Expression of αv, α4, α5 and β3 integrin subunits, fibronectin and vitronectin in goat peri-implantation

Transcriptome Comparison of Chorion-Attached and Non-chorion-attached Endometrium in Mid-gestation of Rabbit

Background

The chorion from the placenta is directly attached to the endometrium (CA) after embryo implantation while some parts of the endometrium are not chorion-attached (NCA). The differences in gene expression between the CA and NCA endometrium mid-gestation are unknown. Our objective was to compare the gene expression profiles of the CA and NCA endometrium of rabbit, to identify the differentially expressed genes (DEGs), and correlate the differences with the physiological state of the endometrium at mid-gestation of rabbit.

Methods

We used transcriptome sequencing to reveal the differences in gene expression between CA and NCA endometrium (n = 3), and then determined the concentration of inflammatory cytokines in CA and NCA tissue and serum by ELISA.

Results

Six Hundred and Forty-Six DEGs were identified between the CA and NCA endometrium [p < 0.05, |log2 (fold change) |≥ 2], The expression levels of 590 DEGs were higher in the NCA endometrium than in the CA endometrium, while the expression level of only 56 DEGs were higher in CA than in NCA. The DEGs were enriched in gene ontology (GO) terms and pathways related to immune regulation and cellular adhesions. Six hub-genes related to inflammatory mediator regulation of transient receptor potential (TRP) channels and chemokine signaling pathways had a lower expression level in the CA endometrium compared to the NCA endometrium, and the expression levels of genes related to focal adhesion and extracellular matrix (ECM)-receptors were significantly higher in NCA endometrium than in CA endometrium. The level of pro-inflammatory cytokines accumulated in the CA endometrium, and high abundance of integrin-β and THBS1 were localized in the luminal epithelium of the NCA endometrium, but not in the CA endometrium.

Conclusions

Our study reveals differences in gene expression between the CA and NCA endometrium at mid-gestation of rabbit, and suggests implications for endometrial physiological function. The CA endometrium showed relative low-level gene expression compared to the NCA endometrium, while the NCA endometrium performed physiological functions related to focal adhesion and ECM-receptor interaction.

Proteomic analysis of extracellular vesicles secreted by primary human epithelial endometrial cells reveals key proteins related to embryo implantation

BACKGROUND

Successful implantation is dependent on coordination between maternal endometrium and embryo, and the role of EVs in the required cross-talk cell-to-cell has been recently established. In this regard, it has been reported that EVs secreted by the maternal endometrium can be internalized by human trophoblastic cells transferring their contents and enhancing their adhesive and invasive capacity. This is the first study to comprehensively evaluate three EV isolation methods on human endometrial epithelial cells in culture and to describe the proteomic content of EVs secreted by pHEECs from fertile women.

METHODS

Ishikawa cells and pHEECs were in vitro cultured and hormonally treated; subsequently, conditioned medium was collected and EVs isolated. Ishikawa cells were used for the comparison of EVs isolation methods ultracentrifugation, ExoQuick-TC and Norgen Cell Culture Media Exosome Purification Kit (n = 3 replicates/isolation method). pHEECs were isolated from endometrial biopsies (n = 8/replicate; 3 replicates) collected from healthy oocyte donors with confirmed fertility, and protein content of EVs isolated by the most efficient methodology was analysed using liquid chromatography-tandem mass spectrometry. EV concentration and size were analyzed by nanoparticle tracking analysis, EV morphology visualized by transmission electron microscopy and protein marker expression was determined by Western blotting.

RESULTS

Ultracentrifugation was the most efficient methodology for EV isolation from medium of endometrial epithelial cells. EVs secreted by pHEECs and isolated by ultracentrifugation were heterogeneous in size and expressed EV protein markers HSP70, TSG101, CD9, and CD81. Proteomic analysis identified 218 proteins contained in these EVs enriched in biological processes involved in embryo implantation, including cell adhesion, differentiation, communication, migration, extracellular matrix organization, vasculature development, and reproductive processes. From these proteins, 82 were selected based on their functional relevance in implantation success as possible implantation biomarkers.

