Activation of Uterine Smad3 Pathway Is Crucial for Embryo Implantation

The Long Non-Coding RNA Gene AC027288.3 Plays a Role in Human Endometrial Stromal Fibroblast Decidualization

During the secretory phase of the menstrual cycle, endometrial fibroblast cells begin to change into large epithelial-like cells called decidual cells in a process called decidualization. This differentiation continues more broadly in the endometrium and forms the decidual tissue during early pregnancy. The cells undergoing decidualization as well as the resulting decidual cells, support successful implantation and placentation during early pregnancy. This study was carried out to identify new potentially important long non-coding RNA (lncRNA) genes that may play a role in human endometrial stromal fibroblast cells (hESF) undergoing decidualization in vitro, and several were found. The expression of nine was further characterized. One of these, AC027288.3, showed a dramatic increase in the expression of hESF cells undergoing decidualization. When AC027288.3 expression was targeted, the ability of the cells to undergo decidualization as determined by the expression of decidualization marker protein-coding genes was significantly altered. The most affected markers of decidualization whose expression was significantly reduced were FOXO1, FZD4, and INHBA. Therefore, AC027288.3 may be a major upstream regulator of the WNT-FOXO1 pathway and activin-SMAD3 pathways previously shown as critical for hESF decidualization. Finally, we explored possible regulators of AC027288.3 expression during human ESF decidualization. Expression was regulated by cAMP and progesterone. Our results suggest that AC027288.3 plays a role in hESF decidualization and identifies several other lncRNA genes that may also play a role.

Differentially Expressed Candidate miRNAs of Day 16 Bovine Embryos on the Regulation of Pregnancy Establishment in Dairy Cows

Recent advances in high-throughput in silico techniques translate experimental data into meaningful biological networks through which the role of individual proteins, interactions, and their biological functions are comprehended. The study objective was to identify differentially expressed (DE) miRNAs between the day 16 competent, elongated embryo from normal cows and the day 16 noncompetent, tubular embryos from repeat breeder cows, assimilate DE-miRNAs to their target genes, and group target genes based on biological function using in silico methods. The 84 prioritized bovine-specific miRNAs were investigated by RT-PCR, and the results showed that 19 were differentially expressed (11 up- and 8 down-regulated) in the competent embryos compared to noncompetent ones (p ≤ 0.05; fold regulation ≥ 2 magnitudes). Top-ranked integrated genes of DE-miRNAs predicted various biological and molecular functions, cellular processes, and signaling pathways. Further, analysis of the categorized groups of genes showed association with signaling pathways, turning on or off key genes and transcription factors regulating the development of embryo, placenta, and various organs. In conclusion, highly DE-miRNAs in day 16 bovine conceptus regulated the embryogenesis and pregnancy establishment. The elucidated miRNA-mRNA interactions in this study were mostly based on predictions from public databases. Therefore, the causal regulations of these interactions and mechanisms require further functional characterization.

The Human Early Maternal–Embryonic Interactome

Background: Single cell transcriptomics offers an avenue for predicting, with improved accuracy, the gene networks that are involved in the establishment of the first direct cell–cell interactions between the blastocyst and the maternal luminal epithelium. We hypothesised that in silico modelling of the maternal–embryonic interface may provide a causal model of these interactions, leading to the identification of genes associated with a successful initiation of implantation. Methods: Bulk and single cell RNA-sequencing of endometrial epithelium and scRNAseq of day 6 and 7 trophectoderm (TE) were used to model the initial encounter between the blastocyst and the maternal uterine lining epithelium in silico. In silico modelling of the maternal–embryonic interface was performed using hypernetwork (HN) analysis of genes mediating endometrial–TE interactions and the wider endometrial epithelial transcriptome. A hypernetwork analysis identifies genes that co-ordinate the expression of many other genes to derive a higher order interaction likely to be causally linked to the function. Potential interactions of TE with non-ciliated luminal cells, ciliated cells, and glandular cells were examined. Results: Prominent epithelial activities include secretion, endocytosis, ion transport, adhesion, and immune modulation. Three highly correlated clusters of 25, 22 and 26 TE-interacting epithelial surface genes were identified, each with distinct properties. Genes in both ciliated and non-ciliated luminal epithelial cells and glandular cells exhibit significant functional associations. Ciliated cells are predicted to bind to TE via galectin–glycan interaction. Day 6 and day 7 embryonic–epithelial interactomes are largely similar. The removal of aneuploid TE-derived mRNA invoked only subtle differences. No direct interaction with the maternal gland epithelial cell surface is predicted. These functional differences validate the in silico segregation of phenotypes. Single cell analysis of the epithelium revealed significant change with the cycle phase, but differences in the cell phenotype between individual donors were also present. Conclusions: A hypernetwork analysis can identify epithelial gene clusters that show correlated change during the menstrual cycle and can be interfaced with TE genes to predict pathways and processes occurring during the initiation of embryo–epithelial interaction in the mid-secretory phase. The data are on a scale that is realistic for functional dissection using current ex vivo human implantation models. A focus on luminal epithelial cells may allow a resolution to the current bottleneck of endometrial receptivity testing based on tissue lysates, which is confounded by noise from multiple diverse cell populations.

