Differentially expressed microRNAs in aneuploid preimplantation blastocysts: a systematic review.

Introduction: MicroRNAs are small noncoding genes with gene expression regulatory function. Their emergence as potential diagnostic biomarker for many diseases has gained a specific interest among researchers. Observations of changes in miRNA levels correlating with aneuploidy in early embryos raise the prospective of employing miRNA as biomarkers to assess the embryo quality. Method: To identify and gather the miRNAs with potential link to chromosomal abnormalities in embryos from previous research, we conducted a systematic search using four databases, including Embase, Medline, Web of Science, and Cochrane databases in accordance with PRISMA guidelines. Results: Out of 200 identified records, only seven met the inclusion criteria. Seven miRNAs: miR-19b, miR-517c, miR-518e, miR-522, miR-92a, and miR-106a exhibited persistent downregulation in aneuploid blastocysts in the included studies. These miRNAs are members of important miRNA clusters, associated with abnormal expression in studies on reproductive failure. Pathway analysis revealed their involvement in regulating gene transcription, as well as cell cycle progression and apoptosis. Discussion: The changes detected in the miRNA expression in aneuploid embryos across different studies support the aneuploidy and miRNA relationship and prospect miRNA as a valuable tool for the assessment of embryo quality. Collectively, these observations highlight the role of miRNAs in embryonic development, and their involvement in genetic abnormalities that occur in embryos, such as aneuploidy, indicating their potential implementation to improve the embryo selection and reproductive outcomes.

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.