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

Placental insufficiency and heavier placentas in sheep after suppressing CXCL12/CXCR4 signaling during implantation†

During implantation, trophoblast cell invasion and differentiation is predominantly important to achieving proper placental formation and embryonic development. The chemokine, C-X-C motif chemokine ligand 12 (CXCL12) working through its receptor C-X-C motif chemokine receptor 4 (CXCR4) is implicated in implantation and placentation but precise roles of this axis are unclear. Suppressing CXCL12/CXCR4 signaling at the fetal-maternal interface in sheep reduces trophoblast invasion, disrupts uterine remodeling, and diminishes placental vascularization. We hypothesize these negative impacts during implantation will manifest as compromised fetal and placental growth at midgestation. To test, on day 12 postbreeding, osmotic pumps were surgically installed in 30 ewes and delivered intrauterine CXCR4 inhibitor or saline for 7 or 14 days. On day 90, fetal/maternal tissues were collected, measured, weighed, and maternal (caruncle) and fetal (cotyledon) placenta components separated and analyzed. The objectives were to determine if (i) suppressing CXCL12/CXCR4 during implantation results in reduced fetal and placental growth and development and (ii) if varying the amount of time CXCL12/CXCR4 is suppressed impacts fetal/placental development. Fetal weights were similar; however greater placental weight and placentome numbers occurred when CXCL12/CXCR4 was suppressed for 14 days. In caruncles, greater abundance of fibroblast growth factor 2, vascular endothelial growth factor A, vascular endothelial growth factor A receptor 1 (FLT-1), and placental growth factor were observed after suppressing CXCL12/CXCR4. Similar results occurred in cotyledons except less vascular endothelial growth factor in 7 day group and less fibroblast growth factor in 14 day group. Our data underscore the importance of CXCL12/CXCR4 signaling during placentation and provide strong evidence that altering CXCL12-mediated signaling induces enduring placental effects manifesting later in gestation.

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.

Differentially Expressed Candidate miRNAs of Day 16 Bovine Embryos on the Regulation of Pregnancy Establishment in Dairy Cows

Recent advances in high-throughput in silico techniques translate experimental data into meaningful biological networks through which the role of individual proteins, interactions, and their biological functions are comprehended. The study objective was to identify differentially expressed (DE) miRNAs between the day 16 competent, elongated embryo from normal cows and the day 16 noncompetent, tubular embryos from repeat breeder cows, assimilate DE-miRNAs to their target genes, and group target genes based on biological function using in silico methods. The 84 prioritized bovine-specific miRNAs were investigated by RT-PCR, and the results showed that 19 were differentially expressed (11 up- and 8 down-regulated) in the competent embryos compared to noncompetent ones (p ≤ 0.05; fold regulation ≥ 2 magnitudes). Top-ranked integrated genes of DE-miRNAs predicted various biological and molecular functions, cellular processes, and signaling pathways. Further, analysis of the categorized groups of genes showed association with signaling pathways, turning on or off key genes and transcription factors regulating the development of embryo, placenta, and various organs. In conclusion, highly DE-miRNAs in day 16 bovine conceptus regulated the embryogenesis and pregnancy establishment. The elucidated miRNA-mRNA interactions in this study were mostly based on predictions from public databases. Therefore, the causal regulations of these interactions and mechanisms require further functional characterization.

Caffeic Acid Phenethyl Ester Reduces the Adverse Effects of Nicotine on the Endometrium

Background

Tobacco smoke contains various toxins that negatively affect the human reproductive system. Caffeic acid phenethyl ester (CAPE), a potent antioxidant, has protective effects on the reproductive system against oxygen-free radicals, methotrexate, and pesticides. Herein, the effect of CAPE on some key markers of endometrial receptivity has been evaluated.

