The effect of minimal concentration of ethylene glycol (EG) combined with polyvinylpyrrolidone (PVP) on mouse oocyte survival and subsequent embryonic development following vitrification
Vitrification techniques employ a relatively high concentration of cryoprotectant in vitrification solutions. Exposure of oocytes to high concentrations of cryoprotectant is known to damage the oocytes via both cytotoxic and osmotic effects. Therefore, the key to successful vitrification of oocytes is to strike a balance between the usage of minimal concentration of cryoprotectant without compromising their cryoprotective actions.
The minimal concentration of ethylene glycol (EG) on mouse oocyte survival and subsequent embryonic development was evaluated following vitrification-warming and parthenogenetic activation. Polyvinylpyrrolidone (PVP) combined with EG on mouse oocyte survival and subsequent embryonic development as well as morphology of the spindle and chromosome alignment were also evaluated. Vitrification system was adapted with JY Straw and the cooling rate was approximately 442–500 °C/min. In contrast, the warming rate was approximately 2,210–2,652 °C/min.
Survival rate of oocytes increased significantly when 15 % EG was combined with 2 % PVP in vitrification solution (VS). The effect of combination of EG and PVP was not significant when the concentration of EG was 20 % and higher. Although there were no significant differences in embryonic development, the percentage of abnormal spindle and chromosome alignment was significantly higher in the oocytes without 2 % PVP in VS.
Our data provide a proof of principle for oocyte vitrification that may not require a high concentration of cryoprotectant. There are synergic effects of EG combined with PVP for oocyte vitrification, which may provide important information to the field in developing less cytotoxic VS.
KeywordsVitrification Cryoprotectant Concentration Oocytes Embryonic development
We thank Dr. Bao-Zeng Xu for technical assistance for immune-fluorescent staining of tubulin and chromosomes. YW was supported by the Key Program for Basic Research of the Science and Technology Commission of Shanghai Municipality, China (Grant No. 12JC1405800).
YW performed the experiments and analyzed data. OO performed the experiment of measuring cooling and warming rates. XMZ, YS assisted the experiments and helped to analyze the data. WD designed study, analyzed the experiments. RCC designed study, analyzed the experiments, and wrote the manuscript.
This study was supported by McGill Reproductive Center, McGill University Health Center (MUHC) and a grant from China Natural Science Foundation (No. 81270746) to RCC.
Conflict of interest
YW, OO, XMZ, YS, WD have nothing declared. RCC designed and invented JY Straw.
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