microRNA-based signatures obtained from endometrial fluid identify implantative endometrium

Multi-omics analysis of uterine fluid extracellular vesicles reveals a resemblance with endometrial tissue across the menstrual cycle: biological and translational insights

STUDY QUESTION

Does the molecular composition of uterine fluid extracellular vesicles (UF-EVs) reflect endometrial tissue changes across the menstrual cycle?

SUMMARY ANSWER

Concordance between endometrial tissue and UF-EVs exists on miRNA and mRNA levels along the menstrual cycle phases and UF-EV surface proteomic signatures suggest EVs originate from several major endometrial cell populations.

WHAT IS KNOWN ALREADY

The clinical value of endometrial receptivity testing is restricted by invasiveness and the use of only one omics level of input. There is promising evidence that UF-EVs can reflect changes in mid-secretory endometrium, highlighting the potential to establish endometrial receptivity testing right before embryo transfer. However, the dynamic changes of UF-EVs molecular cargo have not been directly compared to endometrial tissue on multiple omics levels.

STUDY DESIGN SIZE DURATION

This cross-sectional study included fertile women from four menstrual cycle phases: proliferative and early-, mid-, and late-secretory phases. In total, 26 paired samples of UF and endometrial tissue were collected. mRNA and miRNA were sequenced, and differential analysis was performed on consecutive phases. UF-EVs were profiled for various protein surface markers associated with different cell types. EVs from epithelial endometrial organoid-conditioned culture media were used as a reference of pure epithelial endometrial EVs.

PARTICIPANTS/MATERIALS SETTING METHODS

Paired UF and endometrial tissue samples were collected from 26 fertile, reproductive-age women. EV isolation from UF was validated using electron microscopy and western blotting, and particle numbers were measured by nanoparticle tracking analysis. The transcriptome and miRNome of UF-EVs and endometrial tissue were sequenced, and differential expression analysis was conducted on consecutive phases of the menstrual cycle. Bead-based EV flow cytometry targeting 37 surface protein markers was used to characterize EVs from UF and endometrial organoids.

MAIN RESULTS AND THE ROLE OF CHANCE

Surface proteome analysis revealed that UF-EVs from the mid-secretory phase had significantly increased expression of natural killer cell marker CD56 (P < 0.005), pan-leukocyte marker CD45 (P < 0.005), pan-T-cell marker CD3 (P < 0.005), and coagulation-related protein CD142 (P < 0.005) compared to those from the proliferative phase, whereas markers associated with endometrial epithelial cells (CD29, CD133, and CD326) did not significantly change across the menstrual cycle. Transcriptomic analysis highlighted differential expression of histone and metallothionein genes that correlated between paired UF-EVs and endometrial tissues in each tested menstrual cycle phase. Principal component analysis of miRNomes of paired UF-EVs and endometrial tissue samples resulted in similar clustering patterns, where mid- and late-secretory samples clustered closely, and proliferative and early-secretory phase samples clustered separately. Half of the differentially expressed miRNAs in each phase in UF-EVs were also differentially expressed in the endometrium. Importantly, nine mid-secretory phase UF-EV DE miRNAs were identified, five of which were common between UF-EVs and endometrial biopsies, including hsa-miR-30d-5p and hsa-miR-200b-3p, both of which were previously implicated in implantation. Notably, three of the nine miRNAs, hsa-miR-200b-3p, hsa-miR-141-3p, and hsa-miR-200a-3p, were predicted to regulate mRNAs in the endometrial tissue and the pre-implantation embryo trophectoderm.

LARGE SCALE DATA

N/A.

LIMITATIONS REASONS FOR CAUTION

The clinical dating of the menstrual cycle phase is based on the first day of menstruation and the time of the LH peak, which does not exclude the possibility that the expected endometrial phase was not reached. The wider limitation of our study is the lack of standardized procedures for collecting UF samples in gynaecological practice, which could challenge the replication of our findings.

