Differential expression of CXCR4 receptor in early and term human placenta

Maternal CXCR4 deletion results in placental defects and pregnancy loss mediated by immune dysregulation

CXCR4 is a key regulator of the development of NK cells and DCs, both of which play an important role in early placental development and immune tolerance at the maternal-fetal interface. However, the role of CXCR4 in pregnancy is not well understood. Our study demonstrates that adult-induced global genetic CXCR4 deletion, but not uterine-specific CXCR4 deletion, was associated with increased pregnancy resorptions and decreased litter size. CXCR4-deficient mice had decreased NK cells and increased granulocytes in the decidua, along with increased leukocyte numbers in peripheral blood. We found that CXCR4-deficient mice had abnormal decidual NK cell aggregates and NK cell infiltration into trophoblast areas beyond the giant cell layer. This was associated with low NK cell expression of granzyme B, a NK cell granule effector, indicative of NK cell dysfunction. Pregnancy failure in these mice was associated with abnormalities in placental vascular development and increased placental expression of inflammatory genes. Importantly, adoptive BM transfer of WT CXCR4+ BM cells into CXCR4-deficient mice rescued the reproductive deficits by normalizing NK cell function and mediating normal placental vascular development. Collectively, our study found an important role for maternal CXCR4 expression in immune cell function, placental development, and pregnancy maintenance.

Evolutionary traits and functional roles of chemokines and their receptors in the male pregnancy of the Syngnathidae

Vertebrates have developed various modes of reproduction, some of which are found in Teleosts. Over 300 species of the Syngnathidae (seahorses, pipefishes and seadragons) exhibit male pregnancies; the males have specialized brood pouches that provide immune protection, nourishment, and oxygen regulation. Chemokines play a vital role at the mammalian maternal-fetal interface; however, their functions in fish reproduction are unclear. This study revealed the evolutionary traits and potential functions of chemokine genes in 22 oviparous, ovoviviparous, and viviparous fish species through comparative genomic analyses. Our results showed that chemokine gene copy numbers and evolutionary rates vary among species with different modes of reproduction. Syngnathidae lost cxcl13 and cxcr5, which are involved in key receptor-ligand pairs for lymphoid organ development. Notably, Syngnathidae have site-specific mutations in cxcl12b and ccl44, suggesting immune function during gestation. Moreover, transcriptome analysis revealed that chemokine gene expression varies among Syngnathidae species with different types of brood pouches, suggesting adaptive variations in chemokine functions among seahorses and their relatives. Furthermore, challenge experiments on seahorse brood pouches revealed a joint immune function of chemokine genes during male pregnancy. This study provides insights into the evolutionary diversity of chemokine genes associated with different reproductive modes in fish.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-023-00205-x.

Sex differences in early and term placenta are conserved in adult tissues

BACKGROUND

Pregnancy complications vary based on the fetus's genetic sex, which may, in part, be modulated by the placenta. Furthermore, developmental differences early in life can have lifelong health outcomes. Yet, sex differences in gene expression within the placenta at different timepoints throughout pregnancy and comparisons to adult tissues remains poorly characterized.

METHODS

Here, we collect and characterize sex differences in gene expression in term placentas (≥ 36.6 weeks; 23 male XY and 27 female XX). These are compared with sex differences in previously collected first trimester placenta samples and 42 non-reproductive adult tissues from GTEx.

RESULTS

We identify 268 and 53 sex-differentially expressed genes in the uncomplicated late first trimester and term placentas, respectively. Of the 53 sex-differentially expressed genes observed in the term placentas, 31 are also sex-differentially expressed genes in the late first trimester placentas. Furthermore, sex differences in gene expression in term placentas are highly correlated with sex differences in the late first trimester placentas. We found that sex-differential gene expression in the term placenta is significantly correlated with sex differences in gene expression in 42 non-reproductive adult tissues (correlation coefficient ranged from 0.892 to 0.957), with the highest correlation in brain tissues. Sex differences in gene expression were largely driven by gene expression on the sex chromosomes. We further show that some gametologous genes (genes with functional copies on X and Y) will have different inferred sex differences if the X-linked gene expression in females is compared to the sum of the X-linked and Y-linked gene expression in males.

CONCLUSIONS

We find that sex differences in gene expression are conserved in late first trimester and term placentas and that these sex differences are conserved in adult tissues. We demonstrate that there are sex differences associated with innate immune response in late first trimester placentas but there is no significant difference in gene expression of innate immune genes between sexes in healthy full-term placentas. Finally, sex differences are predominantly driven by expression from sex-linked genes.

Maternal nutrient restriction and over-feeding during gestation alter expression of key factors involved in placental development and vascularization

