high-throughput droplet vitrification of stallion sperm using permeating cryoprotective agents.

This research article discusses an experiment on the vitrification of stallion sperm involving a particular system and mixture of cryoprotective agents (CPAs). The study found that techniques applied, like droplet size, sperm concentration, CPA type and concentration, and exposure time, play a crucial role in the successful vitrification of stallion sperm but resulted in an almost total loss of sperm motility.

Objective and Methodology

• The objective of the experiment was to investigate the feasibility of vitrifying stallion sperm. Vitrification is a technique where the fluid is chilled at such a high speed that it solidifies without forming ice crystals. This was done using a dual-syringe pump system to combine sperm that had been equilibrated in a low concentration CPA solution with a higher concentration CPA solution.
• The resulting mixture was drop-formed into droplets of specific size (~20 µL) and then cooled by being placed onto an aluminum alloy block immersed in liquid nitrogen.
• Mathematical modeling was applied to compute the heat transfer and cooling rate.

CPA Concentration and Droplet Size

• The study intended to identify the minimum CPA concentration required for vitrification. This was done using different CPAs (glycerol, ethylene glycol, propylene glycol, dimethyl sulfoxide) and combinations of these. The effects of droplet size and carrier solution were also a factor in the study.

Vitrification Process

• The vitrification of the sperm was achieved using a 1/1 mixture of glycerol and propylene glycol at a final concentration of 45% in buffered saline supplemented with 3% albumin and polyvinylpyrrolidone. The warming process used a standard diluent supplemented with 100 mM sucrose.
• The research discovered that the sperm concentration had a significant impact on the integrity of the sperm membrane after the vitrification and warming process was completed.

Results and Conclusion

• The results showed a decrease in sperm membrane integrity with higher sperm concentrations. For instance, it was 21 ± 12% for 10 × 10 sperm mL and 54 ± 8% for 1 × 10 sperm mL.
• Despite successfully achieving vitrification, a near-total loss of sperm motility was observed. In conclusion, the experiment demonstrated that successful sperm vitrification requires a delicate balance between factors such as droplet size, sperm concentration, CPA type and concentration, and exposure time.