WIDER IMPLICATIONS OF THE FINDINGS

Evidence that UF-EVs reflect endometrial phases of menstrual cycle supports the use of UF-EVs in endometrial receptivity testing. Additionally, further studies of UF-EVs in endometrial pathologies could be beneficial for diagnostics, considering that more invasive tissue biopsies only reflect the biopsy site and not the full endometrium.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by the European Regional Development Fund Enterprise Estonia's Applied Research Program under the grant agreement number 2014-2020.4.02.21-0398 (EVREM), the Estonian Research Council (grant nos. PRG1076 and PSG1082), the Horizon Europe NESTOR grant (grant no. 101120075) of the European Commission, the Swedish Research Council (grant no. 2024-02530), the Novo Nordisk Fonden (grant no. NNF24OC0092384), and the National Recovery and Resilience Plan of the Republic of Bulgaria, project number BG-RRP-2.004-0001-C01. A.S.L. received funding from the Becas Fundación Ramón Areces para Estudios Postdoctorales. All the authors declare no conflict of interest.

Investigating the Imperative Role of microRNAs Expression in Human Embryo Implantation: A Narrative Review Based on Recent Evidence

BACKGROUND/OBJECTIVES

Embryo implantation is a highly complex process that requires the precise regulation of numerous molecules to be orchestrated successfully. Micro RNAs (miRNAs) are small non-coding RNAs that regulate gene expression and play a crucial role in the regulation of embryo implantation. This article aims to summarize the key findings of the literature regarding the role of miRNAs in human embryo implantation, emphasizing their involvement in critical stages such as decidualization, endometrial receptivity and trophoblast adhesion.

METHODS

This review includes primary research articles from the past decade. The studies utilize a range of experimental methodologies, including gene expression analysis and in vitro studies.

RESULTS

MicroRNAs, like miR-320a, miR-149, and miR30d secreted by preimplantation embryos and blastocysts significantly influence endometrial receptivity by promoting essential cellular processes, such as cell migration and trophoblast cell attachment, while others-miR17-5p, miR-193-3p, miR-372, and miR-542-3p-secreted from the endometrium regulate the decidualization phase. During the apposition and adhesion phases, miRNAs play a complex role by promoting, for example, miR-23b-3p, and inhibiting-as do miR-29c and miR-519d-3p-important biological pathways of these stages. During invasion, miR-26a-5p and miR-125-5p modulate important genes.

CONCLUSIONS

This review underscores the critical impact of miRNAs in the regulation of embryo implantation and early pregnancy. The ability of miRNAs to modulate gene expression at various stages of reproduction presents promising therapeutic avenues for improving assisted reproductive technologies outcomes and addressing infertility. Further research into miRNA-based diagnostic tools and therapeutic strategies is essential to enhance our understanding of their role in reproductive health and to exploit their potential for clinical applications.

Updating Research on Extracellular Vesicles of the Male Reproductive Tract in Farm Animals: A Systematic Review

This systematic review examined research studies on extracellular vesicles (EVs) of the male reproductive tract in livestock species to summarize the research topics and methodologies used, key findings, and future directions. PubMed and Scopus were searched for time ranges up to 1 September 2024, and 1383 articles were identified. The application of screening and eligibility criteria resulted in the selection of 79 articles focusing on male reproductive EVs in livestock. Porcine and bovine male reproductive EVs were the most studied. A variety of EV isolation techniques were used, with ultracentrifugation being the most common. Characterization of male reproductive EVs in livestock was a weak point, with only 24.05% of the articles characterizing EVs according to MISEV guidelines. Inadequate characterization of EVs compromises the reliability of results. The results of 19 articles that provided a good characterization of EVs showed that male reproductive EVs from livestock species are phenotypically and compositionally heterogeneous. These papers also showed that these EVs would be involved in the regulation of sperm functionality. Research on male reproductive EVs in livestock species remains scarce, and further research is needed, which should include appropriate characterization of EVs and aim to find efficient methods to isolate them and assess their involvement in the functionality of spermatozoa and the cells of the female genital tract.

ΜicroRNA (miRNA) Variants in Male Infertility: Insights from Whole-Genome Sequencing

BACKGROUND/OBJECTIVES

Male infertility is a complex condition with various underlying genetic factors. microRNAs (miRNAs) play a crucial role in gene regulation, and their disruption can significantly impact fertility. This study aimed to identify variants within miRNA genes and elucidate their impact on male infertility.

METHODS

Whole genome sequencing was performed on blood samples from men with asthenozoospermia, oligozoospermia, and teratozoospermia, compared to normozoospermic controls. The analysis revealed a significant number of unique variants in each infertile group. We subsequently focused on variants in miRNA regions, followed by an in silico analysis to investigate the role of the identified variants and miRNAs in male infertility.

