Single and combined exposures to bisphenol A and benzophenone-3 during early mouse pregnancy have differential effects on fetal and placental development

Endocrine disrupting chemicals (EDCs) possess the capability to interfere with the endocrine system by binding to hormone receptors, for example on immune cells. Specific effects have already been described for individual substances, but the impact of exposure to chemical mixtures during pregnancy on maternal immune regulation, placentation and fetal development is not known. In this study, we aimed to investigate the combined effects of two widespread EDCs, bisphenol A (BPA) and benzophenone-3 (BP-3), at allowed concentrations on crucial pregnancy processes such as implantation, placentation, uterine immune cell populations and fetal growth. From gestation day (gd) 0 to gd10, female mice were exposed to 4 μg/kg/d BPA, 50 mg/kg/d BP-3 or a BPA/BP-3 mixture. High frequency ultrasound and Doppler measurements were used to determine intrauterine fetal development and hemodynamic parameters. Furthermore, uterine spiral artery remodeling and placental mRNA expression were studied via histology and CHIP-RT-PCR, respectively. Effects of EDC exposure on multiple uterine immune cell populations were investigated using flow cytometry. We found that exposure to BP-3 caused intrauterine growth restriction in offspring at gd14, while BPA and BPA/BP-3 mixture caused varying effects. Moreover, placental morphology at gd12 and placental efficiency at gd14 were altered upon BP-3 exposure. Placental gene transcription was altered particularly in female offspring after in utero exposure to BP-3. Flow cytometry analyses revealed an increase in uterine T cells and NK cells in BPA and BPA/BP-3-treated dams at gd14. Doppler measurements revealed no effect on uterine hemodynamic parameters and spiral artery remodeling was not affected following EDC exposure. Our results provide evidence that exposure to BPA and BP-3 during early gestation affects fetal development in a sex-dependent manner, placental function and immune cell frequencies at the feto-maternal interface. These results call for inclusion of studies addressing pregnancy in the risk assessment of environmental chemicals.

Connecting G protein-coupled estrogen receptor biomolecular mechanisms with the pathophysiology of preeclampsia: a review

BACKGROUND

Throughout the course of pregnancy, small maternal spiral arteries that are in contact with fetal tissue undergo structural remodeling, lose smooth muscle cells, and become less responsive to vasoconstrictors. Additionally, placental extravillous trophoblasts invade the maternal decidua to establish an interaction between the fetal placental villi with the maternal blood supply. When successful, this process enables the transport of oxygen, nutrients, and signaling molecules but an insufficiency leads to placental ischemia. In response, the placenta releases vasoactive factors that enter the maternal circulation and promote maternal cardiorenal dysfunction, a hallmark of preeclampsia (PE), the leading cause of maternal and fetal death. An underexplored mechanism in the development of PE is the impact of membrane-initiated estrogen signaling via the G protein-coupled estrogen receptor (GPER). Recent evidence indicates that GPER activation is associated with normal trophoblast invasion, placental angiogenesis/hypoxia, and regulation of uteroplacental vasodilation, and these mechanisms could explain part of the estrogen-induced control of uterine remodeling and placental development in pregnancy.

CONCLUSION

Although the relevance of GPER in PE remains speculative, this review provides a summary of our current understanding on how GPER stimulation regulates some of the features of normal pregnancy and a potential link between its signaling network and uteroplacental dysfunction in PE. Synthesis of this information will facilitate the development of innovative treatment options.

Understanding the uterine artery Doppler waveform and its relationship to spiral artery remodelling

Analysis of the uterine artery (UtA) Doppler waveform is frequently used in high-risk pregnancies to assess the likelihood of adverse pregnancy outcomes, including preeclampsia and fetal growth restriction. Whilst abnormal UtA waveforms at 18-20 weeks are associated with adverse outcomes, the underlying cause of these waveform changes remains unknown. Current evidence suggests the long-held dogma that the UtA waveform is merely a reflection of trophoblast-induced spiral artery remodelling is incorrect. Hence, the origins of the waveform changes must be reassessed. Recent data from human and animal models suggests that the arcuate arteries, placental bed arterio-venous anastomoses and, most notably, the radial arteries may be more important in determining the UtA waveform profile than previously appreciated. Furthermore, there is increasing evidence implicating the maternal cardiovascular system in the pathophysiology of the complications predicted by the waveform changes, particularly preeclampsia, and therefore its underlying association with the UtA waveform warrants further investigation.

Spiral Arteries in Second Trimester of Pregnancy: When Is It Possible to Define Expected Physiological Remodeling as Abnormal?