Poor maternal nutrition can negatively affect fetal and placental growth and development. However, the mechanism(s) that contribute to altered placenta growth and function are not well understood. We hypothesized that poor maternal diet would impact signaling through the C-X-C motif chemokine ligand (CXCL) 12-CXCL4 axis and/or placental expression of the insulin-like growth factor (IGF) axis. Using our established sheep model of poor maternal nutrition, we examined the effects of restricted- and over-feeding on ewe placentome gene and protein expression. Specifically, ewes were fed a control (CON; 100%), restricted (RES; 60%), or over (OVER; 140%) diet beginning at day 30.2 ± 0.02 of gestation, and samples were collected at days 45, 90, and 135 of gestation, representing periods of active placentation, peak placental growth, and near term, respectively. Placentomes were separated into cotyledon and caruncle, and samples snap frozen. Protein was determined by western blot and mRNA expression by real-time PCR. Data were analyzed by ANOVA and significance determined at P ≤ 0.05. Ewes fed a RES diet had decreased CXCL12 and vascular endothelial growth factor (VEGF), and increased tumor necrosis factor (TNF)α protein compared with CON ewes in caruncle at day 45 (P ≤0.05). In day 45 cotyledon, CXCR7 protein was increased and mTOR was decreased in RES relative to CON (P ≤0.05). At day 90, CXCR4 and CXCR7 were reduced in RES caruncle compared with CON, whereas VEGF was reduced and mTOR increased in cotyledon of RES ewes relative to CON (P ≤0.05). In OVER caruncle, at day 45 CXCR4 and VEGF were reduced and at day 90 CXCR4, CXCR7, and TNFα were reduced in caruncle compared with CON (P ≤0.05). There was no observed effect of OVER diet on protein abundance in the cotyledon (P > 0.05). Expression of IGF-II mRNA was increased in OVER at day 45 and IGFBP-3 was reduced in RES at day 90 in caruncle relative to CON (P ≤0.05). Maternal diet did not alter placentome diameter or weight (P > 0.05). These findings suggest that restricted- and over-feeding negatively impact protein and mRNA expression of key chemokines and growth factors implicated in proper placenta development and function.

Role of chemokines in early pregnancy loss

The present study aimed to compare decidual protein levels and gene expression levels of chemokines between patients with early pregnancy loss and those with voluntary abortion. A total of 15 patients between 6 and 10 gestational weeks, who presented with negative fetal heartbeat to the obstetrics and gynecology outpatient clinics of Gaziosmanpasa Hospital (Yeni Yuzyil University, Istanbul, Turkey) and who had no additional systemic disease and 13 patients between 6 and 10 gestational weeks, who presented with positive fetal heartbeat for voluntary abortion were included in the present study. CX3CL1, CCL17, CXCR4, chemokine ligand 12 (CXCL12) and intercellular adhesion molecule (ICAM)5 protein expression levels were determined by ELISA and gene expression levels by reverse transcription-quantitative PCR in fresh materials recovered after therapeutic curettage. CX3CL1, CCL17, CXCR4, CXCL12 protein levels were significantly higher and ICAM protein level was significantly lower in pregrant women with missed abortion compared with those with voluntary abortion. While the amount of increase in mean CX3CL1, CCL17, CXCR4 and CXCL12 gene expression levels in the tissues of pregnant women with missed abortion was statistically higher than the pregnant women who underwent voluntary abortion, the amount of increase in ICAM5 gene expression was found to be lower (P<0.001) in those with missed abortion. In conclusion, the findings of the present study suggested that CCL17, CX3CL1, CXCL12, CXCR4 and ICAM5 may be associated with missed abortion and may play an important role in placental invasion and the continuation of pregnancy.

Cortisol Dose-Dependently Impairs Migration and Tube-like Formation in a Trophoblast Cell Line and Modulates Inflammatory and Angiogenic Genes

Several stimuli can change maternal hormone levels during pregnancy. These changes may affect trophoblastic cells and modulate the development of the embryo and the placental tissue itself. Changes in cortisol levels are associated with impaired trophoblast implantation and function, in addition to other pregnancy complications. This study aims to analyze the effects of low and high doses of cortisol on an extravillous trophoblast cell line, and the effects of various exposures to this hormone. SGHPL-4 cells were treated with cortisol at five doses (0-1000 nM) and two exposures (continuous: 24 h/day; and intermittent: 2 h/day). In intermittent treatment, cortisol acted mainly as an anti-inflammatory hormone, repressing gene expression of kinin B1 receptors, interleukin-6, and interleukin-1β. Continuous treatment modulated inflammatory and angiogenic pathways, significantly repressing angiogenic factors and their receptors. Cortisol affected cell migration and tube-like structures formation. In conclusion, both continuous and intermittent exposure to cortisol repressed the expression of inflammatory genes, while only continuous exposure repressed the expression of angiogenic genes, suggesting that a sustained increase in the levels of this hormone is more harmful than a high short-term increase. Cortisol also impaired tube-like structures formation, and kinin receptors may be involved in this response.

CXCR4/CXCR7 Protein Expression Levels in Placentas of Patients with Preeclampsia

BACKGROUND Although preeclampsia causes maternal and infantile morbidity and mortality, its pathophysiology is unclear. We aimed to study the correlation between CXC chemokine receptor (CXCR)4 and CXCR7 protein expression levels in the placentas of women with preeclampsia. MATERIAL AND METHODS The study included 42 women who delivered in Wenzhou People's Hospital China from September 2019 to March 2020. There were 3 groups: 13 patients with gestational hypertension, 12 patients with preeclampsia, and 17 patients with normal pregnancy (control). We measured placental CXCR4 and CXCR7 levels with ELISA. We compared differences between groups with t test and ANOVA, and Pearson's correlation was used to test correlations between CXCR4 and CXCR7 protein expression levels and lag time of preeclampsia. RESULTS The preeclampsia and gestational hypertension groups showed statistically higher levels of CXCR4 than did the control group (54.43±10.31, 51.53±9.62 vs 42.81±10.06 ng/g, respectively), with no difference between the preeclampsia and gestational hypertension groups. There were no significant differences in CXCR7 levels between the preeclampsia, gestational hypertension, and control groups. Among patients with preeclampsia, the CXCR4 level was significantly higher in the severe preeclampsia group (systolic blood pressure ³160 and/or diastolic blood pressure ≥90 mmHg) than in the mild hypertension group. CXCR4 and CXCR7 levels were higher in early-onset preeclampsia (<34 weeks) than in late-onset preeclampsia. CXCR4 and CXCR7 levels were not correlated with the lag time of preeclampsia. CONCLUSIONS CXCR4 and CXCR7 protein may play roles in the pathophysiology of preeclampsia.

