Victoria Kunihs

Insights into the molecular processes that drive early development of the human placenta is crucial for our understanding of pregnancy complications such as preeclampsia and fetal growth restriction, since defects in maturation of its epithelial cell, the trophoblast, have been detected in the severe forms of these diseases. However, key regulators specifying the differentiated trophoblast subtypes of the placenta are only slowly emerging. By using diverse trophoblast cell models, we herein show that the transcriptional coactivator of HIPPO signaling, TAZ, plays a pivotal role in the development of invasive extravillous trophoblasts (EVTs), cells that are essential for decidual vessel remodeling and adaption of maternal blood flow to the placenta. Ribonucleic acid sequencing (RNA-seq) or protein analyses upon TAZ gene silencing or CRISPR-Cas9-mediated knockout in differentiating trophoblast stem cells, organoids, primary EVTs, choriocarcinoma cells, or villous explant cultures unraveled that the coactivator promoted expression of genes associated with EVT identity, motility, and survival. Accordingly, depletion or chemical inhibition of TAZ, interacting with TEA domain family member 1 (TEAD1), impaired EVT differentiation, invasion, and migration and triggered apoptosis in the different trophoblast models. Notably, the coactivator also suppressed cell cycle genes and regulators of trophoblast self-renewal and prevented EVTs from cell fusion in organoids and primary cultures. Moreover, TAZ promoted human leukocyte antigen G (HLA-G) surface expression and increased NUAK1 kinase in EVTs thereby maintaining its own expression. In summary, the transcriptional coactivator TAZ plays a multifaceted role in the development of the EVT cell lineage by controlling different biological processes that initiate and preserve differentiation.

Failures in growth and differentiation of the early human placenta are associated with severe pregnancy disorders such as pre-eclampsia and fetal growth restriction. However, regulatory mechanisms controlling development of placental epithelial cells, the trophoblasts, remain poorly elucidated. Using trophoblast stem cells (TSCs), trophoblast organoids (TB-ORGs) and primary cytotrophoblasts (CTBs) of early pregnancy, we herein show that autocrine NOTCH3 signalling controls human placental expansion and differentiation. The NOTCH3 receptor was specifically expressed in proliferative CTB progenitors and its active form, the nuclear NOTCH3 intracellular domain (NOTCH3-ICD), interacted with the transcriptional co-activator mastermind-like 1 (MAML1). Doxycycline-inducible expression of dominant-negative MAML1 in TSC lines provoked cell fusion and upregulation of genes specific for multinucleated syncytiotrophoblasts, which are the differentiated hormone-producing cells of the placenta. However, progenitor expansion and markers of trophoblast stemness and proliferation were suppressed. Accordingly, inhibition of NOTCH3 signalling diminished growth of TB-ORGs, whereas overexpression of NOTCH3-ICD in primary CTBs and TSCs showed opposite effects. In conclusion, the data suggest that canonical NOTCH3 signalling plays a key role in human placental development by promoting self-renewal of CTB progenitors.

Failures in growth and differentiation of the early human placenta are associated with severe pregnancy disorders such as preeclampsia and fetal growth restriction. However, regulatory mechanisms controlling development of its epithelial cells, the trophoblasts, remain poorly elucidated. Using trophoblast stem cells (TSCs), trophoblast organoids (TB-ORGs) and primary cytotrophoblasts (CTBs) of early pregnancy, we herein show that autocrine NOTCH3 signalling controls human placental expansion and differentiation. NOTCH3 receptor was specifically expressed in proliferative CTB progenitors and its active form, the nuclear NOTCH3 intracellular domain (NOTCH3-ICD), interacted with the transcriptional co-activator Mastermind-like 1 (MAML1). Doxycyclin-inducible expression of dominant-negative MAML1 in TSC lines provoked cell fusion and upregulation of genes specific for multinucleated syncytiotrophoblasts, the differentiated hormone-producing cell type of the placenta. However, progenitor expansion and markers of trophoblast stemness and proliferation were suppressed. Accordingly, inhibition of NOTCH3 signalling diminished growth of TB-ORGs whereas overexpression of NOTCH3-ICD in primary CTBs and TSCs showed opposite effects. In conclusion, the data suggest that canonical NOTCH3 signalling plays a key role in human placental development promoting self-renewal of CTB progenitors.

Abnormal placentation has been noticed in a variety of pregnancy complications such as miscarriage, early-onset preeclampsia, and fetal growth restriction. Defects in the developmental program of extravillous trophoblasts (EVTs), migrating from placental anchoring villi into the maternal decidua and its vessels, is thought to be an underlying cause. Yet, key regulatory mechanisms controlling commitment and differentiation of the invasive trophoblast lineage remain largely elusive. Herein, comparative gene expression analyses of HLA-G–purified EVTs, isolated from donor-matched placenta, decidua, and trophoblast organoids (TB-ORGs), revealed biological processes and signaling pathways governing EVT development. In particular, bioinformatics analyses and manipulations in different versatile trophoblast cell models unraveled transforming growth factor-β (TGF-β) signaling as a crucial pathway driving differentiation of placental EVTs into decidual EVTs, the latter showing enrichment of a secretory gene signature. Removal of Wingless signaling and subsequent activation of the TGF-β pathway were required for the formation of human leukocyte antigen-G ⁺ (HLA-G ⁺ ) EVTs in TB-ORGs that resemble in situ EVTs at the level of global gene expression. Accordingly, TGF-β–treated EVTs secreted enzymes, such as DAO and PAPPA2, which were predominantly expressed by decidual EVTs. Their genes were controlled by EVT-specific induction and genomic binding of the TGF-β downstream effector SMAD3. In summary, TGF-β signaling plays a key role in human placental development governing the differentiation program of EVTs.

