Semen cryopreservation
Semen cryopreservation (commonly called sperm banking or sperm freezing) is a procedure to preserve sperm cells. Semen can be used successfully indefinitely [citation needed] after cryopreservation. It can be used for sperm donation where the recipient wants the treatment in a different time or place, or as a means of preserving fertility for men undergoing vasectomy or treatments that may compromise their fertility, such as chemotherapy, radiation therapy or surgery. It is also often used by trans women prior to medically transitioning in ways that affect fertility, such as feminizing hormone therapy and orchiectomies.
Freezing
The most common cryoprotectant used for semen is glycerol (10% in culture medium). Often sucrose or other di-, trisaccharides are added to glycerol solution. Cryoprotectant media may be supplemented with either egg yolk or soy lecithin, with the two having no statistically significant differences compared to each other regarding motility, morphology, ability to bind to hyaluronate in vitro, or DNA integrity after thawing.[1]
Additional cryoprotectants can be used to increase sperm viability and fertility rates post-freezing. Treatment of sperm with heparin binding proteins prior to cryopreservation showed decreased cryoinjury and generation of ROS.[2] The addition of nerve growth factor as a cryoprotectant decreases sperm cell death rates and increased motility after thawing.[3] Incorporation of cholesterol into sperm cell membranes with the use of cyclodextrins prior to freezing also increases sperm viability.[4]
Semen is frozen using either a controlled-rate, slow-cooling method (
Thawing
Thawing at 40 °C seems to result in optimal sperm motility. On the other hand, the exact thawing temperature seems to have only minor effect on sperm viability, acrosomal status, ATP content, and DNA.[6] As with freezing, various techniques have been developed for the thawing process, both discussed by Di Santo et al.[7]
Refreezing
In terms of the level of sperm
Effect on quality
Some evidence suggests an increase in
In long-term follow-up studies, no evidence has been found either of an increase in
See also
- Cryopreservation of animal genetic resources § Semen
- Frozen bovine semen
- Oocyte cryopreservation