Promotion of in vitro development of 1-cell mouse embryos with BSA involves localization of active mitochondria to the perinuclear region of embryos at the 2-and 4-cell stages
2008
Oishi, R.(Kyoto Univ. (Japan)) | Imai, H. | Yamada, M.
In this study, we first examined the effect of BSA on in vitro development of ddY strain mouse embryos at the 1-cell to blastocyst stages in EDTA-depleted KSOM medium, referred to as mKSOM, without or with various concentrations of BSA. When cultured in mKSOM without BSA, in most of embryos, developmental arrest occurred at the 2-cell stage and only 4% of embryos developed to the blastocyst stage. However, when cultured in mKSOM with 0.05% BSA, the developmental rate (73%) to the blastocyst stage significantly increased. This result indicates that BSA has a promoting effect on preimplantation mouse embryo development in culture. Next we examined the distribution of active mitochondria in embryos at the 2- and 4-cell stages that developed in vitro or in vivo by Mito Red staining and laser scanning confocal microscopy. In embryos cultured in mKSOM without BSA, active mitochondria mainly localized perinuclear region at early 2-cell stage and then translocated to cortical layer subjacent to the plasma membrane during the period of late 2-cell stage. Majority of active mitochondria in in vivo derived embryos and in embryos cultured with BSA constantly localized perinuclear and intermediate regions of their cytoplasm during 2- to 4-cell stages. In conclusion, it was found that BSA at a very low concentration (0.05%) promotes in vitro development of mouse 1-cell embryos to the blastocyst stage and regulates constant localization of active mitochondria around nuclear and intermediate regions of cytoplasm in embryos at the 2- and 4-cell stages. From the results, it is suggested that there is a functional correlation between local production of energy, ATP with active mitochondria localized around nucleus and successful preimplantation development.
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