Storage of cells and tissue

Postpone motherhood?

If you can feel the clock ticking but you want to postpone motherhood, AGE banking may be a solution. This is also known as social freezing

During your ART treatment or before you start treatment, it may be necessary to freeze and store reproductive cells or tissue. UZ Brussel's tissue bank where we store reproductive human tissue is called the CRG's MLM bank.

To freeze any tissues, a contract must be signed at all times. In this contract:
  • you give your consent to freeze and store tissue;
  • you determine the storage period;
  • you decide what needs to be done with the stored material on termination of the storage period or when you don't need it anymore; and
  • (if applicable) you undertake to pay a storage cost for the period of storage.
These decisions can be revoked at all times, as long as you do this in writing before the end of the storage period.

Storage of sperm and testicular tissue

Sperm can be frozen and stored relatively easily. The same applies to testicular tissue - with either sperm, or (pre-pubescent) stem cells.

Sperm is frozen in the following situations:

Fresh or frozen?

Both for IVF, IVF-ICSI and artificial insemination with own sperm a fresh sample is preferable for practical reasons.

  • for donor sperm. This is never fresh.
    Donor sperm usually remains frozen for a period of six months before it is used: see Donation - what and how? about anonymity and double checks;
  • when sperm is retrieved during MESA, PESA or TESE procedures and more is obtained than is necessary for the current ICSI treatment (see sperm extraction for ICSI);
  • during a classic IVF treatment or for artificial insemination, if you cannot be present at the moment of egg retrieval or insemination.
    Or if you think you will not be able to produce a sperm sample at the crucial moment, freezing and storing may offer a solution;
  • before sterilisation (vasectomy);
  • before sterilisation treatment, e.g. due to cancer.
    More information is available on the website Here we discuss the freezing of sperm and testicular tissue as (a) possible way(s) of preventing the loss of your fertility after cancer treatment.


    Via the surgical removal of testicular tissue (see testicular biopsy), sperm can be retrieved before they are fully mature, i.e. before they arrive in the epididymis.
    A testicular biopsy can be performed for diagnostic purposes. However, usually it is performed to collect and store sperm or sperm producing cells (see anatomical explanation).

    Freezing testicular tissue can offer a solution for four groups of men and boys.

    Adult men

    In principle adult men can have their sperm frozen and therefore do not have to freeze and store testicular tissue. For a number of men this is the case though:

    • men with azoospermia (absence of sperm in the ejaculate), who have a TESE procedure to collect testicular sperm for fertility treatment with ICSI.
      If more sperm than required are retrieved, the excess sperm can be frozen for possible later use;
    • men who have a vasectomy reversal, known as reanastomosis or the repair of the vas deferentia after a sterilisation. Because reanastomosis is not always successful, patients may choose to freeze testicular tissue prior to the reversal operation;
    • men who will have cancer treatment that will result in sterilisation who have no sperm in their sperm sample. See .
      • The cancer itself can lead to a reduction in sperm production, resulting in azoospermia. Sperm can sometimes be found via TESE in the testicular tissue and be stored before the start of the cancer treatment.
      • Testicles sometimes have to be removed for testicular cancer and semen can be taken from the removed testicles for freezing.

    Pre-pubescent boys

    Pre-pubescent boys who have to undergo cancer treatment before puberty form a separate group. They don't yet produce sperm (see sperm production). If they have potentially sterilising cancer treatment or a blood disorder (e.g. sickle cell anaemia), their future fertility can be preserved via the collection and storage of sperm stem cells from the testicles. Stem cells are the cells from which sperm will later be produced. A testicle or testicular tissue is removed, frozen and stored, with a view to a possible future transplant.

    Freezing stem cells from the testicle of pre-pubescent boys is currently still in an experimental phase. It offers no certainty of later fertility. The procedure is only performed under certain circumstances and is decided together with the child's parents, the paediatrician, the cancer specialists, and the fertility clinic.

    Please go to for more detailed information about this subject. Click on testicular stem cells for more information regarding the current research project at the CRG