loss; trophoblast differentiation and syncytialisation

Workshops are an important part of the IFPA annual meeting. At IFPA Meeting 2010 diverse topics were discussed in twelve themed workshops, six of which are summarized in this report. 1. The placental pathology workshop focused on clinical correlates of placenta accreta/percreta. 2. Mechanisms of regulation of trophoblast invasion and spiral artery remodeling were discussed in the trophoblast invasion workshop. 3. The fetal sex and intrauterine stress workshop explored recent work on placental sex differences and discussed them in the context of whether boys live dangerously in the womb.4. The workshop on parasites addressed inflammatory responses as a sign of interaction between placental tissue and parasites. 5. The decidua and embryonic/fetal loss workshop focused on key regulatory mediators in the decidua, embryo and fetus and how alterations in expression may contribute to different diseases and adverse conditions of pregnancy. 6. The trophoblast differentiation and syncytialisation workshop addressed the regulation of villous cytotrophoblast differentiation and how variations may lead to placental dysfunction and pregnancy complications.

Placental metabolic reprogramming: do changes in the mix of energy-generating substrates modulate fetal growth?

Insufficient oxygen leads to the cessation of growth in favor of cellular survival. Our unique model of high-altitude human pregnancy indicates that hypoxia-induced reductions in fetal growth occur at higher levels of oxygen than previously described. Fetal PO(2) is surprisingly high and fetal oxygen consumption unaffected by high altitude, whereas fetal glucose delivery and consumption decrease. Placental delivery of energy-generating substrates to the fetus is thus altered by mild hypoxia, resulting in maintained fetal oxygenation but a relative fetal hypoglycemia. Our data point to this altered mix of substrates as a potential initiating factor in reduced fetal growth, since oxygen delivery is adequate. These data support the existence, in the placenta, of metabolic reprogramming mechanisms, previously documented in tumor cells, whereby HIF-1 stimulates reductions in mitochondrial oxygen consumption at the cost of increased glucose consumption. Decreased oxygen consumption is not due to substrate (oxygen) limitation but rather results from active inhibition of mitochondrial oxygen utilization. We suggest that under hypoxic conditions, metabolic reprogramming in the placenta decreases mitochondrial oxygen consumption and increases anerobic glucose consumption, altering the mix of energy-generating substrates available for transfer to the fetus. Increased oxygen is available to support the fetus, but at the cost of less glucose availability, leading to a hypoglycemia-mediated decrease in fetal growth. Our data suggest that metabolic reprogramming may be an initiating step in the progression to more severe forms of fetal growth restriction and points to the placenta as the pivotal source of fetal programming in response to an adverse intrauterine environment.

Hypoglycemia and the origin of hypoxia-induced reduction in human fetal growth

BACKGROUND

The most well known reproductive consequence of residence at high altitude (HA >2700 m) is reduction in fetal growth. Reduced fetoplacental oxygenation is an underlying cause of pregnancy pathologies, including intrauterine growth restriction and preeclampsia, which are more common at HA. Therefore, altitude is a natural experimental model to study the etiology of pregnancy pathophysiologies. We have shown that the proximate cause of decreased fetal growth is not reduced oxygen availability, delivery, or consumption. We therefore asked whether glucose, the primary substrate for fetal growth, might be decreased and/or whether altered fetoplacental glucose metabolism might account for reduced fetal growth at HA.

METHODS

Doppler and ultrasound were used to measure maternal uterine and fetal umbilical blood flows in 69 and 58 residents of 400 vs 3600 m. Arterial and venous blood samples from mother and fetus were collected at elective cesarean delivery and analyzed for glucose, lactate and insulin. Maternal delivery and fetal uptakes for oxygen and glucose were calculated.

PRINCIPAL FINDINGS

The maternal arterial - venous glucose concentration difference was greater at HA. However, umbilical venous and arterial glucose concentrations were markedly decreased, resulting in lower glucose delivery at 3600 m. Fetal glucose consumption was reduced by >28%, but strongly correlated with glucose delivery, highlighting the relevance of glucose concentration to fetal uptake. At altitude, fetal lactate levels were increased, insulin concentrations decreased, and the expression of GLUT1 glucose transporter protein in the placental basal membrane was reduced.

