Human cumulus cells as biomarkers for embryo and pregnancy outcomes

Single-embryo transfer is becoming increasingly common in in vitro fertilization (IVF) treatment as a means of reducing multiple pregnancy rates leading to a higher incidence of medical, perinatal and neonatal complications. Consequently, selecting embryos with the highest implantation potential is of great importance in assisted reproductive technology. To date, the choice of the best embryos to transfer is based on subjective morphological parameters. However, as judged by their subjective aspect, movement towards more sophisticated technologies to select the most competent oocytes and/or embryos with the greatest implantation potential have become available, including emerging 'omics' sciences, such as genomics, transcriptomics, proteomics and metabolomics. In this way, the study of the cumulus cells (CCs) transcriptomic profile offers the opportunity, by a non-invasive method, to predict oocyte and embryo competence because bidirectional traffic between CCs and the oocyte is very important for the acquisition of this competence. Using either RT-PCR or DNA microarrays, some studies have provided evidence for the genes expressed in CCs presenting potential biomarkers to predict embryo quality and pregnancy outcomes. This review provides an overview of the current knowledge about CCs as biomarkers for oocyte and embryo selection under an IVF program.