Methods

A cross-sectional study was conducted during 2018-2019 in the Department of Clinical Biochemistry, School of Medicine, Fasa University of Medical Sciences (Fasa, Iran). Primary endometrial cells were divided into five groups, namely control, nicotine, CAPE, vehicle, and nicotine+CAPE. Real-time polymerase chain reaction (PCR) and methylation-specific PCR were performed to evaluate gene expressions and methylation, respectively. Appropriate doses of CAPE and nicotine were determined using the MTT assay. Data were analyzed using SPSS software (version 16.0) with a one-way analysis of variance. P<0.01 was considered statistically significant. The fold change was calculated using the 2-∆ΔCT method.

Results

Treatment of cells with nicotine significantly reduced the expression of C-X-C motif chemokine ligand 12 (CXCL12), fibroblast growth factor 2 (FGF2), and vascular endothelial growth factor A (VEGF-A) genes (P<0.0001). However, the expression levels increased significantly when treated with nicotine+CAPE (P<0.0001). Despite the reduced CXCL12 gene expression in cells treated with nicotine, CXCL12 was unmethylated in all study groups, indicating that the methylation status of the CXCL12 gene was not affected by nicotine or CAPE.

Conclusion

CAPE can be a suitable agent to protect female smokers from the harmful effects of nicotine. This manuscript is available as a preprint on the Research Gate website.

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.

CXCL12 May Drive Inflammatory Potential in the Ovine Corpus Luteum During Implantation

Adequate corpus luteum (CL) function is paramount to successful pregnancy. Structural and functional CL integrity is controlled by diverse cell types that contribute and respond to the local cytokine milieu. The chemokine ligand 12 (CXCL12) and receptor, CXCR4, are modulators of inflammation and cell survival, but little is understood about CXCL12-CXCR4 axis and CL functional regulation. Corpora lutea from control nonpregnant ewes (n = 5; day 10 estrous cycle (D10C)) and pregnant ewes (n = 5/day) on days 20 (D20P) and 30 (D30P) post-breeding were analyzed for gene and protein expression of CXCL12, CXCR4, and select inflammatory cytokines. In separate cell culture studies, cytokine production was evaluated following CXCL12 treatment. Abundance of CXCL12 and CXCR4 increased (P < 0.05) in pregnant ewes compared to nonpregnant ewes, as determined by a combination of quantitative PCR, immunoblot, and immunofluorescence microscopy. CXCR4 was detected in steroidogenic and nonsteroidogenic cells in ovine CL, and select pro-inflammatory mediators were greater in CL from pregnant ewes. In vitro studies revealed greater abundance of tumor necrosis factor (TNF) following CXCL12 administration (P = 0.05), while P4 levels in cell media were unchanged. Fully functional CL of pregnant ewes is characterized by increased abundance of inflammatory cytokines which may function in a luteotropic manner. We report concurrent increases in CXCL12, CXCR4, and select inflammatory mediators in ovine CL as early pregnancy progresses. We propose CXCL12 stimulates production of select cytokines, rather than P4 in the CL to assist in CL establishment and survival.

Inhibition of the C-X-C Motif Chemokine 12 (CXCL12) and Its Receptor CXCR4 Reduces Utero-Placental Expression of the VEGF System and Increases Utero-Placental Autophagy

