Oocyte In Vitro Maturation Does Not Adversely Affect The Progression Of The First Meiotic Division.

Immature oocytes account for 15% of all oocytes collected and are usually discarded during IVF. There is little information on the aneuploidy frequency of in vitro matured (IVM) oocytes derived from young fertile women, and a standardized protocol enabling effective IVM is lacking. Our study aimed to: 1. Assess whether the addition of autologous cumulus cells (CCs) improves IVM rates; 2. Perform a comprehensive analysis of aneuploidy frequency and type in oocytes cultured in the presence or absence of autologous cumulus cells (CCs) during IVM. This is a prospective randomized study including 390 oocytes [116 metaphase II (MII) and 274 immature oocytes] from 91 donors undergoing ovarian stimulation in one clinic between March-July 2019. The immature oocytes underwent IVM in the presence (n=137) or absence of CCs (n=137) according to a randomization plan. The MII oocytes served as a control for the IVM groups. Oocyte donors (mean age 25.57 ± 4.47) had a normal karyotype and did not have fertility problems. Biopsy of the 1st polar body (PB) was performed directly after denudation for MII oocytes, or after IVM for immature ones. IVM took place in a time-lapse incubator until 1st PB extrusion, or for 50 hours. CC suspension (1ul) was added to the culture well of 137 of the immature oocytes. The cytogenetics of oocytes and their 1st PBs was examined via a well-validated next generation sequencing (NGS) strategy. Our sample size calculation indicated that 74 MII were required per group (with an Alpha risk of 5%, a Beta risk of 20%) to reach statistical significance. CC co-culture did not enhance IVM rates. Overall, 62.77% of oocytes co-cultured with CCs matured to MII, compared with 71.53% of oocytes cultured without CCs. A significantly higher number of mature MII oocyte-PB pairs (86.28%) yielded NGS results, compared to the IVM pairs (77.90%, P = 0.01). Reciprocal results between oocyte and their 1st PBs were obtained for most (77.84%) of the samples. A similar euploidy rate was observed for the MII oocytes (81.97%), and the IVM oocytes cultured in the presence (80.00%) or absence (85.42%) of CCs. Abnormalities resulting from loss or gain of whole chromosomes or of individual chromatids occurred at a similar rate for MII and IVM oocytes. Our data suggest that CC supplementation does not enhance IVM. The IVM process does not seem to affect the accuracy of the first meiotic division and there were no statistical differences observed in the various types of meiotic error. Since DNA degradation is one of the principle reasons for failure of NGS analyses, the lower proportion of IVM oocytes/PBs that yielded results during this study may indicate reduced DNA integrity following IVM, a possibility that warrants further investigation. To our knowledge, this is the largest study employing NGS to provide a definitive insight into the chromosome constitution of IVM oocytes.