Ovarian tissue cryopreservation is a fertility preservation technique. This surgical technique, which is used in Assisted Reproduction, consists of removing ovarian tissue from a patient and freezing it so that it can be used in the future. It is indicated, fundamentally, in oncological patients who are girls or adolescents who have not yet had their first menstruation, although it can also be offered up to the age of 35 years if vitrification of oocytes is not possible due to lack of time.
The Hospital Sant Joan de Déu, under the guidance of Prof. Justo Callejo, was a pioneer in Spain in performing this fertility preservation technique. Dr. Cristina Salvador i Alarcón and Dr. Santiago González Núñez, currently form the medical team specializing in this subject. The fertility preservation program began in 2000 and currently has more than 300 frozen ovaries awaiting demand for reimplantation. These ovaries are stored in the Blood and Tissue Bank of Barcelona.
The first birth in the world with this technique took place in 2004. At present, more than 30 births have already been published.
Who is ovarian tissue cryopreservation aimed at?
It is aimed at oncological patients whose ovarian function may be damaged by chemotherapy or radiotherapy treatment. It is mainly indicated in girls, who cannot be offered other fertility preservation options such as oocyte vitrification, although it can also be performed in adult patients under 35 years of age. The younger the patient, the greater the richness of primordial follicles in the tissue.
There are oncologic processes in which the rate of cancerous cells is high, so when reimplanting ovarian tissue it is possible that there is a risk of reintroducing cancerous cells into the body. In these cases cryopreservation should not be performed, but other fertility techniques should be used.
Process of ovarian tissue cryopreservation
The removal of ovarian tissue is performed laparoscopically. There are two options: either the entire ovary is removed or only a wedge (cortex) of the ovary, which is where the cells that will be able to mature and give rise to the egg (primordial follicles) are located.
In the case of infantile patients, due to the small size of their ovary, the entire ovary is usually removed.
Once the ovary has been removed, it must be fragmented into 1 or 2 mm pieces since it is not possible to freeze the entire ovary. These fragments are stored at the Barcelona Blood and Tissue Bank (BST) and remain frozen until the patient requests reimplantation. There is no limit to cryopreservation, so ovarian fragments can be stored for many years. Currently, reimplantation of ovarian tissues that have been frozen for 16-18 years is being performed.
Reimplantation is also performed laparoscopically. It consists of making two small peritoneal pockets where the tissue fragments will be deposited: one in the area where the ovary was previously located and the other right next to the ovary that the patient still has and that has stopped functioning due to the oncological treatments.
We must wait between 3 and 4 months to assess the viability of the implant, since it does not work immediately. Analytical controls are carried out to evaluate the hormonal function.