Comparison of Expression of Chemokine Receptor 4 in Maternal Decidua and Chorionic Villi in Women with Spontaneous Miscarriages and Women Opting for Termination of Viable Pregnancies

Background:

Early pregnancy losses can be a distressing experience both for the parents and the treating clinician. We aim to explore the role of chemokine receptor 4 (CXCR4) in early pregnancy losses by comparing its expression among patients with spontaneous miscarriages and patients undergoing termination of viable pregnancies for unwanted pregnancies.

Aim:

The aim of the study was to investigate the expression of CXCR4 in early pregnancy losses and correlate the various clinical parameters with differential expression of the above receptor in the chorionic villi and maternal decidua.

Study and Setting:

The present study is a case-“control study done in a tertiary care center.

Methodology:

Fifty patients attending outdoor and antenatal clinic of the hospital aged 18-40 years with spontaneous miscarriage under 20 weeks of gestational age were included as cases and compared with fifty females of comparable age group (18-40 years) seeking medical termination of pregnancy as controls. Chorionic villi and decidua obtained from the cases and controls were analyzed for CXCR4 expression.

Statistical Analysis:

The results were analyzed using mean ± standard deviation, percentiles values, Chi-square test, and P value to determine the association of CXCR4 expression in decidua and chorionic villi of cases versus controls.

Results:

CXCR4 expression was significantly downregulated in cases as compared to the controls with P < 0.001. The mean normalized ratio of CXCR4 expression to housekeeping gene (β Actin) expression in the case group was 1.607 ± 1.108 and in the control group, it was 2.506 ± 1.457. There was a strong correlation between the expression of CXCR4 and maternal age. With increasing age, the expression of CXCR4 was more downregulated in both the cases and control groups (P < 0.001). The expression of CXCR4 was elevated in controls as compared to cases in <30 years age group (P = 0.009). CXCR4 expression was higher in primigravida than in multigravida (P = 0.001), and as the number of previous miscarriages increased, the expression of CXCR4 was found to be decreased (P = 0.021).

Conclusion:

CXCR4 expression is significantly reduced in women with spontaneous miscarriages in comparison with viable pregnancies. and possibly, therapies targeted at increasing the expression of CXCR4 can be used as a treatment modality for management of spontaneous miscarriages.

CXCL12 in normal and pathological pregnancies: A review

The survival of allogeneic fetuses during pregnancy is a rather paradoxical phenomenon with a complex mechanism. Chemokine ligand12 (CXCL12) and its receptors CXC chemokine receptor (CXCR)4 and 7 are extensively found in placenta tissues and cells, including trophoblast cells, vascular endothelial cells, and decidual stromal and decidual immune cells (eg, NK cells and regulatory T cells). Evidence has illustrated that the CXClL12/CXCR4/CXCR7 axis could enhance the cross talk at the maternal-fetal interface through multiple processes, such as invasion and placental angiogenesis, which appears to be critical signaling components in placentation and fetal outcome. In addition, an increasing number of studies have demonstrated that the CXCL12/CXCR4/CXCR7 axis also stands out for its pleiotropic roles in several pregnancy-associated diseases (eg, recurrent spontaneous abortion (RSA), pre-eclampsia (PE), and preterm labor). In the present review, the different biological properties and signaling in physiological and pathological pregnancy conditions of CXCL12/CXCR4/CXCR7 axis were discussed, with the aim of obtaining a further understanding of the regulatory mechanisms and highlighting their potential as a target for therapeutic approaches.

Expression and Functional Analysis of CXCL12 and Its Receptors in Human Term Trophoblast Cells

Chemokine CXCL12 and its receptors CXCR4/CXCR7 play a pivotal role in many physiological and pathological situations, while the expression and function in human term trophoblast cells remain largely unknown. In the study, the expression and function of CXCL12 and its receptors CXCR4/CXCR7 in human term trophoblast cells were investigated. Immunocytochemistry and flow cytometry showed that the expression of CXCL12/CXCR4/CXCR7 could be detected in term trophoblast cells while expression level differed. The secretion of CXCL12 in human term trophoblast cells was confirmed by enzyme-linked immunosorbent assay (ELISA). In order to reveal the function of CXCL12, exogenetic recombinant human CXCL12 protein (rhCXCL12) was added to the cultured term trophoblast cells; results showed that cell proliferation ability was increased while cell apoptosis rate was decreased. Moreover, the effects of rhCXCL12 on term trophoblast cells could be diminished or attenuated by antibodies against CXCL12, CXCR4, or CXCR7, respectively. Therefore, these results revealed the important role of CXCL12 on human term trophoblast cells. Our study will provide new insights into understanding the role of CXCL12 on human term trophoblast cells.

Involvement of CXCL12/CXCR4 in the motility of human first-trimester endometrial epithelial cells through an autocrine mechanism by activating PI3K/AKT signaling

Background

CXCL12(chemokine ligand 12, CXCL12) and its receptors CXCR4 are widely expressed in maternal-fetal interface and plays an adjust role in materno-fetal dialogue and immune tolerance during early pregnancy. This study aimed to evaluate the role and mechanism of self-derived CXCL12 in modulating the functions of human first-trimester endometrial epithelial cells (EECs) and to identify the potential protein kinase signaling pathways involved in the CXCL12/CXCR4’s effect on EECs.

Methods

The expression of CXCL12 and CXCR4 in EECs was measured by using immunohistochemistry, immunofluorescence, real-time polymerase chain reaction and enzyme-linked immunosorbent assay. The effects of EEC-conditioned medium (EEC-CM) and recombinant human CXCL12 (rhCXCL12) on EEC migration and invasion in vitro were evaluated with migration and invasion assays. In-cell western blot analysis was used to examine the phosphorylation of protein kinase B (AKT), extracellular regulated protein kinases (ERKs) and phosphatidylinositol 3-kinase (PI3K) after CXCL12 treatment.