RESULTS

Focused analysis on miRNA genes identified 19 exclusive variants in teratozoospermic men, 24 in asthenozoospermic, and 27 in oligozoospermic, all mapping to pre-miRNAs or mature miRNAs. Functional analyses using Gene Ontology (GO) and KEGG pathways highlighted key biological processes and pathways disrupted by these variants and miRNA-mRNA interactions, including transcription regulation, signaling, and cancer-related pathways. Furthermore, six variants (rs17797090, rs1844035, rs7210937, rs451887, rs12233076, and rs6787734) were common across the infertile groups, suggesting their importance in male infertility or their potential as biomarkers. Common variants were also validated in another clinically relevant group of men. Some miRNAs with identified variants, such as hsa-miR-449b and hsa-miR-296, have been previously implicated in male infertility and exhibit differential expression between fertile and infertile men, according to the literature, too.

CONCLUSION

These results provide new insights into the genetic basis of male infertility and open avenues for future research and therapeutic interventions.

Preliminary construction of non-coding RNAs and ceRNA regulatory networks mediated by exosomes in porcine follicular fluid

BACKGROUND

Follicles are fundamental units of the ovary, regulated intricately during development. Exosomes and ovarian granulosa cells (OGCs) play pivotal roles in follicular development, yet the regulatory mechanisms governing exosomes remain elusive.

RESULTS

High-throughput sequencing was employed to evaluate the complete transcript expression profiles of six samples (three porcine ovarian granulosa cells-exosome co-culture samples (GCE) and three porcine ovarian granulosa cells (POGCs) samples). Differential expression analysis revealed 924 lncRNAs, 35 circRNAs, 49 miRNAs, and 9823 mRNAs in the GCE group. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses indicated enrichment of differentially expressed transcripts in pathways related to cell proliferation and apoptosis. Furthermore, a ceRNA regulatory network comprising 43 lncRNAs, 6 circRNAs, 11 miRNAs, and 126 mRNAs was constructed based on intergene co-expression correlations. Seven miRNAs associated with cell proliferation and apoptosis regulation were identified within this network, encompassing 92 subnet pairs as candidate genes for further exploration of exosome regulatory mechanisms. Additionally, preliminary verification at the cellular level demonstrated that exosomal miR-200b enhances the viability of POGCs.

CONCLUSIONS

Transcriptome analysis unveiled a pivotal candidate ceRNA network potentially implicated in exosome-mediated regulation of granulosa cell proliferation and apoptosis, thereby influencing porcine follicular development. These findings offer insights into the molecular mechanisms of follicular fluid exosome regulation, encompassing both coding and non-coding RNA perspectives.

Uterine fluid microRNAs in repeated implantation failure

Recurrent implantation failure (RIF) is a significant obstacle in assisted reproductive procedures, primarily because of compromised receptivity. As such, there is a need for a dependable and accurate clinical test to evaluate endometrial receptiveness, particularly during embryo transfer. MicroRNAs (miRNAs) have diverse functions in the processes of implantation and pregnancy. Dysregulation of miRNAs results in reproductive diseases such as recurrent implantation failure (RIF). The endometrium secretes several microRNAs (miRNAs) during the implantation period, which could potentially indicate whether the endometrium is suitable for in vitro fertilization (IVF). The goal of this review is to examine endometrial miRNAs as noninvasive biomarkers that successfully predict endometrium receptivity in RIF.

Extracellular vesicles-coupled miRNAs from oviduct and uterus modulate signaling pathways related to lipid metabolism and bovine early embryo development

BACKGROUND

Extracellular vesicles (EVs) present in oviductal (OF) and uterine fluid (UF) have been shown to enhance bovine embryo quality during in vitro culture by reducing lipid contents and modulating lipid metabolism-related genes (LMGs), while also influencing cell proliferation, suggesting their involvement on the regulation of different biological pathways. The regulation of signaling pathways related to cell differentiation, proliferation, and metabolism is crucial for early embryo development and can determine the success or failure of the pregnancy. Bioactive molecules within EVs in maternal reproductive fluids, such as microRNAs (miRNAs), may contribute to this regulatory process as they modulate gene expression through post-transcriptional mechanisms.