The placenta, a unique organ that only develops during pregnancy, is essential for nutrient, oxygen, and waste exchange between offspring and mother. Yet, despite its importance, the placenta remains one of the least understood organs and knowledge of early placental formation is particularly limited. Abnormalities in placental development result in placental dysfunction or insufficiency whereby normal placental physiology is impaired. Placental dysfunction is a frequent source of pregnancy loss in livestock, inflicting serious economic impact to producers. Though the underlying causes of placental dysfunction are not well-characterized, initiation of disease is thought to occur during establishment of functional fetal and placental circulation. A comprehensive understanding of the mechanisms controlling placental growth and vascularization is necessary to improve reproductive success in livestock. We propose chemokine C-X-C motif ligand 12 (CXCL12) signaling through its receptor CXCR4 functions as a chief coordinator of vascularization through direct actions on fetal trophoblast and maternal endometrial and immune cells. To investigate CXCL12–CXCR4 signaling on uteroplacental vascular remodeling at the fetal–maternal interface, we utilized a CXCR4 antagonist (AMD3100). On day 12 post-breeding in sheep, osmotic pumps were surgically installed and delivered either AMD3100 or saline into the uterine lumen ipsilateral to the corpus luteum for 14 days. On day 35 of ovine pregnancy, fetal/placental and endometrial tissues were collected, snap-frozen in liquid nitrogen, and uterine horn cross sections were preserved for immunofluorescent analysis. Suppressing CXCL12–CXCR4 at the fetal–maternal interface during initial placental vascularization resulted in diminished abundance of select angiogenic factors in fetal and maternal placenta on day 35. Compared to control, less vascular endothelial growth factor (VEGF) and VEFG receptor 2 (KDR) were observed in endometrium when CXCL12–CXCR4 was diminished. Less VEGF was also evident in fetal placenta (cotyledons) in ewes receiving AMD3100 infusion compared to control. Suppressing CXCL12–CXCR4 at the fetal–maternal interface also resulted in greater autophagy induction in fetal and maternal placenta compared to control, suggestive of CXCL12–CXCR4 impacting cell survival. CXCL12–CXCR4 signaling may govern placental homeostasis by serving as a critical upstream mediator of vascularization and cell viability, thereby ensuring appropriate placental development.

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.

CXCR4 signaling at the fetal-maternal interface may drive inflammation and syncytia formation during ovine pregnancy†

Early pregnancy features complex signaling between fetal trophoblast cells and maternal endometrium directing major peri-implantation events including localized inflammation and remodeling to establish proper placental development. Proinflammatory mediators are important for conceptus attachment, but a more precise understanding of molecular pathways regulating this process is needed to understand how the endometrium becomes receptive to implantation. Both chemokine ligand 12 (CXCL12) and its receptor CXCR4 are expressed by fetal and maternal tissues. We identified this pair as a critical driver of placental angiogenesis, but their additional importance to inflammation and trophoblast cell survival, proliferation, and invasion imply a role in syncytia formation at the fetal-maternal microenvironment. We hypothesized that CXCL12 encourages both endometrial inflammation and conceptus attachment during implantation. We employed separate ovine studies to (1) characterize endometrial inflammation during early gestation in the ewe, and (2) establish functional implications of CXCL12 at the fetal-maternal interface through targeted intrauterine infusion of the CXCR4 inhibitor AMD3100. Endometrial tissues were evaluated for inflammatory mediators, intracellular signaling events, endometrial modifications, and trophoblast syncytialization using western blotting and immunohistochemistry. Endometrial tissue from ewes receiving CXCR4 inhibitor demonstrated dysregulated inflammation and reduced AKT and NFKB, paired with elevated autophagic activity compared to control. Immunohistochemical observation revealed an impairment in endometrial surface remodeling and diminished trophoblast syncytialization following localized CXCR4 inhibition. These data suggest CXCL12-CXCR4 regulates endometrial inflammation and remodeling for embryonic implantation, and provide insight regarding mechanisms that, when dysregulated, lead to pregnancy pathologies such as intrauterine growth restriction and preeclampsia.

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.

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.

Interferon tau-dependent and independent effects of the bovine conceptus on the endometrial transcriptome†

