The effect of hyaluronan concentrations in hST-supplemented TCM 199 on in vitro nuclear maturation of bitch cumulus–oocyte complexes

In this study, the effect of hyaluronan (HA) on in vitro nuclear maturation of bitch oocytes was evaluated. Cumulus–oocyte complexes (COCs) were cultured for 48 h at 37 °C in a humidified atmosphere of 5% CO2 in air. Oocytes with one or more layers of intact cumulus cells and dark cytoplasm were allocated to the following treatments: (A) TCM 199 supplemented with 25 mM Hepes/L (v/v), with 10% heat inactivated estrous cow serum (ECS), 50 μg/mL gentamycin, 2.2 mg/mL sodium bicarbonate, 22 μg/mL pyruvic acid, 20 μg/mL estradiol, 0.5 μg/mL FSH, 0.03 IU/mL hCG and 1 μg/mL human somatotropin (hST) (control medium), (B) Treatment A + 0.5 mg/mL HA and (C) Treatment A + 1.0 mg/mL HA. Supplementation with HA did not increase the number of oocytes that resumed meiosis. Additionally, there were no differences among treatments in the cumulus cell expansion of oocytes. In conclusion, the addition of HA to hST-supplemented TCM 199 did not improve the in vitro nuclear maturation of bitch oocytes, and therefore appeared to be unsatisfactory as supplement for in vitro maturation (IVM) of canine oocytes.