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.

Egg bank

In the egg bank we freeze and store eggs and ovarian tissue.
Retrieval of ripe eggs versus in-vitro maturation (IVM)

Since the development of an advanced freezing technique, referred to as 'vitrification' it is possible to freeze eggs. It has enabled the CRG to set up an egg bank similar to the sperm bank.

When eggs are frozen, their biological clock is put on hold: they don't continue to age and cannot be damaged by external factors. Freezing eggs offers women the opportunity to keep their reproductive potential without the need for fertilisation first (to freeze embryos).

Freezing eggs may offer a solution to different groups of women:
  • women can have their eggs frozen before starting treatment that may damage their ovaries (such as chemotherapy), particularly young women who don't have a partner yet;
  • women who want to donate eggs;
  • women who want to use donor eggs;
  • single women who have not yet found a partner with whom they want children;
  • women (in general) who want to delay having children.

Particularly for egg donation, the existence of the egg bank has been a massive bonus: egg donation with frozen/thawed eggs is more efficient and patient-friendly. The egg donor also enjoys greater freedom in planning her treatment, because we don't have to take into account the preparation of the recipient.
Practically all egg donations involve the egg bank for this reason.

In-vitro maturation of immature eggs  
Normally speaking, to freeze eggs you need to follow the part of the IVF treatment required to stimulate and collect different follicles: ovarian stimulation and egg retrieval.
Now there is also a more patient-friendly alternative: the collection of immature eggs which are matured in the laboratory. This is known as IVM or in-vitro maturation.

The immature eggs can come from:
  • an 'ordinary' egg retrieval, even if this only requires light stimulation;
  • from ovarian tissue – e.g. as a result of an ovariectomy prior to cancer treatment.
    Ovarian tissue that needs to be frozen and stored undergoes a number of procedures in the laboratory first. During this process, immature egg are usually released. These immature eggs cannot be used but thanks to IVM they can be matured and stored.

IVM is an advanced technique, which is considered safe, and is being used with increasing success: worldwide already more than 5,000 children have been born after retrieval of immature eggs followed by IVM and in-vitro fertilisation in couples with reduced fertility.

Future hope

Even though the technique is still in its infancy, it has been successful. Several healthy children have already been born:

  • following the transplant of thawed ovarian tissue in the mother, and
  • after the in-vitro fertilisation of (thawed) eggs matured and frozen via IVM.

For young women facing cancer treatment involving high doses of chemotherapy or radiation, the freezing and storing of ovarian tissue gives them a chance - however small - of getting pregnant in the future.

Ovarian tissue - in particular the outside of the ovary - contains the primordial cells from which eggs mature.

Obviously, the decision to surgically remove (biopsy) and store (part of the) ovarian tissue is not made lightly. The (laparoscopic) procedure is only performed in Belgium if there is a fair chance that the fertility of the patient can be restored after cancer treatment.
Cancer treatment usually has an irreversible effect on fertility. Chemo and radiotherapy are not selective and don’t only attack cancer cells and therefore have a destructive effect on other cells as well, including - if they cannot be shielded or protected - the supply of immature eggs in the ovaries.

Ovarian tissue can be frozen safely. By storing it:
  • we can keep the primordial follicles to mature them at a later time, and
  • we keep open the option to transplant ovarian tissue at a later time.

For more information about protecting your fertility in case of cancer, see and .

For the scientific research at the CRG in this respect, see follicle biology.