MicroRNAs secreted by human preimplantation embryos and IVF outcome

A temporal extracellular transcriptome atlas of human pre-implantation development

Non-invasively evaluating gene expression products in human pre-implantation embryos remains a significant challenge. Here, we develop a non-invasive method for comprehensive characterization of the extracellular RNAs (exRNAs) in a single droplet of spent media that was used to culture human in vitro fertilization embryos. We generate the temporal extracellular transcriptome atlas (TETA) of human pre-implantation development. TETA consists of 245 exRNA sequencing datasets for five developmental stages. These data reveal approximately 4,000 exRNAs at each stage. The exRNAs of the developmentally arrested embryos are enriched with the genes involved in negative regulation of the cell cycle, revealing an exRNA signature of developmental arrest. Furthermore, a machine-learning model can approximate the morphology-based rating of embryo quality based on the exRNA levels. These data reveal the widespread presence of coding gene-derived exRNAs at every stage of human pre-implantation development, and these exRNAs provide rich information on the physiology of the embryo.

Long-term storage modifies the microRNA expression profile of cryopreserved human semen

The global practice of cryopreservation of human semen is commonplace in Assisted Reproductive Technology (ART) labs and sperm banks. However, information on the effects of long-term cryopreservation on semen is limited to clinical data summaries and descriptions. For this study, we prepared 4 semen specimens of fresh semen, 4 specimens cryostored for at least 1 year, 3 specimens cryostored for at least 5 years, 4 specimens cryostored for at least 10 years, and 3 specimens cryostored for at least 15 years. Total RNA was extracted from each sample, amplified, labeled, and mapped to the known primary microRNA (miRNA) in the miRBase database, enabling the prediction of novel miRNAs. We found that cryopreservation can lead to changes in miRNA expression, and with the increase in storage time, these changes became more pronounced. Meanwhile, the expression of let-7d-3p, let-7c-5p and let-7i-3p miRNAs changed dynamically over cryostorage time in frozen-thawed human sperm. Furthermore, we analyzed the time-dependent dynamics of cryostorage-expressed miRNAs and their target mRNAs and found that half of the target genes were expressed in oocytes. These intersection genes were mainly enriched in cancer and cytoskeletal signaling pathways. Our findings showed that the miRNA expression profile of cryopreserved human semen is modified by long-term storage. Furthermore, as the storage time increases, the impact on human sperm becomes more pronounced in terms of miRNAs, which may have an effect on subsequent fertilization and embryonic development.

Assessing the endometrium: An update on current and potential novel biomarkers of receptivity

A cyclical evolvement of the endometrium into a transient state of receptivity is crucial for acceptance of the semi-allogeneic foetus, conducive to pregnancy. Despite documentation of aberrances in this process within patients experiencing repeated embryo implantation failures and miscarriages, the endometrium is often overlooked in IVF clinics as the cause for failure. Focus instead is usually given to embryo-derived factors, such as aneuploidy. Nevertheless, failure of approximately 30 % of euploid embryos to implant demonstrates that other factors such as the endometrium require clinical exploration. Here, we review both traditional and novel methods used to assess endometrial receptivity such as identifying the WOI, endometrial immune profiling and transcriptomics panel testing. Where reported, we will also discuss their clinical application, as well as novel potential biomarkers within the pre-clinical research stages which show promise in their ability to assess endometrial receptivity.

A validated model for individualized prediction of pregnancy outcome in woman after fresh cycle of Day 5 single blastocyst transfer

The association between the embryo quality, clinical characteristics, miRNAs (secreted by blastocysts in the culture medium) and pregnancy outcomes has been well-established. Studies on prediction models for pregnancy outcome, using clinical characteristics and miRNA expression, are limited. We aimed to establish the prediction model for prediction of pregnancy outcome of woman after a fresh cycle of Day 5 single blastocyst transfer (Day 5 SBT) based on clinical data and miRNA expression. A total of 86 women, 50 with successful pregnancy and 36 with pregnancy failure after fresh cycle of Day 5 SBT, were enrolled in this study. All samples were divided into training set and test set (3:1). Based on clinical index statistics of enrolled population and miRNA expression, the prediction model was constructed, followed by validation of the prediction model. Four clinical indicators, female age, sperm DNA fragmentation index, anti-mullerian hormone, estradiol, can be used as independent predictors of pregnancy failure after fresh cycle of Day 5 SBT. Three miRNAs (hsa-miR-199a-3p, hsa-miR-199a-5p and hsa-miR-99a-5p) had a potential diagnostic value for pregnancy failure after Day 5 SBT. The predictive effect of model combining 4 clinical indicators and 3 miRNAs (area under the receiver operating characteristic curve, AUC = 0.853) was better than models combining single 4 clinical indicators (AUC = 0.755) or 3 miRNAs (AUC = 0.713). Based on 4 clinical indicators and 3 miRNAs, a novel model to predict pregnancy outcome in woman after fresh cycle of Day 5 SBT has been developed and validated. The predictive model may be valuable for clinicians to make the optimal clinical decision and patient selection.

Potential Function of Testicular MicroRNAs in Heat-Stress-Induced Spermatogenesis Disorders

Spermatogenesis is temperature-dependent, and the increase in testicular temperature seriously affects mammalian spermatogenesis and semen quality. In this study, the testicular heat stress model of mice was made with a 43 °C water bath for 25 min, and the effects of heat stress on semen quality and spermatogenesis-related regulators were analyzed. On the 7th day after heat stress, testis weight shrank to 68.45% and sperm density dropped to 33.20%. High-throughput sequencing analysis showed that 98 microRNAs (miRNAs) and 369 mRNAs were down-regulated, while 77 miRNAs and 1424 mRNAs were up-regulated after heat stress. Through gene ontology (GO) analysis of differentially expressed genes and miRNA-mRNA co-expression networks, it was found that heat stress may be involved in the regulation of testicular atrophy and spermatogenesis disorders by affecting cell meiosis process and cell cycle. In addition, through functional enrichment analysis, co-expression regulatory network, correlation analysis and in vitro experiment, it was found that miR-143-3p may be a representative potential key regulatory factor affecting spermatogenesis under heat stress. In summary, our results enrich the understanding of miRNAs in testicular heat stress and provide a reference for the prevention and treatment of heat-stress-induced spermatogenesis disorders.

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.

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.