Analysis of correlations between zona pellucida birefringence and molecular markers of oocyte developmental competence

Background Human infertility is the incapacity of a couple to conceive after one year of unprotected sexual intercourse. Selection of the best gametes for subsequent steps of fertilization and embryo transfer was shown to be the crucial step in infertility treatment procedure [1,2]. Oocyte selection using morphological criteria has been the gold standard method in assisted reproductive technologies (ART) clinics. Zona Pellucida (ZP) , a filamentous matrix of glycosylated glycoproteins surrounding the oocyte, is one of these morphological criteria of oocyte selection. In fact, ZP thickness and birefringence was reported to be positively correlated with higher ability of the oocyte to achieve successful pregnancy, but this selection approach has limitations in terms of accuracy, objectivity and constancy. Recent studies using OMICs approaches have identified key molecular markers in somatic cells (cumulus and/or granulosa cells) and follicular fluid that quantitatively and non-invasively predict the oocyte quality for better selection, higher pregnancy rates and efficient infertility treatment. These biomarkers could be a valuable reinforcement of the morphological selection criteria widely used in IVF clinics. In this context, this study was designed to study the relationship between some molecular predictors of oocyte quality found by our group and the conventional morphological parameters of oocyte quality. We expect to find a positive correlation between the ZP birefringence and molecular markers of oocyte competence. Such integrative strategy should lead to a powerful combined approach that will precisely predict the oocyte developmental potential, allowing therefore efficient infertility treatment and elective single embryo transfer (eSET).