Decidual glycodelin-A polarizes human monocytes into a decidual macrophage-like phenotype through Siglec-7.

Decidual macrophages constitute 20-30% of the total leukocytes in the uterus of pregnant women, regulating the maternal immune tolerance and placenta development. Abnormal number or activities of decidual macrophages (dMs) are associated with fetal loss and pregnancy complications, such as preeclampsia. Monocytes differentiate into dMs in a decidua-specific microenvironment. Despite their important roles in pregnancy, the exact factors that regulate the differentiation into dMs remain unclear. Glycodelin-A (PAEP, hereafter referred to as GdA) is a glycoprotein that is abundantly present in the decidua, and plays an important role in fetomaternal defense and placental development. It modulates the differentiation and activity of several immune cell types residing in the decidua. In this study, we demonstrated that GdA induces the differentiation of human monocytes into dM-like phenotypes in terms of transcriptome, cell surface marker expression, secretome, and regulation of trophoblast and endothelial cell functions. We found that Sialic acid-binding Ig-like lectin 7 (Siglec-7) mediates the binding and biological actions of GdA in a sialic acid-dependent manner. We, therefore, suggest that GdA, induces the polarization of monocytes into dMs to regulate fetomaternal tolerance and placental development.

Adrenomedullin insufficiency alters macrophage activities in fallopian tube: a pathophysiologic explanation of tubal ectopic pregnancy.

Ectopic pregnancy is the major cause of maternal morbidity and mortality in the first trimester of pregnancy. Tubal ectopic pregnancy (TEP) accounts for nearly 98% of all ectopic pregnancies. TEP is usually associated with salpingitis but the underlying mechanism in salpingitis leading to TEP remains unclear. Adrenomedullin (ADM) is a peptide hormone abundantly expressed in the fallopian tube with potent anti-inflammatory activities. Its expression peaks at the early luteal phase when the developing embryo is being transported through the fallopian tube. In the present study, we demonstrated reduced expression of ADM in fallopian tubes of patients with salpingitis and TEP. Using macrophages isolated from the fallopian tubes of these women, our data revealed that the salpingistis-associated ADM reduction contributed to aggravated pro-inflammatory responses of the tubal macrophages resulting in production of pro-inflammatory and pro-implantation cytokines IL-6 and IL-8. These cytokines activated the expression of implantation-associated molecules and Wnt signaling pathway predisposing the tubal epithelium to an adhesive and receptive state for embryo implantation. In conclusion, this study provided evidence for the role of ADM in the pathogenesis of TEP through regulating the functions of tubal macrophages.

Alteration of the immune cell profiles in the pathophysiology of tubal ectopic pregnancy.

Tubal ectopic pregnancy (TEP) refers to implantation of conceptus in the fallopian tube. It makes up over 98% of ectopic pregnancy (EP), which is the leading cause of maternal morbidity and mortality in the first trimester of pregnancy. Immune cells at the maternal-fetal interface play important roles in the process of embryo implantation, stroma decidualization, and early placental development. Alterations in the composition, phenotype, and activity of the immune cells in the fallopian tubes contribute toward the onset of TEP. In this review, we compare the leukocytic proportions in decidua of normal pregnancy, and in decidua and fallopian tubes of TEP. The possible functions of these immune cells in the pathophysiology of TEP are also discussed.

Glycodelin-A stimulates the conversion of human peripheral blood CD16-CD56bright NK cell to a decidual NK cell-like phenotype.

