Effects of phosphatidylserine and cholesterol liposomes on the viability, motility, and acrosomal integrity of stallion spermatozoa prior to and after cryopreservation.

The study investigates the impact of lipid molecules treatment on the survival, activity, and acrosomal state of horse sperm cells before and after the freezing process. It specifically shows that application of liposomes containing phosphatidylserine (PS) and cholesterol (PSCH) improves sperm movement and viability, without impacting the acrosomal reaction–a vital step in fertilization.

Research Methodology

• The study used computer-assisted motion analyses (CASA) and flow cytometry to evaluate stallion sperm cells both before and after cryopreservation.
• Sperm samples were subjected to three types of pre-treatment: no treatment (labeled as Hepes-buffered medium or SHB), treatment with phosphatidylserine (PS) liposomes, and treatment with liposomes of both PS and cholesterol (PSCH).
• These samples were then diluted in either Hepes-buffered medium (SHB) or a mixture of skim milk and egg yolk (SMEY) and cooled to 5 degrees Celsius.

Findings from the First Experiment

• The first experiment revealed that following cooling to 5 degrees Celsius in SHB, sperm motion parameters were higher for those treated with PS and PSCH.
• Sperm motion parameters were also higher for samples that were diluted in SMEY as compared with those diluted in SHB, meaning, the medium of dilution played a role in preserving sperm motility.

Findings from the Second Experiment

• In a second experiment, the researchers compared motion parameters for sperm subjected to PSCH liposomes pre-treatment and then frozen in either SMEY or a different medium referred to as CO (high salt-skim milk-egg yolk extender).
• The motion characteristics were similar for all sperm samples after cooling to 5 degrees Celsius regardless of the treatment kind or the freezing medium.
• However, post-cryopreservation, the samples treated with PSCH liposomes showed higher percentages of moving sperm cells than untreated samples irrespective of the freezing extender.
• Along with the treatment, the freezing medium again seemed to play a significant role. Samples frozen in the CO medium had a larger percentage of moving sperm cells than those frozen in the SMEY medium.

Findings from the Third Experiment

• The third experiment further examined these treated and cryopreserved sperm cells under a different condition. Sperm cells were exposed to the molecule dilauroylphosphatidylcholine (PC12) to instigate the acrosome reaction, necessary for a sperm cell to successfully fertilize an egg.
• The scores of viable cells were higher for fresh sperm than for cryopreserved sperm, which can be expected given the harsh conditions of cryopreservation.
• However, there was no sign that the treatment with PSCH liposomes had any effect on the sperm’s capability to undergo the PC12 induced acrosome reaction.

Conclusion

• The overall conclusion of this research is that pre-treatment of stallion sperm cells with liposomes containing PS and cholesterol can indeed improve the recovery of active sperm cells after cryopreservation.
• However, this treatment doesn’t seem to influence the acrosome reaction, a necessary event for a sperm cell to fertilize an egg, suggesting that the PSCH liposome treatment specifically aids in preserving structural and motility aspects of the sperm cells during the freezing process without affecting their functionality.