Ultrastructural Deformity of Mouse Oocytes Matured by Ovarian Hyperstimulation or Not.

Abstract

This study was conducted to evaluate whether ovarian hyperstimulation program can secure ultrastructural integrity as well as developmental competence. Oocytes were retrieved from B6CBAF1 mice either after PMSG/hCG injection or not. We subsequently observed ultrastructure with the image from transmission electron microscope. Concomitantly, preimplantation development of oocytes derived from the hyperstimulation or not was monitored after IVF or after parthenogenesis. The hyperstimulation did not reduce developmental capacity of oocytes ovulated in vivo. Regardless of activation methods (IVF or parthenogenesis), significant (39% vs. 30% of total; p=0.0186) increase in mitochondrial deformity to form vacuolated mitochondria was detected after hyperstimulation treatment. Formation of multivesicular bodies was prominently increased after the hyperstimulation (1.44 vs. 4.27; p=0.0221). However, Other microorganelles and ultrastructural parameters such as formation and distribution of mitochondria, cortical granules and microvilli, and development of sERs were not different between the hyperstimulation and natural ovulation groups. In conclusion, ovarian hyperstimulation with PMSG and hCG induces mitochondrial deformity, which follows activation of multivesicular body formation. However, such changes do not alter at least preimplantation development. Although hyperstimulation program can yield better IVM/IVF outcome, care should be taken to further increase embryonic development beyond blastulation. (poster)