miR-142-3p as a biomarker of blastocyst implantation failure - A pilot study

Role of miRNAs in assisted reproductive technology

Cellular proteins and the mRNAs that encode them are key factors in oocyte and sperm development, and the mechanisms that regulate their translation and degradation play an important role during early embryogenesis. There is abundant evidence that expression of microRNAs (miRNAs) is crucial for embryo development and are highly involved in regulating translation during oocyte and early embryo development. MiRNAs are a group of short (18-24 nucleotides) non-coding RNA molecules that regulate post-transcriptional gene silencing. The miRNAs are secreted outside the cell by embryos during preimplantation embryo development. Understanding regulatory mechanisms involving miRNAs during gametogenesis and embryogenesis will provide insights into molecular pathways active during gamete formation and early embryo development. This review summarizes recent findings regarding multiple roles of miRNAs in molecular signaling, plus their transport during gametogenesis and embryo preimplantation.

Association of Trophectoderm mRNAs and MicroRNAs with Chromosomal Aneuploidy of Embryo

MicroRNAs (miRNAs) and mRNAs can serve as indicators of the chromosomal state of an embryo, with different profiles observed in euploid and aneuploid blastocysts. Examining the levels of miRNAs associated with aneuploidy and euploidy, as well as mRNAs related to implantation, can aid in predicting blastocyst chromosomal normality and improving assisted reproductive technology (ART) outcomes. This study analyzed chromosomal abnormality of 25 blastocysts using fluorescence in situ hybridization (FISH) and also the expression of genes ERBB4, SELL, ITGB3, and ITGAV, as well as miRNAs, miR-339, miR-27b, miR-661, miR-30c, miR-191, miR-345, miR-142, miR-141, miR-20a, and miR-372. We found that 17 out of 25 embryos were aneuploid. Moreover, results revealed lower expression levels of miR-30c and miR-372 in aneuploid embryos compared to euploid ones, while ITGAV and ITGB3 showed significantly higher expression in aneuploid embryos. These findings suggest that miR-372, miR-30c, ITGAV, and ITGB3 expression in trophectoderm cells can serve as biomarkers for assessing embryo health.

When the Embryo Meets the Endometrium: Identifying the Features Required for Successful Embryo Implantation

Evaluation of the optimal number of embryos, their quality, and the precise timing for transfer are critical determinants in reproductive success, although still remaining one of the main challenges in assisted reproduction technologies (ART). Indeed, the success of in vitro fertilization (IVF) treatments relies on a multitude of events and factors involving both the endometrium and the embryo. Despite concerted efforts on both fronts, the overall success rates of IVF techniques continue to range between 25% and 30%. The role of the endometrium in implantation has been recently recognized, leading to the hypothesis that both the "soil" and the "seed" play a central role in a successful pregnancy. In this respect, identification of the molecular signature of endometrial receptivity together with the selection of the best embryo for transfer become crucial in ART. Currently, efforts have been made to develop accurate, predictive, and personalized tests to identify the window of implantation and the best quality embryo. However, the value of these tests is still debated, as conflicting results are reported in the literature. The purpose of this review is to summarize and critically report the available criteria to optimize the success of embryo transfer and to better understand current limitations and potential areas for improvement.

MicroRNAs, small regulatory elements with significant effects on human implantation: a review

Embryo implantation is a critical process for achieving a successful pregnancy and live birth. The proper implantation must have a synchronized interaction between blastocyst and a receptive endometrium. Many genes are involved in the modulation of precise molecular events during implantation. MicroRNAs (miRNAs) have been extensively reported as gene regulatory molecules on post-transcriptional levels involved in various biological processes such as gametogenesis, embryogenesis, and the quality of sperm, oocyte, and embryos. A plethora of evidence has demonstrated critical roles for miRNAs in regulating genes involved in the implantation process; hence, dysregulation of miRNAs could be associated with significant impairments in implantation, such as recurrent implantation failure. In addition to the indispensable role of miRNAs in the intracellular control of gene expression, they can also be secreted into extracellular fluid and circulation. Therefore, miRNAs in body fluids and blood may be exploited as non-invasive diagnostic biomarkers for different pathological and physiological conditions. Recently, several studies have focused on the discovery of miRNAs function in the implantation process by appraising miRNAs and their target genes in human embryos, endometrial tissue, and cell culture models. Moreover, it was revealed that there could be a significant association between endometrial receptivity or implantation status and the expression of miRNAs in human body fluids, reinforcing their role as non-invasive biomarkers. In the current work, we reviewed the studies concerning the role of intracellular and extracellular miRNAs in human implantation and the influence of their dysregulation on implantation disorders.

