DC-sign+ CD163+ macrophages expressing hyaluronan receptor LYVE-1 are located within chorion villi of the placenta

Placental and Immune Cell DNA Methylation Reference Panel for Bulk Tissue Cell Composition Estimation in Epidemiological Studies

To distinguish DNA methylation (DNAm) from cell proportion changes in whole placental tissue research, we developed a robust cell type-specific DNAm reference to estimate cell composition. We collated newly collected and existing cell type DNAm profiles quantified via Illumina EPIC or 450k microarrays. To estimate cell composition, we deconvoluted whole placental samples (n=36) with robust partial correlation based on the top 50 hyper- and hypomethylated sites per cell type. To test deconvolution performance, we evaluated RMSE in predicting principal component one of DNAm variation in 204 external placental samples. We analyzed DNAm profiles (n=368,435 sites) from 12 cell types: cytotrophoblasts (n=18), endothelial cells (n=19), Hofbauer cells (n=26), stromal cells (n=21), syncytiotrophoblasts (n=4), six lymphocyte types (n=36), and nucleated red blood cells (n=11). Median cell composition was consistent with placental biology: 60.4% syncytiotrophoblast, 17.1% stromal, 8.8% endothelial, 4.5% cytotrophoblast, 3.9% Hofbauer, 1.7% nucleated red blood cells, and 1.2% neutrophils. Our expanded reference outperformed an existing reference in predicting DNAm variation (15.4% variance explained, IQR=21.61) with cell composition estimates (RMSE:10.51 vs. 11.43, p-value<0.001). This cell type reference can robustly estimate cell composition from whole placental DNAm data to detect important cell types, reveal biological mechanisms, and improve casual inference.

The interplay of inflammation and placenta in maternal diabetes: insights into Hofbauer cell expression patterns

Introduction

Inflammation of the placenta is harmful to both the fetus and the mother. Inflammation is strongly associated with diabetes, a common complication of pregnancy. Hofbauer cells (HBCs), unique immune system cells of fetal origin in the placenta, play complex roles, including growth of placental villi and their branching, stromal remodelling, and angiogenesis.

Methods

Our study investigated the expression of IL-1β, IL-10, CYP2C8, CYP2C9, CYP2J2 and sEH in HBCs from patients with type 1 diabetes mellitus (T1DM) and gestational diabetes mellitus (GDM) compared to healthy controls using immunohistochemistry. We also assessed the structure of the villus stroma using Masson´s trichrome.

Results

In T1DM, HBCs showed inflammatory activation characterised by increased IL-1β and decreased CYP epoxygenase expression compared to normal placentas. Conversely, significant inflammation in HBCs appeared less likely in GDM, as levels of IL-1β and CYP epoxygenases remained stable compared to normal placentas. However, GDM showed a significant increase in sEH expression. Both types of diabetes showed delayed placental villous maturation and hypovascularisation, with GDM showing a more pronounced effect.

Conclusion

The expression profiles of IL-1β, CYP epoxygenases and sEH significantlly differ between controls and diabetic placentas and between T1DM and GDM. These facts suggest an association of the CYP epoxygenase-EETs-sEH axis with IL-1β expression as well as villous stromal hypovascularisation. Given the stable high expression of IL-10 in both controls and both types of diabetes, it appears that immune tolerance is maintained in HBCs.

Macrophage deficiency in CSF1R-knockout rat embryos does not compromise placental or embryo development

Macrophages are an abundant cell population in the placenta and developing embryo and appear to be involved in processes of vascularization, morphogenesis, organogenesis, and hematopoiesis. The proliferation, differentiation, and survival are dependent on signals from the macrophage colony-stimulating factor receptor, CSF1R. Aside from the role in macrophages, Csf1r mRNA is highly expressed in placental trophoblasts. To explore the function of macrophages and Csf1r in placental and embryonic development, we analyzed the impact of homozygous Csf1r null mutation (Csf1rko) in the rat. In late gestation, IBA1+ macrophages were abundant in control embryos in all tissues, including the placenta, and greatly reduced in the Csf1rko. CSF1R was also detected in stellate macrophage-like cells and in neurons using anti-CSF1R antibody but was undetectable in trophoblasts. However, the neuronal signal was not abolished in the Csf1rko. CD163 was most abundant in cells forming the center of erythroblastic islands in the liver and was also CSF1R dependent. Despite the substantial reduction in macrophage numbers, we detected no effect of the Csf1rko on development of the placenta or any organs, the relative abundance of vascular elements (CD31 staining), or cell proliferation (Ki67 staining). The loss of CD163+ erythroblastic island macrophages in the liver was not associated with anemia or any reduction in the proliferative activity in the liver, but there was a premature expansion of CD206+ cells, presumptive precursors of liver sinusoidal endothelial cells. We suggest that many functions of macrophages in development of the placenta and embryo can be provided by other cell types in their absence.

Interactions between Macrophages and Mast Cells in the Female Reproductive System

Mast cells (MCs) and macrophages (Mϕs) are innate immune cells that differentiate from early common myeloid precursors and reside in all body tissues. MCs have a unique capacity to neutralize/degrade toxic proteins, and they are hypothesized as being able to adopt two alternative polarization profiles, similar to Mϕs, with distinct or even opposite roles. Mϕs are very plastic phagocytic cells that are devoted to the elimination of senescent/anomalous endogenous entities (to maintain tissue homeostasis), and to the recognition and elimination of exogenous threats. They can adopt several functional phenotypes in response to microenvironmental cues, whose extreme profiles are the inflammatory/killing phenotype (M1) and the anti-inflammatory/healing phenotype (M2). The concomitant and abundant presence of these two cell types and the partial overlap of their defensive and homeostatic functions leads to the hypothesis that their crosstalk is necessary for the optimal coordination of their functions, both under physiological and pathological conditions. This review will examine the relationship between MCs and Mϕs in some situations of homeostatic regulation (menstrual cycle, embryo implantation), and in some inflammatory conditions in the same organs (endometriosis, preeclampsia), in order to appreciate the importance of their cross-regulation.

Automated Quantitative Image Evaluation of Antigen Retrieval Methods for 17 Antibodies in Placentation and Implantation Diagnostic and Research

Immunostaining in clinical routine and research highly depends on standardized staining methods and quantitative image analyses. We qualitatively and quantitatively compared antigen retrieval methods (no pretreatment, pretreatment with pepsin, and heat-induced pretreatment with pH 6 or pH 9) for 17 antibodies relevant for placenta and implantation diagnostics and research. Using our newly established, comprehensive automated quantitative image analysis approach, fluorescent signal intensities were evaluated. Automated quantitative image analysis found that 9 out of 17 antibodies needed antigen retrieval to show positive staining. Heat induction proved to be the most efficient form of antigen retrieval. Eight markers stained positive after pepsin digestion, with β-hCG and vWF showing enhanced staining intensities. To avoid the misinterpretation of quantitative image data, the qualitative aspect should always be considered. Results from native placental tissue were compared with sections of a placental invasion model based on thermo-sensitive scaffolds. Immunostaining on placentas in vitro leads to new insights into fetal development and maternal pathophysiological pathways, as pregnant women are justifiably excluded from clinical studies. Thus, there is a clear need for the assessment of reliable immunofluorescent staining and pretreatment methods. Our evaluation offers a powerful tool for antibody and pretreatment selection in placental research providing objective and precise results.

