Embryo-maternal Interactions Research Articles

Effects of intrauterine extracellular vesicle microRNAs on embryonic gene expression in low-fertility cows.

Embryo survival and pre-implantation development depend on uterine luminal fluid, which is believed to play a role in early embryonic death and infertility in cows. Extracellular vesicles (EVs) in the uterine luminal fluid contain microRNAs (miRNAs), crucial mediators of intercellular communication. miRNAs regulate conceptus-maternal interactions and participate in embryonic development by suppressing gene expression. Therefore, we hypothesized that miRNAs in the intrauterine EVs of low-fertility cows would hinder embryonic survival and development. EVs were collected from the bovine uterine luminal fluid of both normal- and low-fertility cows 7 days post-estrus. Small RNA-sequencing analysis of miRNAs isolated from these EVs identified eight miRNAs that were highly expressed in normal-fertility cows (normal-fertility miRNAs) and eight with elevated expression in low-fertility cows (low-fertility miRNAs). These two sets of miRNAs were transfected into hatched blastocysts via lipofection. RNA-seq following lipofection with low-fertility miRNAs identified 424 differentially expressed genes (DEGs) relative to the control; in contrast, following lipofection with normal-fertility miRNAs, seven DEGs were identified. Pathway analysis of the DEGs identified following lipofection with low-fertility miRNAs revealed substantial enrichment of mitogen-activated protein kinase (MAPK) signaling. Expression of activator protein 1 (AP1) and interferon-tau (IFNT) mRNA was significantly lower in the low-fertility miRNA transfection group than in the control. IFNT is essential for maternal pregnancy recognition. Therefore, miRNAs in intrauterine EVs from low-fertility cows at 7 days post-estrus may inhibit embryo development and suppress IFNT expression by altering MAPK signaling.

Plasma Lipidomics Reveals Lipid Signatures of Early Pregnancy in Mares

Understanding the systemic biochemistry of early pregnancy in the mare is essential for developing new diagnostics and identifying causes for pregnancy loss. This study aimed to elucidate the dynamic lipidomic changes occurring during the initial stages of equine pregnancy, with a specific focus on days 7 and 14 post-ovulation. By analysing and comparing the plasma lipid profiles of pregnant and non-pregnant mares, the objective of this study was to identify potential biomarkers for pregnancy and gain insights into the biochemical adaptations essential for supporting maternal recognition of pregnancy and early embryonic development. Employing discovery lipidomics, we analysed plasma samples from pregnant and non-pregnant mares on days 7 and 14 post-conception using the SCIEX ZenoTOF 7600 system. This high-resolution mass spectrometry approach enabled us to comprehensively profile and compare the lipidomes across these critical early gestational timepoints. Our analysis revealed significant lipidomic alterations between pregnant and non-pregnant mares and between days 7 and 14 of pregnancy. Key findings include the upregulation of bile acids, sphingomyelins, phosphatidylinositols, and triglycerides in pregnant mares. These changes suggest enhanced lipid synthesis and mobilization, likely associated with the embryo’s nutritional requirements and the establishment of embryo–maternal interactions. There were significant differences in lipid metabolism between pregnant and non-pregnant mares, with a notable increase in the sterol lipid BA 24:1;O5 in pregnant mares as early as day 7 of gestation, suggesting it as a sensitive biomarker for early pregnancy detection. Notably, the transition from day 7 to day 14 in pregnant mares is characterized by a shift towards lipids indicative of membrane biosynthesis, signalling activity, and preparation for implantation. The study demonstrates the profound lipidomic shifts that occur in early equine pregnancy, highlighting the critical role of lipid metabolism in supporting embryonic development. These findings provide valuable insights into the metabolic adaptations during these period and potential biomarkers for early pregnancy detection in mares.