RESULTS

From the 20 differentially expressed miRNAs, 19 up-regulated in UF-EVs (bta-miR-134, bta-miR-151-3p, bta-miR-155, bta-miR-188, bta-miR-181b, bta-miR-181d, bta-miR-224, bta-miR-23b-3p, bta-miR-24-3p, bta-miR-27a-3p, bta-miR-29a, bta-miR-324, bta-miR-326, bta-miR-345-3p, bta-miR-410, bta-miR-652, bta-miR-677, bta-miR-873 and bta-miR-708) and one (bta-miR-148b) in OF-EVs. These miRNAs were predicted to modulate several pathways such as Wnt, Hippo, MAPK, and lipid metabolism and degradation. Differences in miRNAs found in OF-EVs from the early luteal phase and UF-EVs from mid-luteal phase may reflect different environments to meet the changing needs of the embryo. Additionally, miRNAs may be involved, particularly in the uterus, in the regulation of embryo lipid metabolism, immune system, and implantation. This study evaluated miRNA cargo in OF-EVs from the early luteal phase and UF-EVs from the mid-luteal phase, coinciding with embryo transit within oviduct and uterus in vivo, and its possible influence on LMGs and signaling pathways crucial for early embryo development. A total of 333 miRNAs were detected, with 11 exclusive to OF, 59 to UF, and 263 were common between both groups.

CONCLUSIONS

Our study suggests that miRNAs within OF- and UF-EVs could modulate bovine embryo development and quality, providing insights into the intricate maternal-embryonic communication that might be involved in modulating lipid metabolism, immune response, and implantation during early pregnancy.

Development of a Predictive Model for Optimization of Embryo Transfer Timing Using Blood-Based microRNA Expression Profile

MicroRNAs (miRNAs) can regulate the expression of genes involved in the establishment of the window of implantation (WOI) in the endometrium. Recent studies indicated that cell-free miRNAs in uterine fluid and blood samples could act as alternative and non-invasive sample types for endometrial receptivity analysis. In this study, we attempt to systematically evaluate whether the expression levels of cell-free microRNAs in blood samples could be used as non-invasive biomarkers for assessing endometrial receptivity status. We profiled the miRNA expression levels of 111 blood samples using next-generation sequencing to establish a predictive model for the assessment of endometrial receptivity status. This model was validated with an independent dataset (n = 73). The overall accuracy is 95.9%. Specifically, we achieved accuracies of 95.9%, 95.9%, and 100.0% for the pre-receptive group, the receptive group, and the post-respective group, respectively. Additionally, we identified a set of differentially expressed miRNAs between different endometrial receptivity statuses using the following criteria: p-value < 0.05 and fold change greater than 1.5 or less than -1.5. In conclusion, the expression levels of cell-free miRNAs in blood samples can be utilized in a non-invasive manner to distinguish different endometrial receptivity statuses.

Uterine Fluid Extracellular Vesicles Proteome Is Altered During the Estrous Cycle

Uterine environment is tightly and finely regulated via various signaling pathways mediated through endocrine, exocrine, autocrine, juxtacrine, and paracrine mechanisms. In utero signaling processes are paramount for normal and abnormal physiology which involves cell to cell, cells to gametes, cells to embryo, and even interkingdom communications due to presence of uterine microbiota. Extracellular vesicles (EVs) in the uterine fluid (UF) and their cargo components are known to be mediators of in utero signaling and communications. Interestingly, the changes in UF-EV proteome during the bovine estrous cycle and the effects of these differentially enriched proteins on embryo development are yet to be fully discovered. In this study, shotgun quantitative proteomics-based mass spectrometry was employed to compare UF-EV proteomes at day 0, 7, and 16 of the estrous cycle to understand the estrous cycle-dependent dynamics. Furthermore, different phase UF-EVs were supplemented in embryo cultures to evaluate their impact on embryo development. One hundred fifty-nine UF-EV proteins were differentially enriched at different time points indicating the UF-EV proteome is cycle-dependent. Overall, many identified pathways are important for normal uterine functions, early embryo development, and its nutritional needs, such as antioxidant activity, cell morphology and cycle, cellular homeostasis, cell adhesion, and carbohydrate metabolic process. Furthermore, the luteal phase UF-EVs supplementation increased in vitro blastocyst rates from 25.0 ± 5.9% to 41.0 ± 4.0% (p ≤ 0.05). Our findings highlight the importance of bovine UF-EV in uterine communications throughout the estrous cycle. Interestingly, comparison of hormone-synchronized EV proteomes to natural cycle UF-EVs indicated shift of signaling. Finally, UF-EVs can be used to improve embryo production in vitro.

