Immunohistochemical location of HPL, SP1 and beta-HCG in normal placentas of varying gestational age

Comparative analysis of the syncytiotrophoblast in placenta tissue and trophoblast organoids using snRNA sequencing

The syncytiotrophoblast (STB) is a multinucleated cell layer that forms the outer surface of human chorionic villi. Its unusual structure, with billions of nuclei in a single cell, makes it difficult to resolve using conventional single-cell methods. To better understand STB differentiation, we performed single-nucleus and single-cell RNA sequencing on placental tissue and trophoblast organoids (TOs). Single-nucleus RNA-seq was essential for capturing STB populations, revealing three nuclear subtypes: a juvenile subtype co-expressing CTB and STB markers, one enriched in oxygen sensing genes, and another in transport and GTPase signaling. Organoids grown in suspension culture (STBout) showed higher expression of STB markers, hormones, and a greater proportion of the transport-associated nuclear subtype while TOs grown with an inverted polarity (STBin) exhibited a higher proportion of the oxygen sensing nuclear subtype. Gene regulatory analysis identified conserved STB markers, including the chromatin remodeler RYBP. Although RYBP knockout did not impair fusion, it downregulated CSH1 and upregulated oxygen-sensing genes. Comparing STB expression in first trimester, term, and TOs revealed shared features but context-dependent variability. These findings establish TOs as a robust platform to model STB differentiation and nuclear heterogeneity, providing insight into the regulatory networks that shape placental development and function.

Comparative analysis of the syncytiotrophoblast in placenta tissue and trophoblast organoids using snRNA sequencing

The outer surface of chorionic villi in the human placenta consists of a single multinucleated cell called the syncytiotrophoblast (STB). The unique cellular ultrastructure of the STB presents challenges in deciphering its gene expression signature at the single-cell level, as the STB contains billions of nuclei in a single cell. There are many gaps in understanding the molecular mechanisms and developmental trajectories involved in STB formation and differentiation. To identify the underlying control of the STB, we performed comparative single nucleus (SN) and single cell (SC) RNA sequencing on placental tissue and tissue-derived trophoblast organoids (TOs). We found that SN RNA sequencing was essential to capture the STB population from both tissue and TOs. Differential gene expression and pseudotime analysis of TO-derived STB identified three distinct nuclear subtypes reminiscent of those recently identified in vivo . These included a juvenile nuclear population that exhibited both CTB and STB marker expression, a population enriched in genes involved in oxygen sensing, and finally a subtype enriched in transport and GTPase signaling molecules. Notably, suspension culture conditions of TOs that restore the native orientation of the STB (STB out ) showed elevated expression of canonical STB markers and pregnancy hormones, along with a greater proportion of the STB nucleus subtype specializing in transport and GTPase signaling, compared to those cultivated with an inverted STB polarity (STB in ). Gene regulatory analysis identified novel markers of STB differentiation conserved in tissue and TOs, including the chromatin remodeler RYBP, that exhibited STB-specific RNA and protein expression. CRISPR/Cas9 knockout of RYBP in STB in TOs did not impact cell-cell fusion; however, bulk RNA sequencing revealed downregulation of the pregnancy hormone CSH1 and upregulation of multiple genes associated with the oxygen-sensing STB nuclear subtype. Finally, we compared STB gene expression signatures amongst first trimester tissue, full-term tissue, and TOs, identifying many commonalities but also notable variability across each sample type. This indicates that STB gene expression is responsive to its environmental context. Our findings emphasize the utility of TOs to accurately model STB differentiation and the distinct nuclear subtypes observed in vivo , offering a versatile platform for unraveling the molecular mechanisms governing STB functions in placental biology and disease.

RNA-Seq reveals changes in human placental metabolism, transport and endocrinology across the first-second trimester transition

The human placenta is exposed to major environmental changes towards the end of the first trimester associated with full onset of the maternal arterial placental circulation. Changes include a switch from histotrophic to hemotrophic nutrition, and a threefold rise in the intraplacental oxygen concentration. We evaluated their impact on trophoblast development and function using RNA-sequencing (RNA-Seq) and DNA-methylation analyses performed on the same chorionic villous samples at 7-8 (n=8) and 13-14 (n=6) weeks of gestation. Reads were adjusted for fetal sex. Most DEGs were associated with protein processing in the endoplasmic reticulum (ER), hormone secretion, transport, extracellular matrix, vasculogenesis, and reactive oxygen species metabolism. Transcripts higher in the first trimester were associated with synthesis and ER processing of peptide hormones, and glycolytic pathways. Transcripts encoding proteins mediating transport of oxygen, lipids, protein, glucose, and ions were significantly increased in the second trimester. The motifs of CBX3 and BCL6 were significantly overrepresented, indicating the involvement of these transcription factor networks in the regulation of trophoblast migration, proliferation and fusion. These findings are consistent with a high level of cell proliferation and hormone secretion by the early placenta to secure implantation in a physiological low-oxygen environment.

