Simple vitrification for small numbers of human spermatozoa

Area of Science:

• Reproductive Biology
• Cryobiology
• Spermatozoa Preservation

Background:

• Conventional freezing methods are unsuitable for testicular spermatozoa due to low numbers and poor motility.
• Existing containers pose challenges for cryopreserving limited quantities of spermatozoa.

Purpose of the Study:

• To develop and evaluate a vitrification method for small numbers of spermatozoa using the Cell Sleeper container.
• To assess the impact of droplet volume and oil coverage on sperm parameters during vitrification.

Main Methods:

• Vitrification of spermatozoa in varying droplet volumes (0.5 µL vs. 3.5 µL) with and without oil coverage.
• Cooling in liquid nitrogen vapor followed by storage in a cryotank.
• Comparison of sperm recovery, motility, and viability rates using the Cell Sleeper versus CryoTop.

Main Results:

• Sperm motility significantly improved with oil-free vitrification (P < 0.05).
• Vitrification in 3.5 µL droplets yielded a higher viable sperm rate (72.0%) compared to 0.5 µL droplets (38.0%; P < 0.01).
• The Cell Sleeper demonstrated comparable recovery, motility, and viability rates to the CryoTop.

Conclusions:

• The Cell Sleeper is a highly effective tool for cryopreserving small numbers of spermatozoa.
• This method allows for quick and simple vitrification of limited cells without significant loss.
• The Cell Sleeper offers a promising alternative for testicular sperm cryopreservation.