Bovine trophoblastic cell differentiation on collagen substrata: formation of binucleate cells expressing placental lactogen

In vitro regulation of gene expression of pregnancy-associated proteins and cytokines in bovine endometrial epithelial cells and bovine trophoblastic cells by infection with Neospora caninum

Abortion caused by the parasite Neospora caninum is an important threat to the livestock industry worldwide. Trophoblasts and caruncular cells play major roles in initiating innate immune responses and controlling parasite infection at the fetal-maternal interface. In the present study, bovine uterine epithelial cells (BUECs) and bovine trophoblastic (BT) cells treated with bovine interferon-gamma (IFN-γ), IFN-alpha (IFN-α) and IFN-tau (IFN-τ) followed by infection with N. caninum were examined by measuring the mRNA expression levels of numerous pregnancy-associated proteins and observing parasite growth to elucidate the host-parasite interaction at the uteroplacental region. N. caninum infection increased the expression of prolactin-related protein 1 (PRP1), pregnancy-associated glycoprotein 1 (PAG1), and cytokines (TNF-α, IL-8 and IL-10) in BUECs and of IL-8 in BT cells. Bovine IFN-γ inhibited IL-8 and TNF-α expression in BUECs and IL-8 in BT cells. In contrast, the expression of the interferon-stimulated gene OAS1 was significantly increased by treatment of the infected BT cells with IFN-γ. However, treatment with bovine IFNs did not inhibit N. caninum growth in either cell line. In conclusion, our results suggest that bovine IFN-γ plays a crucial role in control of pathogenesis in uterus and induction of inflammatory response in the placental region following N. caninum infection, rather than growth inhibition of the parasites.

Ovine Trophoblast Cells: Cell Isolation and Culturing from the Placenta at the Early Stage of Pregnancy

Embryo development is dependent upon the exchange of oxygen and nutrients through the placenta, mainly composed of peculiar epithelioid cells, known as trophoblast cells. Normal trophoblast functionality plays a key role during the whole pregnancy, especially in the first stage of placentation. This chapter explains the techniques to obtain sheep primary trophoblast cells from the early placenta. Overall, procedures for cell isolation, culture, characterization, and cryopreservation are described.

Expression of cadherins and some connective tissue components in cow uterus and placenta during pregnancy

The implantation and placental development processes are regulated with cell adhesion molecules and remodeling of the maternal endometrium's extracellular matrices (ECM) and fetal chorion. This study aimed to investigate the distribution and localization of some classical cadherins (E-, N-, and P-cadherins) and extracellular matrix components collagen type 5α1, fibronectin, and laminin in the cow placentomes during pregnancy using immunohistochemical and Western blotting analyses. The study results confirmed the expression of E- and P-cadherins, collagen type Vα1 (COLVα1), fibronectin, and laminin in the cow placentomes, but not N-cadherin. Throughout the pregnancy, E- and P- cadherins, COLVα1, and laminin were localized in the luminal and glandular epithelium of the inter-caruncular endometrium, caruncular epithelium, and the uninucleate (UNCs) and binucleate trophoblast giant cells (BNCs/TGCs). E- cadherin immunoreactivity in the first pregnancy period was strong in the UNCs while moderate in the BNCs/TGCs. However, it was weak in both trophoblast in the second and third pregnancy periods. In the fetal trophoblasts, P- cadherin and laminin immunostainings were more intense in the BNCs/TGCs than UNCs. The fetal and maternal stromal cells were also positive for P- cadherin, COLVα1, fibronectin, and laminin. The immunostaining intensity of COLVα1 and fibronectin in the stromal extracellular matrix of the placentomes decreased as the pregnancy progressed. The endothelia of fetal and maternal vessels were positive for all proteins. The presence and distinct localization of cadherins and ECM proteins in the cow placentome components support the role of these molecules in regulating placental cell growth, migration, and matrix production during pregnancy.

Modeling the Ruminant Placenta-Pathogen Interactions in Apicomplexan Parasites: Current and Future Perspectives

Neospora caninum and Toxoplasma gondii are one of the main concerns of the livestock sector as they cause important economic losses in ruminants due to the reproductive failure. It is well-known that the interaction of these parasites with the placenta determines the course of infection, leading to fetal death or parasite transmission to the offspring. However, to advance the development of effective vaccines and treatments, there are still important gaps on knowledge on the placental host-parasite interactions that need to be addressed. Ruminant animal models are still an indispensable tool for providing a global view of the pathogenesis, lesions, and immune responses, but their utilization embraces important economic and ethics restrictions. Alternative in vitro systems based on caruncular and trophoblast cells, the key cellular components of placentomes, have emerged in the last years, but their use can only offer a partial view of the processes triggered after infection as they cannot mimic the complex placental architecture and neglect the activity of resident immune cells. These drawbacks could be solved using placental explants, broadly employed in human medicine, and able to preserve its cellular architecture and function. Despite the availability of such materials is constrained by their short shelf-life, the development of adequate cryopreservation protocols could expand their use for research purposes. Herein, we review and discuss existing (and potential) in vivo, in vitro, and ex vivo ruminant placental models that have proven useful to unravel the pathogenic mechanisms and the host immune responses responsible for fetal death (or protection) caused by neosporosis and toxoplasmosis.