P-187 Profiling secreted proteins in human embryos: Time-specific discrimination of ploidy and confirmation of enhanced post-implantation development with maternal co-culture

Abstract Study question Can proteins released by embryos into culture medium between 7- and 14-days post-fertilization (d.p.f.) potentially function as biomarkers indicating the ploidy status of the embryos? Summary answer Combined secreted levels of calreticulin (CALR), human Placental Lactogen (hPL), Placental Growth Factor (PlGF) and human Pappalysin-1 (PAPP-A) differentiate euploid from chromosome 21-aneuploid embryos. What is known already Exploring post-implantation embryo development is vital due to potential errors impacting early pregnancy or postnatal health during this period. Trisomy 21 (T21) is a common aneuploidy that can lead to live births but with postnatal health concerns, while chromosome 21 monosomy (M21) often results in embryo developmental arrest. Understanding post-implantation development and secreted products into human post-implantation niche is crucial for unraveling embryo-maternal interactions. Building on prior studies indicating ploidy-related gene and metabolite expression in pre-implantation embryos (DOI:10.1016/j.fertnstert.2019.01.023), this study aims to assess variations in the secretome of embryos with different ploidy during post-implantation development. Study design, size, duration Comparative study involving 48 science-donated human 6 d.p.f. blastocysts initiating hatching coming from in-vitro fertilization cycles. Preimplantation genetic testing identified Euploid (n = 20), pure T21 (n = 14), and pure M21 (n = 14) embryos. Two extended in-vitro culture protocols were compared: co-culturing of human embryos in a 3D system with endometrial cells or in a culture medium designed for post-implantation development but lacking maternal cells. Participants/materials, setting, methods Euploid, T21 and M21 blastocysts were thawed and cultured in-vitro until 14 d.p.f. in both culture systems described above. Levels of CALR, hPL, PlGF and PAPP-A in conditioned embryo media were quantified by ELISA immunoassays at 7, 10, 12 and 14 d.p.f. Absolute secreted protein concentrations (ng/mL) in each case were compared by two-way ANOVA followed by Tukey’s test for multiple comparisons. P < 0.05 was consider as statistically significant. Main results and the role of chance In both culture systems tested, at 7 d.p.f. secreted CALR, hPL and PlGF by M21 embryos were diminished when compared to euploid embryos (p < 0.01). At 10 d.p.f., euploid embryos displayed a significant increase in secreted PAPP-A, surpassing levels in T21 (p < 0.05) and M21 embryos (p < 0.01). Embryo co-culture in 3D endometrial systems led to progressive increase in secreted PAPP-A and PlGF by euploid embryos at 14 d.p.f. compared to earlier timepoints (7 d.p.f.,p<0.01; 10d.p.f.,p<0.05). PAPP-A secretion did not increase in T21 embryos during extended culture. T21 embryos demonstrated decreased PAPP-A secretion at 10, 12, and 14 d.p.f. compared to euploid embryos (p < 0.01 in all cases). Secreted PlGF in T21 embryos rose significantly at 12 (p < 0.05) and 14 d.p.f. (p < 0.05), despite consistently lower levels than euploid embryos (p < 0.01). All studied proteins showed significantly diminished secretions during post-implantation development in M21 embryos compared to euploid ones. Comparing culture systems, the absence of maternal cells led to a significant decrease in secreted protein levels and viability impairment beyond 11 d.p.f. Consequently, only two timepoints (7- 10d.p.f.) were considered for analysis in this culture system. The findings underscore the potential of these secreted biomarkers for distinguishing embryo ploidy, with maternal co-culture supporting enhanced developmental outcomes. Limitations, reasons for caution This is an in-vitro pilot study that should be validated in larger cohorts. Wider implications of the findings Secretions of CALR, hPL, and PlGF at 7 d.p.f. effectively distinguish M21 embryos, while PAPP-A and PlGF secretions at 10-12 d.p.f. are indicative of embryo ploidy. Additionally, co-culturing with maternal cells notably promotes proper embryo development, particularly enhancing trophoblast differentiation and secretion of trophoblast-related proteins. Funding: ISCII(PI20/00405;PI23/00860;FI18/00009;MV21/00086); GVA (CIAICO/2022/203;CIAPOT/2022/18) and IDI-20210916 Trial registration number Not Applicable

In Vitro Culture of Mammalian Embryos: Is There Room for Improvement?