During human pregnancy, placenta-derived extravillous trophoblasts (EVT) invade the decidua and communicate with maternal immune cells. The decidua can be distinguished into basalis (decB) and parietalis (decP), the latter being unaffected by placentation. By defining a novel gating strategy, we report accumulation of myeloid cells in decB. We identified a decidua basalis-associated macrophage (decBAM) population with a differential transcriptome and secretome when compared to decidua parietalis-associated macrophages (decPAMs). decBAMs are CD11c ^hi and efficient inducers of Tregs, proliferate in situ and secrete high levels of CXCL1, CXCL5, M-CSF, and IL-10. In contrast, decPAMs exert a dendritic cell-like, motile phenotype characterized by induced expression of HLA class II molecules, enhanced phagocytosis, and the ability to activate T cells. Strikingly, EVT-conditioned media are able to convert decPAMs into a decBAM phenotype. Cumulatively, these findings assign distinct macrophage phenotypes to decidual areas depending on placentation and further highlight a critical role for EVTs in the induction of pregnancy-tolerant macrophage polarization. Graphical Highlights: In this study, we identified so far unrecognized, placenta-induced immune responses at the maternal-fetal interface. Altogether, we imply that placenta-derived trophoblasts induce a pregnancy-tolerant phenotype by suppressing antigen-presenting cell-like functions in maternal tissue macrophages.

Objective: 3D optical coherence tomography (OCT) is used for analyses of human placenta organoids in situ without sample preparation. Methods: The trophoblast organoids analyzed were derived from primary human trophoblast. In this study a custom made ultra-high-resolution spectral domain OCT system with uniform spatial and axial resolution of 2.48 m in organoid tissue was used. The obtained OCT results align to differentiation status tested via quantitative polymerase chain reaction, Western blot analyses, immunohistochemistry, and immunofluorescence of histological sections. Results: 3D OCT enables a more detailed placenta organoid monitoring compared to brightfield microscopy. Inner architecture with light scattering bridges surrounding cavities were visualized and quantified in situ for the first time. The formation of these bridges and cavities is congruent to differentiated trophoblast organoids having developed syncytiotrophoblasts. Conclusion: Using 3D OCT in living placenta organoids is a fast tool to assess the differentiation status and resolve internal structures in situ, which is not possible with standard live cell imaging modality. Significance: Only recently human placenta-derived organoids were established, allowing to have a highly reproducible and stable in vitro model to investigate not only developmental but also physiological and pathophysiological processes during early pregnancy. To our knowledge, this work is the first to analyze living human placenta organoids using 3D OCT. Thereby, the rapid and especially non- endpoint OCT qualitative analyses align to the differentiation stage of organoids, which will aid future advancement in this field.

Various pregnancy complications, such as severe forms of preeclampsia or intrauterine growth restriction, are thought to arise from failures in the differentiation of human placental trophoblasts. Progenitors of the latter either develop into invasive extravillous trophoblasts, remodeling the uterine vasculature, or fuse into multinuclear syncytiotrophoblasts transporting oxygen and nutrients to the growing fetus. However, key regulatory factors controlling trophoblast self-renewal and differentiation have been poorly elucidated. Using primary cells, three-dimensional organoids, and CRISPR-Cas9 genome-edited JEG-3 clones, we herein show that YAP, the transcriptional coactivator of the Hippo signaling pathway, promotes maintenance of cytotrophoblast progenitors by different genomic mechanisms. Genetic or chemical manipulation of YAP in these cellular models revealed that it stimulates proliferation and expression of cell cycle regulators and stemness-associated genes, but inhibits cell fusion and production of syncytiotrophoblast (STB)-specific proteins, such as hCG and GDF15. Genome-wide comparisons of primary villous cytotrophoblasts overexpressing constitutively active YAP-5SA with YAP KO cells and syncytializing trophoblasts revealed common target genes involved in trophoblast stemness and differentiation. ChIP-qPCR unraveled that YAP-5SA overexpression increased binding of YAP–TEAD4 complexes to promoters of proliferation-associated genes such as CCNA and CDK6 . Moreover, repressive YAP–TEAD4 complexes containing the histone methyltransferase EZH2 were detected in the genomic regions of the STB-specific CGB5 and CGB7 genes. In summary, YAP plays a pivotal role in the maintenance of the human placental trophoblast epithelium. Besides activating stemness factors, it also directly represses genes promoting trophoblast cell fusion.

The human endometrium is the inner lining of the uterus consisting of stromal and epithelial (secretory and ciliated) cells. It undergoes a hormonally regulated monthly cycle of growth, differentiation, and desquamation. However, how these cyclic changes control the balance between secretory and ciliated cells remains unclear. Here, we established endometrial organoids to investigate the estrogen (E2)-driven control of cell fate decisions in human endometrial epithelium. We demonstrate that they preserve the structure, expression patterns, secretory properties, and E2 responsiveness of their tissue of origin. Next, we show that the induction of ciliated cells is orchestrated by the coordinated action of E2 and NOTCH signaling. Although E2 is the primary driver, inhibition of NOTCH signaling provides a permissive environment. However, inhibition of NOTCH alone is not sufficient to trigger ciliogenesis. Overall, we provide insights into endometrial biology and propose endometrial organoids as a robust and powerful model for studying ciliogenesis in vitro.