Trophoblasts

BackgroundWith increasing significance of developmental programming effects associated with placental dysfunction, more investigations are devoted to improving the characterization and understanding of placental signatures in health and disease. The placenta is a transitory but dynamic organ adapting to the shifting demands of fetal development and available resources of the maternal supply throughout pregnancy. Trophoblasts (cytotrophoblasts, syncytiotrophoblasts, and extravillous trophoblasts) are placental-specific cell types responsible for the main placental exchanges and adaptations. Transcriptomic studies with single-cell resolution have led to advances in understanding the placenta's role in health and disease. These studies, however, often show discrepancies in characterization of the different placental cell types.Objective and rationaleWe aim to review the knowledge regarding placental structure and function gained from the use of single-cell RNA sequencing (scRNAseq), followed by comparing cell-type-specific genes, highlighting their similarities and differences. Moreover, we intend to identify consensus marker genes for the various trophoblast cell types across studies. Finally, we will discuss the contributions and potential applications of scRNAseq in studying pregnancy-related diseases.Search methodsWe conducted a comprehensive systematic literature review to identify different cell types and their functions at the human maternal-fetal interface, focusing on all original scRNAseq studies on placentas published before March 2023 and published reviews (total of 28 studies identified) using PubMed search. Our approach involved curating cell types and subtypes that had previously been defined using scRNAseq and comparing the genes used as markers or identified as potential new markers. Next, we reanalyzed expression matrices from the six available scRNAseq raw datasets with cell annotations (four from first trimester and two at term), using Wilcoxon rank-sum tests to compare gene expression among studies and annotate trophoblast cell markers in both first trimester and term placentas. Furthermore, we integrated scRNAseq raw data available from 18 healthy first trimester and nine term placentas, and performed clustering and differential gene expression analysis. We further compared markers obtained with the analysis of annotated and raw datasets with the literature to obtain a common signature gene list for major placental cell types.OutcomesVariations in the sampling site, gestational age, fetal sex, and subsequent sequencing and analysis methods were observed between the studies. Although their proportions varied, the three trophoblast types were consistently identified across all scRNAseq studies, unlike other non-trophoblast cell types. Notably, no marker genes were shared by all studies for any of the investigated cell types. Moreover, most of the newly defined markers in one study were not observed in other studies. These discrepancies were confirmed by our analysis on trophoblast cell types, where hundreds of potential marker genes were identified in each study but with little overlap across studies. From 35 461 and 23 378 cells of high quality in the first trimester and term placentas, respectively, we obtained major placental cell types, including perivascular cells that previously had not been identified in the first trimester. Importantly, our meta-analysis provides marker genes for major placental cell types based on our extensive curation.Wider implicationsThis review and meta-analysis emphasizes the need for establishing a consensus for annotating placental cell types from scRNAseq data. The marker genes identified here can be deployed for defining human placental cell types, thereby facilitating and improving the reproducibility of trophoblast cell annotation.

Preeclampsia (PE) is considered as a disease of placental origin. However, the specific mechanism of placental abnormalities remains elusive. This study identified thrombospondin-1 (THBS1) is downregulated in preeclamptic placentae and negatively correlated with blood pressure. Functional studies show that THBS1 knockdown inhibits proliferation, migration, and invasion and increases the cycle arrest and apoptosis rate of HTR8/SVneo cells. Importantly, THBS1 silencing induces necroptosis in HTR8/SVneo cells, accompanied by the release of damage-associated molecular patterns (DAMPs). Necroptosis inhibitors necrostatin-1 and GSK'872 restore the trophoblast survival while pan-caspase inhibitor Z-VAD-FMK has no effect. Mechanistically, the results show that THBS1 interacts with transforming growth factor B-activated kinase 1 (TAK1), which is a central modulator of necroptosis quiescence and affects its stability. Moreover, THBS1 silencing up-regulates the expression of neuronal precursor cell-expressed developmentally down-regulated 4 (NEDD4), which acts as an E3 ligase of TAK1 and catalyzes K48-linked ubiquitination of TAK1 in HTR8/SVneo cells. Besides, THBS1 attenuates PE phenotypes and improves the placental necroptosis in vivo. Taken together, the down-regulation of THBS1 destabilizes TAK1 by activating NEDD4-mediated, K48-linked TAK1 ubiquitination and promotes necroptosis and DAMPs release in trophoblast cells, thus participating in the pathogenesis of PE.

