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.