Relation of Cumulus Cell Status with Single Oocyte Maturity, Fertilization Capability and Patient Age

Background: The production of competent oocytes depends on a bi-directional communication between the oocyte and cumulus cells. The goal of this study was to determine whether simple parameters monitored in cumulus cells from individual human oocytes have any predictive value, and thus correlate with clinically relevant parameters. Methods: 97 cumulus-oocyte complexes were recovered from 31 patients undergoing ICSI treatment. After the oocytes were denuded, cumulus cell density from individual oocytes was determined. Cells were probed for viability using propidium iodide and for apoptosis by Annexin V staining or by monitoring caspase activity. These parameters were correlated with oocyte status, fertilization ability and patient age (≤29 years old and ≥30 years old). All variables were checked for normal distribution and then compared by Kruskal-Wallis, Mann-Whitney or one-way ANOVA tests. Results: Mature oocytes were surrounded by more cumulus cells (16073±2595, p=0.026), which were also more viable and less apoptotic than atretic or degenerated oocytes. Mature oocytes that fertilized had higher caspase activity in the surrounding cumulus cells than those that did not fertilize. Younger patients presented lower cumulus cells density (8882±2380 vs. 15036±2143 cells; p=0.034); and cumulus cells had higher apoptosis levels in younger patients than older ones (6775.5±1831.6 RLU vs. 2591±46.5 RLU, p=0.002 for caspase activity). Conclusion: The data suggests that high density and apoptosis of cumulus cells are promising parameters to indirectly predict individual oocyte status. Although more studies and a larger data set are needed, cumulus cells presented the potential to be used as simple predictors of female fertility and/or ovarian ageing.