Adaptive mechanisms controlling uterine spiral artery remodeling during the establishment of pregnancy

Transamniotic Stem Cell Therapy (TRASCET) Modulates Uterine Natural Killer Cell (uNK) Activity in the Hypoxia Model of Intrauterine Growth Restriction (IUGR)

Intrauterine Growth Restriction (IUGR) pathophysiology is driven by abnormal uterine natural killer cell (uNK) activity leading to placental dysfunction. Transamniotic stem cell therapy (TRASCET) with mesenchymal stem cells (MSCs) can improve experimental IUGR by mechanisms not fully understood. We sought to examine TRASCET's effects in downstream products of uNKs in a model of IUGR. Fifteen Sprague-Dawley dams were exposed to alternating hypoxia (10.5% O2) from gestational-day 15 (E15) until term (E21). Their fetuses (n=189) were divided into 4 groups. One group remained untreated (n=52), while three groups received volume-matched intra-amniotic injections of either saline (sham, n=44), or a suspension of amniotic fluid-derived MSCs, either in their native state (TRASCET, n=50) or "primed" to an enhanced anti-inflammatory phenotype (TRASCET-Primed, n=43). Normal fetuses served as controls (n=33). At term, various analyses were performed, including ELISA for surrogates of placental inflammation and uNK activity. Statistical comparisons included Bonferroni-adjusted criterion. Overall survival from hypoxia was 74% (140/189). Placental efficiency was lower in untreated and sham but normalized in both TRASCET groups (p<0.001-0.469). Interleukin-17, a stimulator of uNK cells, was elevated from normal in all groups (p<0.001 for all). Interferon-gamma, released from activated uNK cells, was elevated in all groups except sham, but lower than the untreated in both TRASCET groups (p=<0.001-0.062). Tumor necrosis factor-alpha, also produced by uNKs, was elevated in untreated and sham (p<0.001 for both), but normalized by TRASCET (p=0.054) and even lowered from normal in TRASCET-Primed (p<0.001). Vascular endothelial growth factor, also released by uNKs, was elevated in untreated and sham but lower than normal in both TRASCET groups (p<0.001 for all). We conclude that TRASCET with MSCs modulates the activity of placental uNK cells in experimental IUGR, with distinct effects on their downstream products. This mechanistic insight may inform the development of novel strategies for the management of this disease.

A Microphysiological Model to Mimic the Placental Remodeling during Early Stage of Pregnancy under Hypoxia-Induced Trophoblast Invasion

Placental trophoblast invasion is critical for establishing the maternal-fetal interface, yet the mechanisms driving trophoblast-induced maternal arterial remodeling remain elusive. To address this gap, we developed a three-dimensional microfluidic placenta-on-chip model that mimics early pregnancy placentation in a hypoxic environment. By studying human umbilical vein endothelial cells (HUVECs) under oxygen-deprived conditions upon trophoblast invasion, we observed significant HUVEC artery remodeling, suggesting the critical role of hypoxia in placentation. In particular, we found that trophoblasts secrete matrix metalloproteinase (MMP) proteins under hypoxic conditions, which contribute to arterial remodeling by the degradation of extracellular matrix components. This MMP-mediated remodeling is critical for facilitating trophoblast invasion and proper establishment of the maternal-fetal interface. In addition, our platform allows real-time monitoring of HUVEC vessel contraction during trophoblast interaction, providing valuable insights into the dynamic interplay between trophoblasts and maternal vasculature. Collectively, our findings highlight the importance of MMP-mediated arterial remodeling in placental development and underscore the potential of our platform to study pregnancy-related complications and evaluate therapeutic interventions.

Hypoxia causes trophoblast cell ferroptosis to induce miscarriage through lnc-HZ06/HIF1α-SUMO/NCOA4 axis

Defects of human trophoblast cells may induce miscarriage (abnormal early embryo loss), which is generally regulated by lncRNAs. Ferroptosis is a newly identified iron-dependent programmed cell death. Hypoxia is an important and unavoidable feature in mammalian cells. However, whether hypoxia might induce trophoblast cell ferroptosis and then induce miscarriage, as well as regulated by a lncRNA, was completely unknown. In this work, we discovered at the first time that hypoxia could result in ferroptosis of human trophoblast cells and then induce miscarriage. We also identified a novel lncRNA (lnc-HZ06) that simultaneously regulated hypoxia (indicated by HIF1α protein), ferroptosis, and miscarriage. In mechanism, HIF1α-SUMO, instead of HIF1α itself, primarily acted as a transcription factor to promote the transcription of NCOA4 (ferroptosis indicator) in hypoxic trophoblast cells. Lnc-HZ06 promoted the SUMOylation of HIF1α by suppressing SENP1-mediated deSUMOylation. HIF1α-SUMO also acted as a transcription factor to promote lnc-HZ06 transcription. Thus, both lnc-HZ06 and HIF1α-SUMO formed a positive auto-regulatory feedback loop. This loop was up-regulated in hypoxic trophoblast cells, in RM villous tissues, and in placental tissues of hypoxia-treated mice, which further induced ferroptosis and miscarriage by up-regulating HIF1α-SUMO-mediated NCOA4 transcription. Furthermore, knockdown of either murine lnc-hz06 or Ncoa4 could efficiently suppress ferroptosis and alleviate miscarriage in hypoxic mouse model. Taken together, this study provided new insights in understanding the regulatory roles of lnc-HZ06/HIF1α-SUMO/NCOA4 axis among hypoxia, ferroptosis, and miscarriage, and also offered an effective approach for treatment against miscarriage.

Association between CORIN promoter methylation and hypertensive disorders of pregnancy - A nested case-control study

INTRODUCTION

Corin protein and its coding gene variants have been associated with hypertensive disorders of pregnancy (HDP), but the underlying mechanisms are unclear. As a mediator linking fixed genome with the dynamic environment, DNA methylation at the CORIN gene may link corin with HDP but not has been studied. This study aimed to examine whether CORIN promoter methylation and HDP in Chinese pregnant women.

METHODS

Based on a cohort of Chinese pregnant women, we designed a nested case-control study including 196 cases with HDP and 200 healthy controls. DNA methylation levels in the CORIN promoter were quantified by pyrosequencing using peripheral blood before 20 gestational weeks. The association between DNA methylation in CORIN promoter and HDP was systemically examined by single CpG association analysis, followed by gene-based analysis. Multiple testing was controlled by the false discovery rate (FDR) method.

RESULTS

The single CpG association analysis found that, among the 5 CpG sites assayed, hypermethylation at one CpG site (Chr4:47839945) was significantly associated with HDP (OR = 1.94, raw P = 0.020), but the significance did not survive for multiple testing correction (FDR-P = 0.100). The gene-based association analysis found that DNA methylation of the 5 CpG sites was jointly associated with HDP (raw P = 0.003). In addition to HDP, CORIN promoter methylation was also significantly associated with dynamic blood pressure during pregnancy (raw P < 0.05).

DISCUSSION

Hypermethylation in CORIN promoter at early pregnancy was associated with the risk of HDP during late pregnancy in Chinese women. However, further evidence is required to establish the causality between CORIN promoter methylation and HDP.

Extravillous trophoblast cell lineage development is associated with active remodeling of the chromatin landscape

The extravillous trophoblast cell lineage is a key feature of placentation and successful pregnancy. Knowledge of transcriptional regulation driving extravillous trophoblast cell development is limited. Here, we map the transcriptome and epigenome landscape as well as chromatin interactions of human trophoblast stem cells and their transition into extravillous trophoblast cells. We show that integrating chromatin accessibility, long-range chromatin interactions, transcriptomic, and transcription factor binding motif enrichment enables identification of transcription factors and regulatory mechanisms critical for extravillous trophoblast cell development. We elucidate functional roles for TFAP2C, SNAI1, and EPAS1 in the regulation of extravillous trophoblast cell development. EPAS1 is identified as an upstream regulator of key extravillous trophoblast cell transcription factors, including ASCL2 and SNAI1 and together with its target genes, is linked to pregnancy loss and birth weight. Collectively, we reveal activation of a dynamic regulatory network and provide a framework for understanding extravillous trophoblast cell specification in trophoblast cell lineage development and human placentation.

Placental microRNAs relate to early childhood growth trajectories

BACKGROUND

Poor placental function is a common cause of intrauterine growth restriction, which in turn is associated with increased risks of adverse health outcomes. Our prior work suggests that birthweight and childhood obesity-associated genetic variants functionally impact placental function and that placental microRNA are associated with birthweight. To address the influence of the placenta beyond birth, we assessed the relationship between placental microRNAs and early childhood growth.

