Choriocarcinoma cells increase the number of differentiating human cytotrophoblasts through an in vitro interaction

Review on new approach methods to gain insight into the feto-maternal interface physiology

Non-human animals represent a large and important feature in the history of biomedical research. The validity of their use, in terms of reproducible outcomes and translational confidence to the human situation, as well as ethical concerns surrounding that use, have been and remain controversial topics. Over the last 10 years, the communities developing microphysiological systems (MPS) have produced new approach method (NAMs) such as organoids and organs-on-a-chip. These alternative methodologies have shown indications of greater reliability and translatability than animal use in some areas, represent more humane substitutions for animals in these settings, and - with continued scientific effort - may change the conduct of basic research, clinical studies, safety testing, and drug development. Here, we present an introduction to these more human-relevant methodologies and suggest how a suite of pregnancy associated feto-maternal interface system-oriented NAMs may be integrated as reliable partial-/full animal replacements for investigators, significantly aid animal-/environmental welfare, and improve healthcare outcomes.

Differential glucocorticoid effects on proliferation and invasion of human trophoblast cell lines

Several clinical situations require continuous glucocorticoid (GC) treatment during pregnancy. A well-known deleterious side effect of such treatment is the higher incidence of growth-restricted fetuses, for which a too shallow trophoblast invasion is presently hypothesised as the underlying cause. This study investigated whether the synthetic GC triamcinolone acetonide (TA) influences proliferation, invasion and endocrine activity of human trophoblast. BeWo and JEG-3 choriocarcinoma cell lines both express GC receptors (western blotting) and were used as models for human trophoblast. JAR devoid cells of GC receptor were used as negative control. The cells were cultured for 48 h without (control) or with 0.5, 5 and 50 microM TA. In the presence and absence of serum, proliferation was determined by cell counting and measuring the cell cycle regulating protein cyclin B1 (Western blotting); invasion was determined by a conventional Matrigel invasion assay and by measuring the secretion (ELISA) of matrix-metalloproteinases (MMP-2, MMP-9) into the culture medium; endocrine activity was assessed by measuring the levels of human chorionic gonadotropin (ELISA) into the culture medium. TA altered the number of viable and dead cells as well as cyclin B1 levels and, to a lesser extent, invasion of BeWo and JEG-3, with a strong influence of serum. BeWo and JEG-3 cells reacted differently and in most instances reverse. In the cell lines used as models of human trophoblast, TA alter some functions relevant to proliferation and invasion, and suggest that caution should be exercised when treating women with GCs during pregnancy.

IL-1β Treatment Does not Co-ordinately Up-regulate mPGES-1 and COX-2 mRNA Expression, but Results in Higher Degree of Cellular and Intracellular Co-localization of their Immunoreactive Proteins in Human Placenta Trophoblast Cells

PGE2 is involved in initiation and progression of labor in many species. Biosynthesis of PGE2 is mediated by cyclooxygenases (COX) and prostaglandin E synthases (PGES). mPGES-1 and COX-2 form an inducible pathway for PGE2 production in many cell systems. In this study we investigated whether mPGES-1 is involved in cytokine induced PGE2 biosynthesis in human trophoblast cells. We have evaluated the cellular and intracellular co-localization of mPGES-1 and COX-2, as well as cPGES and COX-1 in human trophoblast cells by dual immunofluorescent staining. The effect of IL-1beta on mPGES-1 and COX-2 co-localization, such as would occur with infection, and the regulatory effects of pro-inflammatory cytokines IL-1beta and TNF-alpha on transcriptional activity of mPGES-1 and COX-2 in these cells were also studied. We found that in cultured unstimulated trophoblasts, some cells expressed predominantly either mPGES-1 or COX-2, though there were cells co-expressing both enzymes. With IL-1beta treatment, mPGES-1 and COX-2 became more consistently co-localized. mPGES-1 was not transcriptionally co-induced with COX-2 by the cytokine treatment. We conclude that mPGES-1 is not involved in the inducible COX-2 mediated pathway for PGE2 biosynthesis at the transcriptional level, however, the treatment with IL-1beta results in a higher degree of co-ordination of the mPGES-1 and COX-2 protein immunolocalization, eliciting PGE2 synthesis.

Cellular localization of the human chorionic gonadotropin beta-subunit in transgenic mouse placenta

CG is a human placental glycoprotein expressed in first-trimester trophoblasts. To examine the regulation of the CGbeta-subunit in an in vivo model, we previously constructed transgenic mice containing the CGbeta gene cluster and demonstrated its expression in the placenta. Here, we determine the cell type responsible for CGbeta synthesis in the mouse by immunohistochemical and in situ hybridization analyses. Unexpectedly, the protein and messenger RNA were not detected in trophoblast or elsewhere in the chorioallantoic placenta but in the parietal endoderm, a separate extraembryonic component of the placenta. The identity of this CGbeta-producing layer was confirmed by the presence of laminin A, a known protein of the parietal endoderm extracellular matrix. However, we observed heterogeneity, with respect to synthesis of laminin A and CGbeta; parietal endoderm cells expressing CGbeta at high levels synthesized less laminin A, and vice versa. The absence of CGbeta production in trophoblasts of the transgenic mouse demonstrates a lack of transcriptional equivalence between rodent and human trophoblasts. The data are consistent with the hypothesis that, in human placenta, one or more transcriptional factors coevolved as members of the CGbeta gene cluster underwent duplication.