Characterisation of bovine embryos following prolonged culture in embryonic stem cell medium containing leukaemia inhibitory factor

In order to help elucidate the process of epiblast and trophoblast cell differentiation in bovine embryos invitro, we attempted to develop a suitable culture medium to allow extended embryo culture. Day 7 bovine blastocysts developed in conventional medium were cultured further in embryonic stem cell medium with or without leukaemia inhibitory factor (LIF) until Day 23. At Day 14, the expression of octamer-binding transcription factor 3/4 (OCT3/4) and VIMENTIN was significantly higher in embryos cultured with than without LIF, but embryonic disc formation was not observed. Although expression of SRY (sex determining region Y)-box 17 (SOX17) mRNA was significantly lower in Day 14 embryos cultured with and without LIF than in invivo embryos, hypoblast cells formed just inside the trophoblast cells of the invitro-cultured embryos. On Day 23, expression of placental lactogen (PL) and prolactin-related protein 1 (PRP1) was not affected by LIF in invitro-cultured embryos, levels of both genes were significantly lower in the invitro than invivo embryos. Similar to invivo embryos, binucleate cell clusters seen in Day 23invitro-cultured embryos were composed of PL-negative and -positive cells. These results suggest that our culture system partially reproduced the differentiation process of trophoblast cells invivo.

Adhesion molecules in gamete transport, fertilization, early embryonic development, and implantation-role in establishing a pregnancy in cattle: A review

Cell-cell adhesion molecules have critically important roles in the early events of reproduction including gamete transport, sperm-oocyte interaction, embryonic development, and implantation. Major adhesion molecules involved in reproduction include cadherins, integrins, and disintegrin and metalloprotease domain-containing (ADAM) proteins. ADAMs on the surface of sperm adhere to integrins on the oocyte in the initial stages of sperm-oocyte interaction and fusion. Cadherins act in early embryos to organize the inner cell mass and trophectoderm. The trophoblast and uterine endometrial epithelium variously express cadherins, integrins, trophinin, and selectin, which achieve apposition and attachment between the elongating conceptus and uterine epithelium before implantation. An overview of the major cell-cell adhesion molecules is presented and this is followed by examples of how adhesion molecules help shape early reproductive events. The argument is made that a deeper understanding of adhesion molecules and reproduction will inform new strategies that improve embryo survival and increase the efficiency of natural mating and assisted breeding in cattle.

Derivation of Induced Trophoblast Cell Lines in Cattle by Doxycycline-Inducible piggyBac Vectors

Trophectoderm lineage specification is one of the earliest differentiation events in mammalian development. The trophoblast lineage, which is derived from the trophectoderm, mediates implantation and placental formation. However, the processes involved in trophoblastic differentiation and placental formation in cattle remain unclear due to interspecies differences when compared with other model systems and the small repertoire of available trophoblast cell lines. Here, we describe the generation of trophoblast cell lines (biTBCs) from bovine amnion-derived cells (bADCs) using an induced pluripotent stem cell technique. bADCs were introduced with piggyBac vectors containing doxycycline (Dox)-inducible transcription factors (Oct3⁄4(POU5F1), Sox2, Klf4, and c-Myc). Colonies that appeared showed a flattened epithelial-like morphology similar to cobblestones, had a more definite cell boundary between cells, and frequently formed balloon-like spheroids similar to trophoblastic vesicles (TVs). biTBCs were propagated for over 60 passages and expressed trophoblast-related (CDX2, ELF5, ERRβ, and IFN-τ) and pluripotency-related genes (endogenous OCT3/4, SOX2, KLF4, and c-MYC). Furthermore, when biTBCs were induced to differentiate by removing Dox from culture, they formed binucleate cells and began to express pregnancy-related genes (PL, PRP1, and PAG1). This is the first report demonstrating that the induction of pluripotency in bovine amniotic cells allows the generation of trophoblastic cell lines that possess trophoblast stem cell-like characteristics and have the potential to differentiate into the extra-embryonic cell lineage. These cell lines can be a new cell source as a model for studying trophoblast cell lineages and implantation processes in cattle.

The bovine placenta in vivo and in vitro

The gross anatomic features (cotyledonary type) and histologic classification (synepitheliochorial) of the bovine placenta have been known for many years. Thorough ultrastructural analysis as well as a variety of descriptive studies dealing with the localization of cytoskeletal filaments, extracellular matrix, growth factor systems, steroid hormone receptors, and major histocompatibility complex have contributed further significant knowledge. However, this knowledge was not sufficient to solve clinical placenta-based problems, such as retained fetal membranes. Owing to the complexity of the fetomaternal interface in vitro, culture systems have been developed. As trophoblast giant cells (TGC) are thought to be key players in the cattle placenta, most cell culture models attempt to overcome the pitfall of losing the entire TGC population in vitro. Nevertheless, distinct cell line-based in vitro systems such as cell monolayers or 3-dimensional (co-culture) spheroids were generated for the fetal (trophoblast) and maternal (uterine epithelium) placental compartments. Monolayers have been used to study for example, growth factor or hormonal signaling and TGC formation, whereas spheroids served as models for, for example, trophoblast attachment, uterine epithelium depolarization, and also TGC formation. In the future, the use of more improved culture models might lead to better treatments of retained fetal membranes and increased prevention of embryonic loss. In addition, the in vitro models could shed more light on the mechanisms of the differentiation of uninucleate trophoblast into TGC.