After undergoing remodeling, uterine spiral arteries turn into wide, flexible tubes, with low resistance. If remodeling does not occur, spontaneous abortions, intrauterine growth restriction, and pregnancy-related hypertensive disorders can ensue. Arterial transformation begins at a very early gestational stage; however, second quarter pregnancy histopathological samples have yet to pinpoint the exact moment when abnormal remodeling transpires. We examined 100 samples, taken from consecutive abortions at 12-23 gestational weeks. Following Pijnenborg and Smith guidelines, blinded pathologists analyzed clinical data on remodeling stages. Lab results showed that arterial remodeling is not synchronic in all vessels; a single sample can include various remodeling stages; neither is remodeling homogenous in a single vessel: change may be occurring in one part of the vessel, but not in another. To our knowledge, no one has published this finding. In the examined age group, Smith stage IV predominates; around week 14, substantial muscle and endothelium loss takes place. After week 17, endovascular or fibrin trophoblast does not usually occur. Although scant consensus exists on what defines preeclampsia etiology, it is clear that it involves abnormal remodeling in decidua vessels. Improved understanding requires further knowledge on both the physiological and pathological aspects of the remodeling process. We observed that muscle and endothelial tissues disappear from weeks 14-17, after which time reendothelization predominates. We list the expected proportion of spiral artery changes for each gestational age which, to date, has not been available.

Exposure to 17α-ethinyl estradiol during early pregnancy affects fetal growth and survival in mice

17α-ethinyl estradiol (EE2) is a synthetic compound widely used in the generation of contraceptive pills. EE2 is present in the urine of women taking contraceptives and its presence has been confirmed at increasing concentrations contaminating rivers all over the world. Because of this cycle, it can entry the human food chain when watering plants. A negative influence of EE2 on fertility and reproductive capacity of wildlife was already suggested. The short-term impact of exposure to contaminating EE2 on pregnancy outcome has not been addressed. Pregnant mice were exposed to either 0.005 μg (concentrations found in water) or 5 μg EE2/kg (contraceptive dose) body weight/day from gestation day 1-7 by oral gavage. Control mice received a 0.1% ethanol solution. High frequency ultrasound imaging was used to follow-up fetal and placental growth in vivo. Doppler measurements were utilized to analyze blood flow parameters in uterine and umbilical arteries. Mice were sacrificed at gd5, 10, and 14. We show that most fetuses of mothers exposed to the high EE2 dose die intrauterine at gd10, with implantation sizes beginning to be smaller already at gd8. Mothers exposed to the low EE2 dose show an impaired remodeling of the spiral arteries, a higher placental weight and pups that are large for gestational age. The insulin-like growth factor system that regulates fetal and placental growth and development is affected by the EE2 treatment. Our results show that a short-term exposure to EE2 during early pregnancy has severe consequences for fetal growth and survival depending on the dose. Exposition to synthetic estrogens affects placenta growth and angiogenesis. These findings urge to the study of mechanisms dysregulated upon environmental exposition to estrogens.

Geometric and hemodynamic characterization of uterine spiral arteries: The concept of resistance reserve

BACKGROUND

The coiled geometry of spiral arteries in the human uteroplacental circulation is a hemodynamic enigma because of added length of a spiral artery compared with that of a straight artery, as well as added complexity of the flow within the vessel because of the coiling curvature.

METHODS

We examined the geometric and hemodynamic characteristics of mathematically defined helical and spiral arteries and compared these with the corresponding characteristics of a straight artery traversing the same depth of tissue, with the aim of gaining some insight into the possible role of spiral geometry in uteroplacental perfusion.

RESULTS

The results indicate that the added length of a spiral artery provides the uteroplacental circulation with a reserve of high resistance to flow. The effect of coiling geometry on the flow within the artery is the development of churning vortices in planes normal (perpendicular) to the main flow direction.

CONCLUSIONS

In the early stages of pregnancy the reserve of high resistance is intact, thus keeping blood supply low. As pregnancy progresses, the reserve is gradually purged by trophoblast invasion and transformation of the distal portion of the spiral artery into an open funnel, thus providing the required high blood supply. The development of churning vortices within the spiral artery support earlier suggestions in the literature that the "spurts" of maternal blood emerging from these arteries may play a role in shaping the anatomy of the villous trees among placental lobules.

Understanding abnormal uterine artery Doppler waveforms: A novel computational model to explore potential causes within the utero-placental vasculature

INTRODUCTION

Uterine artery (UtA) Doppler indices are one of the most commonly employed screening tests for pre-eclampsia worldwide. Abnormal indices appear to result from increased uterine vascular resistance, but anatomical complexity and lack of appropriate animal models mean that little is known about the relative contribution of each of the components of the uterine vasculature to the overall UtA Doppler waveform. Previous computational models suggested that trophoblast-mediated spiral artery remodeling has a dominant effect on the UtA Doppler waveform. However, these models did not incorporate the myometrial arterio-venous anastomoses, which have significant potential to affect utero-placental haemodynamics.

