Chemokine CXCL16, a scavenger receptor, induces proliferation and invasion of first-trimester human trophoblast cells in an autocrine manner

Toxoplasma gondii infection induces the expression of the chemokine CXCL16 in macrophages to promote chemoattraction of CXCR6+ cells

CXCL16 is a multifaceted chemokine expressed by macrophages and other immune cells in response to viral and bacterial pathogens. However, few studies have investigated its role in parasitic infections. The obligate intracellular parasite Toxoplasma gondii (T. gondii) is the causative agent of toxoplasmosis, an infection with potentially deleterious consequences in immunocompromised individuals and the developing fetus of acutely infected pregnant women. Chemokines are critical mediators of host defense and, as such, dysregulation of their expression is a subversion strategy often employed by the parasite to ensure its survival. Herein, we report that types I and II T. gondii strains upregulated the expression of both transmembrane and soluble forms of CXCL16 in infected bone marrow-derived macrophages (BMDM). Exposure to soluble T. gondii antigens (STAg) and to excreted-secreted proteins (TgESP) led to the induction of CXCL16. Cxcl16 mRNA abundance and CXCL16 protein levels increased in a time-dependent manner upon T. gondii infection. Importantly, conditioned medium (CM) collected from T. gondii-infected wild-type (WT) macrophage cultures promoted the migration of RAW264.7 cells expressing CXCR6, the cognate receptor of CXCL16, an effect that was significantly reduced by a neutralizing anti-CXCL16 antibody or use of CM from CXCL16 knockout (KO) macrophages. Lastly, T. gondii-driven CXCL16 expression appeared to modulate cytokine-induced (IL-4 + IL-13) alternative macrophage activation and M2 phenotypic marker expression. Further investigation is required to determine whether this chemokine contributes to the pathogenesis of toxoplasmosis and to elucidate the underlying molecular mechanisms.

A systematic review and risk of bias analysis of in vitro studies on trophoblast response to immunological triggers

An increasing amount of evidence suggests that immune responses may affect trophoblast functioning, which in turn may play a role in gestational disorders and fetal development. This systematic review offers the first summary of in vitro studies on the trophoblast response to immunological triggers, in conjunction with a risk of bias analysis. A search in Pubmed and Embase yielded 110 relevant studies. Primary trophoblasts were the most commonly used cell type, but trophoblast subtypes were not always defined. Similarly, the exact natures of trophoblast cell lines were sometimes unclear. Cytokines and Toll-like receptor agonists were often used as interventions, but most studies focused on a select few substances such as tumor necrosis factor-α and lipopolysaccharide. In regard to the outcome parameters, some important trophoblast functions, such as hormone production and barrier formation were underrepresented. Whether or not risk of bias was high varied strongly between types of bias. Risk of selection bias, for example, was usually low. However, none of the included studies mentioned blinding or plate randomization. Only a select few studies mentioned passage numbers, use of vehicle control or conflict of interest. In conclusion, better characterization of trophoblast subtypes and a broader range of studied interventions and outcome parameters would contribute to a more complete understanding of trophoblast responses to immune stimuli. Additionally, researchers are encouraged to replicate experiments and pay close attention when setting up and writing down methodologies, in order to improve the reproducibility and translatability of their work.

Regulation and Function of Chemokines at the Maternal–Fetal Interface

Successful pregnancy requires the maternal immune system to tolerate the semi-allogeneic embryo. A good trophoblast function is also essential for successful embryo implantation and subsequent placental development. Chemokines are initially described in recruiting leukocytes. There are rich chemokines and chemokine receptor system at the maternal–fetal interface. Numerous studies have reported that they not only regulate trophoblast biological behaviors but also participate in the decidual immune response. At the same time, the chemokine system builds an important communication network between fetally derived trophoblast cells and maternally derived decidual cells. However, abnormal functions of chemokines or chemokine receptors are involved in a series of pregnancy complications. As growing evidence points to the roles of chemokines in pregnancy, there is a great need to summarize the available data on this topic. This review aimed to describe the recent research progress on the regulation and function of the main chemokines in pregnancy at the maternal–fetal interface. In addition, we also discussed the potential relationship between chemokines and pregnancy complications.

Human Chorionic Villous Differentiation and Placental Development

In humans, the placenta provides the only fetomaternal connection and is essential for establishing a pregnancy as well as fetal well-being. Additionally, it allows maternal physiological adaptation and embryonic immunological acceptance, support, and nutrition. The placenta is derived from extra-embryonic tissues that develop rapidly and dynamically in the first weeks of pregnancy. It is primarily composed of trophoblasts that differentiate into villi, stromal cells, macrophages, and fetal endothelial cells (FEC). Placental differentiation may be closely related to perinatal diseases, including fetal growth retardation (FGR) and hypertensive disorders of pregnancy (HDP), and miscarriage. There are limited findings regarding human chorionic villous differentiation and placental development because conducting in vivo studies is extremely difficult. Placental tissue varies widely among species. Thus, experimental animal findings are difficult to apply to humans. Early villous differentiation is difficult to study due to the small tissue size; however, a detailed analysis can potentially elucidate perinatal disease causes or help develop novel therapies. Artificial induction of early villous differentiation using human embryonic stem (ES) cells/induced pluripotent stem (iPS) cells was attempted, producing normally differentiated villi that can be used for interventional/invasive research. Here, we summarized and correlated early villous differentiation findings and discussed clinical diseases.

Identification of genes associated with susceptibility to persistent breeding-induced endometritis by RNA-sequencing of uterine cytobrush samples

This study aimed to investigate the susceptibility to persistent breeding-induced endometritis (PBIE). Cytobrush samples were collected from 81 broodmares 1-3 days before artificial insemination (AI). Susceptibility to PBIE was evaluated by the presence of ≥ 2 cm of intrauterine fluid 24 h after AI, besides the fertility was determined by a sonographic pregnancy diagnosis 2 weeks after ovulation. RNA expressions were compared between susceptible non-pregnant (SNP) mares (n=9) and resistant pregnant (RP) mares (n=9) as well as between susceptible pregnant (SP) mares (n=9) and susceptible non-pregnant (SNP) mares. 66 differentially expressed genes (DEGs) were identified between SNP and RP mares and 60 DEGs between SP and SNP mares. In SNP compared to RP mares, transcript levels of genes regulating steroid hormone metabolism and neutrophil chemotaxis were lower, while higher for genes participating in uterine inflammation.Transcripts of genes related to extracellular matrix degradation, tissue adhesions, and fibrosis were lower in SP mares than in SNP mares, while higher for genes related to uterine cell proliferation, differentiation, and angiogenesis in SP mares than SNP mares. In conclusion, increased transcript levels of apolipoprotein E (APOE) and roundabout 2 (ROBO2), cluster domain 44 (CD44), integrin beta 3 (ITGB3), and epidermal growth factor (EGF) are possible biomarkers for susceptibility to PBIE. While higher expression of fibroblast growth factor 9 (FGF9), kinase domain receptor (KDR), and C-X-C motif chemokine ligand (CXCL) 16, collagen type V alpha 2 (COL5A2) and fibronectin (FN1) are suggested indicators of fertility in susceptible mares if they receive proper breeding management.

CXCL5 Downregulation in Villous Tissue Is Correlated With Recurrent Spontaneous Abortion

Recurrent spontaneous abortion (RSA) affects 5% of childbearing-age women worldwide. Inadequate trophoblast invasion is one of the main reasons for the development of RSA; however, the underlying molecular mechanisms for RSA have not been fully understood, and further explanation is urgently needed. C-X-C motif chemokine ligand 5 (CXCL5) is reported to contribute to the invasion of cancer cells, and its aberrant expression is associated with the cellular process of tumor pathology. Considering the high behavioral similarity between trophoblast cells and cancer cells, we hypothesized that CXCL5 may influence trophoblast invasion, and its expression levels in villous tissue may be correlated with RSA. In this study, we firstly investigated the CXCL5 expression in placental villous tissues of 15 RSA patients and 13 control patients, and the results showed that CXCL5 levels were significantly lower in villous tissue from RSA patients than those of the controls. Further in vitro experiments presented that recombinant human CXCL5 can enhance trophoblast migration, invasion, and epithelial-to-mesenchymal transition (EMT) process. We also demonstrated that CXCL5 exerted these effects on trophoblast cells through PI3K/AKT/ERK1/2 signaling pathway. In conclusion, these data indicate that CXCL5 downregulation in human villous tissue is correlated with RSA. Additionally, we found that estrogen, progesterone, human chorionic gonadotropin, and decidual stromal cells can regulate CXCL5 and chemokine receptor 2 (CXCR2) expression of trophoblast in a cell manner.

