VEGFR-1 blockade disrupts peri-implantation decidual angiogenesis and macrophage recruitment

Does cabergoline administration affect endometrial VEGFR-2 expression in a rat model of ovarian hyperstimulation syndrome?

OBJECTIVE

To assess the effect of cabergoline on endometrial vascular endothelial growth factor receptor-2 (VEGFR-2) immunoexpression in an ovarian hyperstimulation syndrome (OHSS) rat model.

MATERIAL AND METHODS

Twenty-one immature female Wistar rats were assigned into three groups: group 1, the control group; group 2, stimulated with gonadotropins to mimic OHSS; and group 3, in which an OHSS protocol was induced and thereafter treated with cabergoline (100 μg/kg/day). Body weight, ovarian volume, corpora lutea numbers, and endometrial VEGFR-2 expression were compared between the groups.

RESULTS

Weight gain and ovarian volume were highest in the OHSS-placebo group, while cabergoline administration significantly reversed those effects (p = 0.001 and p = 0.001, respectively). VEGFR-2 stained cells were significantly lower in groups 2 and 3 compared to group 1 (p = 0.002). Although VEGFR-2 expression was lowest in group 3, the difference was not statistically significant. Corpora lutea numbers were also similar (p = 0.465).

CONCLUSION

While successful implantation requires a vascularized receptive endometrium, impaired expression of VEGFR-2 and disrupted endometrial angiogenesis due to cabergoline administration may be associated with IVF failure in fresh OHSS cycles. The insignificant decrease in endometrial VEGFR-2 expression observed in this research needs to be investigated by further studies involving additional techniques such as immunoblotting and/or RT-PCR analyses.

Vascular changes in the cycling and early pregnant uterus

Uterine vascular remodeling is intrinsic to the cycling and early pregnant endometrium. Maternal regulatory factors such as ovarian hormones, VEGF, angiopoietins, Notch, and uterine natural killer cells significantly mediate these vascular changes. In the absence of pregnancy, changes in uterine vessel morphology and function correlate with different stages of the human menstrual cycle. During early pregnancy, vascular remodeling in rodents and humans results in decreased uterine vascular resistance and increased vascular permeability necessary for pregnancy success. Aberrations in these adaptive vascular processes contribute to increased risk of infertility, abnormal fetal growth, and/or preeclampsia. This Review comprehensively summarizes uterine vascular remodeling in the human menstrual cycle, and in the peri- and post-implantation stages in rodent species (mice and rats).

Single-Cell RNA-Sequencing Reveals Interactions between Endometrial Stromal Cells, Epithelial Cells, and Lymphocytes during Mouse Embryo Implantation

The decidualization of endometrial stromal cells (ESCs) is an essential process facilitating embryo implantation. However, the roles of non-decidualized and decidualized ESCs in regulating the microenvironment of a receptive endometrium remain unclear. We investigated single-cell transcriptomic changes in the uterus of a CD-1 mouse model at the post-implantation stage. The implantation and inter-implantation sites of the uteruses of pregnant mice at 4.5 and 5.5 days post-coitum were dissected for single-cell RNA sequencing. We identified eight cell types: epithelial cells, stromal cells, endothelial cells, mesothelial cells, lymphocytes, myocytes, myeloids, and pericytes. The ESC transcriptome suggests that the four ESC subtypes are involved in the extracellular remodeling during implantation. The trajectory plot of ESC subtypes indicates embryo implantation that involves a differentiation pathway from undifferentiated ESCs (ESC 1) to decidualized ESCs (DEC ESCs), with distinct signaling pathways between the ESC subtypes. Furthermore, the ligand-receptor analysis suggests that ESCs communicate with epithelial cells and immune cells through nectin and ICAM signaling. Collectively, both decidualized and non-decidualized ESCs may regulate the endometrial microenvironment for optimal endometrial receptivity and immune tolerance. This study provides insights on the molecular and cellular characteristics of mouse ESCs in modulating the epithelial and lymphocyte functions during early embryo implantation.

miR-146a-5p enhances embryo survival in unexplained recurrent spontaneous abortion by promoting M2 polarization of decidual macrophages

