Supplementation with spermine during in vitro maturation of porcine oocytes improves early embryonic development after parthenogenetic activation and somatic cell nuclear transfer

Spermine plays an important role in protection from reactive oxygen species (ROS) in bacteria, yeast, and mammalian cells, but there are few studies on the effects of spermine on porcine oocyte maturation and subsequent embryo development. The aim of this study was to determine the effects of spermine on in vitro maturation (IVM) of porcine oocytes and their developmental competence after parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT). We evaluated nuclear maturation, intracellular glutathione (GSH), and ROS levels in oocytes, and their subsequent embryonic development, as well as gene expression in mature oocytes, cumulus cells, and PA blastocysts. After treatment with various concentrations of spermine in IVM culture medium, there was no significant difference in nuclear maturation rate. However, spermine treatment groups (10-500 mu M) showed significantly increased intracellular GSH levels and decreased ROS levels compared to the control (P < 0.05). Furthermore, 10 mu M spermine supported significantly higher blastocyst formation rates after PA than the control group (P < 0.05). According to the optimal condition from the PA results, we investigated the effects of 10 mu M spermine on SCNT, and it also significantly improved blastocyst formation rates compared with the control group (P < 0.05). In evaluating the effects of 10 mu M spermine on gene expression, there was significantly lower expression of a proapoptotic gene (Bax) and higher expression of an antiapoptotic gene (Bcl2) in cumulus cells (P < 0.05). FGFR2 was increased in spermine-treated oocytes. Levels of transcription for POU5F1 and Bcl2 were significantly increased in PA blastocysts. In conclusion, 10 mu M spermine supplementation during IVM improved the development of porcine PA and SCNT embryos by increasing intracellular GSH, scavenging ROS levels, and regulating gene expression.