In vitro maturation of oocytes from stimulated IVF-ICSI cycles using autologous cumulus cell co-culture: A preliminary study

Purpose of the study: In stimulated IVF-ICSI cycles, follicles at different stages of maturation can be aspirated during oocyte pickup. Nowadays, only mature oocytes (metaphase 2 stage) are used and immature oocytes (germinal vesicle and metaphase 1 stages), which are judged unfit for fertilization, are non-used at day 0. In our IVF center, the rate of immature oocytes recovered is around 25%. A significant number of this precious resource is therefore non-used every day in IVF laboratories. The objective of our study was to evaluate the competence of our in vitro maturation autologous coculture method on the maturation and developmental potential of immature oocytes obtained from stimulated IVF-ICSI cycles, in order to obtain additional embryos for the couple as a rescue system to increase the changes of cumulative pregnancy.

Patients and methods: This is a prospective study, carried out in the Reproductive Medicine and Biology Unit of the Amiens-Picardy University Hospital (France). It was included 14 couples, managed in IVF-ICSI in our center, from January to March 2020. Thirty-eight oocytes, identified as immature after cumulus-oocyte complexes (COC) stripping for ICSI, were placed in our in vitro maturation medium with the addition of autologous cumulus cells. Oocytes that had reached the metaphase II stage after a maximum of 36 hours of maturation were microinjected. The fertilization and embryonic development potential of the in vitro matured oocytes were compared to those of 148 in vivo matured "siblings" oocytes from the same oocyte retrieval, and then also compared to those of 127 in vivo matured oocytes from different patients (control group).

Main outcome measure(s): Maturation rate, fertilization rate, early cleavage rate and developmental activity to blastulation rate.

Second outcome measure(s): Embryo quality at cleavage and blastocyst stages, blastulation rate, and useful blastulation rate.

Results: No significant difference was found in the main and secondary criteria of the study compared to the "siblings" in vivo matured oocytes from the same oocyte retrieval. However, a significant difference was obtained on the rate of early cleavage and useful blastulation when our cohort was compared to mature in vivo oocytes from different patients (control group).

Conclusion: This study has shown that after incubation in our in vitro maturation autologous cumulus cell co-culture with cumulus-oocyte cells, immature oocytes recovered during stimulated cycles can give rise to competent oocytes, i.e., capable of being fertilized, of cleaving, and of developing into embryos up to the blastocyst stage. Our study therefore seems to be in the direction of a favorable use of these immature oocytes obtained after stimulated IVF-ICSI cycles. The continuation of this study by including a larger number of oocytes is necessary in order to evaluate the real contribution of this technique in routine.