Unexplained recurrent spontaneous abortion (URSA) is one of the most challenging conditions in the reproductive field, and macrophage M1/M2 polarization disorder is involved in URSA pathogenesis, although the relevant mechanisms are undefined. miR-146a-5p possesses an immunoregulatory role and is expressed in decidual immune cells, and this study aims to investigate its effect on decidual macrophage polarization and therapeutic prospects in URSA, which has never been reported. The levels of M1/M2 markers in the deciduae and the miR-146a-5p expression in the decidual macrophages of URSA and healthy pregnant women were first detected and analyzed. Then, the in vitro effect of miR-146a-5p on the M1/M2 polarization and the secretion of inflammatory cytokines was investigated in Tamm-Horsfall protein-1 (THP-1)-induced macrophages. Finally, the in vivo immunotherapeutic effect of miR-146a-5p on embryo survival and the potential mechanisms were evaluated in a murine model of immune-based URSA. As a result, the abnormal M1/M2 polarization, which showed a shift towards the M1 phenotype and correlated with the decreased expression of miR-146a-5p, was verified in human URSA decidual macrophages. miR-146a-5p could inhibit M1 polarization, promote M2 polarization, and result in an anti-inflammatory microenvironment in THP-1-induced macrophages. The intravenous injection of exogenous miR-146a-5p in the first trimester of pregnant URSA mice significantly reduced the embryo resorption rate and promoted the M2 polarization of decidual macrophages. In conclusion, miR-146a-5p enhances embryo survival in URSA by promoting decidual macrophage polarization toward an M2 phenotype, giving new ideas and potential targets for subsequent research on the pathogenesis and immunotherapeutic strategies of URSA.

The physiological and pathological functions of VEGFR3 in cardiac and lymphatic development and related diseases

Vascular endothelial growth factor receptors (VEGFRs) are part of the evolutionarily conserved VEGF signalling pathways that regulate the development and maintenance of the body's cardiovascular and lymphovascular systems. VEGFR3, encoded by the FLT4 gene, has an indispensable and well-characterized function in development and establishment of the lymphatic system. Autosomal dominant VEGFR3 mutations, that prevent the receptor functioning as a homodimer, cause one of the major forms of hereditary primary lymphoedema; Milroy disease. Recently, we and others have shown that FLT4 variants, distinct to those observed in Milroy disease cases, predispose individuals to Tetralogy of Fallot, the most common cyanotic congenital heart disease, demonstrating a novel function for VEGFR3 in early cardiac development. Here, we examine the familiar and emerging roles of VEGFR3 in the development of both lymphovascular and cardiovascular systems, respectively, compare how distinct genetic variants in FLT4 lead to two disparate human conditions, and highlight the research still required to fully understand this multifaceted receptor.

Histone deacetylase 9 deficiency exaggerates uterine M2 macrophage polarization

The maternal‐foetal interface is an immune‐privileged site where the semi‐allogeneic embryo is protected from attacks by the maternal immune system. Uterine macrophages are key players in establishing and maintaining pregnancy, and the dysregulation of the M1‐M2 subpopulation balance causes abortion. We separated two distinct mouse uterine macrophage subpopulations during early pregnancy, CD45⁺F4/80⁺CD206⁻ M1‐like (M1) and CD45⁺F4/80⁺CD206⁺ M2‐like (M2) cells. The M1 preponderance was significantly exaggerated at 6 hours after lipopolysaccharide (LPS) treatment, and adoptive transfer of M2 macrophages partially rescued LPS‐induced abortion. RNA sequencing analysis of mouse uterine M2 versus M1 revealed 1837 differentially expressed genes (DEGs), among which 629 was up‐regulated and 1208 was down‐regulated. Histone deacetylase 9 (Hdac9) was one of the DEGs and validated to be significantly up‐regulated in uterine M2 as compared with M1. Remarkably, this differential expression profile between M1 and M2 was also evident in primary splenic macrophages and in vitro polarized murine peritoneal, bone marrow–derived and RAW 264.7 macrophages. In Hdac9/HDAC9 knockout RAW 264.7 and human THP‐1–derived macrophages, the expression of M1 differentiation markers was unchanged or decreased whereas M2 markers were increased compared with the wild‐type cells, and these effects were unrelated to compromised proliferation. Furthermore, Hdac9/HDAC9 ablation significantly enhanced the phagocytosis of fluorescent microspheres in M2 Raw 264.7 cells yet decreased the capacity of THP‐1‐derived M1 macrophages. The above results demonstrate that Hdac9/HDAC9 deficiency exaggerates M2 macrophage polarization in mouse and human macrophages, which may provide clues for our understanding of the epigenetic regulation on macrophage M1/M2 polarization in maternal‐foetal tolerance.

