Semen cryopreservation (commonly called sperm banking or sperm freezing) is a procedure to preserve sperm cells.

Semen Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Semen i ...

can be used successfully indefinitely after

cryopreservation Cryo-preservation or cryo-conservation is a process where Organism, organisms, organelles, cell (biology), cells, Biological tissue, tissues, extracellular matrix, Organ (anatomy), organs, or any other biological constructs susceptible to damage ...

. It can be used for

sperm donation Sperm donation is the provision by a man of his sperm with the intention that it be used in the artificial insemination or other 'fertility treatment' of a woman or women who are not his sexual partners in order that they may become pregnant by hi ...

where the recipient wants the treatment in a different time or place, or as a means of preserving fertility for men undergoing

vasectomy Vasectomy, or vasoligation, is an elective surgical procedure for male sterilization or permanent contraception. During the procedure, the male vasa deferentia are cut and tied or sealed so as to prevent sperm from entering into the urethra and ...

or treatments that may compromise their fertility, such as

chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemotherap ...

radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...

or surgery. It is also often used by transgender women prior to medically transitioning in ways that affect fertility, such as

feminizing hormone therapy Feminizing hormone therapy, also known as transfeminine hormone therapy, is hormone therapy and sex reassignment therapy to change the secondary sex characteristics of transgender people from masculine or androgynous to feminine. It is a comm ...

and orchiectomies.

Freezing

The most common

cryoprotectant A cryoprotectant is a substance used to protect biological tissue from freezing damage (i.e. that due to ice formation). Arctic and Antarctic insects, fish and amphibians create cryoprotectants (antifreeze, antifreeze compounds and antifreeze prot ...

used for semen is

glycerol Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...

(10% in culture medium). Often

sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined ...

or other di-,

trisaccharide ''Trisaccharides'' are oligosaccharides composed of three monosaccharides with two glycosidic bonds connecting them. Similar to the disaccharides, each glycosidic bond can be formed between any hydroxyl group on the component monosaccharides. Even ...

s 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. 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. The addition of nerve growth factor as a cryoprotectant decreases sperm cell death rates and increased motility after thawing. Incorporation of cholesterol into sperm cell membranes with the use of cyclodextrins prior to freezing also increases sperm viability. 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 (from Latin ''vitreum'', "glass" via French ''vitrifier'') is the full or partial transformation of a substance into a glass, that is to say, a non-crystalline amorphous solid. Glasses differ from liquids structurally and glasses po ...

. Vitrification gives superior post-thaw motility and cryosurvival than ''slow programmable freezing''. This current technique, invented by the Japanese, is used in the best centers around the world. It is extremely fast (-23000ºC/min), so as a result it avoids the appearance of small ice crystals, preventing the "knife" effect.

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. As with freezing, various techniques have been developed for the thawing process, both discussed by Di Santo et al.

Refreezing

In terms of the level of sperm

DNA fragmentation DNA fragmentation is the separation or breaking of DNA strands into pieces. It can be done intentionally by laboratory personnel or by cells, or can occur spontaneously. Spontaneous or accidental DNA fragmentation is fragmentation that gradually a ...

, 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

and are not going through

sperm washing Sperm washing is the process in which individual sperms are separated from the semen. Washed sperm is used in artificial insemination using the intrauterine insemination (IUI) technique and in in vitro fertilization (IVF). It may also be used to d ...

or other alteration in between, and provided that they are separated by

density gradient centrifugation In biochemistry and cell biology, differential centrifugation (also known as differential velocity centrifugation) is a common procedure used to separate organelles and other sub-cellular particles based on their sedimentation rate. Although o ...

or swim-up before use in assisted reproduction technology.

Effect on quality

Some evidence suggests an increase in

single-strand break DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA da ...

condensation Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to ...

and fragmentation of DNA in sperm after cryopreservation. This can potentially increase the risk of

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mi ...

s in offspring DNA.

Antioxidant Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricant ...

s and the use of well-controlled cooling regimes could potentially improve outcomes. In long-term follow-up studies, no evidence has been found either of an increase in

birth defect A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can ...

s or

chromosomal abnormalities A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder, is a missing, extra, or irregular portion of chromosomal DNA. These can occur in the form of numerical abnormalities, where ther ...

in people conceived from cryopreserved sperm compared with the general population.

References

{{Authority control Assisted reproductive technology Cryopreservation Semen

Freezing

Thawing

Refreezing

Effect on quality

See also

References