This study investigated bovine conceptus-induced modifications to the endometrial transcriptome related to effects of interferon tau (IFNT), conceptus origin (in vivo vs. in vitro), and conceptus sex. In vitro (IVF) or in vivo (superovulation and artificial insemination, AI) produced blastocysts were transferred into recipient heifers on day 7 of the estrous cycle. On day 15, IVF- or AI-derived conceptuses were obtained by uterine flushing and individually placed on endometrial explants in media for 6 h. Explants were also cultured with media alone as a control or media containing 100 ng/mL IFNT. Total explant RNA was analyzed by RNA-Seq. Incubation of endometrium with IFNT or IVF- or AI-derived conceptuses changed (P ≤ 0.001) expression of 491, 498, and 576 transcripts, respectively, compared to the control. Further, 369 differentially expressed genes (DEGs) were common between explants exposed to IFNT or a conceptus. A total of 240 DEGs were uniquely altered by conceptuses (IVF- and AI-derived) but not IFNT. Of these transcripts, 46 were shared between the IVF and AI groups, while 61 and 133 were specific to IVF and AI conceptuses, respectively. Five genes [melanophilin (MLPH), prominin-2 (PROM2), myeloid associated differentiation marker (MYADM), vomeronasal 1 receptor 4 like (VN1R4L) and 5-hydroxytryptamine receptor 1A (HTR1A)] were more abundant in endometrium exposed to female compared to male conceptuses (P < 0.001). A single gene [ADP-ribosylation factor like GTPase 4C (ARL4C)] was more abundant in response to male conceptuses (P < 0.001) than female conceptuses. These data support the hypothesis that conceptus regulation of gene expression in the endometrium is complex and involves factors other than IFNT that may have a biological role in pregnancy establishment.

Effect of Placental Growth Factor on Trophoblast-Endothelial Cell Interactions In Vitro

Placental growth factor (PlGF) is an important angiogenic factor which has an emerging role in the clinical management of suspected preeclampsia. The role of PlGF in normal placental development is not completely understood and it is uncertain whether PlGF influences trophoblast and endothelial cell interactions central to uterine spiral artery remodelling, especially in variable oxygen conditions. A two-cell model of endovascular invasion was used. Tissue culture plates were coated with Matrigel™, on which fluorescent-labelled uterine microvascular endothelial cells (1 × 10⁵/well) and HTR8/SVNeo cells were co-cultured (1 × 10⁵/well) for 20 h. Co-cultures were treated with recombinant human PlGF (rhPlGF) (10 or 100 ng/mL) and incubated at either 21% O₂ or 2% O₂. Images were captured by fluorescence microscopy and analysed using ImageJ (n = 7). Data was analysed using SPSSv24. Treatment with rhPlGF did not improve integration in co-cultures irrespective of oxygen conditions but increased proliferation in 2% O₂ of both trophoblast and endothelial cells. Expression of angiogenic factors VEGF, sFLT-1, PlGF and CXCL12 in both co-cultures and in isolated trophoblast cells was not altered by rhPlGF treatment. Expression of TLR-3 mRNA in co-cultures was increased by rhPlGF 100 ng/mL at 21% O₂ (p = 0.03). PlGF contributes to trophoblast and endothelial cell proliferation in the setting of physiological hypoxia but does not influence trophoblast and endothelial cell interactions in an in vitro model of spiral artery remodelling. Upregulation of TLR-3 expression in co-cultures may indicate a role for PlGF in the placental inflammatory response.

Emerging roles of atypical chemokine receptor 3 (ACKR3) in normal development and physiology

The discovery that atypical chemokine receptors (ACKRs) can initiate alternative signaling pathways rather than classical G-protein coupled receptor (GPCR) signaling has changed the paradigm of chemokine receptors and their roles in modulating chemotactic responses. The ACKR family has grown over the years, with discovery of new functions and roles in a variety of pathophysiological conditions. However, the extent to which these receptors regulate normal physiology is still continuously expanding. In particular, atypical chemokine receptor 3 (ACKR3) has proven to be an important receptor in mediating normal biological functions, including cardiac development and migration of cortical neurons. In this review, we illustrate the versatile and intriguing role of ACKR3 in physiology.