Modulation by benzo[a]pyrene of epidermal growth factor receptors, cell proliferation, and secretion of human chorionic gonadotropin in human placental cell lines

Clinical observations indicate that maternal cigarette smoking has significant detrimental effects on fetoplacental development. The present study used human trophoblastic choriocarcinoma cell lines of placental origin to investigate the effects of benz[a]pyrene (BaP) on epidermal growth factor (EGF) receptors, cell proliferation and human chorionic gonadotropin (hCG) secretion. BaP decreased 125I-EGF binding and EGF receptor protein in a concentration-related manner in both BeWo and JEG-3 cell lines. The steady-state level of EGF receptor mRNA, however, was not changed significantly by BaP in either cell line. Cell proliferation was unchanged or slightly increased following exposure to 10 and 50 microM BaP in the presence of serum, whereas proliferation progressively decreased in cells exposed under serum-free conditions. The mitogenic effect of EGF was inhibited by cotreatment with BaP in both cell lines. Further study of trophoblast endocrine function showed that both basal and EGF-stimulated secretion of hCG was reduced significantly by BaP exposure in BeWo cells, whereas no adverse effect was seen in JEG-3 cells. Finally, cytochrome P450 1A1 (CYP1A1) was induced in a concentration-dependent manner by BaP in both cell lines. Thus, data indicate that the BaP-mediated loss of EGF receptors alters trophoblast proliferation and endocrine function, and that different mechanisms may be involved in the regulation of hCG secretion in BeWo and JEG-3 cells. In addition, this study supports the feasibility of using the BeWo and JEG-3 trophoblastic choriocarcinoma cell lines to investigate biomarkers and mechanisms of placental toxicity.

Developmental regulation of the expression of 72 and 92 kd type IV collagenases in human trophoblasts: a possible mechanism for control of trophoblast invasion

OBJECTIVE

During early pregnancy fetal cytotrophoblast cells invade the uterus and penetrate the basement membrane, a property that is characteristic of malignant cells. However, unlike tumor invasion, trophoblast invasion of the uterus is under strict control. This control limits invasion, so that it primarily remains confined to the endometrial aspect of the myometrium and continues only until midgestation. The invasive properties of the trophoblast cells are made possible by the activity of proteolytic enzymes that belong to the metalloproteinases and serine proteinases. Type IV collagenase (metalloproteinase) is considered crucial in the extracellular matrix remodeling that takes place during the invasion process. In this study we set out to characterize the invasive properties of trophoblast cells at different stages of pregnancy.

STUDY DESIGN

Human trophoblast cells were isolated from first- and third-trimester placentas by trypsin digestion and Percoll fractionation and were then cultured under serum-free conditions. The invasive ability of trophoblast cells was determined by the in vitro invasion assay, in which the ability of cells to penetrate an artificial basement membrane was examined. Metalloproteinase activity was measured by zymography, and the expression of messenger ribonucleic acid transcripts of 72 and 92 kd type IV collagenases was examined by reverse transcriptase polymerase chain reaction.

RESULTS

First-trimester trophoblasts were 3.5 time more invasive in vitro than were third-trimester trophoblast cells (p < 0.005). Although first-trimester trophoblasts secreted both species of type IV collagenase, 72 and 92 kd, in large amounts, third-trimester cells secreted the 92 kd and only minimal amounts of 72 kd type IV collagenase. Moreover, first-trimester trophoblasts secreted significantly more (p < 0.05) 92 kd type IV collagenase than did third-trimester trophoblast. The messenger ribonucleic acid transcript expression of 72 and 92 kd type IV collagenases correlated with the activity of these enzymes secreted by first- and third-trimester trophoblasts.

CONCLUSION

The described high in situ invasive capacity of first-trimester trophoblast might be explained by the increased expression and production of 72 kd type IV collagenase and the higher expression of 92 kd type IV collagenase by first-trimester trophoblast cells.