CONCLUSIONS

EV protein cargos are implicated in biological processes related to endometrial receptivity, embryo implantation, and early embryo development, supporting the concept of a communication system between the embryo and the maternal endometrium via EVs. Identified proteins may define new biomarkers of endometrial receptivity and implantation success.

Adenomyosis and Infertility-Review of Medical and Surgical Approaches

The aim of this review is to clarify the relative association between adenomyosis and infertility and the possible treatment for an infertile patient. Although adenomyosis is detected more often in women of late reproductive age, its influence on pregnancy rates is important, especially considering the tendency to delay pregnancy among women in developed countries. In this article, we present a critical analysis of the literature data concerning the impact of adenomyosis on fertility. The possible effects of treatment on the pregnancy rate will also be discussed. We conducted a literature search; publications from Pubmed, Embase and Cochrane databases published from 1982 to 2019 were retrieved using terms 'adenomyosis and infertility' and 'adenomyosis and pregnancy outcomes', extensively studied in the aspects of diagnosis, pathogenesis of infertility and possible treatment methods. Molecular studies have given deep insight into the pathogenesis of adenomyosis in the recent few years, but there is a huge discrepancy between in vitro studies and praxis. Oral contraceptive pills, anti-prostaglandins, oral or parenteral progestins, danazol and gonadotrophin-releasing hormone (GnRH) analogues have all been used to control menstrual pain and menorrhagia in women with adenomyosis, but they temporarily suppress the menstrual cycle. Additionally, endometrial ablation and hysterectomy used to alleviate pain caused by adenomyosis exclude pregnancy planning. The development of imaging techniques-ultrasound and MRI-enables the diagnosis of adenomyosis with very high accuracy nowadays, but the methods of treatment mentioned above have not given satisfactory results in women planning pregnancy. For these patients, the high-intensity-focused ultrasound method (HIFU) and combined treatment before assisted reproductive techniques can prove beneficial in adenomyosis patients.

Ozone Exposure During Implantation Increases Serum Bioactivity in HTR-8/SVneo Trophoblasts

Implantation is a sensitive window in reproductive development during which disruptions may increase the risk of adverse pregnancy outcomes including intrauterine growth restriction. Ozone exposure during implantation in rats reduces fetal weight near the end of gestation, potentially though impaired trophoblast migration and invasion and altered implantation. The current study characterized changes in ventilation, pulmonary injury, and circulating factors including hormonal, inflammatory, and metabolic markers related to exposure to ozone (0.4-1.2 ppm) for 4-h on gestation days 5 and 6 (window of implantation) in Long-Evans dams. To determine the effects of this exposure on trophoblast function, placental-derived, first trimester, HTR-8/SVneo cells were exposed to serum from air- or ozone (0.8 ppm×4 h)-exposed dams and examined for impacts on metabolic capacity, wound-closure, and invasion. Peri-implantation exposure to ozone induced ventilatory dysfunction and lung vascular leakage in pregnant rats, with little effect on most of the circulating markers measured. However, ozone inhalation induced a significant reduction in several serum cytokines (interferon-γ, interleukin-6, and interleukin-13). Treatment of HTR-8/SVneo trophoblasts with serum from ozone-exposed dams for 16-h downregulated metabolic capacity, wound-closure, and invasion through a Matrigel membrane compared with both air-serum and fetal bovine serum-treated cells. Ozone-serum treated cells increased the release of a critical inhibitor of invasion and angiogenesis (soluble fms-like receptor 1; sFlt1) compared with air-serum treatment. Together, our data suggest that circulating factors in the serum of pregnant rats exposed to ozone during implantation receptivity can hinder critical processes of implantation (eg, invasion and migration) and impair trophoblast metabolic capacity.