Preimplantation embryo culture, pivotal in assisted reproductive technology (ART), has lagged in innovation compared to embryo selection advancements. This review examines the persisting gap between in vivo and in vitro embryo development, emphasizing the need for improved culture conditions. While in humans this gap is hardly estimated, animal models, particularly bovines, reveal clear disparities in developmental competence, cryotolerance, pregnancy and live birth rates between in vitro-produced (IVP) and in vivo-derived (IVD) embryos. Molecular analyses unveil distinct differences in morphology, metabolism, and genomic stability, underscoring the need for refining culture conditions for better ART outcomes. To this end, a deeper comprehension of oviduct physiology and embryo transport is crucial for grasping embryo-maternal interactions' mechanisms. Research on autocrine and paracrine factors, and extracellular vesicles in embryo-maternal tract interactions, elucidates vital communication networks for successful implantation and pregnancy. In vitro, confinement, and embryo density are key factors to boost embryo development. Advanced dynamic culture systems mimicking fluid mechanical stimulation in the oviduct, through vibration, tilting, and microfluidic methods, and the use of innovative softer substrates, hold promise for optimizing in vitro embryo development.

LIF-STAT signaling in decidual cells: a possible role in embryo implantation and early pregnancy.

In this study, we investigate the effects of miRNA-138-5p and probable G-protein coupled receptor 124 (GPR124)-regulated inflammasome and downstream leukemia inhibitory factor (LIF)-STAT and adhesion molecule signaling in human decidual stromal cells. After informed consent was obtained from women aged 25-38 years undergoing surgical termination of the normal pregnancy and spontaneous miscarriage after 6-9 weeks of gestation, human decidual stromal cells were extracted from the decidual tissue. Extracellular vesicles (EVs) with microRNA (miRNA) between cells have been regarded as critical factors for embryo-maternal interactions on embryo implantation and programming of human pregnancy. MicroRNA-138-5p acts as the transcriptional regulator of GPR124 and the mediator of downstream inflammasome. LIF-regulated STAT activation and expression of integrins might influence embryo implantation. Hence, a better understanding of LIF-STAT and adhesion molecule signaling would elucidate the mechanism of microRNA-138-5p- and GPR124-regulated inflammasome activation on embryo implantation and pregnancy. Our results show that microRNA-138-5p, purified from the EVs of decidual stromal cells, inhibits the expression of GPR124 and the inflammasome, and activates the expression of LIF-STAT and adhesion molecules in human decidual stromal cells. Additionally, the knockdown of GPR124 and NLRP3 through siRNA increases the expression of LIF-STAT and adhesion molecules. The findings of this study help us gain a better understanding the role of EVs, microRNA-138-5p, GPR124, inflammasomes, LIF-STAT, and adhesion molecules in embryo implantation and programming of human pregnancy.

Proteomic Approaches to Unravel the Molecular Dynamics of Early Pregnancy in Farm Animals: An In-Depth Review.

Infertility is a major problem in farm animals, which has a negative economic effect on farm industries. Infertility can be defined as the inability of animals to achieve a successful pregnancy. Early pregnancy is crucial to establish a successful pregnancy, and it is reported that 70-80% and 20-30% of total embryonic loss occur in cattle and pigs, respectively, during the first month of pregnancy. The advanced high-throughput proteomics techniques provide valuable tools for in-depth understanding of the implantation process in farm animals. In the present review, our goal was to compile, assess, and integrate the latest proteomic research on farm animals, specifically focused on female reproduction, which involves endometrial tissues, uterine fluids, oviductal fluids, and microRNAs. The series of studies has provided in-depth insights into the events of the implantation process by unfolding the molecular landscape of the uterine tract. The discussed data are related to pregnant vs. non-pregnant animals, pregnancy vs. oestrous cycle, different days of the early pregnancy phase, and animals with uterine infections affecting reproduction health. Some of the studies have utilized non-invasive methods and in vitro models to decipher the molecular events of embryo-maternal interaction. The proteomics data are valuable sources for discovering biomarkers for infertility in ruminants and new regulatory pathways governing embryo-uterine interaction, endometrium receptivity, and embryonic development. Here, we envisage that the identified protein signatures can serve as potential therapeutic targets and biomarkers to develop new therapeutics against pregnancy diseases.

Advanced maternal age leads to changes within the insulin/IGF system and lipid metabolism in the reproductive tract and preimplantation embryo: insights from the rabbit model.

