Characterization of miRNAs in the spent media throughout the pre-implantation period using the Affymetrix Genechip miRNA 4.0 array
Distinct miRNA populations have only been detected in spent media (SM) cultured with blastocyst-stage embryos. Therefore, the aim of the study was to globally profile the extracellular microRNA (miRNA) population throughout the pre-implantation period in bovine embryos. Briefly, embryos were in-vitro produced in group culture and SM was collected at the 2-cell, 8-cell, and blastocyst stage of development. Total RNA was extracted from SM and hybridized onto a miRNA microarray. Results show that distinct miRNA populations can be detected in the SM at the 2-cell, 8-cell, and blastocyst stage of development with miRNAs showing stage-dependant and stage-independent expression in SM. In addition, distinct miRNA populations can be identified in the SM cultured with slow-growing and fast-growing embryos at the 2-cell, 8-cell, and blastocyst stage of development. Overall, the findings contribute to the growing body of evidence supporting the use of miRNAs in SM as non-invasive biomarkers of early embryo development.