Contribution of macrophages to fetomaternal immunological tolerance

The semi-allogeneic fetus develops in a uniquely immune tolerant environment within the uterus. For successful pregnancy, both the innate and adaptive immune systems must favor acceptance of the fetal allograft. Macrophages are the second most abundant immune cells after natural killer (NK) cells in the decidua. In coordination with decidual NK cells and dendritic cells, macrophages aid in implantation, vascular remodeling, placental development, immune tolerance to placental cells, and maintenance of tissue homeostasis at the maternal-fetal interface. Decidual macrophages show the classical activated (M1) and alternatively activated (M2) phenotypes under the influence of the local milieu of growth factors and cytokines, and appropriate temporal regulation of the M1/M2 switch is vital for successful pregnancy. Disturbances in the mechanisms that control the M1/M2 balance and associated functions during pregnancy can trigger a spectrum of pregnancy complications ranging from preeclampsia and fetal growth restriction to preterm delivery. This review addresses various mechanisms of tolerance, focusing on the basic biology of macrophages, their plasticity and polarization, and their protective roles at the immune-privileged maternal-fetal interface, including direct and indirect roles in promoting fetomaternal immune tolerance.

CD206+ M2-Like Macrophages Are Essential for Successful Implantation

Macrophages (MΦs) play important roles in implantation. Depletion of CD11b+ pan-MΦs in CD11b-diphtheria-toxin-receptor (DTR) mice is reported to cause implantation failure due to decreased progesterone production in the corpus luteum. However, of the M1 and M2, the type of MΦs that is important for implantation is unknown. In this study, we investigated the role of M2 MΦ in implantation using CD206-DTR mice. To deplete M2-MΦ, female CD206-DTR C57/BL6 mice were injected with DT before implantation. These M2-MΦ depleted mice (M2(-)) were naturally mated with Balb/C mice. As the control group, female C57/BL6 wild type (WT) mice injected with DT were mated with male Balb/C mice. The number of implantation sites and plasma progesterone levels at implantation were examined. Implantation-related molecule expression was determined using quantitative-PCR and immunohistochemistry of uterine tissues. The mRNA expression in the endometrial tissues of 38 patients with implantation failure was examined during the implantation window. In WT mice, CD206+M2-like MΦs accumulated in the endometrium at the implantation period, on embryonic (E) 4.5. In M2(-), the implantation number was significantly lower than that in control (p < 0.001, 7.8 ± 0.8 vs. 0.2 ± 0.4), although the plasma progesterone levels were not changed. Leukemia inhibitory factor (LIF) and CD206 mRNA expression was significantly reduced (p < 0.01), whereas the levels of TNFα were increased on E4.5 (p < 0.05). In M2(-), the number of Ki-67+ epithelial cells was higher than that in control at the pre-implantation period. Accelerated epithelial cell proliferation was confirmed by significantly upregulated uterine fibroblast growth factor (FGF)18 mRNA (P < 0.05), and strong FGF18 protein expression in M2(-) endometrial epithelial cells. Further, M2(-) showed upregulated uterine Wnt/β-catenin signals at the mRNA and protein levels. In the non-pregnant group, the proportion of M2-like MΦ to pan MΦ, CD206/CD68, was significantly reduced (p < 0.05) and the TNFα mRNA expression was significantly increased (p < 0.05) in the endometrial tissues compared to those in the pregnant group. CD206+ M2-like MΦs may be essential for embryo implantation through the regulation of endometrial proliferation via Wnt/β-catenin signaling.

Gene-activated dermal equivalents to accelerate healing of diabetic chronic wounds by regulating inflammation and promoting angiogenesis

Diabetic chronic wound, characterized by prolonged inflammation and impaired angiogenesis, has become one of the most serious challenges in clinic and pose a significant healthcare burden worldwide. Although a great variety of wound dressings have been developed, few of encouraged achievements were obtained so far. In this study, the gene-activated strategy was applied to enhance sustained expression of vascular endothelial growth factor (VEGF) and achieve better healing outcomes by regulating inflammation and promoting angiogenesis. The gene-activated bilayer dermal equivalents (Ga-BDEs), which has good biocompatibility, were fabricated by loading the nano-sized complexes of Lipofectamine 2000/plasmid DNA-encoding VEGF into a collagen-chitosan scaffold/silicone membrane bilayer dermal equivalent. The DNA complexes were released in a sustained manner and showed the effective transfection capacities to up-regulate the expression of VEGF in vitro. To overcome cutaneous contraction of rodents and mimic the wound healing mechanisms of the human, a reformative rat model of full-thickness diabetic chronic wound was adopted. Under the treatment of Ga-BDEs, speeding wound healing was observed, which is accompanied by the accelerated infiltration and phenotype shift of macrophages and enhanced angiogenesis in early and late healing phases, respectively. These proved that Ga-BDEs possess the functions of immunomodulation and pro-angiogenesis simultaneously. Subsequently, the better regeneration outcomes, including deposition of oriented collagen and fast reepithelialization, were achieved. All these results indicated that, being different from traditional pro-angiogenic concept, the up-regulated expression of VEGF by Ga-BDEs in a sustained manner shows versatile potentials for promoting the healing of diabetic chronic wounds.

