Cryopreservation Techniques for Human Spermatozoa

Cryopreservation of human spermatozoa underpins a wide spectrum of clinical and research applications, from fertility preservation before gonadotoxic treatments to donor banking and conservation of genetic diversity. Conventional programmable slow freezing and vapour-phase protocols remain standard, relying on stepwise temperature reduction and the use of permeating and non-permeating cryoprotectants such as glycerol, sucrose or dextran to minimise intracellular ice formation and osmotic shock. Emerging vitrification methods employ ultra-rapid cooling to achieve a glassy solid state, thereby reducing ice recrystallisation but demanding precise volume control and specialised carriers. Throughout these procedures, spermatozoa are vulnerable to mechanical and biochemical insults including ice-crystal damage, osmotic stress and oxidative stress mediated by reactive oxygen species, which manifest as diminished motility, viability, alterations in membrane fluidity and compromised DNA integrity. Advances in CPA formulations, antioxidant supplementation and device engineering have incrementally improved post-thaw outcomes, while transcriptomic and epigenetic analyses have begun to elucidate molecular consequences of freeze–thaw cycles. Ongoing research seeks to optimise protocols, balance toxicity and protective efficacy of cryoprotectants, and harmonise clinical practicability with cell safety, thereby enhancing assisted reproduction outcomes globally.

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Cryopreservation Techniques for Human Spermatozoa publication trend

The graph below shows the total number of articles in cryopreservation techniques for human spermatozoa across all publications each year (not limited to Nature Index journals).

Technical terms

Cryoprotectant: A substance such as glycerol, sucrose or dextran added to preserve cells during freezing by reducing ice formation and osmotic stress.

Programmable slow freezing: A controlled-rate cooling protocol that gradually lowers temperature in stages to minimise ice recrystallisation and cellular injury.

Vitrification: An ultra-rapid cryopreservation technique that solidifies samples into a glass-like state without ice crystal formation.

Reactive oxygen species (ROS): Highly reactive molecules generated during cryopreservation that can induce lipid peroxidation, protein oxidation and DNA damage.

Osmotic stress: Cellular stress caused by rapid changes in solute concentration during freezing or thawing, leading to volume fluctuations and membrane perturbation.

References

1. Addition of Vitamin C Mitigates the Loss of Antioxidant Capacity, Vitality and DNA Integrity in Cryopreserved Human Semen Samples. Antioxidants (2024).
2. Restoring Sperm Quality Post-Cryopreservation Using Mitochondrial-Targeted Compounds. Antioxidants (2022).
3. Cryoprotectants-Free Vitrification and Conventional Freezing of Human Spermatozoa: A Comparative Transcript Profiling. International Journal of Molecular Sciences (2022).
4. Cryopreservation of Human Spermatozoa: Functional, Molecular and Clinical Aspects. International Journal of Molecular Sciences (2023).
5. Human sperm vitrification: the state of the art. Reproductive Biology and Endocrinology (2020).
6. Process and Pitfalls of Sperm Cryopreservation. Journal of Clinical Medicine (2017).