METHODS

Using the SITAR package, we generated two parameters that describe individual weight trajectories of children (0-5 years) in the New Hampshire Birth Cohort Study (NHBCS, n = 238). Using negative binomial generalized linear models, we identified placental microRNAs that relate to growth parameters (FDR < 0.1), while accounting for sex, gestational age at birth, and maternal parity.

RESULTS

Genes targeted by the six growth trajectory-associated microRNAs are enriched (FDR < 0.05) in growth factor signaling (TGF/beta: miR-876; EGF/R: miR-155, Let-7c; FGF/R: miR-155; IGF/R: Let-7c, miR-155), calmodulin signaling (miR-216a), and NOTCH signaling (miR-629).

CONCLUSIONS

Growth-trajectory microRNAs target pathways affecting placental proliferation, differentiation and function. Our results suggest a role for microRNAs in regulating placental cellular dynamics and supports the Developmental Origins of Health and Disease hypothesis that fetal environment can have impacts beyond birth.

IMPACT

We found that growth trajectory associated placenta microRNAs target genes involved in signaling pathways central to the formation, maintenance and function of placenta; suggesting that placental cellular dynamics remain critical to infant growth to term and are under the control of microRNAs. Our results contribute to the existing body of research suggesting that the placenta plays a key role in programming health in the offspring. This is the first study to relate molecular patterns in placenta, specifically microRNAs, to early childhood growth trajectory.

Alpha-2-macroglobulin is involved in the occurrence of early-onset pre-eclampsia via its negative impact on uterine spiral artery remodeling and placental angiogenesis

BACKGROUND

Pre-eclampsia (PE) is one of the leading causes of maternal and fetal morbidity/mortality during pregnancy, and alpha-2-macroglobulin (A2M) is associated with inflammatory signaling; however, the pathophysiological mechanism by which A2M is involved in PE development is not yet understood.

METHODS

Human placenta samples, serum, and corresponding clinical data of the participants were collected to study the pathophysiologic mechanism underlying PE. Pregnant Sprague-Dawley rats were intravenously injected with an adenovirus vector carrying A2M via the tail vein on gestational day (GD) 8.5. Human umbilical artery smooth muscle cells (HUASMCs), human umbilical vein endothelial cells (HUVECs), and HTR-8/SVneo cells were transfected with A2M-expressing adenovirus vectors.

RESULTS

In this study, we demonstrated that A2M levels were significantly increased in PE patient serum, uterine spiral arteries, and feto-placental vasculature. The A2M-overexpression rat model closely mimicked the characteristics of PE (i.e., hypertension in mid-to-late gestation, histological and ultrastructural signs of renal damage, proteinuria, and fetal growth restriction). Compared to the normal group, A2M overexpression significantly enhanced uterine artery vascular resistance and impaired uterine spiral artery remodeling in both pregnant women with early-onset PE and in pregnant rats. We found that A2M overexpression was positively associated with HUASMC proliferation and negatively correlated with cell apoptosis. In addition, the results demonstrated that transforming growth factor beta 1 (TGFβ1) signaling regulated the effects of A2M on vascular muscle cell proliferation described above. Meanwhile, A2M overexpression regressed rat placental vascularization and reduced the expression of angiogenesis-related genes. In addition, A2M overexpression reduced HUVEC migration, filopodia number/length, and tube formation. Furthermore, HIF-1α expression was positively related to A2M, and the secretion of sFLT-1 and PIGF of placental origin was closely related to PE during pregnancy or A2M overexpression in rats.

CONCLUSIONS

Our data showed that gestational A2M overexpression can be considered a contributing factor leading to PE, causing detective uterine spiral artery remodeling and aberrant placental vascularization.

Endometrial Microbiota and Immune Tolerance in Pregnancy

Recent studies have demonstrated that the uterus has its own microbiota. However, there is no consensus on endometrial microbiota composition, thus its role in the healthy uterine environment is still a frontier topic. Endometrial receptivity is key to embryo implantation, and in this specific context immunological tolerance against fetal antigens and the tightly regulated expression of inflammatory mediators are fundamental. According to recent evidence, endometrial microbiota may interact in a very dynamic way with the immune system during the peri-conceptional stage and later during pregnancy. For this reason, a condition of dysbiosis might lead to adverse pregnancy outcomes. The aim of this review is to summarize the evidence on the molecular mechanisms by which the endometrial microbiota may interact with the immune system. For this purpose, the link between dysbiosis and reproductive disorders, such as infertility, recurrent pregnancy loss (RPL), and preterm birth, will be discussed. In conclusion, the most recent findings from molecular analyses will be reported to illustrate and possibly overcome the intrinsic limitations of uterine microbiota detection (low endometrial biomass, high risk of contamination during sampling, and lack of standardization).

Transamniotic stem cell therapy (TRASCET) for intrauterine growth restriction (IUGR): A comparison between placental and amniotic fluid donor mesenchymal stem cells

PURPOSE

Transamniotic stem cell therapy (TRASCET) with donor mesenchymal stem cells (MSCs) has been shown experimentally to reverse central effects of intrauterine growth restriction (IUGR). We sought to compare amniotic-fluid and placenta-derived MSCs (afMSCs and pMSCs, respectively) as TRASCET donor cells in a murine IUGR model.

METHODS

Pregnant Sprague-Dawley dams (n=8) were exposed to alternating 12-hour hypoxia (10.5% O₂) cycles, starting on gestational day 15 (E15; term=E21-22). On E17, fetuses (n=100) were divided into four groups. An untreated group had no further manipulations (n=24). Three groups received volume-matched intra-amniotic injections of either saline (sham; n=27), or suspensions of afMSCs (n=24), or pMSCs (n=25). Normal fetuses served as controls (n=21). All infused MSCs consisted of syngeneic Lewis rat cells phenotyped by flow cytometry and GFP-labeled. At term, fetal and placental morphometrics were calculated, and placental TNF-α levels were determined by ELISA. Statistical comparisons were by Fischer's T-test or Wilcoxon rank sum test (p≤0.05).

RESULTS

Overall survival of the hypoxic groups was 83% (83/100). Compared to normal, maternal-adjusted fetal weights were significantly decreased in all hypoxia groups (pairwise p<0.001), however only the afMSC group showed higher adjusted-fetal weights than sham (p<0.001). Placental efficiency was decreased in untreated, sham, and pMSC groups (p<0.001-0.056) but normalized in the afMSC group (p=0.205). Maternal-adjusted placental weights were lower than normal in all hypoxia groups (p<0.001-0.045), except for the pMSC group (p=0.387).

CONCLUSIONS

Amniotic fluid-derived mesenchymal stem cells are superior to their placenta-derived counterparts in transamniotic stem cell therapy for intrauterine growth restriction in a rat model.

LEVEL OF EVIDENCE

Basic/Translational science.

Evidence of Nitric Oxide Impairment During Hypertensive Pregnancies

Hypertensive disorders of pregnancy complicate up to 10% of pregnancies worldwide, and they can be classified into (1) gestational hypertension, (2) preeclampsia, (3) chronic hypertension and (4) chronic hypertension with preeclampsia. Nitric oxide (NO) plays an essential role in the haemodynamic adaptations observed during pregnancy. It has been shown that the nitric oxide pathway's dysfunction during pregnancy is associated with placental- and vascular-related diseases such as hypertensive disorders of pregnancy. This review aims to present a brief definition of hypertensive disorders of pregnancy and physiological maternal cardiovascular adaptations during pregnancy. We also detail how NO signalling is altered in the (a) systemic vasculature, (b) uterine artery/spiral arteries, (c) implantation and (d) placenta of hypertensive disorders during pregnancy. We conclude by summarizing the anti-hypertensive therapy of hypertensive disorders of pregnancy as a specific management strategy.

MicroRNAs: key regulators of the trophoblast function in pregnancy disorders

The placenta is essential for a successful pregnancy and healthy intrauterine development in mammals. During human pregnancy, the growth and development of the placenta are inseparable from the rapid proliferation, invasion, and migration of trophoblast cells. Previous reports have shown that the occurrence of many pregnancy disorders may be closely related to the dysfunction of trophoblasts. However, the function regulation of human trophoblast cells in the placenta is poorly understood. Therefore, studying the factors that regulate the function of trophoblast cells is necessary. MicroRNAs (miRNAs) are small, non-coding, single-stranded RNA molecules. Increasing evidence suggests that miRNAs play a crucial role in regulating trophoblast functions. This review outlines the role of miRNAs in regulating the function of trophoblast cells and several common signaling pathways related to miRNA regulation in pregnancy disorders.