Current knowledge on the role of extracellular vesicles in endometrial receptivity

Endometrial receptivity has been widely understood as the capacity of the endometrium to receive implantable embryos. The establishment of endometrial receptivity involves multiple biological processes including decidualization, tissue remodeling, angiogenesis, immune regulation, and oxidative metabolism. Extracellular vesicles (EVs) are lipid-bilayer-membrane nanosized vesicles mediating cell-to-cell communication. Recently, EVs and their cargo have been proven as functional factors in the establishment of endometrial receptivity. In this review, we comprehensively summarized the alteration of endometrium/embryo-derived EVs during the receptive phase and retrospected the current findings which revealed the pivotal role and potential mechanism of EVs to promote successful implantation. Furthermore, we highlight the potentiality and limitations of EVs being translated into clinical applications such as biomarkers of endometrial receptivity or reproductive therapeutic mediators, and point out the direction for further research.

Current perspectives on endometrial receptivity: A comprehensive overview of etiology and treatment

Recurrent implantation failure (RIF) remains a challenging problem in assisted reproductive technology (ART). Further insights into uterine abnormalities that can disturb embryo implantation should be obtained. This review provides an overview of the effects of organic and non-organic uterine disorders on endometrial receptivity. The results suggest that various uterine pathologies can lead to defective embryo implantation via multiple mechanisms. In particular, uterine adenomyosis dysregulates molecular and cellular interactions that are vital for successful embryo implantation with a background of chronic inflammation, which may be alleviated by pretreatment with a gonadotropin-releasing hormone agonist. Uterine myomas can cause endometrial deformation and adverse alterations in uterine contractility. Nonetheless, the effectiveness of myomectomy remains debated, and endometrial polyp removal may be considered, particularly in patients with RIF. Chronic endometritis abrogates the appropriate uterine immunological environment critical for embryo implantation. Abnormal endometrial microbiota have been suggested to influence endometrial receptivity; however, supporting evidence is currently scarce. Platelet-rich plasma therapy may be a potential treatment for thin endometria; nevertheless, further validation is required. Endometrial receptivity analysis can detect dysregulation of the window of implantation, and new non-invasive methods for predicting endometrial receptivity have recently been proposed. However, numerous issues still need to be fully clarified. Further clinical and basic studies are necessary to investigate the pathophysiology of defective endometrial receptivity and identify optimal treatments for patients undergoing ART, especially those with RIF.

Comparison of the Administration of 150 or 75 IU of Recombinant LH in Agonist ICSI Cycles Stimulated with Recombinant FSH in Women Aged 35-39: A Comparative Study

Background

The purpose of the study was to assess whether the coadministration of 150 IU of recombinant LH instead of 75 IU in women aged 35-39 improves the results in agonist ICSI cycles stimulated with 300 IU of recombinant FSH.

Methods

In this study, two ovarian stimulation protocols coexisted which were identical except in the administered dose of recombinant LH, for which some patients received 150 IU (n=231) and some received 75 IU (n=216). Both groups received 300 IU of recombinant FSH. Gonadotropins were reimbursed by the National Health System. Statistical analysis was performed by Student's t test, χ2, and ANCOVA. Significance level was established at p=0.05.

Results

The number of retrieved oocytes was slightly higher in the 300/150 group (9.06±5.53 vs. 8.61±5.11), but the differences were not significant. Results were similar with the number of metaphase II oocytes (7.18±4.86 vs. 6.72±4.72) and the number of fertilized oocytes (4.64±3.2 vs. 4.23±2.72). The per-transfer clinical pregnancy rates exhibited close similarity between both groups (32.84% vs. 32.46%), as did the per-transfer live birth rates (29.90% vs. 30.37%) and the implantation rate. The rate of hyperstimulation syndrome (OHSS) as well as the rate of cancellation due to OHHS risk was similar in both groups. There was also no difference in the miscarriage rate. When results were expressed by per started cycle or by oocyte pick-up, the results remained very similar in both groups.

Conclusion

In women aged 35-39 undergoing ovarian stimulation with recombinant FSH in agonist cycles, the coadministration of 75 or 150 UI of recombinant LH did not influence pregnancy rates. However, a slight increase in the number of retrieved oocytes should not be disregarded.

Natural killer cell subsets in endometrial fluid: a pilot study of their association with the endometrial cycle and reproductive parameters

PURPOSE

To investigate if there are natural killer (NK) cells in endometrial fluid (EF) and their relationship with the endometrial cycle and reproductive parameters.

