CD9 is expressed in extravillous trophoblasts in association with integrin alpha3 and integrin alpha5

Extracellular Vesicles Derived from Osteogenic-Differentiated Human Bone Marrow-Derived Mesenchymal Cells Rescue Osteogenic Ability of Bone Marrow-Derived Mesenchymal Cells Impaired by Hypoxia

In orthopedics, musculoskeletal disorders, i.e., non-union of bone fractures or osteoporosis, can have common histories and symptoms related to pathological hypoxic conditions induced by aging, trauma or metabolic disorders. Here, we observed that hypoxic conditions (2% O2) suppressed the osteogenic differentiation of human bone marrow-derived mesenchymal cells (hBMSC) in vitro and simultaneously increased reactive oxygen species (ROS) production. We assumed that cellular origin and cargo of extracellular vesicles (EVs) affect the osteogenic differentiation capacity of hBMSCs cultured under different oxygen pressures. Proteomic analysis revealed that EVs isolated from osteogenic differentiated hBMSC cultured under hypoxia (hypo-osteo EVs) or under normoxia (norm-osteo EVs) contained distinct protein profiles. Extracellular matrix (ECM) components, antioxidants and pro-osteogenic proteins were decreased in hypo-osteo EVs. The proteomic analysis in our previous study revealed that under normoxic culture conditions, pro-osteogenic proteins and ECM components have higher concentrations in norm-osteo EVs than in EVs derived from naïve hBMSCs (norm-naïve EVs). When selected for further analysis, five anti-hypoxic proteins were significantly upregulated (response to hypoxia) in norm-osteo EVs. Three of them are characterized as antioxidant proteins. We performed qRT-PCR to verify the corresponding gene expression levels in the norm-osteo EVs' and norm-naïve EVs' parent cells cultured under normoxia. Moreover, we observed that norm-osteo EVs rescued the osteogenic ability of naïve hBMSCs cultured under hypoxia and reduced hypoxia-induced elevation of ROS production in osteogenic differentiated hBMSCs, presumably by inducing expression of anti-hypoxic/ antioxidant and pro-osteogenic genes.

Placental cell type deconvolution reveals that cell proportions drive preeclampsia gene expression differences

The placenta mediates adverse pregnancy outcomes, including preeclampsia, which is characterized by gestational hypertension and proteinuria. Placental cell type heterogeneity in preeclampsia is not well-understood and limits mechanistic interpretation of bulk gene expression measures. We generated single-cell RNA-sequencing samples for integration with existing data to create the largest deconvolution reference of 19 fetal and 8 maternal cell types from placental villous tissue (n = 9 biological replicates) at term (n = 40,494 cells). We deconvoluted eight published microarray case-control studies of preeclampsia (n = 173 controls, 157 cases). Preeclampsia was associated with excess extravillous trophoblasts and fewer mesenchymal and Hofbauer cells. Adjustment for cellular composition reduced preeclampsia-associated differentially expressed genes (log2 fold-change cutoff = 0.1, FDR < 0.05) from 1154 to 0, whereas downregulation of mitochondrial biogenesis, aerobic respiration, and ribosome biogenesis were robust to cell type adjustment, suggesting direct changes to these pathways. Cellular composition mediated a substantial proportion of the association between preeclampsia and FLT1 (37.8%, 95% CI [27.5%, 48.8%]), LEP (34.5%, 95% CI [26.0%, 44.9%]), and ENG (34.5%, 95% CI [25.0%, 45.3%]) overexpression. Our findings indicate substantial placental cellular heterogeneity in preeclampsia contributes to previously observed bulk gene expression differences. This deconvolution reference lays the groundwork for cellular heterogeneity-aware investigation into placental dysfunction and adverse birth outcomes.

Roles of tetraspanins during trophoblast development: bioinformatics and new perspectives

Tetraspanins are a superfamily of membrane proteins found in all eukaryotic organisms. They act as scaffold molecules that regulate the traffic and function of other membrane/signaling proteins, resulting in important downstream cellular consequences. The aim of this work was to use transcriptomes and bioinformatics analysis to identify the tetraspanins (and their partners) involved in trophoblast differentiation. We built a protein-protein interaction network around tetraspanins which revealed that tetraspanins CD9, CD81, and CD82 show a specific expression during trophoblast differentiation. These proteins appeared to be interconnected and to recruit several membrane partners which include integrins, immune-related molecules, and a variety of receptors. During weeks 8 to 24, a CD9 expression trajectory was identified in extravillous trophoblasts, and a website was developed: ( https://extravillous.shinyapps.io/CD9humanEVT/ ). In conclusion, CD81 may, together with CD9 and CD82, be interconnected in controlling trophoblast invasion in the endometrium. CD9 expression trajectory in extravillous trophoblast between weeks 8 and 24 shows the involvement of CD9 in cell adhesion and migration.

CD9 and ITGA3 are regulated during HIV-1 infection in macrophages to support viral replication

Monocytes/macrophages are important target cells for HIV-1. Here, we investigated whether HIV-1 induces changes in the macrophage gene expression profile to support viral replication. We observed that the macrophage gene expression profiles dramatically changed upon HIV-1 infection. The majority of the HIV-1 regulated genes were also differentially expressed in M2a macrophages. The biological functions associated with the HIV-1 induced gene expression profile in macrophages were mainly related to inflammatory responses. CD9 and ITGA3 were among the top genes upregulated upon HIV-1 infection. We showed that these genes support viral replication and that downregulation of these genes decreased HIV-1 replication in macrophages. Here we showed that HIV-1 infection of macrophages induces a gene expression profile that may dampen inflammatory responses. CD9 and ITGA3 were among the top genes regulated by HIV-1 and were shown to support viral production most likely at the level of viral budding and release.