αvβ3 Integrin and fibronectin expressions and their relation to estrogen and progesterone during placentation in swine

Mammalian pregnancy requires specific interactions between the conceptus and its mother that involve the endocrine system and adhesion molecules. The relation between adhesion molecules and their ligands at the fetal-maternal interface is crucial for developing a successful implantation. Progesterone (P4) and estrogen (E2) secreted by the porcine conceptus are required for the relation to be established. We investigated the expression of αvβ3 integrin and its ligand, fibronectin (FN), at the placental interface, and E2 and P4 concentrations in both serum and maternal and fetal placental extracts during placentation in swine. Placental and serum samples of crossbred sows at 17, 30, 60, 70, and 114 days gestation and no pregnant uteri were used. The presence of αvβ3 and FN were determined by immunohistochemistry, and E2 and P4 by chemiluminescence in homogenates of nonpregnant uterus (HoU), swine maternal placenta (HoPM), swine fetal placenta (HoPF) and serum. The expression of αvβ3 and FN increased at the interface at 17, 30 and 60 days gestation. Immunostaining decreased by 70 days. Serum E2 levels peaked at 17 days, then decreased, then increased again near term. The highest concentration of P4 occurred in HoPF at 70 days gestation, then decreased coincident with a decline in integrin and FN expression at the placental interface. High P4 levels during swine gestation may regulate the expression of αvβ3 integrin and FN at the placental interface for up to 70 days gestation. Other adhesion molecules and their ligands likely maintain the fetal-placental interface after 70 days.

Mmu-miR-126a-3p plays a role in murine embryo implantation by regulating Itga11

miR-126a-3p has been found to be specifically up-regulated in the process of murine embryo implantation. This study aimed to further clarify the role of miR-126a-3p in embryo implantation. The expression of miR-126a-3p in implantation sites was significantly higher than that in interimplantation sites (P = 0.009). Its expression dynamics in a series of models, including pseudopregnancy, delayed implantation and artificial decidualization, suggested that the induction of miR-126a-3p is dependent on hormonal signalling and decidualization of the endometrium. Bioinformatic analysis predicted and luciferase activity assay confirmed that Itga11, a member of the integrin family, was a target gene of miR-126a-3p. miR-126a-3p bound to the 3' untranslated region of Itga11 and regulated Itga11 by inhibiting mRNA translation and affecting mRNA stability. Transwell assay showed that miR-126a-3p promoted cell migratory and invasive capacity in vitro. Loss of function of miR-126a-3p significantly reduced the number of implantation sites in vivo (P = 0.013). Collectively, miR-126a-3p may play a major role in embryo implantation by regulating Itga11, possibly through impairing cell migratory and invasive capacity. These findings should contribute to a better understanding of the miRNA-based mechanism of embryo implantation.

Label-free proteomics uncovers energy metabolism and focal adhesion regulations responsive for endometrium receptivity

The menstrual cycle of the female uterus leads to periodic changes of the endometrium. These changes are important for developing the endometrial receptivity and for achieving competency of embryo implantation. However, the molecular events underlying the endometrial receptivity process remain poorly understood. Here we applied an LC-MS-based label-free quantitative proteomic approach to compare the endometrial tissues in the midsecretory (receptive) phase with the endometrial tissues in the proliferative phase from age-matched woman (n = 6/group). The proteomes of endometrial tissues were extracted using an SDS-based detergent, digested by the filter-aided sample preparation procedures, and subsequently analyzed by nano-LC-MS/MS (Orbitrap XL) with a 4 h gradient. Reliable protein expression profiles were reproducibly obtained from the endometrial tissues in the receptive and proliferative phases. A total of 2138 protein groups were quantified under highly stringent criteria with a false discovery rate of <1% for peptide and protein groups. Among these proteins, 317 proteins had differences in expression that were statistically significant between the receptive and proliferative phases. Direct protein-protein interaction network analyses of these significantly changed proteins showed that the up-regulation of creatine kinase B-type (CKB) in the receptive phase may be related to endometrium receptivity. The interaction network also showed that proteins related to cell-cell adhesion were down-regulated. Moreover, the results from KEGG pathway analyses are consistent with the protein-protein interaction results. The proteins, including alpha-actinin (ACTN), extracellular matrix proteins, integrin alpha-V, and so on, that are involved in the focal adhesion pathway were down-regulated in the receptive phase compared with the proliferative phase, which may facilitate the implantation of the fertilized ovum. Selected proteins were validated by Western blot analysis and indirect immunofluorescence, including the up-regulation of CKB and down-regulation ACTN in the receptive phase. In summary, our proteomic analysis study shows potential for predicting the endometrial remodeling from the proliferative to the receptivity phase in women, and these results also reveal the key biological mechanisms (such as energy metabolism and focal adhesion) underlying human endometrial receptivity.