Results

CXCL12 and CXCR4 were both expressed in human first-trimester EECs at the mRNA and protein level. Both EEC-CM and rhCXCL12 significantly increased the migration and invasion of EECs (P < 0.05), which could be blocked by neutralizing antibodies against CXCR4 (P < 0.05) or CXCL12 (P < 0.05), respectively. CXCL12 activated both PI3K/AKT and ERK1/2 signaling and CXCR4 neutralizing antibody effectively reduced CXCL12-induced phosphorylation of AKT and ERK1/2. LY294002, a PI3K-AKT inhibitor, was able to reverse the promotive effect of EEC-CM or rhCXCL12 on EEC migration and invasion.

Conclusions

Human first-trimester EECs promoted their own migration and invasion through the autocrine mechanism with CXCL12/CXCR4 axis involvement by activating PI3K/AKT signaling. This study contributes to a better understanding of the epithelium function mediated by chemokine and chemokine receptor during normal pregnancy.

CXCR4 signaling at the ovine fetal-maternal interface regulates vascularization, CD34+ cell presence, and autophagy in the endometrium†

Placenta development is characterized by extensive angiogenesis and vascularization but if these processes are compromised placental dysfunction occurs, which is the underlying cause of pregnancy complications such as preeclampsia and intrauterine growth restriction. Dysregulation of placental angiogenesis has emerged as one of the main pathophysiological features in the development of placental insufficiency and its clinical consequences. The signaling axis initiated by chemokine ligand 12 (CXCL12) and its receptor CXCR4 stimulates angiogenesis in other tissues, and may be central to placental vascularization. We hypothesized that CXCL12-CXCR4 signaling governs the pro-angiogenic placental microenvironment by coordinating production of central angiogenic factors and receptors and regulates endometrial cell survival essential for placental function and subsequent fetal longevity. The CXCR4 antagonist, AMD3100, was used to elucidate the role of CXCL12-CXCR4 signaling regarding uteroplacental vascular remodeling at the fetal-maternal interface. On day 12 postbreeding, osmotic pumps were surgically installed and delivered either AMD3100 or PBS into the uterine lumen ipsilateral to the corpus luteum. On day 20, endometrial tissues were collected, snap-frozen in liquid nitrogen, and uterine horn cross sections preserved for immunofluorescent analysis. In endometrium from ewes receiving AMD3100 infusion, the abundance of select angiogenic factors was diminished, while presence of CD34+ cells increased compared to control ewes. Ewes receiving AMD3100 infusion also exhibited less activation of Akt/mTOR signaling, and elevated LC3B-II, a marker of cellular autophagy in endometrium. This study suggests that CXCL12-CXCR4 signaling governs placental homeostasis by serving as a critical upstream mediator of vascularization and cell viability, thereby ensuring appropriate placental development.

Cigarette Smoking Affects Uterine Receptivity Markers

OBJECTIVE

Smoking negatively affects fertility and the rate of other endometrial diseases. To determine the effect of smoking on endometrial physiology, we evaluated 2 endometrial regulatory cytokines and receptivity markers, C-X-C motif chemokine ligand 12 (CXCL12) and fibroblast growth factor 2 (FGF2), both in vitro and in vivo.

STUDY DESIGN

The human endometrial stromal cell line (HESC) and primary human endometrial stromal cells were treated with cigarette smoking extract (CSE) or with vehicle control. Twenty female mice were randomly assigned to either cigarette smoke (CS) exposure for 8 weeks or to a nonsmoke (NS) group that received room air. Immunohistochemical analysis of CXCL12 and FGF2 expression was performed in mouse uterine tissue. Human endometrial samples were obtained from both nonsmokers and smokers. Real-time reverse transcription-polymerase chain reaction was performed for all cell cultures and human samples.

RESULTS

Compared to controls, CXCL12 and FGF2 mRNA expression were significantly decreased in CSE-exposed HESC and primary cells. In mice, immunohistochemical analysis showed that both CXCL12 and FGF2 protein expression was lower in the CS group compared to controls. Similarly, both CXCL12 and FGF2 expression were decreased in women who smoke compared to nonsmokers.

CONCLUSION

Decreased endometrial CXCL12 and FGF2 expression contribute to the impaired endometrial receptivity in women who smoke. Smoking is also associated with decreased rates of endometrial cancer and endometriosis; increased CXCL12 and FGF2 are implicated in both conditions. The changes in the expression of cytokines described here may explain the impact of smoking on all of these diseases. Tobacco has direct effects on normal endometrium that impacts endometrial health and disease.

SDF-1/CXCL12 and CXCR4 gene variants, and elevated serum SDF-1 levels are associated with preeclampsia

OBJECTIVE

We aimed to compare the frequencies of stromal cell-derived factor-1 (SDF-1) 3'A and CXCR4 single-nucleotide polymorphisms (SNPs) and serum SDF-1 levels in patients with preeclampsia (PE).

METHODS

In total, 89 women with PE and 89 control women were included in the study. Genotyping was done by polymerase chain reaction-restriction fragment length polymorphism method. Enzyme-linked immunosorbent assay method was used to measure serum SDF-1 level.

