Search

BACKGROUND The establishment of maternal–fetal crosstalk is vital to a successful pregnancy. Glycosylation is a post-translational modification in which glycans (monosaccharide chains) are attached to an organic molecule. Glycans are involved in many physiological and pathological processes. Human endometrial epithelium, endometrial gland secretions, decidual immune cells, and trophoblasts are highly enriched with glycoconjugates and glycan-binding molecules important for a healthy pregnancy. Aberrant glycosylation in the placenta and uterus has been linked to repeated implantation failure and various pregnancy complications, but there is no recent review summarizing the functional roles of glycosylation at the maternal–fetal interface and their associations with pathological processes. OBJECTIVE AND RATIONALE This review aims to summarize recent findings on glycosylation, glycosyltransferases, and glycan-binding receptors at the maternal–fetal interface, and their involvement in regulating the biology and pathological conditions associated with endometrial receptivity, placentation and maternal–fetal immunotolerance. Current knowledge limitations and future insights into the study of glycobiology in reproduction are discussed. SEARCH METHODS A comprehensive PubMed search was conducted using the following keywords: glycosylation, glycosyltransferases, glycan-binding proteins, endometrium, trophoblasts, maternal–fetal immunotolerance, siglec, selectin, galectin, repeated implantation failure, early pregnancy loss, recurrent pregnancy loss, preeclampsia, and fetal growth restriction. Relevant reports published between 1980 and 2023 and studies related to these reports were retrieved and reviewed. Only publications written in English were included. OUTCOMES The application of ultrasensitive mass spectrometry tools and lectin-based glycan profiling has enabled characterization of glycans present at the maternal–fetal interface and in maternal serum. The endometrial luminal epithelium is covered with highly glycosylated mucin that regulates blastocyst adhesion during implantation. In the placenta, fucose and sialic acid residues are abundantly presented on the villous membrane and are essential for proper placentation and establishment of maternal–fetal immunotolerance. Glycan-binding receptors, including selectins, sialic-acid-binding immunoglobulin-like lectins (siglecs) and galectins, also modulate implantation, trophoblast functions and maternal–fetal immunotolerance. Aberrant glycosylation is associated with repeated implantation failure, early pregnancy loss and various pregnancy complications. The current limitation in the field is that most glycobiological research relies on association studies, with few studies revealing the specific functions of glycans. Technological advancements in analytic, synthetic and functional glycobiology have laid the groundwork for further exploration of glycans in reproductive biology under both physiological and pathological conditions. WIDER IMPLICATIONS A deep understanding of the functions of glycan structures would provide insights into the molecular mechanisms underlying their involvement in the physiological and pathological regulation of early pregnancy. Glycans may also potentially serve as novel early predictive markers and therapeutic targets for repeated implantation failure, pregnancy loss, and other pregnancy complications. [ABSTRACT FROM AUTHOR]

Pregnancy involves a wide range of adaptations in the maternal body. Maternal immune tolerance toward the foreign fetus is critical for a successful pregnancy. Decidual macrophages are the primary antigen-presenting and phagocytic cells responsible for antigen presentation and apoptotic cell removal. Their phenotype changes dynamically during pregnancy. Placenta-derived exosomes are small vesicles carrying active biological molecules such as microRNAs, proteins, and lipids. The placenta-derived exosomes have been implicated in endothelial cell activation, smooth muscle cell migration, and T-cell apoptosis, but it is unknown whether placenta-derived exosomes would affect the development and functions of decidual macrophages. In this study, we reported that placenta-derived exosomes stimulated macrophage polarization into alternatively activated (M2) macrophages. Mechanistically, miRNA-30d-5p from the placenta-derived exosomes induced macrophage polarization to the M2 phenotype by targeting histone deacetylase 9. Furthermore, the conditioned medium of placenta-derived exosome–treated macrophages promoted trophoblast migration and invasion. By contrast, the conditioned medium impaired the ability of endothelial cell tube formation and migration. Placenta-derived exosome–treated macrophages had no impact on T-cell proliferation. Together, we demonstrated that placenta-derived exosomes polarize macrophages to acquire a decidua-like macrophage phenotype to modulate trophoblast and endothelial cell functions. [ABSTRACT FROM AUTHOR]

Study Question: Will use of oral progestogen in women with threatened miscarriage in the first trimester reduce the miscarriage rate when compared with placebo?Summary Answer: Use of oral progestogen in women with threatened miscarriage in the first trimester did not reduce miscarriage before 20 weeks when compared with placebo.What Is Known Already: Miscarriage is a common complication of pregnancy and occurs in 15-20% of clinically recognized pregnancies. Use of vaginal progestogens is not effective in reducing miscarriage but there is still no good evidence to support use of oral progestogen for the treatment of threatened miscarriage.Study Design, Size, Duration: This was a randomized double-blind controlled trial. A total of 406 women presenting with threatened miscarriage in the first trimester were recruited from 30 March 2016 to May 2018.Participants/materials, Setting, Methods: Women attending Early Pregnancy Assessment Clinics because of vaginal bleeding during the first trimester were recruited and randomly assigned to use dydrogesterone 40 mg orally, followed by 10 mg orally three times a day or placebo until 12 completed weeks of gestation or 1 week after the bleeding stopped, whichever was later. The primary outcome was the miscarriage rate before 20 weeks of gestation.Main Results and the Role Of Chance: The two groups of women had comparable age, BMI, number of previous miscarriages, gestation and ultrasound findings at presentation. The miscarriage rate before 20 weeks of gestation was similar in both groups, being 12.8% (26/203) in the progestogen group and 14.3% (29/203) in the placebo group (relative risk 0.897, 95% CI 0.548-1.467; P = 0.772). The live birth rate was 81.3% in the progestogen group versus 83.3% in the placebo group (P = 0.697). No significant differences were found between the two groups in terms of obstetric outcomes and side effects.Limitations, Reasons For Caution: The primary outcome was the miscarriage rate, rather than the live birth rate. Women were recruited from Early Pregnancy Assessment Clinics and those with heavy vaginal bleeding might be admitted into wards directly instead of attending Early Pregnancy Assessment Clinic. The severity of vaginal bleeding was subjectively graded by women themselves. The sample size was not adequate to demonstrate a smaller difference in the miscarriage rate between the progestogen and placebo groups. We did not exclude women with multiple pregnancy, which increased the risk of miscarriage although there was only one set of twin pregnancy in the placebo group.Wider Implications Of the Findings: Use of oral progestogen is not recommended in women with threatened miscarriage in the first trimester.Study Funding/competing Interest(s): This study was funded by the Health and Medical Research Fund, HKSAR (reference number 12132341). All authors declared no conflict of interest.Trial Registration Number: ClinicalTrials.gov with an identifier NCT02128685.Trial Registration Date: 1 May 2014.Date Of First Patient's Enrolment: 30 March 2016. [ABSTRACT FROM AUTHOR]