Effects of cryopreservation on the acrosomal status of stallion spermatozoa.

The research examines the impact of cryopreservation on the acrosomal status of stallion spermatozoa, demonstrating that freezing and thawing processes result in significant changes in acrosomal responses and reduced sperm viability.

Research Overview

• The study was designed to understand the effects of cryopreservation or freeze-thawing on equine spermatozoa. Specifically, the focus was on the changes in the acrosomal status. The acrosome is an important part of the sperm cell, as it contains the enzymes that help the sperm to penetrate and fertilize an egg.
• With the use of ejaculates from six stallions, the researchers evaluated the impact of different treatment sets: fresh processing; cooled storage at 4-6 degrees Celsius for 24 hours in a milk-based or lactose-EDTA freezing extender; and, freeze-thawing with lactose-EDTA extender in liquid nitrogen at two different concentrations of spermatozoa.

Methodology

• After each treatment, the sperm samples underwent an incubation in TALP-TEST at 39 degrees Celsius under 5% CO2 for two hours.
• A subsample of the sperm was further exposed to calcium ionophore A23187 for 10 minutes. This substance is typically used to stimulate an acrosomal reaction in sperm, although in this case, it was found to not affect the percentage of acrosome reactions.
• Quality and state of sperm were evaluated using staining techniques with FITC-conjugated Pisum sativum agglutinin, and ethidium homodimer as a nuclear counterstain. Sperm cell viability was assessed with the aid of Hoechst 33258 – a staining technique usually used to detect cell viability.

Findings

• Results showed that samples frozen in lactose-EDTA extender in liquid nitrogen at both 5 x 10(7) and 2 x 10(8) spermatozoa ml(-1) concentrations, had more spermatozoa exhibiting intermediate acrosomal staining than any other treatment, indicating a different rate or mode of acrosome reactions in these samples.
• The percentage of cells exhibiting acrosomal reaction was overall higher in these samples, while the proportion of viable cells was the lowest.
• In comparison, semen stored in either a milk-based or lactose-EDTA freezing extender exhibited a lower percentage of viable cells than fresh semen.

Conclusion

• The study concluded that the freeze-thawing process introduces significant changes in the acrosomal status of equine sperm cells, potentially interfering with their ability to successfully fertilize an egg.
• Moreover, the process led to a significant decrease in the viability of sperm cells. These findings provide essential insights into the effects of cryopreservation on sperm quality, which is useful for practitioners in animal reproduction and for further research into fertility preservation methods.