Non-Coding RNAs as Biomarkers for Embryo Quality and Pregnancy Outcomes: A Systematic Review and Meta-Analysis

Despite advances in in vitro fertilization (IVF), there is still a lack of non-invasive and reliable biomarkers for selecting embryos with the highest developmental and implantation potential. Recently, small non-coding RNAs (sncRNAs) have been identified in biological fluids, and extracellular sncRNAs are explored as diagnostic biomarkers in the prediction of IVF outcomes. To determine the predictive role of sncRNAs in embryo quality and IVF outcomes, a systematic review and meta-analysis was performed. Articles were retrieved from PubMed, EMBASE, and Web of Science from 1990 to 31 July 2022. Eighteen studies that met the selection criteria were analyzed. In total, 22 and 47 different sncRNAs were found to be dysregulated in follicular fluid (FF) and embryo spent culture medium (SCM), respectively. MiR-663b, miR-454 and miR-320a in FF and miR-20a in SCM showed consistent dysregulation in two different studies. The meta-analysis indicated the potential predictive performance of sncRNAs as non-invasive biomarkers, with a pooled area under curve (AUC) value of 0.81 (95% CI 0.78, 0.844), a sensitivity of 0.79 (95% CI 0.72, 0.85), a specificity of 0.67 (95% CI 0.52, 0.79) and a diagnostic odds ratio (DOR) of 8 (95% CI 5, 12). Significant heterogeneity was identified among studies in sensitivity (I2  =  46.11%) and specificity (I2  =  89.73%). This study demonstrates that sncRNAs may distinguish embryos with higher developmental and implantation potentials. They can be promising non-invasive biomarkers for embryo selection in ART. However, the significant heterogeneity among studies highlights the demand for prospective multicenter studies with optimized methods and adequate sample sizes in the future.

Exosomes: New regulators of reproductive development

Exosomes are a subtype of extracellular vesicles (EVs) with a size range between 30 and 150 ​nm, which can be released by the majority of cell types and circulate in body fluid. They function as a long-distance cell-to-cell communication mechanism that modulates the gene expression profile and fate of target cells. Increasing evidence has indicated exosomes' central role in regulating various complex reproductive processes. However, to our knowledge, a review that focally and vividly describes the role of exosomes in reproductive development is still lacking. This review highlights our knowledge about the contribution of exosomes to early mammalian reproduction, such as gametogenesis, fertilization, early embryonic development, implantation, placentation and pregnancy. The discussion is primarily drawn from literature pertaining to the mammalian lineage with emphasis on the roles of exosomes in human reproduction and laboratory and livestock models.

Potential roles of extracellular vesicles as a noninvasive tool for prenatal genetic diagnosis

The rate of infertility is increasing owing to genetic and environmental factors. Consequently, assisted reproductive technology has been introduced as an alternative. Bearing in mind the global trend toward the transfer of only one embryo, there is an increasing trend for assessing embryo quality before transfer through prenatal genetic diagnosis (PGD) tests. This ensures that the best-quality embryos are implanted into the uterus. In the in vitro fertilization cycle, PGD is not only used for diseases or quality checks before embryo freezing but also for evaluating unfortunate risks, such as aneuploidy, signs of early abortions, and preterm birth. However, traditional preimplantation genetic testing and screening approaches are invasive and harm the health of both the mother and embryo, raising the risk of miscarriage. In the last decade, embryonic extracellular vesicles (EVs) have been investigated and have emerged as a promising diagnostic tool. In this mini-review, we address the use of EVs as a noninvasive biomarker in PGD to test for biological hazards within the embryo without invading its cells. We summarize the state-of-the-art in the use of the embryo's EV content, genomic DNA, messenger RNA, and microRNA in the spent culture medium and their relationship with embryo quality, successful implantation, and pregnancy.

microRNAs as A Biomarker to Predict Embryo Quality Assessment in In Vitro Fertilization

Embryo selection for in vitro fertilization (IVF) is an effort to increase the success rate of embryo implantation. Factors influencing the success of embryo implantation include embryo quality, endometrial receptivity, embryo characteristics, and maternal interactions. Some molecules have been found to influence these factors, but their regulatory mechanisms are unclear. MicroRNAs (miRNAs) are reported to play an essential role in the embryo implantation process. miRNAs are small non-coding RNAs consisting of only 20 nucleotides that play an essential role in the stability of gene expression regulation. Previous studies have reported that miRNAs have many roles and are released by cells into the extracellular environment for intracellular communication. In addition, miRNAs can provide information related to physiological and pathological conditions. These findings encourage research development in determining the quality of embryos in IVF to increase the implantation success rate. Moreover, miRNAs can provide an overview of embryo-maternal communication and potentially be noninvasive biological markers of embryo quality, which could increase assessment accuracy while reducing mechanical damage to the embryo itself. This review article summarizes the involvement of extracellular miRNAs and the potential applications of miRNAs in IVF.

miR‑519d‑3p released by human blastocysts negatively regulates endometrial epithelial cell adhesion by targeting HIF1α