Oxidative Damage and Nrf2 Translocation Induced by Toxicities of Deoxynivalenol on the Placental and Embryo on Gestation Day 12.5 d and 18.5 d

Deoxynivalenol (DON) is a kind of natural pollutant belonging to the trichothecenes family. The aim of this study is to use diverse assays to evaluate oxidative damage as well as translocation of nuclear factor erythroid 2-related factor 2 (Nrf2), and to investigate their mechanisms in DON-induced toxicities on a placenta and embryo. Pregnant C57BL/6 mice were randomly assigned to three groups with different doses of DON: 0, 1.0, 2.5 mg/(kg·day). In gestation day (GD) 12.5 d and 18.5 d, DON induced an elevated resorption rate of the embryos as well as structural and functional damage of the placenta. In the placenta, altered levels of the antioxidant enzymes malondialdehyde, superoxide dismutase and glutathione indicated remarkable oxidative stress. Furthermore, an elevated level of heme oxygenase-1 (HO-1) and the translocation of Nrf2 from nucleus to cytoplasm indicated Nrf2/HO-1 pathway activation in DON-L group (1.0 mg/(kg·day)). It is noteworthy that the results in this experiment in GD 12.5 d were similar to those in GD 18.5 d. In conclusion, DON-induced placental oxidative damage and Nrf2 translocation were similar in GD 12.5 d and GD 18.5 d. Oxidative stress is one of the most important molecular mechanisms for embryotoxicity induced by DON, and Nrf2 translocation may play a substantial role against it.

What Is Trophoblast? A Combination of Criteria Define Human First-Trimester Trophoblast

Controversy surrounds reports describing the derivation of human trophoblast cells from placentas and embryonic stem cells (ESC), partly due to the difficulty in identifying markers that define cells as belonging to the trophoblast lineage. We have selected criteria that are characteristic of primary first-trimester trophoblast: a set of protein markers, HLA class I profile, methylation of ELF5, and expression of microRNAs (miRNAs) from the chromosome 19 miRNA cluster (C19MC). We tested these criteria on cells previously reported to show some phenotypic characteristics of trophoblast: bone morphogenetic protein (BMP)-treated human ESC and 2102Ep, an embryonal carcinoma cell line. Both cell types only show some, but not all, of the four trophoblast criteria. Thus, BMP-treated human ESC have not fully differentiated to trophoblast. Our study identifies a robust panel, including both protein and non-protein-coding markers that, in combination, can be used to reliably define cells as characteristic of early trophoblast.

The diagnostic significance of hCG and hPL via immunohistochemistry of placental tissues in pregnancies diagnosed with IUGR and IUD

Placentas of patients diagnosed with intrauterine growth restriction (IUGR) and intrauterine death (IUD) were examined by immunohistochemistry for alpha-beta subunits of human chorionic gonadotropin (hCG) and human placental lactogen (hPL) antibodies, and compared with placentas from women with healthy pregnancies. In total, 114 subjects were evaluated. The patient group comprised 27 cases of IUGR and 57 of IUD, and the control group consisted of 30 women with normal pregnancies. Placental specimens were examined for primary antibodies using immunohistochemical techniques. Placentas from 22 cases of IUGR were stained positively for alpha-hCG. All 27 specimens obtained from this group were stained positively for beta-hCG and hPL. Among the cases of IUD, 44 placentas were stained positively for alpha-hCG, and all 57 specimens were stained positively for beta-hCG and hPL.

Syncytiotrophoblastic vesicles in placental intervillous space

OBJECTIVE

This study was undertaken to investigate the origin and function of vesicles found in the intervillous space.

STUDY DESIGN

A retrospective study was performed by using placental sections of different gestational ages. The number of vesicles was counted in each section of gestational age groups. Immunohistochemical staining for beta-human chorionic gonadotropin (beta-hCG) and human placental lactogen (hPL) was conducted to confirm the origin of vesicles.

RESULTS

Staining for beta-hCG and hPL was prominent in vesicles separating from syncytiotrophoblast into the intervillous space. The numbers of vesicles were not significantly different in gestational age groups of 42 to 30 weeks and all vesicles disappeared in 9- to 5-week groups. Large vesicles tended to show degeneration and disintegration in the intervillous space.

CONCLUSION

The vesicles containing beta-hCG and hPL suggest a different secretory mechanism of syncytiotrophoblast.