Extracellular matrix proteins secreted from both the endometrium and the embryo are required for attachment: a study using a co-culture model of rat blastocysts and Ishikawa cells

Integrins are expressed in a highly regulated manner at the maternal-fetal interface during implantation. However, the significance of extracellular matrix (ECM) ligands during the integrin-mediated embryo attachment to the endometrium is not fully understood. Thus, the distribution of fibronectin in the rat uterus and blastocyst was studied at the time of implantation. Fibronectin was absent in the uterine luminal epithelial cells but was intensely expressed in the trophoblast cells and the inner cell mass suggesting that fibronectin secreted from the blastocyst may be a possible bridging ligand for the integrins expressed at the maternal-fetal interface. An Arg-Gly-Asp (RGD) peptide was used to block the RGD recognition sites on integrins, and the effect on rat blastocyst attachment to Ishikawa cells was examined. There was a significant reduction in blastocyst attachment when either the blastocysts or the Ishikawa cells were pre-incubated with the RGD-blocking peptide. Thus, successful attachment of the embryo to the endometrium requires the interaction of integrins on both the endometrium and the blastocyst with the RGD sequence of ECM ligands, such as fibronectin. Pre-treatment of both blastocysts and Ishikawa cells with the RGD peptide also inhibited blastocyst attachment, but not completely, suggesting that ECM bridging ligands that do not contain the RGD sequence are also involved in embryo attachment.

Embryo-maternal communication: signalling before and during placentation in cattle and pig

Communication during early pregnancy is essential for successful reproduction. In this review we address the beginning of the communication between mother and developing embryo; including morphological and transcriptional changes in the endometrium as well as epigenetic regulation mechanisms directing the placentation. An increasing knowledge of the embryo-maternal communication might not only help to improve the fertility of our farm animals but also our understanding of human health and reproduction.

β(1) and β(3) integrins disassemble from basal focal adhesions and β(3) integrin is later localised to the apical plasma membrane of rat uterine luminal epithelial cells at the time of implantation

The present study investigated the expression of integrin subunits that are known to be associated with focal adhesions, namely β(1) and β(3) integrins in rat uterine luminal epithelial cells during early pregnancy. The β(1) and β(3) integrins were concentrated along the basal cell surface and were colocalised and structurally interacted with talin, a principal focal adhesion protein, on Day 1 of pregnancy. At the time of implantation, β(1) and β(3) integrins disassembled from the site of focal adhesions, facilitating the removal of uterine luminal epithelial cells for embryo invasion. Also at this time, β(3) integrin markedly increased along the apical membrane, suggesting a role in embryo attachment. This distributional change in β(1) and β(3) integrins seen at the time of implantation was predominantly under the influence of progesterone. Taken together, β(1) and β(3) integrin disassembly from focal adhesions and the increase in β(3) integrin apically are key components of hormonally regulated endometrial receptivity.

αv β3 Integrin may participate in conceptus attachment by regulating morphologic changes in the endometrium during peri-implantation in ovine

The objective of this study was to determine expression and potential functions of α(v) and β(3) integrin subunits in ovine endometrium during the peri-implantation period (days 8-17 after fertilization). The morphologic changes in the endometrium were observed histochemically following haematoxylin/eosin (HE) staining, whereas the expressions of α(v) and β(3) integrin subunits were analysed by RT-PCR, immunohistochemistry and Western blot. The filamentous conceptus attached to the luminal epithelium (LE) on day 17 of pregnancy, with no differences in endometrial morphology between days 8-12 of pregnancy. However, endometrial glands in the endometrial stroma (S) underwent extensive hyperplasia from day 14 to day 17, increased reductus of the LE with an obvious proliferation of caruncles, and an increased number and diameter of blood vessels (V) in the endometrium. The relative expression levels of α(v) and β(3) integrin subunits mRNA gradually increased until day 16, but sharply declined on day 17. Western blot analysis revealed that the expression pattern of α(v) and β(3) integrin subunit proteins paralleled that of the corresponding mRNA. In addition, immunohistochemical localization of α(v) and β(3) integrin subunits confirmed their presence in the glandular epithelium (GE), LE and endometrial stroma. Immunostaining on LE and stroma varied with the increasing days of pregnancy, with the strongest immunostaining on days 16 and 17. In conclusion, expression of α(V) and β(3) integrin subunits was closely related to the early progression of pregnancy and conceptus attachment; therefore, we inferred that α(v) β(3) integrin may participate in conceptus attachment by the regulation of endometrial morphology during peri-implantation in ovine.