Decidual IDO+ macrophage promotes the proliferation and restricts the apoptosis of trophoblasts

Indoleamine 2, 3-dioxygenase (IDO), a tryptophan-catabolizing enzyme, is essential in physiological immunoregulation. The present research was conducted to elucidate the expression and roles of IDO in decidual macrophages (dMφ) during early pregnancy. Here, we observed a remarkable decrease of IDO⁺ dMφ from patients with unexplained recurrent spontaneous abortion (URSA). IDO⁺ dMφ displayed M2 phenotype with higher CD206, CD209 and CD163, and lower CD86. Interestingly, treatment with 1-methyl-d-tryptophan (1-MT, an IDO pathway inhibitor) led to the M1 bias of dMφ. Further analysis of the cytokine array and the qPCR showed decreased levels of trophoblast proliferation or invasion-related molecules (e.g., CXCL12 and BMP2) in 1-MT-treated dMφ. The data of co-culture system showed that 1-MT-pretreated dMφ decreased the proliferation and the expression of Ki-67 and Bcl-2, and increased cell apoptosis of HTR-8/Snveo cells. Additionally, the expression of IDO in U937 cells was up-regulated by decidual stromal cells (DSC) and HTR-8/Snveo cells in vitro, as well as estradiol and medroxyprogesterone. These data suggest that endocrine environment, DSC and trophoblasts should contribute to the high level of IDO in dMφ, and IDO⁺ dMφ with M2 dominant phenotype promote the survival of trophoblasts during early pregnancy. The abnormal lower level of IDO should trigger the dysfunction of dMφ, further suppress the survival of trophoblasts and increase the risk of miscarriage.

Natural killer cells: functional differences in recurrent spontaneous abortion†

Recurrent spontaneous abortion (RSA) is one of the major pregnancy disorders and poses a serious risk to both the mother and the fetus. Although a number of research efforts have been conducted, therapeutic advances for treating RSA have not lived up to their expectations. Hence, other treatments should be explored. The important role of natural killer (NK) cells in immunotherapy is attracting increasing attention, both as a pharmaceutical target and for cell therapies. NK cells are abundant in the endometrium and play a role in implantation and placentation in normal pregnancy. As research progresses, NK cells are increasingly regarded as playing essential roles in the emergence and development of RSA. In this article, I review recent findings on the role of uterine NK cells in the pathophysiology of RSA. These cells may become therapeutic NK cell-related targets. In conclusion, although several issues regarding NK cells in RSA remain unresolved and require further investigation, extensive evidence is available for the treatment of RSA.

OVOL2 attenuates the expression of MAP3K8 to suppress epithelial mesenchymal transition in colorectal cancer

BACKGROUND

Inactivation of members of the OVO-like family of C2H2 zinc-finger transcription factor 2 (OVOL2) is increased after colorectal cancer (CRC) metastasis. This study investigated the functional roles and clinical relevance of OVOL2 and its downstream factors in colorectal carcinogenesis.

METHODS

Transcriptome RNA sequencing (RNA-seq) of HCT116 cells overexpressing OVOL2 and SW480 cells silencing OVOL2 were conducted. We cross-checked the Chromatin Immunoprecipitation sequencing (ChIP-seq, GSM1239518) positive peaks and RNA-seq differential expression genes (DEGs). In vitro functional assays, including wound-healing assay and transwell assay, were performed. The RNA expression (n = 597) and protein expression (n = 93) of OVOL2- mitogen-activated protein kinase kinase kinase 8 (MAP3K8)-C-X-C Motif Chemokine Ligand 16 (CXCL16) were evaluated in human CRC and adjacent normal tissues. CXCL16 levels in cell culture supernatants and serum samples obtained from 29 colon polyps patients and 24 CRC patients were measured using ELISA.

RESULTS

We found that OVOL2 inhibited the migration and epithelial mesenchymal transition (EMT) of CRC cells by blocking the MAP3K8/AKT/NF-κB signaling pathway, and also decreased levels of CXCL16, a chemokine downstream of the MAP3K8/AKT/NF-κB signaling pathway. Furthermore, patient tumor tissue samples showed a lower level of in situ OVOL2 (P = 0.005) and higher CXCL16 (P = 0.001) levels, compared to adjacent normal tissues. Survival analyses revealed that both OVOL2 (logrank P = 0.063) and CXCL16 (logrank P = 0.048) were associated with overall survival (OS) and were independent prognostic factors for CRC. Additionally, OVOL2 and CXCL16 were found to be prognostically relevant (logrank P = 0.038). CXCL16 may serve as a potential diagnostic biomarker for CRC (P = 0.010).

CONCLUSIONS

The OVOL2/ MAP3K8/CXCL16 axis is a key player in colonic tumorigenesis and metastasis, and may be a potential diagnostic and prognostic biomarker.

Osteoprotegerin interacts with syndecan-1 to promote human endometrial stromal decidualization by decreasing Akt phosphorylation

STUDY QUESTION

Does osteoprotegerin (OPG) promote human endometrial stromal decidualization?

SUMMARY ANSWER

OPG is essential for human endometrial stromal decidualization through its interaction with syndecan-1 to decrease Akt phosphorylation.

WHAT IS KNOWN ALREADY

OPG (a cytokine receptor) levels are significantly increased in the circulation of pregnant women. However, the role and mechanism of OPG in human endometrial stromal cell (ESC) decidualization remain elusive.

STUDY DESIGN, SIZE, DURATION

We analyzed the endometrial expression of OPG in endometrial tissue samples collected from women with regular menstrual cycles (ranging from 25 to 35 days), and decidual tissue samples collected from woman with normal early pregnancy or recurrent pregnancy loss (RPL) who visited the Department of Gynecology and Obstetrics at a tertiary care center from January to October 2018. None of the subjects had hormonal treatment for at least 3 months prior to the procedure. In total, 16 women with normal early pregnancy and 15 with RPL were selected as subjects for this study. The function of OPG in decidualization was explored in a human endometrial stromal cell (HESC) line and primary cultures of HESCs.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We collected endometrial tissues (by biopsy) from the subjects during their menstrual cycle and decidual tissues from subjects with a normal early pregnancy and those with RPL at the time of dilation and curettage. The control group comprised randomly selected women who underwent termination of an apparently normal early pregnancy. The endometrial OPG expression was analyzed using immunohistochemical staining and quantitative RT-PCR (qRT-PCR). Immunofluorescence staining and western blot, and qRT-PCR were used to explore the mRNA and protein expression, respectively, of OPG in an immortalized HESC line and in primary cultures of HESC during proliferation and decidualization. siRNA-mediated knockdown experiments were performed to examine the function of OPG in HESC proliferation and decidualization. Flow cytometry and the cell proliferation MTS assay were performed to further examine the role of OPG in HESC proliferation. We also analyzed decidual marker gene expression by qRT-PCR to assess the consequences of OPG loss for HESC decidualization. A co-immunoprecipitation (IP) assay was used to determine the potential interaction between the OPG and Syndecan-1. Western blot analysis of the rescue experiments performed using the phosphatidylinositol 3-kinase (PI3K) signaling-specific inhibitor LY294002 was used to investigate the downstream signaling pathways through which OPG could mediate HESC decidualization.

MAIN RESULTS AND THE ROLE OF CHANCE

OPG was expressed in both the human endometrium and in vitro decidualized ESCs. Knockdown experiments revealed that OPG loss impaired the expression of IGF-binding protein-1 (IGFBP-1) (P < 0.05) and prolactin (PRL) (P < 0.05), two specific markers of decidualization, in HESC undergoing decidualization. We also uncovered that OPG knockdown induced the aberrant activation of Akt (protein kinase B) during HESC decidualization (P < 0.05). The inhibition of Akt activation could rescue the impaired expression of the decidual markers PRL (P < 0.05) and IGFBP-1 (P < 0.05) in response to OPG knockdown. Syndecan-1 was considered a potential receptor candidate, as it was expressed in both the endometrium and in vitro cultured stromal cells. Subsequent co-IP experiments demonstrated the interaction between OPG and Syndecan-1 during decidualization. In addition, Syndecan-1 knockdown not only clearly attenuated the decidualization markers PRL (P < 0.05) and IGFBP-1 (P < 0.05) but also induced the aberrant enhancement of Akt phosphorylation in decidualized cells, consistent with the phenotype of OPG knockdown cells. Finally, we revealed that the transcript and protein expression of both OPG and Syndecan-1 was significantly lower in the decidual samples of women with RPL than in those of women with normal pregnancy (P < 0.05).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

In this study, based on a number of approaches, it was demonstrated that OPG mediated the repression of Akt that occurs during human stromal cell decidualization, however, the molecular link between OPG and Akt signaling was not determined, and still requires further exploration.

WIDER IMPLICATIONS OF THE FINDINGS

OPG is required for decidualization, and a decrease in OPG levels is associated with RPL. These findings provide a new candidate molecule for the diagnosis and potential treatment of RPL.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported in part by the National Natural Science Foundation of China U1605223 (to G.S.), 81701457 (to Y.J.) and 81601349 (to Y.J.). The authors have no conflicts of interest to disclose.