Successful embryo implantation requires a competent embryo, a receptive endometrium and synchronized communication between them. The selection of embryos with the highest implantation potential remains a challenge in the field of assisted reproductive technology. Moreover, little is known about the precise molecular mechanisms underlying embryo‑endometrium crosstalk. MicroRNAs (miRNAs/miRs) have been detected in the spent embryo culture medium (SCM); however, their functions at the preimplantation stage remain unclear. In the present study, human SCM samples were collected during in vitro fertilization/intracytoplasmic sperm injection‑embryo transfer and divided into implanted and not‑implanted groups according to the clinical pregnancy outcomes. Total RNA was extracted and six miRNAs (miR‑372‑3p, miR‑373‑3p, miR‑516b‑5p, miR‑517a‑3p, miR‑519d‑3p and miR‑520a‑3p) were selected for reverse transcription‑quantitative PCR (RT‑qPCR) analysis. The results revealed that miR‑372‑3p and miR‑519d‑3p were markedly increased in SCM from blastocysts that failed to implant compared with in blastocysts that implanted. The receiver operating characteristic curve analysis revealed that miR‑519d‑3p was superior to miR‑372‑3p in predicting pregnancy outcomes. In vitro miRNA uptake and cell adhesion assays were performed to determine whether miR‑519d‑3p could be taken up by endometrial epithelial cells and to examine the biological roles of miR‑519d‑3p after internalization. Potential targets of miR‑519d‑3p were verified using a dual‑luciferase reporter system. The results demonstrated that miR‑519d‑3p was taken up by human endometrial epithelial cells and that it may inhibit embryo adhesion by targeting HIF1α. Using RT‑qPCR, western blot analysis and flow cytometry assay, HIF1α was shown to inhibit the biosynthesis of fucosyltransferase 7 and sialyl‑Lewis X (sLe^x), a cell‑surface oligosaccharide that serves an important role in embryonic apposition and adhesion. In addition, a mouse model was established and the results suggested that miR‑519d‑3p overexpression hampered embryo implantation in vivo. Taken together, miRNAs in SCM may serve as novel biomarkers for embryo quality. Furthermore, miR‑519d‑3p was shown to mediate embryo‑endometrium crosstalk and to negatively regulate embryo implantation by targeting HIF1α/FUT7/sLe^x pathway.

microRNAs in the blastocoel fluid as accessible indicators of chromosomal normality

MicroRNAs (miRNAs) derived from the pre-implantation blastocoel fluid (BF) have attracted interest as accessible biomarkers indicative of embryonic health in ongoing IVF cycles. Therefore, we investigated expression levels of some aneuploidy-associated miRNAs and implantation-related mRNAs as predictive markers for embryo chromosomal normality. In this study, the BF of 25 blastocysts that had been checked for aneuploidy (aneuploid=17 and euploid=8) was aspirated and the expression of 10 miRNAs (miR-20a, miR-30c, miR-661, miR-372, miR-142, miR-191, miR-345, miR-339, miR-141, and miR-27b) and four genes (ERBB4, SELL, ITGB3, ITGAV) were evaluated using real time-PCR. Results showed that the levels of miR-661 and miR-20a were significantly higher in the BF of the aneuploid embryos compared to the euploid group (p = 0.0017 and 0.004, respectively). A comparison of the mRNA levels between the aneuploid and euploid groups also demonstrated a significant difference in ITGAV (p = 0.013) and SELL (p = 0.0317) levels. In the euploid group, a negative correlation was found between ITGB3 and miR-30c (r = -0.71, p = 0.08), and in the aneuploid group, a positive correlation was found between ERBB4 and miR-345 (r = 0.71, p = 0.02). It can be suggested that miR-20a, miR-661, and ITGAV levels of BF could be used as less-invasive biomarkers to evaluate embryonic health. Moreover, aneuploidy-related miRNA levels were associated with levels of genes involved in embryo implantation.

Role of miRNAs in preimplantation embryo development and their potential as embryo selection biomarkers

CONTEXT

MicroRNAs (miRNAs) play different roles in oocyte fertilisation, degradation of maternal transcripts, embryo development, and implantation. During in vitro fertilisation (IVF), different miRNAs are released from embryos into the spent culture media (SCM) that can potentially reflect the status of the embryo.

AIMS

This study is the assessment of miRNAs, which secreted in SCM during the IVF cycles can be used as noninvasive biomarkers to predict an embryo's ability to form a blastocyst, implant, and give live birth.

METHODS

Systematic literature search was conducted to review all recent studies about miRNAs as potential non-invasive biomarkers for selecting the best embryos in the assisted reproductive technology (ART) cycle.

KEY RESULTS

Studies have shown that levels of some miRNAs in the SCM have an association with the implantation potential and pregnancy outcome of the embryo.

CONCLUSIONS

Embryo-secreted miRNAs can be used as potential non-invasive biomarkers for selecting the best embryos in the ART cycle. Unfortunately, few human studies evaluated the association between ART outcomes and miRNAs in SCM.

IMPLICATIONS

This review can pave the way for further miRNAs transcriptomic studies on human embryo culture media and introducing a specific miRNA profile as a multivariable prediction model for embryo selection in IVF cycles.

Building Pluripotency Identity in the Early Embryo and Derived Stem Cells

The fusion of two highly differentiated cells, an oocyte with a spermatozoon, gives rise to the zygote, a single totipotent cell, which has the capability to develop into a complete, fully functional organism. Then, as development proceeds, a series of programmed cell divisions occur whereby the arising cells progressively acquire their own cellular and molecular identity, and totipotency narrows until when pluripotency is achieved. The path towards pluripotency involves transcriptome modulation, remodeling of the chromatin epigenetic landscape to which external modulators contribute. Both human and mouse embryos are a source of different types of pluripotent stem cells whose characteristics can be captured and maintained in vitro. The main aim of this review is to address the cellular properties and the molecular signature of the emerging cells during mouse and human early development, highlighting similarities and differences between the two species and between the embryos and their cognate stem cells.