Phenotypic and functional characterization of first-trimester human placental macrophages, Hofbauer cells

Hofbauer cells (HBCs) are a population of macrophages found in high abundance within the stroma of the first-trimester human placenta. HBCs are the only fetal immune cell population within the stroma of healthy placenta. However, the functional properties of these cells are poorly described. Aligning with their predicted origin via primitive hematopoiesis, we find that HBCs are transcriptionally similar to yolk sac macrophages. Phenotypically, HBCs can be identified as HLA-DR-FOLR2+ macrophages. We identify a number of factors that HBCs secrete (including OPN and MMP-9) that could affect placental angiogenesis and remodeling. We determine that HBCs have the capacity to play a defensive role, where they are responsive to Toll-like receptor stimulation and are microbicidal. Finally, we also identify a population of placenta-associated maternal macrophages (PAMM1a) that adhere to the placental surface and express factors, such as fibronectin, that may aid in repair.

Absorption, distribution, metabolism and excretion of hyaluronic acid during pregnancy: a matter of molecular weight

INTRODUCTION

For many years hyaluronic acid (HA) was mainly used for its hydrating properties. However, new applications have recently arisen, considering the biological properties of HA and its molecular weight. Clinical application of low molecular weight HA (LMW-HA) initially was supported by specific absorption data. The identification of high molecular weight HA (HMW-HA) absorption pathways and the knowledge of its physiological role allowed to evaluate its clinical application. Based on the immunomodulatory properties of HMW-HA and its physiological involvement as signaling molecule, pregnancy represents an interesting context of application.

AREA COVERED

This expert opinion includes in-vitro, in-vivo, ex-vivo and clinical studies on gestational models. It provides an overview of the physiological and the therapeutic role of HMW-HA in pregnancy starting from its metabolism. Indeed, HMW-HA is widely involved in several physiological processes as implantation, immune response, uterine quiescence and cervical remodeling, and therefore is an essential molecule for a successful pregnancy.

EXPERT OPINION

Available evidence suggests that HMW-HA administration can support physiological pregnancy, favoring blastocyst adhesion and development, preventing miscarriage and pre-term birth. For this reason, supplementation in pregnancy should be evaluated.

The anti-inflammatory role of placental Hofbauer cells is altered in patients with chorioamnionitis: Are CYP2C8 and soluble epoxide hydrolase involved in immunomodulation?

AIMS

Hofbauer cells (HBCs) are placental macrophages playing various roles during normal and complicated pregnancies, and of the latter, chorioamnionitis is the most frequent.

METHODS

In placenta with chorioamnionitis, we examined immunohistochemical expression profiles of IL-1β, IL-10, and their potential regulators, CYP2C8 and soluble epoxide hydrolase (sEH), in Hofbauer cells and compared the results with our previously published data for normal placenta.

RESULTS

We found that the expression profiles of the studied proteins in Hofbauer cells in chorioamnionitis differs from normal placenta. In chorioamnionitis, HBCs showed a moderate expression of IL-1β together with a weak expression of IL-10 and CYP2C8. Contrary to normal placenta, HBCs in chorioamnionitis express sEH. We demonstrated a moderate positive correlation between the expression of CYP2C8 and sEH in chorioamnionitis (Spearman r = 0.5654), suggesting enhanced degradation of anti-inflammatory epoxyeicosatrienoic acids. Moreover, the relations of IL-1β and IL-10 to CYP2C8, previously described in normal placenta, disappeared. Furthermore, a weak expression of anti-inflammatory IL-10 in chorioamnionitis was accompanied by change in circularity of HBCs (Spearman r = 0.8193).

CONCLUSION

Taken together, these findings suggest a possible alteration of the anti-inflammatory role of HBCs and its regulation in chorioamnionitis.

Single-cell RNA sequencing reveals the induction of novel myeloid and myeloid-associated cell populations in visceral fat with long-term obesity

Macrophages and other immune cells are important contributors to obesity-associated inflammation; however, the cellular identities of these specific populations remain unknown. In this study, we identified individual populations of myeloid cells found in mouse epididymal/visceral adipose tissue by single-cell RNA sequencing, immunofluorescence, and flow cytometry. Multiple canonical correlation analysis identified 11 unique myeloid and myeloid-associate cell populations. In obese mice, we detected an increased percentage of monocyte-derived pro-inflammatory cells expressing Cd9 and Trem2, as well as significantly decreased percentages of multiple cell populations, including tissue-resident cells expressing Lyve1, Mafb, and Mrc1. We have identified and validated a novel myeloid/macrophage population defined by Ly6a expression, exhibiting both myeloid and mesenchymal characteristics, which increased with obesity and showed high pro-fibrotic characteristics in vitro. Our mouse adipose tissue myeloid cell atlas provides an important resource to investigate obesity-associated inflammation and fibrosis.

M1 macrophages involved in the pathogenesis of placental chronic villitis of unknown etiology

INTRODUCTION

Placental villitis is characterized by the presence of inflammatory infiltrate in the placental villous. The objective of this study was to characterize in villitis of unknown etiology (VUE) of the human placentas the subpopulation of M1, important effector cells, and M2 macrophages, immunoregulatory cells.

METHODS

Sixteen cases of VUE and three control placentas were examined using immunohistochemistry with antibodies for CD3, CD68, CD11c, and CD163.

RESULTS

CD11c appeared predominantly in the inflamed villi when compared to the normal areas (p<.001). These cells corresponded to 41.2% of the macrophage population in the inflamed area and were mainly present inside the villi (36%). With regards to CD163, these cells tended to be in higher amounts in the inflamed villi when compared to CD11c and normal areas.

DISCUSSION

We conclude that the almost exclusive presence of M1 macrophages in the inflamed areas suggests the influence of these cells in the pathogenesis VUE. The greater amount of M2 in villitis and normal areas suggests a possible immunoregulatory mechanism of the inflammatory process in VUE.

Morphometric analysis of Hofbauer cells in normal placenta and chorioamnionitis in humans

Hofbauer cells are macrophages residing in the stroma of placental villi and play a number of roles during normal pregnancy, as well as pathological conditions. A morphometric analysis of Hofbauer cells, in particular to investigate the number of cells, their size and shape in samples of normal human placenta from 1st trimester, term and with chorioamnionitis was performed. Tissue samples were immunostained for CD206 antigen and evaluated using ImageJ software. We detected significant changes in number and morphology of HBCs between normal placenta and placenta with chorioamnionitis samples. In chorioamnionitis, the cells were unevenly distributed within the villi, generally present in higher numbers, larger and more elongated than those in normal 1st trimester and term placenta.