CONCLUSION/SIGNIFICANCE

Our results support that preferential anaerobic consumption of glucose by the placenta at high altitude spares oxygen for fetal use, but limits glucose availability for fetal growth. Thus reduced fetal growth at high altitude is associated with fetal hypoglycemia, hypoinsulinemia and a trend towards lactacidemia. Our data support that placentally-mediated reduction in glucose transport is an initiating factor for reduced fetal growth under conditions of chronic hypoxemia.

Where the O2 goes to: preservation of human fetal oxygen delivery and consumption at high altitude

Fetal growth is decreased at high altitude (> 2700 m). We hypothesized that variation in fetal O(2) delivery might account for both the altitude effect and the relative preservation of fetal growth in multigenerational natives to high altitude. Participants were 168 women of European or Andean ancestry living at 3600 m or 400 m. Ancestry was genetically confirmed. Umbilical vein blood flow was measured using ultrasound and Doppler. Cord blood samples permitted calculation of fetal O(2) delivery and consumption. Andean fetuses had greater blood flow and oxygen delivery than Europeans and weighed more at birth, regardless of altitude (+208 g, P < 0.0001). Fetal blood flow was decreased at 3600 m (P < 0.0001); the decrement was similar in both ancestry groups. Altitude-associated decrease in birth weight was greater in Europeans (-417 g) than Andeans (-228 g, P < 0.005). Birth weight at 3600 m was > 200 g lower for Europeans at any given level of blood flow or O(2) delivery. Fetal haemoglobin concentration was increased, decreased, and the fetal / curve was left-shifted at 3600 m. Fetuses receiving less O(2) extracted more (r(2) = 0.35, P < 0.0001). These adaptations resulted in similar fetal O(2) delivery and consumption across all four groups. Increased umbilical venous O(2) delivery correlated with increased fetal O(2) consumption per kg weight (r(2) = 0.50, P < 0.0001). Blood flow (r(2) = 0.16, P < 0.001) and O(2) delivery (r(2) = 0.17, P < 0.001) correlated with birth weight at 3600 m, but not at 400 m (r(2) = 0.04, and 0.03, respectively). We concluded that the most pronounced difference at high altitude is reduced fetal blood flow, but fetal haematological adaptation and fetal capacity to increase O(2) extraction indicates that deficit in fetal oxygen delivery is unlikely to be causally associated with the altitude- and ancestry-related differences in fetal growth.

Placental expression of soluble fms-like tyrosine kinase 1 is increased in singletons and twin pregnancies with intrauterine growth restriction

OBJECTIVE

Intrauterine growth restriction (IUGR) is characterized by decreased placental perfusion. Low oxygen has been shown to increase soluble fms-like tyrosine kinase 1 (sFlt-1) expression in the human placenta. The objective of this study was to examine sFlt-1 expression in different types of IUGR pregnancies, including early-onset severe cases characterized by abnormal umbilical and uterine artery Doppler and discordant IUGR twins in which the normal cotwin represents the optimal control because both placentas share the same uterine environment.

PATIENTS

Placentas from four subgroups were collected: early severe IUGR with umbilical artery absent end diastolic flow (n = 19), small for gestational age with normal uterine and umbilical artery Doppler (n = 11), severely growth-restricted dichorionic and monochorionic twins with abnormal umbilical artery Doppler (n = 9), preeclamptic twins (n = 3), and age-matched normal singletons (n = 19) and twin controls (n = 8).

RESULTS

Expression of sFlt-1 mRNA and protein was significantly increased in IUGR placentas compared with small for gestational age and normal control placentas. sFlt-1 expression levels were also significantly greater in the small IUGR twin placentas from discordant twin pregnancies compared with the normal cotwin. In preeclamptic twins, sFlt-1 expression was increased in only one of the two placentas.

