217 EFFECTS OF PORCINE GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR ON PORCINE IN VITRO-FERTILIZED EMBRYOS

Abstract

The cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) is expressed in the female reproductive tract and is one of the regulatory molecules that mediate maternal effects on the growth and development of pre-implantation embryos in several species. The objective of the present study was to investigate the effects of porcine GM-CSF (pGM-CSF) on the developmental potential of porcine IVF embryos. All experiments were performed with zygotes that were produced in vitro and cultured in porcine zygote medium-3–polyvinyl alcohol-based medium. Data were analysed with PASW statistics-17 (SPSS Inc., Chicago, IL) using Duncan’s multiple range test. A total 865 zygotes in 4 replicates were used with different concentrations of pGM-CSF (0, 2, 10, 100 ng mL^–1) in Experiment 1. It was demonstrated that 10 ng mL^–1 of pGM-CSF could increase (15.1 ± 2.2) blastocyst development significantly (P < 0.05) compared with the control (6.1 ± 0.7). There was no effect on cleavage rate. In blastocyst formation, early and expanded blastocysts were significantly (P < 0.05) higher in the 10 ng mL^–1 of pGM-CSF group compared with the control. In Experiment 2, a total 839 zygotes with at least 5 replicates in each group were used, and whether pGM-CSF would act to increase blastocyst yield before or after Day 4 development was tested. Zygotes were cultured with the following treatments: 1) zygotes cultured with fresh porcine zygote medium–polyvinyl alcohol medium from Days 0 to 7 post-insemination as a control; 2) medium supplemented with 10 ng mL^–1 of pGM-CSF from Days 0 to 4 followed by no pGM-CSF from Days 4 to 7; 3) medium alone from Days 0 to 4 followed by supplementation with 10 ng mL^–1 of pGM-CSF from Days 4 to 7; and 4) medium supplemented with 10 ng mL^–1 of pGM-CSF from Days 0 to 7. As compared with the controls (7.8 ± 0.7), pGM-CSF influenced the percentage of blastocyst formation when pGM-CSF was added from Days 4 to 7 (14.6 ± 1.6) or Days 0 to 7 (15.2 ± 1.8), but not from Days 0 to 4 (8.7 ± 1.5). Similarly, the early blastocyst formation rates were significantly higher in the Day 4 to 7 culture period compared with the control, and expanded blastocyst formation was significantly higher in the Day 4 to 7 and Day 0 to 7 culture periods. There was no significant different in cleavage rate among these groups. In conclusion, these data suggest that supplementation of pGM-CSF in in vitro culture medium at Days 4 to 7 or Days 0 to 7 promotes the developmental potential of porcine IVF embryos.