Immune cells in normal pregnancy and gestational trophoblastic diseases

A healthy pregnancy requires the development of maternal-fetal immune tolerance against the semi-allogeneic fetus. The interactions between the trophoblastic cells and the maternal immune cells (p.e., natural killer cells, T cells, macrophages, dendritic cells and B-cells) are important for the development of the maternal-fetal immune tolerance and the placental growth and function. These interactions are mediated by cell to cell contact and secreted molecules such as cytokines, chemokines, angiogenic factors and growth factors. The maternal immune cells are present in normal non-pregnant and pregnant endometrium and there are several lines of evidence based on immunohistochemical and RNA sequencing data that the decidual immune cells and immune-related pathways display alterations in GTD, which may have pathogenetic and clinical significance. The present review focuses on the usefulness of the immunohistochemical analysis which provides multiparametric in situ information regarding the numbers, the immunophenotypes and the immunotopographical distributions of the decidual immune cells in tissue sections from normal pregnancy and GTD. We also discuss the significance of the immunohistochemical information in order to gain insight in the putative mechanisms explaining the alterations of the decidual immune cells in GTD and the potential implications of these alterations in the pathogenesis and the clinical behavior of GTD.

Placental Hofbauer Cell Polarization Resists Inflammatory Cues In Vitro

Feto-placental Hofbauer cells (HBCs) are macrophages residing in placental stroma. They are generally described as anti-inflammatory M2 polarized cells, promoting tolerance and tissue remodeling. In certain pathologies, however, a possible phenotypical switch towards pro-inflammatory M1 macrophages has been proposed. The study aimed to determine if HBCs can acquire an M1 phenotype under pro-inflammatory conditions in vitro. HBCs were isolated from healthy human term placentas. Cells were cultivated upon addition of LPS and INF-γ or IL-4 and IL-13 to induce the M1 and M2 phenotype, respectively. Specific cell polarization markers and cytokines, associated with respective phenotypes, were investigated by flow cytometry and ELISA. THP-1 macrophages served as positive control. Pro-inflammatory stimuli reduced M2 markers CD163 and DC-SIGN, but did not induce M1 markers. TNF-α release was increased, but at the same time TGF-β and IL-10 release was upregulated, resembling in part the M2b sub-phenotype. Anti-inflammatory stimuli had no effect on HBC polarization. HBCs maintain their M2 phenotype in vitro despite inflammatory stimuli, which might represent a state of adaption and tolerance to avoid rejection of the semiallogeneic feto-placental unit.

Perinatal Mesenchymal Stromal Cells and Their Possible Contribution to Fetal-Maternal Tolerance

During pregnancy, a successful coexistence between the mother and the semi-allogenic fetus occurs which requires a dynamic immune system to guarantee an efficient immune protection against possible infections and tolerance toward fetal antigens. The mechanism of fetal-maternal tolerance is still an open question. There is growing in vitro and in vivo evidence that mesenchymal stromal cells (MSC) which are present in perinatal tissues have a prominent role in generating a functional microenvironment critical to a successful pregnancy. This review highlights the immunomodulatory properties of perinatal MSC and their impact on the major immune cell subsets present in the uterus during pregnancy, such as natural killer cells, antigen-presenting cells (macrophages and dendritic cells), and T cells. Here, we discuss the current understanding and the possible contribution of perinatal MSC in the establishment of fetal-maternal tolerance, providing a new perspective on the physiology of gestation.

Macrophage Polarization in Physiological and Pathological Pregnancy

The immunology of pregnancy is complex and poorly defined. During the complex process of pregnancy, macrophages secrete many cytokines/chemokines and play pivotal roles in the maintenance of maternal-fetal tolerance. Here, we summarized the current knowledge of macrophage polarization and the mechanisms involved in physiological or pathological pregnancy processes, including miscarriage, preeclampsia, and preterm birth. Although current evidence provides a compelling argument that macrophages are important in pregnancy, our understanding of the roles and mechanisms of macrophages in pregnancy is still rudimentary. Since macrophages exhibit functional plasticity, they may be ideal targets for therapeutic manipulation during pathological pregnancy. Additional studies are needed to better define the functions and mechanisms of various macrophage subsets in both normal and pathological pregnancy.

Hofbauer Cells: Their Role in Healthy and Complicated Pregnancy

Hofbauer cells are placental villous macrophages of fetal origin that are present throughout pregnancy. Although Hofbauer cell populations are antigenically and morphologically heterogeneous, their epigenetic, antigenic, and functional profiles most closely resemble alternatively activated macrophages or what are referred to as M2a, M2b, M2c, and M2d polarity subtypes. Consistent with an M2-like profile, these cells play an important role in placental development including vasculogenesis and angiogenesis. During placental inflammation Hofbauer cells may produce pro-inflammatory cytokines or mediators that damage the villous cell barrier, and induce fibrotic responses within the villi as a continuum of chronic inflammation. However, to date, there is no evidence that Hofbauer cells become classically activated or adopt an M1 polarity phenotype that is able to kill microbes. To the contrary, their predominant M2 like qualities may be why these cells are ineffective in controlling most TORCH infections. Moreover, Hofbauer cells may contribute to vertical transmission of various pathogens to the fetus since they can harbor live virus and serve as reservoirs within the placenta. The goal of this review is to summarize what is currently known about the role of Hofbauer cells in normal and complicated pregnancies that involve immunologic disorders, inflammation, and/or infection.

Congenital Viral Infection: Traversing the Uterine-Placental Interface

Why certain viruses cross the physical barrier of the human placenta but others do not is incompletely understood. Over the past 20 years, we have gained deeper knowledge of intrauterine infection and routes of viral transmission. This review focuses on human viruses that replicate in the placenta, infect the fetus, and cause birth defects, including rubella virus, varicella-zoster virus, parvovirus B19, human cytomegalovirus (CMV), Zika virus (ZIKV), and hepatitis E virus type 1. Detailed discussions include ( a) the architecture of the uterine-placental interface, ( b) studies of placental explants ex vivo that provide insights into the infection and spread of CMV and ZIKV to the fetal compartment and how these viruses undermine early development, and ( c) novel treatments and vaccines that limit viral replication and have the potential to reduce dissemination, vertical transmission and the occurrence of congenital disease.

DC-SIGN expression in Hofbauer cells may play an important role in immune tolerance in fetal chorionic villi during the development of preeclampsia

Immune tolerance at feto-maternal interfaces is a complex phenomenon. Although maternal decidual macrophages are well-known immune cells, little is known about fetal-derived macrophages (Hofbauer cells) within chorionic villi. Preeclampsia (PE) is a major cause of maternal mortality in the field of obstetrics, and the innate immunological role of maternal decidual macrophages is well known. In this study, we assessed the differential phenotypes and marker expression in fetal macrophages, known as dendritic cell-specific ICAM-grabbing non-integrin (DC-SIGN)-positive Hofbauer cells. We compared Hofbauer cell properties between normal and PE placenta chorionic villi and performed sequential staining of DC-SIGN, CD14, and CD68 to evaluate the existence of Hofbauer cells. Furthermore, to evaluate the immunological function of these cells, we stained the cells for CD163, a marker of immunoregulatory type 2 (M2) macrophages. Additionally, we examined the expression of the immunosuppressive cytokine interleukin (IL)-10, which is known to be produced by M2 macrophages. DC-SIGN+/CD14+, DC-SIGN+/CD68+, and CD163+/DC-SIGN+ cells were quantified based on photomicrographs. The results showed that CD14, CD163, DC-SIGN, and IL-10 levels were significantly downregulated in PE compared with normal. Additionally, CD163+/DC-SIGN+ Hofbauer cells were significantly less frequent in PE than in normal. DC-SIGN Hofbauer cells produced IL-10 at lower levels in the PE than in the normal. Thus, we speculate that fetal-derived Hofbauer cells may play an important role in normal pregnancy with immunosuppressive effects based on their M2 macrophage characteristics to maintain immune tolerance during pregnancy. Additionally, in PE, these functions were defective, supporting the roles of these macrophages in PE development.