Reproductive potential in women declines with age. The impact of ageing on embryo-maternal interactions is still unclear. Rabbits were used as a reproductive model to investigate maternal age-related alterations in reproductive organs and embryos on Day 6 of pregnancy. Blood, ovaries, endometrium, and blastocysts from young (16-20 weeks) and advanced maternal age phase (>108 weeks, old) rabbits were analysed at the mRNA and protein levels to investigate the insulin-like growth factor (IGF) system, lipid metabolism, and stress defence system. Older rabbits had lower numbers of embryos at Day 6 of pregnancy. Plasma insulin and IGF levels were reduced, which was accompanied by paracrine regulation of IGFs and their receptors in ovaries and endometrium. Embryos adapted to hormonal changes as indicated by reduced embryonic IGF1 and 2 levels. Aged reproductive organs increased energy generation from the degradation of fatty acids, leading to higher oxidative stress. Stress markers, including catalase, superoxide dismutase 2, and receptor for advanced glycation end products were elevated in ovaries and endometrium from aged rabbits. Embryonic fatty acid uptake and β-oxidation were increased in both embryonic compartments (embryoblast and trophoblast) in old rabbits, associated with minor changes in the oxidative and glycative stress defence systems. In summary, the insulin/IGF system, lipid metabolism, and stress defence were dysregulated in reproductive tissues of older rabbits, which is consistent with changes in embryonic metabolism and stress defence. These data highlight the crucial influence of maternal age on uterine adaptability and embryo development.

Embryo-maternal interaction is associated with the location of the embryo during the mobility phase in mares

Despite advances in the molecular analysis of the endometrium during early equine pregnancy, little is known about embryo-maternal interaction during the embryo mobility phase. It has been demonstrated that the embryo stimulates upregulation of prostaglandin synthase (PTGES) locally in the endometrium. This suggests that endometrial gene expression is influenced by the location of the embryo in the uterus. The aim of this study was to characterize the transcriptome of the endometrium of mares based on the location of the mobile embryo and to compare the gene expression of the endometrium between the uterine horns of pregnant (n = 8) and non-bred (n = 8) mares. On day 12 (D0 = ovulation), a cytobrush was used to collect endometrial samples from the middle of the uterine horn of pregnant mares that did (PE) and did not (PWE) contain the embryo, and from the middle of both uterine horns of non-bred mares (NB). RNA was extracted, followed by library preparation and total RNA-sequencing (PE-150bp). On average, 40 million reads were generated per sample. Reads were trimmed and mapped to the current equine reference genome (Ecab 3.0). Differentially expressed genes (DEGs) were identified using Deseq2 (P value < 0.01) and gene ontology (GO) analysis was performed using Shinny Go. Based on the location of the embryo (PE vs PWE), 56 DEGs were identified, 41 upregulated and 15 downregin PWE relative to PE. The DEGs included two genes (LOC100064092, FADS3) involved with fatty acid metabolism, and seven genes (RIPOR2, SMAD6, ROBO1, TENM1, SELL, ADORA2A, and AGR2) involved in cell-to-cell interaction. Based on GO, the DEGs in the pregnant group were mainly associated with cell adhesion, response to chemokines, inflammatory responses, connective tissue replacement involved in inflammatory responses, and connective tissue replacement. Additionally, there were 669 and 707 DEGs, in PE vs. NB and PWE vs. NB comparisons, respectively. The DEGs were mainly involved in cell metabolism and signaling. Moreover, there were 13 overlapping genes among the PE vs. NB and PE vs. PWE groups. There were two genes (PLIN5, LOC100064092) involved with fatty acid metabolism, one with hematopoiesis (SERPINB10), one with vascularization and development (ATOH8), one gene related to osmotic pressure (MUC5B), and one gene related to endometrial remodeling (TIMP1). In conclusion, these results suggest that the embryo initiates local maternal-embryo dialogue, embryo development and immune system regulation during the early pre-fixation phase of pregnancy. This project was supported by the John P. Hughes Endowment and the Center for Equine Health with funds provided by the State of California satellite wagering fund and contributions by private donors.