RESULTS

For SDF-1 3'A SNP, the frequency of GA genotype, total number of GA and AA genotypes, and the A allele frequency was higher in PE patients than controls (p = 0.04, 0.023, and 0.029, respectively). For CXCR4 SNP, the frequency of CT genotype, total number of CT and TT genotypes, and the T allele frequency were higher in PE patients than controls (p = 0.04, 0.006, and 0.005, respectively). SDF-1 serum level was detected higher in preeclamptic women compared with controls (p = 0.001). In PE patients, there was no significant association between serum SDF-1 levels and genotypes of SDF-1 3'A SNP. SDF-1 level was significantly higher in patients bearing CXCR4 CT genotype than CC genotype (p = 0.001). Furthermore, SDF-1 levels in patients bearing CT+TT genotype were found higher than that of patients with CC genotypes (p = 0.001).

CONCLUSION

Results of our study suggest that SDF-1 3'A and CXCR4 polymorphisms and elevated serum SDF-1 levels may have a role in the development of PE.

Decoding the chemokine network that links leukocytes with decidual cells and the trophoblast during early implantation

Chemokine network is central to the innate and adaptive immunity and entails a variety of proteins and membrane receptors that control physiological processes such as wound healing, angiogenesis, embryo growth and development. During early pregnancy, the chemokine network coordinates not only the recruitment of different leukocyte populations to generate the maternal-placental interface, but also constitutes an additional checkpoint for tissue homeostasis maintenance. The normal switch from a pro-inflammatory to an anti-inflammatory predominant microenvironment characteristic of the post-implantation stage requires redundant immune tolerance circuits triggered by key master regulators. In this review we will focus on the recruitment and conditioning of maternal immune cells to the uterus at the early implantation period with special interest on high plasticity macrophages and dendritic cells and their ability to induce regulatory T cells. We will also point to putative immunomodulatory polypeptides involved in immune homeostasis maintenance at the maternal-placental interface.

Insights into the mechanism of CXCL12-mediated signaling in trophoblast functions and placental angiogenesis

The chemokine CXCL12 and its receptor CXCR4 are important signaling components required for human blastocyst implantation and the progression of pregnancy. Growing evidence indicates that the CXCL12/CXCR4 axis can regulate trophoblast function and uterine spiral artery remodeling, which plays a fundamental role in placentation and fetal outcome. The orphan receptor CXCR7 is also believed to partly regulate the function of the CXCL12/CXCR4 axis. Additionally, the CXCL12/CXCR4/CXCR7 axis can enhance the cross-talk between trophoblasts and decidual cells such as uterine natural killer cells and decidual stromal cells which are involved in regulation of trophoblast differentiation and invasion and placental angiogenesis. In addition, recent studies proved that CXCL12 expression is elevated in the placenta and mid-trimester amniotic fluid of pregnant women with preeclampsia, implying that dysregulation of CXCL12 plays a role in the pathogenesis of preeclampsia. Further understanding of the regulatory mechanisms of CXCL12-mediated signaling in trophoblast functions and placental angiogenesis may help to design novel therapeutic approaches for pregnancy-associated diseases.

Human chorionic gonadotropin increases serum progesterone, number of corpora lutea and angiogenic factors in pregnant sheep

Early gestation is a critical period when implantation and placental vascularization are established, processes influenced by progesterone (P4). Although human chorionic gonadotropin (hCG) is not endogenously synthesized by livestock, it binds the LH receptor, stimulating P4 synthesis. We hypothesized treating pregnant ewes with hCG would increase serum P4, number of corpora lutea (CLs) and concepti, augment steroidogenic enzymes, and increase membrane P4 receptors (PAQRs) and angiogenic factors in reproductive tissues. The objective was to determine molecular alterations induced by hCG in pregnant sheep that may promote pregnancy. Ewes received either 600 IU of hCG or saline i.m. on day 4 post mating. Blood samples were collected daily from day 0 until tissue collection for serum P4 analysis. Reproductive tissues were collected on either day 13 or 25 of gestation and analyzed for PAQRs, CXCR4, proangiogenic factors and steroidogenic enzymes. Ewes receiving hCG had more CL and greater serum P4, which remained elevated. On day 25, StAR protein production decreased in CL from hCG-treated ewes while HSD3B1 was unchanged; further, expression of CXCR4 significantly increased and KDR tended to increase. PAQR7 and CXCR4 protein was increased in caruncle tissue from hCG-treated ewes. Maternal hCG exposure influenced fetal extraembryonic tissues, as VEGFA, VEGFB, FLT1, and ANGPT1 expression increased. Our results indicate hCG increases serum P4 due to augmented CL number per ewe. hCG treatment resulted in greater PAQR7 and CXCR4 in maternal endometrium and promoted expression of proangiogenic factors in fetal extraembryonic membranes. Supplementing livestock with hCG may boost P4 levels and improve reproductive efficiency.

Activation of the CXCL12/CXCR4 signaling axis may drive vascularization of the ovine placenta

