Human Fetal-maternal Interface Research Articles

Interleukin-34 is present at the fetal-maternal interface and induces immunoregulatory macrophages of a decidual phenotype in vitro.

Is the newly discovered cytokine interleukin (IL)-34 expressed at the human fetal-maternal interface in order to influence polarization of monocytes into macrophages of a decidual immunoregulatory phenotype? IL-34 was found to be present at the fetal-maternal interface, in both fetal placenta and maternal decidua, and it was able to polarize monocytes into macrophages of a decidual phenotype. IL-34 was shown to bind to the same receptor as macrophage-colony stimulating factor (M-CSF), which has an important immunomodulatory role at the fetal-maternal interface, for example by polarizing decidual macrophages to an M2-like regulatory phenotype. IL-34 is known to regulate macrophage subsets, such as microglia and Langerhans cells, but its presence at the fetal-maternal interface is unknown. The presence of IL-34 at the fetal-maternal interface was evaluated by immunohistochemistry (IHC) and ELISA in placental and decidual tissues as well as in isolated trophoblast cells and decidual stromal cells obtained from first trimester elective surgical terminations of pregnancy (n = 49). IL-34 expression was also assessed in third trimester placental biopsies from women with (n = 21) or without (n = 15) pre-eclampsia. The effect of IL-34 on macrophage polarization was evaluated in an in vitro model of blood monocytes obtained from healthy volunteers (n = 14). In this model, granulocyte macrophage-colony stimulating factor (GM-CSF) serves as a growth factor for M1-like polarization, and M-CSF as a growth factor for M2-like polarization. First trimester placental and decidual tissues were obtained from elective pregnancy terminations. Placental biopsies were obtained from women with pre-eclampsia and matched controls in the delivery ward. Polarization of macrophages in vitro was determined by flow-cytometric phenotyping and secretion of cytokines and chemokines in cell-free supernatants by multiplex bead assay. Our study shows that IL-34 is produced at the fetal-maternal interface by both placental cyto- and syncytiotrophoblasts and decidual stromal cells. We also show that IL-34, in vitro, is able to polarize blood monocytes into macrophages with a phenotype (CD14highCD163+CD209+) and cytokine secretion pattern similar to that of decidual macrophages. The IL-34-induced phenotype was similar, but not identical to the phenotype induced by M-CSF, and both IL-34- and M-CSF-induced macrophages were significantly different (P < 0.05-0.0001 depending on marker) from GM-CSF-polarized M1-like macrophages. Our findings suggest that IL-34 is involved in the establishment of the tolerant milieu found at the fetal-maternal interface by skewing polarization of macrophages into a regulatory phenotype. Although it is clear that IL-34 is present at the fetal-maternal interface and polarizes macrophages in vitro, its precise role in vivo remains to be established. The recently discovered cytokine IL-34 is present at the fetal-maternal interface and has immunomodulatory properties with regard to induction of decidual macrophages, which are important for a healthy pregnancy. Knowledge of growth factors related to macrophage polarization can potentially be translated to treatment of pregnancy complications involving dysregulation of this process. This study was funded by grants from the Medical Research Council (Grant K2013-61X-22310-01-04), the Research Council of South-East Sweden (FORSS), and the County Council of Östergötland, Sweden. No author has any conflicts of interest to declare.

Two Distinct Myeloid Subsets at the Term Human Fetal-Maternal Interface.

