Sphingosine-1-Phosphate (S1P) analogue Phyto-sphingosine-1-Phosphate (P1P) improves the in vitro maturation efficiency of porcine oocytes via regulation of oxidative stress and apoptosis

Phytosphingosine-1-Phosphate (P1P) is a signaling sphingolipid regulating various physiological activities. Yet, little is known of the effect of P1P in the context of reproduction. As such, we aimed to investigate the influence of P1P on oocyte maturation during porcine in vitro maturation (IVM). Here we report the expression of S1PR1-3 among P1P receptors (S1PR1-4) in cumulus cells and oocytes. When P1P was treated by concentrations 10 nM, 50 nM, 100 nM, and 1000 nM during IVM, Metaphase II rate was significantly increased in 1000 nM (=1 M) P1P treatment group. Maturation rate improvement by P1P supplementation was only observed in the presence of EGF. Oocytes under the influence of P1P decreased intracellular ROS levels yet did not show significant differences in GSH levels. In our molecular studies, P1P treatment up-regulated gene expressions involved in cumulus expansion (Has2 and EGF), antioxidant enzyme (SOD3 and Cat), and developmental competence (Oct4) while activating ERK1/2 and Akt signaling. P1P treatment also influenced oocyte survival by shifting the ratio of Bcl-2 to Bax, while inactivating JNK signaling. We further demonstrated that oocytes matured with P1P significantly displayed not only higher developmental competence (cleavage and blastocyst formation rate), but also greater blastocyst quality (total cell number and the ratio of apoptotic cells) when activated via parthenogenetic activation (PA) and in vitro fertilization (IVF). Despite low levels of endogenous P1P found in animals, exogenous P1P was able to influence animal reproduction as shown by increased porcine oocyte maturation as well as preimplantation embryo development.