A new strategy in selecting oocytes using cumulus cells analysis of specific molecules of the apoptotic pathway, according to the ability to reach blastocyst stage.

Abstract

Study question: The aim of the research was to investigate the apoptosis rate of individual cumulus cell–oocyte complexes (COC), associated to the level of p-Akt, to verify the difference between oocytes who produce embryos able to reach the blastocyst stage compared with embryos arrested during the in vitro colture. Summary answer: It was demonstrated that DNA fragmentation in cumulus cells was remarkably lower in patients who achieved a pregnancy after ICSI cycles, related to the quality of oocytes and embryos. Akt pathway plays a critical role in the regulation of cell survival, and most growth factors activate this pathway. What is known already: Studies on oocyte maturation have shown the importance of LH-induced activation of the epidermal growth factor (EGF)-like growth factors. This can be a potential mechanism for transducing the LH signal to oocyte. It is known that LH is an anti apoptotic agent. It is unknown the relationship between apoptosis and Akt in cumulus cell. Akt has been reported to coexist in a multimolecular complex containing also ribosomal S6 kinase 1 and phosphoinositide-dependent kinase 1. Study design, size, duration: The study had the duration of 24 month. 53 patients were involved after informed consent. In this prospective and randomized study, it has been measured the DNA fragmentation rate and the level of p-Akt in cumulus cells of single cumulus-oocyte complex (COC) for each follicle containing a mature oocyte. Participants/materials, setting, methods: Normo-responder patients have been selected. DNA fragmentation rate in cumulus cells has been examined with the use of a TUNEL assay in situ. p-Akt has been examined by immunological assay in situ. Statistic of molecule expression and DNA fragmentation was tested through the repeated measures ANOVA test of log-transformed variables. Main results and the role of chance: Out of 255 MII oocytes, 197 were fertilized and the derived embryos had the following evolution: 117 completed the development to blastocyst (day 5or 6) and were transferred, 57 were vitrified at blastocyst stage and 23 were arrested during in vitro culture at different stage of cleavage. We found a statistical difference between the DNA fragmentation rate of cumulus cells between the arrested embryos compared to the transferred and vitrified blastocysts (p=0.004), confirming that cumulus apoptotic rate of the cumulus cells could be considered as a marker of oocyte competence. Likewise we a found statistical significance between oocytes resulting in transferred blastocyst and arrested embryos in the ratio p-AKT/TUNEL (p=0.043); Therefore, the ratio p-AKT/TUNEL could be considered also a marker of oocyte quality. Limitations, reasons for caution: More studies are needed to confirm these data and to determine the how these molecular pathways are involved on the oocyte competence. Wider implication of the findings: We found that in the cumulus cells of the oocytes able to produce blastocysts apoptosis is significantly lower and the p-AKT/TUNEL ratio is higher than in cumulus cells of arrested embryos, indicating that DNA fragmentation is lower when p-AKT is higher. Data seems to demonstrate that DNA fragmentation rate and p-AKT value in cumulus cells could be considered a molecular marker of oocyte competence, to evaluated as a prognostic pattern of blastocyst formation. Study funding/competing interest: Research awarded by “Grant for fertility innovation 2012” Trial registration number : The trial is an observational study and no registration is needed.