“Iron triangle” of regulating the uterine microecology: Endometrial microbiota, immunity and endometrium

The uterus is the core place for breeding new life. The balance and imbalance of uterine microecology can directly affect or even dominate the female reproductive health. Emerging data demonstrate that endometrial microbiota, endometrium and immunity play an irreplaceable role in regulating uterine microecology, forming a dynamic iron triangle relationship. Up to nowadays, it remains unclear how the three factors affect and interact with each other, which is also a frontier topic in the emerging field of reproductive tract microecology. From this new perspective, we aim to clarify the relationship and mechanism of the interaction of these three factors, especially their pairwise interactions. Finally, the limitations and future perspectives of the current studies are summarized. In general, these three factors have a dynamic relationship of mutual dependence, promotion and restriction under the physiological or pathological conditions of uterus, among which the regulatory mechanism of microbiota and immunity plays a role of bridge. These findings can provide new insights and measures for the regulation of uterine microecology, the prevention and treatment of endometrial diseases, and the further multi-disciplinary integration between microbiology, immunology and reproductive medicine.

METTL3-Mediated m6A RNA Methylation of ZBTB4 Interferes With Trophoblast Invasion and Maybe Involved in RSA

N⁶-methyladenosine (m⁶A) was the most abundant modification of mRNA and lncRNA in mammalian cells and played an important role in many biological processes. However, whether m⁶A modification was associated with recurrent spontaneous abortion (RSA) and its roles were still unclear.

Methods: Methylated RNA immunoprecipitation sequencing (MeRIP-Seq) was used to study the global m⁶A modification pattern in RSAs and controls. RNA sequencing (RNA-Seq) was used to study the level of global mRNA in two groups. Real-time quantitative PCR (RT-qPCR) was used to verify the level of mRNA of METTL3 and ZBTB4. MeRIP–qPCR was conducted to test the level of ZBTB4 m⁶A modification in two groups. In order to further explore whether ZBTB4 was the substrate of METTL3, the HTR-8/SVneo (HTR-8) cell line was selected for the knockdown and overexpression of METTL3. To study whether METTL3 regulated the ZBTB4 expression by recognizing ZBTB4 mRNA m⁶A motifs in coding sequences (CDS), dual-luciferase reporter assay was conducted. RNA stability assays using actinomycin D were conducted to study the RNA stability of the HTR-8 cell line with METTL3 overexpression and knockdown. To illustrate the role of METTL3 in the invasion of trophoblast, matrigel invasion assays and transwell migration assays were conducted using the HTR-8 cell line with METTL3 overexpression and knockdown.

Results: A total of 65 genes were found with significant differences both in m⁶A modification and mRNA expression. We found m⁶A methyltransferase METTL3 was significantly down-regulated in the RSA group. Through gene function analysis, RT-qPCR, MeRIP–qPCR validation experiment, knockdown, and overexpression of METTL3 in the HTR-8 cell line, ZBTB4 was selected as one target of METTL3. Furthermore, we clarified that METTL3 regulated the expression of ZBTB4 by recognizing ZBTB4 mRNA m⁶A motifs in the CDS using the dual-luciferase reporter assay and METTL3 regulated the invasion of trophoblast by altering the stability and expression of ZBTB4 by RNA stability, matrigel invasion, and transwell migration assays.

Conclusion: Our study revealed the mechanism by which METTL3 regulated the stability and expression of ZBTB4 and the trophoblast migration ability of RSA. A new perspective was provided for exploring the mechanism of embryonic development in RSA patients.

Intrauterine Growth Restriction (IUGR) as a potential target for transamniotic stem cell therapy

BACKGROUND

We sought to determine whether intrauterine growth restriction (IUGR) could be a target for mesenchymal stem cell (MSC)-based transamniotic stem cell therapy (TRASCET).

METHODS

Pregnant dams subjected to hypoxia (10.5% O₂) cycles had their fetuses divided into four groups: untreated (n = 24) and three groups receiving volume-matched intra-amniotic injections of either saline (sham; n = 16), or suspensions of luciferase-labeled, syngeneic amniotic fluid-derived MSCs that were either native (TRASCET-unprimed; n = 29), or primed by exposure to IFNγ and IL-1β (TRASCET-primed; n = 31). Normal fetuses served as additional controls (n = 22). Multiple analyses were performed at term.

RESULTS

Compared to normal, fetal weights were significantly decreased in all hypoxia groups (p = 0.002 to <0.001), except for TRASCET-primed. Placental efficiency (fetal/placental weight) was significantly decreased in all hypoxia groups (p = 0.002 to <0.001), but normalized in both TRASCET groups. A significant increase in metrial expression of IFNγ in both the untreated and sham groups (p = 0.04 to 0.02) was reversed only in the TRASCET-primed group. Luciferase DNA was present in both TRASCET groups' placentas.

CONCLUSIONS

Transamniotic stem cell therapy with primed mesenchymal stem cells reverses some of the effects of intrauterine growth restriction in a rat model. Further study into this novel approach for the treatment of this disease is warranted.

LEVEL OF EVIDENCE

N/A (Animal and Laboratory Study).

VE-cadherin enables trophoblast endovascular invasion and spiral artery remodeling during placental development

During formation of the mammalian placenta, trophoblasts invade the maternal decidua and remodel spiral arteries to bring maternal blood into the placenta. This process, known as endovascular invasion, is thought to involve the adoption of functional characteristics of vascular endothelial cells (ECs) by trophoblasts. The genetic and molecular basis of endovascular invasion remains poorly defined, however, and whether trophoblasts utilize specialized endothelial proteins in an analogous manner to create vascular channels remains untested. Vascular endothelial (VE-)cadherin is a homotypic adhesion protein that is expressed selectively by ECs in which it enables formation of tight vessels and regulation of EC junctions. VE-cadherin is also expressed in invasive trophoblasts and is a prime candidate for a molecular mechanism of endovascular invasion by those cells. Here, we show that VE-cadherin is required for trophoblast migration and endovascular invasion into the maternal decidua in the mouse. VE-cadherin deficiency results in loss of spiral artery remodeling that leads to decreased flow of maternal blood into the placenta, fetal growth restriction, and death. These studies identify a non-endothelial role for VE-cadherin in trophoblasts during placental development and suggest that endothelial proteins may play functionally unique roles in trophoblasts that do not simply mimic those in ECs.

Intravenous immunoglobulins improve live birth rate among women with underlying immune conditions and recurrent pregnancy loss: a systematic review and meta-analysis

Intravenous immunoglobulin (IVIG) is increasingly used as a treatment for recurrent pregnancy loss (RPL) despite lack of clear evidence on efficacy. Recent data suggest IVIG might be more effective in a subgroup of women with an aberrant immunological profile. Therefore, a systematic review and meta-analysis of studies on the effectiveness of IVIG treatment on pregnancy outcome among women with RPL and underlying immunological conditions (e.g., elevated NK cell percentage, elevated Th1/Th2 ratio, diagnosis with autoimmune disorders) was conducted. Eight non-randomized controlled trials, including 478 women (intervention: 284; control: 194), met eligibility criteria. Meta-analysis showed that treatment with IVIG was associated with a two-fold increase in live birth rate (RR 1.98, 95% CI 1.44–2.73, P < 0.0001). The effect of IVIG was particularly marked in the subgroup of studies including patients based on presence of elevated (> 12%) NK-cell percentage (RR 2.32, 95% CI 1.77–3.02, P < 0.0001) and when starting intervention prior to or during cycle of conception (RR 4.47, 95% CI 1.53–13.05, P = 0.006). In conclusion, treatment with IVIG may improve live birth rate in women with RPL and underlying immune conditions. However, these results should be interpreted with caution as studies are limited by low number of participants and the non-randomized design, which represent seriously biases. Future randomized controlled trials in women with RPL and underlying immune conditions are needed before using IVIG in a clinical setting.

Modeling Trophoblast Cell-Guided Uterine Spiral Artery Transformation in the Rat

The rat possesses hemochorial placentation with deep intrauterine trophoblast cell invasion and trophoblast-guided uterine spiral artery remodeling, which resembles human placentation. Uterine spiral arteries are extensively remodeled to deliver sufficient supply of maternal blood and nutrients to the developing fetus. Inadequacies in these key processes negatively impact fetal growth and development. Recent innovations in genome editing combined with effective phenotyping strategies have provided new insights into placental development. Application of these research approaches has highlighted both conserved and species-specific features of hemochorial placentation. The review provides foundational information on rat hemochorial placental development and function during physiological and pathological states, especially as related to the invasive trophoblast cell-guided transformation of uterine spiral arteries. Our goal is to showcase the utility of the rat as a model for in vivo mechanistic investigations targeting regulatory events within the uterine-placental interface.

Longitudinal assessment of spiral artery and intravillous arteriole blood flow and adverse pregnancy outcome

OBJECTIVE

Superb microvascular imaging (SMI) has been shown to improve visualization of small vessels by suppressing global motions while preserving low-flow components, such as the microvessels in the placenta. We sought to determine if SMI-aided visualization of flow velocity waveforms in the spiral arteries (SA) and intravillous fetal arterioles (IVA) could predict fetal growth restriction (FGR), gestational hypertension (GH) and/or pre-eclampsia (PE).