Gene expression profiles of bovine caruncular and intercaruncular endometrium at implantation

At implantation the endometrium undergoes modifications necessary for its physical interactions with the trophoblast as well as the development of the conceptus. We aim to identify endometrial factors and pathways essential for a successful implantation in the caruncular (C) and the intercaruncular (IC) areas in cattle. Using a 13,257-element bovine oligonucleotide array, we established expression profiles at day 20 of the estrous cycle or pregnancy (implantation), revealing 446 and 1,295 differentially expressed genes (DEG) in C and IC areas, respectively (false discovery rate = 0.08). The impact of the conceptus was higher on the immune response function in C but more prominent on the regulation of metabolism function in IC. The C vs. IC direct comparison revealed 1,177 and 453 DEG in cyclic and pregnant animals respectively (false discovery rate = 0.05), with a major impact of the conceptus on metabolism and cell adhesion. We selected 15 genes including C11ORF34, CXCL12, CXCR4, PLAC8, SCARA5, and NPY and confirmed their differential expression by quantitative RT-PCR. The cellular localization was analyzed by in situ hybridization and, upon pregnancy, showed gene-specific patterns of cell distribution, including a high level of expression in the luminal epithelium for C11ORF34 and MX1. Using primary cultures of bovine endometrial cells, we identified PTN, PLAC8, and CXCL12 as interferon-tau (IFNT) target genes and MSX1 and CXCR7 as IFNT-regulated genes, whereas C11ORF34 was not an IFNT-regulated gene. Our transcriptomic data provide novel molecular insights accounting for the biological functions related to the C or IC endometrial areas and may contribute to the identification of potential biomarkers for normal and perturbed early pregnancy.

Expression of alphaVbeta3 integrin in rat endometrial epithelial cells and its functional role during implantation

The alpha(V)beta(3) integrin as a marker of endometrial receptivity has been well established in human and other mammalian species; however, its expression is still not known in rats. Our objective was to establish the expression of alpha(V)beta(3) integrin as a marker of endometrial receptivity in rat and to further prove its role in implantation by function-blocking studies in this species. Immunocytochemical, immunohistochemical and flow-cytometric studies were performed in rat endometrial epithelial cells (EEC) to demonstrate the expression of alpha(V)beta(3) integrin during non-receptive, pre-receptive and receptive phases of the uterus. Results revealed positive immunocytochemical staining for alpha(v) and beta(3) subunits on the surface of EEC of days 4 and 5p.c. (post-coitum), but the intensity was higher in cells of day 5p.c. Flow-cytometric study revealed higher level of alpha(V)beta(3) on day 5p.c. as compared to day 4p.c. and non-pregnant animals. Immunohistochemical analysis of uterine tissue also revealed that the alpha(V)beta(3) expression in LE was higher on day 5p.c. morning as compared to that observed on day 4p.c. In addition, the expression of beta(3) subunit was not evident in rats receiving ormeloxifene, an agent known to inhibit the uterine receptivity. Immunoblotting experiments also revealed higher expression of uterine beta(3) on day 5p.c. On day 6, expression of beta(3) was high in implantation sites than on inter-implantation sites. In immature ovariectomized rats, alpha(V)beta(3) was up-regulated by progesterone and by a combination of estrogen and progesterone. The expression of alpha(V)beta(3) was also up-regulated in EEC co-cultured with blastocysts. All the agents used for function-blocking studies showed significant reduction in the number of implantation sites in treated horn as compared to sham control horn. The present study has successfully demonstrated the expression of alpha(V)beta(3) in rat EEC as a marker of endometrial receptivity and showed that this molecule is indispensable for the process of implantation in this species.