Embryo-maternal interactions revealed by phosphoproteomic analysis of endometrial organoids exposed to embryo secretome

The equine embryo remains mobile and without physical attachment to the endometrium for a prolonged period in early pregnancy. During this time, the embryo only communicates with the maternal system via secreted compounds in its immediate environment. These interactions are poorly understood, and a definitive signal for maternal recognition of pregnancy remains elusive. In this study, we sought to develop a model to examine embryo-maternal interactions at close range in vitro, demonstrating that incubation of endometrial organoids with embryo-conditioned medium results in detectable changes in the endometrial phosphoproteome. Mare endometrial organoids were derived from isolated endometrial glands of uteri obtained immediately post-mortem. Embryos were recovered by uterine lavage from Standardbred mares at day 8-9 post-ovulation, washed and pre-cultured in BSA-containing medium under oil, and cultured in protein-free medium under oil. Embryo-conditioned and control media were collected at 12 h, centrifuged to remove debris and stored at −80°C until further analysis. For co-incubation experiments, organoids were primed with 10nM estradiol (48 h), then 10nM estradiol + 1 µM progesterone (48 h). Embryo-conditioned (n=3) or control (n=3) media were added at a dilution of 1:100 in organoid medium and co-incubated for 30 minutes. Organoids were then recovered and processed to remove media and secretome components (on ice and in the presence of phosphatase inhibitors). Cell pellets were frozen at -80˚C until protein extraction. Proteins were extracted with urea-based extraction buffer, reduced,alkylated, and digested with trypsin. Phosphopeptides were isolated using titanium dioxide before LC tandem mass spectrometry (MS/MS) using a Q-Exactive Plus hybrid quadrupole-Orbitrap MS system (Thermo Fisher Scientific, Bremen, Germany). Endometrial organoids were successfully cultured in vitro and their functional mimicry of in vivo endometrium was confirmed via multiple routes including histological analysis of gland-like structures, epithelial and endometrial markers, and RNA sequencing alongside isolated endometrial glands. Phosphoproteomic mass spectrometry of endometrial organoids revealed a profile of 181 phosphopeptides mapping to 90 protein IDs. Of these, 10 phosphopeptides were decreased (log2[fold-change] < -0.8) in co-incubated organoids, while 3 were uniquely detected in secretome-exposed organoids only. Most notably, we observed a decrease in the phosphorylated peptides of PGRMC1 (progesterone receptor membrane component 1). This protein forms part of a non-classical system of progesterone action, located in the cell membrane. A change in PGRMC1 phosphorylation suggests that an alternative system of progesterone receptor activation participates in equine embryo-maternal signaling. There were also changes in phosphorylation status of chaperone proteins essential to progesterone receptor assembly (e.g., HSP90AB1). In summary, this study describes the immediate response of mare endometrial organoids to compounds released by embryos, identifying novel mechanisms possibly implicated in signaling between the embryo and maternal system.

Review: Endometrial function in pregnancy establishment in cattle.

The endometrium is fundamentally required for successful pregnancy in ruminants and species where the posthatching conceptus undergoes a protracted elongation and peri-implantation phase of pregnancy. Moreover, there are substantial waves of pregnancy loss during this pre- and peri-implantation period of pregnancy the precise source of which has not been clearly defined i.e., the maternal uterine contribution to this loss. Understanding the molecular interactions required for successful pregnancy in cattle will allow us to intervene to support pregnancy success during this vulnerable window. The endometrium contributes to most key developmental milestones of pregnancy establishment, including (1) contributing to the regulation of the oestrus cycle, (2) nourishing the preimplantation conceptus, (3) responding to the conceptus to create a more receptive microenvironment, (4) providing essential biophysical support, and (5) signalling and producing factors which affect the mother systemically. This review will summarise what we currently know about conceptus-maternal interactions as well as identify the gaps in our knowledge that could be filled with newer in vitro model approaches. These include the use of microfluidics, organ-on-a-chip devices, and bioinformatic approaches. This will help maximise food production efficiency (both meat and dairy) and decrease the environmental burden, while enhancing our understanding of the fundamental processes required for successful implantation in cattle.

088 The intricacies of conceptus-maternal interactions proposed by parthenogenetic beef cattle pregnancies

088 The intricacies of conceptus-maternal interactions proposed by parthenogenetic beef cattle pregnancies

Extracellular Vesicles Secreted by Pre-Hatching Bovine Embryos Produced In Vitro and In Vivo Alter the Expression of IFNtau-Stimulated Genes in Bovine Endometrial Cells.