METHODS

The population under study consisted of 43 women aged 18-40 undergoing infertility workup at our University Hospital in 2021-2022. The EF samples were obtained at the first visit to our unit, on occasion of the mock embryo transfer. The day of the cycle was considered only in cycles of 27-29 days. An immunophenotype study of NK in EF was performed by flow cytometry analysis. In a subgroup of women, on the same day, NK was studied in EF and peripheral blood.

RESULTS

Our study is the first to evidence NK cells in EF. None of the NK cells observed corresponded to a mature peripheral blood NK cell population (stages 4-5), and neither endometrial nor decidual uNK cells were detected. Nevertheless, we found 2 patient groups with an NK cell subset with a higher expression of CD16+, which could belong to an intermediate or transient stage between the uNK and pbNK NK cell population in the EF. We found that CD16 was significantly increased in the mid-late luteal phase and its correlation with the day of the cycle. The NK immunophenotype was different in EF and peripheral blood.

CONCLUSION

We described a new component of the EF, the NK cells, whose CD16 activity is closely correlated with the day of the cycle. These cells could play a role in implantation/implantation failure.

Dynamic peripheral blood microRNA expression landscape during the peri-implantation stage in women with successful pregnancy achieved by single frozen-thawed blastocyst transfer

STUDY QUESTION

What are the dynamic expression features of plasma microRNAs (miRNAs) during the peri-implantation period in women with successful pregnancy via single frozen-thawed blastocyst transfer?

SUMMARY ANSWER

There is a significant change in the plasma miRNA expression profile before and after blastocyst transfer, during the window of implantation.

WHAT IS KNOWN ALREADY

The expression of miRNAs in peripheral blood has indicative functions during the peri-implantation period. Nevertheless, the dynamic expression profile of circulating miRNAs during the peri-implantation stage in women with a successful pregnancy has not been studied.

STUDY DESIGN SIZE DURATION

Seventy-six women treated for infertility with a single frozen-thawed blastocyst transfer in a natural cycle were included in this study. Among them, 57 women had implantation success and a live birth, while 19 patients experienced implantation failure. Peripheral blood samples were collected at five different time points throughout the peri-implantation period, including D0 (ovulation day), D3, D5, D7, and D9 in this cycle of embryo transfer. The plasma miRNAs in women with blastocyst transfer were isolated, sequenced, and analyzed.

PARTICIPANTS/MATERIALS SETTING METHODS

Peripheral blood samples were collected in EDTA tubes and stored at -80°C until further use. miRNAs were isolated from blood, cDNA libraries were constructed, and the resulting sequences were mapped to the human genome. The plasma miRNAs were initially analyzed in a screening cohort (n = 34) with successful pregnancy. Trajectory analysis, including a global test and pairwise comparisons, was performed to detect dynamic differentially expressed (DE) miRNAs. Fuzzy c-means clustering was conducted for all dynamic DE miRNAs. The correlation between DE miRNAs and clinical characteristics of patients was investigated using a linear mixed model. Target genes of the miRNAs were predicted, and functional annotation analysis was performed. The expression of DE miRNAs was also identified in a validation set consisting of women with successful (n = 23) and unsuccessful (n = 19) pregnancies.

MAIN RESULTS AND THE ROLE OF CHANCE

Following small RNA sequencing, a total of 2656 miRNAs were determined as valid read values. After trajectory analysis, 26 DE miRNAs (false discovery rate < 0.05) were identified by the global test, while pairwise comparisons in addition identified 20 DE miRNAs. A total of seven distinct clusters representing different temporal patterns of miRNA expression were discovered. Nineteen DE miRNAs were further identified to be associated with at least one clinical trait. Endometrium thickness and progesterone level showed a correlation with multiple DE miRNAs (including two of the same miRNAs, hsa-miR-1-3p and hsa-miR-6741-3p). Moreover, the 19 DE miRNAs were predicted to have 403 gene targets, and there were 51 (12.7%) predicted genes likely involved in both decidualization and embryo implantation. Functional annotation for predicted targets of those clinically related DE miRNAs suggested the involvement of vascular endothelial growth factor and Wnt signaling pathways, as well as responses to hormones, immune responses, and cell adhesion-related signaling pathways during the peri-implantation stage.

LARGE SCALE DATA

The raw miRNA sequence data reported in this article have been deposited in the Genome Sequence Archive (GSA-Human: HRA005227) and are publicly accessible at https://ngdc.cncb.ac.cn/gsa-human/browse/HRA005227.