Differential immunophenotype of macrophages in acute and chronic chorioamnionitis

AIM

The aim of this study was to investigate the involvement and immunophenotype of macrophages in acute chorioamnionitis (ACA) and chronic chorioamnionitis (CCA), marking amniotic fluid infection and anti-fetal rejection, respectively.

METHODS

Chorioamniotic membranes from (1) gestational age-matched cases without chorioamnionitis, (2) cases with ACA, and (3) cases with CCA were studied after immunohistochemical staining using antibodies against CD14, CD68, CD163, and DC-SIGN.

RESULTS

Macrophages increased prominently in the chorionic trophoblastic layer of both ACA and CCA cases in contrast to non-inflammatory cases. Macrophages in the decidua and the chorioamniotic membranes of ACA cases expressed CD14. Macrophages in the chorionic trophoblastic layer of CCA cases were characterized by CD68 positivity. DC-SIGN-positive cells were increased in the chorioamniotic mesodermal layer of CCA cases.

CONCLUSIONS

Macrophages participate in the inflammatory response in ACA and CCA. The differential immunophenotypes of macrophages in the decidua and chorioamniotic membranes of ACA and CCA cases suggest their disease-specific and region-specific roles at the feto-maternal interface.

Modulators of the Balance between M1 and M2 Macrophages during Pregnancy

Macrophages are a subset of mononuclear phagocytes of the innate immune system with high plasticity and heterogeneity. At the maternal–fetal interface, macrophages are present in all stages of pregnancy and involved in a variety of activities, including regulation of immune cell activities, decidualization, placental cell invasion, angiogenesis, parturition, and postpartum uterine involution. The activation state and function of uterine–placental macrophages are largely dependent on the local tissue microenvironment. However, disruption of the uterine microenvironment can have profound effects on macrophage activity and subsequently impact pregnancy outcome. Thus, appropriately and timely regulated macrophage polarization has been considered a key determinant of successful pregnancy. Targeting macrophage polarization might be an efficient strategy for maintaining maternal–fetal immune homeostasis and a normal pregnancy. Here, we will review the latest findings regarding the modulators regulating macrophage polarization in healthy pregnancies and pregnancy complications, which might provide a basis for macrophage-centered therapeutic strategies.

Hofbauer Cells: Placental Macrophages of Fetal Origin

Pregnancy complications such as preterm birth, miscarriage, maternal and/or neonatal morbidities, and mortality can be manifestations of underlying placental pathology. Hofbauer cells refer to a heterogeneous population of fetal macrophages that reside within the functional unit of the placenta known as the chorionic villus. Hofbauer cells can be detected within the connective tissue matrix of the placenta as early as 4 weeks post-conception and are present throughout pregnancy. These cells are implicated in a wide array of functions important for a successful pregnancy including placental morphogenesis, immune regulation, control of stromal water content, and the transfer of ions and serum proteins across the maternal-fetal barrier. Derangements in Hofbauer cell homeostasis are associated with placental pathologies involving infection, inflammation, and inadequate placental development. Despite a growing body of evidence that these cells are important, our knowledge about Hofbauer cell function in both normal and dysfunctional pregnancy is rudimentary. The goal of this chapter is to provide an overview of what is known about Hofbauer cell origins and their potential roles in normal and complicated pregnancy. We also review established and emerging methodologies available for the study of Hofbauer cells during in vitro and in vivo conditions.

Immunolocalization of substance P and NK-1 receptor in vascular anomalies

The peptide substance P (SP) shows a widespread distribution in both the central and peripheral nervous systems, but it is also ubiquitous in the human body. After binding to the neurokinin-1 (NK-1) receptor, SP regulates tumoral angiogenesis and proliferation. Thus, knowledge of this system is the key for a better understanding and, hence, a better management of many human diseases, including vascular anomalies (VA). This study aims to examine the expression and localization of both SP and the NK-1 receptor in different vascular anomalies using an immunohistochemical technique. Our results demonstrated predominantly nuclear localization of SP in venous malformations and in one haemangioma sample, in contrast with cytoplasmic expression in capillary malformations and rapidly involuting congenital hemangioma (RICH). NK-1 receptor showed a cytoplasmic localization in all VA. In summary, all these findings demonstrate that SP and NK-1 receptor are expressed in VA, with different expression patterns depending on the nature of the anomaly, suggesting that they could play an important role in the pathogenesis of VA.

Hofbauer cells of M2a, M2b and M2c polarization may regulate feto-placental angiogenesis

The human placenta comprises a special type of tissue macrophages, the Hofbauer cells (HBC), which exhibit M2 macrophage phenotype. Several subtypes of M2-polarized macrophages (M2a, M2b and M2c) exist in almost all tissues. Macrophage polarization depends on the way of macrophage activation and leads to the expression of specific cell surface markers and the acquisition of specific functions, including tissue remodeling and the promotion of angiogenesis. The placenta is a highly vascularized and rapidly growing organ, suggesting a role of HBC in feto-placental angiogenesis. We here aimed to characterize the specific polarization and phenotype of HBC and investigated the role of HBC in feto-placental angiogenesis. Therefore, HBC were isolated from third trimester placentas and their phenotype was determined by the presence of cell surface markers (FACS analysis) and secretion of cytokines (ELISA). HBC conditioned medium (CM) was analyzed for pro-angiogenic factors, and the effect of HBC CM on angiogenesis, proliferation and chemoattraction of isolated primary feto-placental endothelial cells (fpEC) was determined in vitro. Our results revealed that isolated HBC possess an M2 polarization, with M2a, M2b and M2c characteristics. HBC secreted the pro-angiogenic molecules VEGF and FGF2. Furthermore, HBC CM stimulated the in vitro angiogenesis of fpEC. However, compared with control medium, chemoattraction of fpEC toward HBC CM was reduced. Proliferation of fpEC was not affected by HBC CM. These findings demonstrate a paracrine regulation of feto-placental angiogenesis by HBC in vitro. Based on our collective results, we propose that the changes in HBC number or phenotype may affect feto-placental angiogenesis.

Lymphatic vascular endothelial hyaluronan receptor-1 immunoexpression in placenta of HIV infected pre-eclamptic women

INTRODUCTION

Lymphangiogenesis is the formation of new vessels from pre-existing lymphatic vessels. Data on lymphangiogenesis in the placenta of HIV-infected pre-eclamptics are sparse and the findings are conflicting. The aim of this novel study was to evaluate LYVE-1 immunoexpression in the placenta of HIV infected normotensive versus pre-eclamptic women.