During pregnancy, immune cells infiltrate the placenta at different stages of fetal development. NK cells and macrophages are the most predominant cell types. These immune cells play pleiotropic roles, as they control spiral artery remodeling to ensure appropriate blood supply and maintain long-term tolerance to a true allograft; yet, they must be able to mount appropriate immune defenses to pathogens that may threaten the fetus. Whether the same cell type accomplishes all these tasks or if there are dedicated subsets remains controversial. Here, we identify and characterize two distinct subsets of myeloid cells that differ in their pro-inflammatory/regulatory capacity. While one subset predominantly produces the immune-modulating cytokine IL-10, the second subset has superior capacity to secrete pro-inflammatory mediators, such as IL-1β and IL-6. The putative regulatory myeloid cells also express high levels of inhibitory receptors and their ligands, including programmed cell death 1 (PD1) ligands. Importantly, a large fraction of CD8 and CD4 cells in normal term human placenta are PD1 positive, suggesting that the PD1/PD1 ligands axis might be critical to maintain tolerance during pregnancy.

Adiponectin roles in histiotrophic nutrition at the human fetal-maternal interface

Adiponectin roles in histiotrophic nutrition at the human fetal-maternal interface

Integrative transcriptome meta-analysis reveals widespread sex-biased gene expression at the human fetal-maternal interface.

As males and females share highly similar genomes, the regulation of many sexually dimorphic traits is constrained to occur through sex-biased gene regulation. There is strong evidence that human males and females differ in terms of growth and development in utero and that these divergent growth strategies appear to place males at increased risk when in sub-optimal conditions. Since the placenta is the interface of maternal–fetal exchange throughout pregnancy, these developmental differences are most likely orchestrated by differential placental function. To date, progress in this field has been hampered by a lack of genome-wide information on sex differences in placental gene expression. Therefore, our motivation in this study was to characterize sex-biased gene expression in the human placenta. We obtained gene expression data for >300 non-pathological placenta samples from 11 microarray datasets and applied mapping-based array probe re-annotation and inverse-variance meta-analysis methods which showed that >140 genes (false discovery rate (FDR) <0.05) are differentially expressed between male and female placentae. A majority of these genes (>60%) are autosomal, many of which are involved in high-level regulatory processes such as gene transcription, cell growth and proliferation and hormonal function. Of particular interest, we detected higher female expression from all seven genes in the LHB-CGB cluster, which includes genes involved in placental development, the maintenance of pregnancy and maternal immune tolerance of the conceptus. These results demonstrate that sex-biased gene expression in the normal human placenta occurs across the genome and includes genes that are central to growth, development and the maintenance of pregnancy.

Local regulation of implantation at the human fetal-maternal interface

Embryo implantation and formation of a functional placenta are complex processes that require a plethora of regulatory molecules. In recent years, many of these mediators have been identified, often from studies in experimental animals. Furthermore, their expression patterns at the embryo-maternal interface in women have been characterized and provide clues to their potential actions. What has been missing in most cases is any experimental demonstration of their function. Proteases, cytokines and chemokines are among the molecules identified at the embryo-maternal interface. Functional studies of the protease, proprotein convertase (PC)6, the gp130 cytokines, leukemia inhibitory factor (LIF) and interleukin (IL)11 and the chemokines, CX3CL1 and CCL14 demonstrate potential actions within the uterine cavity. These actions include: enhancing blastocyst development, modifying adhesive properties of the blastocyst and the uterine epithelial surface, and providing chemotactic guidance to the blastocyst. As implantation proceeds, PC6 and IL-11 also act to drive decidualization. The products (proteases, chemokines and cytokines) produced by these decidual cells provide a unique environment. This is important for both directing and restraining trophoblast invasion and for leukocyte trafficking into the decidua until the placenta is fully established.

Decidual NK cells regulate key developmental processes at the human fetal-maternal interface

Decidual NK cells regulate key developmental processes at the human fetal-maternal interface

Emerging Roles of Antiangiogenic and Angiogenic Proteins in Pathogenesis and Prediction of Preeclampsia

