Developmental capacities of two-cell mouse embryos frozen by three methods

Area of Science:

• Reproductive Biology
• Cryobiology
• Developmental Biology

Background:

• Efficient cryopreservation is crucial for preserving embryo viability.
• Optimizing freezing protocols for two-cell mouse embryos is essential for reproductive research and assisted reproduction technologies.

Purpose of the Study:

• To evaluate and identify the most efficient freezing protocol for two-cell mouse embryo preservation.
• To compare the efficacy of different cooling rates, thawing methods, and cryoprotective agents.

Main Methods:

• Three freezing protocols were assessed: slow cooling/slow thawing (DMSO), slow cooling/fast thawing (PROH), and ultrarapid freezing/fast thawing (DMSO or PROH).
• Ice nucleation (seeding) was induced manually or automatically in slow-cooling procedures.
• Survival and blastocyst development rates were measured for each protocol.

Main Results:

• Manual seeding significantly improved survival and blastocyst development compared to automatic seeding in slow-cooling methods.
• Slow cooling with fast thawing in 1.5 M PROH and manual seeding yielded high survival (86.2%) and developmental rates (69.0%).
• Ultrarapid freezing with DMSO showed higher rates (84.8% survival, 55.9% development) than with PROH (39.8% survival, 19.4% development).

Conclusions:

• Manual induction of ice nucleation is superior to automated systems for mouse embryo cryopreservation.
• The protocol involving slow cooling, fast thawing, 1.5 M PROH, and manual seeding is the most effective for preserving the developmental potential of two-cell mouse embryos.
• Findings suggest potential applicability to human embryo cryopreservation.