Functional Evaluation of STOX1 (STORKHEAD-BOX PROTEIN 1) in Placentation, Preeclampsia, and Preterm Birth

Revaluation of the association of the STOX1 (STORKHEAD_BOX1 PROTEIN 1) transcription factor mutation (Y153H, C allele) with the early utero-vascular origins of placental pathology is warranted. To investigate if placental STOX1 Y153H genotype affects utero-vascular remodeling-compromised in both preterm birth and preeclampsia-we utilized extravillous trophoblast (EVT) explant and placental decidual coculture models, transfection of STOX1 wild-type and mutant plasmids into EVT-like trophoblast cell lines, and a cohort of 75 placentas from obstetric pathologies. Primary EVT and HTR8/SVneo cells carrying STOX1 Y153H secreted lower levels of IL (interleukin) 6, and IL-8, and higher CXCL16 (chemokine [C-X-C motif] ligand 16) and TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) than wild-type EVT and Swan71 cells. Media from wild-type EVT or Swan71 cells transfected with wild-type STOX1 stimulated: endothelial chemokine expression, angiogenesis, and decidual natural killer cell and monocyte migration. In contrast, Y153H EVT conditioned medium, Swan71 transfected with the Y153H plasmid, or HTR8/SVneo media had no effect. Genotyping of placental decidual cocultures demonstrated association of the placental STOX1 CC allele with failed vascular remodeling. Decidual GG NODAL R165H increased in failed cocultures carrying the placental CC alleles of STOX1. Multivariate analysis of the placental cohort showed that the STOX1 C allele correlated with premature birth, with or without severe early-onset preeclampsia, and small for gestational age babies. In conclusion, placental STOX1 Y153H is a precipitating factor in preterm birth and placental preeclampsia due to defects in early utero-placental development.

Regulation of CXCR6 Expression on Adipocytes and Osteoblasts Differentiated from Human Adipose Tissue-Derived Mesenchymal Stem Cells

Human mesenchymal stem cells derived from adipose tissue (hADMSCs) are a desirable candidate in regenerative medicine. hADMSCs secrete growth factors, cytokines, and chemokines and also express various receptors that are important in cell activation, differentiation, and migration to injured tissue. We showed that the expression level of chemokine receptor CXCR6 was significantly increased by ~2.5-fold in adipogenic-differentiated cells (Ad), but not in osteogenic-differentiated cells (Os) when compared with hADMSCs. However, regulation of CXCR6 expression on hADMSCs by using lentiviral particles did not affect the differentiation potential of hADMSCs. Increased expression of CXCR6 on Ad was mediated by both receptor recycling, which was in turn regulated by secretion of CXCL16, and de novo synthesis. The level of soluble CXCL16 was highly increased in both Ad and Os in particular, which inversely correlates with the expression on a transmembrane-bound form of CXCL16 that is cleaved by disintegrin and metalloproteinase. We concluded that the expression of CXCR6 is regulated by receptor degradation or recycling when it is internalized by interaction with CXCL16 and by de novo synthesis of CXCR6. Overall, our study may provide an insight into the molecular mechanisms of the CXCR6 reciprocally expressed on differentiated cells from hADMSCs.

CXCL16/CXCR6 interaction promotes endometrial decidualization via the PI3K/AKT pathway

Decidualization renders the endometrium transiently receptive to an implanting blastocyst although the underlying mechanisms remain incompletely understood. The aim of this study was to determine the role of chemokine CXCL16 and its receptor CXCR6 in the decidualization during pregnancy. Here, the expression of CXCL16 was investigated in endometrial tissues, decidua and placenta in this study. Compared with endometrial tissue, protein expression of CXCL16 was significantly higher in tissues from the fertile control samples, especially in villus. Meanwhile, the primary trophoblast cells and decidual stromal cells (DSCs) secreted more CXCL16 and expressed higher CXCR6 compared to endometrial stromal cells (ESCs) in vitro. Stimulation with the inducer of decidualization (8-bromoadenosine 3',5'-cyclic with medroxyprogesterone acetate, 8-Br-cAMP plus MPA) significantly upregulated the expression of CXCL16 and CXCR6 in ESCs in vitro. After treatment with exogenous recombinant human CXCL16 (rhCXCL16) or trophoblast-secreted CXLC16, decidualised ESCs showed a significant decidual response, mainly characterised by increased prolactin (PRL) secretion. Simultaneously, PI3K/PDK1/AKT/Cyclin D1 pathway in decidualised ESCs were activated by rhCXCL16, and AKT inhibitor GS 690693 abolished the PRL secretion of ESCs that was triggered by rhCXCL16. Finally, the impaired CXCL16/CXCR6 expression could be observed at the maternal-foetal interface from patients who have experienced spontaneous abortion. This study suggests that the CXCL16/CXCR6 axis contributes to the progression of ESC decidualization by activating PI3K/PDK1/AKT/Cyclin D1 pathway. It unveils a new paradigm at the maternal-foetal interface in which CXCL16 is an initiator for the molecular crosstalk that enhances decidualization of ESCs.

Investigation of human trophoblast invasion in vitro

BACKGROUND

In humans, inadequate trophoblast invasion into the decidua is associated with the 'great obstetrical syndromes' which include pre-eclampsia, foetal growth restriction (FGR) and stillbirth. The mechanisms regulating invasion remain poorly understood, although interactions with the uterine environment are clearly of central importance. Extravillous trophoblast (EVT) cells invade the uterus and transform the spiral arteries. Progress in understanding how they invade has been limited due to the lack of good in vitro models. Firstly, there are no non-malignant cell lines that have an EVT phenotype. Secondly, the invasion assays used are of limited use for the small numbers of primary EVT available from first-trimester placentas. We discuss recent progress in this field with the generation of new EVT lines and invasion assays using microfluidic technology.

OBJECTIVE AND RATIONALE

Our aim is to describe the established models used to study human trophoblast invasion in vivo and in vitro. The difficulties of obtaining primary cells and cell lines that recapitulate the phenotype of EVT are discussed together with the advantages and pitfalls of the different invasion assays. We compare these traditional end point assays to microfluidic assays where the dynamics of migration can be measured.

SEARCH METHODS

Relevant studies were identified by PubMed search, last updated on February 2020. A search was conducted to determine the number of journal articles published using the cell lines JEG-3, BeWo, JAR, HTR-8/Svneo, Swan-71 and primary human extravillous trophoblast in the last 5 years.

OUTCOMES

Deep trophoblast invasion into the maternal decidua is a particular feature of human pregnancy. This invasion needs to be finely regulated to allocate resources between mother and baby. A reliable source of EVT is needed to study in vitro how the uterine environment regulates this process. First, we critically discuss the issues with the trophoblast cell lines currently used; for example, most of them lack expression of the defining marker of EVT, HLA-G. Recently, advances in human stem cell and organoid technology have been applied to extraembryonic tissues to develop trophoblast cell lines that can grow in two (2D) and three dimensions (3D) and differentiate to EVT. This means that the 'trophoblast' cell lines currently in use should rapidly become obsolete. Second, we critically discuss the problems with assays to study trophoblast invasion. These lack physiological relevance and have simplified migration dynamics. Microfluidic assays are a powerful tool to study cell invasion because they require only a few cells, which are embedded in 3D in an extracellular matrix. Their major advantage is real-time monitoring of cell movement, enabling detailed analysis of the dynamics of trophoblast migration.

WIDER IMPLICATIONS

Trophoblast invasion in the first trimester of pregnancy remains poorly understood despite the importance of this process in the pathogenesis of pre-eclampsia, FGR, stillbirth and recurrent miscarriage. The new technologies described here will allow investigation into this critical process.

The chemokine CXCL16 can rescue the defects in insulin signaling and sensitivity caused by palmitate in C2C12 myotubes

In obesity, macrophages infiltrate peripheral tissues and secrete pro-inflammatory cytokines that impact local insulin sensitivity. Lipopolysaccharide (LPS) and the saturated fatty acid (FA) palmitate polarise macrophages towards a pro-inflammatory phenotype in vitro and indirectly cause insulin resistance (IR) in myotubes. In contrast, unsaturated FAs confer an anti-inflammatory phenotype and counteract the actions of palmitate. To explore paracrine mechanisms of interest, J774 macrophages were exposed to palmitate ± palmitoleate or control medium and the conditioned media generated were screened using a cytokine array. Of the 62 cytokines examined, 8 were significantly differentially expressed following FA treatments. Notably, CXCL16 secretion was downregulated by palmitate. In follow-up experiments using ELISAs, this downregulation was confirmed and reversed by simultaneous addition of palmitoleate or oleate, while LPS also diminished CXCL16 secretion. To dissect potential effects of CXCL16, C2C12 myotubes were treated with palmitate to induce IR, recombinant soluble CXCL16 (sCXCL16), combined treatment, or control medium. Palmitate caused the expected reduction of insulin-stimulated Akt activation and glycogen synthesis, whereas simultaneous treatment with sCXCL16 attenuated these effects. These data indicate a putative role for CXCL16 in preservation of Akt activation and insulin signaling in the context of chronic low-grade inflammation in skeletal muscle.