Murine Blastocysts Release Mature MicroRNAs Into Culture Media That Reflect Developmental Status

Extracellular microRNA (miRNA) sequences derived from the pre-implantation embryo have attracted interest for their possible contributions to the ongoing embryonic-uterine milieu, as well as their potential for use as accessible biomarkers indicative of embryonic health. Spent culture media microdroplets used to culture late-stage E4.0 murine blastocysts were screened for 641 mature miRNA sequences using a reverse transcription-quantitative polymerase chain reaction-based array. We report here 39 miRNAs exclusively detected in the conditioned media, including the implantation-relevant miR-126a-3p, miR-101a, miR-143, and miR-320, in addition to members of the highly expressed embryonic miR-125 and miR-290 families. Based on these results, an miRNA panel was assembled comprising five members of the miR-290 family (miR-291-295) and five conserved sequences with significance to the embryonic secretome (miR-20a, miR-30c, miR-142-3p, miR-191, and miR-320). Panel profiling of developing embryo cohort lysates and accompanying conditioned media microdroplets revealed extensive similarities in relative quantities of miRNAs and, as a biomarker proof of concept, enabled distinction between media conditioned with differently staged embryos (zygote, 4-cell, and blastocyst). When used to assess media conditioned with embryos of varying degrees of degeneration, the panel revealed increases in all extracellular panel sequences, suggesting cell death is an influential and identifiable factor detectable by this assessment. In situ hybridization of three panel sequences (miR-30c, miR-294, and miR-295) in late-stage blastocysts revealed primarily inner cell mass expression with a significant presence of miR-294 throughout the blastocyst cavity. Furthermore, extracellular miR-290 sequences responded significantly to high centrifugal force, suggesting a substantial fraction of these sequences may exist within a vesicle such as an exosome, microvesicle, or apoptotic bleb. Together, these results support the use of extracellular miRNA to assess embryonic health and enable development of a non-invasive viability diagnostic tool for clinical use.

Small non-coding RNAs in embryonic pre-implantation

Failure of embryo implantation has been introduced as an important limiting parameter in early assisted reproduction and pregnancy. The embryo-maternal interactions, endometrial receptivity, and detections of implantation consist of the embryo viability. For regulating the implantation, multiple molecules may be consisted, however, their specific regulatory mechanisms still stand unclear. MicroRNAs (miRNAs) have been highly concerned due to their important effect on human embryo implantation. MicroRNA (miRNA), which acts as the transcriptional regulator of gene expression, is consisted in embryo implantation. Scholars determined that miRNAs cannot affect the cells and release by cells in the extracellular environment considering facilitating intercellular communication, multiple packaging forms, and preparing indicative data in the case of pathological and physiological conditions. The detection of extracellular miRNAs provided new information in cases of implantation studies. For embryo-maternal communication, MiRNAs offered novel approaches. In addition, in assisted reproduction, for embryo choice and prediction of endometrial receptivity, they can act as non-invasive biomarkers and can enhance the accuracy in the process of reducing the mechanical damage for the tissue.

The Involvement of MicroRNAs in SARS-CoV-2 Infection Comorbid with HIV-Associated Preeclampsia

Purpose of Review

This review investigated the potential role of microRNAs (miRNAs) in the synergy of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, preeclampsia (PE), and human immunodeficiency virus (HIV) infection. Maternal health is a great concern when treating pregnant women fighting this triad of diseases, which is highly prevalent in South Africa. MicroRNAs are involved in fine-tuning of physiological processes. Disruptions to the balance of this minute protein can lead to various physiological changes that are sometimes pathological.

Recent Findings

MicroRNAs have recently been implicated in PE and have been linked to the anti-angiogenic imbalance evident in PE. Recent in silico studies have identified potential host miRNAs with anti-viral properties against SARS-CoV-2 infection. Studies have demonstrated dysregulated expression of several miRNAs in HIV-1 infection along with the ability of HIV-1 to downregulate anti-viral host microRNAs.

Summary

This review has highlighted the significant gap in literature on the potential of miRNAs in women with HIV-associated PE in synergy with the novel SARS-CoV-2 infection. In addition, this review has provided evidence of the critical role that the epigenetic regulatory mechanism of miRNA plays in viral infections and PE, thereby providing a foundation for further research investigating the potential of therapeutic miRNA development with fewer side-effects for pregnant women.

Current Advancements in Noninvasive Profiling of the Embryo Culture Media Secretome

There have been over 8 million babies born through in vitro fertilization (IVF) and this number continues to grow. There is a global trend to perform elective single embryo transfers, avoiding risks associated with multiple pregnancies. It is therefore important to understand where current research of noninvasive testing for embryos stands, and what are the most promising techniques currently used. Furthermore, it is important to identify the potential to translate research and development into clinically applicable methods that ultimately improve live birth and reduce time to pregnancy. The current focus in the field of human reproductive medicine is to develop a more rapid, quantitative, and noninvasive test. Some of the most promising fields of research for noninvasive assays comprise cell-free DNA analysis, microscopy techniques coupled with artificial intelligence (AI) and omics analysis of the spent blastocyst media. High-throughput proteomics and metabolomics technologies are valuable tools for noninvasive embryo analysis. The biggest advantages of such technology are that it can differentiate between the embryos that appear morphologically identical and has the potential to identify the ploidy status noninvasively prior to transfer in a fresh cycle or before vitrification for a later frozen embryo transfer.

