Abstract

Purpose

To determine the impact of low versus atmospheric oxygen tension during only the pre-maturation phase of biphasic capacitation in vitro maturation.

Methods

The study involved sibling oocytes (532 cumulus-oocyte complexes [COCs] from 20 participants [mean age 29.5 ± 2.5 years]) with polycystic ovary syndrome undergoing CAPA-IVM without gonadotrophins. After oocyte pick-up (OPU), COCs were randomized to undergo pre-maturation under low or atmospheric oxygen, then IVM culture at 20% oxygen. The primary outcome was the oocyte maturation rate. Secondary outcomes included rates of fertilization, blastulation, and good-quality blastocysts. Cumulus cell gene expression was also determined, and glucose and lactate concentrations in spent culture media were analyzed.

Results

Oocyte maturation rates per COC (59.8% vs. 56.1%; p = 0.47) and per patient (61% vs. 55%; p = 0.34) were comparable between the atmospheric vs. low oxygen groups. Fertilization rates were significantly higher in the atmospheric versus low oxygen group; all other embryology outcomes were similar between groups. Significantly different cumulus cell gene expression was seen for LDHA (glucose metabolism; lower in the low oxygen group), CPT1A (lipid shuttle; higher in the low oxygen group), and NDRG1 (hypoxia response; lower in the low oxygen group). Glucose consumption and lactate production were comparable between groups during pre-maturation, but lower in the low oxygen group during IVM.

Conclusions

Overall, although low oxygen tension during CAPA-IVM pre-maturation reduces the number of fertilized oocytes, it does not compromise fertilized oocyte quality or embryological outcomes.