Early pregnancy, when most embryonic losses occur, is a critical period in which vital placental vascularization is established. Vascular endothelial growth factor (VEGF) is a potent inducer of angiogenesis, and factors that regulate VEGF function, expression, or both may ultimately affect vascularization. Activation of the C-X-C chemokine receptor type 4 (CXCR4) by its cognate ligand, C-X-C chemokine ligand 12 (CXCL12), increases VEGF synthesis and secretion, which in turn stimulates CXCL12 and CXCR4 production and this synergistic regulation may influence placental vascularization. We hypothesized that expression of CXCL12, CXCR4, select angiogenic factors, and their receptors would increase in placental tissues during early pregnancy and that treatment of ovine trophectoderm cells with CXCL12 would increase production of angiogenic factors. To test this hypothesis, maternal caruncle (CAR) and fetal extraembryonic membrane (FM) tissues were collected on days 18, 20, 22, 25, 26, and 30 of pregnancy and on day 10 of the estrous cycle (control, NP) to determine relative mRNA or protein expression of CXCL12 and CXCR4 and selected angiogenic factors. In CAR, expression of mRNA for CXCR4 increased on day 18, 20, 22, and 25 and CXCL12 increased on day 18 and 20 compared with NP ewes. CXCL12 protein followed a similar pattern in CAR tissue, with greater levels on day 20 than in NP tissue. Greater levels of fibroblast growth factor 2 (FGF2) mRNA was observed in CAR on day 20 of gestation than on day 30. In FM, CXCL12, CXCR4, angiopoietin 1, VEGF, and VEGF receptor 1 were enhanced with advancing pregnancy, whereas FGF2 and kinase insert domain receptor (or VEGF receptor 2) peaked on day 25. An increase in protein levels occurred on day 25 compared with day 20 in FM for CXCL12 and CXCR4, as well as a similar tendency for FGF2 protein. Both CXCL12 and CXCR4 are specifically localized to trophoblast cells and to the uterine luminal and glandular epithelium. Treatment of ovine trophectoderm cells with CXCL12 increased mRNA expression for VEGF and FGF2. The relationship between VEGF, FGF2, and the CXCL12/CXCR4 signaling underscores the potential role for this chemokine axis in driving placentation.

CXCL12-CXCR7 signaling activates ERK and Akt pathways in human choriocarcinoma cells

Abstract CXCL12 acts as a physiological ligand for the chemokine receptor CXCR7. Chemokine receptor expression by human trophoblast and other placental cells have important implications for understanding the regulation of placental growth and development. We had previously reported the differential expression of CXCR7 in different stages of the human placenta suggesting its possible role in regulation of placental growth and development. In this study, we determined the expression of CXCR7 in human choriocarcinoma JAR cells at the mRNA level and protein level and the downstream signaling pathway mediated by CXCL12-CXCR7 interaction. We observed that binding of CXCL12 to CXCR7 activates the ERK and Akt cell-survival pathways in JAR cells. Inhibition of the ERK and Akt pathways using specific inhibitors (Wortmanin & PD98509) led to the activation of the p38 pathway. Our findings suggest a possible role of CXCR7 in activating the cell survival pathways ERK and Akt in human choriocarcinoma JAR cells.

CXCL12 receptor preference, signal transduction, biological response and the expression of 5T4 oncofoetal glycoprotein

CXCL12 is a pleiotropic chemokine capable of eliciting multiple signal transduction cascades and functions, via interaction with either CXCR4 or CXCR7. Factors that determine CXCL12 receptor preference, intracellular signalling route and biological response are poorly understood but are of central importance in the context of therapeutic intervention of the CXCL12 axis in multiple disease states. We have recently demonstrated that 5T4 oncofoetal glycoprotein facilitates functional CXCR4 expression leading to CXCL12 mediated chemotaxis in mouse embryonic cells. Using wild type (WT) and 5T4 knockout (5T4KO) murine embryonic fibroblasts (MEFs), we now show that CXCL12 binding to CXCR4 activates both the ERK and AKT pathways within minutes, but while these pathways are intact, they are non-functional in 5T4KO cells treated with CXCL12. Importantly, in the absence of 5T4 expression, CXCR7 is upregulated and becomes the predominant receptor for CXCL12, activating a distinct signal transduction pathway with slower kinetics involving transactivation of the epidermal growth factor receptor (EGFR), eliciting proliferation rather than chemotaxis. Thus the surface expression of 5T4 marks the use of the CXCR4 rather than the CXCR7 receptor, with distinct consequences for CXCL12 exposure, relevant to the spread and growth of a tumour. Consistent with this hypothesis, we have identified human small cell lung carcinoma cells with similar 5T4/CXCR7 reciprocity that is predictive of biological response to CXCL12 and determined that 5T4 expression is required for functional chemotaxis in these cells.

Gene targeting in primary human trophoblasts

Studies in primary human trophoblasts provide critical insights into placental function in normal and complicated pregnancies. Mechanistic studies in these cells require experimental tools to modulate gene expression. Lipid-based methods to transfect primary trophoblasts are fairly simple to use and allow for the efficient delivery of nucleic acids, but potential toxic effects limit these methods. Viral vectors are versatile transfection tools of native trophoblastic or foreign cDNAs, providing high transfection efficiency, low toxicity and stable DNA integration into the trophoblast genome. RNA interference (RNAi), using small interfering RNA (siRNA) or microRNA, constitutes a powerful approach to silence trophoblast genes. However, off-target effects, such as regulation of unintended complementary transcripts, inflammatory responses and saturation of the endogenous RNAi machinery, are significant concerns. Strategies to minimize off-target effects include using multiple individual siRNAs, elimination of pro-inflammatory sequences in the siRNA construct and chemical modification of a nucleotide in the guide strand or of the ribose moiety. Tools for efficient gene targeting in primary human trophoblasts are currently available, albeit not yet extensively validated. These methods are critical for exploring the function of human trophoblast genes and may provide a foundation for the future application of gene therapy that targets placental trophoblasts.

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.

Natural killer cell-triggered vascular transformation: maternal care before birth?