The role of CXC chemokine ligand 16 in physiological and pathological pregnancies

The survival and development of a semi-allogeneic fetus during pregnancy require the involvement of a series of cytokines and immune cells. Chemokines are a type of special cytokine those were originally described as having a role in leukocyte trafficking. CXC chemokine ligand (CXCL) 16 is a member of the chemokine family, and CXC chemokine receptor (CXCR) 6 is its sole receptor. Emerging evidence has shown that CXCL16/CXCR6 is expressed at the maternal-fetal interface, by cell types that include trophoblast cells, decidual stroma cells, and decidual immune cells (eg, monocytes, γδT cells, and natural killer T (NKT) cells). The regulation of expression of CXCL16 is quite complex, and this process involves a multitude of factors. CXCL16 exerts a critical role in the establishment of a successful pregnancy through a series of molecular interactions at the maternal-fetal interface. However, an abnormal expression of CXCL16 is associated with certain pathological states associated with pregnancy, including recurrent miscarriage, pre-eclampsia, and gestational diabetes mellitus (GDM). In the present review, the expression and pleiotropic roles of CXCL16 under conditions of physiological and pathological pregnancy are systematically discussed.

Formyl peptide receptor-2 is decreased in foetal growth restriction and contributes to placental dysfunction

STUDY QUESTION

What is the association between placental formyl peptide receptor 2 (FPR2) and trophoblast and endothelial functions in pregnancies affected by foetal growth restriction (FGR)?

SUMMARY ANSWER

Reduced FPR2 placental expression in idiopathic FGR results in significantly altered trophoblast differentiation and endothelial function in vitro.

WHAT IS KNOWN ALREADY

FGR is associated with placental insufficiency, where defective trophoblast and endothelial functions contribute to reduced feto-placental growth.

STUDY DESIGN, SIZE, DURATION

The expression of FPR2 in placental tissues from human pregnancies complicated with FGR was compared to that in gestation-matched uncomplicated control pregnancies (n = 25 from each group). Fpr2 expression was also determined in placental tissues obtained from a murine model of FGR (n = 4). The functional role of FPR2 in primary trophoblasts and endothelial cells in vitro was assessed in diverse assays in a time-dependent manner.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Placentae from third-trimester pregnancies complicated by idiopathic FGR (n = 25) and those from gestation-matched pregnancies with appropriately grown infants as controls (n = 25) were collected at gestation 27-40 weeks. Placental tissues were also collected from a spontaneous CBA/CaH × DBA/2 J murine model of FGR. Placental FPR2/Fpr2 mRNA expression was determined by real-time PCR, while protein expression was examined by immunoblotting and immunohistochemistry. siRNA transfection was used to silence FPR2 expression in primary trophoblasts and in human umbilical vein endothelial cells (HUVEC), and the quantitation of cytokines, chemokines and apoptosis was performed following a cDNA array analyses. Functional effects of trophoblast differentiation were measured using HCGB/β-hCG and syncytin-2 expression as well as markers of apoptosis, tumour protein 53 (TP53), caspase 8, B cell lymphoma 2 (BCL2) and BCL associated X (BAX). Endothelial function was assessed by proliferation, network formation and permeability assays.

MAIN RESULTS AND THE ROLE OF CHANCE

Placental FPR2/Fpr2 expression was significantly decreased in FGR placentae (n = 25, P < 0.05) as well as in murine FGR placentae compared to controls (n = 4, P < 0.05). FPR2 siRNA (siFPR2) in term trophoblasts significantly increased differentiation markers, HCGB and syncytin-2; cytokines, interleukin (IL)-6, CXCL8; and apoptotic markers, TP53, caspase 8 and BAX, but significantly reduced the expression of the chemokines CXCL12 and its receptors CXCR4 and CXCR7; CXCL16 and its receptor, CXCR6; and cytokine, IL-10, compared with control siRNA (siCONT). Treatment of HUVECs with siFPR2 significantly reduced proliferation and endothelial tube formation, but significantly increased permeability of HUVECs.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Reduced expression of placental FPR2/Fpr2 was observed in the third trimester at delivery after development of FGR, suggesting that FPR2 is associated with FGR pregnancies. However, there is a possibility that the decreased placental FPR2 observed in FGR may be a consequence rather than a cause of FGR, although our in vitro functional analyses using primary trophoblasts and endothelial cells suggest that FPR2 may have a direct or indirect regulatory role on trophoblast differentiation and endothelial function in FGR.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study linking placental FPR2 expression with changes in the trophoblast and endothelial functions that may explain the placental insufficiency observed in FGR.

STUDY FUNDING/COMPETING INTERESTS

P.M. and P.R.E. received funding from the Australian Institute of Musculoskeletal Science, Western Health, St. Albans, Victoria 3021, Australia. M.L. is supported by a Career Development Fellowship from the National Health and Medical Research Council (NHMRC; Grant no. 1047025). Monash Health is supported by the Victorian Government's Operational Infrastructure Support Programme. The authors declare that there is no conflict of interest in publishing this work.

Uterine responses to early pre-attachment embryos in the domestic dog and comparisons with other domestic animal species

In the dog, there is no luteolysis in the absence of pregnancy. Thus, this species lacks any anti-luteolytic endocrine signal as found in other species that modulate uterine function during the critical period of pregnancy establishment. Nevertheless, in the dog an embryo-maternal communication must occur in order to prevent rejection of embryos. Based on this hypothesis, we performed microarray analysis of canine uterine samples collected during pre-attachment phase (days 10-12) and in corresponding non-pregnant controls, in order to elucidate the embryo attachment signal. An additional goal was to identify differences in uterine responses to pre-attachment embryos between dogs and other mammalian species exhibiting different reproductive patterns with regard to luteolysis, implantation, and preparation for placentation. Therefore, the canine microarray data were compared with gene sets from pigs, cattle, horses, and humans. We found 412 genes differentially regulated between the two experimental groups. The functional terms most strongly enriched in response to pre-attachment embryos related to extracellular matrix function and remodeling, and to immune and inflammatory responses. Several candidate genes were validated by semi-quantitative PCR. When compared with other species, best matches were found with human and equine counterparts. Especially for the pig, the majority of overlapping genes showed opposite expression patterns. Interestingly, 1926 genes did not pair with any of the other gene sets. Using a microarray approach, we report the uterine changes in the dog driven by the presence of embryos and compare these results with datasets from other mammalian species, finding common-, contrary-, and exclusively canine-regulated genes.

Trophoblast-Derived CXCL16 Decreased Granzyme B Production of Decidual γδ T Cells and Promoted Bcl-xL Expression of Trophoblasts

BACKGROUND

Decidual γδ T cells are known to regulate the function of trophoblasts at the maternal-fetal interface; however, little is known about the molecular mechanisms of cross talk between trophoblast cells and decidual γδ T cells.

METHODS

Expression of chemokine C-X-C motif ligand 6 (CXCL16) and its receptor CXCR6 was evaluated in first-trimester human villus and decidual tissues by immunohistochemistry. γδ T cells were isolated from first-trimester human deciduae and cocultured with JEG3 trophoblast cells. Cell proliferation and apoptosis-related molecules, together with cytotoxicity factor and cytokine production, were measured by flow cytometry analysis.

RESULTS

Expression of CXCL16 and CXCR6 was reduced at the maternal-fetal interface in patients who experienced unexplained recurrent spontaneous abortion as compared to healthy pregnancy women. With the administration of pregnancy-related hormones or coculture with JEG3 cells, CXCR6 expression was upregulated on decidual γδ T cells. CXCL16 derived from JEG3 cells caused a decrease in granzyme B production of decidual γδ T cells. In addition, decidual γδ T cells educated by JEG3-derived CXCL16 upregulated the expression of Bcl-xL in JEG3 cells.

CONCLUSION

This study suggested that the CXCL16/CXCR6 axis may contribute to maintaining normal pregnancy by reducing the secretion of cytotoxic factor granzyme B of decidual γδ T cells and promoting the expression of antiapoptotic marker Bcl-xL of trophoblasts.

XCL1-XCR1 pathway promotes trophoblast invasion at maternal-fetal interface by inducing MMP-2/MMP-9 activity

PROBLEM

Certain chemokines with their receptors can promote or inhibit trophoblast cell migration and invasion in human first-trimester placenta. Whether the lymphotactin (Lptn; XCL1)-XC chemokine receptor 1 (XCR1) chemokine pathway affects trophoblast cell migration and invasion in human first-trimester placenta remains unclear.

METHOD OF STUDY

The expression pattern of chemokine XCL1 and its receptor XCR1 was detected in human first-trimester by qRT-PCR, and the effect of recombinant human XCL1 (rhXCL1) on trophoblast cell function was tested by wound healing and Transwell assays. Matrix metalloproteinase (MMP) activity in trophoblast cells treated with rhXCL1 was assessed via qRT-PCR and gelatin zymography.

RESULTS

Abundant XCR1 mRNA was expressed in the first-trimester decidua and villi. XCL1 and XCR1 mRNA were expressed at a higher level in the first-trimester than in the term placenta. RhXCL1 promoted trophoblast cell migration and invasion by increasing MMP-9 and MMP-2 activity and that of the MMP-2/tissue inhibitor of metalloproteinases 2 (TIMP-2) complex via the phosphatidylinositol 3-kinase (PI3K)/AKT kinase (AKT), mitogen-activated protein kinase (MEK), and JUN N-terminal kinase (JNK) signaling pathways.