The Involvement of Cell Adhesion Molecules, Tight Junctions, and Gap Junctions in Human Placentation

Placentation is a major determinant of the success of pregnancy. It is regulated by several factors such as cell adhesion molecules, tight junctions, and gap junctions. The cell adhesion molecules are integrins, cadherins, immunoglobulins, nectins, and selectins. The tight junctions are composed of claudins, occludin, and junction adhesion molecule proteins while the gap junctions are composed of connexins of varying molecular weights. During placentation, some of these molecules regulate trophoblast proliferation, trophoblast fusion, trophoblast migration, trophoblast invasion, trophoblast-endothelium adhesion, glandular remodeling, and spiral artery remodeling. There is a dysregulated placental expression of some of these molecules during obstetric complications. We have, hereby, indicated the expression patterns of the subunits of each of these molecules in the various trophoblast subtypes and in the decidua, and have highlighted their involvement in physiological and pathological placentation. The available evidence points to the relevance of these molecules as distinguishing markers of the various trophoblast lineages and as potential therapeutic targets in the management of malplacentation-mediated diseases.

Promoting Roles of Embryonic Signals in Embryo Implantation and Placentation in Cooperation with Endocrine and Immune Systems

Embryo implantation in the uterus is an essential process for successful pregnancy in mammals. In general, the endocrine system induces sufficient embryo receptivity in the endometrium, where adhesion-promoting molecules increase and adhesion-inhibitory molecules decrease. Although the precise mechanisms remain unknown, it is widely accepted that maternal–embryo communications, including embryonic signals, improve the receptive ability of the sex steroid hormone-primed endometrium. The embryo may utilize repulsive forces produced by an Eph–ephrin system for its timely attachment to and subsequent invasion through the endometrial epithelial layer. Importantly, the embryonic signals are considered to act on maternal immune cells to induce immune tolerance. They also elicit local inflammation that promotes endometrial differentiation and maternal tissue remodeling during embryo implantation and placentation. Additional clarification of the immune control mechanisms by embryonic signals, such as human chorionic gonadotropin, pre-implantation factor, zona pellucida degradation products, and laeverin, will aid in the further development of immunotherapy to minimize implantation failure in the future.

Isolation, purification and in vitro differentiation of cytotrophoblast cells from human term placenta

BACKGROUND

The syncytialization of cytotrophoblast cells to syncytiotrophoblast is central to human placental transport and hormone production. Many techniques for in vitro study of this process have been proposed and new investigators to the field may find the literature in the field daunting. Here, we present a straightforward and reliable method to establish this important model using modern but readily available tools and reagents.

METHODS

Villous cytotrophoblast cells are obtained from term placenta using mild enzymatic degradation, Percoll gradient centrifugation, negative magnetic cell sorting using an antibody against classical major histocompatibility complex molecules and in vitro culture on a matrix-coated growth surface.

RESULTS

The purity of isolated cytotrophoblast cells exceeds 98 % as assessed by cytokeratin-7 expression using flow cytometry. Contamination by mesenchymal cells, extravillous trophoblast cells, leukocytes, Hofbauer and endothelial cells is minimized (less than 2 % when analyzed for vimentin, HLA-G, CD45, CD163 and CD31 using flow cytometry). Isolated cytotrophoblast cells began to aggregate into monolayers of mononucleated cells within about 12 h of plating. By 72 h in culture, most cytotrophoblast cells have differentiated into syncytiotrophoblast as demonstrated by a loss of intercellular E-cadherin expression upon fusion into multinucleated syncytia. After 72 h in culture, nearly every cultured cell expresses syncytiotrophoblast markers, including cytokeratin-7, human chorionic gonadotropin-β (β-hCG) and the fusion-related proteins glial cell missing-1 (GCM-1) and syncytin.

CONCLUSIONS

We present an efficient and reliable method for isolating of cytotrophoblast cells with high purity and complete differentiation into syncytiotrophoblast in vitro.

"Trophoblast islands of the chorionic connective tissue" (TICCT): a novel placental histologic feature

INTRODUCTION

We found isolated or clustered trophoblasts in the chorionic connective tissue of the extraplacental membranes, and defined this novel histologic feature as the "trophoblast islands of the chorionic connective tissue" (TICCT). This study was conducted to determine the clinical significance of TICCT.

METHODS

Immunohistochemistry for cytokeratin-7 was performed on the chorioamniotic membranes (N = 2155) obtained from singleton pregnancies of 1199 uncomplicated term and 956 preterm deliveries. The study groups comprised 1236 African-American and 919 Hispanic women. Gestational age ranged from 24(+0) weeks to 41(+6) weeks. Multiple logistic regression analysis was performed to investigate the magnitude of association between patient characteristics and the presence of TICCT.

RESULTS

The likelihood of TICCT was significantly associated with advancing gestational age both in term (OR: 1.29, 95% CI: 1.16-1.45, p < 0.001) and preterm deliveries (OR: 1.19, 95% CI: 1.07-1.32, p = 0.001) . Hispanic women were less likely than African-American women to have TICCT across gestation in term (OR: 0.23, 95% CI: 0.18-0.31, p < 0.001) and preterm pregnancies (OR: 0.41, 95% CI: 0.29-0.58, p < 0.001). Women with a female fetus were significantly more likely to have TICCT than women with a male fetus, in both term (OR: 1.64, 95% CI: 1.28-2.11, p < 0.001) and preterm gestations (OR: 2.04, 95% CI: 1.46-2.85, p < 0.001). TICCT was 40% less frequent in the presence of chronic placental inflammation [term (OR: 0.60, 95% CI: 0.45-0.81, p = 0.001) and preterm gestations (OR: 0.58, 95% CI: 0.40-0.84, p = 0.003)] and in parous women at term (OR: 0.60, 95% CI: 0.44-0.81, p = 0.001).

CONCLUSIONS

Our findings suggest that the duration of pregnancy, fetal sex, and parity may influence the behavior of extravillous trophoblast and placental mesenchymal cells.