Cysteine-X-cysteine motif chemokine ligand 12 and its receptor CXCR4: expression, regulation, and possible function at the maternal-conceptus interface during early pregnancy in pigs

Cysteine-X-cysteine (CXC) motif chemokine ligand 12 (CXCL12) and its receptor, CXC chemokine receptor type 4 (CXCR4), are involved in regulating the proliferation, migration, and survival of trophoblast cells and the maternal immune response in humans and mice. The present study examined the expression, regulation, and function of CXCL12 and CXCR4 at the maternal-conceptus interface during pregnancy in pigs. The endometrium expressed CXCL12 and CXCR4 mRNAs with the greatest CXCL12 abundance on Day 15 of pregnancy. CXCL12 protein was localized mainly in endometrial epithelial cells, while CXCR4 protein was localized in subepithelial stromal cells, vascular endothelial cells, and immune cells in blood vessels in the endometrium during the estrous cycle and pregnancy. CXCL12 protein was detected in uterine flushing on Day 15 of pregnancy. The conceptus during early pregnancy and chorioallantoic tissues during mid-to-late pregnancy expressed CXCL12 and CXCR4. Interferon-γ increased the abundance of CXCL12, but not CXCR4 mRNA in endometrial explants. Recombinant CXCL12 (rCXCL12) protein dose-dependently increased migration of cultured porcine trophectoderm cells and peripheral blood mononuclear cells (PBMCs). Furthermore, rCXCL12 caused migration of T cells, but not natural killer cells, in PBMCs. This study revealed that interferon-γ-induced CXCL12 and its receptor, CXCR4, were expressed at the maternal-conceptus interface and increased the migration of trophectoderm cells and T cells at the time of implantation in pigs. These results suggest that CXCL12 may be critical for the establishment of pregnancy by regulating trophoblast migration and T cell recruitment into the endometrium during the implantation period in pigs.

Intrauterine inhibition of chemokine receptor 4 signaling modulates local and systemic inflammation in ovine pregnancy

PROBLEM

Chemokines help coordinate inflammation within the fetal-maternal microenvironment during gestation. The chemokine CXCL12 signaling through its receptor CXCR4 regulates inflammatory activity, but this phenomenon is not well understood during pregnancy, and there are no reports exploring the role of this pair in peripheral immune tolerance during gestation. Herein, we hypothesize that intrauterine CXCL12-CXCR4 signaling governs local and systemic immunomodulatory dynamics during early gestation in ewes.

METHOD OF STUDY

Osmotic pumps were surgically installed for intrauterine infusion of a CXCR4 inhibitor, AMD3100, beginning on day 12 post-breeding in sheep. Endometrial tissues were collected on day 35 of gestation and evaluated for inflammatory potential, Akt pathway activation, and autophagy induction. Demonstrative of peripheral immune activity, levels of select cytokines were assessed in daily blood samples collected throughout the study, as well as in corpus luteum and spleen on day 35.

RESULTS

Anti-inflammatory IL10 was primarily localized to endometrial glandular epithelium with lower abundance when CXCR4 was antagonized. Inhibition of CXCR4 at the fetal-maternal interface resulted in less activation of Akt in endometrium, while evidence of autophagy induction was greater. Corpora lutea from ewes receiving intrauterine AMD3100 exhibited lower interferon-gamma (IFNG) expression. Blood inflammatory potential was differentially altered in a temporal fashion throughout infusion. IL10 abundance in spleen was greater following CXCR4 inhibition at the fetal-maternal interface, while IFNG was less.

CONCLUSION

Intrauterine CXCL12-CXCR4 signaling governs endometrial and systemic inflammation; disruption of this axis may have detrimental impacts on offspring and maternal health.