METHODS

This was a prospective longitudinal study of singleton pregnancies without fetal anomaly, receiving prenatal care in one of two medical centers over a 5-year period. Using SMI-aided color Doppler, SA and IVA flow velocity was measured at three timepoints: 11 + 0 to 14 + 0, 18 + 0 to 22 + 6 and 28 + 0 to 34 + 6 weeks of gestation. SA and IVA flow velocity waveforms were reported as resistance indices (RI). RI values were analyzed using multilevel modeling; individual regression curves were estimated and combined to obtain the reference intervals for SA-RI and IVA-RI in uncomplicated pregnancies. The primary clinical outcome was FGR and secondary outcomes were PE and GH. FGR was defined as estimated fetal weight < 10^th percentile. Student's t-test was used to compare deviation from expected RI between normal and complicated pregnancies.

RESULTS

Among 540 pregnancies included in the analysis, 18 (3.3%) had FGR, 31 (5.7%) PE and 61 (11.3%) GH. In uncomplicated pregnancies, the SA-RI decreased progressively with advancing gestation, whereas the IVA-RI increased with gestational age. In the third trimester, the mean SA-RI and IVA-RI values were significantly higher in the FGR group compared with pregnancies that did not develop FGR, while the mean SA-RI was significantly higher in PE compared with non-PE pregnancies. There was no significant difference in mean SA-RI or IVA-RI between pregnancies with vs those without GH at any gestational age. When all three adverse outcomes were combined, SA-RI was significantly higher in pregnancies with these outcomes when compared to uncomplicated pregnancies in the third trimester (mean ± SD, 0.29 ± 0.12 vs 0.26 ± 0.12; P = 0.02). In screening for FGR using SA-RI, the areas under the receiver-operating-characteristics curves (AUC) were 0.68, 0.73 and 0.73 in the first, second and third trimesters, respectively. The respective AUCs for IVA-RI were 0.72, 0.72 and 0.73 for each trimester.

CONCLUSIONS

SA-RI and IVA-RI, measured using SMI technology, were significantly higher in pregnancies at risk for FGR in late gestation. Larger studies are needed to determine if SA and IVA flow are reliable predictors of adverse pregnancy outcome. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Kisspeptin treatment improves fetal-placental development and blocks placental oxidative damage caused by maternal hypothyroidism in an experimental rat model

Maternal hypothyroidism is associated with fetal growth restriction, placental dysfunction, and reduced kisspeptin/Kiss1R at the maternal-fetal interface. Kisspeptin affects trophoblastic migration and has antioxidant and immunomodulatory activities. This study aimed to evaluate the therapeutic potential of kisspeptin in the fetal-placental dysfunction of hypothyroid Wistar rats. Hypothyroidism was induced by daily administration of propylthiouracil. Kisspeptin-10 (Kp-10) treatment was performed every other day or daily beginning on day 8 of gestation. Feto-placental development, placental histomorphometry, and expression levels of growth factors (VEGF, PLGF, IGF1, IGF2, and GLUT1), hormonal (Dio2) and inflammatory mediators (TNFα, IL10, and IL6), markers of hypoxia (HIF1α) and oxidative damage (8-OHdG), antioxidant enzymes (SOD1, Cat, and GPx1), and endoplasmic reticulum stress mediators (ATF4, GRP78, and CHOP) were evaluated on day 18 of gestation. Daily treatment with Kp-10 increased free T3 and T4 levels and improved fetal weight. Both treatments reestablished the glycogen cell population in the junctional zone. Daily treatment with Kp-10 increased the gene expression levels of Plgf, Igf1, and Glut1 in the placenta of hypothyroid animals, in addition to blocking the increase in 8-OHdG and increasing protein and/or mRNA expression levels of SOD1, Cat, and GPx1. Daily treatment with Kp-10 did not alter the higher protein expression levels of VEGF, HIF1α, IL10, GRP78, and CHOP caused by hypothyroidism in the junctional zone compared to control, nor the lower expression of Dio2 caused by hypothyroidism. However, in the labyrinth zone, this treatment restored the expression of VEGF and IL10 and reduced the GRP78 and CHOP immunostaining. These findings demonstrate that daily treatment with Kp-10 improves fetal development and placental morphology in hypothyroid rats, blocks placental oxidative damage, and increases the expression of growth factors and antioxidant enzymes in the placenta.

Intersection of regulatory pathways controlling hemostasis and hemochorial placentation

Hemochorial placentation is characterized by the development of trophoblast cells specialized to interact with the uterine vascular bed. We utilized trophoblast stem (TS) cell and mutant rat models to investigate regulatory mechanisms controlling trophoblast cell development. TS cell differentiation was characterized by acquisition of transcript signatures indicative of an endothelial cell-like phenotype, which was highlighted by the expression of anticoagulation factors including tissue factor pathway inhibitor (TFPI). TFPI localized to invasive endovascular trophoblast cells of the rat placentation site. Disruption of TFPI in rat TS cells interfered with development of the endothelial cell-like endovascular trophoblast cell phenotype. Similarly, TFPI was expressed in human invasive/extravillous trophoblast (EVT) cells situated within first-trimester human placental tissues and following differentiation of human TS cells. TFPI was required for human TS cell differentiation to EVT cells. We next investigated the physiological relevance of TFPI at the placentation site. Genome-edited global TFPI loss-of-function rat models revealed critical roles for TFPI in embryonic development, resulting in homogeneous midgestation lethality prohibiting analysis of the role of TFPI as a regulator of the late-gestation wave of intrauterine trophoblast cell invasion. In vivo trophoblast-specific TFPI knockdown was compatible with pregnancy but had profound effects at the uterine-placental interface, including restriction of the depth of intrauterine trophoblast cell invasion while leading to the accumulation of natural killer cells and increased fibrin deposition. Collectively, the experimentation implicates TFPI as a conserved regulator of invasive/EVT cell development, uterine spiral artery remodeling, and hemostasis at the maternal-fetal interface.

Physiological characterization of an arginine vasopressin rat model of preeclampsia

Rodent models have contributed greatly to our understanding of preeclampsia (PE) progression in humans, however to-date no model has been able to effectively replicate the clinical presentation of the disease. This study aimed to provide a thorough physiological characterization of the arginine vasopressin (AVP)-induced rat model of PE to determine its applicability in studying the pathophysiology of PE. Female Sprague Dawley rats (n = 24) were separated into four groups (n = 6 per group) viz., pregnant AVP, pregnant saline, non-pregnant AVP, and non-pregnant saline. All animals received a continuous dose of either AVP (150 ng/h) or saline via subcutaneous mini osmotic pumps for 18 days. Full physiological characterization of the model included measuring systolic and diastolic blood pressure, and collecting urine and blood samples for biochemical analysis. AVP infusion significantly increased blood pressure and urinary protein levels in the pregnant rats (p < 0.05). Biochemical markers measured, differed significantly in the AVP-treated vs the pregnant saline groups (p < 0.05). Placental and individual pup weight decreased significantly in the pregnant AVP vs pregnant saline group (p < 0.05). The physiological and hematological data confirm the usefulness of this rat model in the study of PE, since AVP-induced vasoconstriction increases peripheral resistance and successfully mimics the pathological changes associated with PE development in humans.Abbreviations: PE: preeclampsia; AVP: arginine vasopressin; ISSHP: International Society for the Study of Hypertension in Pregnancy; ACOG: American College of Obstetricians and Gynecologists; RUPP: reduced uterine perfusion pressure; sFlt-1: soluble fms-like tyrosine kinase; VEGF: vascular endothelial growth factor; PlGF: placental growth factor; AVP: arginine vasopressin; PAVP: pregnant AVP-treated; PS: pregnant saline; GD: gestational day; ALT: alanine transaminase; NAVP: non-pregnant AVP-treated; NS: non-pregnant saline; AST: aspartate aminotransferase; HDL: high-density lipoprotein; RBC: red blood cell; RAAS: renin-angiotensin aldosterone system; HELLP: hemolysis, elevated liver enzymes, low platelet.

Evaluation of Placentation and the Role of the Aryl Hydrocarbon Receptor Pathway in a Rat Model of Dioxin Exposure

BACKGROUND

Our environment is replete with chemicals that can affect embryonic and extraembryonic development. Dioxins, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are compounds affecting development through the aryl hydrocarbon receptor (AHR).

OBJECTIVES

The purpose of this investigation was to examine the effects of TCDD exposure on pregnancy and placentation and to evaluate roles for AHR and cytochrome P450 1A1 (CYP1A1) in TCDD action.