Natural killer (NK) cells are found in lymphoid and non-lymphoid organs. In addition to important roles in immune surveillance, some NK cells contribute to angiogenesis and circulatory regulation. The uterus of early pregnancy is a non-lymphoid organ enriched in NK cells that are specifically recruited to placental attachment sites. In species with invasive hemochorial placentation, these uterine natural killer (uNK) cells, via secretion of cytokines, chemokines, mucins, enzymes and angiogenic growth factors, contribute to the physiological change of mesometrial endometrium into the unique stromal environment called decidua basalis. In humans, uNK cells have the phenotype CD56(bright)CD16(dim) and they appear in great abundance in the late secretory phase of the menstrual cycle and early pregnancy. Gene expression studies indicate that CD56(bright)CD16(dim) uterine and circulating cells are functionally distinct. In humans but not mice or other species with post-implantation decidualization, uNK cells may contribute to blastocyst implantation and are of interest as therapeutic targets in female infertility. Histological and genetic studies in mice first identified triggering of the process of gestation spiral arterial modification as a major uNK cell function, achieved via interferon (IFN)-γ secretion. During spiral arterial modification, branches from the uterine artery that traverse the endometrium/decidua transiently lose their muscular coat and ability to vasoconstrict. The expression of vascular markers changes from arterial to venous as these vessels dilate and become low-resistance, high-volume channels. Full understanding of the vascular interactions of human uNK cells is difficult to obtain because endometrial time-course studies are not possible in pregnant women. Here we briefly review key information concerning uNK cell functions from studies in rodents, summarize highlights concerning human uNK cells and describe our preliminary studies on development of a humanized, pregnant mouse model for in vivo investigations of human uNK cell functions.

Learning from nature: pregnancy changes the expression of inflammation-related genes in patients with multiple sclerosis

Background

Pregnancy is associated with reduced activity of multiple sclerosis (MS). However, the biological mechanisms underlying this pregnancy-related decrease in disease activity are poorly understood.

Methodology

We conducted a genome-wide transcription analysis in peripheral blood mononuclear cells (PBMCs) from 12 women (7 MS patients and 5 healthy controls) followed during their pregnancy. Samples were obtained before, during (i.e. at the third, sixth, and ninth month of gestation) and after pregnancy. A validation of the expression profiles has been conducted by using the same samples and an independent group of 25 MS patients and 11 healthy controls. Finally, considering the total group of 32 MS patients, we compared expression profiles of patients relapsing during pregnancy (n = 6) with those of relapse-free patients (n = 26).

Principal Findings

Results showed an altered expression of 347 transcripts in non-pregnant MS patients with respect to non-pregnant healthy controls. Complementary changes in expression, occurring during pregnancy, reverted the previous imbalance particularly for seven inflammation-related transcripts, i.e. SOCS2, TNFAIP3, NR4A2, CXCR4, POLR2J, FAM49B, and STAG3L1. Longitudinal analysis showed that the overall deregulation of gene expression reverted to “normal” already within the third month of gestation, while in the post-partum gene expressions rebounded to pre-pregnancy levels. Six (18.7%) of the 32 MS patients had a relapse during pregnancy, mostly in the first trimester. The latter showed delayed expression profiles when compared to relapse-free patients: in these patients expression imbalance was reverted later in the pregnancy, i.e. at sixth month.

Conclusions

Specific changes in expression during pregnancy were associated with a decrease in disease activity assessed by occurrence of relapses during pregnancy. Findings might help in understanding the pathogenesis of MS and may provide basis for the development of novel therapeutic strategies.

Proteasome-independent degradation of HIV-1 in naturally non-permissive human placental trophoblast cells

BACKGROUND

The human placenta-derived cell line BeWo has been demonstrated to be restrictive to cell-free HIV-1 infection. BeWo cells are however permissive to infection by VSV-G pseudotyped HIV-1, which enters cells by a receptor-independent mechanism, and to infection by HIV-1 via a cell-to-cell route.

RESULTS

Here we analysed viral entry in wild type BeWo (CCR5+, CXCR4+) and BeWo-CD4+ (CD4+, CCR5+, CXCR4+) cells. We report that HIV-1 internalisation is not restricted in either cell line. Levels of internalised p24 antigen between VSV-G HIV-1 pseudotypes and R5 or X4 virions were comparable. We next analysed the fate of internalised virions; X4 and R5 HIV-1 virions were less stable over time in BeWo cells than VSV-G HIV-1 pseudotypes. We then investigated the role of the proteasome in restricting cell-free HIV-1 infection in BeWo cells using proteasome inhibitors. We observed an increase in the levels of VSV-G pseudotyped HIV-1 infection in proteasome-inhibitor treated cells, but the infection by R5-Env or X4-Env pseudotyped virions remains restricted.

CONCLUSION

Collectively these results suggest that cell-free HIV-1 infection encounters a surface block leading to a non-productive entry route, which either actively targets incoming virions for non-proteasomal degradation, and impedes their release into the cytoplasm, or causes the inactivation of mechanisms essential for viral replication.

Differential expression of RDC1/CXCR7 in the human placenta

INTRODUCTION

Chemokine receptor expression by human trophoblast and other placental cells have important implications for understanding the regulation of placental growth, development, and their role in maternofetal HIV transmission. CXCR7, now a deorphanized G protein coupled receptor that has been recently shown to bind to the ligands ITAC and CXCL12 has been proposed to act as a co-receptor for HIV-1, HIV-2, and SIV strains. The differential expression of CXCR7 in the human placenta is not yet reported.

METHODS

The expression of CXCR7 was studied in 45 different human placental tissues, of which 20 were from early placental tissues (8-10 week old) obtained from medically terminated pregnancies and 25 were placenta from normal term deliveries.

RESULTS

Immunohistochemistry and RT-PCR analysis revealed a greater expression of CXCR7 in term human placenta as compared to the early stage. This was further confirmed by real-time PCR.

CONCLUSION

Our study reveals, for the first time, the differential expression of CXCR7 in early (8-10 weeks) and term human placenta. The precise role of CXCR7 in the human placenta needs to be determined. HIV vertical transmission is reported to occur mainly during the end stages of pregnancy. Our finding of increased CXCR7 expression in the term human placenta therefore warrants future studies to assess its role in the vertical transmission of HIV-1.