METHODS

Placental tissue was obtained from normotensive and pre-eclamptic women stratified according to their HIV status. The pre-eclamptic group was divided into early (<34 weeks) and late (>34 weeks) onset. Immunohistochemistry utilized mouse anti-human LYVE-1 antibody and was morphometrically evaluated.

RESULTS

LYVE-1 immunostaining was localized within endothelium of the arterial supply and venous drainage of both conducting and exchange villi as well as within medial cells of arteries. LYVE-1 immunostained macrophage-like cells were observed within the fetal and maternal circulation. LYVE-1 immunoexpression was higher (p=0.0001) in HIV positive cohort, regardless of pregnancy and villous type. Irrespective of HIV status and pregnancy type, LYVE-1 immunoexpression was significantly elevated in the conducting compared to the exchange villi (p=0.01). LYVE-1 immunoexpression was higher in N and LOPE compared to EOPE groups for both conducting and exchange villi types respectively (p=0.0001 and p=0.006). There is a decrease of LYVE-1 expression in EOPE+ (conducting villi) and EOPE- (exchange villi) compared to N and LOPE subgroups.

CONCLUSION

This study provides a novel insight into an up-regulation of LYVE-1 expression in the fetal circulation of conducting and exchange villi of HIV-infected pre-eclamptics.

The Role of Decidual Macrophages During Normal and Pathological Pregnancy

Macrophages perform many specific functions including host defense, homeostasis, angiogenesis, and tissue development. Macrophages are the second most abundant leukocyte population in the non-pregnant endometrium and pregnant decidua and likely play a central role in the establishment and maintenance of normal pregnancy. Importantly, aberrantly activated uterine macrophages can affect trophoblast function and placental development, which may result in various adverse pregnancy outcomes ranging from pre-eclampsia to fetal growth restriction or demise. Only by fully understanding the roles of macrophage in pregnancy will we be able to develop interventions for the treatment of these various pregnancy complications. This review discusses the general origin and classification of monocytes and macrophages and focuses on the phenotype and functional roles of decidual macrophage at the maternal-fetal interface in normal pregnancy, as well as discussing the potential contribution of the abnormal state of these cells to various aspects of pregnancy pathologies.

Development of Blood and Lymphatic Endothelial Cells in Embryonic and Fetal Human Skin

Blood and lymphatic vessels provide nutrients for the skin and fulfill important homeostatic functions, such as the regulation of immunologic processes. In this study, we investigated the development of blood and lymphatic endothelial cells in prenatal human skin in situ using multicolor immunofluorescence and analyzed angiogenic molecules by protein arrays of lysates and cell culture supernatants. We found that at 8 to 10 weeks of estimated gestational age, CD144(+) vessels predominantly express the venous endothelial cell marker PAL-E, whereas CD144(+)PAL-E(-) vessels compatible with arteries only appear at the end of the first trimester. Lymphatic progenitor cells at 8 weeks of estimated gestational age express CD31, CD144, Prox1, and temporary PAL-E. At that developmental stage not all lymphatic progenitor cells express podoplanin or Lyve-1, which are acquired with advancing gestational age in a stepwise fashion. Already in second-trimester human skin, the phenotype of blood and lymphatic vessels roughly resembles the one in adult skin. The expression pattern of angiogenic molecules in lysates and cell culture supernatants of prenatal skin did not reveal the expected bent to proangiogenic molecules, indicating a complex regulation of angiogenesis during ontogeny. In summary, this study provides enticing new insights into the development and phenotypic characteristics of the vascular system in human prenatal skin.

Generation of pure lymphatic endothelial cells from human pluripotent stem cells and their therapeutic effects on wound repair

Human pluripotent stem cells (hPSCs) have emerged as an important source for cell therapy. However, to date, no studies demonstrated generation of purified hPSC-derived lymphatic endothelial cells (LECs) and tested their therapeutic potential in disease models. Here we sought to differentiate hPSCs into the LEC lineage, purify them with LEC markers, and evaluate their therapeutic effects. We found that an OP9-assisted culture system reinforced by addition of VEGF-A, VEGF-C, and EGF most efficiently generated LECs, which were then isolated via FACS-sorting with LYVE-1 and PODOPLANIN. These hPSC-derived LYVE-1⁺PODOPLANIN⁺cells showed a pure committed LEC phenotype, formed new lymphatic vessels, and expressed lymphangiogenic factors at high levels. These hPSC-derived LECs enhanced wound healing through lymphangiogenesis and lymphvasculogenesis. Here we report, for the first time, that LECs can be selectively isolated from differentiating hPSCs, and that these cells are potent for lymphatic vessel formation in vivo and wound healing. This system and the purified hPSC-derived LECs can serve as a new platform for studying LEC development as well as for cell therapy.

M1/M2 macrophage polarity in normal and complicated pregnancy

Tissue macrophages play an important role in all stages of pregnancy, including uterine stromal remodeling (decidualization) before embryo implantation, parturition, and post-partum uterine involution. The activation state and function of utero-placental macrophages are largely dependent on the local tissue microenvironment. Thus, macrophages are involved in a variety of activities such as regulation of immune cell activities, placental cell invasion, angiogenesis, and tissue remodeling. Disruption of the uterine microenvironment, particularly during the early stages of pregnancy (decidualization, implantation, and placentation) can have profound effects on macrophage activity and subsequently impact pregnancy outcome. In this review, we will provide an overview of the temporal and spatial regulation of utero-placental macrophage activation during normal pregnancy in human beings and rodents with a focus on more recent findings. We will also discuss the role of M1/M2 dysregulation within the intrauterine environment during adverse pregnancy outcomes.

Three types of macrophagic cells in the mesentery of mice with special reference to LYVE-1-immunoreactive cells

Immunohistochemistry using whole mount preparations of the murine mesentery revealed two types of LYVE-1-immunoreactive cells with dendritic morphology other than F4/80(+) typical macrophages.The two types of LYVE-1(+) cells were regularly distributed with constant intervals throughout the mesentery and appeared to possess their own territory. Both types of LYVE-1(+) cells were weakly or moderately immunopositive for F4/80 antibody, a marker of macrophages,while F4/80(+) round macrophages were absolutely free from the LYVE-1 immunoreactivity. Only macrophages could ingest latex particles of 20 nm in diameter 3 h after a peritoneal injection.Peritoneal administration of lipopolysaccharide (LPS) induced a rapid reduction of LYVE-1 immunoreactivity in the cells with dendritic morphology followed by an increased immunoreactivity to F4/80 antibody, and simultaneously by dynamic changes in their shape. Under normal conditions,F4/80(+) macrophages in various connective tissues expressed LYVE-1, in contrast to lack of LYVE-1 in F4/80(+) macrophages within the parenchyma of visceral organs and macrophages residing in hepatic sinusoids and pulmonary alveoli. LYVE-1 may play a role in cell adhesion and migration of macrophagic cells within connective tissues rich in hyaluronan, and loss of LYVE-1 becomes a reliable sign of activated conditions in inflammation.