Isolation and characterization of human trophoblast side-population (SP) cells in primary villous cytotrophoblasts and HTR-8/SVneo cell line

Recently, numerous studies have identified that immature cell populations including stem cells and progenitor cells can be found among “side-population” (SP) cells. Although SP cells isolated from some adult tissues have been reported elsewhere, isolation and characterization of human trophoblast SP remained to be reported. In this study, HTR-8/SVneo cells and human primary villous cytotrophoblasts (vCTBs) were stained with Hoechst 33342 and SP and non-SP (NSP) fractions were isolated using a cell sorter. A small population of SP cells was identified in HTR-8/SVneo cells and in vCTBs. SP cells expressed several vCTB-specific markers and failed to express syncytiotrophoblast (STB) or extravillous cytotrophopblast (EVT)-specific differentiation markers. SP cells formed colonies and proliferated on mouse embryonic fibroblast (MEF) feeder cells or in MEF conditioned medium supplemented with heparin/FGF2, and they also showed long-term repopulating property. SP cells could differentiate into both STB and EVT cell lineages and expressed several differentiation markers. Microarray analysis revealed that IL7R and IL1R2 were exclusively expressed in SP cells and not in NSP cells. vCTB cells sorted as positive for both IL7R and IL1R2 failed to express trophoblast differentiation markers and spontaneously differentiated into both STB and EVT in basal medium. These features shown by the SP cells suggested that IL7R and IL1R2 are available as markers to detect the SP cells and that vCTB progenitor cells and trophoblast stem cells were involved in the SP cell population.

Persistence of decidual NK cells and KIR genotypes in healthy pregnant and preeclamptic women: a case-control study in the third trimester of gestation

BACKGROUND

Natural Killer (NK) cells are the most abundant lymphocytes in the decidua during early gestation. The interactions of NK cells with the extravillous cytotrophoblast have been associated with a normal spiral artery remodeling process, an essential event for a successful pregnancy. Recent data indicate that alterations in the amount of decidual NK (dNK) cells contribute to the development of preeclampsia (PE). Moreover, genetic studies suggest that Killer Immunoglobulin-like Receptors (KIR) expressed in dNK cells influence the susceptibility to PE. Although dNK cells have been well characterized during early pregnancy, they have been scarcely studied in the third trimester of gestation. The aim of this work was to characterize dNK cells at the last trimester of gestation and to analyze the KIR genotype of healthy and PE women.

METHODS

Decidual samples were obtained during Caesarean section from control (n = 10) and PE (n = 9) women. Flow cytometric analysis of CD3, CD56, CD16 and CD9 was used to characterize and quantify dNK cells in both groups. Cell surface markers from decidual leukocytes were compared with PBMC from healthy donors.KIR genotyping was performed in genomic DNA (control, n = 86; PE, n = 90) using PCR-SSP.

RESULTS

The results indicate that dNK cells persist throughout pregnancy. They represented 20% of total leukocytes in control and PE groups, and they expressed the same cell surface markers (CD3-, CD56+, CD16- and CD9+) as dNK in the first trimester of gestation. There were no significant differences in the percentage of dNK cells between control and PE groups. The analysis of KIR gene frequencies and genotypes was not statistically different between control and PE groups. The ratio of activating to inhibitory genes indicated that the overall inhibitory balance (0.2-0.5) was more frequent in the PE group (control, 31.3% vs PE, 45.5%), and the activating balance (0.6-1.1) was more frequent in the control group (control, 68.6% vs PE, 54.4%). However this difference was not significant.

CONCLUSION

We demonstrated the persistence of dNK cells in PE and control women at the third trimester of pregnancy; these dNK cells had a similar phenotype to those found during early pregnancy. The predominance of a KIR inhibitory balance in the PE group could be associated to the physiopathology of PE.

Genome-wide expression profile of first trimester villous and extravillous human trophoblast cells

We have examined the transcriptional changes associated with differentiation from villous to extravillous trophoblast using a whole genome microarray. Villous trophoblast (VT) is in contact with maternal blood and mediates nutrient exchange whereas extravillous trophoblast (EVT) invades the decidua and remodels uterine arteries. Using highly purified first trimester trophoblast we identified over 3000 transcripts that are differentially expressed. Many of these transcripts represent novel functions and pathways that show co-ordinated up-regulation in VT or EVT. In addition we identify new players in established functions such as migration, immune modulation and cytokine or angiogenic factor secretion by EVT. The transition from VT to EVT is also characterised by alterations in transcription factors such as STAT4 and IRF9, which may co-ordinate these changes. Transcripts encoding several members of the immunoglobulin-superfamily, which are normally expressed on leukocytes, were highly transcribed in EVT but not expressed as protein, indicating specific control of translation in EVT. Interactions of trophoblast with decidual leukocytes are involved in regulating EVT invasion. We show that decidual T-cells, macrophages and NK cells express the inhibitory collagen receptor LAIR-1 and that EVT secrete LAIR-2, which can block this interaction. This represents a new mechanism by which EVT can modulate leukocyte function in the decidua. Since LAIR-2 is detectable in the urine of pregnant, but not non-pregnant women, trophoblast-derived LAIR-2 may also have systemic effects during pregnancy.

Tetraspanin CD9 regulates beta 1 integrin activation and enhances cell motility to fibronectin via a PI-3 kinase-dependent pathway

Tetraspanin CD9 regulates cell motility and other adhesive processes in a variety of tissue types. Using transfected Chinese Hamster Ovary cells as our model system, we examined the cellular pathways critical for CD9 promoted cell migration. alpha 5 beta 1 integrin was directly involved as CD9 enhanced migration was abolished by the alpha 5 beta 1 blocking antibody PB1. Furthermore, the ligand mimetic peptide RGDS, significantly upregulated the expression of a beta1 ligand induced binding site (LIBS) demonstrating for the first time that CD9 expression potentiates beta1 integrin high affinity conformation states. CD9 promoted cell motility was significantly blocked by phosphatidylinositol-3 kinase (PI-3K) inhibitors, wortmannin and LY294002, whereas inhibitors targeting protein kinase C or mitogen-activated protein kinase had no effect. PI-3K dominant/negative cDNA transfections confirmed that PI-3K was an essential component. CD9 enhanced the phosphorylation of the PI-3K substrate, Akt, in response to cell adhesion on FN. CD9 expression also upregulated p130Cas phosphorylation and total protein levels; however, p130Cas siRNA knockdown did not alter the motile phenotype. CD9 enhanced migration was also unaffected by serum deprivation suggesting that growth factors were not critical. Our studies demonstrate that CD9 upregulates beta1 LIBS, and in concert with alpha 5 beta 1, enhances cell motility to FN via a PI-3K dependent mechanism.