SOLD1 is expressed in bovine trophoblast cell lines and regulates cell invasiveness

BACKGROUND

Secreted protein of Ly-6 domain 1 (SOLD1), a secretory-type member of the Ly-6 superfamily, is expressed in both fetal and maternal tissues throughout gestation. SOLD1 mRNA is expressed in the endometrium and in trophoblast mononucleate and binucleate cells, suggesting it plays an important role not only in placental architecture at early gestation, but also in remodeling the endometrium at late gestation. Here, we investigate the expression of SOLD1 mRNA and protein in trophoblast cell lines. In addition, we examine the effect of SOLD1 on the invasive ability of trophoblast cells.

METHODS

We measured SOLD1 gene expression in thirteen bovine trophoblast (BT) cell lines by using quantitative reverse transcription PCR (qRT-PCR). SOLD1 protein levels were examined in two cell lines, BT-C and BT-K, by using Western blotting and immunocytochemistry. In addition, we measured the invasive activity of BT cells in the presence or absence of anti-bovine SOLD1 antibodies.

RESULTS

At variable levels, SOLD1 was expressed in all thirteen cell lines; however, expression remained below that of proximal fetal membrane tissue. SOLD1 protein, which was approximately 28 kDa in size, was detected in perinuclear area of the cytoplasm in BT cells. Treatment with anti-bovine SOLD1 antibody had a dose-dependent suppressive effect on the invasiveness of BT-K cell lines.

CONCLUSIONS

The present study is the first to investigate SOLD1 expression in vitro, in trophoblastic cell lines. Our data suggested that SOLD1 is involved in the regulation of the trophoblast invasiveness. Therefore, SOLD1 may play an active and crucial role in mediating communication at the fetomaternal interface.

An efficient system to establish biopsy-derived trophoblastic cell lines from bovine embryos

Trophoblastic cells play a crucial role in implantation and placentogenesis and can be used as a model to provide substantial information on the peri-implantation period. Unfortunately, there are few cell lines for this purpose in cattle because of the difficulty of raising successive cell stocks in the long-term. Our results show that the combination of a monolayer culture system in microdrops on a surface treated with gelatin and the employment of conditioned media from mouse embryonic fibroblasts support the growth of bovine trophoblastic cells lines from an embryo biopsy. Expression profiles of mononucleate- and binucleate-specific genes in established trophoblastic cells lines represented various stages of gestation. Moreover, the ability to expand trophoblastic cell lines for more than 2 yr together with pluripotency-related gene expression patterns revealed certain self-renewal capacity. In summary, we have developed a system to expand in vitro trophoblastic cells from an embryo biopsy that solves the limitations of using amplified DNA from a small number of cells for bovine embryo genotyping and epigenotyping and, on the other hand, facilitates the establishment of trophoblastic cell lines that can be useful as peri-implantation in vitro models.

Massive deregulation of miRNAs from nuclear reprogramming errors during trophoblast differentiation for placentogenesis in cloned pregnancy

Background

Low efficiency of Somatic Cell Nuclear Transfer (NT) has been widely addressed with high incidence of placental abnormalities due to genetic and epigenetic modifications. MiRNAs are shown to be major regulators of such modifications. The present study has been carried out to identify the expression patterns of 377 miRNAs, their functional associations and mechanism of regulation in bovine placentas derived from artificial insemination (AI), in vitro production (IVP) and NT pregnancies.

Results

This study reveals a massive deregulation of miRNAs as chromosomal cluster or miRNA families without sex-linkage in NT and in-vitro derived IVP placentas. Cell specific localization miRNAs in blastocysts and expression profiling of embryos and placentas at different developmental stages identified that the major deregulation of miRNAs exhibited in placentas at day 50 of pregnancies is found to be less dependent on global DNA methylation, rather than on aberrant miRNA biogenesis molecules. Among them, aberrant AGO2 expression due to hypermethylation of its promoter was evident. Along with other factors, aberrant AGO2 expression was observed to be associated with multiple defects in trophoblast differentiation through deregulation of miRNAs mediated mechanisms.

Conclusion

These aberrant miRNA activities might be associated with genetic and epigenetic modifications in abnormal placentogenesis due to maldifferentiation of early trophoblast cell lineage in NT and IVP pregnancies. This study provides the first insight into genome wide miRNA expression, their role in regulation of trophoblast differentiation as well as abnormal placental development in Somatic Cell Nuclear Transfer pregnancies to pave the way to improve the efficiency of cloning by nuclear transfer.

Bovine trophoblastic cell differentiation and binucleation involves enhanced endogenous retrovirus element expression

BACKGROUND

Endogenous retrovirus (ERV) envelope (env) genes are involved in the differentiation of trophoblastic cells in humans and mice. However, there is limited information about their roles in ruminant trophoblastic cells. Thus, we attempted to explore the possible roles of ERV elements in the binucleation of bovine trophoblastic cells using in vitro bovine trophoblastic (BT) cell lines.

METHODS

In this study, blastocysts and elongated embryos were obtained from Japanese Black cows, and endometrial and fetal membrane tissues were collected from day 17 to 37 of gestation. The gene expression levels of four ERV elements, bERVE (bovine endogenous retrovirus envelope element-like transcript) -A, bERVE-B, BERV (bovine endogenous retrovirus) -K1 env, and BERV-K2 env, were analyzed in the fetal and endometrial tissue and cultured BT cell lines using quantitative RT-PCR. On-Matrigel gel and on-collagen gel culturing were used to induce binucleate cell (BNC) formation in the BT cell lines. How the culture conditions affected the expression of BNC-specific genes and ERV elements was examined by quantitative RT-PCR and immunocytochemistry.

