PARENT SESSION
OVARIAN GERM CELLS AND FERTILITY
Laurel
7:30 AM-10:00 AM

(271) THE EFFECT OF HYALURONIC ACID AND 17-ESTRADIOL DURING IN VITRO MATURATION ON FURTHER DEVELOPMENT OF BOVINE OOCYTES.

Ali, Atef¹, Massicotte, Lyne¹, Sirard, Marc-André¹, ¹ Department of Animal Science, Quebec, Canada

ABSTRACT- The concentration of hyaluronic acid (HA) in follicular fluid is an indicator for estimation of oocyte viability for fertilization. However, little is known of the role of HA during in vitro maturation of bovine oocytes. This study was designed to evaluate the effect of different concentrations of HA ( 0, 1, 4, 8, and 12 mg/ml ) added to the maturation medium on bovine embryo development to the blastocyst stage after 8 days of culture. The effect of combination of 17-estradiol (E₂ 1 mg/ml) and HA on cumulus expansion and subsequent embryo development was studied. After culture, blastocysts were fixed and their cell number determined. Bovine oocytes were matured in synthetic oviduct fluid medium (SOF), fertilized in droplets composed of modified Tyrode lactate medium (under 20% O₂) and cultured (under 7% O₂) in defined conditioned medium in vitro. Data from 3 replicates were analyzed by ANOVA and multiple comparisons were made with Fishers LSD test. Cumulus expansion was never found when HA and E₂ were added to the maturation medium. The inclusion of high concentrations of HA during IVM had a positive effect on the developmental capacity of the oocytes to the blastocysts stage ( 35%± 1.52 and 37% ± 1.15 for HA 8 and 12 mg/ml, respectively ) compared to low concentrations (24% ± 0.88 and 26% ± 0.57 for HA 1 and 4 mg/ml, respectively) or SOF alone with no supplement (29% ± 0.88 ). Furthermore, addition of E₂ to the maturation medium in the presence of HA 8 mg/ml significantly (p<0.0001) increased the blastocyst rate compared to maturation medium alone (46.3% ± 2.02 vs 27% ± 0.33, respectively). Number of cells/blastocyst were not different among treatments (113 ± 10.14, 115 ± 7.21 and 124 ± 11.05, for SOF alone, HA 8 mg/ml and HA 8 mg/ml with E₂, respectively). Our study showed that although SOF alone can support bovine oocyte maturation, a high proportion of morphologically normal blastocyst can be produced from IVM of oocytes cultured in medium containing HA and E₂. These results open the possibility of including HA in culture media to increase the efficiency of in vitro blastocyst production from in vitro-matured bovine oocytes using completely defined condition. We are currently investigating the exact role of HA on the production of bovine embryos.

KEY WORDS: oocyte development, in vitro fertilization, embryo, hyaluronic acid