METHODS

Actions of TCDD were examined in wild-type and genome-edited rat models. Placenta phenotyping was assessed using morphological, biochemical, and molecular analyses.

RESULTS

TCDD exposures were shown to result in placental adaptations and at higher doses, pregnancy termination. Deep intrauterine endovascular trophoblast cell invasion was a prominent placentation site adaptation to TCDD. TCDD-mediated placental adaptations were dependent upon maternal AHR signaling but not upon placental or fetal AHR signaling nor the presence of a prominent AHR target, CYP1A1. At the placentation site, TCDD activated AHR signaling within endothelial cells but not trophoblast cells. Immune and trophoblast cell behaviors at the uterine-placental interface were guided by the actions of TCDD on endothelial cells.

DISCUSSION

We identified an AHR regulatory pathway in rats activated by dioxin affecting uterine and trophoblast cell dynamics and the formation of the hemochorial placenta. https://doi.org/10.1289/EHP9256.

miRNAs in decidual NK cells: regulators worthy of attention during pregnancy

The critical immune effectors, including T, B, and natural killer (NK) cells, dendritic cells, and macrophages participate in regulating immune responses during pregnancy. Among these immune cells, decidual NK (dNK) cells are involved in key placental development processes at the maternal-fetal interface, such as uterine spiral artery remodeling, trophoblast invasion, and decidualization. Mechanistically, dNK cells significantly influence pregnancy outcome by secreting cytokines, chemokines, and angiogenic mediators and by their interactions with trophoblasts and other decidual cells. MicroRNAs (miRNAs) are small non-coding RNA molecules that participate in the initiation and progression of human diseases. Although the functions of circulating miRNAs in pathological mechanism has been extensively studied, the regulatory roles of miRNAs in NK cells, especially in dNK cells, have been rarely reported. In this review, we analyze the effects of miRNA regulations of dNK cell functions on the immune system during gestation. We discuss aberrant expressions of certain miRNAs in dNK cells that may lead to pathological consequences, such as recurrent pregnancy loss (RPL). Interestingly, miRNA expression patterns are also different between dNK cells and peripheral NK (pNK) cells, and pNK cells in the first- and third-trimester of gestation. The dysregulation of miRNA plays a pivotal regulatory role in driving immune functions of dNK and pNK cells. Further understanding of the molecular mechanisms of miRNAs in dNK cells may provide new insights into the development of therapeutics to prevent pregnancy failure.

Uterine Vascular Control Preconception and During Pregnancy

Successful pregnancy and reproduction are dependent on adequate uterine blood flow, placental perfusion, and vascular responsivity to fetal demands. The ability to support pregnancy centers on systemic adaptation and endometrial preparation through decidualization, embryonic implantation, trophoblast invasion, arterial/arteriolar reactivity, and vascular remodeling. These adaptations occur through responsiveness to endocrine signaling and local uteroplacental mediators. The purpose of this article is to highlight the current knowledge associated with vascular remodeling and responsivity during uterine preparation for and during pregnancy. We focus on maternal cardiovascular systemic and uterine modifications, endometrial decidualization, implantation and invasion, uterine and spiral artery remodeling, local uterine regulatory mechanisms, placentation, and pathological consequences of vascular dysfunction during pregnancy. © 2021 American Physiological Society. Compr Physiol 11:1-23, 2021.

No evidence of the unfolded protein response in the placenta of two rodent models of preeclampsia and intrauterine growth restriction

In humans, intrauterine growth restriction (IUGR) and preeclampsia (PE) are associated with induction of the unfolded protein response (UPR) and increased placental endoplasmic reticulum (ER) stress. Especially in PE, oxidative stress occurs relative to the severity of maternal vascular underperfusion (MVU) of the placental bed. On the premise that understanding the mechanisms of placental dysfunction could lead to targeted therapeutic options for human IUGR and PE, we investigated the roles of the placental UPR and oxidative stress in two rodent models of these human gestational pathologies. We employed a rat IUGR model of gestational maternal protein restriction, as well as an endothelial nitric oxide synthase knockout mouse model (eNOS-/-) of PE/IUGR. Placental expression of UPR members was analyzed via qRT-PCR (Grp78, Calnexin, Perk, Chop, Atf6, and Ern1), immunohistochemistry, and Western blotting (Calnexin, ATF6, GRP78, CHOP, phospho-eIF2α, and phospho-IRE1). Oxidative stress was determined via Western blotting (3-nitrotyrosine and 4-hydroxy-2-nonenal). Both animal models showed a significant reduction of fetal and placental weight. These effects did not induce placental UPR. In contrast to human data, results from our rodent models suggest retention of placental plasticity in the setting of ER stress under an adverse gestational environment. Oxidative stress was significantly increased only in female IUGR rat placentas, suggesting a sexually dimorphic response to maternal malnutrition. Our study advances understanding of the involvement of the placental UPR in IUGR and PE. Moreover, it emphasizes the appropriate choice of animal models researching various aspects of these pregnancy complications.

Pregnancy-Related Extracellular Vesicles Revisited

Extracellular vesicles (EVs) are small vesicles ranging from 20–200 nm to 10 μm in diameter that are discharged and taken in by many different types of cells. Depending on the nature and quantity of their content—which generally includes proteins, lipids as well as microRNAs (miRNAs), messenger-RNA (mRNA), and DNA—these particles can bring about functional modifications in the receiving cells. During pregnancy, placenta and/or fetal-derived EVs have recently been isolated, eliciting interest in discovering their clinical significance. To date, various studies have associated variations in the circulating levels of maternal and fetal EVs and their contents, with complications including gestational diabetes and preeclampsia, ultimately leading to adverse pregnancy outcomes. Furthermore, EVs have also been identified as messengers and important players in viral infections during pregnancy, as well as in various congenital malformations. Their presence can be detected in the maternal blood from the first trimester and their level increases towards term, thus acting as liquid biopsies that give invaluable insight into the status of the feto-placental unit. However, their exact roles in the metabolic and vascular adaptations associated with physiological and pathological pregnancy is still under investigation. Analyzing peer-reviewed journal articles available in online databases, the purpose of this review is to synthesize current knowledge regarding the utility of quantification of pregnancy related EVs in general and placental EVs in particular as non-invasive evidence of placental dysfunction and adverse pregnancy outcomes, and to develop the current understanding of these particles and their applicability in clinical practice.

Single-Cell RNA-seq Identifies Cell Subsets in Human Placenta That Highly Expresses Factors Driving Pathogenesis of SARS-CoV-2

Infection by the Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) results in the novel coronavirus disease COVID-19, which has posed a serious threat globally. Infection of SARS-CoV-2 during pregnancy is associated with complications such as preterm labor and premature rupture of membranes, and a proportion of neonates born to infected mothers are also positive for the virus. During pregnancy, the placental barrier protects the fetus from pathogens and ensures healthy development. To predict if the placenta is permissive to SARS-CoV-2, we utilized publicly available single-cell RNA-seq data to identify if the placental cells express the necessary factors required for infection. SARS-CoV-2 binding receptor ACE2 and the S protein priming protease TMPRSS2 are co-expressed by a subset of syncytiotrophoblasts (STB) in the first trimester and extravillous trophoblasts (EVT) in the second trimester human placenta. In addition, the non-canonical receptor BSG/CD147 and other proteases (CTSL, CTSB, and FURIN) are detected in most of the placental cells. Other coronavirus family receptors (ANPEP and DPP4) were also expressed in the first and second trimester placental cells. Additionally, the term placenta of multiple species including humans expressed ACE2, DPP4, and ANPEP along with the viral S protein proteases. The ACE2- and TMPRSS2-positive (ACE2 + TMPRSS2 +) placental subsets expressed mRNA for proteins involved in viral budding and replication. These cells also had the mRNA for proteins that physically interact with SARS-CoV-2 in host cells. Further, we discovered unique signatures of genes in ACE2 + TMPRSS2 + STBs and EVTs. The ACE2 + TMPRSS2 + STBs are highly differentiated cells and express genes involving mitochondrial metabolism and glucose transport. The second trimester ACE2 + TMPRSS2 + EVTs are enriched for markers of endovascular trophoblasts. Both these subtypes abundantly expressed genes in the Toll-like receptor pathway. The second trimester EVTs are also enriched for components of the JAK-STAT pathway that drives inflammation. We carried out a systematic review and identified that in 12% of pregnant women with COVID-19, the placenta was infected with SARS-CoV-2, and the virus was detected in STBs. To conclude, herein we have uncovered the cellular targets for SARS-CoV-2 entry and have shown that these cells can potentially drive viremia in the developing human placenta. Our results provide a basic framework toward understanding the paraphernalia involved in SARS-CoV-2 infections in pregnancy.