Beta3 integrin expression within uterine endometrium and its relationship with unexplained infertility

The aim of this study was to investigate whether the endometrium of women with unexplained infertility differs in the presence of the beta 3 (beta3) integrin molecule from the endometrium of normal fertile women. In a retrospective case-control study 30 endometrial biopsies from hysterectomies with nonendometrial pathology and 30 endometrial samples from women with a history of unexplained infertility were collected during the window of implantation. Immunohistochemically staining with a monoclonal antibody against beta3 integrin subunit in endometrial biopsies was performed and then assessed semiquantitively by microscope on different endometrial compartments including glandular epithelial cells, vessels, lymphocytes, macrophages and stromal cells. Chi-square test was used to compare the expression and defect of beta3 integrin subunit between two groups. The results showed that beta3 integrin molecules were present in fertile and infertile endometrial uterine tissues. The majority of glandular epithelial cells expressed beta3 integrin in fertile endometrium. However, the endometrial expression of beta3 integrin was reduced significantly in infertile endometrium during the window of implantation (p < 0.05). A few numbers of vessels and stromal cells expressed beta3 integrin molecule with no statistical significance between the two groups. In conclusion Abnormal endometrial integrin expression is a frequent finding in women with unexplained infertility. A therapeutic potential approach in improving uterine endometrium receptivity together with up-regulation of beta3 integrin in this population of women suggested.

Expression of alphaV and beta3 integrin subunits during implantation in pig

Integrin are adhesion molecules involved in uterine-conceptus interactions during the perimplantation period. In this study, the expression of alphaV and beta3 integrin subunits in endometrium during implantation in pigs was investigated. The immunohistochemical location was performed on paraformaldehyde-fixed, paraffin-embedded tissue sections, and the mRNA expression of alphaV was detected in endometrium. In addition, serum levels of estradiol, progesterone, follicle-stimulating hormone, and luteinizing hormone were measured on Days 0, 12, 18, and 25 of pregnancy. The results indicate that endometrium expressed integrin alphaV and beta3 in all stages examined. The most intensive staining for integrin alphaV and beta3 was observed in endometrial stroma in porcine pregnancy on Day 18. The mRNA of alphaV integrin strongly expressed on Day 18, and moderately expressed on Days 12 and 25. The correlation between serum hormone level and the mRNA expression of alphaV integrin was not significant. The expression patterns of integrin alphaV and beta3 during implantation provide insights into the important physiological function of alphaVbeta3 integrin in pig, and the strong expression of integrin alphaV and beta3 in mid-implantation may indicate its crucial role in successful implantation and embryo survival.

Galectin 15 (LGALS15): A Gene Uniquely Expressed in the Uteri of Sheep and Goats that Functions in Trophoblast Attachment1

Galectins are a family of secreted animal lectins with biological roles in cell adhesion and migration. In sheep, galectin 15 (LGALS15) is expressed specifically in the endometrial luminal (LE) and superficial glandular (sGE) epithelia of the uterus in concert with blastocyst elongation during the peri-implantation period. The present study examined LGALS15 expression in the uterus of cattle, goats, and pigs. Although the bovine genome contains an LGALS15-like gene, expressed sequence tags encoding LGALS15 mRNA were found only for sheep, and full-length LGALS15 cDNAs were cloned only from endometrial total RNA isolated from pregnant sheep and goats, but not pregnant cattle or pigs. Ovine and caprine LGALS15 were highly homologous at the mRNA (95%) and protein (91%) levels, and all contained a conserved carbohydrate recognition domain and RGD recognition sequence for integrin binding. Endometrial LGALS15 mRNA levels increased after Day 11 of both the estrous cycle and pregnancy, and were considerably increased after Day 15 of pregnancy in goats. In situ hybridization detected abundant LGALS15 mRNA in endometrial LE and sGE of early pregnant goats, but not in cattle or pigs. Immunoreactive LGALS15 protein was present in endometrial epithelia and conceptus trophectoderm of goat uteri and detected within intracellular crystal structures in trophectoderm and LE. Recombinant ovine and caprine LGALS15 proteins elicited a dose-dependent increase in ovine trophectoderm cell attachment in vitro that was comparable to bovine fibronectin. These results support the hypothesis that LGALS15 is uniquely expressed in Caprinae endometria and functions as an attachment factor important for peri-implantation blastocyst elongation.