Leukemia inhibitory factor induces cumulus expansion in immature human and mouse oocytes and improves mouse two-cell rate and delivery rates when it is present during mouse in vitro oocyte maturation

OBJECTIVE

To examine the role of leukemia inhibitory factor (LIF) during in vitro maturation (IVM) on human and mice cumulus expansion and mice oocyte competence by in vitro fertilization (IVF), culture, and embryo transfer (ET).

DESIGN

Prospective animal and human study.

SETTING

Serono laboratories and IVF clinic.

PATIENT(S)

Healthy women volunteers and 8-week-old female mice.

INTERVENTION(S)

Cumulus compacted human and mice oocytes were matured in IVM media with and without recombinant follicle-stimulating hormone (FSH) and with and without LIF. Mice IVM oocytes with and without 0.2 IU/mL of recombinant FSH; or with and without recombinant FSH + LIF (0.1, 1.0, 1000.0 ng/mL) and ovulated oocytes were in vitro fertilized and cultured. We transferred 395 blastocysts to the uterine horn of 2.5-day pseudopregnant female mice.

MAIN OUTCOME MEASURE(S)

Cumulus expansion in human and mice oocytes, and two-cell rate, blastocyst rate, and delivered rate of live pups in mice.

RESULT(S)

In human and mouse oocytes, LIF induced cumulus expansion. When 1000 ng/mL of LIF was added in combination with recombinant FSH, a statistically significant increase in cleavage rate, embryo development rate, and birth rate was observed when compared with oocytes matured with FSH alone.

CONCLUSION(S)

Leukemia inhibitory factor induced cumulus expansion similarly in human and mouse cumulus-oocyte complexes, and recombinant FSH plus LIF supplementation during mouse IVM significantly improved oocyte competence as measured by cleavage rate, blastocyst development, and birth rate.

Integrin alpha5 is involved in fibronectin-induced human extravillous trophoblast invasion

To identify the molecules involved in human extravillous trophoblast (EVT) invasion, we raised murine mAbs that react with EVTs and obtained one mAb (CHL3) that inhibited invasion of a human choriocarcinoma-derived cell line, BeWo cells. The N-terminal 22 aminoacid sequence of the CHL3 antigen (150kDa) purified from placental tissue completely matched that of integrin alpha5, which is known to interact with fibronectin. Double immunohistochemical staining and flow cytometry confirmed the reactivity of CHL3 with integrin alpha5 and its expression on the surface of BeWo cells and human EVTs isolated from villous explant cultures. CHL3 mAb inhibited the attachment of human EVTs and BeWo cells to fibronectin-coated dishes, but not to Matrigel dishes. In the Matrigel invasion assay supplemented with or without fibronectin, the invasion of isolated EVTs and BeWo cells was attenuated by treatment with CHL3 without affecting cell proliferation. During invasion assays, the production of matrix metalloproteases 2 and 9 was not changed by CHL3. These findings suggest that interaction with fibronectin through integrin alpha5 plays an important role in human extravillous trophoblast invasion.

Tetraspan and beta-1 integrins expression pattern of the epithelial lung adenocarcinoma cell line A549 and its sensitivity to divalent cations

BACKGROUND

Tetraspans are ubiquitous integral transmembrane molecules associated on the cell surface with such adhesion molecules as integrins. Their expression has been shown to vary in tumors, but has seldom been described on lung tumoral epithelial cells, and the conditions required for a proper association of tetraspans and integrins have not yet been fully explored.

METHODS

We investigated the expression of 10 tetraspans and six beta1 integrins on the tumoral lung epithelial cell line A549. Cells were examined both in quantitative flow cytometry and as monolayers, under normal or chelated conditions, in order to determine the cation dependency of their expression.

RESULTS

Five tetraspans and four beta1 integrins are expressed on the membrane of A549 cells. Both quantitative and qualitative surface and cytoplasmic modifications of this pattern were induced in chelating conditions, suggesting the importance of divalent cations for the expression of these molecules.

CONCLUSIONS

These data indicate that a specific pattern of tetraspans and integrins, relying strongly on the availability of divalent cations in the microenvironment, is expressed by tumoral epithelial cells.

Regulation of human extravillous trophoblast function by membrane-bound peptidases

During human placentation, the invasion of extravillous trophoblasts (EVTs) into maternal decidual tissues, especially toward maternal spiral arteries, is considered an essential process for subsequent normal fetal development. However, the precise regulatory mechanisms to induce EVT invasion toward arteries and/or to protect EVTs from further invasion have not been well understood. Recently, we found that two cell surface peptidases, dipeptidyl peptidase IV (DPPIV) and carboxypeptidase-M (CP-M,) are differentially expressed on EVTs. DPPIV expression was mainly observed on EVTs that had already ceased invasion. CP-M was detected on migrating EVTs including endovascular trophoblasts in the maternal arteries. The enzymatic inhibition of these peptidases affected the invasive property of choriocarcinoma-derived cell lines, BeWo and JEG3 cells. In addition, a chemokine, RANTES, that is one of the substrates for DPPIV, enhanced invasion of EVTs isolated from primary villous explant culture and its receptor, CCR1, was specifically expressed on migrating EVTs toward maternal arteries. Furthermore, a novel membrane-bound cell surface peptidase, named laeverin, was found to be specifically expressed on EVTs that had almost ceased invasion. These findings suggest that membrane-bound peptidases are important factors regulating EVT invasion during early placentation in humans.

