NOTUM-MEDIATED WNT SILENCING DRIVES EXTRAVILLOUS TROPHOBLAST CELL LINEAGE DEVELOPMENT

Trophoblast stem (TS) cells have the unique capacity to differentiate into specialized cell types, including extravillous trophoblast (EVT) cells. EVT cells invade into and transform the uterus where they act to remodel the vasculature facilitating the redirection of maternal nutrients to the developing fetus. Disruptions in EVT cell development and function are at the core of pregnancy-related disease. WNT-activated signal transduction is a conserved regulator of morphogenesis of many organ systems, including the placenta. In human TS cells, activation of canonical WNT signaling is critical for maintenance of the TS cell stem state and its downregulation accompanies EVT cell differentiation. We show that aberrant WNT signaling undermines EVT cell differentiation. Notum, palmitoleoyl-protein carboxylesterase (NOTUM), a negative regulator of canonical WNT signaling, was prominently expressed in first trimester EVT cells developing in situ and upregulated in EVT cells derived from human TS cells. Furthermore, NOTUM was required for human TS cell differentiation to EVT cells. Activation of NOTUM in EVT cells is driven, at least in part, by endothelial PAS domain 1 (also called hypoxia-inducible factor 2 alpha). Collectively, our findings indicate that canonical WNT signaling is essential for maintenance of human trophoblast cell stemness and prevention of human TS cell differentiation. Downregulation of canonical WNT signaling via the actions of NOTUM is required for EVT cell differentiation.

An Improved Protocol for Targeted Differentiation of Primed Human Induced Pluripotent Stem Cells into HLA-G-Expressing Trophoblasts to Enable the Modeling of Placenta-Related Disorders

Abnormalities at any stage of trophoblast development may result in pregnancy-related complications. Many of these adverse outcomes are discovered later in pregnancy, but the underlying pathomechanisms are constituted during the first trimester. Acquiring developmentally relevant material to elucidate the disease mechanisms is difficult. Human pluripotent stem cell (hPSC) technology can provide a renewable source of relevant cells. BMP4, A83-01, and PD173074 (BAP) treatment drives trophoblast commitment of hPSCs toward syncytiotrophoblast (STB), but lacks extravillous trophoblast (EVT) cells. EVTs mediate key functions during placentation, remodeling of uterine spiral arteries, and maintenance of immunological tolerance. We optimized the protocol for a more efficient generation of HLA-Gpos EVT-like trophoblasts from primed hiPSCs. Increasing the concentrations of A83-01 and PD173074, while decreasing bulk cell density resulted in an increase in HLA-G of up to 71%. Gene expression profiling supports the advancements of our treatment regarding the generation of trophoblast cells. The reported differentiation protocol will allow for an on-demand access to human trophoblast cells enriched for HLA-Gpos EVT-like cells, allowing for the elucidation of placenta-related disorders and investigating the immunological tolerance toward the fetus, overcoming the difficulties in obtaining primary EVTs without the need for a complex differentiation pathway via naïve pluripotent or trophoblast stem cells.

Advanced Strategy of Trophoblasts Retrieval and Isolation from the Cervix (TRIC): Comparison of Two HLA-G Antibodies for Immunomagnetic Isolation of Trophoblasts

Trophoblasts retrieval and isolation from the cervix (TRIC) is a non-invasive method which enables analysis of fetal genetic information from the extravillous trophoblast cells (EVTs). The aim of this study was to compare the efficacy of the HLA-G antibodies—G233 and 4H84—in isolating EVT cells and provide an optimized protocol of TRIC. We analyzed EVTs from 23 pregnant women in between 5 to 20 weeks of gestation who underwent invasive prenatal testing. Two HLA-G antibodies—G233 and 4H84—were used in a subgroup of 11 and 12 samples for immunomagnetic isolation. Cells with β-hCG expression were counted to compare the rate of isolated trophoblast cells. The rate of β-hCG positive cells was significantly different between the G233 and the 4H84 by immunefluorescence microscopy (p < 0.001). The percentage of β-hCG expressing cells in G233 and 4H84 groups were 62.4 ± 8.24% and 82.6 ± 7.1%, respectively (p < 0.001). The average fetal cell positive rate was 14.1 ± 3.78 in the G233 group while it was 25.8 ± 3.9 in the 4H84 group by fluorescence in situ hybridization (FISH) (p = 0.011). Immunoisolation of trophoblast cells using 4H84 HLA-G antibody was more efficient in capturing EVT cells than using G233 for successful clinical application of TRIC.