Mapping the distinctive populations of lymphatic endothelial cells in different zones of human lymph nodes

The lymphatic sinuses in human lymph nodes (LNs) are crucial to LN function yet their structure remains poorly defined. Much of our current knowledge of lymphatic sinuses derives from rodent models, however human LNs differ substantially in their sinus structure, most notably due to the presence of trabeculae and trabecular lymphatic sinuses that rodent LNs lack. Lymphatic sinuses are bounded and traversed by lymphatic endothelial cells (LECs). A better understanding of LECs in human LNs is likely to improve our understanding of the regulation of cell trafficking within LNs, now an important therapeutic target, as well as disease processes that involve lymphatic sinuses. We therefore sought to map all the LECs within human LNs using multicolor immunofluorescence microscopy to visualize the distribution of a range of putative markers. PROX1 was the only marker that uniquely identified the LECs lining and traversing all the sinuses in human LNs. In contrast, LYVE1 and STAB2 were only expressed by LECs in the paracortical and medullary sinuses in the vast majority of LNs studied, whilst the subcapsular and trabecular sinuses lacked these molecules. These data highlight the existence of at least two distinctive populations of LECs within human LNs. Of the other LEC markers, we confirmed VEGFR3 was not specific for LECs, and CD144 and CD31 stained both LECs and blood vascular endothelial cells (BECs); in contrast, CD59 and CD105 stained BECs but not LECs. We also showed that antigen-presenting cells (APCs) in the sinuses could be clearly distinguished from LECs by their expression of CD169, and their lack of expression of PROX1 and STAB2, or endothelial markers such as CD144. However, both LECs and sinus APCs were stained with DCN46, an antibody commonly used to detect CD209.

Innate and adaptive immune interactions at the fetal-maternal interface in healthy human pregnancy and pre-eclampsia

Maternal immune tolerance of the fetus is indispensable for a healthy pregnancy outcome. Nowhere is this immune tolerance more important than at the fetal–maternal interface – the decidua, the site of implantation, and placentation. Indeed, many lines of evidence suggest an immunological origin to the common pregnancy-related disorder, pre-eclampsia. Within the innate immune system, decidual NK cells and antigen presenting cells (including dendritic cells and macrophages) make up a large proportion of the decidual leukocyte population, and are thought to modulate vascular remodeling and trophoblast invasion. On the other hand, within the adaptive immune system, Foxp3⁺ regulatory T cells are crucial for ensuring immune tolerance toward the semi-allogeneic fetus. Additionally, another population of CD4⁺HLA-G⁺ suppressor T cells has also been identified as a potential player in the maintenance of immune tolerance. More recently, studies are beginning to unravel the potential interactions between the innate and the adaptive immune system within the decidua, that are required to maintain a healthy pregnancy. In this review, we discuss the recent advances exploring the complex crosstalk between the innate and the adaptive immune system during human pregnancy.

A three-dimensional atlas of human dermal leukocytes, lymphatics, and blood vessels

Dendritic cells (DCs), macrophages (Mφ), and T cells are major components of the skin immune system, but their interstitial spatial organization is poorly characterized. Using four-channel whole-mount immunofluorescence staining of the human dermis, we demonstrated the three-dimensional distribution of CD31⁺ blood capillaries, LYVE-1⁺ lymphatics, discrete populations of CD11c⁺ myeloid DCs, FXIIIa⁺ Mφ, and lymphocytes. We showed phenotypic and morphological differences in situ between DCs and Mφ. DCs formed the first dermal cellular layer (0–20 μm beneath the dermoepidermal junction), Mφ were located deeper (40–60 μm), and CD3⁺ lymphocytes were observed throughout (0–60 μm). Below this level, DCs, T cells, and the majority of Mφ formed stable perivascular sheaths. Whole-mount imaging revealed the true extent of dermal leukocytes previously underestimated from cross-section views. The total area of apical dermis (0–30 μm) contained approximately 10-fold more myeloid DCs than the entire blood volume of an average individual. Surprisingly, <1% of dermal DCs occupied lymphatics in freshly isolated skin. Dermal DCs rapidly accumulated within lymphatics, but Mφ remained fixed in skin explants cultured ex vivo. The leukocyte architecture observed in normal skin was distorted in inflammation and disease. These studies illustrate the micro-anatomy of dermal leukocytes and provide further insights into their functional organization.

Placental macrophages are impaired in chorioamnionitis, an infectious pathology of the placenta

Pregnancy is dependent on maternal-fetal tolerance that may be compromised because of infections or inflammation of the placenta. In this study, we examined whether the context of placental immune tolerance affected the functions of resident macrophages and if their functions were altered during chorioamnionitis, an infectious pathology of the placenta. Macrophages from at-term placentas expressed CD14, exhibited macrophage microbicidal functions, but were less inflammatory than monocyte-derived macrophages. Moreover, placental macrophages spontaneously matured into multinucleated giant cells (MGCs), a property not exhibited by monocyte-derived macrophages, and we detected MGCs of myeloid origin in placental tissue. Compared with placental macrophages, MGCs exhibited a specific phenotype and gene expression signature, consisting of increased cytoskeleton-associated gene expression along with depressed expression of inflammatory response genes. Furthermore, placental macrophages from patients with chorioamnionitis were unable to form MGCs, but this defect was partially corrected by incubating these placental macrophages with control trophoblast supernatants. MGCs formation likely serves to regulate their inflammatory and cytocidal activities in a context that imposes semiallograft acceptance and defense against pathogens.

Immunolocalization of substance P and NK-1 receptor in Hofbauer cells in human normal placenta

Substance P (SP) after binding to the neurokinin-1 (NK-1) receptor regulates many biological functions. Both SP and the NK-1 receptor are expressed in human normal placenta cells, monocytes, and macrophages. However, to our knowledge, the presence of both SP and the NK-1 receptor in macrophages of the placenta, the Hofbauer cells, is unknown. We demonstrate by immunohistochemistry in human normal placenta samples the presence of both SP and NK-1 receptors in the cytoplasm and in the nucleus of Hofbauer cells. The findings suggest a functional role of the SP/NK-1 receptor system in the physiology and pathophysiology of Hofbauer cells in the human placenta.

Characterization of cells expressing lymphatic marker LYVE-1 in macaque large intestine during simian immunodeficiency virus infection identifies a large population of nonvascular LYVE-1(+)/DC-SIGN(+) cells

Abstract LYVE-1 is a marker expressed by lymphatic endothelial cells (LECs) that line the lymphatic endothelium. Through studies designed to examine potential changes in expression of LYVE-1 in cynomolgus macaque colon tissues during the course of simian immunodeficiency virus (SIV) infection, we discovered that LYVE-1 was expressed by heterogenous populations of cells. As revealed by in situ hybridization (ISH), LYVE-1 mRNA levels in colon were decreased in macaques with AIDS compared with acutely infected or uninfected macaques. In the submucosal layer of the colon, approximately half of the LYVE-1-expressing cells co-expressed the dendritic cell (DC) marker, DC-SIGN/CD209, and this percentage did not change appreciably during infection. Subsets of cells expressing LYVE-1 also co-expressed macrophage markers, such as CD68 and the macrophage mannose receptor (MMR)/CD206, in both the colon and lymph nodes. LECs, DCs, and macrophages that co-expressed LYVE-1 were observed in colon and lymph node from uninfected, healthy animals as well as in tissues with SIV-driven inflammation. These findings provide further definition of the phenotypic overlap between LECs and antigen presenting cells, reveal the heterogeneity within the population of cells expressing the lymphatic marker LYVE-1, and show that SIV modulates this population of cells in a mucosal surface across which the virus is acquired.