Extracellular vesicles, microRNA and the preimplantation embryo: non-invasive clues of embryo well-being

Elective single embryo transfer is rapidly becoming the standard of care in assisted reproductive technology for patients under the age of 35 years with a good prognosis. Clinical pregnancy rates have become increasingly dependent on the selection of a single viable embryo for transfer, and diagnostic techniques facilitating this selection continue to develop. Current progress in elucidating the extracellular vesicle and microRNA components of the embryonic secretome is reviewed, and the potential for these findings to improve clinical embryo selection discussed. Key results have shown that extracellular vesicles and microRNAs are rapidly detectable constituents of the embryonic secretome. Evidence suggests that the vesicular population is largely exosomal in nature, secreted at all stages of preimplantation development and capable of traversing the zona pellucida. Both extracellular vesicle and microRNA concentrations within the secretome are elevated for blastocysts with diminished developmental competence, as indicated either by degeneracy or implantation failure, whereas studies have yet to firmly correlate individual microRNA sequences with pregnancy outcome. These emerging correlations support the viability of extracellular vesicles and microRNAs as the basis for a new diagnostic test to supplement or replace morphokinetic assessment.

Secreted MicroRNA to Predict Embryo Implantation Outcome: From Research to Clinical Diagnostic Application

Embryo implantation failure is considered a leading cause of infertility and a significant bottleneck for in vitro fertilization (IVF) treatment. Confirmed factors that lead to implantation failure involve unhealthy embryos, unreceptive endometrium, and asynchronous development and communication between the two. The quality of embryos is further dependent on sperm parameters, oocyte quality, and early embryo development after fertilization. The extensive involvement of such different factors contributes to the variability of implantation potential across different menstrual cycles. An ideal approach to predict the implantation outcome should not compromise embryo implantation. The use of clinical material, including follicular fluid, cumulus cells, sperm, seminal exosomes, spent blastocyst culture medium, blood, and uterine fluid, that can be collected relatively non-invasively without compromising embryo implantation in a transfer cycle opens new perspectives for the diagnosis of embryo implantation potential. Compositional comparison of these samples between fertile women and women or couples with implantation failure has identified both quantitative and qualitative differences in the expression of microRNAs (miRs) that hold diagnostic potential for implantation failure. Here, we review current findings of secreted miRs that have been identified to potentially be useful in predicting implantation outcome using material that can be collected relatively non-invasively. Developing non-invasive biomarkers of implantation potential would have a major impact on implantation failure and infertility.

Definition and validation of a custom protocol to detect miRNAs in the spent media after blastocyst culture: searching for biomarkers of implantation

STUDY QUESTION

Can miRNAs be reliably detected in the spent blastocyst media (SBM) after IVF as putative biomarkers of the implantation potential of euploid embryos?

SUMMARY ANSWER

Adjustment of the data for blastocyst quality and the day of full-expansion hinders the predictive power of a fast, inexpensive, reproducible and user-friendly protocol based on the detection of 10 selected miRNAs from SBM.

WHAT IS KNOWN ALREADY

Euploidy represents so far the strongest predictor of blastocyst competence. Nevertheless, ~50% of the euploid blastocysts fail to implant. Several studies across the years have suggested that a dialogue exists between the embryo and the endometrium aimed at the establishment of a pregnancy. MicroRNAs have been proposed as mediators of such a dialogue and investigated in this respect. Several expensive, time-consuming and complex protocols have been adopted and promising results have been produced, but conclusive evidence from large clinical studies is missing.

STUDY DESIGN, SIZE, DURATION

This study was conducted in two phases from September 2015 to December 2017. In Phase 1, the human blastocyst miRNome profile was defined from the inner cell mass (ICM) and the corresponding whole-trophectoderm (TE) of six donated blastocysts. Two different protocols were adopted to this end. In parallel, 6 pools of 10 SBM each were run (3 from only implanted euploid blastocysts, IEBs; and 3 from only not-implanted euploid blastocysts, not-IEBs). A fast, inexpensive and user-friendly custom protocol for miRNA SBM profiling was designed. In Phase 2, 239 SBM from IEB and not-IEB were collected at three IVF centres. After 18 SBM from poor-quality blastocysts were excluded from the analysis, data from 107 SBM from not-IEB and 114 from IEB were produced through the previously developed custom protocol and compared. The data were corrected through logistic regressions.

PARTICIPANT/MATERIALS, SETTINGS, METHODS

Donated blastocysts underwent ICM and whole-TE isolation. SBM were collected during IVF cycles characterized by ICSI, blastocyst culture in a continuous media, TE biopsy without zona pellucida opening in Day 3, quantitative PCR (qPCR)-based aneuploidy testing and vitrified-warmed single euploid embryo transfer. Not-IEB and IEB were clustered following a negative pregnancy test and a live birth, respectively. The Taqman Low Density Array (TLDA) cards and the Exiqon microRNA human panel I+II qPCR analysis protocols were adopted to analyse the ICM and whole-TE. The latter was used also for SBM pools. A custom protocol and plate was then designed based on the Exiqon workflow, validated and finally adopted for SBM analysis in study Phase 2. This custom protocol allows the analysis of 10 miRNAs from 10 SBM in 3 hours from sample collection to data inspection.

MAIN RESULTS AND ROLE OF THE CHANCE

The TLDA cards protocol involved a higher rate of false positive results (5.6% versus 2.8% with Exiqon). There were 44 miRNAs detected in the ICM and TE from both the protocols. One and 24 miRNAs were instead detected solely in the ICM and the TE, respectively. Overall, 29 miRNAs were detected in the pooled SBM: 8 only from not-IEB, 8 only from IEB and 13 from both. Most of them (N = 24/29, 82.7%) were also detected previously in both the ICM and TE with the Exiqon protocol; two miRNAs (N = 2/29, 6.9%) were previously detected only in the TE, and three (N = 3/29, 10.3%) were never detected previously. In study Phase 2, significant differences were shown between not-IEB and IEB in terms of both miRNA detection and relative quantitation. However, when the data were corrected for embryo morphology and day of full development (i.e. SBM collection), no significant association was confirmed.

