FREEZING - STORAGE OF SEMEN AND TISSUE

Historical background

The possibility of freezing sperm was first reported in 1776 by Spallanzani, after successful experiments in which he froze and thawed human sperm in snow. In practice, however, the first sperm freezing took place in 1949, when Polge and his colleagues observed the cryoprotective effect of glycerol on bird sperm frozen at -76 degrees Celsius. In 1953 Sherman and Bunge were the first to freeze human sperm, in a 10% glycerol solution with dry ice. The same research team achieved the first pregnancy from sperm frozen in glycerol solution and liquid nitrogen a few years later. The first human sperm banks were set up in the 1970s, and the birth of the first IVF baby, Louise Brown, in 1979 gave fresh impetus to improving sperm freezing techniques.

How is sperm cryopreserved and frozen?

Sperm can be frozen using an appropriate procedure and stored in containers of liquid nitrogen at -196 degrees Celsius. The most widely used method involves adding a suitable volume of cryoprotectant, such as glycerol at a concentration of 5-10%, to the sperm and then freezing the sample, with or without a controlled-rate freezer. In recent years, more complex solutions containing substances other than glycerol, such as egg yolk, soya lecithin, amino acids and citrate, have also been used to improve cryopreservation, without any major change in results. Frozen sperm can be stored for many years, even decades, without losing its properties or its fertilising capacity.

Indications for and advantages of sperm freezing and cryopreservation.

• Men about to undergo chemotherapy or radiotherapy for cancer, which is expected to have a significant effect on their fertility. Men about to undergo orchidectomy or prostatectomy for a benign or malignant tumour, so that they can preserve their fertility for the future.
• Men about to undergo sterilisation (vasectomy – ligation of the vas deferens), so that their fertility can remain reversible.
• Men with an unhealthy lifestyle, such as heavy smoking, heavy daily alcohol consumption or daily exposure to occupational hazards (chemicals, radiation, excessive heat), who wish to preserve their fertility for the long term through sperm cryopreservation.
• Couples undergoing IVF cycles where the husband cannot be physically present on the day of egg retrieval (long business trips, unforeseen events at work, etc.).
• Men with erectile dysfunction who cannot ejaculate, or who have a complete absence of sperm in the ejaculate: sperm can be retrieved directly from the epididymis and the testis and frozen for future use, preserving the patient's fertility.
• Men who have had an accident (spinal cord injury) and cannot ejaculate often: the quantity and quality of their sperm decline over time. In these cases, banking and storing sperm as early as possible can go a long way towards protecting their fertility.
• Men who wish to have children later in life and want to safeguard their reproductive potential as a precaution.
• Men who have been successfully treated to improve sperm quality but are unlikely to maintain that result: through cryopreservation they can freeze their sperm while its quantity and quality are satisfactory.
• Men with severe oligoasthenozoospermia, when the ejaculate has to be pooled from several collections.

It has also made sperm banks possible, and allows donor sperm to be used at any time by couples facing a serious problem of azoospermia.