STUDY QUESTION: Does glycodelin-A (GdA) induce conversion of human peripheral blood CD16-CD56bright natural killer (NK) cells to decidual NK (dNK) cells to facilitate placentation? SUMMARY ANSWER: GdA binds to blood CD16-CD56bright NK cells via its sialylated glycans and converts them to a dNK-like cells, which in turn regulate endothelial cell angiogenesis and trophoblast invasion via vascular endothelial growth factor (VEGF) and insulin-like growth factor-binding protein 1 (IGFBP-1) secretion, respectively. WHAT IS KNOWN ALREADY: dNK cells are the most abundant leucocyte population in the decidua. These cells express CD16-CD56bright phenotype. Peripheral blood CD16-CD56bright NK cells and hematopoietic precursors have been suggested to be capable of differentiating towards dNK cells upon exposure to the decidual microenvironment. These cells regulate trophoblast invasion during spiral arteries remodelling and mediate homoeostasis and functions of the endothelial cells. GdA is an abundant glycoprotein in the human decidua with peak expression between the 6th and 12th week of gestation, suggesting a role in early pregnancy. Indeed, GdA interacts with and modulates functions and differentiation of trophoblast and immune cells in the human feto-maternal interface. Aberrant GdA expression during pregnancy is associated with unexplained infertility, pregnancy loss and pre-eclampsia. STUDY DESIGN, SIZE, DURATION: CD16+CD56dim, CD16-CD56bright and dNK cells were isolated from human peripheral blood and decidua tissue, respectively, by immuno-magnetic beads or fluorescence-activated cell sorting. Human extravillous trophoblasts were isolated from first trimester placental tissue after termination of pregnancy. Biological activities of the cells were studied after treatment with GdA at a physiological dose of 5 µg/mL. GdA was purified from human amniotic fluid by immuno-affinity chromatography. PARTICIPANTS/MATERIALS, SETTING, METHODS: Expression of VEGF, CD9, CD49a, CD151 and CD158a in the cells were determined by flow cytometry. Angiogenic proteins in the spent media of NK cells were determined by cytokine array and ELISA. Blocking antibodies were used to study the functions of the identified angiogenic proteins. Endothelial cell angiogenesis was determined by tube formation and trans-well migration assays. Cell invasion and migration were determined by trans-well invasion/migration assay. Binding of normal and de-sialylated GdA, and expression of L-selectin and siglec-7 on the NK cells were analysed by flow cytometry. The association between GdA and L-selectin on NK cells was confirmed by immunoprecipitation. Extracellular signal-regulated protein kinases (ERK) activation was determined by Western blotting and functional assays. MAIN RESULTS AND THE ROLE OF CHANCE: GdA treatment enhanced the expression of dNK cell markers CD9 and CD49a and the production of the functional dNK secretory product VEGF in the peripheral blood CD16-CD56bright NK cells. The spent media of GdA-treated CD16-CD56bright NK cells promoted tube formation of human umbilical vein endothelial cells and invasiveness of trophoblasts. These stimulatory effects were mediated by the stimulatory activities of GdA on an ERK-activation dependent production of VEGF and IGFBP-1 by the NK cells. GdA had a stronger binding affinity to the CD16-CD56bright NK cells as compared to the CD16+CD56dim NK cells. This GdA-NK cell interaction was reduced by de-sialylation. GdA interacted with L-selectin, expressed only in the CD16-CD56bright NK cells, but not in the CD16+CD56dim NK cells. Anti-L-selectin functional blocking antibody suppressed the binding and biological activities of GdA on the NK cells. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: Some of the above findings are based on a small sample size of peripheral blood CD16-CD56bright NK cells. These results need to be confirmed with human primary dNK cells. WIDER IMPLICATIONS OF THE FINDINGS: This is the first study on the biological role of GdA on conversion of CD16-CD56bright NK cells to dNK-like cells. Further investigation on the glycosylation and functions of GdA will enhance our understanding on human placentation and placenta-associated complications with altered NK cell biology. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the Hong Kong Research Grant Council Grant 17122415, Sanming Project of Medicine in Shenzhen, the Finnish Cancer Foundation, Sigrid Jusélius Foundation and the Finnish Society of Clinical Chemistry. The authors have no competing interests to declare.

The Pleiotropic Effect of Glycodelin-A in Early Pregnancy.