Trophoblast attachment to the endometrial epithelium elicits compartment-specific transcriptional waves in an in-vitro model

RESEARCH QUESTION

Which are the early compartment-specific transcriptional responses of the trophoblast and the endometrial epithelium throughout early attachment during implantation?

DESIGN

An endometrial epithelium proxy (cell line Ishikawa) was co-cultured with spheroids of a green fluorescent protein (GFP) expressing trophoblast cell line (JEG-3). After 0, 8 and 24 h of co-culture, the compartments were sorted by fluorescence-activated cell sorting; GFP+ (trophoblast), GFP- (epithelium) and non-co-cultured control populations were analysed (in triplicate) by RNA-seq and gene set enrichment analysis (GSEA).

RESULTS

Trophoblast challenge induced a wave of transcriptional changes in the epithelium that resulted in 295 differentially regulated genes involving epithelial to mesenchymal transition (EMT), cell movement, apoptosis, hypoxia, inflammation, allograft rejection, myogenesis and cell signalling at 8 h. Interestingly, many of the enriched pathways were subsequently de-enriched by 24 h (i.e. EMT, cell movement, allograft rejection, myogenesis and cell signalling). In the trophoblast, the co-culture induced more transcriptional changes and regulation of a variety of pathways. A total of 1247 and 481 genes were differentially expressed after 8 h and from 8 to 24 h, respectively. Angiogenesis and hypoxia were over-represented at both stages, while EMT and cell signalling only were at 8 h; from 8 to 24 h, inflammation and oestrogen response were enriched, while proliferation was under-represented.

CONCLUSIONS

Successful attachment produced a series of dynamic changes in gene expression, characterized by an overall early and transient transcriptional up-regulation in the receptive epithelium, in contrast to a more dynamic transcriptional response in the trophoblast.

Decreased ANGPTL4 impairs endometrial angiogenesis during peri-implantation period in patients with recurrent implantation failure

Insufficient endometrial angiogenesis during peri-implantation impairs endometrial receptivity (ER), which contributes to recurrent implantation failure (RIF) during in vitro fertilization and embryo transfer (IVF-ET). Angiopoietin-like protein 4 (ANGPTL4) acts as a multifunctional secretory protein and is involved in the regulation of lipid metabolism and angiogenesis in various tissues including the endometrium. Herein, we found decreased ANGPTL4 expression in endometrial tissue and serum during peri-implantation period in 18 RIF-affected women with elevated uterine arterial impedance (UAI) compared with the pregnancy controls. ANGPTL4 and peroxisome proliferator-activated receptor gamma (PPARγ) expression were up-regulated upon decidualization on human endometrial stromal cells (HESCs). Rosiglitazone promoted the expression of ANGPTL4 in HESCs and human umbilical vein endothelial cells (HUVECs) via PPARγ. ANGPTL4 promoted the proliferation, migration and angiogenesis of HUVECs in vitro. Our results suggest that decreased abundance of ANGPTL4 in endometrial tissues impairs the endometrial receptivity via restraining endometrial angiogenesis during decidualization; while rosiglitazone-induced ANGPTL4 up-regulation in hESCs and HUVECs through PPARγ. Therefore, ANGPTL4 could be a potential therapeutic approach for some RIF-affected women with elevated UAI.

Effect of soy isoflavones on implantation losses in Wistar rat: implication of progesterone receptors, vascular endothelial growth factor and estradiol receptors alpha

BACKGROUND

Implantation is a crucial period determining the success of a full pregnancy. Endocrine disruptors such as phytoestrogens (PEs) were thought to adversely influence embryonic implantations. However, the mechanism by which they upset implantation was not fully elucidated.

AIMS

The effect of administering soy isoflavones on the implantation of Wistar rats was studied through the detection of progesterone receptors (PR), vascular endothelial growth factor (VEGF), and estradiol receptor alpha (ER-α) protein expression at gestation day 6 (GD6).