Hypertensive disorders are a major cause of maternal and fetal death, especially in developing nations, with the pregnancy-specific disease preeclampsia-eclampsia responsible for most of this mortality. Preeclampsia, recognized by ancient Greeks, was only sporadically investigated until late last century, current literature still labeling this disorder a “disease of theories.” Thus, not surprisingly, we have started the new millennium unable to predict or prevent preeclampsia, and management strategies remain but supportive, with pregnancy termination still the only definitive “therapy.” This may be about to change, as focused research, mainly in the past decade, has resulted in dramatic progress regarding pathogenesis of disease manifestations and risk assessment, while investigators have begun designing and testing definitive therapy.1 There are still a myriad of uncertainties and unanswered questions to address, but here we summarize the extent of 1 new and exciting chapter in preeclampsia research: the roles of angiogenic and antiangiogenic factors, to which an article in this issue by Rana and colleagues,2 contributes. A landmark report published in 2003 set the stage for all that followed.3 Dr Karumanchi’s laboratory, previously involved in renal cancer research, changed its focus to the kidney in preeclampsia. Using microarray chip technology, they probed gene expression profiles in placentas of women with preeclampsia and those with uncomplicated pregnancies. Of course many differences were noted, but one that caught the investigators’ attention was upregulation of the mRNA for the antiangiogenic protein soluble fms-like tyrosine kinase 1 (abbreviated as sFlt-1 or sVEGFR-1) in placentas from women with preeclampsia. Aware that de novo hypertension and proteinuria were 2 disturbing side effects of certain antiangiogenic compounds tested in cancer patients, these …

The role of macrophage migration inhibitory factor in maintaining the immune privilege at the fetal–maternal interface

Macrophage migration inhibitory factor (MIF) is a pivotal regulator of the innate and adaptive immunity affecting the response and behavior of macrophages and lymphocytes. MIF is also implicated in other fundamental cellular processes including angiogenesis and cell proliferation. Several studies examined the expression of MIF in reproductive organs and tissues and its involvement in different aspects of human and animal reproduction. The goal of this review was to summarize these findings and discuss, in particular, the role of MIF in the maintenance of the immune privilege at the human fetal-maternal interface.

Physiological Smooth Muscle Cell Apoptosis Contributes to the Uterine Vascular Remodeling in Human Early Pregnancy

See related article, pages 834–841 Although equipped with the entire machinery driving cell proliferation and cell death, the turnover of the vascular smooth muscle cell (VSMC) layer within the vascular wall is quite low throughout the adult normal body. Vascular wall remodeling with VSMC apoptosis is routinely considered as associated with vascular diseases. This includes the development and regression of vascular thickening in hypertension, in advanced atherosclerotic plaques where VSMC apoptosis promotes plaque rupture, after angioplasty-induced arterial injury, as well as in arterial aneurysm where apoptosis is responsible for excessive slackening and rupture of the vessel media.1 Furthermore, in several animal studies, early pregnancy is a physiological situation where vessel wall remodeling plays a vital role. Indeed, in the first trimester of human pregnancy, vascular wall remodeling through degenerative changes converts the uterine spiral arteries located within the decidua basilis into toneless, widely opened arteries, thus enabling abundant blood supply to the maternal-fetal exchange area within the placenta. It is known that extravillous cytotrophoblasts deriving from fetal cytotrophoblastic shell migrate into segments of the spiral artery wall, through retrograde endovascular (intravasation) and interstitial migratory pathways (extravasation) into the decidua basilis to trigger the disappearance of endothelial and VSMC. In this process, trophoblasts become buried intramurally within a fibrinoid layer, which replaces the original muscular medial layer. Such trophoblast invasion converts the ends of spiral arteries into a wide caliber vessel that can better deliver maternal blood to the expanding intervillous space of the placenta (Figure 1A). Defective or incomplete trophoblast invasion can result in pathological pregnancies, including preeclampsia and intrauterine growth restriction.2,3 Therefore, understanding the cellular mechanisms governing the interaction between intramural trophoblast and vascular wall cells is yet to be determined. Oversimplified schematic depicting the trophoblasts invading the spiral artery traveling from myometrium up to …

Decidual NK cells regulate key developmental processes at the human fetal-maternal interface

