Vitrification of mouse embryos in two cryoprotectant solutions

Area of Science:

• Reproductive Biology
• Cryobiology
• Developmental Biology

Background:

• Vitrification is a key technique for preserving embryos.
• Optimizing cryoprotective media and protocols is crucial for improving embryo survival rates.
• Different developmental stages of mouse embryos exhibit varying sensitivities to cryopreservation.

Purpose of the Study:

• To compare the efficiency of two different media formulations for mouse embryo vitrification.
• To evaluate the impact of equilibration temperature (room temperature vs. 4°C) on vitrification success.
• To determine the optimal conditions for vitrifying mouse compacted morulae, early blastocysts, and expanded blastocysts.

Main Methods:

• Mouse embryos at compacted morula, early blastocyst, and expanded blastocyst stages were used.
• Embryos were equilibrated in either Rall Equilibration Medium (REM) or Massip Equilibration Medium (MEM) at room temperature or 4°C.
• Vitrification was performed using Rall Vitrification Medium (RVM) or Massip Vitrification Medium (MVM).
• Post-thaw embryo survival and development were assessed after culture.

Main Results:

• Compact morulae vitrified at room temperature showed higher survival with RVM (93%) compared to MVM (66%).
• No significant difference in survival rates was observed for early and expanded blastocysts vitrified at room temperature using either medium.
• Equilibration at 4°C with MVM significantly improved the survival rate of expanded blastocysts (57%) compared to RVM (5%).
• Compact morulae survival after 4°C equilibration was similar between RVM (83%) and MVM (70%).

Conclusions:

• Compact morulae exhibit the highest tolerance to the vitrification process among the studied developmental stages.
• Cooling embryos to 4°C prior to vitrification is not necessary for compact morulae.
• Low-temperature equilibration (4°C) combined with MVM offers a significant improvement in expanded blastocyst survival rates.