microRNAs: Promising Non-Invasive Biomarkers for Early Embryonic Development and Fertility

Infertility is a serious problem in humans and cattle. Current methods, however, do not provide accurate prediction of embryo developmental potential and pregnancy success. In both humans and cattle, the current method of determining embryo quality in in-vitro fertilization (IVF) setting is through morphological grading. Recent studies have shown that microRNAs (miRNA) can be identified in blood and other human body fluids; therefore can be used as biomarkers for several diseases including cancer. miRNAs are small non-coding RNAs that regulate activity of genes involved in development, differentiation, apoptosis, and proliferation. However, it is not known whether or not miRNAs can be detected in the culture of cattle and human embryos. We hypothesized that miRNAs can be found in culture media of bovine embryos and that the expression of these RNAs can be used as a measure of embryo quality. To test this hypothesis, three biological replicates of embryos and culture media were obtained utilizing an IVF system. Small RNAs were extracted from embryos and culture media and small-RNA library was constructed and sequenced using the Illumina GAIIx. A paired t-test was carried out across the samples of the three replicates. Analysis revealed 11 miRNAs that were differentially expressed between degenerate and blastocyst conditioned media. The miRNA differentially expressed were all more highly expressed in degenerate media compared to blastocyst media. Functional analysis using miRNA mimics and inhibitors was performed to validate differentially expressed miRNAs.