Cryopreservation – Sperm Freezing
Cryopreservation is the conservation of biological tissue at cryogenic (very low) temperatures, typically at -80C (dry ice temperature) or -196C (the boiling point of liquid nitrogen) as chemical and biological reactions in living cells are drastically reduced at such low temperatures. These cells/tissues can be thawed, revived and reused, under proper conditions.
Human sperm can be stored in this manner up to 40 years and used successfully for fertility therapy.
Sperm cryopreservation is important for various reasons, some of which are:
- Sperm availability during treatment for sperm-toxic diseases like cancer or other non-malignant diseases, as in Covid-19
- A pathological condition develops which will cause sterility
- Sperm preservation for males who plan to undergo vasectomy.
- The male is sterile and sperm donation is required.
The advantages of Cryopreservation are reduction in risk of morphological changes and cross-contamination. It also helps with microbial contamination.
The need for sperm cryopreservation is enhanced when the following occur:
- Non-availability of the male during IVF treatment – where the couples are undergoing fertility treatments and the male partner cannot be present at the time of treatment due to travel, work or other reasons.
- Vasectomy causing surgical sterilization
- Treatment for cancer
- Diabetes causing erectile dysfunction
- Occupational risks – patients who have occupational risk exposures, such as in sports, or are on certain medications, may stop the same for a period of time to allow the sperm quality to improve, so that preservation of improved sperm can be carried out, before they resume their work/medications.
Cryopreservation of human sperm has been used widely to treat couples with infertility problems. Sperm preservation has played an important part, especially in the case of patients undergoing cancer therapy. Now, with the Covid pandemic, it has offered a way for sperm to be preserved during this difficult time as well.
According to expert Joe Conaghan, PhD, HCLD, “During freezing, sperm are cooled to a very low sub zero temperature (minus 196 degrees Centigrade). At that temperature, all biological activity is effectively stopped. The sperm cells are not metabolizing or depleting their energy reserves. They are truly in suspended animation. Bacteria or other microbes cannot attack or degrade the sperm in any way because they are also unable to function at such a low temperature. Everything is on hold.”
Semen parameters before cryopreservation have shown to be accurate when compared with sperm motility and viability after thawing. However, some damage can be caused to sperm during the freezing and thawing process due to various reasons such as formation of ice crystals, osmotic shock or membrane damage. Most sperm storage banks use nitrogen vapor, which lowers the risk of viral cross contamination, as the use of liquid nitrogen sometimes causes such cross-contamination with other samples in the same container.
A plus factor is that cryopreservation has been gradually increasing in success with the use of CPAs (cryopreservation agents) and temperature controlled equipment. High security storage containers are also reliable and have also helped to resist potential cross-contamination.
Sperm washing prior to freezing has been shown to improve post-thaw sperm motility, as it separates spermatozoa from seminal plasma. It is best for men with low sperm motility (movement) and low sperm counts. To date, no seroconversions (transition from the point of viral infection to when the virus becomes present in the body) have been reported during pregnancies using sperm washing.
Most Fertility centres offer sperm cryopreservation/freezing facilities to their patients at affordable rates. Contact your fertility specialist to understand if sperm cryopreservation is best suited for you.