BAP31 and Its Caspase Cleavage Product Regulate Cell Surface Expression of Tetraspanins and Integrin-mediated Cell Survival

BAP31, a resident integral protein of the endoplasmic reticulum membrane, regulates the export of other integral membrane proteins to the downstream secretory pathway. Here we show that cell surface expression of the tetraspanins CD9 and CD81 is compromised in mouse cells from which the Bap31 gene has been deleted. CD9 and CD81 facilitate the function of multiprotein complexes at the plasma membrane, including integrins. Of note, BAP31 does not appear to influence the egress of alpha5beta1 or alpha(v)beta3 integrins to the cell surface, but in Bap31-null mouse cells, these integrins are not able to maintain cellular adhesion to the extracellular matrix in the presence of reduced serum. Consequently, Bap31-null cells are sensitive to serum starvation-induced apoptosis. Reconstitution of wild-type BAP31 into these Bap31-null cells restores integrin-mediated cell attachment and cell survival after serum stress, whereas interference with the functions of CD9, alpha5beta1, or alpha(v)beta3 by antagonizing antibodies makes BAP31 cells act similar to Bap31-null cells in these respects. Finally, in human KB epithelial cells protected from apoptosis by BCL-2, the caspase-8 cleavage product, p20 BAP31, inhibits egress of tetraspanin and integrin-mediated cell attachment. Thus, p20 BAP31 can operate upstream of BCL-2 in living cells to influence cell surface properties due to its effects on protein egress from the endoplasmic reticulum.

New regulatory mechanisms for human extravillous trophoblast invasion

Human extravillous trophoblasts (EVT) invade maternal deciduas and reconstructed maternal spiral arteries during early placentation. However, the precise regulatory mechanisms to induce EVT invasion toward arteries and/or to protect EVT from further invasion have not been well understood. Recently, it was found that EVT that had already ceased their invasion, specifically expressed cluster of differentiation (CD9) and dipeptidyl peptidase IV (DPPIV) on their cell surface. In addition, EVT migrating to maternal spiral arteries expressed CC chemokine receptor type-1 (CCR-1), which is a chemokine receptor for regulated on activation normal T cell expressed and secreted (RANTES) and so on. CD9 is associated with integrin molecules on the cell surface and is considered to modulate integrin function. In contrast, DPPIV is a cell surface peptidase that can metabolize RANTES at extracellular sites before its accessing to the chemokine receptors. In vitro functional assay showed that CD9, DPPIV and RANTES are involved in the regulation for EVT invasion. From these findings, it can be proposed that CD9 and DPPIV, including chemokines, are new regulatory factors for human extravillous trophoblasts. (Reprod Med Biol 2005; 4: 189-195).

Endocrine cell lines from the placenta

Cell-lines derived from human placenta and chorion have been used extensively to model the endocrine functions of human trophoblast. In general terms, the endocrine functions of the primary cells and tissues are at least partially replicated within the cell-lines, suggesting that they may be used as appropriate models. There are, however, two major provisos that compromise this generalisation. Firstly, the endocrine function of placenta represents a complex interaction between cytotrophoblast, syncytiotrophoblast and multiple regulators, so a single cell population digested from the normal environment is unlikely to represent this. Secondly, the characterisation of primary trophoblast populations and of cell-lines is incomplete, complicating the assignment of functions to trophoblast populations. Despite these difficulties, useful information has been obtained from the available cell-lines, regardless of whether they have arisen spontaneously, been transformed in vitro, or derived from cancers in vivo.

Evaluation of Cytokeratin 7 as an accurate intracellular marker with which to assess the purity of human placental villous trophoblast cells by flow cytometry

Villous trophoblast cells (TC) obtained from first trimester and term human placentae after trypsin/Percoll gradient isolation were immunodepleted of contaminant cells. The level of purity was assessed by the intracellular expression of the pan trophoblast marker cytokeratin-7 (CK7) and comparisons were made with the GB25 trophoblast-specific (cytotrophoblast+syncytiotrophoblast) cell surface marker. The presence of contaminating cells was traced with intracellular vimentin, or cell surface CD2, CD36, and CD163 markers and evaluated by flow cytometric analysis. The pattern of CK7 expression by trophoblast cells was also analyzed by immunofluorescence microscopy. Most batches of TC from first trimester or term placentae (92+/-3% and 96+/-2%, respectively) showed a high percentage of CK7 expressing cells, with less than 2% contaminating vimentin positive cells. In some batches of TC with a lower percentage (65+/-4%) of CK7-expressing cells, no vimentin was found, but a low percentage of CD36-expressing cells was evidenced, with no presence of CD2, and/or CD163-expressing cells. The intracellular CK7 signal correlated significantly with that of GB25 (p<0.05) cell surface expression in TC of term placentae. The choriocarcinoma BeWo and Jar cell lines also showed high levels (>92%) of CK7-expressing cells. Conversely, the control U87 astrocytoma cell line showed a high percentage (>90%) of vimentin but no CK7-expressing cells. These results provide evidence that the mutually exclusive pattern of intracellular CK7/vimentin expression of human TC can be used for evaluation by flow cytometry of the purity of primary human trophoblast cells.

A Primary Cell Culture System for Human Cytotrophoblasts of Proximal Cytotrophoblast Cell Columns Enabling In Vitro Acquisition of the Extra-villous Phenotype

Cytotrophoblast (CT) differentiation into the extra-villous phenotype is a crucial process in initiating their invasion into the decidua and thereby developing the placenta. However, how CTs differentiate into extra-villous CTs (EVCTs) is not fully elucidated. To address this, a suitable culture model for CTs has been long-sought. But this has been hampered by annoying problems such as; cell aggregation, in vitro syncytialization, low plating efficiency, etc. The aim of this study is to develop a culture system in which CTs differentiate into EVCTs. CTs were isolated from the first trimester placenta using density gradient separation and immuno-depletion using anti-CD9 antibody to remove contaminating fibroblasts and EVCTs. The resultant isolated CTs were found to have the character similar to poorly differentiated CTs comprising proximal cytotrophoblastic cell columns as confirmed by immunocytochemical and flowcytometric analyses. When cultured on type 4 collagen-coated plates in culture media containing low calcium concentration, CTs neither aggregated nor syncytialized, remaining mononuclear and monolayer state. Interestingly, cultured CTs gradually upregulated integrin alpha1, CD9, and human leukocyte antigen (HLA)-G; the known markers specific for EVCTs invading into the decidua diffusely. Hence, the CT culture system provides a sophisticated experimental model in which highly purified CTs acquire the extra-villous phenotype without syncytialization.