Human CD56(bright) NK cells accumulate in the maternal decidua during pregnancy and are found in direct contact with fetal trophoblasts. Several mechanisms have been proposed to explain the inability of NK cells to kill the semiallogeneic fetal cells. However, the actual functions of decidual NK (dNK) cells during pregnancy are mostly unknown. Here we show that dNK cells, but not peripheral blood-derived NK subsets, regulate trophoblast invasion both in vitro and in vivo by production of the interleukin-8 and interferon-inducible protein-10 chemokines. Furthermore, dNK cells are potent secretors of an array of angiogenic factors and induce vascular growth in the decidua. Notably, such functions are regulated by specific interactions between dNK-activating and dNK-inhibitory receptors and their ligands, uniquely expressed at the fetal-maternal interface. The overall results support a 'peaceful' model for reproductive immunology, in which elements of innate immunity have been incorporated in a constructive manner to support reproductive tissue development.

Complementary expression of HIP, a cell-surface heparan sulfate binding protein, and perlecan at the human fetal-maternal interface.

The human hemochorial placenta is a structure formed by the invasion of cytotrophoblasts into the uterus. Previous studies from our laboratory have demonstrated a role for heparan sulfate proteoglycans (HSPGs) and their binding proteins in interactions between human trophoblastic and uterine cell lines in vitro. In this study, expression of both mRNA and protein of a novel, cell surface, heparin/heparan sulfate interacting protein (HIP), by human trophoblastic cell lines-i.e., JAR, JEG, and BeWo-and by human cytotrophoblast was examined throughout gestation. Immunohistochemistry of the human fetal-maternal interface demonstrated abundant HIP expression in cytotrophoblast cells, with lesser staining in syncytiotrophoblast and little or no staining in surrounding stromal or decidual cells. Staining with antibodies to the basement membrane HSPG, perlecan, demonstrated a pattern of staining complementary to that of HIP. Cytotrophoblasts in the uterine stroma, not affiliated with attached villi, displayed a less intense deposition of perlecan. In vitro binding studies of 125I-perlecan to a 17-amino acid synthetic peptide sequence of HIP, which has a high affinity and specificity for heparin/heparan sulfate, indicates that perlecan binds to the HIP peptide with high affinity (KDapp = 0.6 nM) and in a heparin-inhibitable manner. Furthermore, HIP antibodies inhibited by 61-88% in vitro invasion by trophoblasts in assays using primary cultures of normal human cytotrophoblasts. Consistent with this was the observation that immunohistochemically detectable HIP expression was greatly reduced in pre-eclamptic cytotrophoblasts, a condition in which trophoblast invasion is abnormally shallow. It is suggested that HIP potentiates human cytotrophoblast interactions with HSPGs, in vivo, and facilitates trophoblast invasion processes.

Cellular localization of gp46 at the human fetal-maternal interface

gp46 is a collagen-binding heat-shock glycoprotein with a possible role in the biosynthesis of collagen as well as in cell differentiation and fusion. In this study, the relative levels of gp46 protein and its mRNA transcript were examined, as well as the mRNA levels of collagen types I and IV in first trimester and term human placental tissues. Western blot analysis revealed substantially higher levels of gp46 in first trimester placentae than in term placentae. Similarly, elevated levels of type IV collagen transcript were detected in first trimester relative to term tissues. Interestingly, the levels of gp46 and type I collagen mRNA remained unchanged. Immunohistochemical analysis of first trimester tissues demonstrated intense gp46 staining in mono-nucleated villous and extravillous cytotrophoblasts, decidual cells and in the villous connective tissue stroma. Syncytiotrophoblast in the same tissues also exhibited gp46 staining but at a reduced intensity. In chorionic villi of term placentae, faint gp46 staining was only observed in the Syncytiotrophoblast layer. However, as in the first trimester placentae, intense labelling was evident in the extravillous cytotrophoblasts and decidual cells of these tissues. These results suggest a developmental regulation of gp46 expression at the fetal-maternal interface during pregnancy and suggest a possible functional link between gp46 and collagen type IV during gestation.