The embryo-maternal interaction occurs during the early stages of embryo development and is essential for the implantation and full-term development of the embryo. In bovines, the secretion of interferon Tau (IFNT) during elongation is the main signal for pregnancy recognition, but its expression starts around the blastocyst stage. Embryos release extracellular vesicles (EVs) as an alternative mechanism of embryo-maternal communication. The aim of the study was to determine whether EVs secreted by bovine embryos during blastulation (D5-D7) could induce transcriptomic modifications, activating IFNT signaling in endometrial cells. Additionally, it aims to assess whether the EVs secreted by embryos produced in vivo (EVs-IVV) or in vitro (EVs-IVP) have different effects on the transcriptomic profiles of the endometrial cells. In vitro- and in vivo-produced bovine morulae were selected and individually cultured for 48 h to collect embryonic EVs (E-EVs) secreted during blastulation. E-EVs stained with PKH67 were added to in vitro-cultured bovine endometrial cells to assess EV internalization. The effect of EVs on the transcriptomic profile of endometrial cells was determined by RNA sequencing. EVs from both types of embryos induced several classical and non-classical IFNT-stimulated genes (ISGs) and other pathways related to endometrial function in epithelial endometrial cells. Higher numbers of differentially expressed genes (3552) were induced by EVs released by IVP embryos compared to EVs from IVV (1838). Gene ontology analysis showed that EVs-IVP/IVV induced the upregulation of the extracellular exosome pathway, the cellular response to stimulus, and the protein modification processes. This work provides evidence regarding the effect of embryo origin (in vivo or in vitro) on the early embryo-maternal interaction mediated by extracellular vesicles.

The Extracellular Vesicles Proteome of Endometrial Cells Simulating the Receptive Menstrual Phase Differs from That of Endometrial Cells Simulating the Non-Receptive Menstrual Phase.

Successful embryo implantation into a receptive endometrium requires mutual endometrial-embryo communication. Recently, the function of extracellular vehicles (EVs) in cell-to-cell interaction in embryo-maternal interactions has been investigated. We explored isolated endometrial-derived EVs, using RL95-2 cells as a model of a receptive endometrium, influenced by the menstrual cycle hormones estrogen (E2; proliferative phase), progesterone (P4; secretory phase), and estrogen plus progesterone (E2P4; the receptive phase). EV sized particles were isolated by differential centrifugation and size exclusion chromatography. Nanoparticle tracking analysis was used to examine the different concentrations and sizes of particles and EV proteomic analysis was performed using shotgun label-free mass spectrometry. Our results showed that although endometrial derived EVs were secreted in numbers independent of hormonal stimulation, EV sizes were statistically modified by it. Proteomics analysis showed that hormone treatment changes affect the endometrial EV's proteome, with proteins enhanced within the EV E2P4 group shown to be involved in different processes, such as embryo implantation, endometrial receptivity, and embryo development, supporting the concept of a communication system between the embryo and the maternal endometrium via EVs.

Understanding conceptus–maternal interactions: what tools do we need to develop?

Communication between the maternal endometrium and developing embryo/conceptus is critical to support successful pregnancy to term. Studying the peri-implantation period of pregnancy is critical as this is when most pregnancy loss occurs in cattle. Our current understanding of these interactions is limited, due to the lack of appropriate in vitro models to assess these interactions. The endometrium is a complex and heterogeneous tissue that is regulated in a transcriptional and translational manner throughout the oestrous cycle. While there are in vitro models to study endometrial function, they are static and 2D in nature or explant models and are limited in how well they recapitulate the in vivo endometrium. Recent developments in organoid systems, microfluidic approaches, extracellular matrix biology, and in silico approaches provide a new opportunity to develop in vitro systems that better model the in vivo scenario. This will allow us to investigate in a more high-throughput manner the fundamental molecular interactions that are required for successful pregnancy in cattle.

Immune Tolerance of Embryo Implantation and Pregnancy: The Role of Human Decidual Stromal Cell- and Embryonic-Derived Extracellular Vesicles.