Preeclamptic women are deficient of interleukin-10 as assessed by cytokine release of trophoblast cells in vitro

BACKGROUND

It is well known that the acceptance of the fetoplacental unit in human pregnancy requires maternal immune tolerance, which is thought to be regulated locally by the placenta. Therefore an anti-inflammatory cytokine such as IL-10 plays a critical role in different pregnancy disorders including preeclampsia. In the present study, we examined the expression of both proinflammatory (TNF-alpha, IL-1beta, IL-2) and immunoregulatory (IL-6, IL-10) cytokines from normal term and preeclamptic patients in human trophoblast cultures.

METHODS

Eleven patients with preeclampsia and 11 patients with a normal pregnancy at term were included in the study. Trophoblast cells isolated from placentas were cultured up to 48 h under standard tissue culture conditions and cytokine release was determined by ELISA. IL-10 synthesis was significantly decreased in the third trimester in preeclamptic patients in comparison with the control group.

RESULTS

There were no significant differences in IL-1beta, IL-2, IL-6 or TNF-alpha expression but a significant alteration in IL-10 release in trophoblast cultures in vitro in term placentas from preeclamptic patients compared with normal pregnancy.

CONCLUSIONS

Because IL-10 is a potent regulator of anti-inflammatory immune response these abnormalities may be associated with the inadequate placental development in preeclampsia.

Demonstration of a tissue factor pathway inhibitor 2 messenger RNA synthesis by pure villous cytotrophoblast cells isolated from term human placentas

Tissue factor pathway inhibitor 2 (TFPI-2), a Kunitz-type proteinase inhibitor, might play an important role during placenta growth by regulating trophoblast invasion and differentiation. Many TFPI-2 transcripts have been detected in syncytiotrophoblast cells, but conflicting results have been reported concerning TFPI-2 synthesis by the cytotrophoblast. To address this issue, we developed a method to isolate pure preparations of human villous cytotrophoblast cells from normal term placentas, and the synthesis of tissue factor, TFPI-1, and TFPI-2 mRNAs was then evaluated. Cells were isolated by trypsin-DNase-EDTA digestion, followed by Percoll gradient separation and immunodepletion of human leukocyte antigen-positive cells. The quality of villous cytotrophoblast cells was verified by electron microscopy. Purity of cell preparations was assessed by labeling cells with GB25, a monoclonal antibody specific to villous trophoblast cells, and by checking the absence of contaminating cells using anti-CD9 antibody. The lack of hCG, CD32 mRNA, and tissue factor mRNA also indicated the absence of contaminating cells. Using competitive reverse transcription polymerase chain reaction, we showed that freshly isolated villous cytotrophoblast cells synthesized significant levels of TFPI-1 mRNA and larger amounts of TFPI-2 mRNA. TFPI-1 and TFPI-2 mRNA synthesis remained unchanged when cytotrophoblast cells were cultured in complete medium and evolved as a multinucleated syncytiotrophoblast. These results indicate that the villous cytotrophoblast and syncytiotrophoblast are both important sites of TFPI-2 synthesis in the human placenta. This study also indicates that tissue factor detection should be used systematically to check the purity of cytotrophoblast cell preparations because it allows detection of contamination by monocytes/macrophages and by syncytial fragments.

Identification of CD9 extracellular domains important in regulation of CHO cell adhesion to fibronectin and fibronectin pericellular matrix assembly

CD9, a 24-kDa member of the tetraspanin family, influences cellular growth and development, activation, adhesion, and motility. Our investigation focuses on the hypothesis that the CD9 second extracellular loop (EC2) is important in modulating cell adhesive events. Using a Chinese hamster ovary (CHO) cell expression system, we previously reported that CD9 expression inhibited cell adhesion to fibronectin and fibronectin matrix assembly. For the first time, a functional epitope on CD9 EC2 that regulates these processes is described. Binding of mAb7, an EC2-specific anti-CD9 monoclonal antibody, reversed the CD9 inhibitory activity on CHO cell adhesion and fibronectin matrix assembly. This reversal of cell phenotype also was observed in CHO cells expressing CD9 EC2 truncations. Furthermore, our data showed that the EC2 sequence (173)LETFTVKSCPDAIKEVFDNK(192) was largely responsible for the CD9-mediated CHO cell phenotype. Two peptides, (135)K-V(172) (peptide 5b) and (168)P-I(185) (peptide 6a), selectively blocked mAb7 binding to soluble CD9 and to CD9 on intact cells. These active peptides reversed the influence of CD9 expression on CHO cell adhesion to fibronectin. In addition, confocal microscopy revealed that CD9 colocalized with the integrin alpha(5)beta(1) and cytoskeletal F-actin in punctate clusters on the cell surface, particularly at the cell margins. Immunoprecipitation studies confirmed CD9 association with beta(1) integrin. The cellular distribution and colocalization of focal adhesion kinase and alpha-actinin with cytoskeletal actin was also influenced by CD9 expression. Thus, CD9 may exhibit its effect by modulating the composition of adhesive complexes important in facilitating cell adhesion and matrix assembly.