METHODS

Eighteen cyclic female Wistar rats were distributed into two groups, group A: control (n=9) were fed with a casein based diet, and group B (n=9) were fed with a casein diet and gavaged 50 mg/kg/day soy isoflavones' extract 40% starting from gestation day zero (GD0) to GD6. Feed intake, body weight (BW), body gain, and uterine weights were recorded. At the end of GD6 the number of corpora lutae (CLs) and implantation rates were recorded. Histopathology and immunohistochemistry (IHC) for PR, VEGF, and ER-α protein expression in implanted uteri were performed.

RESULTS

Soy isoflavones significantly reduced feed intake, weight gain, uterine weights CL numbers, and implantation rates of the treated pregnant dams. The endometrium of the soy treated dams showed less proliferation than that of the control. Immunostaining percentage of PR and VEGF proteins significantly reduced in soy treated dams compared to the control. However, the mean expression percentage of ER-α exhibited significant elevation in the soy treated dams in comparison to the control group.

CONCLUSION

Implantation losses caused by soy isoflavones seemed to be due to the down regulation of PR that failed to down regulate ER-α action and decreased VEGF production.

Hypoxia modifies the polarization of macrophages and their inflammatory microenvironment, and inhibits malignant behavior in cancer cells

Macrophages are a heterogeneous group of phagocytes that play critical roles in inflammation, infection and tumor growth. Macrophages respond to different environmental factors and are thereby polarized into specialized functional subsets. Although hypoxia is an important environmental factor, its impact on human macrophage polarization and subsequent modification of the inflammatory microenvironment have not been fully established. The present study aimed to elucidate the effect of hypoxia exposure on the ability of human macrophages to polarize into the classically activated (pro-inflammatory) M1, and the alternatively activated (anti-inflammatory) M2 phenotypes. The effect on the inflammatory microenvironment and the subsequent modification of A549 lung carcinoma cells was also investigated. The presented data show that hypoxia promoted macrophage polarization towards the M2 phenotype, and modified the inflammatory microenvironment by decreasing the release of proinflammatory cytokines. Modification of the microenvironment by proinflammatory M1 macrophages under hypoxia reversed the inhibition of malignant behaviors within the proinflammatory microenvironment. Furthermore, it was identified p38 signaling (a major contributor to the response to reactive oxygen species generated by hypoxic stress), but not hypoxia-induced factor, as a key regulator of macrophages under hypoxia. Taken together, the data suggest that hypoxia affects the inflammatory microenvironment by modifying the polarization of macrophages, and thus, reversing the inhibitory effects of a proinflammatory microenvironment on the malignant behaviors of several types of cancer cell.

Role of Macrophages in Pregnancy and Related Complications

Macrophages (MФs) are the leukocytes produced from differentiation of monocytes and are located in almost all tissues of human body. They are involved in various processes, such as phagocytosis, innate and adaptive immunity, proinflammatory (M1) and anti-inflammatory (M2) activity, depending on the tissue microenvironment. They play a crucial role in pregnancy, and their dysfunction or alteration of polarity is involved in pregnancy disorders, like preeclampsia, recurrent spontaneous abortion, infertility, intrauterine growth restriction, and preterm labor. About 50-60% of decidual leukocytes are natural killer (NK) cells followed by MФs (the second largest population). MФs are actively involved in trophoblast invasion, tissue and vascular remodeling during early pregnancy, besides their role as major antigen-presenting cells in the decidua. These cells have different phenotypes and polarities in different stages of pregnancy. They have also been observed to enhance tumor growth by their anti-inflammatory activity (M2 type) and prevent immunogenic rejection. Targeted alteration of polarity (M1-M2 or vice versa) could be a major focus in the future treatment of pregnancy complications. This review is focused on the role of MФs in pregnancy, their involvement in pregnancy disorders, and decidual MФs as possible therapeutic targets for the treatment of pregnancy complications.

The role of maternal T cell and macrophage activation in preterm birth: Cause or consequence?

