Semen cryopreservation, also known as sperm banking, involves preserving sperm cells through freezing. Glycerol is commonly used as a cryoprotectant during freezing to help prevent damage to sperm cells. Frozen sperm can remain viable for successful use in fertility treatments indefinitely, with the longest reported storage being 22 years. Cryopreservation allows sperm to be stored and used later for fertility treatments when needed or desired.

1. Semen cryopreservation (commonly called sperm banking) is a procedure to preserve sperm
cells. Semen can be used successfully indefinitely after cryopreservation. For human sperm, the
longest reported successful storage is 22 years.[1]
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.
Contents
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 1Freezing
 2Thawing
 3Refreezing
 4Effect on quality
 5See also
 6References
Freezing[edit]
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.[2]
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. [3]
The addition of nerve growth factor as a cryoprotectant
decreases sperm cell death rates and increased motility after thawing. [4]
Incorporation of cholesterol
into sperm cell membranes with the use of cyclodextrins prior to freezing also increases sperm
viability. [5]
Semen is frozen using either a controlled-rate, slow-cooling method (slow programmable freezing or
SPF) or a newer flash-freezing process known as vitrification. Vitrification gives superior post-thaw
motility and cryosurvival than slow programmable freezing.[6]
Thawing[edit]
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.[7]
As with freezing, various techniques have been developed for the thawing process, both
discussed by Di Santo et al. (2012)[8]
Refreezing[edit]
In terms of the level of sperm DNA fragmentation, up to three cycles of freezing and thawing can be
performed without causing a level of risk significantly higher than following a single cycle of freezing
and thawing. This is provided that samples are refrozen in their original cryoprotectant and are not
going through sperm washing or other alteration in between, and provided that they are separated
by density gradient centrifugation or swim-up before use in assisted reproduction technology.[9]

2. Effect on quality[edit]
Some evidence suggests an increase in single-strand breaks, condensation and fragmentation of
DNA in sperm after cryopreservation. This can potentially increase the risk of mutations in offspring
DNA. Antioxidants and the use of well-controlled cooling regimes could potentially improve
outcomes.[10]
In long-term follow-up studies, no evidence has been found either of an increase in birth
defects or chromosomal abnormalities in people conceived from cryopreserved sperm compared
with the general population.[10]