Knockdown of IGF-IR by siRNA injection during bovine preimplantation embryonic development.

This study aimed to assess the efficiency and effects of insulin-like growth factor receptor-1 (IGF-IR) siRNA knockdown during bovine preimplantation embryonic development. In oocytes injected with IGF-IR siRNA, the relative IGF-IR mRNA levels compared to controls were 28% and 46% at 6 and 24 h after injection, respectively. With respect to the injection of IGF-IR siRNA in zygotes, 24 h after injection the relative levels of IGF-IR mRNA and protein in the two-cell embryos were 74% and 78% of those in the controls, respectively. IGF-IR siRNA reduced blastocyst formation (23.2%) compared to siRNA controls (33.0%) and uninjected oocytes (35.4%; P < 0.05) and the number of viable cells per IGF-IR siRNA-treated blastocyst (64 ± 3) was significantly reduced, compared to control siRNA and uninjected blastocysts (81 ± 3 and 116 ± 4; P < 0.01). In conclusion, IGF-IR siRNA knockdown reduces the development of bovine embryos, and microinjection in zygotes can decrease blastocyst cell number.