The role of the immune system in term (TL) and preterm labor (PTL) is unknown. Despite the fact that globally, PTL remains the most important cause of childhood mortality. Infection, typically of the fetal membranes, termed chorioamnionitis, is the best-understood driver of PTL, but the mechanisms underpinning other causes, including idiopathic and stretch-induced PTL, are unclear, but may well involve activation of the maternal immune system. The final common pathway of placental dysfunction, fetal membrane rupture, cervical dilation and uterine contractions are highly complex processes. At term, choriodecidual rather than myometrial inflammation is thought to drive the onset of labor and similar findings are present in different types of PTL including idiopathic PTL. Although accumulated data has confirmed an association between the immune response and preterm birth, there is yet a need to understand if this response is an initiator or a consequence of tissue-level dysregulation. This review focuses on the potential role of macrophages and T cells in innate and adaptive immunity relevant to preterm birth in humans and animal models.

Innate immune cells in the placental bed in healthy pregnancy and preeclampsia

Immune cells in the placental bed are important for adequate development of the placental bed. The most prominent immune cells in the placental bed early in pregnancy are uterine natural killer cells (uNK) cells and macrophages. Also dendritic cells and mast cells can be found in the early placental bed. These cells not only have an immune regulatory function, but are also involved in the regulation of trophoblast invasion, angiogenesis and spiral artery remodeling. In preeclampsia, one of the major complications of pregnancy, decreased trophoblast invasion and spiral artery remodeling has been found. This is associated with decreased numbers of uNK cells, increased numbers of macrophages around the spiral arteries and similar or increased numbers of dendritic cells in the placental bed. In this review, we discuss the current insights in the functions of uNK cells, macrophages, dendritic cells and mast cells in the placental bed in humans during healthy pregnancy and during preeclampsia. As animal models are instrumental in understanding the role of immune cells in the placental bed, we also review studies on the function and phenotype of these innate immune cells in experimental preeclampsia. A better understanding of the dynamics and functional changes of these immune cells in the placental bed may eventually lead to new therapeutic targets for preeclampsia.

VEGF may contribute to macrophage recruitment and M2 polarization in the decidua

It is increasingly evident that cytokines and growth factors produced in the decidua play a pivotal role in the regulation of the local immune microenvironment and the establishment of pregnancy. One of the major growth factors produced in the decidua is vascular endothelial growth factor (VEGF), which acts not only on endothelial cells, but also on multiple other cell types, including macrophages. We sought to determine whether decidua-derived VEGF affects macrophage recruitment and polarization using human endometrial/decidual tissue samples, primary human endometrial stromal cells (ESCs), and the human monocyte cell line THP1. In situ hybridization was used for assessment of local VEGF expression and immunohistochemistry was used for identification and localization of CD68-positive endometrial macrophages. Macrophage migration in culture was assessed using a transwell migration assay, and the various M1/M2 phenotypic markers and VEGF expression were assessed using quantitative real-time PCR (qRT-PCR). We found dramatic increases in both VEGF levels and macrophage numbers in the decidua during early pregnancy compared to the secretory phase endometrium (non-pregnant), with a significant increase in M2 macrophage markers, suggesting that M2 is the predominant macrophage phenotype in the decidua. However, decidual samples from preeclamptic pregnancies showed a significant shift in macrophage phenotype markers, with upregulation of M1 and downregulation of M2 markers. In THP1 cultures, VEGF treatment significantly enhanced macrophage migration and induced M1 macrophages to shift to an M2 phenotype. Moreover, treatment with conditioned media from decidualized ESCs induced changes in macrophage migration and polarization similar to that of VEGF treatment. These effects were abrogated by the addition of a potent VEGF inhibitor. Together these results suggest that decidual VEGF plays a significant role in macrophage recruitment and M2 polarization, and that inhibition of VEGF signaling may contribute to the shift in macrophage polarity observed in different pregnancy disorders, including preeclampsia.

Angiogenic factor imbalance precedes complement deposition in placentae of the BPH/5 model of preeclampsia

Preeclampsia (PE), a hypertensive disorder of pregnancy, is a leading cause of maternal and fetal morbidity and mortality. Although the etiology is unknown, PE is thought to be caused by defective implantation and decidualization in pregnancy. Pregnant blood pressure high (BPH)/5 mice spontaneously develop placentopathies and maternal features of human PE. We hypothesized that BPH/5 implantation sites have transcriptomic alterations. Next-generation RNA sequencing of implantation sites at peak decidualization, embryonic day (E)7.5, revealed complement gene up-regulation in BPH/5 vs. controls. In BPH/5, expression of complement factor 3 was increased around the decidual vasculature of E7.5 implantation sites and in the trophoblast giant cell layer of E10.5 placentae. Altered expression of VEGF pathway genes in E5.5 BPH/5 implantation sites preceded complement dysregulation, which correlated with abnormal vasculature and increased placental growth factor mRNA and VEGF₁₆₄ expression at E7.5. By E10.5, proangiogenic genes were down-regulated, whereas antiangiogenic sFlt-1 was up-regulated in BPH/5 placentae. We found that early local misexpression of VEGF genes and abnormal decidual vasculature preceded sFlt-1 overexpression and increased complement deposition in BPH/5 placentae. Our findings suggest that abnormal decidual angiogenesis precedes complement activation, which in turn contributes to the aberrant trophoblast invasion and poor placentation that underlie PE.-Sones, J. L., Merriam, A. A., Seffens, A., Brown-Grant, D.-A., Butler, S. D., Zhao, A. M., Xu, X., Shawber, C. J., Grenier, J. K., Douglas, N. C. Angiogenic factor imbalance precedes complement deposition in placentae of the BPH/5 model of preeclampsia.