RESULTS

bERVE-A, bERVE-B, BERV-K1 env, and BERV-K2 env were expressed in almost all BT cell lines; however, only bERVE-A and BERV-K1 env were detected in trophoblastic tissues during the peri-implantation period. In the on-Matrigel cultures, the expression levels of BNC-specific genes and molecules were enhanced in the BT cells. The expression levels of bERVE-A and BERV-K1 env were also increased in the BT cells during on-Matrigel culturing. The BT cell expression levels of these ERV elements were consistent with those of BNC-specific genes during on-Matrigel culturing (P < 0.01).

CONCLUSIONS

These results suggest that bERVE-A and BERV-K1 env are involved in the expression of BNC-specific genes and the progression of bovine trophoblastic cell binucleation, as their expression levels increased during periods of increased BNC-specific molecule expression, which is strongly suggestive of the development of BNC from mononucleate trophoblastic cells. The on-Matrigel culture system is a convenient in vitro tool for studying bovine trophoblastic cell lineages.

Delivery of AP-2α siRNA into cultured bovine trophoblast cells by electroporation repressed key placenta-specific gene expression

Binucleate trophoblast giant cells (BNC) characteristically appear early in gestation in the bovine placenta. They secret pivotal hormones and cytokines for feto-maternal communication, for example, expression of placental lactogens (CSH1), prolactin-related protein 1 (PRP1) and pregnancy-associated glycoprotein 1 (PAG1) are necessary for pregnancy establishment in bovine. These genes transcription are regulated in a temporal and spatial manner, however, molecular mechanisms by which these gene transcriptions are regulated in this manner have not been firmly elucidated. In this study, a cell culture model for bovine trophoblast cells was initially established, small interfering RNA duplexes against Activator Protein-2α (TFAP2A) was transfected into the cells by electroporation, and transcripts of CSH1, PRP1 and PAG1 were measured by qPCR. The results showed that trophoblast giant cells were confluent for 90% after cultured for 10 days, and BNC constituted of a population of more than 45% of the total cells. Using a fluorescein-labeled non-silencing siRNA duplex, an electroporation protocol yielding routinely >93% positive cells could be established, and siRNA duplex transfection demonstrated an efficient knockdown of cellular AP-2α mRNA level by 72.30 ± 3.28% in electroporated cells. Finally, CSH1, PRP1 and PAG1 genes expression were effectively down-regulated by 65.45 ± 6.38% (P<0.01), 40.73±11.72% (P<0.01) and 11.59 ± 1.88% (P<0.05), respectively. It was therefore suggested that electroporating siRNA into bovine trophoblast cells could be an efficient method to manipulate BNC function and to study the regulation mechanism of specific gene transcription without the use of chemical transfection reagents. It was suggested that AP-2α could be at least involved in the regulation of expression CSH1 and PRP1 transcripts.

Trophoblast development

This review summarises current knowledge about the specification, commitment and maintenance of the trophoblast lineage in mice and cattle. Results from gene expression studies, in vivo loss-of-function models and in vitro systems using trophoblast and embryonic stem cells have been assimilated into a model seeking to explain trophoblast ontogeny via gene regulatory networks. While trophoblast differentiation is quite distinct between cattle and mice, as would be expected from their different modes of implantation, recent studies have demonstrated that differences arise much earlier during trophoblast development.

Bone morphogenetic protein 4 accelerates the establishment of bovine trophoblastic cell lines

Trophoblastic cells play a crucial role in implantation and placentogenesis. A large proportion of the failures of conception in cows occur in the peri-implantation period, which are known as early embryo losses. In exploring this critical phenomenon, trophoblastic cell lines can provide substantial information. Unfortunately, there are few cell lines for this purpose in cattle because of the difficulty of raising successive cell stock in the long term. In this study, 12 new cell lines were established using bone morphogenetic protein 4 (BMP4). BMP4 stimulated embryonic cells to enter the trophoblastic cell lineage but there were no significant differences between intact and BMP4-treated groups. Only one out of 49 embryos developed trophoblastic cells in the intact group. Finally, 12 cell lines were maintained for around 30 passages, and they retained trophoblastic characteristics and expressed bovine trophoblastic genes: placental lactogen, interferon-τ, pregnancy-associated glycoprotein 1, and prolactin-related protein 1. Although the gene expression patterns were different among cell lines and depended on the cells, there was no significant relationship between the expression intensities of genes and the treatment dose of BMP4. All of them expressed bovine POU domain class 5 transcription factor 1 and caudal-type homeobox 2. The expression of these genes was confirmed by quantitative RT-PCR and immunohistochemical detection. These results suggest that BMP4 is involved in the raising of trophoblast cell lines from early embryonic cells and the newly developed cell lines can provide different types of bovine trophoblastic cells with different cell lineages. This may constitute a significant new tool for the examination of trophoblastic differentiation.

Formation of bovine placental trophoblast spheroids

INTRODUCTION

In this study, we aimed to form spheroids with the bovine placental trophoblast cell line F3. Spheroids are 3-dimensional culture models which can be used to conduct versatile in vitro and in vivo experiments.

MATERIALS AND METHODS

The spheroids were generated using the hanging drop technique, 25% methocel and matrigel. The F3 spheroids were characterized morphologically by light microscopy and transmission (TEM) and scanning electron microscopy (SEM) and immunohistochemistry (ezrin, vimentin, cytokeratin, placental lactogen). The fluorescent dyes calcein and ethidium homodimer were used to determine the viability of the spheroidal F3 cells by immunofluorescence microscopy.