CONCLUSIONS

Our results demonstrate that sFlt-1 expression is increased in severe IUGR placentas with abnormal umbilical artery Doppler of singletons and also in discordant IUGR twins. Reduced placental perfusion may contribute to the increased expression of sFlt-1 in IUGR pregnancies. Our data are compatible with differential sFlt-1 expression in placentas from discordant twins.

Comparison of fetal demise case series drawn from socioeconomically distinct counties in New Jersey

The causes of stillbirth were investigated in two case series drawn from distinct communities within the same geographic region in New Jersey, one characterized by affluence (Hackensack Medical Center, Bergen County) and one by poverty (University Hospital, Essex County). The data was obtained over 4 years (1998-2001) from a stillbirth autopsy service available to all obstetrics-gynecology clinicians in the northern New Jersey area. A total of 52 stillbirths from University Hospital in Newark (Essex County) and 55 from Hackensack Medical Center (Bergen County) were examined by this same autopsy service. Cause(s) were identified for 70% of stillbirth cases. Whereas population-based data revealed that the rate of stillbirths was higher in Essex and mothers of stillbirths in Essex were of younger age, greater parity, and gravidity and had higher rates of smoking, single marital status, and very low birth weight infants, the only significant difference between the two case series was infection, detected in 35% of stillbirths from University Hospital versus 14% from Hackensack. Also no difference in the incidence of stillbirth due to unknown cause was found between the case series.

Human placental hypoxia-inducible factor-1alpha expression correlates with clinical outcomes in chronic hypoxia in vivo

Placental hypoxia is causally implicated in fetal growth restriction and preeclampsia, with both occurring more frequently at high altitude (>2700 m; HA). The nuclear transcription factor hypoxia-inducible factor (HIF) may facilitate placental oxygen transport at HA by increasing erythropoiesis and placental angiogenesis. We therefore investigated HIF expression and its regulatory mechanisms in placentas from normal pregnancies at high (3100 m), moderate (1600 m), and sea level (75 m) altitudes. Moderate-altitude and sea level placentas did not differ, but HIF-1alpha and the von Hippel-Lindau tumor suppressor protein were overexpressed in HA placentas. The ability of von Hippel-Lindau tumor suppressor protein to form the E3 ubiquitin protein ligase complex, required for HIF-1alpha degradation, was unaltered in HA placentas. mRNA for factor-inhibiting HIF, a negative modulator of HIF-1alpha transactivation, was increased, but protein levels were diminished. Elevated HIF-1alpha likely contributed to the significant increase we report in HIF-1alpha downstream target proteins, transforming growth factor beta3 in the placenta, and vascular endothelial growth factor and erythropoietin in the maternal circulation. These circulating markers and lowered birth to placental weight ratios correlated with increased HIF-1alpha, thereby linking molecular and systemic physiological data. The HA response to chronic hypoxia resembles preeclampsia in several aspects, illustrating the utility of the HA model in understanding placental pathologies.

Hypoxic switch in mitochondrial myeloid cell leukemia factor-1/Mtd apoptotic rheostat contributes to human trophoblast cell death in preeclampsia

Preeclampsia, a disorder of pregnancy, is characterized by increased trophoblast cell death and altered trophoblast-mediated remodeling of myometrial spiral arteries resulting in reduced uteroplacental perfusion. Mitochondria-associated Bcl-2 family members are important regulators of programed cell death. The mechanism whereby hypoxia alters the mitochondrial apoptotic rheostat is essential to our understanding of placental disease. Herein, myeloid cell leukemia factor-1 (Mcl-1) isoform expression was examined in physiological/pathological models of placental hypoxia. Preeclamptic placentae were characterized by caspase-dependent cleavage of death-suppressing Mcl-1L and switch toward cell death-inducing Mcl-1S. In vitro, Mcl-1L cleavage was induced by hypoxia-reoxygenation in villous explants, whereas Mcl-1L overexpression under hypoxia-reoxygenation rescued trophoblast cells from undergoing apoptosis. Cleavage was mediated by caspase-3/-7 because pharmacological caspase inhibition prevented this process. Altitude-induced chronic hypoxia was characterized by expression of Mcl-1L; resulting in a reduction of apoptotic markers (cleaved caspase-3/-8 and p85 poly-ADP-ribose polymerase). Moreover, in both physiological (explants and high altitude) and pathological (preeclampsia) placental hypoxia, decreased trophoblast syncytin expression was observed. Hence, although both pathological and physiological placental hypoxia are associated with slowed trophoblast differentiation, trophoblast apoptosis is only up-regulated in preeclampsia, because of a hypoxia-reoxygenation-induced switch in generation of proapoptotic Mcl-1 isoforms.

