300 GANGLIOSIDE IMPROVES MEIOTIC MATURATION AND PREIMPLANTATION DEVELOPMENT OF PORCINE OOCYTES

Abstract

Gangliosides are sialic acid-conjugated glycosphingolipids that are believed to regulate cell differentiation as well as the signals of several signal molecules, including epidermal growth factor receptor (EGFR). These compounds are localised in a glycosphingolipid-enriched microdomain on the cell surface and regulated by the glycosphingolipid composition. However, the role of gangliosides in porcine embryos is not yet clearly understood. Therefore, in this study, the relationship between ganglioside (GD1a) and EGFR activation was investigated during meiotic maturation and further development in porcine oocytes. Porcine oocytes were cultured in the NCSU-23 medium supplemented with or without EGF and GD1a for 44 h. Assessment of meiotic maturation was performed by using aceto-orcein staining method. Also, protein levels in matured oocytes were evaluated by Western blot analysis. After fertilization, presumptive zygotes were cultured in the PZM-3 medium for 6 days. All experiments were repeated more than 3 times. Data were analysed by using Student's t-test and Duncan's multiple range test. The proportion of GV arrested oocytes at 22 h was significantly different between the EGF + GD1a-treated and untreated group (41.6 ± 1.5 v. 25.0 ± 0.0%; P < 0.05). After completion of meiotic maturation (44 h), the proportion of MII was significantly different between the EGF + GD1a-treated and untreated group (89.9 ± 3.6 v. 57.4 ± 5.3%; P < 0.05). Also, expression of EGFR protein in matured porcine oocytes was increased in the presence of EGF and GD1a. After IVF, the percentage of penetrated oocytes was significantly higher in the EGF + GD1a-treated group (89.1 ± 2.3%), resulting in higher than normal pronucleus formation (2PN of 43.1 ± 5.2%). Finally, in result, differences in preimplantation developmental potential were detected between the oocytes that were matured with or without EGF and GD1a (50.4 ± 6.1 v. 27.2 ± 2.7%; P < 0.05). These results suggest that GD1a improves the developmental competence of embryos via enhanced meiotic maturation of porcine oocytes by EGFR activation.