Effect of metabolic status on conceptus-maternal interactions on day 19 in dairy cattle: II. Effects on the endometrial transcriptome

The aim of this study was to test the hypothesis that the metabolic stresses associated with lactation alter the ability of the endometrium to respond appropriately to the conceptus by examining endometrial gene expression on day 19 of pregnancy. Immediately after calving, primiparous Holstein cows with similar production and fertility estimated breeding values were randomly divided into two groups and either dried off (i.e. never milked) immediately or milked twice daily. Approximately 65-75 days postpartum, grade 1 blastocysts recovered from superovulated Holstein heifer donors (n = 5) were transferred (1 per recipient) into lactating (n = 11) and nonlactating (n = 11) recipients. Control nulliparous Holstein heifers (n = 6) were artificially inseminated. RNA-sequencing was performed on intercaruncular endometrial samples recovered at slaughter from confirmed pregnant animals on day 19 (n = 5 lactating and nonlactating cows; n = 4 heifers). Differentially expressed genes (DEGs) were identified between both postpartum groups compared to heifers and between lactating and nonlactating cows. Functional annotation of DEGs between cows and heifers revealed over-representation of categories, including endosome, cytoplasmic vesicle, endocytosis, regulation of exocytosis, and cytokine receptor activity. Functional categories including transcription factor binding sites, cell motility, and cell migration were enriched for DEGs between endometria from lactating and nonlactating cows. In conclusion, while the evidence for a major effect of lactation on the endometrial transcriptome is relatively weak, these data suggest that the metabolic status of the animal (heifer vs cow) modulates the response of the endometrium to the developing conceptus.

In the ovine pituitary, CXCR4 is localized in gonadotropes and somatotropes and increases with elevated serum progesterone

The pituitary is the central endocrine regulator of reproduction and in addition to various hormones regulating its actions, other molecules, such as chemokines, influence pituitary physiology as well. Despite reports over 2 decades ago that chemokines regulate the pituitary, much of the basic biology discerning chemokine action in the pituitary is unclear. A small number of chemokines and their receptors have been localized to the pituitary, yet chemokine ligand 12 (CXCL12) and its receptor, CXCR4, have received the most attention as both are increased in human pituitary adenomas. This chemokine duo was also reported in normal human and rat pituitary, suggestive of a functional role and that this chemokine axis might function in pituitaries from other mammalian species. To date, reports of CXCL12 and CXCR4 in pituitary from livestock are lacking, and research on pituitary during pregnancy in any mammalian species is limited. Moreover, progesterone regulates CXCR4 expression in a tissue-dependent manner, but whether differing concentrations of progesterone reaching the pituitary modulate CXCL12 or CXCR4 is not known. To address these gaps, our first objective was to determine if CXCL12 and CXCR4 expression and protein abundance differ in sheep pituitary during early gestation (days 20, 25, and 30 of gestation) compared to nonpregnant ewes. The second objective was to determine if CXCL12 or CXCR4 production was altered in the ovine pituitary when circulating progesterone concentrations are elevated. The expression of CXCL12 messenger RNA decreased on day 20 of gestation compared to nonpregnant ewes; CXCL12 protein was similar across all days tested. In nonpregnant and pregnant ewes, CXCR4 was localized to somatotropes and gonadotropes on all days tested. Abundance of CXCR4 increased in the pituitary tissue of pregnant ewes with elevated circulating progesterone compared with pregnant ewes with normal circulating progesterone concentrations (control). The present study details CXCL12 and CXCR4 in normal ovine pituitary and reveals that gonadotropes and somatotropes may be regulated by CXCL12/CXCR4, underscoring this signaling axis as a potential new class of modulator in endocrine functions.

Lowering the concentration affects the migration and viability of intracerebroventricular-delivered human mesenchymal stem cells

Due to their widely known therapeutic benefits, mesenchymal stem cells have been proposed as a novel treatment option for a wide range of diseases including Alzheimer's disease. To maximize these benefits, critical factors such as delivery route, cell viability, and cell migration must be accounted for. Out of the various delivery routes to the brain, the intracerebroventricular (ICV) route stands out due to the widespread distribution that can occur via cerebrospinal fluid flow. The major objective of this present study was to observe how altering cell concentration influences the migration and viability of human umbilical cord blood derived-mesenchymal stem cells (hUCB-MSCs), delivered via ICV injection, in the brains of wild-type (WT) mice. C3H/C57 WT mice were divided into three groups and were injected with 1 × 10⁵ hUCB-MSCs suspended in varying volumes: high (3 μl), middle (5 μl), and low (7 μl) concentrations, respectively. Lowering the concentration increased the migratory capabilities and elevated the viability of hUCB-MSCs. These results suggest that cell concentration can affect the physiological state of hUCB-MSCs, and thus the extent of therapeutic efficacy that can be achieved.