Maternal oxygen delivery is not related to altitude- and ancestry-associated differences in human fetal growth

Fetal growth is reduced at high altitude, but the decrease is less among long-resident populations. We hypothesized that greater maternal uteroplacental O(2) delivery would explain increased fetal growth in Andean natives versus European migrants to high altitude. O(2) delivery was measured with ultrasound, Doppler and haematological techniques. Participants (n=180) were pregnant women of self-professed European or Andean ancestry living at 3600 m or 400 m in Bolivia. Ancestry was quantified using ancestry-informative single nucleotide polymorphism. The altitude-associated decrement in birth weight was 418 g in European versus 236 g in Andean women (P<0.005). Altitude was associated with decreased uterine artery diameter, volumetric blood flow and O(2) delivery regardless of ancestry. But the hypothesis was rejected as O(2) delivery was similar between ancestry groups at their respective altitudes of residence. Instead, Andean neonates were larger and heavier per unit of O(2) delivery, regardless of altitude (P<0.001). European admixture among Andeans was negatively correlated with birth weight at both altitudes (P<0.01), but admixture was not related to any of the O(2) transport variables. Genetically mediated differences in maternal O(2) delivery are thus unlikely to explain the Andean advantage in fetal growth. Of the other independent variables, only placental weight and gestational age explained significant variation in birth weight. Thus greater placental efficiency in O(2) and nutrient transport, and/or greater fetal efficiency in substrate utilization may contribute to ancestry- and altitude-related differences in fetal growth. Uterine artery O(2) delivery in these pregnancies was 99 +/- 3 ml min(-1), approximately 5-fold greater than near-term fetal O(2) consumption. Deficits in maternal O(2) transport in third trimester normal pregnancy are unlikely to be causally associated with variation in fetal growth.

Hypoxic upregulation of glucose transporters in BeWo choriocarcinoma cells is mediated by hypoxia-inducible factor-1

Placental hypoxia has been implicated in pregnancy pathologies, including fetal growth restriction and preeclampsia; however, the mechanism by which the trophoblast cell responds to hypoxia has not been adequately explored. Glucose transport, a process crucial to fetoplacental growth, is upregulated by hypoxia in a number of cell types. We investigated the effects of hypoxia on the regulation of trophoblast glucose transporter (GLUT) expression and activity in BeWo choriocarcinoma cells, a trophoblast cell model, and human placental villous tissue explants. GLUT1 expression in BeWo cells was upregulated by the hypoxia-inducing chemical agents desferroxamine and cobalt chloride. Reductions in oxygen tension resulted in dose-dependent increases in GLUT1 and GLUT3 expression. Exposure of cells to hypoxic conditions also resulted in an increase in transepithelial glucose transport. A role for hypoxia-inducible factor (HIF)-1 was suggested by the increase in HIF-1alpha as a result of hypoxia and by the increase in GLUT1 expression following treatment of BeWo with MG-132, a proteasomal inhibitor that increases HIF-1 levels. The function of HIF-1 was confirmed in experiments where the hypoxic upregulation of GLUT1 and GLUT3 was inhibited by antisense HIF-1alpha. In contrast to BeWo cells, hypoxia produced minimal increases in GLUT1 expression in explants; however, treatment with MG-132 did upregulate syncytial basal membrane GLUT1. Our results show that GLUTs are upregulated by hypoxia via a HIF-1-mediated pathway in trophoblast cells and suggest that the GLUT response to hypoxia in vivo will be determined not only by low oxygen tension but also by other factors that modulate HIF-1 levels.