LIMITATIONS, REASONS FOR CAUTION

This study did not evaluate specifically exosomal miRNAs, thereby reducing the chance of identifying the functional miRNAs. Ex-vivo experiments are required to confirm the role of miRNAs in mediating the dialogue with endometrial cells, and higher throughput technologies need to be further evaluated for miRNA profiling from clinical SBM samples.

WIDER IMPLICATIONS OF THE FINDINGS

Although no clinical predictive power was reported in this study, the absence of invasiveness related with SBM analysis and the evidence that embryonic genetic material can be reliably detected and analysed from SBM make this waste product of IVF an important source for further investigations aimed at improving embryo selection.

STUDY FUNDING/COMPETING INTEREST(S)

This project has been financially supported by Merck KgaA (Darmstadt, Germany) with a Grant for Fertility Innovation (GFI) 2015. The authors have no conflict of interest to declare related with this study.

TRIAL REGISTRATION NUMBER

None.

Endometrial microRNAs and their aberrant expression patterns

MicroRNAs (miRNAs) are a class of small noncoding RNAs that regulate gene expression. They play fundamental roles in several biological processes, including cell differentiation and proliferation, embryo development, organ development, and organ metabolism. Besides regulating the physiological processes, miRNAs regulate various pathological conditions such as tumors, metastases, metabolic diseases, and osteoporosis. Although several studies have been performed on miRNAs, only few studies have described the miRNA expression and functions in human reproductive tract tissues. During menstruation, the human endometrium undergoes extensive cyclic morphological and biochemical modifications before embryo implantation. In addition to the ovarian steroid hormones (estrogen and progesterone), endometrial autocrine or paracrine factors and embryo-derived signals play a significant role in endometrial functions. miRNAs are considered key regulators of gene expression in the human endometrium and implantation process, and their aberrant expression levels are associated with the development of various disorders, including tumorigenesis. In this review, we summarize the studies that show the role of miRNAs in regulating the physiological conditions of the endometrium and the implantation process and discuss the aberrant expression of miRNAs in ectopic pregnancy, endometriosis, and endometrial cancer.

MicroRNAs in combined spent culture media and sperm are associated with embryo quality and pregnancy outcome

OBJECTIVE

To identify differentially abundant miRNAs in sperm samples and spent culture media (SCM) of embryos of different grade toward a prediction of pregnancy outcome.

DESIGN

Array-based reverse-transcription quantitative polymerase chain reaction profiling and validation.

SETTING

University research institute and in vitro fertilization center.

PATIENT(S)

Couples (n = 61) undergoing infertility treatment with the use of intracytoplasmic sperm injection.

INTERVENTIONS(S)

None.

MAIN OUTCOME MEASURE(S)

Abundance levels of miRNAs in combined SCM of embryos of different quality and in sperm samples associated with pregnancy outcome.

RESULT(S)

Out of 372 screened miRNAs, miR-19b-3p and let-7a-5p were detected consistently in all SCM and sperm samples. The abundance levels of miRNAs were significantly altered between SCM of embryos with different quality (G1, G2, and G3 grades). Specifically, miR-320a and miR-15a-5p were differentially abundant in G1 vs. G2, miR-21-5p in G1 vs. G3, and miR-20a-5p in G2 vs. G3. The abundance levels of combined SCM and sperm derived miRNAs were also significantly altered between different pregnancy outcomes. MiR-19b-3p showed the highest area under the receiver operating characteristic curve values between positive and negative outcomes, with lower abundance levels in both combined SCM and sperm samples associated with a positive pregnancy outcome. MiR-320a, miR-15a-5p, miR-21-5p, and miR-20a-5p showed similar results in combined SCM samples.

CONCLUSION(S)

miRNA abundance levels in combined SCM and sperm differed significantly depending on embryo quality and pregnancy outcome. MiR-19b-3p may serve as a potential biomarker to predict pregnancy outcome.

Head and neck squamous cancer progression is marked by CLIC4 attenuation in tumor epithelium and reciprocal stromal upregulation of miR-142-3p, a novel post-transcriptional regulator of CLIC4

Chloride intracellular channel 4 (CLIC4) is a tumor suppressor implicated in processes including growth arrest, differentiation, and apoptosis. CLIC4 protein expression is diminished in the tumor parenchyma during progression in squamous cell carcinoma (SCC) and other neoplasms, but the underlying mechanisms have not been identified. Data from The Cancer Genome Atlas suggest this is not driven by genomic alterations. However, screening and functional assays identified miR-142-3p as a regulator of CLIC4. CLIC4 and miR-142-3p expression are inversely correlated in head and neck (HN) SCC and cervical SCC, particularly in advanced stage cancers. In situ localization revealed that stromal immune cells, not tumor cells, are the predominant source of miR-142-3p in HNSCC. Furthermore, HNSCC single-cell expression data demonstrated that CLIC4 is lower in tumor epithelial cells than in stromal fibroblasts and endothelial cells. Tumor-specific downregulation of CLIC4 was confirmed in an SCC xenograft model concurrent with immune cell infiltration and miR-142-3p upregulation. These findings provide the first evidence of CLIC4 regulation by miRNA. Furthermore, the distinct localization of CLIC4 and miR-142-3p within the HNSCC tumor milieu highlight the limitations of bulk tumor analysis and provide critical considerations for both future mechanistic studies and use of miR-142-3p as a HNSCC biomarker.