CONCLUSION

XCL1-XCR1 chemokine pathway promotes trophoblast invasion by increasing matrix metalloproteinase activity in human first-trimester placenta.

Analysis of cysteine-X-cysteine motif chemokine ligands 9, 10, and 11, their receptor CXCR3, and their possible role on the recruitment of immune cells at the maternal-conceptus interface in pigs

Chemokines play critical roles in the establishment and maintenance of pregnancy in animals. Cysteine-X-cysteine motif chemokine ligand 9 (CXCL9), CXCL10, and CXCL11 are involved in recruiting immune cells by binding to their shared receptor, CXC receptor 3 (CXCR3), in a variety of tissues. This study examined the expression and regulation of chemokines CXCL9, CXCL10, and CXCL11, their receptor CXCR3, and their role at the maternal-conceptus interface in pigs. The endometrium expressed CXCL9, CXCL10, CXCL11, and CXCR3 stage specifically during pregnancy, with the greatest abundance on Day 15 of pregnancy. It was noted that their expression was primarily localized to stromal cells, endothelial cells, or vascular smooth muscle cells in the endometrium. Interferon-γ increased the abundance of CXCL9, CXCL10, CXCL11 mRNAs, but not CXCR3, in endometrial explants. Furthermore, recombinant CXCL9 (rCXCL9), rCXCL10, and rCXCL11 proteins increased migration of cultured peripheral blood mononuclear cells (PBMCs) in a dose-dependent manner. Recombinant CXCL9 and rCXCL10 caused migration of CD4+, CD8+, CD4+CD8+ T cells, and natural killer (NK) cells, and rCXCL11 increased migration of CD4+ T and NK cells in PBMCs. The present study demonstrated that interferon-γ-induced CXCL9, CXCL10, and CXCL11, and their receptor CXCR3 were expressed in the uterus in stage- and cell-type specific manners and increased the migration of T and NK cells, which showed the greatest endometrial infiltration on Day 15 of pregnancy. These results suggest that CXCL9, CXCL10, and CXCL11 may play an important role in the recruitment of immune cells into the endometrium during the implantation period in pigs.

Trophoblast-derived CXCL16 induces M2 macrophage polarization that in turn inactivates NK cells at the maternal-fetal interface

Decidual macrophages (dMΦ) are distinct from the conventional macrophages present in other tissues and express M2 macrophage markers, but the molecular mechanisms of formation and the roles of M2 MΦ during pregnancy have not been completely elucidated. The crosstalk between decidual natural killer cells (dNK) and dMΦ plays an important role in the maintenance of maternal-fetal immune tolerance. Here, CXCL16 derived from first-trimester trophoblast cells induces the polarization of human M2 macrophages. The M2 MΦ polarized by CXCL16 exhibit decreased interleukin-15 production, which facilitates the inactivation of NK cells. The cytotoxicity of NK cells is attenuated by the CXCL16-polarized M2 MΦ. The data shown in the present study provide evidence to support the hypothesis that CXCL16 secreted by trophoblast cells is a key molecule involved in decidual M2 MΦ polarization, which in turn regulates the killing ability of NK cells, thereby contributing to the homeostatic and immune-tolerant milieu required for successful fetal development.

Chlamydia trachomatis infection of human endometrial stromal cells induces defective decidualisation and chemokine release

Miscarriage affects ~20% of pregnancies and maternal infections account for ~15% of early miscarriages. Chlamydia trachomatis (Ct) has been associated with miscarriage but the underlying mechanisms are unknown. Successful implantation requires endometrial stromal cell (ESC) decidualisation. Maintenance of pregnancy requires angiogenesis, establishment of the correct cellular milieu and trophoblast invasion, all of which involve the action of chemokines. Our objective was to determine whether Ct infection impacts upon ESC decidualisation and chemokine secretion. Human primary ESC were decidualised in-vitro, infected with Ct serovar E, and changes in expression of genes of interest were measured using RT-PCR, proteomic array and ELISA. We demonstrate for the first time that Ct can infect and proliferate in ESC. Expression of the decidualisation marker prolactin was decreased in Ct-infected ESC at both mRNA and protein levels. Ct infection altered the chemokine profile of decidualised ESC as shown by proteomic array. Chemokines CXCL12 and CXCL16, important for trophoblast invasion, were analysed further and expression was reduced in infected decidualised cells at mRNA and protein levels. Our data indicate that Ct infection of ESC impairs decidualisation and alters chemokine release. These findings at least partially explain how Ct infection could result in adverse pregnancy outcomes.

Association between CXCL16/CXCR6 expression and the clinicopathological features of patients with non-small cell lung cancer

Lung cancer is a major cause of morbidity and mortality worldwide, therefore identifying biomarkers for the early detection, grading or postoperative follow-up of lung cancer is of clinical significance. In the present study, expression of lung tissue (t)-CXCL16 and t-CXCR6 was examined in 58 patients with non-small cell lung cancer (NSCLC) using immunohistochemical staining, and serum (s)-CXCL16 levels were detected in 58 patients with NSCLC and in 32 normal volunteers using an ELISA. A follow-up was performed every 4 months between January 2014 and January 2015. Compared with the normal volunteers, the s-CXCL16 concentration in patients with NSCLC significantly increased (329.47±135.38 vs. 572.82±116.05 pg/ml, respectively; P<0.001). When grouped according to TNM stage, the expression of t-CXCL16 (60 vs. 85.71%; P=0.029), t-CXCR6 (53.33 vs. 78.57%; P=0.043) and s-CXCL16 (26.67 vs. 57.14%, P=0.019) in the stage I-II subgroup was significantly lower compared with that of the stage III-IV subgroup. The positive expression rate of t-CXCL16 (91.18%) and t-CXCR6 (79.41%) in the lymph node metastasis subgroup was significantly higher compared with that of the corresponding non-lymph node metastasis subgroup (50 and 45.83%, respectively; P<0.01). Additionally, the positive expression rate of t-CXCL16 in the smoking subgroup was 100%, which was significantly higher compared with that of the non-smoking subgroup (23.81%) (P<0.001). The follow-up and mortality rates were 100% (58/58) and 13.79% (8/58), respectively. Within the time period of the present study, the survival time was 4-18 months, and the mean survival time was 16.6 months. In conclusion, the expression of t-CXCL16 and t-CXCR6 is positively correlated with the TNM stage and lymph node metastasis in patients with NSCLC. Additionally, there was a significant increase in s-CXCL16 levels in patients with NSCLC, suggesting that CXCL16 could be used as a supplementary biomarker for the early detection of NSCLC.

Provocative ideas on human placental biology: A prerequisite for prevention and treatment of neonatal health challenges

A 2-day invite-only meeting on generating "Provocative Ideas on human placental research" was organized on 1-2 December 2015 at the Translational Health Science and Technology Institute, Faridabad. This meeting was sponsored by Department of Biotechnology, Ministry of Science and Technology, Govt. of India. The objectives of this meeting were the critical evaluation of placental physiology and its development. Special emphasis was placed on understanding the consequences and implications of placental development in sustenance of pregnancy and in pregnancy-associated complications such as preeclampsia, intrauterine growth restriction, and preterm birth. This meeting brought together experienced as well as novice clinicians and biologists who have a keen interest in the field of placental biology, including development of new technologies and methods for evaluating the role of placenta in predicting pregnancy outcomes. The meeting primarily focused on (i) high-throughput "-omics" approaches, (ii) maternal nutrition and placental function, (iii) placental infection and inflammation, (iv) real-time evaluation of placental development: tools for placental research, and (v) epidemiologic relevance of placental-based research. Unanimous consensus emerged among the participants to carry out additional work focused on these areas. In this article, we summarize the talks and review the published literature on the above-mentioned niches. As a direct outcome of this meeting, a request for applications has been announced by the Department of Biotechnology, Government of India, for pursuing research in this vital but understudied domain.

Targeting STOX1 in the therapy of preeclampsia

INTRODUCTION

Preeclampsia is a major pregnancy disease, explained partly by genetic predispositions. STOX1, a transcription factor discovered in 2005, was the first gene directly associated with genetic forms of the disease. Alterations of STOX1 expression as well as STOX1 variants have also been associated to Alzheimer's disease. These observations make of this gene a putative therapeutic target. Area covered: Two major isoforms (STOX1A and STOX1B) are encoded by the gene and are theoretically able to compete for the same binding site, while only the most complete (STOX1A) is supposed to be able to activate gene expression. This makes the ratio between STOX1A and STOX1B as well as their position inside the cell (nucleus or cytoplasm) crucial to understand how STOX1 functions. STOX1 appears to have multiple gene targets, especially in pathways connected to inflammation, oxidative stress, and cell cycle. Expert opinion: STOX1-directed therapies, could be directed either towards its targets (genes or pathways), or directly at STOX1. For this the addressing of STOX1 to various cell compartments could theoretically be modified; also it could be possible of altering the balance between the two isoforms, through selectively inhibiting one of them, possibly improving the outcomes in severe preeclampsia.