Embryo-endometrial communication plays a critical role in embryo implantation and the establishment of a successful pregnancy. Successful pregnancy outcomes involve maternal immune modulation during embryo implantation. The endometrium is usually primed and immunomodulated by steroid hormones and embryo signals for subsequent embryo implantation and the maintenance of pregnancy. The roles of extracellular vesicles (EVs) and microRNAs for the embryo-maternal interactions have been elucidated recently. New evidence shows that endometrial EVs and trophectoderm-originated EV cargo, including microRNAs, proteins, and lipids in the physiological microenvironment, regulate maternal immunomodulation for embryo implantation and subsequent pregnancy. On the other hand, trophoblast-derived EVs also control the cross-communication between the trophoblasts and immune cells. The exploration of EV functions and mechanisms in the processes of embryo implantation and pregnancy will shed light on a practical tool for the diagnostic or therapeutic approaches to reproductive medicine and infertility.

Ruminant conceptus-maternal interactions: interferon-tau and beyond.

Embryonic or fetal loss in cattle is associated with problems that occur during oocyte maturation, early embryonic development, conceptus elongation, maternal recognition of pregnancy (MRP), and/or placental attachment and implantation. Many of these problems manifest as inadequate or asynchronous communication between the developing conceptus and endometrium, resulting in pregnancy failure. This review will provide an overview of how various conceptus-endometrial paracrine signaling systems control the fate of early pregnancy in cattle and other ruminants. We begin by summarizing the actions of interferon-tau, the classic MRP signal in ruminates, and then explore how other secretory factors derived from either the conceptus or endometrium influence establishment and maintenance of pregnancy. Insight into how the endometrium responds to male vs. female conceptuses or conceptuses produced by in vitro methods will also be described. Specific focus will be placed on describing how "omic" technologies and other cutting-edge techniques have assisted with identifying novel conceptus and/or endometrial factors and their functions. Recent findings indicate that the endometrial transcriptome and histotroph are altered by conceptus sex, quality, and origin, suggesting that the endometrium is a sensor of conceptus biochemistry. Although the endometrium has a certain level of flexibility in terms of conceptus-maternal interactions, this interplay is not sufficient to retain some pregnancies. However, new information inspires us to learn more and will help develop technologies that mitigate early embryonic loss and reproductive failure in ruminants and other animals.

Extracellular Vesicle-Associated MicroRNA-138-5p Regulates Embryo Implantation and Early Pregnancy by Adjusting GPR124.

Functional embryo–maternal interactions occur during the embryo implantation and placentation. Extracellular vesicles with microRNA (miR) between cells have been considered of critical importance for embryo implantation and the programming of human pregnancy. MiR-138-5p functions as the transcriptional regulator of G protein-coupled receptor 124 (GPR124). However, the signaling pathway of miR138-5p- and GPR124-adjusted NLRP3 inflammasome activation remains unclear. In this study, we examine the roles of the miR138-5p and GPR124-regulated inflammasome in embryo implantation and early pregnancy. Human decidual stromal cells were isolated from the abortus tissue and collected by curettage from missed abortion patients and normal pregnant women at 6- to 12-week gestation, after informed consent. Isolated extracellular vesicles from decidua and decidual stromal cells were confirmed by transmission electron microscopy (TEM). Next-Generation Sequencing (NGS) and microarray were performed for miR analysis. The predicated target genes of the differentially expressed miR were analyzed to identify the target genes and their pathway. We demonstrated the down-regulation of miR-138-5p and the overexpression of GPR124 in spontaneous miscarriage compared to normal pregnancy. We also showed the excessive activation of the NLRP3 inflammasome in spontaneous miscarriage compared to normal pregnancy. Here, we newly demonstrate that the miR-138-5p and GPR124-adjusted NLRP3 inflammasome were expressed in extracellular vesicles derived from decidua and decidual stromal cells, indicating that the miR-138-5p, GPR124 and NLRP3 (NACHT, LRR, and PYD domains-containing protein 3) inflammasome have a potential modulatory role on the decidual programming and placentation of human pregnancy. Our findings represent a new concept regarding the role of extracellular vesicles, miR-138-5p, GPR124, and the NLRP3 inflammasome in normal early pregnancy and spontaneous miscarriage.