Decidual Natural Killer Cells: A Good Nanny at the Maternal-Fetal Interface During Early Pregnancy

Decidual natural killer (dNK) cells are the tissue-resident and major subpopulation of NK cells at the maternal-fetal interface. It has been demonstrated that dNK cells play pivotal roles in pregnancy, including keeping maternal-fetal immune tolerance, promoting extravillous trophoblast (EVT) cell invasion, and driving uterine spiral artery remodeling. However, the molecular mechanisms haven't been elucidated until recent years. In this review, we systemically introduce the generation, subsets, and surface or soluble molecules of dNK cells, which are critical for maintaining the functions of dNK cells. Further, new functions of dNK cells including well-controlled cytotoxicity, immunosurveillance and immunotrophism supporting via the cell-cell interaction between dNK cells and EVT cells are mainly focused. The molecular mechanisms involved in these functions are also illustrated. Moreover, pregnancy-associated diseases caused by the dNK cells abnormalities are discussed. It will be important for future investigations about the mechanism of maintenance of pregnancy and parturition and potential clinical applications of dNK cells.

Vitamin D Promotes Trophoblast Cell Induced Separation of Vascular Smooth Muscle Cells in Vascular Remodeling via Induction of G-CSF

Vitamin D deficiency is associated with complications of pregnancy such as pre-eclampsia, fetal growth restriction, and miscarriage, all of which are also associated with incomplete spiral artery (SpA) remodeling. We have previously shown that both uterine natural killer (uNK) cells and extravillous trophoblast cells (EVT) are required for successful SpA remodeling, but whether their activity in this process is modulated by vitamin D is not known. In the current study, we use a previously described chorionic plate artery (CPA) ex vivo model of vascular remodeling to determine the effects of 1,25(OH)₂D treated uNK cell, placental explant (PEx), and uNK/PEx conditioned medium (CM) on vascular smooth muscle cell (VSMC) disorganization and phenotypic switching. Significant results were followed up in VSMCs in vitro. We demonstrate that 1,25(OH)₂D can enhance the ability of PEx to induce SpA remodeling, via a mechanism associated with increased secretion of granulocyte-colony stimulating factor (G-CSF). G-CSF appears able to increase VSMC disorganization and phenotypic switching in both an ex vivo vascular model and in vitro VSMC cultures. The clinical relevance of these findings are still to be determined. G-CSF may have differential effects depending on dose and vascular bed, and vitamin D may play a role in potentiating these actions. G-CSF may be an interesting potential therapeutic target for facilitating physiological vascular remodeling for the prevention of adverse obstetric outcomes.

Effects of gestational diabetes mellitus on stereological parameters and extravillous trophoblast cells of placenta compared to the control group

The quantitative changes of extravillous trophoblast cells (EVTs) in placenta of gestational diabetes mellitus (GDM) patients were investigated compared to healthy controls using stereological methods. The volumetric parameters of the placenta and EVTs were estimated using Cavalieri's principle and Physical Disector stereological methods. The placental volume and weight in the GDM group increased compared to the control group (p < .05). The difference in the total volume of intervillous space and blood vessels of the placenta between GDM and control groups was statistically significant (p < .05). In addition, there was a significant difference in the volume density of blood vessels and syncytiotrophoblast between the GDM group and the control group (p < .05). The total volume of the EVTs, nucleus and cytoplasm diameter, volume of the nucleus and cytoplasm, nucleus to cytoplasm ratio (N/C) of EVTs and the total number of EVTs per unit volume of the placenta in the GDM group showed a significant increase compared to the controls (p < .05). Impact statement What is already known on this subject? It is reported that extravillous trophoblast cells (EVTs) played an important role in pregnancy complications. There are limited studies on the quantitative changes of EVTs in the placental bed of GDM patients. What do the results of this study add? The results showed that volumetric parameters and number of EVTs were significantly altered in GDM placentas. These changes can be associated with disturbances in trophoblastic invasion in GDM pregnancies and may affect the development and survival of the embryo. What are the implications of these findings for clinical practice and/or further research? In the present study, there is a new insight to placenta structure that probably could be useful to understanding possible mechanisms of pregnancy complications and the achievement of new therapeutic strategies. Further investigation on the molecular biology of these cells in pregnancy complications will be needed to clarify this hypothesis.