Uterine Flushing Fluid-Derived Let-7b Targets CXCL10 to Regulate Uterine Receptivity in Goats during Embryo Implantation

Exosomes have the ability to carry a wide range of chemicals, convey them to target cells or target regions, and act as "messengers." For the purpose of investigating embryo attachment, it is helpful to comprehend the range of exosomal mRNAs and miRNAs derived from the uterine flushing fluid before and after embryo attachment. In this study, we recovered exosomes from goat uterine rinsing fluid at 5, 15, and 18 days of gestation and used RNA-Seq to identify the mRNA and miRNA profiles of exosomes obtained from uterine rinsing fluid before and after embryo implantation. In total, 91 differently expressed miRNAs and 27,487 differentially expressed mRNAs were found. The target genes predicted by the differentially expressed miRNAs and the differentially expressed mRNAs were mainly membrane-related organelles with catalytic activity, binding activity, transcriptional regulation activity, and involved in metabolism, biological regulation, development, and other processes. This was revealed by GO analysis. Furthermore, KEGG analysis revealed that they were abundant in signaling pathways associated with embryo implantation, including the "PI3K-Akt signaling pathway," "Toll-like receptor signaling pathway," "TGF-beta signaling route," "Notch signaling pathway," and others. Moreover, our research has demonstrated, for the first time, that chi-let-7b-5p specifically targets the 3'UTR of CXCL10. Our research offers a fresh viewpoint on the mechanics of embryo attachment.

Establishment of Adenomyosis Organoids as a Preclinical Model to Study Infertility

Adenomyosis is related to infertility and miscarriages, but so far there are no robust in vitro models that reproduce its pathological features to study the molecular mechanisms involved in this disease. Endometrial organoids are in vitro 3D models that recapitulate the native microenvironment and reproduce tissue characteristics that would allow the study of adenomyosis pathogenesis and related infertility disorders. In our study, human endometrial biopsies from adenomyosis (n = 6) and healthy women (n = 6) were recruited. Organoids were established and hormonally differentiated to recapitulate midsecretory and gestational endometrial phases. Physiological and pathological characteristics were evaluated by immunohistochemistry, immunofluorescence, qRT-PCR, and ELISA. Secretory and gestational organoids recapitulated in vivo glandular epithelial phenotype (pan-cytokeratin, Muc-1, PAS, Laminin, and Ki67) and secretory and gestational features (α-tubulin, SOX9, SPP1, PAEP, LIF, and 17βHSD2 expression and SPP1 secretion). Adenomyosis organoids showed higher expression of TGF-β2 and SMAD3 and increased gene expression of SPP1, PAEP, LIF, and 17βHSD2 compared with control organoids. Our results demonstrate that organoids derived from endometria of adenomyosis patients and differentiated to secretory and gestational phases recapitulate native endometrial-tissue-specific features and disease-specific traits. Adenomyosis-derived organoids are a promising in vitro preclinical model to study impaired implantation and pregnancy disorders in adenomyosis and enable personalized drug screening.

Pregnancy in pigs: the journey of an early life

Embryo mortality is responsible for greater losses in litter size in pigs. It is well known that pregnancy establishment is a complex process, and important changes occur continuously in both the corpora lutea and the endometrium, which varies depending on the pre-natal development phase: embryonic, pre-implantation or fetal stages. The placenta is a key organ responsible for the exchange of nutrients, metabolites and respiratory gases between mother and fetuses. The porcine placenta is diffuse, epitheliochorial, and placentation begins with implantation, which involves specialized cell adhesion and cell migration, leading to the attachment of the trophectoderm to the uterine endometrial lumen epithelium. The efficiency with which the placenta provides adequate amounts of nutrients and oxygen to the fetus is crucial for proper fetal growth and development. In the last decades, emphasis on selection for sow prolificacy has resulted in a substantial increase in the number of piglets born per litter, which had a direct effect on piglet quality, compromising birth weight and litter uniformity. Placental insufficiency will lead to fetal intrauterine growth restriction. This review addresses the main events of early embryo development, including preimplantation and implantation periods. In addition, placentation and its role on fetal development are covered, as well as intrauterine growth restriction, as it is a natural condition in the pig, with long lasting detrimental effects to the production chain.

Paired-like homeodomain transcription factor 2 affects endometrial cell function and embryo implantation through the Wnt/β-catenin pathway

The successful implantation of embryos is crucial for pregnancy in mammals. This complex process is inevitably dependent on the development of the endometrium. The paired-like homeodomain transcription factor 2 (PITX2) is involved in a variety of biological processes, but whether it is involved in embryo implantation has not been reported. In this study, we aimed to investigate uterine expression and regulation of PITX2 during implantation. We found that PITX2 was elevated in the human endometrium in the secretory phase. The results of the pregnant mouse models showed that PITX2 expression was spatiotemporal in mouse endometrial tissue throughout peri-implantation period, and it was significantly upregulated at the time of implantation. Interestingly, PITX2 was mainly localized to the glandular epithelium cells on D2.5-3.5 of pregnancy, while D5.5-6.5 was largely expressed in stromal cells. In vitro, PITX2 regulated endometrial cells proliferation, migration, invasion, and other functions through the Wnt/β-catenin signaling pathway. In addition, a significant decrease in the rate of embryo implantation was observed after injecting PITX2 small interfering RNA into the uterine horn. These results demonstrate the effects of PITX2 on the physiological function of endometrial cells and embryo implantation, suggesting a role in the endometrial regulatory mechanism during implantation.

Embryo gene expression in pig pregnancy

Pregnancy is a complex process in which significant changes occur continually in both the corpora lutea and in the endometrium of the females and varies depending on the embryonic, pre-implantation or foetal stages. In the embryonic stages, the majority of genes expressed in the pig embryo correspond to the loss of cellular pluripotency. In contrast, the implantation consists of three phases: elongation of the conceptus, adhesion and union of the embryo to the endometrial epithelium. During these phases, many factors are expressed, including growth factors, molecules that facilitate adhesion and cytokines. All these changes are ultimately regulated by different lipid and hormonal substances, specifically by progesterone, oestradiol and prostaglandins, which regulate the expression of many proteins necessary for the development of the embryo, endometrial remodelling and embryo-maternal communication. This paper is a review of primary gene regulatory mechanisms in pigs during different stages of implantation.