Semen 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).
The commonly-used semen washing techniques:
- Direct Swim-up Technique: Spermatozoa are selected based on their ability to swim out of seminal plasma into the culture medium. The direct swim-up of spermatozoa from semen is the preferred method of separating out the high motile spermatozoa. This technique gives a lower yield of spermatozoa than washing and selects sperms on basis of their motility.
- Density gradient Technique: This method uses centrifugation of seminal plasma over the density gradients consisting of colloidal silica coated with silane, which separates sperms according to their density. The normal motile spermatozoa with the compact head are denser and heavier and will swim actively through the gradient media and thus will settle at the bottom to tube to form a soft pellet. There are two types of density gradient technique of semen washing: –
- Continuous Gradients: In the continuous gradients, there is a gradual increase in density from the top of the gradient to its bottom.
- Discontinuous Gradients: In a discontinuous gradient, there are clear boundaries between lower and upper gradients. The most widely used discontinuous density gradient preparation includes 45% (v/v) density (top layer) and 90% (v/v) density (lower layer).
The choice of sperm preparation technique is decided by the nature of the semen sample. The direct swim-up technique is often used for normal semen samples. In the cases of severe oligozoospermia, teratozoospermia, or asthenozoospermia, density gradient techniques are preferred because of the high recovery of motile spermatozoa.
A sperm bank also referred to as a cryobank, is a facility that collects, freezes, and stores human sperm. The sperm kept at a sperm bank is either donated by men to be used by couples seeking sperm donations for artificial insemination or IVF procedures or is provided by men who want to preserve their own sperm for future use.
Indications for Semen Banking
Semen from healthy donors known or presumed to be fertile may be stored for future use. These donors may be recruited by a clinic or sperm bank and their spermatozoa used anonymously.
Semen may be obtained and stored before a man undergoes a procedure or exposure that might prevent or impair his fertility, such as:
- Vasectomy (in the case of a future change in the marital situation or desire for more children)
- Treatment with cytotoxic agents or radiotherapy, which is likely to impair spermatogenesis permanently
- Active duty in a dangerous occupation, e.g. in military forces, in countries where posthumous procreation is acceptable.
Spermatozoa may be stored for treatment of the man’s partner by artificial insemination by husband’s semen (AIH), IUI, IVF, or ICSI, in cases of:
- Severe oligozoospermia or intermittent presence of motile spermatozoa in the semen (as the backup for ICSI).
- Treatment of infertility that may not persist, such as surgery for genital tract obstruction or gonadotrophin treatment for hypothalamic-pituitary hypogonadism
- The need for a special collection, such as assisted ejaculation for patients with spinal cord injury, spermatozoa from retrograde ejaculation in urine, or surgical collection from the genital tract.
- Men who are unable to provide fresh semen on the day of an ART procedure.
Minimizing Infectious Disease Transmission
For men with HIV controlled by antiretroviral therapy, samples with an undetectable viral load may be stored for IUI, IVF or ICSI, to attempt conception while reducing the risk of transmission of HIV to the female partner.
Different Techniques for Sperm Banking
- Slow Freezing: This involves progressive sperm cooling over a 2-3 hour period in various steps, either manually or automatically using a semi-programmable freezer.
- Vitrification: Semen vitrification is performed by directly dropping the spermatozoa suspension in LN2 at -196° C.