The placental site nodule: an immunohistochemical study

The placental site nodule and plaque (PSN-P) is a recently described, benign proliferation of intermediate trophoblast cells (ITs) in the endometrium or endocervix occurring after an intrauterine gestation. We performed an extensive immunohistochemical study of 11 cases of PSN-P. Cytokeratins (AE1/AE3 and MAK 6) were strongly positive in all cases stained. Epithelial membrane antigen (EMA) was positive in all cases, in 5% to 75% of lesional cells. Expression of human placental lactogen (hPL) was weak and focal, and a minority of cases were positive for human chorionic gonadotropin (hCG). More helpful in identifying the trophoblastic nature of the lesion was pregnancy-specific beta-1 glycoprotein (SP1), which was present in 100% of cases, and placental alkaline phosphatase (PLAP), present at least focally in 90% of cases stained. Vimentin was strongly positive in all cases stained. The presence of vimentin, SP1 and PLAP in PSN-P has not been documented previously. In our opinion cytokeratin, vimentin, and SP-1 are the most important monoclonal antibodies to aid in the differential diagnosis of PSN-P.

Ultrastructural localization of pregnancy-specific beta 1-glycoprotein (SP1) and cathepsin B in villi of early placenta of the macaque

Pregnancy-specific beta 1-glycoprotein (SP1) is found in maternal serum very early in gestation in both human and non-human primates. As judged by light microscopic immunocytochemistry, the major source of SP1 is the syncytial trophoblast, but little is known of the subcellular localization of SP1 indicative of the cellular pathway involved in secretion of the hormone. To study subcellular distribution of SP1, we used electron microscopic immunocytochemistry carried out on macaque placental villi from early (3-4 weeks) gestation. Both light and electron microscopic results confirmed localization confined to syncytial trophoblast in the villi. Within syncytial trophoblast labeling was predominantly over small granules in the apical cytoplasm. The Golgi complex also showed labeling, and light labeling was associated with the endoplasmic reticulum. For comparison, we also localized cathepsin B, a lysosomal protease. By way of contrast this enzyme was localized primarily in large cytoplasmic granules. The results are consistent with a secretory pathway including synthesis in the ER, processing by the Golgi complex, and exocytotic release into maternal blood in the intervillous space.

Placental protein distribution in maternal diabetes mellitus: an immunocytochemical study

Placentas associated with maternal diabetes are generally characterized by features of villous immaturity. We correlated the villous histology with the immunocytochemical distribution of four trophoblastic proteins: beta human chorionic gonadotropin (beta HCG), placental alkaline phosphatase (PLAP), pregnancy specific beta-1-glycoprotein (SP1), and human placental lactogen (HPL) in 14 third-trimester placentas associated with diabetes mellitus. Staining was increased for beta HCG and decreased for PLAP, SP1, and HPL in the diabetic placentas compared to control placentas of similar gestational age. This pattern was most prominent in areas of marked architectural villous immaturity within individual placentas and suggests concomitant functional immaturity.

Demonstration of the ability of Hofbauer cells to phagocytose exogenous antibodies

We have studied the effects of the anti-human chorionic gonadotropin and anti-human antithrombin III antibodies on Hofbauer cells from human immature placenta, when applied to either intact villi or on cell culture. Trypsin treatment of the villi results in a mixed cell culture mainly composed of isolated Hofbauer cells but which also contains a variable number of mesenchymal cells and a few syncytiotrophoblastic cells. In all samples analysed only 7-8% of the Hofbauer cells and some syncytiotrophoblastic cells exhibited a macrophagic activity 24 h after incubation of the cultures with the antisera. That only certain proportions of Hofbauer and syncytiotrophoblastic cells express macrophagic activity is also seen when intact villi are incubated for 24 h with these antibodies. Indeed, neither all the villi nor all these cells within a single villus are positively stained. The fact that only a fraction of Hofbauer cells and syncytiotrophoblast express a macrophagic activity may suggest that only some cells, amongst both these cell types, are involved in the protection of the fetus against maternal immunological rejection by removing immunological complexes.

Immunocytochemical identification of mitotic Hofbauer cells in cultures of first trimester human placental villi

In cultures of first trimester human placental villi, mitotic Hofbauer cells have been identified using a combined autoradiographic and immunostaining technique for the demonstration of HCG, a marker for Hofbauer cells.

Identification of human chorionic gonadotropin (HCG) secreting cells and other cell types using antibody to HCG and a new monoclonal antibody (mABlu-5) in cultures of human placental villi

We have identified cells which secrete human chorionic gonadotropin (HCG) of cultures if first trimester placental villi. As a first step, we identified epithelial cells using a new monoclonal antibody. We then added HCG antibodies to the cultured cells. We found that syncytiotrophoblast (and not cytotrophoblast), Hofbauer cells and some mesenchymal cells stained with HCG antibodies.