2012 ASRM 68th Annual Meeting
S.Y. Yoon, S.K. Cha, N.J. Yang, J.H. Eum, W.S. Lee, D.R. Lee
Mitochondria have a central role for cell viability and in early mammalian embryogenesis. Asymmetric distribution of mitochondria at pronuclear stage has been associated with asymmetric segregation into different blastomeres might be the reason of abnormal embryonic development. We investigated the possible causes of low blastocyst development of vitrified/warmed oocytes by evaluating the changes of high-polarized mitochondria redistribution.
Materials and methods
Immature GV mouse oocytes were vitrified in EG+ DMSO with an EM grid and slush-nitrogen. We used a milrinone, as phosphodietsterase 3 inhibitor, to block spontaneous germinal vesicle breakdown during oocyte collection and vitrification. The thawed/warmed oocyte were matured in vitro or subjected to test high-polarized mitochondria distribution. In vitro matured MII oocyte were fertilized and cultured in KSOM for 5 days to analyze embryonic development. As high-polarized mitochondria indicator, JC-1was used and monitored with CLSM with Z-stack.
There is no difference in in vitro maturation rate and fertilization rate between fresh and vitrified/warmed immature oocyte. However, the development rate to blastocyst in thawed/warmed oocyte was significantly lower than those in fresh oocyte (P<0.05). It was recovered if these oocytes were incubated in milrinone for more than 3hr for recovery of mitochondria redistribution before oocyte maturation. Most of thawed/warmed oocyte showed low-polarized mitochondrial inner membrane potential, on the other hand, for 3hr incubated oocyte in milrinone recovered to high polarized mitochondria.
Alteration of high polarized mitochondria distribution in vitrified oocyte may affect on mitochondria activity during fertilization and further embryo development.
Supported by: This work was supported by a grant from the Korea Healthcare Technology R&D Project, Ministry for Health, Welfare & Family affairs, Republic of Korea.