Low oxygen inhibits but complex high-glucose medium facilitates in vitro maturation of squirrel monkey oocyte-granulosa cell complexes

Purpose: the objectives of these in vitro maturation studies in primate cumulus-oocyte complexes (COCs) were to evaluate the effect of a reduced-oxygen environment and to compare medium with a high-glucose concentration to medium with pyruvate but no glucose. Methods: COCs were retrieved from squirrel monkeys stimulated with 1 mg of follicle-stimulating hormone (FSH) for 4-6 days. Experiment I examined maturation after 48 Hr in 5% O-2/5% CO2/90% N-2 compared with 5% CO2/air. The medium was CMRL-1066 containing moderate glucose (5.5 mM) supplemented with 1 mM glutamine, 0.33 mM pyruvate, 0.075 IU/ml human FSH, 5 IU/ml human chorionic gonadotropin, 75 U penicillin G/ml, and 20% fetal bovine serum. Experiment 2 in 5% CO2/air, compared P-I medium (pyruvate and lactate but no glucose) to Waymouth's medium (27.5 mM glucose), both with identical supplements. Results: Only 3 (8%) of 37 COCs matured in 5% O-2, while 39 (49%) of 80 matured in ambient O-2. Fourteen (22%) of 64 complexes matured in P-I medium, compared to 47 (49%) of 96 meiosis II oocytes in Waymouth's medium (P < 0.05). Conclusions: These are the first primate studies showing detrimental effects of reduced-oxygen culture on in vitro maturation. Additionally, maturation was enhanced with complex high-glucose medium suggesting that the predominant metabolism in aerobic glycolysis.