RESULTS

The cell line F3 only formed spheroids by the hanging drop technique when matrigel was added. The trophoblast spheroids were delimited and fully covered by extracellular matrix (light microscopy/TEM/SEM). Cells contributing to spheroids could not be discriminated from each other (light microscopy). The outer spheroidal layer consisted of cells which possessed an apical pole with microvilli that were directed to the outside (light microscopy/TEM). All of the spheroidal F3 cells expressed ezrin, vimentin and cytokeratin, but not placental lactogen. The spheroid core contained degenerating cells whilst the F3 cells of the outer rim were viable (TEM/immunofluorescence microscopy).

DISCUSSION

We have established a 3-dimensional spheroid model for the bovine placental trophoblast cell line F3. The developed culture model might prove valuable for future in vitro studies on the differentiation of bovine trophoblast cells.

The characterization of DNA methylation-mediated regulation of bovine placental lactogen and bovine prolactin-related protein-1 genes

Background

Bovine trophoblast binucleate cells (BNC) express a plethora of molecules including bovine placental lactogen (bPL, gene name is bCSH1) and bovine prolactin-related protein-1 (bPRP1). BCSH1 and bPRP1 are members of the growth hormone (GH)/prolactin (PRL) gene family, which are expressed simultaneously in BNC and are central to placentation and the progression of pregnancy in cattle. However, there is a paucity of information on the transcriptional regulatory mechanisms of both the bCSH1 and bPRP1 genes. Recent studies, however, have demonstrated that the expression of a number of genes is controlled by the methylation status of their promoter region. In the present study, we examined the cell-type-specific epigenetic alterations of the 5'-flanking region of the bCSH1 and bPRP1 genes to gain an insight into their regulatory mechanisms.

Results

Analysis of 5-aza-2'-deoxycytidine treatment demonstrated that bCSH1 expression is moderately induced in fibroblast cultures but enhanced in BT-1 cells. Sodium bisulfite based sequencing revealed that bCSH1 is hypomethylated in the cotyledonary tissue but not in the fetal skin, and this pattern was not altered with the progression of pregnancy. On the other hand, the methylation status of bPRP1 was similar between the cotyledon and fetal skin. The bPRP1 gene was exclusively hypermethylated in a bovine trophoblast cell-derived BT-1 cell-line. While the activity of bCSH1 was similar in both BT-1 and bovine fibroblast cells, that of bPRP1 was specific to BT-1. Treatment with a demethylating agent and luciferase assays provided in vitro evidence of the positive regulation of bCSH1 but not bPRP1.

Conclusion

This is the first report to identify the differential regulatory mechanisms of the bCSH1 and bPRP1 genes and indicates that bCSH1 might potentially be the only transcript that is subject to DNA methyltransferase regulation. The data indicates the possibility of novel kinetics of induction of the synchronously expressed BNC-specific bCSH1 and bPRP1 transcripts, which may aid the understanding of the intricate regulation and specific role(s) of these important molecules in bovine placentogenesis and the progression of pregnancy.

Native and recombinant bovine placental lactogens

The bovine placenta produces a wide variety of proteins that are structurally and functionally similar to the pituitary proteins from the GH/PRL gene family. Bovine placental lactogen (bPL) is a 200-amino acid long glycoprotein hormone that exhibits both lactogenic and somatogenic properties. The apparent molecular masses of purified native (n) bPL molecules (31-33 kDa) exceed 23 041 Da, which is the theoretical molecular mass of the protein core. At least six isoelectric variants (pI: 4.85-6.3) of bPL were described in cotyledonary extracts and three different bPL isoforms (pI: 4.85-5.25) were found in fetal sera. The bPL molecules that are detected in higher concentrations in peripheral circulation exhibit a more acidic pI than those present in placental homogenates. This may reflect an important glycosylation process occurring just prior to the bPL secretion. The bPL mRNA is transcribed in trophectoderm binucleate cells starting from Day 30 of pregnancy until the end of gestation. In mothers, bPL is involved in the regulation of ovarian function, mammogenesis, lactogenesis, and pregnancy stage-dependent adaptation of nutrient supplies to the fetus. Due to the higher fetal, compared to maternal concentrations of circulating hormone, it has been suggested that bPL primarily targets fetal tissues.

Comparison of the interferon-tau expression from primary trophectoderm outgrowths derived from IVP, NT, and parthenogenote bovine blastocysts

The expression of interferon-tau (IFN-tau) is essential for bovine embryo survival in the uterus. An evaluation of IFN-tau production from somatic cell nuclear transfer (NT)-embryo-derived primary trophectoderm cultures in comparison to trophectoderm cultured from parthenogenote (P) and in vitro matured, fertilized, and cultured (IVP) bovine embryos was performed. In Experiment 1, the success/failure ratio for primary trophectoderm colony formation was similar for IVP and NT blastocysts [IVP = 155/29 (84%); NT 104/25 (81%)], but was decreased (P = .05) for P blastocysts [54/43 (56%)]. Most trophectoderm colonies reached diameters of at least 1 cm within 3-4 weeks, and at this time, 72 hr conditioned cell culture medium was measured for IFN-tau concentration by antiviral activity assay. The amount of IFN-tau produced by IVP-outgrowths [4311 IU/mL (n = 155)] was greater (P < .05) than that from NT- [626 IU/mL (n = 104)] and P - [1595 IU/mL (n = 54)] derived trophectoderm. Differential expression of IFN-tau was confirmed by immunoblotting. In Experiment 2, colony formation was again similar for IVP and NT blastocysts [IVP = 70/5 (93%); NT 67/1 (99%)] and less (P < .05) for P blastocysts [65/27 (70%)]. Analysis of trophectoderm colony size after 23 days in culture showed a similar relationship with P-derived colonies being significantly smaller in comparison to IVP and NT colonies. A differential expression of IFN-tau was also observed again, but this time as measured over time in culture. Maximal IFN-tau production was found at day-14 of primary culture and diminished to a minimum by the 23rd day.