Regulation by interleukin-1 beta of growth and collagenase production by choriocarcinoma cells

Impaired trophoblastic invasion and proliferation have been implicated in the pathogenesis of eclampsia, pre-eclampsia, spontaneous abortions and intra-uterine growth retardation (IUGR). First trimester trophoblast cells (which do not grow in culture) and choriocarcinoma (BeWo) (which grow spontaneously, and are used as a model for proliferating trophoblast) were incubated with interleukin-1 beta (IL-1 beta). BeWo cell growth was decreased dose-dependently by exogenous IL-1 beta at concentrations of 100-1000 pg/ml. This effect was first detected after 24 h of incubation with IL-1 beta, and persisted for up to 96 h of culture. In contrast, trophoblast cells isolated from first trimester placental tissue showed no growth response when stimulated with IL-1 beta. The levels of active interstitial collagenase produced by BeWo cells were increased by IL-1 beta (100-1000 pg/ml), which paralleled the decrease in cell growth. First trimester trophoblast cells produced lower levels of collagenase and this was not affected by incubation of the cells by IL-1 beta. These results indicate that IL-1 beta may regulate placental development, but further development of culture systems for first trimester trophoblast will be needed before this result can be confirmed.

Interaction between choriocarcinoma cell line (JAr) and human cytotrophoblasts in vitro

Cytotrophoblasts (from term placentae) and cells from the choriocarcinoma cell line JAr were cultivated either separately or in co-culture for 72 h. RNA was isolated from the cell cultures and Northern blots were developed using equal amounts of RNA. The RNA was hybridized with cDNA probes for CG alpha, CG beta and hPL. Corresponding m-RNAs were detected in the three RNAs except for hPL m-RNA which was absent from JAr cells RNA. The abundance of CG alpha and CG beta m-RNA in the RNA of the co-culture was higher than their accumulative abundances in the RNAs from cytotrophoblasts and JAr cells cultured alone and the abundance of hPL m-RNA in the RNA of the co-cultures was as high as that in the RNA from cytotrophoblasts cultured alone. On the basis of previous findings (Hochberg et al, 1991), it can be assumed that the cytotrophoblasts in the co-cultures are responsible for the increase in hormonal m-RNA production. It could be calculated that the abundances of the CG alpha, CG beta and hPL m-RNAs in the RNA which originated in the cytotrophoblast nuclei were 20, 100 and 10-fold higher respectively in the co-culture compared to those in the culture of cytotrophoblasts. This effect is limited to certain genes only as the concentration of the 92kD collagenase m-RNA and uPA (urokinase type plasminogen activator) m-RNA, which are both produced in cytotrophoblasts to a much higher extent than in JAr cells, and are not increased by cultivating the cytotrophoblasts with JAr cells in co-culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Human macrophage colony-stimulating factor induces the differentiation of trophoblast

When human cytotrophoblastic cells in the early stage of pregnancy were cultured in a serum-free medium in the presence of human macrophage colony-stimulating factor (M-CSF), the cytotrophoblastic cells fused and formed a typical syncytiotrophoblast which had a dense distribution of microvilli revealed under an electron microscope. On the other hand, cytotrophoblasts incubated with anti-M-CSF antibody showed hardly any syncytiotrophoblast formation. Following this finding, we studied the differentiation of chorionic cells from the viewpoint of hormone secretion. When cytotrophoblasts were incubated in the presence of M-CSF, the supernatant of the culture showed an increase in human chorionic gonadotropin and human placental lactogen levels in proportion to the concentration of M-CSF added. When cytotrophoblasts were incubated in the presence of anti-M-CSF antibody or anti-fms antibody, human chorionic gonadotropin and human placental lactogen secretion were suppressed. Thus, M-CSF was morphologically and endocrinologically found to induce the differentiation of chorionic cells.

Transcription of the H19 gene in differentiating cytotrophoblasts from human placenta

Placental differentiation is closely correlated with the appearance of specific proteins, yet factors regulating cytotrophoblast differentiation are unknown. One strategy employed to search for such factors makes use of differential screening of cDNA libraries. For this purpose, cytotrophoblasts were isolated from human term placentae and cultured for 24 and 120 hr. cDNA libraries were constructed from the cell's RNA, and differential screening resulted in the isolation of three identical clones highly expressed after 120 hr. A DNA sequencing of 139 bp at the 3' end of these clones and a search of the data bank revealed that the sequence was identical to the parallel domain in the human H19 gene. This highly conserved gene is unusual in that it may not encode a protein. In the mouse, its RNA was shown to accumulate to high levels in embryonic tissues of endodermal and mesodermal origin. Our present findings imply that, in humans, the H19 gene is efficiently expressed in placental tissue and differentiated cytotrophoblasts, which are of ectodermal origin. RNA blot hybridization revealed a unique bimodal pattern of expression for the H19 gene in cultured cytotrophoblasts. The modulation in expression of H19 during cytotrophoblast growth was not due to the increase in the number of multinuclear cells. Size fractionation of cytotrophoblasts by centrifugal elutriation revealed that H19 expression is correlated with the stage of cell differentiation. We therefore propose that H19 transcripts might play a regulatory role in the process of cytotrophoblast differentiation.