Expression of miR-Let-7a, miR-15a, miR-16-1, and their target genes in fresh and vitrified embryos and its surrounding culture media for noninvasive embryo assessment

microRNAs (miRNAs) play a critical role in implantation and development of mouse embryos. In this study, we aim to evaluate the possibility of miRNAs as potential biomarkers in the blastocyst culture to assess embryo quality. We also intend to investigate whether improved clinical outcomes of vitrified embryos agree with altered miRNA expressions. Mouse embryos from in vitro fertilization were vitrified at the two-cell stage. After thawing, the embryos were individually cultured and developed to the blastocyst stage. We used quantitative real-time polymerase chain reaction to evaluate miRNA expression levels in both vitrified and fresh groups, and culture medium (CM). The fibronectin binding assay was performed to examine for blastocyst attachment. The findings showed reduced expressions of miR-16-1 (0.2 ± 0.06) and miR-Let-7a (0.65 ± 0.1) after vitrification compared to fresh embryos. We observed significant upregulation of the target genes Vav3 (4.33 ± 0.25), integrin β-3 (Itg β3; 4.73 ± 0.2), and Bcl2 (2.29 ± 0.16) in the vitrified embryos compared to the fresh groups. Evaluation of blastocyst CM showed upregulation of miR-Let-7a (15.68 ± 0.89), miR-16-1 (16.18 ± 0.75), and miR-15a (13.36 ± 0.73) in the vitrified group in comparison to the fresh blastocysts (P < .05). The expression levels of miR-16-1 (3.28 ± 0.63), miR-15a (5.91 ± 0.38), and miR-Let-7a (9.07 ± 0.6) in CM of the vitrified blastocysts conducted on fibronectin were significantly higher than the fresh group (P < .05).This study showed that vitrification of embryos changes implantation and proliferation biomarkers. In addition, upregulated miRNAs in CM could be potentially used for noninvasive early assessment of embryo quality.

MicroRNA Biogenesis Machinery Is Dysregulated in the Endometrium of Infertile Women Suggesting a Role in Receptivity and Infertility

MicroRNAs (miRs) regulate endometrial function and their dysregulation could underlie unexplained infertility in women. Ribonucleases including DICER and DROSHA, and the proteins, ARGONAUTE 1 (AGO 1) and 2 (AGO 2) regulate the biogenesis/maturation of miRs. We aimed to elucidate the expression and localization of miR biogenesis machinery components during the human menstrual cycle and compare their levels in endometrium from women with normal fertility and primary unexplained infertility. miR biogenesis components were measured by quantitative-RT-PCR and immunohistochemistry. In the endometrium of women with normal fertility, DROSHA immunolocalized maximally to the epithelium during the early and mid-secretory phases compared with the proliferative and late-secretory phases. Stromal DICER immunostaining intensity was higher in the late-secretory phase compared with all other phases in fertile women. DROSHA mRNA was reduced in the mid-secretory-infertile whole endometrial tissue (has all cells of the tissue), and primary epithelial and stromal cells while no differences were found in DICER, AGO1, and AGO2 mRNA. In the luminal epithelium, DROSHA staining intensity was reduced in early and mid-secretory-infertile while DICER staining was reduced in the early secretory-infertile compared with their respective fertile groups. DICER and DROSHA were dynamically regulated across the menstrual cycle and reduced levels during receptivity phase could underlie implantation failure/infertility.

IVM of mouse fully grown germinal vesicle oocytes upon a feeder layer of selected cumulus cells enhances their developmental competence

In the ovary, acquisition of oocyte developmental competence depends on a bidirectional exchange between the gamete and its companion cumulus cells (CCs). In this study we investigated the contribution of CCs surrounding oocytes of known developmental competence or incompetence to the acquisition of oocyte developmental competence. To this end, feeder layers of CCs (FL-CCs) were prepared using CCs isolated either from: (1) developmentally competent mouse oocytes whose nucleolus was surrounded by a chromatin ring (FL-SN-CCs); or (2) developmentally incompetent mouse oocytes whose nucleolus was not surrounded by a chromatin ring (FL-NSN-CCs). Denuded, fully grown oocytes (DOs) were matured to the MII stage on either FL-SN-CCs or FL-NSN-CCs, inseminated with spermatozoa and cultured throughout preimplantation development. FL-SN-CCs significantly improved the acquisition of oocyte developmental competence, with a blastocyst development rate equal to that for maturation of intact cumulus-oocyte-complexes. In contrast, DOs matured on FL-NSN-CCs or in the absence of CCs exhibited developmental failure, with embryos arresting at either the 4-cell or morula stage. These results set a culture platform to further improve the protocols for the maturation of DOs and to unravel the molecules involved in the cross-talk between the gamete and its companion CCs during the germinal vesicle to MII transition.

