155 EFFECT OF CO-CULTURE WITH CUMULUS-DERIVED SOMATIC CELLS DURING IN VITRO MATURATION ON PORCINE CUMULUS–OOCYTE COMPLEXES AND SUBSEQUENT EMBRYONIC DEVELOPMENT AFTER IN VITRO FERTILIZATION

Abstract

The purpose of this study was to investigate the effects of co-culture with cumulus-derived somatic cells (CSC) during porcine in vitro maturation (IVM) and subsequent embryonic development after IVF. The CSC were cultured in Dulbecco's modified Eagle medium for 48 h with various numbers of cumulus-derived somatic cells (0.0, 2.5, 5.0, and 10.0 × 10⁴), and then cultured in TCM-199 for 4 h before the oocytes were added. Cumulus-oocytes complexes from 3- to 6-mm follicles were matured in 500 μL of TCM-199, with eCG and hCG, for 22 h, and then cultured in M199 without hormones for 22 h. Each experiment consisted of at least 4 replicates. Statistical analyses were carried out using SPSS 17.0 software (SPSS Inc., Chicago, IL). Percentage data were compared by one-way ANOVA, followed by Duncan's multiple range test. Data were presented as means ± s.e.m. Differences were considered to be significant if the P-value was 0.05. After IVM, no significant difference (P < 0.05) was observed in nuclear maturation rate among the 0.0, 2.5, 5.0, and 10.0 × 10⁴ groups (88.0 ± 2.37, 81.5 ± 2.17, 87.0 ± 1.98 and 86.0 ± 1.93%, respectively). The 2.5 × 10⁴ group showed a significant (P < 0.05) increase in intracellular glutathione (GSH) levels compared with that of the other groups. Intracellular reactive oxygen species (ROS) levels of mature oocyte in all groups showed no significant differences. The developmental competence of matured oocytes in all groups was evaluated after IVF. The 2.5 and 5.0 × 10⁴ groups showed significantly (P < 0.05) high cleavage rates (60.0 ± 4.7 and 64.52 ± 5.9%, respectively) compared with the 0 and 10.0 × 10⁴ groups (43.15 ± 5.0 and 53.8 ± 5.0%, respectively). The 2.5 × 10⁴ group showed a significantly (P < 0.05) higher BL formation rate (35.7 ± 2.9) than control group (21.0 ± 3.8%, respectively), and higher total cell number (127.25 ± 7.7) compared with the 0 and 10 × 10⁴ groups (89.3 ± 4.0 and 92.6 ± 3.7, respectively). In the analysis of gene expression, IVF-BL derived from the 2.5 and 5.0 × 10⁴ groups showed higher (P < 0.05) mRNA expression of PCNA, which is an essential component of the DNA replication and repair machinery and POU5F1 has been used to evaluate developmental potential in embryos. The 10.0 × 10⁴ group showed higher (P < 0.05) mRNA expression of caspase-3 and Bak as known pro-apoptotic factors, compared with the control group IVF-BL. The results of cortical granules distribution which leads digesting sperm receptor proteins ZP2 and ZP3 to block polyspermy, showed that the 2.5 × 10⁴ group was increased significantly (P < 0.05) compared with the other co-culture groups (13.7 ± 6.1, 29.2 ± 9.5, 18.3 ± 0.8 and 19.52 ± 5.3, respectively). In conclusion, co-culture with 2.5 × 10⁴ cumulus-derived somatic cells during IVM improved the developmental potential of porcine IVF embryos by increasing the intracellular GSH level and distribution of cortical granules during oocyte maturation.

This work was supported, in part, by a grant from the Next-Generation BioGreen 21 Program (No. PJ00956901), Rural Development Administration, and the National Research Foundation of Korea Grant funded by the Korean Government (NRF-2012R1A1A4A01004885, NRF-2013R1A2A2A04008751), Republic of Korea.