The unique applicability of the human placenta to the Adverse Outcome Pathway (AOP) concept: the placenta provides fundamental insights into human organ functions at multiple levels of biological organization

Despite the short lifespan of the human placenta, the proper formation and function of the organ is of crucial importance for fetal development. Placental dysfunction increases the risk of complications for mother and child during pregnancy and childbirth and beyond as it predisposes to fetal programming. The placenta is an upstream organ of the fetus. It performs the functions of fetal lungs, liver, intestines, kidneys and glands as long as these organs are not fully functional. Furthermore, it is the only human organ that is non-invasively available either after elective abortion or after birth. This is a crucial point given that the conceptual framework of Adverse Outcome Pathway (AOP) requires data on organ function. In vitro and ex vivo placental studies, combined with epidemiological and clinical data on pregnant women, newborns, and infants can uniquely cover all levels of information needed to develop new AOPs and complement existing AOPs related to reproductive toxicity and beyond. To stimulate further research in this area and to support researchers in future studies dealing with the development of AOPs related to the placenta, this review first gives a brief description of placental structure, placental development and relevant pregnancy diseases. The state of knowledge about the available placental models, their particularities and limitations are briefly discussed. Finally, the use of placental research for the development of AOPs is presented with an illustrative example.

Lymphatic mimicry in maternal endothelial cells promotes placental spiral artery remodeling

Molecular heterogeneity of endothelial cells underlies their highly specialized functions during changing physiological conditions within diverse vascular beds. For example, placental spiral arteries (SAs) undergo remarkable remodeling to meet the ever-growing demands of the fetus - a process which is deficient in preeclampsia. The extent to which maternal endothelial cells coordinate with immune cells and pregnancy hormones to promote SA remodeling remains largely unknown. Here we found that remodeled SAs expressed the lymphatic markers PROX1, LYVE1, and VEGFR3, mimicking lymphatic identity. Uterine natural killer (uNK) cells, which are required for SA remodeling and secrete VEGFC, were both sufficient and necessary for VEGFR3 activation in vitro and in mice lacking uNK cells, respectively. Using Flt4Chy/+ mice with kinase inactive VEGFR3 and Vegfcfl/fl Vav1-Cre mice, we demonstrated that SA remodeling required VEGFR3 signaling, and that disrupted maternal VEGFR3 signaling contributed to late-gestation fetal growth restriction. Collectively, we identified a novel instance of lymphatic mimicry by which maternal endothelial cells promote SA remodeling, furthering our understanding of the vascular heterogeneity employed for the mitigation of pregnancy complications such as fetal growth restriction and preeclampsia.

Poorly controlled diabetes mellitus alters placental structure, efficiency, and plasticity

INTRODUCTION

The hemochorial placenta provides a critical barrier at the maternal-fetal interface to modulate maternal immune tolerance and enable gas and nutrient exchange between mother and conceptus. Pregnancy outcomes are adversely affected by diabetes mellitus; however, the effects of poorly controlled diabetes on placental formation, and subsequently fetal development, are not fully understood.

RESEARCH DESIGN AND METHODS

Streptozotocin was used to induce hyperglycemia in pregnant rats for the purpose of investigating the impact of poorly controlled diabetes on placental formation and fetal development. The experimental paradigm of hypoxia exposure in the pregnant rat was also used to assess properties of placental plasticity. Euglycemic and hyperglycemic rats were exposed to ambient conditions (~21% oxygen) or hypoxia (10.5% oxygen) beginning on gestation day (gd) 6.5 and sacrificed on gd 13.5. To determine whether the interaction of hyperglycemia and hypoxia was directly altering trophoblast lineage development, rat trophoblast stem (TS) cells were cultured in high glucose (25 mM) and/or exposed to low oxygen (0.5% to 1.5%).

RESULTS

Diabetes caused placentomegaly and placental malformation, decreasing placental efficiency and fetal size. Elevated glucose disrupted rat TS cell differentiation in vitro. Evidence of altered trophoblast differentiation was also observed in vivo, as hyperglycemia affected the junctional zone transcriptome and interfered with intrauterine trophoblast invasion and uterine spiral artery remodeling. When exposed to hypoxia, hyperglycemic rats showed decreased proliferation and ectoplacental cone development on gd 9.5 and complete pregnancy loss by gd 13.5. Furthermore, elevated glucose concentrations inhibited TS cell responses to hypoxia in vitro.

CONCLUSIONS

Overall, these results indicate that alterations in placental development, efficiency, and plasticity could contribute to the suboptimal fetal outcomes in offspring from pregnancies complicated by poorly controlled diabetes.

Interleukin-17 signaling mediates cytolytic natural killer cell activation in response to placental ischemia

T-helper (T_H)17s, IL-17, and cytolytic natural killer cells (cNKs) are increased in preeclampsia and contribute to the hypertension, inflammation, and fetal growth restriction that occurs in response to placental ischemia in the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. As IL-17 stimulates NK cytotoxicity in vitro, we tested the hypothesis that IL-17 inhibition in RUPP rats would decrease cNK activation as a mechanism to improve maternal and fetal outcomes. On gestation day (GD) 14, rats undergoing RUPP received a miniosmotic pump infusing IL-17RC (100 pg/day), a soluble IL-17 receptor (RUPP + IL-17RC). On GD19, mean arterial pressure (MAP) was measured in normal pregnant (NP), RUPP, and RUPP + IL-17RC rats (n = 10-12/group), animals were euthanized, and blood and tissues were collected for analysis. MAP was 30% higher in RUPP compared with NP (P < 0.0001) and was 12% lower in RUPP + IL-17RC (P = 0.0007 vs. RUPP). Placental cytolytic NK cells were 132% higher in RUPP than in NP (P = 0.04 vs. NP) and were normalized in RUPP + IL-17RC (P = 0.03 vs. RUPP). Placental levels of TNF-α, a cNK-secreted cytokine, and macrophage inflammatory protein-3α (MIP-3α), a cNK chemokine, were higher in RUPP vs. NP and lower after IL-17 blockade. Placental VEGF was lower in RUPP vs. NP and was normalized in RUPP + IL-17RC. In vitro cytolytic activity of RUPP placental NKs was higher compared with NP and was blunted in RUPP + IL-17RC NKs. Finally, both fetal weight and placental weight were lower in RUPP compared with NP, and were improved in RUPP + IL-17RC. These data identify IL-17 as a mediator of cNK activation in response to placental ischemia during pregnancy.

The role of hepatic sinusoidal obstruction in the pathogenesis of the hepatic involvement in HELLP syndrome: Exploring the literature

AIM

This study aims to determine, based on existing data, whether the mechanism resulting in liver dysfunction in HELLP syndrome resembles that in Sinusoidal Obstruction Syndrome (SOS).

BACKGROUND

HELLP syndrome is a serious pregnancy disorder with high maternal and perinatal morbidity and mortality rates. Because of poor insight in its pathophysiology, particularly that of the liver involvement, clinical management is limited to symptomatic treatment, often followed by termination of pregnancy. SOS is a rare, potentially life-threatening complication of radio and/ or chemotherapy in the preparation of hematopoietic cell transplantation. The etiology of liver dysfunction in SOS is - unlike that in HELLP syndrome - better-understood and seems to be initiated by direct toxic damage and demise of endothelial cells, causing hepatic sinusoidal obstruction and ischemia.

METHODS

We searched Pubmed, Embase and Cochrane for reports on the etiology of HELLP and SOS. This yielded 73 articles, with 14 additional reports from the references listed in these articles.

RESULTS

The dysfunctional placenta in women developing HELLP initiates a cascade of events that eventually results in liver dysfunction. The placenta releases, besides anti-angiogenetic factors, also necrotic debris and cell-free DNA, a mixture that not only induces systemic endothelial dysfunction as in preeclampsia, but also a systemic inflammatory response. The latter aggravates the endothelio-toxic effects in the systemic cardiovascular bed, amplifying the already increased pro-thrombotic conditions. Particularly in microcirculations with extremely low shear forces, such as in the hepatic sinusoids, this will facilitate microthrombi formation and fibrin deposition eventually resulting in obstruction of the sinusoids similar as in SOS. The latter causes ischemic damage and progressive demise of hepatocytes.

CONCLUSION

The available information supports the concept that the liver damage in HELLP and SOS results from sinusoidal ischemia, presumably resulting from partially overlapping pathophysiological mechanisms.

Hemochorial placentation: development, function, and adaptations

Placentation is a reproductive adaptation that permits fetal growth and development within the protected confines of the female reproductive tract. Through this important role, the placenta also determines postnatal health and susceptibility to disease. The hemochorial placenta is a prominent feature in primate and rodent development. This manuscript provides an overview of the basics of hemochorial placental development and function, provides perspectives on major discoveries that have shaped placental research, and thoughts on strategies for future investigation.