Genome multiplication is a generalised phenomenon in placentomal and interplacentomal trophoblast giant cells in cattle

The frequency of polyploidisation in bovine binucleate trophoblast giant cells (TGC) from placentomes (PL) and the interplacentomal allantochorion (AL) of six male fetuses with a crown-rump length between 3.5 and 103 cm was determined by in situ hybridisation with a chromosome-7-specific probe, using a probe specific for the Y chromosome to distinguish between maternal and fetal nuclei. The results showed that polyploid nuclei were essentially always of fetal origin. The frequency of tetraploid nuclei varied between 3% and 15% in both the placentomal and interplacentomal samples, with mean frequencies of 8.8% and 10.0% respectively. Octoploid nuclei were observed with a mean frequency of 1.1% in the interplacentomal samples, but were absent in samples from placentomes. Subsequent determination of nuclear DNA content by cytophotometric measurement of Feulgen-stained nuclei revealed that the frequency of nuclei with an 8C DNA content was several fold higher (AL 5.4%; PL 7.8%) than the frequency of octoploidy, suggesting that tetraploid TGC cells are arrested in the G2 phase of the cell cycle.

Analysis of uteroplacental-specific molecules and their functions during implantation and placentation in the bovine

In cattle, the mechanisms underlying implantation and placental development are still unclear. Synepitheliochorial placentation in cattle is noninvasive, and thus generates limited interest in terms of degradation and remodeling of endometrial tissues. The overall purpose of this study was three-fold: (1) to examine the gene circuitry around the implantation window, (2) to understand development of the placenta during the peri-implantation period by using a uteroplacental cDNA microarray, and (3) to study the roles of molecules involved in endometrial remodeling. Bovine trophoblastic binucleate cell-specific molecules, such as pregnancy-associated glycoproteins (PAGs), placental lactogen (PL), and prolactin-related proteins (PRPs), were markedly expressed in binucleate cells (BNCs) around implantation. The expression of PRP-1 was specific to the caruncular (CAR) area of the gravid uterine horn. Gelatinases (MMP-2 and -9) in association with heparanase may be central to endometrial remodeling. In situ hybridization analyses of PAGs, PRPs, PL, and heparanase suggested that BNCs expressed these molecules simultaneously. Future studies will further investigate the specific roles of these molecules in placentogenesis. The uteroplacental cDNA microarray presented cascades of molecular signatures not only for the endometrium but also for the intricate dialogue at the level of the feto-maternal interface in cattle. Placentome morphogenesis potentially parallels the dynamic multigenic circuitry and regulates the cell cycle in the endometrium. The roles of BNCs and their secreted molecules remain an enigma, particularly with regard to the adhesion process and endometrial remodeling, which is the focus of this study.

Culture of mature trophoblastic giant cells from bovine placentomes

The mostly binucleate trophoblast giant cells (TGC) found in bovine placentomes, in addition to synthesizing and releasing hormones play an important role in fetal development and maternal adaptation to pregnancy. Placentomes from early gestation were collected, and for isolation of mature TGC, three cellular disaggregation methods, mechanical (MECH), enzymatic by trypsin (TRYP) or collagenase (COLL) were compared to each other. Further on, the cell survival in culture medium (DMEM) supplemented with either 10% fetal calf serum (FCS) or 10% serum replacement (SR) on culture plates free of any substrate was evaluated over a period of 90 days by trypan blue exclusion. The cells were further characterized by HOECHST 33342 nuclear staining, and immunocytochemical staining with monoclonal antibodies against vimentin and cytokeratin. A mean total rate of TGC survival of 82.56% was recorded. Statistical analysis showed significantly higher survival rates after enzymatic disaggregation with COLL (86.23%) than following MECH (80.38%) or TRYP (80.91%) treatment. Supplementation of DMEM with FCS resulted in significantly higher cellular survival rates (87.13%) when compared to the addition of SR (77.73%). Analysis of the influence of both, disaggregation method and medium supplementation on TGC survival revealed statistically significant differences between the following groups: MECH-SR (71.09%) was significantly lower than all other groups; TRYP-SR (78.03%) was significantly different from all other groups; TRYP-FCS (83.43%) and COLL-SR (84.08%) were significantly lower than MECH-FCS (89.98%) which together with COLL-FCS (88.25%) showed the highest cellular survival rate. In summary, our results show that TGC isolated from early gestation placentomes may be viable for more than 90 days of culture. However, whether these TGC produce placental lactogen throughout this period has yet to be determined.