Inhibition of chemokine (C-X-C motif) receptor four (CXCR4) at the fetal-maternal interface during early gestation in sheep: alterations in expression of chemokines, angiogenic factors and their receptors

Chemokine (C-X-C motif) ligand 12 (CXCL12) and its receptor, chemokine (C-X-C motif) receptor 4 (CXCR4), are involved in significant biological processes associated with early pregnancy including increasing trophoblast invasion and stimulating placental vascularization. To further elucidate functions of CXCL12-CXCR4 signaling during early gestation, our objective was to inhibit CXCR4 in vivo using a CXCR4 antagonist, AMD3100. We hypothesized that inhibition of CXCR4 would negatively affect chemokine and angiogenic factor regulation imperative for placental development in sheep. Osmotic pumps containing PBS (control) or AMD3100 (CXCR4 antagonist) were surgically installed ipsilateral to the corpus luteum on d 12 of gestation and administered treatments directly into the uterine lumen. Maternal (caruncle and intercaruncle) and fetal membrane tissues were collected on d 23 of gestation and mRNA and protein expression were analyzed for vascular endothelial growth factor (VEGF), kinase insert domain receptor (KDR), fms related tyrosine kinase 1 (FLT1), fibroblast growth factor 2 (FGF2), angiopoietin 1 (ANGPT1), hypoxia inducible factor 1 ɑ subunit (HIF1A), CXCL12, and its corresponding receptors (CXCR4 and CXCR7). Immunohistochemical procedures were performed for analysis of CXCL12 and cell proliferation. In caruncle tissue ipsilateral to the pump, mRNA for KDR, ANGPT1, HIF1A, and CXCL12 increased (P < 0.05) in treated ewes compared to control, whereas caruncle tissue contralateral to the pump had increased expression (P < 0.05) of KDR, and CXCL12 in treated ewes. In fetal membrane, CXCR4 mRNA and protein decreased (P < 0.05), while VEGF protein decreased (P < 0.05) in caruncle and fetal membrane tissue from treated ewes. Results from this study highlight the importance of CXCL12-CXCR4 signaling at the fetal-maternal interface. Inhibiting this axis may disrupt typical regulation of angiogenic factors needed for placental development and embryo growth.

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.

Citrullination regulates the expression of insulin-like growth factor-binding protein 1 (IGFBP1) in ovine uterine luminal epithelial cells

There are five peptidylarginine deiminase (PAD) isozymes designated as PADs 1, 2, 3, 4 and 6, and many are expressed in female reproductive tissues. These enzymes post-translationally convert positively charged arginine amino acids into neutral citrulline residues. Targets for PAD-catalyzed citrullination include arginine residues on histone tails, which results in chromatin decondensation and changes in gene expression. Some of the first studies examining PADs found that they are localized to rodent uterine epithelial cells. Despite these findings, the function of PAD-catalyzed citrullination in uterine epithelial cells is still unknown. To address this, we first examined PAD expression in uterine cross-sections from pregnant ewes on gestation day 25 (d25). Immunohistochemistry revealed that the levels of PADs 2 and 4 are robust in luminal and glandular epithelia compared with those of PADs 1 and 3. As PADs 2 and 4 have well-characterized roles in histone citrullination, we next hypothesized that PADs citrullinate histones in these uterine cells. Examination of caruncle lysates from pregnant ewes on gestation d25 and an ovine luminal epithelial (OLE) cell line shows that histone H3 arginine residues 2, 8, 17 and 26 are citrullinated, but histone H4 arginine 3 is not. Using a pan-PAD inhibitor, we next attenuated histone citrullination in OLE cells, which resulted in a significant decrease in the expression of insulin-like growth factor-binding protein 1 (IGFBP1) mRNA. As IGFBP1 is important for the migration and attachment of the trophectoderm to uterine endometrium, our results suggest that PAD-catalyzed citrullination may be an important post-translational mechanism for the establishment of pregnancy in ewes.

