O-11: Diverse Effects of Polyunsaturated Fatty Acids on Oocyte Maturation and Development In vitro

Background: Polyunsaturated fatty acids (PUFAs) have been shown to influence fertility and endocrinology of reproduction and metabolic activity in many species. In dairy cows, we and others have shown changes in steroid and metabolic hormones and prostaglandins leading to alteration of ovarian activity and uterine function. These can influence fertility by changes in folliculogenesis cyclicity and ovulation, and influence pregnancy rate by affecting fertilisation, embryo development, embryo quality and implantation rates. It is well known that oocyte nuclear and cytoplasmic maturation is crucial for it cleavage after fertilisation and production of developmentally competent embryos. We have investigated whether the type of PUFA can affect oocyte maturation on bovine oocytes cultured in a serum free condition. Materials and Methods: Oocytes were cultured in the presence or absence of either linolenic acid (ALA; 18:3 n-3) or linoleic acid (LA; 18:2 n-6) during maturation. The rate of cumulus cells expansion, nuclear maturation, expression of extracellular signal-regulated kinases (ERK1 and 2) and Akt in oocytes and the changes in the concentration of cAMP in COCs, and prostaglandins (PGs) in the spent media was analysed. In addition, the developmental potential of oocytes and quality of embryos produced from COCs treated with these PUFAs were compared by analysis of cleavage and blastocyst rates after IVF and assessment of blastocyst quality by DST staining. Results: Treatment of cumulus oocyte complexes (COCs) with ALA did not affect cumulus cells expansion but increased the percentage of oocytes at the MII stage as compared to the control. These oocytes had higher levels of intracellular cAMP at 3 hours of maturation and higher phosphorylation of the extracellular signal-regulated kinases (ERK1 and 2) at the first 6 hours of maturation. No changes were observed in the Akt activation. In the spent media, ALA increased the concentrations of PGE2 and PGF2α, and resulted in higher PGE: PGF ratio compared to control. Oocytes treated with ALA produced higher percentage of cleaved embryos and blastocysts, and better quality embryos containing higher cell numbers and lower apoptosis. Treatment of COCs with LA inhibited cumulus cells expansion and decreased percentage of oocytes at the MII stage as compared to the control. This group of COCs had lower levels of intracellular cAMP at 6 hours of maturation and lower phosphorylation of the extracellular signal-regulated kinases (ERK1 and 2) at 24 hours of maturation. Akt activation was also lower in LA treated COCs at 6 hours of maturation. In the spent media, LA increased the concentrations of PGE2 (>10X), PGF2α, resulting in very high PGE:PGF ratio compared to the control. LA supplementation to the COCs during maturation also resulted in lower percentage of cleaved embryos and blastocyst rates. Conclusion: The type of PUFA can induce molecular changes leading to altered nuclear and cytoplasmic maturation of the oocytes leading to improvement/ or reduction of developmental potential after fertilisation