Silica nanoparticles inhibit macrophage activity and angiogenesis via VEGFR2-mediated MAPK signaling pathway in zebrafish embryos

The safety evaluation of silica nanoparticles (SiNPs) are getting great attention due to its widely-used in food sciences, chemical industry and biomedicine. However, the adverse effect and underlying mechanisms of SiNPs on cardiovascular system, especially on angiogenesis is still unclear. This study was aimed to illuminate the possible mechanisms of SiNPs on angiogenesis in zebrafish transgenic lines, Tg(fli-1:EGFP) and Albino. SiNPs caused the cardiovascular malformations in a dose-dependent manner via intravenous microinjection. The incidences of cardiovascular malformations were observed as: Pericardial edema > Bradycardia > Blood deficiency. The area of subintestinal vessels (SIVs) was significant reduced in SiNPs-treated groups, accompanied with the weaken expression of vascular endothelial cells in zebrafish embryos. Using neutral red staining, the quantitative number of macrophage was declined; whereas macrophage inhibition rate was elevated in a dose-dependent way. Furthermore, SiNPs significantly decreased the mRNA expression of macrophage activity related gene, macrophage migration inhibitory factor (MIF) and the angiogenesis related gene, vascular endothelial growth factor receptor 2 (VEGFR2). The protein levels of p-Erk1/2 and p-p38 MAPK were markedly decreased in zebrafish exposed to SiNPs. Our results implicate that SiNPs inhibited the macrophage activity and angiogenesis via the downregulation of MAPK singaling pathway.

Exposure to benzo[a]pyrene impairs decidualization and decidual angiogenesis in mice during early pregnancy

Benzo[a]pyrene (BaP) is a ubiquitous environmental persistent organic pollutant and a well-known endocrine disruptor. BaP exposure could alter the steroid balance in females. Endometrium decidualization and decidual angiogenesis are critical events for embryo implantation and pregnancy maintenance during early pregnancy and are modulated by steroids. However, the effect of BaP on decidualization is not clear. This study aimed to explore the effects of BaP on decidualization and decidual angiogenesis in pregnant mice. The result showed that the uteri in the BaP-treated groups were smaller and exhibited an uneven size compared with those in the control group. Artificial decidualization was detected in the uteri of the controls, but weakened decidualization response was observed in the BaP-treated groups. BaP significantly reduced the levels of estradiol, progesterone, and their cognate receptors ER and PR, respectively. The expression of several decidualization-related factors, including FOXO1, HoxA10, and BMP2, were altered after BaP treatment. BaP reduced the expression of cluster designation 34 (CD34), which indicated that the decidual angiogenesis was inhibited by BaP treatment. In addition, BaP induced the downregulation of vascular endothelial growth factor A. These data suggest that oral BaP ingestion compromised decidualization and decidual angiogenesis. Our results provide experimental data for the maternal reproductive toxicity of BaP during early pregnancy, which is very important for a comprehensive risk assessment of BaP on human reproductive health.

Stathmin 1 plays a role in endometrial decidualisation by regulating hypoxia inducible factor-1α and vascular endothelial growth factor during embryo implantation