Establishment of a bovine blastocyst-derived cell line collection for the comparative analysis of embryos created in vivo and by in vitro fertilization, somatic cell nuclear transfer, or parthenogenetic activation

Tools and methods for analyzing differences in embryos resulting from somatic cell nuclear transfer (NT) in comparison to those derived from normal fertilization are needed to define better the nature of the nuclear reprogramming that occurs after NT. To this end, a collection of bovine blastocyst-derived cell lines was created. In vitro expanded or hatched blastocysts, used as primary culture tissue, were from NT; in vitro maturation, fertilization, and culture (IVF); or parthenogenetic (P) activation. Also, five in vivo-fertilized and developed blastocysts were collected by uterine flushing on the eighth d postfertilization. Whole blastocysts were physically attached to STO feeder layers to initiate all of the cell lines generated. The majority of the cell lines in the collection are trophectoderm, 38 NT-derived, 6 in vivo-derived, 20 IVF-derived, and 13 P-derived. Trophectoderm identity was ascertained by morphology and, in many cases, interferon-tau production. Several visceral endoderm cell lines and putative parietal endoderm cell lines were also established. At approximately 5% efficiency, epiblast masses from NT and IVF blastocysts survived and were isolated in culture. Two epiblast masses were also isolated from P blastocysts. Spontaneous differentiation from the epiblast outgrowths resulted in the establishment of fibroblast cell lines. The use of the trophectoderm cell lines as a comparative in vitro model of bovine trophectoderm and placental function is discussed in relation to NT reprogramming.

Neospora caninum: antibodies directed against tachyzoite surface protein NcSRS2 inhibit parasite attachment and invasion of placental trophoblasts in vitro

Polyclonal and monoclonal antibodies to native Neospora caninum tachyzoite surface protein NcSRS2 were generated and tested in vitro for their ability to neutralize tachyzoite attachment to and invasion of host cells. Host cells included Vero cells and a newly cloned, immortalized ovine trophoblast cell line obtained from primary cultures of ovine placenta. The ovine trophoblasts had morphology consistent with fetal trophoblasts and expressed mRNA for interferon-tau, a marker for trophoblasts. Native NcSRS2 was used to immunize mice to obtain monospecific anti-NcSRS2 polyclonal serum and anti-NcSRS2 monoclonal antibodies. Compared to irrelevant antibodies, monospecific anti-NcSRS2 serum and two anti-NcSRS2 monoclonal antibodies, 100.2.4.4 and 119.4.9.10, significantly blocked invasion of tachyzoites into both trophoblasts and Vero cells. Parasite attachment, assessed by IFA, was significantly reduced by anti-NcSRS2 mAb 100.2.4.4 and monospecific serum. The findings provide rationale to investigate a role for antibodies to NcSRS2 in prevention of N. caninum transplacental transmission in vivo.

Isolation and characterization of a bovine trophectoderm cell line derived from a parthenogenetic blastocyst

A bovine trophectoderm cell line was established from a parthenogenetic in vitro-produced blastocyst. To initiate the cell line, 8-day parthenogenetic blastocysts were attached to a feeder layer of STO fibroblasts and primary outgrowths occurred that consisted of trophectoderm, endoderm, and very occasionally epiblast tissue. Any endoderm and epiblast outgrowths were removed from the primary cultures within the first 10 days of culture by dissection. One of the primary trophectoderm cell cultures was chosen for further propagation and was passaged by physical dissociation and replating on STO feeder cells. The cell culture, designated BPT-1, was maintained in T25 flasks and passaged at a 1:3 split ratio for the first 15 passages approximately once every 2 weeks. Thereafter, the cell culture was passaged at 1:10-1:40 split ratios. Transmission electron microscopic examination showed the cells to be a polarized epithelium with apical microvilli, a thin basal lamina, and lateral junctions consisting of tight junctions and desmosomes. Lipid vacuoles and digestive vacuoles were also prominent features of the BPT-1 cells. Metaphase spread analysis at passage 59 indicated a near diploid cell population (2n = 60) with a mode and median of 60 and a mean of 64. BPT-1 cells secreted interferon-tau into the medium as measured by anti-viral assay and Western blot analysis. The cell line provides an in vitro model of parthenogenote trophectoderm whose biological characteristics can be compared to trophectoderm cell lines derived from bovine embryos produced by normal fertilization or nuclear transfer.

The cytoplasmic expression of E-cadherin and beta-catenin in bovine trophoblasts during binucleate cell differentiation

Binucleate cells are endocrine cells generated by the acytokinesis and endoreduplication of the trophectoderm in the ruminant placenta. These cells are migratory and secrete hormones into the maternal circulation after fusing with uterine epithelial cells. In this study, we performed immunohistochemistry for E-cadherin and beta-catenin in bovine placenta and a bovine trophoblast cell line (BT-1). We found that E-cadherin and beta-catenin were distributed not only at the cell to cell boundary but throughout the cytoplasm in binucleate cells, although they were concentrated at the cell to cell boundary in epithelial cells in bovine placenta. Moreover, beta-catenin was detected in the nuclei of binucleate cells. Binucleate cells after fusion with uterine epithelial cells (feto-maternal hybrid cells) in the maternal side showed no intracellular expression of E-cadherin and beta-catenin. The transformation into binucleate cells in the BT-1 cell line was also accompanied by the cytoplasmic accumulation of E-cadherin and beta-catenin. We further demonstrated that levels of cytoplasmic beta-catenin were well correlated with the DNA content of binucleate cells in BT-1. The dynamic changes in the distribution of E-cadherin and beta-catenin suggest an important role in binucleate cells, including the rearrangement of cadherin-mediated cell adhesions during cell migration and the onset of endoreduplication probably via the nuclear transfer of beta-catenin.

