Abstract:
EXP. 1 aimed to determine the effects of insulin-like growth factor-1 (IGF-1) and the mRNA expression of IGF-1 receptor (IGF-1R) during the in vitro development of cat embryos cultured in groups versus singly. Group embryo culture led to a significantly higher blastocyst development rate compared with single-embryo culture (P<0.05). The poor development of singly cultured embryos coincided with the significantly lower IGF-1R expression in morulae than in group-cultured morulae. IGF-1 (25 or 50 ng/ml) supplementation significantly improved the blastocyst formation rate of single embryos to a level similar to group culture by promoting the morula-to-blastocyst transition. IGF-1 supplementation (25 or 50 ng/ml) of singly cultured embryos upregulated the expression of IGF-1R mRNA in morula-stage embryos to the same level as that observed in group-cultured embryos (without IGF-1). EXP. 2 aimed to examined the influence of EGF and its interaction with insulin liked growth factor-1 (IGF-1) on developmental competence of singly cultured embryos, expression of EGF receptor (EGFR) at various stage of development. EGF promoted blastocyst formation to the level comparable to that of group culture. Expression levels of EGFR were decreased in morulae and blastocysts cultured in the presence of EGF, irrespective culture regimens (group or individual culture). EXP. 3 aimed to investigate the relationships of secreted IGF-1 concentrations on subsequent blastocyst formation and to determine the expression level of genes that related to blastocyst quality (OCT3/4, BCL2, and BAX) in blastocyst embryos which have low or high secreted IGF-1 level on Day 3 compared with in vivo produced blastocyst. Four to eight-cell and morula stage embryos that developed to blastocysts significantly secreted the IGF-1 at higher levels than those did not develop to blastocyst. The expression of OCT3/4, BCL2, and BAX significantly increased in the blastocyst especially from high IGF-1 secretion embryos. EXP. 4 aimed to determine the roles of IGF-1 on the production of reactive oxygen species and the expression of anti-oxidative genes of domestic cat embryos cultured in group or singly. Supplementation of IGF-1 improved blastocyst formation only in singly culture. ROS level was higher in singly cultured embryos supplemented with IGF-1 than those without growth factor (P <0.05). In single culture, supplementation of IGF-1 at 50 ng/ml significantly decreased the expression of GPX1 transcripts compared with others. In group culture, ROS level was decreased in group culture with 50 ng/ml of IGF-1 compared with other treatments (P <0.05). The expressions of GPX1, SOD1 and catalase were also increased group culture with 50 ng/ml of IGF-1 compared with other treatment (P <0.05).