Predictive factors for biochemical pregnancy in intracytoplasmic sperm injection cycles

The aim of this study was to investigate which factors contribute to the incidence of biochemical pregnancy (BP) in intracytoplasmic sperm injection (ICSI) cycles. This cohort study included cycles performed from June 2010 to September 2016 in a private, university-affiliated IVF centre. Cycles were split into four groups, depending on the pregnancy outcomes: Clinical Pregnancy (CP, n = 903), Biochemical Pregnancy (BP, n = 55), Miscarriage (MI, n = 142) and Negative Pregnancy (NP, n = 2034). The effects of ovarian stimulation, laboratory data and seminal parameters on pregnancy outcomes were evaluated using adjusted general linear models. Discriminant analyses were conducted to construct a model for pregnancy prediction and to establish cut-offs for BP. The total sperm count (p = 0.035), total and progressive sperm motility (p = 0.001 and p = 0.023, respectively), total motile sperm count (TMSC, p = 0.029) and the endometrial thickness (p < 0.001) were lower among BP group cycles. Lower rates of high-quality cleavage-stage embryos were observed in the BP group compared to CP and MI groups (p < 0.001). In discriminant analyses, cut-offs for BP prediction were established for the following factors: endometrial thickness < 11 mm, sperm motility < 55.5% and total dose of follicle-stimulating hormone (FSH)> 2400 IU. The incidence of biochemical pregnancy was four times higher when the aforementioned factors did not meet the defined cut-offs. The combination of suboptimal endometrial development and poor seminal and embryo quality contribute to an increased incidence of biochemical pregnancy in ICSI cycles.

The role of microRNAs in human embryo implantation: a review

MicroRNAs (miRNAs) are emerging as important in human embryo implantation, and we present here a review of the literature from a clinical perspective. Implantation involves complex interactions between the blastocyst and endometrium. miRNAs have been shown to be differentially expressed in implanted compared with non-implanted blastocysts and euploid compared with aneuploid blastocysts. Further, miRNAs are differentially expressed in proliferative compared with decidualized endometrium, and in receptive compared with pre-receptive endometrium. miRNAs are also differentially expressed in endometrium of women who failed implantation, and in endometrium of women with recurrent implantation failure. Due to the complexity of miRNA signaling, studies have suffered from inconsistency in reproducibility of results. However, miRNAs show potential as biomarkers in the pursuit of more reliable prediction of embryo implantation.

Association Between miR-605A>G, miR-608G>C, miR-631I>D, miR-938C>T, and miR-1302-3C>T Polymorphisms and Risk of Recurrent Implantation Failure

Recurrent implantation failure (RIF) is diagnosed when pregnancy failure occurs after 2 consecutive in vitro fertilization-embryo transfers (IVF-ET) to the endometrium using at least 4 high-quality embryos. MicroRNAs (miRNAs) are a class of small noncoding RNA and reported to play an important role in cell proliferation as well as implantation process. Recently, it has been reported that miRNA can regulate RIF occurrence. So, we were to examine the association between the specific miRNA polymorphisms and RIF in Korean women. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay to determine the frequency of the following polymorphisms: miR-605A>G, miR-608G>C, miR-631I>D, miR-938C>T, and miR-1302-3C>T. Our results demonstrate a decreased incidence of RIF in patients with the miR-1302-3C>T polymorphism (adjusted odds ratio [AOR], 0.234; 95% confidence interval [CI], 0.089-0.618; P = .003). Based on our allele combination analysis, the C-T ( miR-938/ miR-1302-3: OR = 0.259; 95% CI, 0.100-0.674; P = .003) allele was also associated with decreased RIF risk. From our interaction analysis with miR-1302-3, the miR-1302-3CC genotype (AOR = 43.332; 95% CI, 5.576-336.745) showed an association with RIF prevalence in participants with an activated partial thromboplastin time (aPTT) ≤22.6. We found that the miR-1302-3C>T polymorphism is significantly associated with RIF development in Korean women. Specifically, our study suggests that the T allele of miR-1302-3 may decrease the risk of RIF in Korean women.

Altered miRNA-profile dependent on ART outcome in early pregnancy targets Wnt-pathway

Main goal of this study is to detect the possible alterations in microRNA (miRNA) expression and the pathway targeted in plasma at the time of embryo transfer and pregnancy testing dependent on the assisted reproductive treatment (ART) outcome after ovarian hyperstimulation for in vitro fertilization. Changes in miRNA expression in plasma of women, who became pregnant (n = 6) vs women who failed implantation (n = 6) following day 5 embryo transfer (ET), were investigated at the day of ET and pregnancy testing (PT). Protein expression to validate the finding was performed with a sample size of n = 20 (10 per group) using enzyme-linked immunosorbent assay. Enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed using DIANA-miRPath, v3.0 software based on predicted targets by DIANA-microT-CDS. 4 miRNAs could be identified as possible biomarkers for implantation success. The 11 miRNAs showing the highest significant alterations were all associated with the regulation of WNT3 and WNT7a. While WNT7a presented with a significant decrease between ET and PT in case of ongoing pregnancy, women with implantation failure showed unaltered concentrations. WNT3 presented with a significant decrease in both groups. However, the loss of WNT3 between ET and PT was significantly higher in patients who became pregnant. Main limitation of this prospective study is its small sample size, defining it as a pilot analysis. To conclude, we could demonstrate a significant change in miRNA profile dependent on the ART outcome affecting Wnt pathway. Our findings indicate a possible prospective use of miRNA as biomarkers for implantation success.