LIMITATIONS REASONS FOR CAUTION

Although the RNA sequencing results revealed the global dynamic changes of miRNA expression, further experiments examining the clinical significance of the identified DE miRNAs in embryo implantation outcome and the relevant regulatory mechanisms involved are warranted.

WIDER IMPLICATIONS OF THE FINDINGS

Understanding the dynamic landscape of the miRNA transcriptome could shed light on the physiological mechanisms involved from ovulation to the post-implantation stage, as well as identifying biomarkers that characterize stage-related biological process.

STUDY FUNDING/COMPETING INTERESTS

The study was funded by the Major clinical research project of Tangdu Hospital (2021LCYJ004) and the Discipline Platform Improvement Plan of Tangdu Hospital (2020XKPT003). The funders had no influence on the study design, data collection, and analysis, decision to publish, or preparation of the article. There are no conflicts of interest to declare.

Identification and characterization of circRNAs in peri-implantation endometrium between Yorkshire and Erhualian pigs

BACKGROUND

One of the most critical periods for the loss of pig embryos is the 12th day of gestation when implantation begins. Recent studies have shown that non-coding RNAs (ncRNAs) play important regulatory roles during pregnancy. Circular RNAs (circRNAs) are a kind of ubiquitously expressed ncRNAs that can directly regulate the binding proteins or regulate the expression of target genes by adsorbing micro RNAs (miRNA).

RESULTS

We used the Illumina Novaseq6,000 technology to analyze the circRNA expression profile in the endometrium of three Erhualian (EH12) and three Yorkshire (YK12) pigs on day 12 of gestation. Overall, a total of 22,108 circRNAs were identified. Of these, 4051 circRNAs were specific to EH12 and 5889 circRNAs were specific to YK12, indicating a high level of breed specificity. Further analysis showed that there were 641 significant differentially expressed circRNAs (SDEcircRNAs) in EH12 compared with YK12 (FDR < 0.05). Functional enrichment of differential circRNA host genes revealed many pathways and genes associated with reproduction and regulation of embryo development. Network analysis of circRNA-miRNA interactions further supported the idea that circRNAs act as sponges for miRNAs to regulate gene expression. The prediction of differential circRNA binding proteins further explored the potential regulatory pathways of circRNAs. Analysis of SDEcircRNAs suggested a possible reason for the difference in embryo survival between the two breeds at the peri-implantation stage.

CONCLUSIONS

Together, these data suggest that circRNAs are abundantly expressed in the endometrium during the peri-implantation period in pigs and are important regulators of related genes. The results of this study will help to further understand the differences in molecular pathways between the two breeds during the critical implantation period of pregnancy, and will help to provide insight into the molecular mechanisms that contribute to the establishment of pregnancy and embryo loss in pigs.

Identification of Endometrial Cancer-Specific microRNA Biomarkers in Endometrial Fluid

Abnormal uterine bleeding is a common benign gynecological complaint and is also the most common symptom of endometrial cancer (EC). Although many microRNAs have been reported in endometrial carcinoma, most of them were identified from tumor tissues obtained at surgery or from cell lines cultured in laboratories. The objective of this study was to develop a method to detect EC-specific microRNA biomarkers from liquid biopsy samples to improve the early diagnosis of EC in women. Endometrial fluid samples were collected during patient-scheduled in-office visits or in the operating room prior to surgery using the same technique performed for saline infusion sonohysterography (SIS). The total RNA was extracted from the endometrial fluid specimens, followed by quantification, reverse transcription, and real-time PCR arrays. The study was conducted in two phases: exploratory phase I and validation phase II. In total, endometrial fluid samples from 82 patients were collected and processed, with 60 matched non-cancer versus endometrial carcinoma patients used in phase I and 22 in phase II. The 14 microRNA biomarkers, out of 84 miRNA candidates, with the greatest variation in expression from phase I, were selected to enter phase II validation and statistical analysis. Among them, three microRNAs had a consistent and substantial fold-change in upregulation (miR-429, miR-183-5p, and miR-146a-5p). Furthermore, four miRNAs (miR-378c, miR-4705, miR-1321, and miR-362-3p) were uniquely detected. This research elucidated the feasibility of the collection, quantification, and detection of miRNA from endometrial fluid with a minimally invasive procedure performed during a patient in-office visit. The screening of a larger set of clinical samples was necessary to validate these early detection biomarkers for endometrial cancer.

