Embryotropic Effect of Insulin-Like Growth Factor (IGF)-I and Its Receptor on Development of Porcine Preimplantation Embryos Produced by In Vitro Fertilization and Somatic Cell Nuclear Transfer

摘要

Insulin-like growth factor (IGF)-l is a receptor-mediated autocrine/paracrine growth/survival factor for mammalian embryo development. The present study investigated the temporal expression and regulation of porcine IGF-I receptor (IGF-IR) mRNA and the role of IGF-I on development of porcine in vitro fertilized (IVF) and somatic cell nuclear transfer (SCNT) embryos, As assessed by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR), the level of IGF-IR mRNA expression was highin unfertilized oocytes, 2-cell and 4-cell embryos and gradually decreased in 8-cell embryos, morulae, and blastocysts in both IVF and SCNT series, The IVF or SCNT embryos were cultured with 0, 1, 10, 50, or 100 ng/ml IGF-I for 168 hr. Supplementing with50 ng/ml IGF-I increased blastocyst formation and the number of cells in inner cell masses (ICMs) in both IVF and SCNT embryos, In a second experiment, more blastocysts were obtained when IVF or SCNT embryos were cultured for the first 48 hr or for theentire 168 hr with 50 ng/ml IGF-I compared to culturing without IGF-I for 48 hr or with IGF-I for the last 120 hr or without IGF-I for the entire 168 hr. Treating IVF or SCNT embryos with 50 ng/ml IGF-I significantly up-regulated IGF-IR mRNA compared tountreated control embryos. In conclusion, the present study demonstrated that IGF-IR mRNA is expressed in porcine IVF and SCNT embryos, and that IGF-I improved the developmental competence of IVF and SCNT embryos through its specific receptors.