Expression of CD134 and CXCR4 mRNA in term placentas from FIV-infected and control cats

Feline immunodeficiency virus (FIV) causes a natural infection of domestic cats that resembles HIV-1 in pathogenesis and disease progression. Feline AIDS is characterized by depression of the CD4+ T cell population and fatal opportunistic infections. Maternal-fetal transmission of FIV readily occurs under experimental conditions, resulting in infected viable kittens and resorbed or arrested fetal tissues. Although both FIV and HIV use the chemokine receptor CXCR4 as a co-receptor, FIV does not utilize CD4 as the primary receptor. Rather, CD134 (OX40), a T cell activation antigen and co-stimulatory molecule, is the primary receptor for FIV. We hypothesized that placental expression of CD134 and CXCR4 may render the placenta vulnerable to FIV infection, possibly facilitating efficient vertical transmission of FIV, and impact pregnancy outcome. The purpose of this project was to quantify the relative expression of CD134 and CXCR4 mRNA from the term placentas of three groups of cats: uninfected queens producing viable offspring, experimentally-infected queens producing only viable offspring, and experimentally-infected queens producing viable offspring among mostly non-viable fetuses. Total RNA was extracted from term placental tissues from all groups of cats. Real-time one-step reverse transcriptase-PCR was used to measure gene expression. The FIV receptors CD134 and CXCR4 were expressed in all late term feline placental tissues. Placentas from FIV-infected queens producing litters of only viable offspring expressed more CD134 and CXCR4 mRNA than those from uninfected queens, suggesting that infection may cause upregulation of the receptors. On the other hand, placentas from FIV-infected cats with non-successful pregnancies expressed similar levels of CD134 mRNA and slightly less CXCR4 mRNA than those from uninfected queens. Thus, it appears that cells expressing these receptors may play a role in pregnancy maintenance.

Rab5 and Rab7, but Not ARF6, Govern the Early Events of HIV-1 Infection in Polarized Human Placental Cells

Trophoblasts, the structural cells of the placenta, are thought to play a determinant role in in utero HIV type 1 (HIV-1) transmission. We have accumulated evidence suggesting that HIV-1 infection of these cells is associated with uptake by an unusual clathrin/caveolae-independent endocytic pathway and that endocytosis is followed by trafficking through multiple organelles. Furthermore, part of this trafficking involves the transit of HIV-1 from transferrin-negative to EEA1 and transferrin-positive endosomes, suggesting a merger from nonclassical to classical endocytic pathways in these cells. In the present article, the relationship between the presence of HIV-1 within specific endosomes and infection was studied. We demonstrate that viral infection is virtually lost when endosome inhibitors are added shortly after exposure to HIV-1. Thus, contrary to what is seen in CD4+ T lymphocytes, the initial presence of HIV-1 within the endosomes is mandatory for infection to take place. Importantly, this process is independent of the viral envelope proteins gp120 and gp41. The Rab family of small GTPases coordinates the vesicular transport between the different endocytic organelles. Experiments performed with various expression vectors indicated that HIV-1 infection in polarized trophoblasts relies on Rab5 and Rab7 without the contribution of Arf6 or Rab11. Furthermore, we conclude that Rab5 drives movements from raft-rich region to early endosomes, and this transit is required for subsequently reaching late endosomes via Rab7. This complex trafficking is mandatory for HIV-1 infection to proceed in human polarized trophoblasts.

The Feline Immunodeficiency Virus-Infected Cat: A Model for Lentivirus-induced Placental Immunopathology and Reproductive Failure (Mini-Review)

PROBLEM

Pediatric human immunodeficiency virus (HIV) infection is largely a result of transplacental transmission, and pregnancy perturbation is more frequent in HIV-infected women. Dysregulation of placental immunology may occur during HIV infection, possibly facilitating HIV vertical transfer and miscarriage. The (FIV)-infected cat is a useful small-animal model for HIV pathogenesis because the viruses share common biological and clinical features. Transplacental transmission is readily achieved experimentally, resulting in a high proportion of infected offspring and frequent reproductive failure.

METHOD OF STUDY

We are using this model to examine lentivirus-induced placental immunopathology to determine the role aberrant immunology plays in intrauterine transmission and pregnancy perturbation.

RESULTS

Kittens were cesarean delivered from FIV-B-2542-infected and control queens at week 8 gestation (1 week short of term), and placental and fetal specimens were collected. On average, control queens delivered 3.8 kittens/litter, and 1 of 31 kittens (3.2%) was non-viable. FIV-infected queens produced 2.7 kittens/litter with 15 of 25 fetuses (60%) non-viable. The virus was detected in 14 of 15 placentas (93%) and 21 of 22 fetuses (95%) using polymerase chain reaction (PCR). Using a one-step, real time reverse transcriptase (RT)-PCR, we measured expression of representative placental T helper 1 (Th1) cytokines, interleukin (IL)-1beta and interferon (IFN)-gamma, a Th2 cytokine, IL-10, and chemokine receptor CXCR4. A comparison of placental cytokine expression between infected and control queens did not reveal differences between the two groups. However, elevated expression of Th1 cytokines and increased Th1/Th2 ratios (IL-1beta/IL-10) occurred in placentas from resorptions, indicating that increased placental Th1 cytokine expression was associated with pregnancy failure in the FIV-infected cat.

CONCLUSION

The potential to establish efficient FIV in utero transmission, coupled with the parallels in immunopathology between FIV-infected cats and HIV-infected humans, suggests the usefulness of the FIV-infected cat as a cost-effective, small-animal model to study lentivirus-induced immunopathology, transplacental infection, and reproductive failure.