METHODS

We present a more anatomically complete computational model, explicitly incorporating a structural description of each component of the uterine vasculature, and crucially including myometrial arterio-venous anastomoses as parallel pathways for blood-flow away from the placental bed. Wave transmission theory was applied to the network to predict UtA waveforms.

RESULTS

Our model shows that high UtA resistance indices, combined with notching, reflect an abnormal remodeling of the entire uterine vasculature. Incomplete spiral artery remodeling alone is unlikely to cause abnormal UtA Doppler waveforms as increased resistance in these arteries can be 'buffered' by upstream anastomoses. Critically, our results indicate that the radial arteries, may have a more important effect on utero-placental flow dynamics, and the UtA Doppler waveform than previously thought.

CONCLUSIONS

This model suggests that to appropriately interpret UtA Doppler waveforms they must be considered to be reflecting changes in the entire system, rather than just the spiral arteries.

Arterial endothelial cytokines guide extravillous trophoblast invasion towards spiral arteries; an in-vitro study with the trophoblast cell line ACH-3P and female non-uterine endothelial cells

INTRODUCTION

Invasion of extravillous trophoblasts (EVT) is tightly linked to appropriate cell to cell contact as well as paracrine guidance of EVT by maternal uterine cells, conducted by a variety of locally expressed cytokines. Here we investigated the interaction of the first trimester trophoblast cell line ACH-3P with adult iliac arterial (AEC) and venous endothelial cells (VEC).

METHODS

The impact of ACH-3P conditioned medium (Cdm), obtained at 2.5% and 21% oxygen, on endothelial cell viability (LDH-Assay) and network formation (Matrigel-Assay) was tested. We investigated cytokine expression of AEC- and VEC-Cdm and confirmed results with ELISA analysis, and investigated the influence of Cdm on ACH-3P proliferation and invasion. Additionally, direct co-culture experiments with ACH-3P and AEC on Matrigel were performed. A subset of experiments was verified with primary trophoblasts as well as with first trimester placenta in situ specimens.

RESULTS

ACH-3P-Cdm significantly enhanced cell viability of AEC and VEC after 72 h. ACH-3P-Cdm at 2.5% oxygen stabilized endothelial network structures in Matrigel up to 24 h, similar to the effect of a direct co-culture of AEC and ACH-3P. AEC and VEC showed a similar pattern of secreted cytokines. However, elevated levels of cytokines secreted by AEC were found for GRO, IL-6, MMP-1 and uPAR. ELISA confirmed elevated concentrations of IL-6 and uPAR in AEC compared to VEC. ACH-3P and primary trophoblasts more likely invaded towards AEC-Cdm than towards VEC-Cdm. Addition of IL-6 to Cdm increased the invasion potential of both cell types. AEC- and VEC-Cdm reduced ACH-3P cell proliferation after 24 h of culture. IL-6 was highly expressed in uterine AEC compared to VEC as visualized by immunohistochemistry.

DISCUSSION

The presented results clearly demonstrate that cytokines of both cell types, AEC and trophoblasts, differentially contribute to successful guidance and interaction in the process of trophoblast invasion.

Chronic villitis of unknown etiology and massive chronic intervillositis have similar immune cell composition

INTRODUCTION

Chronic villitis of unknown etiology (CVUE) and massive chronic intervillositis (MCI) are placental lesions associated with infiltration of mononuclear cells in the chorionic villi and the intervillous spaces, respectively. It is not well known whether immune cells in CVUE and MCI have similar phenotypic characteristics.

METHODS

A cross-sectional study of third trimester placentas was conducted to identify immune cell subpopulations in CVUE and MCI (n = 17/group). CVUE was diagnosed with H&E staining and antibody to CD3 in serial sections; and MCI, by the presence of massive infiltration of mononuclear cells in the intervillous spaces. Immune cells, ICAM-1 expression and nuclear factor κB (NF-κB) activation were determined immunohistochemically.

RESULTS

CVUE and MCI showed similar infiltrates, mainly CD68+ and CD3+ cells. Most cells (>80%) were CD45RB+, and one third were CD45RO+ in both lesions. There were slightly more CD8+ than CD4+ cells in both CVUE and MCI. More than 90% of cells in CVUE and MCI were ICAM-1+ with NFκB nuclear localization. Syncytiotrophoblast ICAM-1 expression was significantly (p < 0.001) higher in MCI (mean of 81.0; range of 71.6-86.0) than in CVUE (52.4; 36.4-59.4) or normal placentas (0.2; 0.0-0.6). Both, failure of physiologic transformation of spiral arteries and placental atherosclerosis-like lesions of atherosis were significantly more frequent in MCI than in CVUE or normal placentas (p = 0.044 and p = 0.007, respectively).

DISCUSSION

These finding suggest that MCI and CVUE have very similar infiltration of immune cells although MCI has more severe placental lesions.