Diagnostic Potential of Evaluation of SDF-1α and sRAGE Levels in Threatened Premature Labor

Preterm birth remains the most prevalent cause of neonatal morbidity. This study aimed to evaluate the diagnostic value of SDF-1α, resistin, secretory RAGE (sRAGE), and endogenous secretory RAGE (esRAGE) in preterm labor. A total of 211 pregnant women participated in the study. Group A contained 72 women between 22 and 36 weeks of gestation, with premature labor, who finally had preterm birth. Group B contained 66 women in labor between 37 and 41 weeks of gestation. Women in group A had lower SDF-1α and sRAGE levels than those in group B. Moreover, in group A, SDF-1α and sRAGE levels were correlated with the latency period from the occurrence of premature labor symptoms until delivery. Sensitivity and specificity of studied parameters for prediction of preterm birth were 95% and 40% for SDF-1α and 51.3% and 93.5% for sRAGE, respectively. The prognostic value of plasma SDF-1α and sRAGE levels was comparable with that of cervical length ultrasound measurement and serum C-reactive protein levels. We conclude that SDF-1α and sRAGE appear to play a major role in the diagnosis of preterm birth and its evaluation could be convenient and useful for predicting preterm birth.

Placental development during early pregnancy: Effects of embryo origin on expression of chemokine ligand twelve (CXCL12)

The aim was to localize chemokine ligand twelve (CXCL12) in sheep placental tissues during early gestation and after assisted reproductive technologies (ART). Uteri were collected from naturally (NAT) mated ewes and ewes receiving embryo transfer (ET), in vitro fertilization (IVF) or in vitro activation (IVA). CXCL12 was immunolocalized to endometrial stroma, glands, and trophoblast. Greater CXCL12 immunoreactivity was present in trophoblast on day 22 and 24 and in NAT ewes compared to IVF and IVA. Increased CXCL12 expression suggests CXCL12 promotes implantation and placentation. Decreased CXCL12 in IVF and IVA embryos, may compromise pregnancy establishment when utilizing ART methods.

CXCR4, CXCR7, and CXCL12 are associated with trophoblastic cells apoptosis and linked to pathophysiology of severe preeclampsia

Preeclampsia is a pregnancy disorder with sudden onset of maternal hypertension and proteinuria, which is characterized by defective cytotrophoblast invasion, increased apoptosis in cytotrophoblast, and diminished syncytial differentiation. In this study, samples from 11 mild preeclamptic patients, 18 severe preeclamptic patients, and 21 normal pregnant women were collected. The expression level of CXCL12 and its two receptors (CXCR4 and CXCR7) in these samples and their relationship with apoptosis were investigated. Morphological change of trophoblast cells that was observed by scanning electron microscope (SEM) indicated a significant tendency of apoptosis in the preeclamptic placenta. Immunohistochemical staining showed that expression level of three proteins was significantly lower in severe preeclamptic placentas compared with normal placentas (P<0.05), whereas no significant difference was found between mild preeclamptic and normal placentas (P>0.05). Real time quantitative PCR (RT-qPCR) and Western blot showed that both mRNA and protein expression level of CXCR4, CXCR7, and CXCL12 of trophoblasts were lower in the severe preeclampsia group than that in the normal group (P<0.05 for mRNA, P<0.01 for protein). In conclusion, our data revealed that the roles of CXCR4, CXCR7, and CXCL12 are associated with trophoblastic cells apoptosis and may be linked to the occurrence and development of severe preeclampsia.

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.