Description and Outcomes of Current Clinical Techniques for Sperm Cryopreservation

Abstract

Nowadays, sperm cryopreservation is strongly recommended in cases of malignancy. Moreover, the use of frozen testicular sperm in azoospermic patients prevents the need for repeated sperm retrieval and optimises scheduling between oocyte and sperm obtainment. Even though cryopreservation of human spermatozoa for assisted reproductive purposes is a widely implemented practice, none of the established freezing and vitrification techniques offer optimal cryosurvival results due to the dramatic impact of cryodamage on sperm cells. This comprehensive review describes the most commonly used sperm cryopreservation techniques in order to establish which of them minimise sperm cryodamage and offer better survival rates. Presently, it is not sufficiently demonstrated that sperm vitrification improves survival significantly more than freezing methods. Slow freezing offers the best survival results when compared to other freezing protocols, and owing to its technical advantages, can be considered as one of the preferred protocols to be easily implemented in assisted reproduction laboratories. Moreover, several studies have suggested that sperm preparation prior to cryopreservation can improve thawed sample quality. However, other authors have demonstrated that freezing the fresh sample and performing semen preparation after thawing gives better results in regard to total motile sperm count and motility. Regarding clinical results, it is well established that similar or even better reproductive outcomes are achieved using frozen testicular sperm in cases of azoospermia or anejaculation. Moreover, the use of frozen semen in cancer patients can help to achieve good fertilisation and pregnancy rates. Finally, the use of frozen sperm is not at all associated with worse post-natal development.

A comprehensive review and update on human fertility cryopreservation methods and tools

“…SF, rapid freezing, and vitrification are sperm cryopreservation methods, discovered during the performance of several cryo-experimental improvements ( 81 , 82 ). SF was developed by Behrman and Sawada and includes progressive sperm cooling in two or three steps, either manually or automatically ( 37 , 83 ).…”

“…Besides the osmolarity, similar importance seems to play the temperature during the thawing/warming process. Sperm vitrification requires the removal of seminal plasma before starting the procedure, while in other sperm freezing techniques, semen removal can be done either before freezing or after thawing ( 82 ). Seminal plasma may contain cell leukocytes or other microorganisms with the ability to promote the production of reactive oxygen species (ROS).…”