The aim of the present study was to explore the potential mechanism underlying stathmin 1 (Stmn1) regulation of embryo implantation, as a continuation of previous proteomic research. Adult healthy female mice were mated naturally with fertile males. Murine uterine tissue was collected during the peri-implantation period. Local expression of Stmn1 during embryo implantation was detected by immunohistochemistry (IHC), which showed that Stmn1 was extensively expressed in endometrial glandular epithelium, vascular endothelium, luminal epithelium and the underlying stromal cells at the implantation site on Day 5. The role of Stmn1 during embryo implantation was evaluated by transient knockdown of Stmn1 in vivo using short interference (si) RNA, and some associated factors including Akt, phosphorylated (p-) Akt, hypoxia-inducible factor (HIF)-1α, prolactin (PRL), insulin-like growth factor binding protein (IGFBP) 1 and vascular endothelial growth factor (VEGF) were examined by western blotting analysis and ELISA. The number of embryos implanted after Stmn1-siRNA infusion into the lumen of one uterine horn was lower than that with normal pregnancies (2.2 ± 1.5 vs 8.6 ± 0.5 respectively; P < 0.05). The expression of VEGF, HIF-1α, p-Akt and the decidualisation biomarkers PRL and IGFBP 1 was upregulated at the implantation site on Day 5, but downregulated after Stmn1-siRNA infusion. These findings suggest that during embryo implantation, knockdown of Stmn1 suppresses decidualisation by inhibiting the expression of p-Akt, HIF-1α and VEGF, thus leading to impaired embryo implantation. These findings provide clues for understanding the complicated process of embryo implantation and the potential role of Stmn1 during embryo implantation.

The decidua-the maternal bed embracing the embryo-maintains the pregnancy

The decidua has been known as maternal uterine tissue, which plays essential roles in protecting the embryo from being attacked by maternal immune cells and provides nutritional support for the developing embryo prior to placenta formation. However, there are questions that still remain to be answered: (1) How does the decidua supply nutrition and provide a physical scaffold for the growing embryo, before placental vascular connection is established? (2) How is the balance between preventing an anti-embryo immune response and protecting both embryo and mother from infections established? To understand basic personas in decidual tissues, we review the structure of the decidua composed of terminally differentiated uterine stromal cells, blood vessels, and a number of repertoire of uterine local immune cells, including the well-known uterine natural killer (uNK) cells and recently discovered innate lymphoid cells (ILCs). Decidual macrophages and uterine dendritic cells (DCs) are supposed to modulate adaptive immunity via balancing cytokines and promoting generation of regulatory T (T_reg) cells. During decidualization, vascular and tissue remodeling in the uterus provide nutritional and physical support for the developing embryo. Secretion of various cytokines and chemokines from both the embryo and the decidual cells activates multiple signaling network between the mother and the embryo upon implantation. Defects in the decidual development during early pregnancy result in loss of pregnancy or complications in later gestational stage.

Vascular Notch proteins and Notch signaling in the peri-implantation mouse uterus

Background

Angiogenesis is essential for uterine decidualization, the progesterone-mediated transformation of the uterus allowing embryo implantation and initiation of pregnancy. In the current study, we define the vasculature, expression of Notch proteins and Notch ligands, and Notch activity in both endothelial cells and vascular-associated mural cells of blood vessels in the pre-implantation endometrium and post-implantation decidua of the mouse uterus.

Methods

We used immunofluorescence to determine the expression of Notch in endothelial cells and mural cells by co-staining for the endothelial cell marker, CD31, the pan-mural cell marker, platelet-derived growth factor receptor beta (PDGFR-β), the pericyte markers, neural/glial antigen 2 (NG2) and desmin, or the smooth muscle cell marker, alpha smooth muscle actin (SMA). A fluorescein isothiocyanate-labeled dextran tracer, was used to identify functional peri-implantation vasculature. CBF:H2B-Venus Notch reporter transgenic mice were used to determine Notch activity.

Results

Notch signaling is observed in endothelial cells and pericytes in the peri-implantation uterus. Prior to implantation, Notch1, Notch2 and Notch4 and Notch ligand, Delta-like 4 (Dll4) are expressed in capillary endothelial cells, while Notch3 is expressed in the pericytes. Jagged1 is expressed in both capillary endothelial cells and pericytes. After implantation, Notch1, Notch4 and Dll4 are expressed in endothelial cells of newly formed decidual capillaries. Jagged1 is expressed in endothelial cells of spiral arteries and a subset of decidual pericytes. Notch proteins are not expressed in lymphatic vessels or macrophages in the peri-implantation uterus.

Conclusions

We show Notch activity and distinct expression patterns for Notch proteins and ligands, suggesting unique roles for Notch1, Notch4, Dll4, and Jag1 during decidual angiogenesis and early placentation. These data set the stage for loss-of-function and gain-of-function studies that will determine the cell-type specific requirements for Notch proteins in decidual angiogenesis and placentation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13221-015-0034-y) contains supplementary material, which is available to authorized users.