Adding cholesterol to the stallion sperm plasma membrane improves cryosurvival

Area of Science:

• Reproductive Biology
• Cryobiology
• Animal Science

Background:

• Cryopreservation of equine sperm causes membrane damage due to phase transitions from fluid to gel states at low temperatures.
• Reduced membrane fluidity during cooling is a primary cause of cryoinjury in sperm cells.
• Supplementing sperm membranes with cholesterol can potentially mitigate cold-induced damage and improve cryosurvival.

Purpose of the Study:

• To determine the optimal concentration of cholesterol-loaded cyclodextrins (CLC) for enhancing equine sperm cryosurvival.
• To evaluate the effect of CLC addition on sperm membrane integrity, fluidity, and post-thaw viability.
• To assess the impact of CLCs on the functional capacity of cryopreserved stallion sperm, specifically zona pellucida binding.

Main Methods:

• Equine sperm were treated with varying concentrations of cholesterol-loaded cyclodextrins (CLC).
• Sperm motility, membrane integrity, and cholesterol content were assessed before and after cryopreservation.
• Post-thaw functional competence was evaluated by measuring sperm binding to zona pellucida of bovine oocytes.

Main Results:

• Addition of 1.5 mg CLC significantly improved post-thaw motility in stallions with poor cryosurvival rates (67% vs. 50%).
• CLCs increased membrane integrity and maintained higher cholesterol levels in sperm membranes after cryopreservation.
• Cryopreserved sperm treated with CLCs showed significantly enhanced binding to the zona pellucida (48 vs. 15).

Conclusions:

• Cholesterol-loaded cyclodextrins (CLC) effectively improve the cryosurvival of equine sperm by maintaining membrane integrity and fluidity.
• Pre-treatment with CLCs enhances post-thaw viability and functional sperm parameters, including zona pellucida binding.
• The addition of CLCs represents a straightforward and effective strategy to increase the success rate of stallion sperm cryopreservation.