Hypoxia and Placental Development

Hemochorial placentation is orchestrated through highly regulated temporal and spatial decisions governing the fate of trophoblast stem/progenitor cells. Trophoblast cell acquisition of specializations facilitating invasion and uterine spiral artery remodeling is a labile process, sensitive to the environment, and represents a process that is vulnerable to dysmorphogenesis in pathologic states. Hypoxia is a signal guiding placental development, and molecular mechanisms directing cellular adaptations to low oxygen tension are integral to trophoblast cell differentiation and placentation. Hypoxia can also be used as an experimental tool to investigate regulatory processes controlling hemochorial placentation. These developmental processes are conserved in mouse, rat, and human placentation. Consequently, elements of these developmental events can be modeled and hypotheses tested in trophoblast stem cells and in genetically manipulated rodents. Hypoxia is also a consequence of a failed placenta, yielding pathologies that can adversely affect maternal adjustments to pregnancy, fetal health, and susceptibility to adult disease. The capacity of the placenta for adaptation to environmental challenges highlights the importance of its plasticity in safeguarding a healthy pregnancy. Birth Defects Research 109:1309-1329, 2017.© 2017 Wiley Periodicals, Inc.

Natural killer-cell deficiency alters placental development in rats

Natural killer (NK) cells are the most prevalent leukocyte population in the uterus during early pregnancy. Natural killer cells contribute to uterine vascular (spiral artery) remodeling in preparation for the increased demand on these vessels later in pregnancy. A second wave of spiral artery modification is directed by invasive trophoblast cells. The significance of the initial wave of NK-cell-mediated vascular remodeling in species exhibiting deep trophoblast invasion such as humans and rats is not known. The purpose of this study was to generate a genetic model of NK-cell deficiency in rats, and determine the consequences of NK-cell deficiency on spiral artery remodeling and reproductive outcomes. To accomplish this task, we utilized zinc finger nuclease-mediated genome editing of the rat interleukin-15 (Il15) gene. Il15 encodes a cytokine required for NK-cell lineage development. Using this strategy, a founder rat was generated containing a frameshift deletion in Il15. Uteri of females harboring a homozygous mutation at the Il15 locus contained no detectable NK cells. NK-cell deficiency did not impact fetal growth or viability. However, NK-cell deficiency caused major structural changes to the placenta, including expansion of the junctional zone and robust, early-onset activation of invasive trophoblast-guided spiral artery remodeling. In summary, we successfully generated an NK-cell-deficient rat and showed, using this model, that NK cells dampen the extent of trophoblast invasion and delay trophoblast-directed spiral artery remodeling. This study furthers our understanding of the role of NK cells on uterine vascular remodeling, trophoblast invasion, and placental development.

Association of plasminogen activator inhibitor-type 1 (PAI-1) -675 4G/5G polymorphism with unexplained female infertility

BACKGROUND

Infertility is a major issue of concern for couples at reproductive age.  The underlying causes of infertility remain unknown in 15-30 % of the cases. Plasminogen activator inhibitor type 1 (PAI-1), which is a major fibrinolytic factor, has been associated with increased infertility risk.  DNA variants at PAI-1, such as -675 4G/5G promoter polymorphism, have been implicated in infertility-related reproductive disorders, possibly due to a molecular mechanism involving implantation failure. This study aims to investigate the association of PAI-1 4G/5G polymorphism to otherwise unexplained female infertility in a sample of women of Greek ethnic origins.

METHODS

We enrolled in this study 222 women from the population of Northern Greece; 115 women with unexplained infertility (group 1) and 107 normal fertile women (group 2). All participants were genotyped for PAI-1 -675 by real-time polymerase chain reaction.

RESULTS

Our results indicate an association with the PAI-1 4G allele in our sample of women with unexplained infertility. The dominant genetic model supports the association, in contrast to the recessive genetic model.

CONCLUSIONS

Our results indicate that PAI-1 4G/5G polymorphism is a promising screening factor which could potentially be a target for certain cases of unexplained female infertility. However, they should be interpreted with caution and should be validated in larger studies and diverse populations. In addition, other variants in genes involved in thrombophilia might need to be considered. HIPPOKRATIA 2017, 21(4): 180-185.

Deciphering signature of selection affecting beef quality traits in Angus cattle

Artificial selection towards a desired phenotype/trait has modified the genomes of livestock dramatically that generated breeds that greatly differ in morphology, production and environmental adaptation traits. Angus cattle are among the famous cattle breeds developed for superior beef quality. This paper aimed at exploring genomic regions under selection in Angus cattle that are associated with meat quality traits and other associated phenotypes. The whole genome of 10 Angus cattle was compared with 11 Hanwoo (A-H) and 9 Jersey (A-J) cattle breeds using a cross-population composite likelihood ratio (XP-CLR) statistical method. The top 1% of the empirical distribution was taken as significant and annotated using UMD3.1. As a result, 255 and 210 genes were revealed under selection from A-H and A-J comparisons, respectively. The WebGestalt gene ontology analysis resulted in sixteen (A-H) and five (A-J) significantly enriched KEGG pathways. Several pathways associated with meat quality traits (insulin signaling, type II diabetes mellitus pathway, focal adhesion pathway, and ECM-receptor interaction), and feeding efficiency (olfactory transduction, tight junction, and metabolic pathways) were enriched. Genes affecting beef quality traits (e.g., FABP3, FTO, DGAT2, ACS, ACAA2, CPE, TNNI1), stature and body size (e.g., PLAG1, LYN, CHCHD7, RPS20), fertility and dystocia (e.g., ESR1, RPS20, PPP2R1A, GHRL, PLAG1), feeding efficiency (e.g., PIK3CD, DNAJC28, DNAJC3, GHRL, PLAG1), coat color (e.g., MC1-R) and genetic disorders (e.g., ITGB6, PLAG1) were found to be under positive selection in Angus cattle. The study identified genes and pathways that are related to meat quality traits and other phenotypes of Angus cattle. The findings in this study, after validation using additional or independent dataset, will provide useful information for the study of Angus cattle in particular and beef cattle in general.

Fluid shear stress regulates vascular remodeling via VEGFR-3 activation, although independently of its ligand, VEGF-C, in the uterus during pregnancy

Early pregnancy is characterized by an increase in the blood volume of the uterus for embryonic development, thereby exerting fluid shear stress (FSS) on the vascular walls. The uterus experiences vascular remodeling to accommodate the increased blood flow. The blood flow-induced FSS elevates the expression of vascular endothelial growth factors (VEGFs) and their receptors, and regulates vascular remodeling through the activation of VEGF receptor-3 (VEGFR-3). However, the mechanisms responsible for FSS-induced VEGFR-3 expression in the uterus during pregnancy are unclear. In this study, we demonstrate that vascular remodeling in the uterus during pregnancy is regulated by FSS-induced VEGFR-3 expression. We examined the association between VEGFR-3 and FSS through in vivo and in vitro experiments. In vivo experiments revealed VEGFR-3 expression in the CD31-positive region of the uterus of pregnant mice; VEGF-C (ligand for VEGFR-3) was undetected in the uterus. These results confirmed that VEGFR-3 expression in the endometrium is independent of its ligand. In vitro studies experiments revealed that FSS induced morphological changes and increased VEGFR-3 expression in human uterine microvascular endothelial cells. Thus, VEGFR-3 activation by FSS is associated with vascular remodeling to allow increased blood flow in the uterus during pregnancy.

Role of Plasminogen Activator Inhibitor Type 1 in Pathologies of Female Reproductive Diseases

Normal pregnancy is a state of hypercoagulability with diminishing fibrinolytic activity, which is mainly caused by an increase of plasminogen activator inhibitor type 1 (PAI-1). PAI-1 is the main inhibitor of plasminogen activators, including tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA). In human placentas, PAI-1 is expressed in extravillous interstitial trophoblasts and vascular trophoblasts. During implantation and placentation, PAI-1 is responsible for inhibiting extra cellular matrix (ECM) degradation, thereby causing an inhibition of trophoblasts invasion. In the present study, we have reviewed the literature of various reproductive diseases where PAI-1 plays a role. PAI-1 levels are increased in patients with recurrent pregnancy losses (RPL), preeclampsia, intrauterine growth restriction (IUGR), gestational diabetes mellitus (GDM) in the previous pregnancy, endometriosis and polycystic ovary syndrome (PCOS). In general, an increased expression of PAI-1 in the blood is associated with an increased risk for infertility and a worse pregnancy outcome. GDM and PCOS are related to the genetic role of the 4G/5G polymorphism of PAI-1. This review provides an overview of the current knowledge of the role of PAI-1 in reproductive diseases. PAI-1 represents a promising monitoring biomarker for reproductive diseases and may be a treatment target in the near future.

