Systematic review of mRNA expression in human oocytes: understanding the molecular mechanisms underlying oocyte competence.

The biggest cell in the human body, the oocyte, encloses almost the complete machinery to start life. Despite all the research performed to date, defining oocyte quality is still a major goal of reproductive science. It is the consensus that mature oocytes are transcriptionally silent although, during their growth, the cell goes through stages of active transcription and translation, which will endow the oocyte with the competence to undergo nuclear maturation, and the oocyte and embryo to initiate timely translation before the embryonic genome is fully activated (cytoplasmic maturation). A systematic search was conducted across three electronic databases and the literature was critically appraised using the KMET score system. The aim was to identify quantitative differences in transcriptome of human oocytes that may link to patient demographics that could affect oocyte competence. Data was analysed following the principles of thematic analysis. Differences in the transcriptome were identified with respect to age or pathological conditions and affected chromosome mis segregation, perturbations of the nuclear envelope, premature maturation, and alterations in metabolic pathways-amongst others-in human oocytes.

A Comparative Analysis of Outcomes Between Two Different Intramuscular Progesterone Preparations in Women Undergoing Frozen Embryo Transfer Cycles.

Background: The purpose of the current study was to assess if luteal support with intramuscular (IM) 17 alpha-hydroxyprogesterone caproate (17-OHPC) (Lentogest, IBSA, Italy) improves the pregnancy outcome in comparison to natural intramuscular progesterone (Prontogest, AMSA, Italy) when administered to recipients in a frozen embryo transfer cycle. Methods: A retrospective comparative study was performed to evaluate outcomes between two different intramuscular regimens used for luteal support in frozen embryo transfer cycles in patients underwent autologous in vitro fertilization (IVF) cycles (896 IVF cycles) and intracytoplasmic sperm injection (ICSI) who had a blastocyst transfer from February 2014 to March 2017 at the Centre for Reproductive and Genetic Health (CRGH) in London. Results: The live birth rates were significantly lower for the IM natural progesterone group when compared to 17-OHPC group (41.8% vs. 50.9%, adjusted OR of 0.63 (0.31-0.91)). The miscarriage rates were significantly lower in the 17-OHPC group compared to the IM natural progesterone group (14.5% vs. 19.2%, OR of 1.5, 95% CI of 1.13-2.11). The gestational age at birth and birth weight were similar in both groups (p=0.297 and p=0.966, respectively). Conclusion: It is known that both intramuscular and vaginal progesterone preparations are the standard of care for luteal phase support in women having frozen embryo transfer cycles. However, there is no clear scientific consensus regarding the optimal luteal support. In this study, it was revealed that live birth rates are significantly higher in women who received artificial progesterone compared to women who received natural progesterone in frozen embryo transfer cycles.

Next Generation Sequencing Detects Premeiotic Errors in Human Oocytes.

Autosomal aneuploidy is the leading cause of embryonic and foetal death in humans. This arises mainly from errors in meiosis I or II of oogenesis. A largely ignored source of error stems from germinal mosaicism, which leads to premeiotic aneuploidy. Molecular cytogenetic studies employing metaphase fluorescence in situ hybridization and comparative genomic hybridisation suggest that premeiotic aneuploidy may affect 10-20% of oocytes overall. Such studies have been criticised on technical grounds. We report here an independent study carried out on unmanipulated oocytes that have been analysed using next generation sequencing (NGS). This study confirms that the incidence of premeiotic aneuploidy in an unselected series of oocytes exceeds 10%. A total of 140 oocytes donated by 42 women gave conclusive results; of these, 124 (88.5%) were euploid. Sixteen out of 140 (11.4%) provided evidence of premeiotic aneuploidy. Of the 140, 112 oocytes were immature (germinal vesicle or metaphase I), of which 10 were aneuploid (8.93%); the remaining 28 were intact metaphase II - first polar body complexes, and six of these were aneuploid (21.4%). Of the 16 aneuploid cells, half contained simple errors (one or two abnormal chromosomes) and half contained complex errors. We conclude that germinal mosaicism leading to premeiotic aneuploidy is a consistent finding affecting at least 10% of unselected oocytes from women undergoing egg collection for a variety of reasons. The importance of premeiotic aneuploidy lies in the fact that, for individual oocytes, it greatly increases the risk of an aneuploid mature oocyte irrespective of maternal age. As such, this may account for some cases of aneuploid conceptions in very young women.

Chromosomal Analysis of Cumulus Cells as a Future Predictor for Oocyte Aneuploidy: A Case Report.

BACKGROUND: Within the ovary, the optimal growth of the follicle, oocyte maturation and ovulation are highly conditioned by the two-way cross talk and interactions between the oocyte and the immediate somatic cells, known as cumulus cells (CCs). This biological communication between cell lines triggered the interest in the study of CCs as a biomarker of oocyte competence. CASE PRESENTATION: The findings of a 45,X mosaic pattern on CCs from a female patient with unremarkable medical history are reported in this study. The patient came to the Centre for Reproductive and Genetic Health, London on 14th August 2019 for her first visit and the follow up procedures were done for her to determine underlying genetic status. For this purpose, four sources of DNA including CCs, blood lymphocytes, buccal cells and immature oocytes were analyzed in the present report. CONCLUSION: In the present case study, the hypothesis of the female patient being mosaic 45,X was confirmed although the degree of mosaicism and whether this was affecting the germinal line could not be determined. In the event of the discovery of a cell line with an apparently abnormal genetic makeup, genetic counselling is important in order to understand the implications from somatic to germinal cells for patients exploring fertility journeys.

The First ongoing Pregnancy Following Comprehensive Aneuploidy Assessment Using a Combined Blastocenetesis, Cell Free DNA and Trophectoderm Biopsy Strategy.

BACKGROUND: The exact origin of cell-free DNA found in spent culture media or blastocoel fluid is currently unknown but with the potential to become an improved source of DNA for chromosomal analysis than trophectoderm biopsy samples, it provides a superior representation of the fetal genetic status. However, the genetic material contained within the blastocoel cavity may be more reliable to assessment of embryo euploidy in a clinical context than trophectoderm of cell-free DNA. CASE PRESENTATION: This is the first UK case report where all three sources of DNA were analyzed in a clinical setting on 29 th January 2018 at the Centre for Reproductive and Genetic Health, London, leading to an ongoing clinical pregnancy. CONCLUSION: The experience from this case report suggests that removal of blastocoel fluid, sampling of spent culture media and trophectoderm biopsy can be carried out in parallel. Gathering genetic information from two to three independent samples of embryo DNA may provide enhanced diagnostic accuracy and may clarify cytogenetic status of mosaic embryos.

Correction to: Contraction behaviour reduces embryo competence in high-quality euploid blastocysts.

The original version of this article unfortunately contained a mistake in the author group section.