The roles of serum CXCL16 in circulating Tregs and gastrointestinal stromal tumor cells

Gastrointestinal stromal tumors (GIST) are the most common sarcomas of the digestive system. Abnormal expression of CXCL16 and its sole receptor, CXCR6, has been demonstrated in many cancers. However, no studies have shown the relationship between CXCL16 or CXCR6 expression and GIST. In this study, we detected CXCL16 and CXCR6 expression in GIST patient samples by using immunohistochemistry analysis and Western blot analysis. Serum CXCL16 level was determined by using enzyme-linked immunosorbent assay. Circulating Tregs were isolated by using flow cytometry. MTT assay, cell cycle assay, and transwell assay were used to test the effects of recombinant CXCL16 on Tregs and GIST cells in vitro. The levels of CXCL16 and CXCR6 protein were higher in cancer tissues than in normal tissues. Serum CXCL16 level and circulating Tregs were higher in GIST patients than that in the healthy volunteers. CXCL16, CXCR6, serum CXCL16, and circulating Tregs were significantly associated with a decreased survival time of patients. Relative to control cells, high concentration recombinant CXCL16 treated Tregs and GIST cells exhibited lower proliferation and mobility rates as assessed by MTT assay and transwell assay, respectively. Taken together, CXCL16 was observed to mediate the inhibitory effects in Tregs and GIST cells, and these involved suppression of the MEK/ERK signaling pathway.

CXCR6 expression in non-small cell lung carcinoma supports metastatic process via modulating metalloproteinases

Lung cancer (LuCa) is the leading cause of cancer-related deaths worldwide regardless of the gender. High mortality associated with LuCa is due to metastasis, molecular mechanisms of which are yet to be defined. Here, we present evidence that chemokine receptor CXCR6 and its only natural ligand, CXCL16, are significantly expressed by non-small cell lung cancer (NSCLC) and are involved in the pathobiology of LuCa. CXCR6 expression was significantly higher in two subtypes of NSCLC (adenocarcinomas-ACs and squamous cell carcinoma-SCCs) as compared to non-neoplastic tissue. Additionally, serum CXCL16 was significantly elevated in LuCa cases as compared to healthy controls. Similar to CXCR6 tissue expression, serum level of CXCL16 in AC patients was significantly higher than SCC patients. Biological significance of this axis was validated using SCC and AC cell lines. Expression of CXCR6 was higher in AC cells, which also showed higher migratory and invasive potential than SCC. Differences in migratory and invasive potential between AC and SCC were due to differential expression of metalloproteinases following CXCL16 stimulation. Hence, our findings suggest clinical and biological significance of CXCR6/CXCL16 axis in LuCa, which could be used as potential prognostic marker and therapeutic target.

Intrauterine trophoblast migration: A comparative view of humans and rodents

Trophoblast migration and invasion through the decidua and maternal uterine spiral arteries are crucial events in placentation. During this process, invasive trophoblast replace vascular endothelial cells as the uterine arteries are remodeled to form more permissive vessels that facilitate adequate blood flow to the growing fetus. Placentation failures resulting from either extensive or shallow trophoblastic invasion can cause pregnancy complications such as preeclampsia, intrauterine growth restriction, placenta creta, gestational trophoblastic disease and even maternal or fetal death. Consequently, the use of experimental animal models such as rats and mice has led to great progress in recent years with regards to the identification of mechanisms and factors that control trophoblast migration kinetics. This review aims to perform a comparative analysis of placentation and the mechanisms and factors that coordinate intrauterine trophoblast migration in humans, rats and mice under physiological and pathological conditions.

Molecular Cross-Talk at the Feto-Maternal Interface

Molecular cross-talk at the feto-maternal interface occurs between many different cell types, including uterine leukocytes, extravillous trophoblast cells, and uterine spiral arteries, is essential for the establishment and maintenance of pregnancy. This review concentrates on human pregnancy and examines three main areas in which cross-talk occurs; immune tolerance, regulation of extravillous trophoblast invasion, and remodeling of the uterine spiral arteries.

Chemokine CCL24 promotes the growth and invasiveness of trophoblasts through ERK1/2 and PI3K signaling pathways in human early pregnancy

Chemokine CCL24, acting through receptor CCR3, is a potent chemoattractant for eosinophil in allergic diseases and parasitic infections. We recently reported that CCL24 and CCR3 are co-expressed by trophoblasts in human early pregnant uterus. Here we prove with evidence that steroid hormones estradiol (E), progesterone (P), and human chorionic gonadotropin (hCG), as well as decidual stromal cells (DSCs) could regulate the expression of CCL24 and CCR3 of trophoblasts. We further investigate how trophoblast-derived CCL24 mediates the function of trophoblasts in vitro, and conclude that CCL24/CCR3 promotes the proliferation, viability and invasiveness of trophoblasts. In addition, analysis of the downstream signaling pathways of CCL24/CCR3 show that extracellular signal-regulated kinases (ERK1/2) and phosphoinositide 3-kinase (PI3K) pathways may contribute to the proliferation, viability and invasiveness of trophoblasts by activating intracellular molecules Ki67 and matrix metallopeptidase 9 (MMP9). However, we did not observe any inhibitory effect on trophoblasts when blocking c-Jun N-terminal kinase (JNK) or p38 pathways. In conclusion, our data suggests that trophoblast-derived CCL24 at the maternal-fetal interface promotes trophoblasts cell growth and invasiveness by ERK1/2 and PI3K pathways. Meanwhile, pregnancy-related hormones (P and hCG), as well as DSCs could up-regulate CCL24/CCR3 expression in trophoblasts, which may indirectly influence the biological functions of trophoblasts. Thus, our results provide a possible explanation for the growth and invasion of trophoblasts in human embryo implantation.

Inconformity of CXCL3 plasma level and placenta expression in preeclampsia and its effect on trophoblast viability and invasion

As a member of the chemokine family, CXCL3 was previously known to participate in many pathophysiological events. However, whether CXCL3 stimulates trophoblast invasion as a key process of preeclampsia pathogenesis remains largely unknown. Therefore, the aim of this study was to investigate this hypothesis and determine the effect of CXCL3 on the first trimester trophoblast. Seventy gravidas were included in this study. ELISA was used to detect CXCL3 plasma levels on preeclampsia and normal pregnant groups. CXCL3 protein and mRNA levels were detected via Western blot and real-time quantitative PCR analysis after immunolocalized in human placenta. Moreover, the CXCL3 function in HTR-8/Svneo was analyzed via WST-1 assay, flow cytometry and invasion test. The plasma CXCL3 level in preeclampsia was significantly higher than that in normal pregnancy. CXCL3 expression was observed in the cytoplasm of placental trophoblasts and vascular endothelium in all groups without significant difference between maternal and fetal sides. In addition, placenta CXCL3 expression in severe preeclampsia was significantly lower than those in normal and mild PE groups. Moreover, exogenous CXCL3 can promote the proliferation and invasion of HTR-8/Svneo; however, its effect on apoptosis remains unclear. In summary, a significant abnormality of plasma CXCL3 level and placental CXCL3 expression was discovered in severe preeclampsia; CXCL3 had a function in trophoblast invasion, which indicated its participation in shallow implantation. Therefore CXCL3 might be involved in severe preeclampsia pathogenesis.

The integrative roles of chemokines at the maternal-fetal interface in early pregnancy

Embryos express paternal antigens that are foreign to the mother, but the mother provides a special immune milieu at the fetal-maternal interface to permit rather than reject the embryo growth in the uterus until parturition by establishing precise crosstalk between the mother and the fetus. There are unanswered questions in the maintenance of pregnancy, including the poorly understood phenomenon of maternal tolerance to the allogeneic conceptus, and the remarkable biological roles of placental trophoblasts that invade the uterine wall. Chemokines are multifunctional molecules initially described as having a role in leukocyte trafficking and later found to participate in developmental processes such as differentiation and directed migration. It is increasingly evident that the gestational uterine microenvironment is characterized, at least in part, by the differential expression and secretion of chemokines that induce selective trafficking of leukocyte subsets to the maternal-fetal interface and regulate multiple events that are closely associated with normal pregnancy. Here, we review the expression and function of chemokines and their receptors at the maternal-fetal interface, with a special focus on chemokine as a key component in trophoblast invasiveness and placental angiogenesis, recruitment and instruction of immune cells so as to form a fetus-supporting milieu during pregnancy. The chemokine network is also involved in pregnancy complications.

CXCL16 and CXCR6 are coexpressed in human lung cancer in vivo and mediate the invasion of lung cancer cell lines in vitro

Despite advances in early diagnosis and multimodality therapy for cancers, most of lung cancer patients have been locally advanced or metastatic at the time of diagnosis, suggesting the highly progressive characteristic of lung cancer cells. The mechanisms underling invasiveness and metastasis of lung cancer are yet to be elucidated. In the present study, immunohistochemistry was performed to detect the expression of CXCL16-CXCR6 in human lung cancer tissues. It was demonstrated that similar to CXCL12 and CXCR4, CXCL16 and CXCR6 were also coexpressed in human primary lung cancer tissues. After confirming the functional existence of CXCL16 and CXCR6 protein in A549, 95D and H292 cells by ELSA and flow cytometry analysis, we further explored the significance of CXCL16-CXCR6 axis in the biological functions of lung cancer cell lines in vitro. It was found that CXCL16 had no effects on the PCNA (proliferating cell nuclear antigen) expression of A549, 95D and H292 cells. However, both exogenous CXCL16 and CM (conditioned medium from A549, 95D or H292) significantly improved the in vitro viability and invasion of three lung cancer cell lines. The neutralizing antibody to CXCL16 or down-regulation of CXCR6 was able to inhibit the increased viability and invasiveness of A549, 95D and H292 cells stimulated by CXCL16 or CM. Our results imply that CXCL16-CXCR6 axis is involved in the regulation of viability and invasion rather than PCNA expression of lung caner cells, which opens the door for better understanding the mechanisms of lung tumor progression and metastasis.

