Human sperm cryopreservation: overcoming the halving effect

This thesis examines the history, process, current pitfalls and possible improvements in human sperm cryopreservation. Initially, Chapter 1 revealed the lack of cohesiveness in current research, requiring the creation of an extensive list of both human and animal cryopreservation studies to determine the current best commercially available cryoprotectant media and freezing technique - deciding on slow programmed freezing and Quinn’s Advantage™ Sperm Freeze media. Building on this, Chapter 2 compared current isolation techniques and their effectiveness at retaining sperm quality post-freeze. Through the comparison of 40 samples, the electrophoretic sperm separation Felix™ System was concluded to have the best levels of total motility, vitality, lipid peroxidation and DNA integrity. Emphasis is placed on the DNA integrity result, as it was statistically different to all procedures, not just the control and DGC. The next step to improving cryopreservation was the improvement of CPA media; if Quinn’s Advantage™ Sperm Freeze could be improved, then that would validate the creation of a new cryopreservation media. Chapter 3 discovered that Quinns had a lack of antioxidants, halving the samples protection against ROS attack. By adding 0.4 mM Vitamin C, this antioxidant loss was mitigated, and a significant improvement in post-freeze vitality obtained. Chapter 4 built upon this finding, by creating a whole new medium – CCM complete. Comparing it to Quinns post-thaw and isolation by Felix™, CCM produced significantly higher levels of total and progressive motility, vitality and DNA integrity. Overall, Chapters 1 – 4 demonstrate not only that there is room for improvement in human sperm cryopreservation studies, but that these improvements are possible with current chemicals and techniques, making this Thesis an invaluable tool for future research to build from.