Plasticity of blood- and lymphatic endothelial cells and marker identification

The distinction between lymphatic and blood vessels is biologically fundamental. Here we wanted to rigorously analyze the universal applicability of vascular markers and characteristics of the two widely used vascular model systems human microvascular endothelial cell line-1 (HMEC-1) and telomerase-immortalized microvascular endothelial cell line (TIME). Therefore we studied the protein expression and functional properties of the endothelial cell lines HMEC-1 and TIME by flow cytometry and in vitro flow assays. We then performed microarray analyses of the gene expression in these two cell lines and compared them to primary endothelial cells. Using bioinformatics we then defined 39 new, more universal, endothelial-type specific markers from 47 primary endothelial microarray datasets and validated them using immunohistochemistry with normal and pathological tissues. We surprisingly found that both HMEC-1 and TIME are hybrid blood- and lymphatic cells. In addition, we discovered great discrepancies in the previous identifications of blood- and lymphatic endothelium-specific genes. Hence we identified and validated new, universally applicable vascular markers. Summarizing, the hybrid blood-lymphatic endothelial phenotype of HMEC-1 and TIME is indicative of plasticity in the gene expression of immortalized endothelial cell lines. Moreover, we identified new, stable, vessel-type specific markers for blood- and lymphatic endothelium, useful for basic research and clinical diagnostics.

Naturally-occurring genetic variants in human DC-SIGN increase HIV-1 capture, cell-transfer and risk of mother-to-child transmission

BACKGROUND

Mother-to-child transmission (MTCT) is the main cause of HIV-1 infection in children worldwide. Dendritic cell-specific ICAM-3 grabbing-nonintegrin (DC-SIGN, also known as CD209) is an HIV-1 receptor that enhances its transmission to T cells and is expressed on placental macrophages.

METHODS AND FINDINGS

We have investigated the association between DC-SIGN genetic variants and risk of MTCT of HIV-1 among Zimbabwean infants and characterized the impact of the associated mutations on DC-SIGN expression and interaction with HIV-1. DC-SIGN promoter (p-336C and p-201A) and exon 4 (198Q and 242V) variants were all significantly associated with increased risk of intrauterine (IU) HIV-1 infection. Promoter variants decreased DC-SIGN expression both in vitro and in placental CD163(+) macrophages (Hofbauer cells) of HIV-1 unexposed infants but not of HIV-1 exposed infants. The exon 4 protein-modifying mutations increased HIV-1 capture and transmission to T cells in vitro.

CONCLUSION

This study provides compelling evidence to support an important role of DC-SIGN in IU HIV-1 infection.

Methylome of fetal and maternal monocytes and macrophages at the feto-maternal interface

PROBLEM

Decidual macrophages (dMφ) of the mother and placental macrophages (Hofbauer cells, HC) of the fetus are deployed at a critical location: the feto-maternal interface. This study was conducted to compare the DNA methylome of maternal and fetal monocytes, dMφ, and HC and thereby to determine the immunobiological importance of DNA methylation in pregnancy.

METHOD OF STUDY

Paired samples were obtained from normal pregnant women at term not in labor and their neonates. Maternal monocytes (MMo) and fetal monocytes (FMo) were isolated from the peripheral blood of mothers and fetal cord blood, respectively. dMφ and HC were obtained from the decidua of fetal membranes and placentas, respectively. DNA methylation profiling was performed using the Illumina Infinium Human Methylation27 BeadChip. Quantitative real-time PCR and Western Blot were performed for validation experiments.

RESULTS

(i) Significant differences in DNA methylation were found in each comparison (MMo versus FMo, 65 loci; dMφ versus HC, 266 loci; MMo versus dMφ, 199 loci; FMo versus HC, 1030 loci). (ii) Many of the immune response-related genes were hypermethylated in fetal cells (FMo and HC) compared to maternal cells (MMo and dMφ). (iii) Genes encoding markers of classical macrophage activation were hypermethylated, and genes encoding alternative macrophage activation were hypomethylated in dMφ and HC compared to MMo and FMo, respectively. (iv) mRNA expressions of DNMT1, DNMT3A, and DNMT3B were significantly lower in dMφ than in HC. (v) 5-azacytidine treatment increased expression of INCA1 in dMφ.

CONCLUSIONS

The findings herein indicate that DNA methylation patterns change during monocyte-macrophage differentiation at the feto-maternal interface. It is also suggested that DNA methylation is an important component of the biological machinery conferring an anti-inflammatory phenotype to macrophages at the feto-maternal interface.

Macrophages at the fetal-maternal interface express markers of alternative activation and are induced by M-CSF and IL-10

During pregnancy, the maternal immune system is challenged by the presence of the fetus, which must be tolerated despite being semiallogeneic. Uterine mucosal (or decidual) macrophages (M), one of the major leukocyte populations at the fetal-maternal interface, have been implicated in fetal tolerance, but information regarding their regulation is scarce. In this study, we investigated the role of several factors potentially involved in the differentiation and polarization of decidual M with an in vitro M differentiation model. By using flow cytometry, we showed that M-CSF and IL-10 were potent inducers of M2 (immunoregulatory) M markers expressed on human decidual M (CD14, CD163, CD206, CD209). In contrast, proinflammatory stimuli, and unexpectedly also the Th2-associated IL-4 and IL-13, induced different patterns of expression, indicating that a Th2-dominated environment is not required for decidual M polarization. M-CSF/IL-10-stimulated and decidual M also showed similar cytokine secretion patterns, with production of IL-10 as well as IL-6, TNF, and CCL4. Conversely, the proinflammatory, LPS/IFN-γ-stimulated M produced significantly higher levels of TNF and no IL-10. We also used a gene array with 420 M-related genes, of which 100 were previously reported to be regulated in a global gene expression profiling of decidual M, confirming that M-CSF/IL-10-induced M are closely related to decidual M. Taken together, our results consistently point to a central role for M-CSF and in particular IL-10 in the shaping of decidual M with regulatory properties. These cytokines may therefore play an important role in supporting the homeostatic and tolerant immune milieu required for a successful pregnancy.