Beyond pregnancy: modulation of trophoblast invasion and its consequences for fetal growth and long-term children's health

Invasion of extravillous trophoblast cells (EVTs) into the maternal tissues is a key step in the development of a successful pregnancy, excessive and insufficient EVT invasion being associated with pregnancy complications. These pregnancy complications include preeclampsia and fetal growth restriction, both of which are associated with maternal and fetal morbidity and mortality at the time of birth and with increased risk of cardiovascular disease, diabetes and obesity in adult life for infants born from these conditions. In addition, women who develop preeclampsia are also at a greater risk of cardiovascular disease in later life. Many factors, protein and environmental, have been shown to both up- and down-regulate this process in vitro via different mechanisms. The redundancy observed in the regulation of this system suggests that dysregulation of one factor may not contribute to the pathological conditions of EVT invasion and that the relative local concentrations of many different factors may be more important. This review article explores the possibility that the modulation of EVT invasion as a therapeutic target for pregnancies affected by preeclampsia and fetal growth restriction may not be possible or needs to concentrate on the modulation of cell activity as a whole and not of one particular factor.

CXCL16 in kidney and cardiovascular injury

CXC chemokine ligand 16 (CXCL16) is a CXC soluble chemokine, an adhesion molecule and a cell surface scavenger receptor. CXCL16 regulates inflammation, tissue injury and fibrosis. Parenchymal renal cells, vascular wall cells, leukocytes and platelets express and/or release CXCL16 under the regulation of inflammatory mediators. CXCL16 expression is increased in experimental and human nephropathies. Targeting CXCL16 protected from experimental glomerular injury or interstitial fibrosis. Conflicting results were reported for experimental cardiovascular injury. High circulating CXCL16 levels are associated to human kidney and cardiovascular disease and urinary CXCL16 may increase in kidney injury. In conclusion, mounting evidence suggests a role of CXCL16 in kidney and cardiovascular disease. However, a better understanding is still required before exploring CXCL16 targeting in the clinic.

Immunological modes of pregnancy loss: inflammation, immune effectors, and stress

Inflammatory immune response plays a key role in reproductive failures such as multiple implantation failures (MIF), early pregnancy loss, and recurrent pregnancy losses (RPL). Cellular immune responses particularly mediated by natural killer (NK), and T cells are often dysregulated in these conditions. Excessive or inappropriate recruitment of peripheral blood NK cells to the uterus may lead to cytotoxic environment in utero, in which proliferation and differentiation of trophoblast is hampered. In addition, inadequate angiogenesis by uterine NK cells often leads to abnormal vascular development and blood flow patterns, which, in turn, leads to increased oxidative stress or ischemic changes in the invading trophoblast. T-cell abnormalities with increased Th1 and Th17 immunity, and decreased Th2 and T regulatory immune responses may play important roles in RPL and MIF. A possible role of stress in inflammatory immune response is also reviewed.

Impaired decidual natural killer cell regulation of vascular remodelling in early human pregnancies with high uterine artery resistance

During human pregnancy, natural killer (NK) cells accumulate in the maternal decidua, but their specific roles remain to be determined. Decidual NK (dNK) cells are present during trophoblast invasion and uterine spiral artery remodelling. These events are crucial for successful placentation and the provision of an adequate blood supply to the developing fetus. Remodelling of spiral arteries is impaired in the dangerous pregnancy complication pre-eclampsia. We studied dNK cells isolated from pregnancies at 9–14 weeks' gestation, screened by uterine artery Doppler ultrasound to determine resistance indices which relate to the extent of spiral artery remodelling. dNK cells were able to promote the invasive behaviour of fetal trophoblast cells, partly through HGF. Cells isolated from pregnancies with higher resistance indices were less able to do this and secreted fewer pro-invasive factors. dNK cells from pregnancies with normal resistance indices could induce apoptotic changes in vascular smooth muscle and endothelial cells in vitro, events of importance in vessel remodelling, partly through Fas signalling. dNK cells isolated from high resistance index pregnancies failed to induce vascular apoptosis and secreted fewer pro-apoptotic factors. We have modelled the cellular interactions at the maternal-fetal interface and provide the first demonstration of a functional role for dNK cells in influencing vascular cells. A potential mechanism contributing to impaired vessel remodelling in pregnancies with a higher uterine artery resistance is presented. These findings may be informative in determining the cellular interactions contributing to the pathology of pregnancy disorders where remodelling is impaired, such as pre-eclampsia.

Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

TWEAK (tumor necrosis factor-like weak inducer of apoptosis) activates CXCL16 expression during renal tubulointerstitial inflammation

TWEAK (tumor necrosis factor-like weak inducer of apoptosis) is a TNF superfamily cytokine that activates the fibroblast growth factor-inducible 14 (Fn14) receptor. Transcriptional analysis of experimental kidney tubulointerstitial inflammation showed a correlation between an upregulation of the mRNA for the transmembrane chemokine CXCL16, a T-cell chemoattractant, and Fn14 activation. Exogenous TWEAK increased mouse kidney CXCL16 expression and T-lymphocyte infiltration in vivo, processes inhibited by the NF-κB inhibitor parthenolide. Tubular cell CXCL16 was increased in a nephrotoxic tubulointerstitial inflammation model and neutralizing anti-TWEAK antibodies decreased this CXCL16 expression and lymphocyte infiltration. In human kidney biopsies with tubulointerstitial inflammation, tubular cell CXCL16 and Fn14 expressions were associated with inflammatory infiltrates. TWEAK upregulated CXCL16 mRNA expression in cultured renal tubular cells in an NF-κB-dependent manner and increased soluble and cellular CXCL16 protein. CXCL16 modestly promoted the expression of cytokines in tubular cells expressing its receptor (CXCR6) and appeared to synergize with TWEAK to promote an inflammatory response; however, it did not modulate tubular cell proliferation or survival. Thus, TWEAK upregulates the expression of the chemokine CXCL16 in tubular epithelium and this may contribute to kidney tubulointerstitial inflammation.

The chemokine receptor CXCR4 and its ligand CXCL12 are activated during implantation and placentation in sheep

BACKGROUND

The progression of implantation and placentation in ruminants is complex and is regulated by interplay between sex steroids and local signaling molecules, many of which have immune function. Chemokines and their receptors are pivotal factors in implantation and vascularization of the placenta. Based on known critical roles for chemokine receptor 4 (CXCR4) during early pregnancy in other species, we hypothesized that CXCR4 and its ligand CXCL12 would increase in the endometrium and conceptus in response to implantation in ewes. The objectives of the current study were to determine if CXCL12 and CXCR4 were upregulated in: endometrium from pregnant compared to non-pregnant ewes and in, conceptuses, cotyledons, caruncles and intercaruncular tissue.

METHODS

Tissues were collected from sheep on Days 12, 13, 14, and 15 of either the estrous cycle or pregnancy and from pregnant ewes on Days 35 and 50. Blood samples from jugular and uterine vein were also collected on all days. Conceptuses were collected from mature ewes on Days 13, 15, 16, 17, 21 and 30 of gestation. Real time PCR was used to determine relative mRNA concentrations for CXCL12 and CXCR4 and Western blot analysis was employed to confirm protein concentration.

RESULTS

Differences described are P < 0.05. In the endometrium, CXCR4 mRNA and protein was greater on Day 15 of pregnancy compared to the estrous cycle. CXCL12 and CXCR4 mRNA in conceptuses was greater on Days 21 and 30 compared to earlier days. CXCL12 mRNA was greater in cotyledons on Day 35 compared to Day 50. On Day 35 of gestation, CXCR4 was greater compared to Day 50 in caruncle and intercaruncular tissue. White blood cells obtained from jugular and uterine vein collection had the greatest mRNA concentration of CXCL12 on Day 35 of pregnancy.

CONCLUSIONS

A comprehensive analysis of CXCL12 and CXCR4 expression in fetal and maternal tissues during early pregnancy is reported with noteworthy differences occurring during implantation and placentation in sheep. We interpreted these data to mean that the CXCL12/CXCR4 pathway is activated during implantation and placentation in sheep and is likely playing a role in the communication between trophoblast cells and the maternal endometrium.