ITRAQ-based quantitative proteomic analysis of porcine uterine fluid during pre-implantation period of pregnancy

Proteins in the uterine luminal fluid are essential for embryo development and regulation of embryo-maternal interaction in porcine. However, little is known about the profile of proteins in uterine luminal fluid of porcine during the pre-implantation period. The present study, applied iTRAQ proteomics technology to identify and analyze uterine luminal fluid proteins on day 9 of estrus cycle and days 9, 12, and 15 of pregnancy. A total of 964 proteins were identified in the present study. Principal component analysis and hierarchical clustering revealed the dynamic developmental characteristics of embryo implantation, which indicated significant differences on day 12 or 15 of pregnancy. In addition, further analysis conducted in the present study identified 279 differentially abundance proteins among the three groups, five clusters were generated using SOTA clustering to examine changes in of the differentially abundant proteins. Results of the current study also found that the proteins in the cluster are involved in some important processes such as regulation of low-density lipoproteins and regulation of TGF-β secretion. Notably, it was found that regulation of TGF-β is essential for porcine embryonic morphological transformation. Furthermore, proteins that play vital roles in implantation, such as CTSC, CTSB, and ACP5 were identified through protein-protein interaction network. Therefore, these findings of the present study provide a basis for understanding embryo development mechanisms and implantation in pigs. SignificanceProteins are directly acting molecules for the functioning of organisms. It is important to study the regulation mechanism of embryo implantation from the perspective of protein function. In the current study, iTRAQ proteomics technology was employed to identify and explore uterine luminal fluid proteins on day 9 of estrus cycle and days 9, 12, and 15 of pregnancy. The findings provide novel insights into the process of porcine early embryo implantation. Furthermore, it is also helpful to clarify the mechanism of embryonic development and implantation.

Quantitative proteomic analysis of serum-purified exosomes identifies putative pre-eclampsia-associated biomarkers

BackgroundThe high incidence of pre-eclampsia, which affects 2–7% of all pregnancies, remains a major health concern. Detection of pre-eclampsia before the appearance of clinical symptoms is essential to allow early intervention, and would benefit from identification of plasma/serum biomarkers to help guide diagnosis and treatment. Liquid biopsy has emerged as a promising source of protein biomarkers that circumvents some of the inherent challenges of proteome-wide analysis of plasma/serum. In this respect, purified exosomes have the added benefit of being carriers of intercellular communication both in physiological and pathological conditions.MethodsWe compared the protein complement of purified exosomes from three different collections of control and pre-eclamptic serum samples, obtained at the end of the second trimester of pregnancy and at delivery. We employed shotgun label-free proteomics to investigate differential protein expression, which was then validated by targeted proteomics.ResultsWe developed a purification method that yielded highly enriched exosome preparations. The presence of specific pregnancy protein markers suggested that a significant proportion of purified exosomes derived from tissues related to pregnancy. Quantitative proteomic analyses allowed us to identify 10, 114 and 98 differentially-regulated proteins in the three sample collections, with a high degree of concordance. Functional analysis suggested that these proteins participate in biological processes related to pre-eclampsia, including angiogenesis, inflammation and cell migration. The differential abundance of 66 proteins was validated by targeted proteomics. Finally, we studied the impact of the pre-eclampsia-associated exosomes in the proteome using an in vitro cellular model.ConclusionsWe have identified and validated differential exosomal proteins in liquid biopsy of pregnant women that open new possibilities for early detection of pre-eclampsia. Additionally, the functional impact of the proteome composition of purified pre-eclamptic exosomes in target cells provides new information to better understand changes in embryo-maternal interactions and, consequently, the pathogenesis of this disease.

Role of reproductive fluids and extracellular vesicles in embryo&#x2013;maternal interaction during early pregnancy in cattle.

The coordinated interaction between the developing embryo and the maternal reproductive tract is essential for the establishment and maintenance of pregnancy in mammals. An early cross-talk is established between the oviduct/uterus and the gametes and embryo. This dialogue will shape the microenvironment in which gamete transport, fertilisation, and early embryonic development occur. Due to the small size of the gametes and the early embryo relative to the volume of the oviductal and uterine lumina, collection of tissue and fluid adjacent to these cells is challenging in cattle. Thus, the combination of in vivo and in vitro models seems to be the most appropriate approach to better understand this fine dialogue. In this respect, the aim of this review is to summarise the recent findings in relation to gamete/embryo-maternal interaction during the pre-elongation period.