GATA factors: Master regulators of gene expression in trophoblast progenitors

Mammalian reproduction is critically dependent on trophoblast cells, which ensure embryo implantation and placentation. Development of trophoblast cell lineages is a multi-step process and relies upon proper spatial and temporal gene expression, which is regulated by multiple transcription factors. However, most of the transcription factors that are implicated in trophoblast development regulate gene expression at a specific developmental stage or in a specific trophoblast subtype. In contrast, recent studies from our group and other laboratories indicate that conserved GATA family of transcription factors, GATA2 and GATA3, are important to regulate gene expression at multiple stages of trophoblast development. Furthermore, our conditional gene deletion studies revealed that functional redundancy of GATA2 and GATA3 ensures both self-renewal of trophoblast stem and progenitor cells and their differentiation to trophoblast cells of a matured placenta. Together these findings indicate that GATA2/GATA3 are the master orchestrators of gene expression in trophoblast cells and they fine tune gene regulatory network to establish distinct trophoblast cell types during placentation.

Polychlorinated biphenyls target Notch/Dll and VEGF R2 in the mouse placenta and human trophoblast cell lines for their anti-angiogenic effects

The intrauterine environment is particularly vulnerable to environmental exposures. We previously established a mouse model that provided evidence for pregnancy complications and placental anti-angiogenesis in response to Aroclor 1254 (A-1254), a mixture of polychlorinated biphenyls (PCBs). Importantly, these effects were observed in IL-10^-/-, but not wild type, mice, suggesting that IL-10 deficiency predisposes to pregnancy disruptive effects of environmental toxicants. However, the mechanisms by which PCBs cause anti-angiogenic effects are unclear. Here, we evaluated PCB-mediated anti-angiogenic effects by diverse but complementary approaches, including HUVEC-mediated trophoblast invasion in nude mice, in vitro three-dimensional capillary tube formation involving HUVEC and/or HTR8 trophoblasts, and aortic ring endothelial cell outgrowth/sprouting. Taken together, our data suggest that PCBs act as potent anti-angiogenic agents. Importantly, we show that treatment of pregnant IL-10^-/- mice with A-1254 resulted in placental activation of the Notch/Delta-like ligand (Dll) pathway, a master regulator of cell-cell interaction and vascular patterning. Similar results were obtained with HUVEC and HTR8 trophoblasts. Rescue of A-1254-induced disruption of HUVEC-based tube formation by γ-secretase inhibitor L1790 confirmed the critical role of the Notch/Dll pathway. Our data suggest that PCBs impart pregnancy disruptive functions by activating the Notch/Dll pathway and by inducing anti-angiogenic effects at the maternal-fetal interface.

Ex vivo Trophoblast-specific Genetic Manipulation Using Lentiviral Delivery

In this protocol report, we describe a lentiviral gene delivery technique for genetic modification of the rat trophoblast cell lineage. Lentiviral packaged gene constructs can be efficiently and specifically delivered to the trophoblast cell lineage of the blastocyst. The consequences of 'gain-of-function' and 'loss-of-function' blastocyst manipulations can be evaluated with in vitro outgrowth assays or following transfer to pseudopregnant rats.

Inactivation of maternal Hif-1α at mid-pregnancy causes placental defects and deficits in oxygen delivery to the fetal organs under hypoxic stress

A critical transition occurs near mid-gestation of mammalian pregnancy. Prior to this transition, low concentrations of oxygen (hypoxia) signaling through Hypoxia Inducible Factor (HIF) functions as a morphogen for the placenta and fetal organs. Subsequently, functional coupling of the placenta and fetal cardiovascular system for oxygen (O₂) transport is required to support the continued growth and development of the fetus. Here we tested the hypothesis that Hif-1α is required in maternal cells for placental morphogenesis and function. We used Tamoxifen-inducible Cre-Lox to inactivate Hif-1α in maternal tissues at E8.5 (MATcKO), and used ODD-Luciferase as a reporter of hypoxia in placenta and fetal tissues. MATcKO of Hif-1α reduced the number of uterine natural killer (uNK) cells and Tpbpa-positve trophoblast cells in the maternal decidua at E13.5 -15.5. There were dynamic changes in all three layers of E13.5-15.5 MATcKO placenta. Of note was the under-development of the labyrinth at E15.5 associated with reduced Ki67 and increased TUNEL staining consistent with reduced cell proliferation and increased apoptosis. Labyrinth defects were particularly evident in placentas connected to effectively HIF-1α heterozygous null embryos. MATcKO had no effect on basal ODD-Luciferase activity in fetal organs (heart, liver, brain) at any stage, but at E13.5-15.5 resulted in enhanced induction of the ODD-Luciferase hypoxia reporter when the dam's inspired O₂ was reduced to 8% for 4 hours. MATcKO also slowed the growth after E13.5 of fetuses that were effectively heterozygous for Hif-1α, with most being non-viable at E15.5. The hearts of these E15.5 fetuses were abnormal with reduction in size, thickened epicardium and mesenchymal septum. We conclude that maternal HIF-1α is required for placentation including recruitment of uNK and trophoblast cells into the maternal decidua and other trophoblast cell behaviors. The placental defects render the fetus vulnerable to O₂ deprivation after mid-gestation.

Placental Hypoxia During Early Pregnancy Causes Maternal Hypertension and Placental Insufficiency in the Hypoxic Guinea Pig Model

Chronic placental hypoxia is one of the root causes of placental insufficiencies that result in pre-eclampsia and maternal hypertension. Chronic hypoxia causes disruption of trophoblast (TB) development, invasion into maternal decidua, and remodeling of maternal spiral arteries. The pregnant guinea pig shares several characteristics with humans such as hemomonochorial placenta, villous subplacenta, deep TB invasion, and remodeling of maternal arteries, and is an ideal animal model to study placental development. We hypothesized that chronic placental hypoxia of the pregnant guinea pig inhibits TB invasion and alters spiral artery remodeling. Time-mated pregnant guinea pigs were exposed to either normoxia (NMX) or three levels of hypoxia (HPX: 16%, 12%, or 10.5% O2) from 20 day gestation until midterm (39-40 days) or term (60-65 days). At term, HPX (10.5% O2) increased maternal arterial blood pressure (HPX 57.9 ± 2.3 vs. NMX 40.4 ± 2.3, P < 0.001), decreased fetal weight by 16.1% (P < 0.05), and increased both absolute and relative placenta weights by 10.1% and 31.8%, respectively (P < 0.05). At midterm, there was a significant increase in TB proliferation in HPX placentas as confirmed by increased PCNA and KRT7 staining and elevated ESX1 (TB marker) gene expression (P < 0.05). Additionally, quantitative image analysis revealed decreased invasion of maternal blood vessels by TB cells. In summary, this animal model of placental HPX identifies several aspects of abnormal placental development, including increased TB proliferation and decreased migration and invasion of TBs into the spiral arteries, the consequences of which are associated with maternal hypertension and fetal growth restriction.

HIF-KDM3A-MMP12 regulatory circuit ensures trophoblast plasticity and placental adaptations to hypoxia

The hemochorial placenta develops from the coordinated multilineage differentiation of trophoblast stem (TS) cells. An invasive trophoblast cell lineage remodels uterine spiral arteries, facilitating nutrient flow, failure of which is associated with pathological conditions such as preeclampsia, intrauterine growth restriction, and preterm birth. Hypoxia plays an instructive role in influencing trophoblast cell differentiation and regulating placental organization. Key downstream hypoxia-activated events were delineated using rat TS cells and tested in vivo, using trophoblast-specific lentiviral gene delivery and genome editing. DNA microarray analyses performed on rat TS cells exposed to ambient or low oxygen and pregnant rats exposed to ambient or hypoxic conditions showed up-regulation of genes characteristic of an invasive/vascular remodeling/inflammatory phenotype. Among the shared up-regulated genes was matrix metallopeptidase 12 (MMP12). To explore the functional importance of MMP12 in trophoblast cell-directed spiral artery remodeling, we generated an Mmp12 mutant rat model using transcription activator-like nucleases-mediated genome editing. Homozygous mutant placentation sites showed decreased hypoxia-dependent endovascular trophoblast invasion and impaired trophoblast-directed spiral artery remodeling. A link was established between hypoxia/HIF and MMP12; however, evidence did not support Mmp12 as a direct target of HIF action. Lysine demethylase 3A (KDM3A) was identified as mediator of hypoxia/HIF regulation of Mmp12 Knockdown of KDM3A in rat TS cells inhibited the expression of a subset of the hypoxia-hypoxia inducible factor (HIF)-dependent transcripts, including Mmp12, altered H3K9 methylation status, and decreased hypoxia-induced trophoblast cell invasion in vitro and in vivo. The hypoxia-HIF-KDM3A-MMP12 regulatory circuit is conserved and facilitates placental adaptations to environmental challenges.

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.