Omics insights into extracellular vesicles in embryo implantation and their therapeutic utility

Implantation success relies on intricate interplay between the developing embryo and the maternal endometrium. Extracellular vesicles (EVs) represent an important player of this intercellular signalling through delivery of functional cargo (proteins and RNAs) that reprogram the target cells protein and RNA landscape. Functionally, the signalling reciprocity of endometrial and embryo EVs regulates the site of implantation, preimplantation embryo development and hatching, antioxidative activity, embryo attachment, trophoblast invasion, arterial remodelling, and immune tolerance. Omics technologies including mass spectrometry have been instrumental in dissecting EV cargo that regulate these processes as well as molecular changes in embryo and endometrium to facilitate implantation. This has also led to discovery of potential cargo in EVs in human uterine fluid (UF) and embryo spent media (ESM) of diagnostic and therapeutic value in implantation success, fertility, and pregnancy outcome. This review discusses the contribution of EVs in functional hallmarks of embryo implantation, and how the integration of various omics technologies is enabling design of EV-based diagnostic and therapeutic platforms in reproductive medicine.

Association between Sperm Morphology and Altered Sperm microRNA Expression

Simple Summary

Sperm morphology is usually determined subjectively, and studies focused exclusively on sperm morphology are scarce. There is a global tendency to find objective markers of spermatozoa quality, including sperm morphology, as this will allow for a more personalized approach to managing and treating male infertility. MicroRNAs (miRNAs) are widely recognized as promising putative and objective biomarkers. In our study, we included 15 patients with normal sperm morphology and 13 patients with abnormal sperm morphology. We determined the expression profiles of 13 different miRNAs in the sperm of these participants and revealed that 9 miRNAs could serve as potential biomarkers of sperm morphology in spermatozoa.

Abstract

Evaluation of male infertility has been based on semen analysis for years. As this method can be subjective at times, there is a scientific tendency to discover stable and quantifiable biomarkers. This study included 28 couples who underwent an in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycle. The couples were assigned into two groups, according to sperm morphology. Couples where the males were normozoospermic were placed in the control group (15 participants), while couples where males had teratozoospermia were placed in the study group (13 participants). Thirteen candidate miRNAs were selected for qPCR analysis, based on our literature search. We determined significant under-expression of nine miRNAs (miR-10a-5p/-15b-5p/-26a-5p/-34b-3p/-122-5p/-125b-5p/-191-5p/-296-5p and let-7a-5p) in spermatozoa from patients with teratozoospermia compared to the controls, whereas expression levels of four miRNAs (miR-92a-3p/-93-3p/-99b-5p/-328-3p) did not significantly differ between the study and control groups. The expression levels of all 13 included miRNAs were significantly positively correlated with each other and significantly positively associated with spermatozoa morphology, excluding miR-99b-5p. There were no other significant associations between miRNA expression and sperm quality parameters. Only expression levels of miR-99b-5p were significantly positively correlated with good-quality day 3 embryo rate (ρ = 0.546; p = 0.003), while other variables of the IVF/ICSI cycle outcome showed no significant associations with miRNA expression profiles. This is one of the rare studies providing an insight directly into miRNA profiles in regard to sperm morphology. We identified nine miRNAs that could serve as biomarkers of spermatozoa quality in regard to teratozoospermia.

Endometrium Immunomodulation to Prevent Recurrent Implantation Failure in Assisted Reproductive Technology

After more than four decades of assisted reproductive technology (ART) practice worldwide, today more than 60% of women undergoing in vitro fertilization (IVF) treatments fail to become pregnant after the first embryo transfer and nearly 20% of patients are suffering from unexplained recurrent implantation failures (RIFs) and repeated pregnancy loss (RPL). The literature reported different causes of RIF–RPL, mainly multifactorial, endometrial and idiopathic. RIF remains a black box because of the complicated categorization and causes of this physio-pathological dysregulation of implantation and pregnancy process after ovarian stimulation. Many options were suggested as solutions to treat RIF–RPL with controversial results on their usefulness. In this article, we reviewed different possible therapeutic options to improve implantation rates and clinical outcomes. Based on our experience we believe that endometrium immunomodulation after intrauterine insemination of activated autologous peripheral blood mononuclear cells (PBMCs) or platelet-rich plasma (PRP) can be a promising therapeutic solution. On the other hand, peripheral lymphocyte balance typing, specific cytokines and interleukins profiling can be proposed as predictive biomarkers of implantation before embryo transfer.