Thymic stromal lymphopoietin from trophoblasts induces dendritic cell–mediated regulatory TH2 bias in the decidua during early gestation in humans

Thymic stromal lymphopoietins (TSLPs) play critical roles in dendritic cell–mediated immune responses. In this study, we found that human trophoblasts and decidual epithelial cells in maternal-fetal interface of early placentas express TSLP mRNA and protein, but only trophoblast cells secret soluble TSLP. Human decidual CD1c+ DCs (dDCs) highly express the functional TSLP receptor complex TSLP receptor and interleukin-7 receptor-α. Recombinant human TSLP activates CD1C+ decidual DCs and peripheral monocyte-derived DCs with increased costimulatory molecules, major histocompatibility complex class II, and OX-40L. Human TSLP or supernatants from human trophoblasts specifically stimulate dDCs to highly produce interleukin-10 and TH2-attracting chemokine CCL-17. The TSLP-activated dDCs prime decidual CD4+ T cells for TH2 cell differentiation, involved in maternal-fetal immunotolerance. Interestingly, the protein expression of TSLP in normal pregnancy with significant TH2 bias is much higher than that of miscarriage showing TH1 bias at the maternal-fetal interface. Therefore, human trophoblasts may contribute to maternal-fetal tolerance by instructing dDCs to induce regulatory TH2 bias in human early pregnancy via TSLP.

Bovine pretransfer endometrium and embryo transcriptome fingerprints as predictors of pregnancy success after embryo transfer

Aberrant gene expression in the uterine endometrium and embryo has been the major causes of pregnancy failure in cattle. However, selecting cows having adequate endometrial receptivity and embryos of better developmental competence based on the gene expression pattern has been a greater challenge. To investigate whether pretransfer endometrial and embryo gene expression pattern has a direct relation with upcoming pregnancy success, we performed a global endometrial and embryo transcriptome analysis using endometrial and embryo biopsy technology and the pregnancy outcome information. For this, endometrial samples were collected from Simmental heifers at day 7 and 14 of the estrous cycle, one cycle prior to embryo transfer. In the next cycle, blastocyst stage embryos were transferred to recipients at day 7 of the estrous cycle after taking 30-40% of the blastocyst as a biopsy for transcriptome analysis. The results revealed that at day 7 of the estrous cycle, the endometrial gene expression pattern of heifers whose pregnancy resulting in calf delivery was significantly different compared with those resulting in no pregnancy. These differences were accompanied by qualitative and quantitative alteration of major biological process and molecular pathways. However, the transcriptome difference was minimal between the two groups of animals at day 14 of the estrous cycle. Similarly, the transcriptome analysis between embryos biopsies that resulted in calf delivery and those resulted in no pregnancy revealed a total of 70 differentially expressed genes. Among these, the transcript levels of 32 genes including SPAG17, PF6, UBE2D3P, DFNB31, AMD1, DTNBP1, and ARL8B were higher in embryo biopsies resulting in calf delivery. Therefore, the present study highlights the potential of pretransfer endometrial and embryo gene expression patterns as predictors of pregnancy success in cattle.

Critical growth factors and signalling pathways controlling human trophoblast invasion

Invasion of placental trophoblasts into uterine tissue and vessels is an essential process of human pregnancy and fetal development. Due to their remarkable plasticity invasive trophoblasts fulfil numerous functions, i.e. anchorage of the placenta, secretion of hormones, modulation of decidual angiogenesis/lymphangiogenesis and remodelling of maternal spiral arteries. The latter is required to increase blood flow to the placenta, thereby ensuring appropriate transfer of nutrients and oxygen to the developing fetus. Since failures in vascular changes of the placental bed are associated with pregnancy diseases such as preeclampsia or intrauterine growth restriction, basic research in this particular field focuses on molecular mechanisms controlling trophoblast invasion under physiological and pathological conditions. Throughout the years, an increasing number of growth factors, cytokines and angiogenic molecules controlling trophoblast motility have been identified. These factors are secreted from numerous cells such as trophoblast, maternal epithelial and stromal cells, as well as uterine NK cells and macrophages, suggesting that a complex network of cell types, mediators and signalling pathways regulates trophoblast invasiveness. Whereas essential features of the invasive trophoblast such as expression of critical proteases and adhesion molecules have been well characterised, the interplay between different cell types and growth factors and the cross-talk between distinct signalling cascades remain largely elusive. Similarly, key-regulatory transcription factors committing and differentiating invasive trophoblasts are mostly unknown. This review will summarise our current understanding of growth factors and signal transduction pathways regulating human trophoblast invasion/migration, as well as give insights into novel mechanisms involved in the particular differentiation process.

Chemokine scavenger D6 is expressed by trophoblasts and aids the survival of mouse embryos transferred into allogeneic recipients

Proinflammatory CC chemokines are thought to drive recruitment of maternal leukocytes into gestational tissues and regulate extravillous trophoblast migration. The atypical chemokine receptor D6 binds many of these chemokines and is highly expressed by the human placenta. D6 is thought to act as a chemokine scavenger because, when ectopically expressed in cell lines in vitro, it efficiently internalizes proinflammatory CC chemokines and targets them for destruction in the absence of detectable chemokine-induced signaling. Moreover, D6 suppresses inflammation in many mouse tissues, and notably, D6-deficient fetuses in D6-deficient female mice show increased susceptibility to inflammation-driven resorption. In this paper, we report strong anti-D6 immunoreactivity, with specific intracellular distribution patterns, in trophoblast-derived cells in human placenta, decidua, and gestational membranes throughout pregnancy and in trophoblast disease states of hydatidiform mole and choriocarcinoma. We show, for the first time, that endogenous D6 in a human choriocarcinoma-derived cell line can mediate progressive chemokine scavenging and that the D6 ligand CCL2 can specifically associate with human syncytiotrophoblasts in term placenta in situ. Moreover, despite strong chemokine production by gestational tissues, levels of D6-binding chemokines in maternal plasma decrease during pregnancy, even in women with pre-eclampsia, a disease associated with increased maternal inflammation. In mice, D6 is not required for syngeneic or semiallogeneic fetal survival in unchallenged mice, but interestingly, it does suppress fetal resorption after embryo transfer into fully allogeneic recipients. These data support the view that trophoblast D6 scavenges maternal chemokines at the fetomaternal interface and that, in some circumstances, this can help to ensure fetal survival.

Functional regulation of thymic stromal lymphopoietin on proliferation and invasion of trophoblasts in human first-trimester pregnancy

BACKGROUND

Thymic stromal lymphopoietin (TSLP) is a novel cytokine that triggers the dendritic cell-mediated T(H)2 response and regulatory T cell expansion. The aim of this study is to evaluate whether TSLP and TSLP receptor (TSLPR) are expressed in primary human extravillous trophoblast (EVT), how proimflammatory cytokines (tumor necrosis factor (TNF)-alpha, IL-1beta), T(H)2 and T(H)3 cytokines (IL-4, TGF-beta) and pregnancy-associated hormones regulate TSLP production by EVT and whether the SLP-TSLPR interaction affects the biological behavior of trophoblsts.

METHODS

We assessed TSLP mRNA and protein expression by real-time RT-PCR, ELISA and immunochemistry, respectively. We further investigated effects of TSLP on the proliferation and invasion of trophoblast cells in vitro.

RESULTS

The primary EVTs constitutively expressed TSLP and TSLPR. IL-4 and TNF-alpha or pregnancy-associated hormones result in a significant increase in TSLP mRNA expression and protein release from EVT, and TSLP promotes primary EVT proliferation and invasion in vitro.

CONCLUSIONS

This study has demonstrated that the first-trimester human trophoblast cells express TSLP and TSLPR, that cytokine milieu which mimics the maternal-fetal interface modulates expression of TSLP in trophoblast and that TSLP stimulates trophoblast proliferation and invasion. This suggests that TSLP plays an important role in human EVT invasion and placentation in human early pregnancy.

NME1 at the human maternal-fetal interface downregulates titin expression and invasiveness of trophoblast cells via MAPK pathway in early pregnancy

Nometastatic gene 23-H1 (NME1, also known as nm23-H1) is a wide-spectrum tumor metastasis suppressor gene that plays an important role in suppressing the invasion and metastasis of tumor cells. It has been demonstrated that NME1 is also expressed in human first-trimester placenta, but its function at maternal-fetal interface is not clear. The present study aimed to elucidate the biological function of NME1 at the maternal-fetal interface, especially on invasion of the human extravillous cytotrophoblasts (EVCTs). NME1 has been identified in both human trophoblast cells and decidual stromal cells (DSCs) in early pregnancy. We have proved that NME1 silencing in vitro increases the titin protein translation in the invasive EVCTs. Moreover, NME1 can inactivate the phospho-extracellular signal-regulated kinase 1/2 (P-ERK1/2) in trophoblasts in a time-dependent manner, and U0126, an inhibitor of MAPK/ERK, can inhibit partly the enhanced invasiveness and titin expression in trophoblasts induced by NME1 silencing. Interestingly, the expression of NME1 in either villi or decidua is higher significantly in miscarriage than that of the normal early pregnancy. These findings first reveal that the NME1 expressed in trophoblasts and DSCs controls the inappropriate invasion of human first-trimester trophoblast cells via MAPK/ERK1/2 signal pathway, and the overexpression of NME1 at maternal-fetal interface leads to pregnancy wastage.