研究開発・学会発表

Introduction
In vitrification of embryos, a combination of dimethyl sulfoxide (DMSO) and ethylene glycol (EG) has been widely used as cryoprotectant agents (CPA). Although DMSO is one of the most effective CPA, it also has cytotoxicity to embryos. Recently, it was demonstrated that carboxylated poly-L-lysine (PLL), which is classified into a polyampholyte, is shown to be effective for the cryopreservation of cultured cells. In this study, we evaluated the efficacy of PLL on mouse embryos if it could be an alternative to DMSO.

Materials and Methods
In order to assess the effect of PLL on cryopreservation, 145 mice 8-cell embryos and 163 blastocysts recovered from ICR strains were vitrified with 15% DMSO, 10% or 20% PLL containing 20% serum substitute supplement (SSS), 15% EG and 0.5M sucrose. In this study, the survival rate and the developmental rate into blastocysts were assessed in each group. In addition, the numbers of dead cells in each experimental group was counted individually.

Results
The survival and developmental rate of 8-cell embryos vitrified with each solution was 100%. In addition, the ratio of dead cells in each groups showed similar percentage (4.1%, 3.8% and 4.8%). In blastocysts, there was no significant difference in the survival rate (95.0%, 93.0%, and 95.3%) between each group. Finally, the ratio of dead cells in each group showed similar percentage (6.9%, 7.5% and 8.9%).

Conclusion
Our results indicate that PLL has an equivalent potency to DMSO in effectiveness and safety for the vitrification of mouse embryos.