Gene Expression Profiles of Bovine Trophoblastic Cell Line (BT-1) Analyzed by a Custom cDNA Microarray

Gene expression of bovine trophoblast cell line (BT-1) was analyzed with a custom utero-placenta complementary DNA microarray. Expression comparison with in vivo tissues of trophoblast derivation was performed to investigate characteristics of the expression in BT-1. BT-1 is a cell line established without feeder cells using trophoblast cells that are separated from bovine blastocysts. The bovine in vivo tissues of the trophoblast derivation were collected on day 17 through 56 of gestation. Of 1,773 genes, 933 exhibited an expression difference exceeding two-fold between BT-1 and in vivo tissues. These genes were analyzed by the k-means clustering method and were distributed into six clusters. Some genes, such as placental lactogen, interferon-tau and pregnancy-associated glycoproteins, all known as trophoblast-specific genes, were detected in BT-1 as well as in vivo tissues throughout the experiment period. These trophoblast-specific genes and octamer-binding transcription factor-4, known as a marker for undifferentiation of cells in mice, were detected by RT-PCR in both BT-1 and in vivo trophoblast tissues. The overall gene expression profile in BT-1 suggests that this cell line contains trophoblast-specific characteristics and is similar to trophoblast cells around the implantation period.

The prolactin and growth hormone families: pregnancy-specific hormones/cytokines at the maternal-fetal interface

The prolactin (PRL) and growth hormone (GH) gene families represent species-specific expansions of pregnancy-associated hormones/cytokines. In this review we examine the structure, expression patterns, and biological actions of the pregnancy-specific PRL and GH families.

Differential regulation of the expression of matrix metalloproteinases and tissue inhibitors of metalloproteinases by cytokines and growth factors in bovine endometrial stromal cells and trophoblast cell line BT-1 in vitro

Degradation and reconstitution of extracellular matrix in uterine endometrium is a crucial event for embryonic implantation and is regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). In the present study, we investigated the regulation of MMP and TIMP expression in cultured bovine endometrial stromal cells (BESCs) and a bovine trophoblast cell line BT-1 (BT-1 cells). The production of proMMP-9 was induced by transforming growth factor beta (TGFbeta) and 12-O-tetradecanoylphorbol 13-acetate in the stromal cells. The treatment of BESCs with TGFbeta, insulin-like growth factor-I, and hepatocyte growth factor (HGF) resulted in a significant increase in the level of TIMP-1 in the culture medium. In addition, a significant increase of TIMP-2 production was observed in interleukin (IL)-1alpha and HGF-treated BESCs. However, the expression of TIMP-1 and TIMP-2 mRNA was not augmented by these factors. The treatment of BESCs with 12-O-tetradecanoylphorbol 13-acetate resulted in a significant increase in the level of TIMP-1 but a significant decrease in the level of TIMP-2 in the stromal cells. Membrane type-1 MMP mRNA expression in the stromal cells was augmented by tumor necrosis factor alpha (TNFalpha), IL-6, HGF, and 12-O-tetradecanoylphorbol 13-acetate. On the other hand, BT-1 cells constitutively produced proMMP-9 and proMMP-2, and the treatment of BT-1 cells with TNFalpha, HGF, and 12-O-tetradecanoylphorbol 13-acetate resulted in a significant increase in the level of proMMP-9 but not in the level of proMMP-2. The production of TIMP-1 in BT-1 cells was also augmented by IL-1alpha, TNFalpha, and HGF at the level of translation and was transcriptionally increased by 12-O-tetradecanoylphorbol 13-acetate. However, the level of TIMP-2 mRNA in BT-1 cells was not affected by any of the treatments. These results suggest that the expression of MMPs and TIMPs is differentially regulated by cytokines and growth factors and that the production of TIMP-1 and TIMP-2 may not be accompanied by changes in their mRNA expression in bovine endometrium and trophoblasts. Furthermore, as in humans and rodents, MMPs and TIMPs may contribute to the control of degradation and reconstitution of extracellular matrix in bovine endometrium during embryonic implantation and early placentation.

Cell culture on thin tissue sections commonly prepared for histopathology

Thin tissue sections commonly prepared on a glass slide for histopathology retain many in vivo biochemical attributes related not only to structure but also function. We hypothesized that such tissue sections might serve as novel cell culture substrata that would reflect tissue conditions in vivo. Here we report the applicability of tissue section substrata to tissue reconstruction and serum-free culture. Four different cell types were cultured on section and acellularized section substrata prepared from a bovine placenta. The labyrinth region of the substratum induced cell differentiation to elicit the formation of multicellular spheroids of BeWo cells (human choriocarcinoma cells), a capillary network-like structure for CPAE cells (bovine pulmonary artery endothelial cells), and a neuronal network-like structure for PC-12 cells (rat pheochromocytoma cells). The substratum provided a microenvironment that maintained the viability of PC-12 cells in a serum-free culture. We also succeeded in preparing a multicellular mass of normal human dermal fibroblasts (NHDFs) involving acellularized section-derived components. This technology offers the novel investigation of cell behaviors induced by culturing different cell types on various tissue sections and will be a useful tool for identifying cell characteristics and clarifying the molecular mechanisms that regulate the behavior of each cell type.