BackgroundGestational diabetes mellitus (GDM) has been associated with several fetal complications, such as macrosomia and fetal growth restriction (FGR). Infants from GDM associated FGR are at increased risk for adult-onset obesity and associated metabolic disorders. However, the underlying mechanisms of GDM associated FGR remain to be explored.MethodsWe analyzed placentas from GDM patients with FGR for ferroptosis markers and GLUT1 expression. High glucose conditions were established by adding different concentrations of D-Glucose to the 1640 cell culture medium. RSL3 were used to test ferroptosis sensitivity in trophoblast cells. GLUT1 was inhibited using siRNA or its inhibitor WZB117 to assess its impact on ferroptosis inhibition in HTR8/SVneo cell line. Mechanistic studies explored the effects of GLUT1 on AMPK and ACC phosphorylation, which in turn impacted lipid metabolism and ferroptosis. In mouse models, streptozotocin (STZ)-induced GDM was treated with WZB117 and the ferroptosis inhibitor liproxstatin-1 (Lip-1). Finally, AMPK and ACC phosphorylation levels were evaluated in GDM patient samples.ResultsIn this study, placentas from GDM patients with FGR showed signs of ferroptosis and upregulation of GLUT1. In cell models, high glucose conditions sensitized trophoblast cells to ferroptosis and induced GLUT1 expression. Interestingly, GLUT1 inhibition significantly suppressed ferroptosis in trophoblast cells under high glucose conditions. Mechanistically, elevated GLUT1 inhibited AMPK phosphorylation and reduced ACC phosphorylation, thereby promoting lipid synthesis and facilitating ferroptosis. In pregnant mice, STZ-induced hyperglycemia led to FGR, and treatment with either the GLUT1 inhibitor WZB117 or the ferroptosis inhibitor Lip-1 alleviated the FGR phenotype. Moreover, in vivo elevation of GLUT1 increased ferroptosis markers, decreased AMPK/ACC phosphorylation, and resulted in altered lipid metabolism, which likely contributed to the observed phenotype. Finally, placental samples from GDM patients showed reduced AMPK and ACC phosphorylation.ConclusionsOur findings suggest a potential role of ferroptosis in GDM associated FGR and indicate that the dysregulated GLUT1-AMPK-ACC axis may be involved in the pathogenesis of GDM associated FGR in clinicals.

Senescent cells display indefinite growth arrest and a pro-inflammatory, senescence-associated secretory phenotype (SASP). As the accumulation of senescent cells in tissues with age plays detrimental roles in age-related pathologies, there is much interest in finding therapeutic strategies to eliminate them or suppress the SASP. In this study, we investigated the impact of the secretome and extracellular vesicles (EVs) derived from human trophoblast stem cells (hTSCs) on senescent human fibroblasts. We found that the hTSC conditioned medium (hTSC-CM), and in particular the EVs (hTSC-EVs), significantly reduced the levels of mRNAs encoding SASP factors and the secretion of SASP factors including CXCL1, IL8, and GDF15. Proteomic analysis of hTSC-CM and EVs indicated an enrichment in proteins involved in cell adhesion, tissue repair, and remodeling of the extracellular matrix (ECM). Furthermore, incubation of senescent cells with hTSC-EVs attenuated DNA damage and inflammatory signaling, at least in part by suppressing the function of NF-κB, a major transcriptional regulator of the SASP program. Our findings underscore the value of hTSC-CM and EVs therein in therapeutic approaches directed at senescent cells.