Differential distribution and phenotype of decidual macrophages in preeclamptic versus control pregnancies

Maternal immune tolerance of the semiallogeneic fetus is a complex phenomenon. Macrophages are an abundant cell population in the human decidua, and changes in distribution or phenotype may be involved in the development of preeclampsia. The aim of this study was to assess the distribution and phenotype of macrophages in preterm preeclamptic, preterm control, and term control placentas. Placentas of preterm preeclamptic (n = 6), preterm control (n = 5), and term control pregnancies (n = 6) were sequentially immunohistochemically stained for CD14, CD163, DC SIGN, and IL-10. The distributions of CD14(+), CD163(+), DC SIGN(+), IL-10(+), CD163(+)/CD14(+), DC SIGN(+)/CD14(+), and Flt-1/CD14(+) cells were determined by double staining and by digital image analysis of sequential photomicrographs. CD14 and CD163 expression increased significantly in preterm preeclamptic decidua basalis compared with preterm control pregnancies (P = 0.0006 and P = 0.034, respectively). IL-10 expression was significantly lower in the decidua parietalis of preterm preeclamptic pregnancies compared with preterm control pregnancies (P = 0.03). The CD163/CD14 ratio was significantly lower in the decidua basalis (P = 0.0293) and the DC SIGN/CD14 ratio was significantly higher in the decidua basalis (P < 0.0001) and parietalis (P < 0.0001) of preterm preeclamptic pregnancies compared with preterm control pregnancies. CD14(+) macrophages did express Flt-1. Alterations in distribution and phenotype of macrophages in the decidua of preterm preeclamptic pregnancies compared with control pregnancies may contribute to the pathogenesis of preeclampsia.

Isolation of hofbauer cells from human term placentas with high yield and purity

PROBLEM  Placental villus macrophages (i.e., Hofbauer cells, HBCs) were identified more than 100 years ago. Alterations in their numbers and characteristics are associated with several complications of pregnancy. Although HBCs have previously been isolated and cultured, there is no consensus methodology to obtain these cells with high yield and purity for in vitro studies. METHOD OF STUDY  Hofbauer cells were isolated from human term placentas using protocols in which cytotrophoblasts (CTs) and fibroblasts (FIBs), other major villous cell types, were isolated in parallel. Enzymatic digestion, Percoll gradients, and immunoselection were used to isolate the three cell types. Purity was assessed by morphology, flow cytometry, and phagocytosis assays. RESULTS  Hofbauer cells were isolated with 98-99% purity and a yield of 130-200 × 10(6) cells/80-100 g of tissue. HBCs exhibited a pleiomorphic and vacuolated appearance for at least 5 days in culture medium with and without serum. High levels of phagocytosis in HBCs, but not in CTs or FIBs, confirmed macrophage function in HBCs. Phagocytotic activity was maintained across several days in culture. CONCLUSION  Hofbauer cells were isolated from term placenta with high yield and purity using protocols in which CTs and FIBs were also obtained. This methodology will foster future studies that examine the role of HBCs in regulating villus function.

Placental macrophage (Hofbauer cell) polarization is independent of maternal allergen-sensitization and presence of chorioamnionitis

BACKGROUND

Macrophages can polarize in which M1/classically activated and M2/alternatively activated macrophages are considered to be the extremes. M1 macrophages are involved in inflammatory reactions, while M2 macrophages are suggested to be involved in homeostasis, parasite killing, tumor promotion, tissue remodeling and in allergic reactions. We hypothesized that polarization of placental macrophages (Hofbauer cells) is influenced by the allergen-sensitization status of the mother and/or the presence of chorioamnionitis, a placental inflammation. This Hofbauer cell polarization might be associated to the intrauterine environment and influence the risk of allergy development for the child. Therefore we aimed to determine the polarization status of Hofbauer cells in health and disease.

METHODS

We determined the expression of CD68, CX3CR1, IL-7R, DC-SIGN/CD209 and CD163 in placentas of sensitized versus non-sensitized mothers (n = 17), and placentas with or without histological chorioamnionitis (n = 10) by means of immunohistochemical analysis and quantitative real-time PCR (qPCR).

RESULTS

Protein expression of the M1 markers (CX3CR1, IL-7R and CCR7) could not be detected in any of the analyzed samples while the M2 markers (DC-SIGN, CD163 and mannose receptor/CD206) were readily detected. Significant differences between non-sensitized versus sensitized mothers and uncomplicated versus chorioamnionitis complicated pregnancies were not detected at protein or at mRNA expression level.

CONCLUSIONS

These results suggest that Hofbauer cells have an M2 phenotype, and that their polarization is not affected by maternal allergen-sensitization or by presence of chorioamnionitis.

Hyaluronan as an immune regulator in human diseases

Accumulation and turnover of extracellular matrix components are the hallmarks of tissue injury. Fragmented hyaluronan stimulates the expression of inflammatory genes by a variety of immune cells at the injury site. Hyaluronan binds to a number of cell surface proteins on various cell types. Hyaluronan fragments signal through both Toll-like receptor (TLR) 4 and TLR2 as well as CD44 to stimulate inflammatory genes in inflammatory cells. Hyaluronan is also present on the cell surface of epithelial cells and provides protection against tissue damage from the environment by interacting with TLR2 and TLR4. Hyaluronan and hyaluronan-binding proteins regulate inflammation, tissue injury, and repair through regulating inflammatory cell recruitment, release of inflammatory cytokines, and cell migration. This review focuses on the role of hyaluronan as an immune regulator in human diseases.

Pulmonary dendritic cells in lungs of preterm infants: neglected participants in bronchopulmonary dysplasia?

Preterm infants are at risk for bronchopulmonary dysplasia (BPD), a chronic lung disease characterized by disrupted alveolar remodeling and microvascular dysangiogenesis. The pathogenesis of BPD is multifactorial, with contributions from antenatal and/or postnatal infection and inflammation. The potential role of dendritic cells, critical immune regulatory cells with potent angiogenic activities, remains undetermined. We studied the prevalence and topography of dendritic cells in postmortem lungs of short- and long-term ventilated preterm infants born between 23 and 29 weeks in gestation. Controls were age-matched infants who had lived less than 12 hours. Dendritic cells were identified by anti-DC-SIGN immunohistochemistry and were co-localized with endothelial and smooth muscle cells by double immunofluorescence. Lungs of early and late control infants without evidence of antenatal infection contained scattered DC-SIGN-positive dendritic cells in the peripheral lung parenchyma. Lungs of early control infants with a history of chorioamnionitis/antenatal infection and lungs of short- or long-term ventilated preterm infants showed a dramatic (more than 3-fold) increase in dendritic cells. Double labeling highlighted a close association between dendritic cells and small- or medium-sized pulmonary vessels. In conclusion, we demonstrated that dendritic cells are an integral component of normal postcanalicular lung development. Antenatal infection and ventilation/BPD are associated with significant pulmonary recruitment of dendritic cells. The recently described angiogenic effects of dendritic cells and their intimate association with the pulmonary microvasculature indicate that dendritic cells may participate in BPD-associated dysangiogenesis. Elucidation of the role of this immunovascular axis may lead to novel therapeutic approaches to BPD.

IgE in the human placenta: why there?

Immunoglobulin E (IgE) antibodies are key effector molecules in the allergic inflammatory response and are also involved in the protection against extracellular parasites. Allergic symptoms often develop early in life, and the intrauterine environment has been proposed to play an important role in affecting the risk of later allergy development. The placenta constitutes a selective barrier between the maternal and foetal circulation. Recently, we reported that maternal IgE antibodies are present on foetal macrophages in the villous tissue of the human placenta irrespective of maternal allergy status. This review discusses the presence of IgE antibodies in the human placenta and its possible roles in normal and pathologic pregnancy. It also deals with the relationship between placental IgE and development of allergy during childhood. A better understanding of the role of IgE in placenta could give us clues on how to prevent allergy development in the future generations.