Endometrial stromal cell decidualization inhibits human chorionic gonadotrophin and human placental lactogen secretion by co-cultured trophoblasts.

We have developed an in-vitro co-culture system to examine the interaction between purified first trimester cytotrophoblasts and purified non-pregnant human endometrial stromal cells (ESC). ESC decidualization is an important step in endometrial maturation and may modulate embryo implantation. In order to investigate the effects of ESC decidualization on trophoblast function, we examined human chorionic gonadotrophin (HCG), human placental lactogen (HPL), progesterone and estrogen secretion by trophoblasts co-cultured in contact with ESC, either with or without decidualization induced by progesterone. Decidualized ESC inhibited basal HCG and HPL secretion for 3 days during the culture for HCG, and for 5 days during the culture for HPL (P < 0.01 and P < 0.03 respectively). After 5 days of co-culture, decidual transformation of ESC as indicated by prolactin production occurred in the control cultures due to progesterone and oestradiol secretion by the co-cultured trophoblasts, but no significant differences in HCG or HPL secretion were observed between the two groups. Although the type of trophoblast used in the present study is far from implantation, our results clearly demonstrated that HCG and HPL secretion by trophoblasts was inhibited by the presence of co-cultured decidualized ESC, and suggested that ESC decidualization may regulate trophoblast function at the human fetal-maternal interface.

Localization of transforming growth factor-beta at the human fetal-maternal interface: role in trophoblast growth and differentiation.

We examined the localization of transforming growth factor (TGF)-beta in first-trimester and term human decidua and chorionic villi and explored the role of this factor on the proliferation and differentiation of cultured trophoblast cells. Two antibodies, 1D11.16.8, a mouse monoclonal neutralizing antibody capable of recognizing both TGF-beta 1 and TGF-beta 2 and CL-B1/29, a rabbit polyclonal antibody capable of recognizing TGF-beta 2, were used to immunolocalize TGF-beta in fixed, paraffin-embedded, or fixed, frozen sections of placenta and decidua, providing similar results. Intense labeling was observed in the extracellular matrix (ECM) of the first-trimester decidua and cytoplasm of term decidual cells. Syncytiotrophoblast cell cytoplasm as well as the ECM in the core of the chorionic villi of both first-trimester and term placentas exhibited a moderate degree of labeling. Strong cytoplasmic labeling was observed in the cytotrophoblastic shell of the term placenta. To examine the role of TGF-beta on trophoblast proliferation and differentiation, early passage cultures of first-trimester and primary cultures of term trophoblast cells were established and characterized on the basis of numerous immunocytochemical and functional markers. These cells expressed cytokeratin, placental alkaline phosphatase, urokinase-type plasminogen activator, and pregnancy-specific beta glycoprotein, but not factor VIII or 63D3; they also produced hCG and collagenase type IV. Exposure of first-trimester trophoblast cultures to TGF-beta 1 significantly inhibited proliferation in a dose-dependent manner. An antiproliferative effect was also noted in the presence of TGF-beta 2. These effects were abrogated in the presence of the neutralizing anti-TGF-beta antibody (1D11.16.8) in a concentration-dependent manner. In a 3-day culture, exogenous TGF-beta 1 stimulated formation of multinucleated cells by the first trimester as well as term trophoblast cells. Addition of neutralizing anti-TGF-beta antibody to first-trimester trophoblast cells stimulated proliferation beyond control levels in a 24-h culture and reduced formation of multinucleated cells in a 3-day culture, indicating the presence of endogenous TGF-beta activity. These results indicate that TGF-beta produced at the human fetal-maternal interface plays a major regulatory role in the proliferation and differentiation of the trophoblast.