Three macrophage subsets are identified in the uterus during early human pregnancy

Macrophages are crucial for a successful pregnancy, and malfunctions of decidual macrophages correlate with adverse pregnancy outcomes, such as spontaneous abortion and preeclampsia. Previously, decidual macrophages were often thought to be a single population. In the present study, we identified three decidual macrophage subsets, CCR2-CD11cLO (CD11c^low, ~80%), CCR2-CD11cHI (CD11c^high, ~5%), and CCR2+CD11cHI (CD11c^high, 10-15%), during the first trimester of human pregnancy by flow cytometry analysis. CCR2-CD11cLO macrophages are widely distributed in the decidua, while CCR2-CD11cHI and CCR2+CD11cHI macrophages are primarily detected close to extravillous trophoblast cells according to immunofluorescence staining. According to RNA sequencing bioinformatics analysis and in vitro functional studies, these three subsets of macrophages have different phagocytic capacities. CCR2+CD11cHI macrophages have pro-inflammatory characteristics, while the CCR2-CD11cHI population is suggested to be anti-oxidative and anti-inflammatory due to its high expression of critical heme metabolism-related genes, suggesting that these two subsets of macrophages maintain an inflammatory balance at the leading edge of trophoblast invasion to facilitate the clearance of pathogen infection as well as maintain the homeostasis of the maternal-fetal interface. The present study physiologically identifies three decidual macrophage subsets. Further clarification of the functions of these subsets will improve our understanding of maternal-fetal crosstalk in the maintenance of a healthy pregnancy.

The term basal plate of the human placenta as a source of functional extravillous trophoblast cells

BACKGROUND

Extravillous trophoblast (EVT) cells are of pivotal importance in human embryo implantation and homeostasis of the maternal fetal interface. Invasion of the endometrium by EVT contributes to placental anchorage, spiral artery remodeling, immunological defense, tolerogenic responses, and several collaborative cross talks involved in establishing and maintaining a successful pregnancy. We report here an improved protocol for the isolation of fully differentiated EVT cells from the basal plate of the human term placenta.

METHODS

The basal plate was carefully dissected from the villous tissue and the amniochorion membrane prior to enzymatic digestion. Term basal EVT cells were isolated using a 30 and 60% Percoll gradient. A panel of markers and characteristics of the isolated cells were used to confirm the specificity and efficiency of the method so that their potential as an investigative tool for placental research could be ascertained.

RESULTS

Isolated cells were immunoreactive for cytokeratin-7 (CK-7), placental growth factor, placental alkaline phosphatase, human leukocyte antigen G1 (HLA-G1), and α1 and α5 integrins, similarly to the EVT markers from first trimester placental villi. Around 95% of the isolated cells labeled positively for CK-7 and 82% for HLA-G1. No significant change in viability was observed during 48 h of EVT culture as indicated by propidium iodide incorporation and trypan blue test exclusion. Genes for metalloproteinases MMP-2 and MMP9 (positive regulators of trophoblast invasiveness) were expressed up to 48 h of culturing, as also the gelatinolytic activity of the isolated cells. Transforming growth factor (TGF)-beta, which inhibits proliferation, migration, and invasiveness of first-trimester EVT cells, also reduced invasion of isolated term EVT cells in transwell assays, whereas epidermal growth factor was a positive modulator.

CONCLUSIONS

Term basal plate may be a viable source of functional EVT cells that is an alternative to villous explant-derived EVT cells and cell lines. Isolated term EVT cells may be particularly useful in investigation of the role of trophoblast cells in pathological gestations, in which the precise regulation and interactive ability of extravillous trophoblast has been impaired.