The effect of L-carnitine supplementation during in vitro maturation on oocyte maturation and somatic cloned embryo development.

The quality of the recipient cytoplasm was reported as a crucial factor in maintaining the vitality of SCNT embryos and SCNT efficiency for dairy cows. Compared with oocytes matured in vivo, oocytes matured in vitro showed abnormal accumulation and metabolism of cytoplasmic lipids. L-carnitine treatment was found to control fatty acid transport into the mitochondrial ß-oxidation pathway, which improved the process of lipid metabolism. The results of this study show that 0.5 mg/ml L-carnitine significantly reduced the cytoplasmic lipid content relative to control. No significant difference was observed in the rate of oocyte nuclear maturation, but the in vitro developmental competence of SCNT embryos was improved in terms of increased blastocyst production and lower apoptotic index in the L-carnitine treatment group. In addition, the pregnancy rate with SCNT embryos in the treatment group was significantly higher than in the control group. In conclusion, the present study demonstrated that adding L-carnitine to the maturation culture medium could improve the developmental competence of SCNT embryos both in vitro and in vivo by reducing the lipid content of the recipient cytoplasm.

Supplementation with kaempferol relieves oxidative stress and enhances development of early bovine embryos in vitro.

Oxidative stress (OS) has been considered the principle cause of developmental failure of early embryos cultured in vitro; therefore, the addition of antioxidants is very important for improving in vitro culture (IVC) systems. Various antioxidants have been tested for IVC systems, but most have exhibited some side effects. Kaempferol (3,5,7-trihydroxy-2-[4-hydroxyphenyl]-4 h-1-benzopyran-4-one, KAE) is a flavonoid with strong antioxidant activity and no obvious side effects. This study explored the effect of KAE on antioxidant capacity and developmental competence of bovine embryos after fertilization. KAE was added to bovine IVC medium and significantly reduced reactive oxygen species (ROS) in 2-, 4- and 8-cell stage embryos and increased blastocyst formation. In addition, the level of H3K9ac was increased, the apoptotic index was reduced and total cell numbers and trophectoderm cell numbers in day 7 blastocysts were increased significantly in KAE-treated embryos compared to control. Expression of the apoptotic gene, Bcl-2, was higher in blastocysts after KAE treatment, while expression of the endoplasmic reticulum (ER) stress genes, Bip and HDAC1, and the pro-apoptotic gene, Bax, were significantly lower in the KAE group. Thus, KAE significantly reduced ROS damage and improved development of IVC bovine embryos.