Successful pregnancy depends largely on adequate placentation and maternal tolerance of the fetus. Glycodelin-A is a glycoprotein abundant in the decidua during early pregnancy. It plays an important role in placental development and fetomaternal defense. Glycodelin-A interacts by its unique carbohydrate side chains with the cell surface of various cell types in the human fetomaternal interface, particularly the trophoblasts and the immune cells, and modulates their functions and differentiation to permit successful pregnancy. Abnormal levels of glycodelin-A in the endometrium, uterine flushings, and/or maternal serum correlate with unexplained infertility, early pregnancy loss, and recurrent miscarriage. This review integrates recent studies on the role of glycodelin-A in placental development and fetomaternal tolerance in early pregnancy.

Soluble human leukocyte antigen G5 polarizes differentiation of macrophages toward a decidual macrophage-like phenotype.

STUDY QUESTION: What are the actions of soluble human leukocyte antigen G5 (sHLAG5) on macrophage differentiation? SUMMARY ANSWER: sHLAG5 polarizes the differentiation of macrophages toward a decidual macrophage-like phenotype, which could regulate fetomaternal tolerance and placental development. WHAT IS KNOWN ALREADY: sHLAG5 is a full-length soluble isoform of human leukocyte antigen implicated in immune tolerance during pregnancy. Low or undetectable circulating level of sHLAG5 in first trimester of pregnancy is associated with pregnancy complications such as pre-eclampsia and spontaneous abortion. Decidual macrophages are located in close proximity to invasive trophoblasts, and are involved in regulating fetomaternal tolerance and placental development. STUDY DESIGN, SIZE, DURATION: Human peripheral blood monocytes were differentiated into macrophages by treatment with granulocyte macrophage colony-stimulating factor in the presence or absence of recombinant sHLAG5 during the differentiation process. The phenotypes and the biological activities of the resulting macrophages were compared. PARTICIPANTS/MATERIALS, SETTING, METHODS: Recombinant sHLAG5 was produced in Escherichia coli BL21 and the protein identity was verified by tandem mass spectrometry. The expression of macrophage markers were analyzed by flow cytometry and quantitative PCR. Phagocytosis was determined by flow cytometry. Indoleamine 2,3-dioxygenase 1 expression and activity were measured by western blot analysis and kynurenine assay, respectively. Cell proliferation and cell cycling were determined by fluorometric cell proliferation assay and flow cytometry, respectively. Cytokine secretion was determined by cytokine array and ELISA kits. Intracellular cytokine expression was measured by flow cytometry. Cell invasion and migration were determined by trans-well invasion and migration assay, respectively. MAIN RESULTS AND THE ROLE OF CHANCE: sHLAG5 drove the differentiation of macrophages with 'immuno-modulatory' characteristics, including reduced expression of M1 macrophage marker CD86 and increased expression of M2 macrophage marker CD163. sHLAG5-polarized macrophages showed enhanced phagocytic activity. They also had higher expression and activity of indoleamine 2,3-dioxygenase 1, a phenotypic marker of decidual macrophages, which inhibited proliferation of autologous T-cells via induction of G0/G1 cell cycle arrest. In addition, sHLAG5-polarized macrophages had an increased secretion of interleukin-6 and C-X-C motif ligand 1, which inhibited interferon-γ production in T-cells and induction of trophoblast invasion, respectively. LIMITATIONS, REASONS FOR CAUTION: Most information on the phenotypes and biological activities of human decidual macrophages are based on past literatures. A direct comparison between sHLAG5-polarized macrophages and primary decidual macrophages is required to verify the present observations. WIDER IMPLICATIONS OF THE FINDINGS: This is the first study on the role of sHLAG5 in macrophage differentiation. Further study on the mechanism that regulates the differentiation process of macrophages would enhance our understanding on the physiology of early pregnancy. STUDY FUNDING/COMPETING INTERESTS: This work was supported in part by the Hong Kong Research Grant Council Grant HKU774212 and the University of Hong Kong Grant 201309176126. The authors have no competing interests to declare. TRIAL REGISTRATION NUMBER: Nil.