Chinese hamster ovary cell motility to fibronectin is modulated by the second extracellular loop of CD9. Identification of a putative fibronectin binding site

CD9, a member of the tetraspanin family of proteins, is characterized by four transmembrane domains and two extracellular loops. Surface expression of CD9 on Chinese hamster ovary (CHO) cells dramatically enhances spreading and motility on fibronectin. To elucidate the mechanistic basis of CD9-fibronectin interaction, binding to fibronectin was investigated using purified and recombinant forms of CD9. The affinity of fibronectin for CD9 in enzyme-linked immunosorbent assay was 81 +/- 25 nm. The binding of fibronectin to immobilized CD9 was enhanced by Ca(2+) ions. Protein binding and peptide competition studies demonstrated that peptide 6 derived from CD9 extracellular loop 2 (amino acids 168-192) contained part of the fibronectin-binding domain. Additionally, enhanced adhesion of CD9-CHO-B2 cells to fibronectin was significantly reduced by peptide 6. CD9-CHO cells had a 5-fold increase in motility to fibronectin as compared with mock-transfected controls, an effect that correlated with CD9 cell surface density. Truncation of CD9 extracellular loop 2 and peptide 6 caused inhibition of CD9-CHO cell motility to fibronectin. Deletion of CD9 extracellular loop 1 had no significant effect on CHO cell motility. These findings demonstrate a critical role for CD9 extracellular loop 2 in cell motility to fibronectin and clarify the mechanism by which CD9-fibronectin interaction modulates cell adhesion and motility.

Expression of fertilin and CD9 in bovine trophoblast and endometrium during implantation

The superficial placentation of cattle involves the development of fetal binucleate cells that arise from the chorion and migrate between adjacent cell tight junctions to fuse with maternal epithelium. Thus, the temporal and spatial patterns of expression of the cell migration, adhesion, and fusion molecules fertilin and CD9 were investigated in bovine trophoblast and endometrium. Bovine fertilin alpha and fertilin beta messenger RNA sequences were amplified by reverse transcriptase-polymerase chain reaction in testis (positive control), peri-implantation (Days 18, 19, and 21), and postimplantation (Days 35-40) trophoblast RNA, but not in caruncular endometrium (Day 40). Northern blot analysis indicated that the transcript hybridizing to fertilin alpha in trophoblast RNA was approximately 4.0 kilobases (kb), whereas in testis, 2 transcripts of approximately 3.3 and 3.8 kb were indicated. The transcript hybridizing to the fertilin beta probe was also larger in trophoblast than in testis ( approximately 3.8 vs. 2.4 kb, respectively). In situ hybridization revealed that fertilin beta mRNA was expressed by trophoblast cells, including binucleate cells. Immunohistochemical study of CD9, a member of the transmembrane-4-superfamily which is thought to be involved in sperm-egg fusion, showed that CD9 was present on the apical surface of uterine epithelium and in a subpopulation of binucleate cells of the trophoblast. Immunoprecipitation followed by Western blot analysis showed association between CD9 and integrin alpha3 in endometrium. The results support the hypothesis that fertilin and CD9 are involved in bovine binucleate cell migration and fusion.

Preparation and functional characterization of villous cytotrophoblasts free of syncytial fragments

Recent studies suggest that purified villous cytotrophoblasts are largely contaminated by mononucleated syncytial fragments and therefore unsuitable for studies of trophoblast differentiation. We assessed highly purified (>99.99 per cent) populations of villous trophoblasts for fragment contamination using the syncytial markers placental alkaline phosphatase (PLAP, by immunohistochemistry) and exteriorized phosphatidyl serine (ePS, by flow cytometric analysis). The preparations contained from 4-46 per cent syncytial fragments. However, we find that PLAP negative cells preferentially adhere to tissue culture surfaces and that all preparations were <2 per cent PLAP positive after routine plating and washing procedures. A second purification procedure eliminated dead (propidium iodide permeable) cells and separated viable syncytial fragments (ePS-positive) from viable cytotrophoblasts (ePS-negative) by two colour fluorescence activated cell sorting (FACS). Viable ePS-positive cells were ultrastructurally apoptotic, adhered poorly in culture and those that adhered rapidly underwent apoptosis. Viable ePS-negative cells contained large heterochromic nuclei and cytoplasmic structures, adhered strongly in culture and remained viable. The latter population (putative true villous CT) differentiated into syncytialized cells when cultured with EGF. We conclude that villous CT can be routinely purified, are viable in culture and can undergo syncytial fusion without extensive preformed syncytium.

Murine CD9 is the receptor for pregnancy-specific glycoprotein 17

Pregnancy-specific glycoproteins (PSGs) are a family of highly similar secreted proteins produced by the placenta. PSG homologs have been identified in primates and rodents. Members of the human and murine PSG family induce secretion of antiinflammatory cytokines in mononuclear phagocytes. For the purpose of cloning the receptor, we screened a RAW 264.7 cell cDNA expression library. The PSG17 receptor was identified as the tetraspanin, CD9. We confirmed binding of PSG17 to CD9 by ELISA, flow cytometry, alkaline phosphatase binding assays, and in situ rosetting. Anti-CD9 monoclonal antibody inhibited binding of PSG17 to CD9-transfected cells and RAW 264.7 cells. Moreover, PSG17 binding to macrophages from CD9-deficient mice was significantly reduced. We then tested whether PSG17 binds to other members of the murine tetraspanin family. PSG17 did not bind to cells transfected with CD53, CD63, CD81, CD82, or CD151, suggesting that PSG17-CD9 binding is a specific interaction. We have identified the first receptor for a murine PSG as well as the first natural ligand for a member of the tetraspanin superfamily.

Complexes of tetraspanins with integrins: more than meets the eye

The transmembrane proteins of the tetraspanin superfamily are implicated in a diverse range of biological phenomena, including cell motility, metastasis, cell proliferation and differentiation. The tetraspanins are associated with adhesion receptors of the integrin family and regulate integrin-dependent cell migration. In cells attached to the extracellular matrix, the integrin-tetraspanin adhesion complexes are clustered into a distinct type of adhesion structure at the cell periphery. Various tetraspanins are associated with phosphatidylinositol 4-kinase and protein kinase C isoforms, and they may facilitate assembly of signalling complexes by tethering these enzymes to integrin heterodimers. At the plasma membrane, integrin-tetraspanin signalling complexes are partitioned into specific microdomains proximal to cholesterol-rich lipid rafts. A substantial fraction of tetraspanins colocalise with integrins in various intracellular vesicular compartments. It is proposed that tetraspanins can influence cell migration by one of the following mechanisms: (1) modulation of integrin signalling; (2) compartmentalisation of integrins on the cell surface; or (3) direction of intracellular trafficking and recycling of integrins.

