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Ultra-rapid freezing of very low numbers of sperm using cryoloops
Timothy G Schuster1, Laura M Keller, Rodney L Dunn
1Department of Urology, University of Michigan, Ann Arbor, MI 48109, USA.
Background:
With the availability of ICSI, men with severe oligozoospermia (<5x10(6)/ml) are able to reproduce. Current methods for cryopreservation of severe oligozoospermic samples are labour intensive and costly. The objective of this study was to evaluate whether freezing small numbers of motile sperm (approximately 100) was feasible using cryoloops.
Methods:
Initial tests assessed the effect of various dilutions of cryoprotectants on pre-freezing sperm motility. Several solutions were further evaluated for their ability to cryoprotect sperm during ultra-rapid freezing. Sperm were placed on cryoloops and held in liquid nitrogen vapour for 5 min prior to freezing (ultra-rapid freezing) or directly submerged into liquid nitrogen. Using the optimal cryoprotectant and technique from these experiments, ultra-rapid and standard slow-rate freezing protocols were compared.
Results:
Optimal sperm survival was seen when sperm in cryoloops were placed in liquid nitrogen vapour in test yolk buffer with 12% v/v glycerol versus other cryoprotectants. Using this cryoprotectant, post-thaw sperm motility is comparable between ultra-rapid and slow-rate freezing methods.
Conclusion:
Ultra-rapid freezing of very low numbers of sperm is feasible using cryoloops suspended in liquid nitrogen vapour for 5 min.
Insights
Ultra-rapid freezing of low sperm counts is now feasible using cryoloops. This method, involving liquid nitrogen vapor, offers a cost-effective alternative for sperm cryopreservation in severe oligozoospermia cases.
Area of Science:
- Reproductive Biology
- Cryopreservation Technology
- Andrology
Background:
- Intracytoplasmic sperm injection (ICSI) enables reproduction for men with severe oligozoospermia.
- Current cryopreservation methods for low sperm counts are costly and labor-intensive.
Purpose of the Study:
- To evaluate the feasibility of freezing small numbers of motile sperm (approx. 100) using cryoloops.
- To assess ultra-rapid freezing techniques for severe oligozoospermic samples.
Main Methods:
- Tested various cryoprotectant dilutions for pre-freezing sperm motility.
- Evaluated cryoprotectants for ultra-rapid freezing using cryoloops.
- Compared ultra-rapid freezing with standard slow-rate freezing protocols.
Main Results:
- Optimal sperm survival achieved with cryoloops in liquid nitrogen vapor using test yolk buffer and 12% glycerol.
- Post-thaw sperm motility was comparable between ultra-rapid and slow-rate freezing methods with the optimal cryoprotectant.
Conclusions:
- Ultra-rapid freezing of very low sperm numbers is feasible using cryoloops.
- Cryoloops suspended in liquid nitrogen vapor for 5 minutes provide a viable cryopreservation method.