For the first time in medical history, a man who was rendered infertile by chemotherapy in childhood has received a transplant of cryopreserved immature testicular tissue that had been frozen for 16 years. This procedure, performed by researchers at Vrije Universiteit Brussel and Brussels IVF at UZ Brussel, aims to restore sperm cell production in patients whose fertility was severely compromised by cancer treatments before they reached puberty. The tissue was transplanted in both the testicle and the scrotum, and the ultimate goal is to see whether new sperm cells can be produced autonomously, leading to the possibility of fatherhood with the help of assisted reproductive technology if needed.

The rationale behind this approach lies in the preservation of testicular stem cells, which are crucial for sperm production. In boys undergoing potentially fertility-threatening treatments, such as chemotherapy or radiation before puberty, doctors can remove and freeze small fragments of testicular tissue containing these stem cells. Once the patient reaches adulthood and wants to explore family planning options, the frozen tissue can be reintroduced to encourage sperm production. This concept, developed through years of laboratory research, has opened a vital doorway for young individuals who might otherwise face lifelong infertility.

After the transplant, the patient will be evaluated over a period of one year through regular blood tests, hormone analysis, ultrasounds, and semen sampling every three months. Because the transplanted tissue fragments are not directly linked to the patient’s existing sperm duct, spontaneous sperm appearance in the semen is not guaranteed. However, if the newly produced sperm cells are found within the testicular tissue, they can potentially be used later on through assisted reproductive techniques. At the end of the year, the transplanted fragments will be removed and examined to confirm whether they have succeeded in generating mature sperm. Additional samples will be taken from other areas of the testis to determine whether the procedure has stimulated wider sperm cell production.

These pioneering steps build on a clinical fertility preservation program at UZ Brussel that began in 2002, the first of its kind worldwide to collect and store testicular tissue from young boys facing fertility-threatening treatments. The collaborative efforts have expanded under the guidance of leading scientists, who continue to refine methods of both tissue transplantation and in vitro sperm production. This second strategy, still under development, could one day serve as an alternative for patients whose tissue is found to contain cancer cells or who cannot successfully undergo a transplant procedure.

Looking ahead, this milestone offers renewed hope to cancer survivors and children affected by other serious illnesses that require aggressive treatments. While there are no absolute guarantees that the procedure will result in fatherhood for all patients, the possibility of restoring fertility now exists where it did not before. By freezing testicular tissue prior to puberty and reintegrating it after completing cancer treatment, the medical community has taken a transformative step toward ensuring that childhood survivors of serious diseases have broader, more promising options when they consider building families in adulthood.

Source

11 January 2025. VUB

• World first - First ever transplant of frozen testicular tissue after chemotherapy during childhood provides hope for fertility restoration