Specific interactions among transmembrane 4 superfamily (TM4SF) proteins and phosphoinositide 4-kinase

In earlier work we established that phosphoinositide 4-kinase (PI 4-kinase) may associate with transmembrane 4 superfamily (TM4SF, tetraspanin) proteins, but critical specificity issues were not addressed. Here we demonstrate that at least five different TM4SF proteins (CD9, CD63, CD81, CD151 and A15/TALLA1) can associate with a similar or identical 55 kDa type II PI 4-kinase. These associations were specific, since we found no evidence for other phosphoinositide kinases (e.g. phosphoinositide 3-kinase and phosphoinositide-4-phosphate 5-kinase) associating with TM4SF proteins, and many other TM4SF proteins (including CD82 and CD53) did not associate with PI 4-kinase. CD63-PI 4-kinase complexes were almost entirely intracellular, and thus are distinct from other TM4SF-PI 4-kinase complexes (e.g. involving CD9), which are largely located in the plasma membrane. These results suggest that a specific subset of TM4SF proteins may recruit PI 4-kinase to specific membrane locations, and thereby influence phosphoinositide-dependent signalling.

Antibody reaction patterns in first trimester placenta: implications for trophoblast isolation and purity screening

The aim of this immunohistochemical and cytochemical study was to select specific antibodies to establish an efficient purification protocol for first trimester trophoblast and for subsequent purity screening of isolated trophoblast cells. The reactivity of antibodies to various cytokeratin filaments, glycoprotein CD9, fibroblast specific antigen (FSA), common leukocyte antigen CD45RB and macrophage antigens CD163, CD68 and CD14 were studied on cryosections of placental tissue. Among the cytokeratins tested, cytokeratin 7 was the only keratin filament type, which was not expressed in placental mesenchymal cells, but in all trophoblast subpopulations. Since anti-CD9, in addition to mesenchymal cells, also strongly labels extravillous cytotrophoblast cells, whereas the antibody to FSA only reacts with mesenchymal cells, anti-FSA is suitable as a depletion antibody for mesenchymal cells. Among the macrophage markers anti-CD163 was the most specific for Hofbauer cells. CD45RB was expressed on maternal and fetal leukocytes as well as on Hofbauer cells. Isolated first trimester placental cell preparations that have been collected from a density gradient contained up to 45 per cent non-trophoblast cells. Immunocytochemistry using antibodies to CK7, FSA, vimentin, CD45RB and CD163 demonstrated that subsequent immunodepletion with antibodies to CD45RB and FSA increased the purity of the trophoblast preparation to greater than 98 per cent. According to this study trophoblasts from first trimester placentae should be identified by cytokeratin antibodies specific for the isoform 7. Purification of isolated trophoblasts by density gradient alone does not result in a sufficient degree of purity.

Anti-CD9 monoclonal antibody-stimulated invasion of endometrial cancer cell lines in vitro: possible inhibitory effect of CD9 in endometrial cancer invasion

Cell surface marker CD9 has been reported to play a role in inhibiting trophoblastic cell invasion. Since the invasive properties of cancer cells may resemble those of trophoblasts, we decided to investigate the role of CD9 in the invasion of endometrial cancer cells. In normal human endometrium, CD9 was found to be constitutively expressed on epithelial cells, as reported previously. While epithelial cells of endometrial hyperplasia (n = 5) were also positive for the expression of CD9, endometrial adenocarcinomas (n = 15) showed reduced expression. In order to clarify the significance of this reduced CD9 expression in endometrial cancer, an in-vitro invasion assay system was used to assess the effect of anti-CD9 monoclonal antibody (mAb) on the invasive properties of endometrial cancer cell line. Anti-CD9 mAb significantly enhanced invasion of the RL95-2 and Ishikawa cell lines, without affecting cell proliferation. Since CD9 is associated with the integrin subunits beta(1), alpha(3) and alpha(6) in human endometrium, we investigated the functional relationship between CD9 and these integrins in the RL95-2 cell line. Monoclonal antibodies against the integrins beta(1), alpha(3) and alpha(6) inhibited RL95-2 cell invasion. However, anti-CD9 mAb continued to show a stimulatory effect on RL95-2 cell invasion after treatment with anti-integrin alpha(3) mAb. In contrast, the anti-CD9 mAb had no effect after treatment with the mAb for integrins alpha(6) and beta(1). These findings indicate that CD9 is involved in regulating the invasive properties of endometrial carcinoma cells and that this effect is partially mediated by integrin subunits alpha(6) and beta(1). Thus, CD9 appears to be involved in the prevention of endometrial cancer invasion.

CD9 is expressed on human endometrial epithelial cells in association with integrins alpha(6), alpha(3) and beta(1)

Recently we reported that CD9 is involved in the invasion of a trophoblast-like choriocarcinoma cell line, BeWo, probably through the regulation of integrin functions. Integrins have also been reported to be expressed in the human endometrium and it has been suggested that they play important roles in blastocyst implantation. This study used immunohistochemistry to investigate the expression of CD9 in the endometrium during the menstrual cycle. CD9 was found to be intensely expressed on the cell surface of the glandular epithelium throughout the menstrual cycle without any apparent differences in staining intensity. In addition, Western blotting analysis of the affinity-purified proteins confirmed that CD9 was associated with integrins beta(1), alpha(3) and alpha(6) in the human endometrium. Therefore it can be concluded that CD9, in association with integrins alpha(6), alpha(3) and beta(1), is a constitutive molecule of the endometrial glandular epithelium. These results also suggest that CD9 may be an important regulator of these integrins in the human endometrium.