The effects of canthaxanthin on porcine oocyte maturation and embryo development in vitro after parthenogenetic activation and somatic cell nuclear transfer.

The objective of this study was to examine the effects of canthaxanthin (Cx) treatment during in vitro maturation (IVM) of porcine oocytes on embryonic development after parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT), on intracellular glutathione (GSH) and reactive oxygen species (ROS) levels in mature oocytes, and on gene expression in both PA- and SCNT-derived blastocysts. To determine the optimal effective concentration of Cx, porcine oocytes were cultured in IVM medium supplemented with various concentrations (0, 20, 40 and 80 mu M) of Cx for 22 hr. Compared to other groups, supplementation with 40 mu M Cx significantly improved blastocyst formation rates after PA (p<.05), but no significant differences were observed among groups in total blastocyst cell numbers. Subsequently, oocytes were cultured in IVM medium supplemented with or without 40 mu M Cx. Oocytes treated with 40 mu M Cx showed significantly increased cleavage and blastocyst formation rates after SCNT compared to the control group (p<.05). Moreover, significantly increased intracellular GSH and reduced ROS levels were observed in the Cx-treated group (p<.05). In addition, both PA-and SCNT-derived blastocysts from the 40 mu M Cx-treated group showed significantly increased mRNA expression of Bcl2 and Oct4 and decreased Caspase-3 expression level (p<.05), when compared with the control group. PA-derived blastocysts from the 40 mu M Cx-treated group also exhibited significantly decreased expression of Bax (p<.05). Our results demonstrated that treatment with 40 mu M Cx during IVM improves the developmental competence of PA and SCNT embryos. Improvement of embryo development by Cx is most likely due to increased intracellular GSH synthesis, which reduces ROS levels in oocytes, and it may also positively regulate apoptosis-and development-related genes.