A 27-year-old man whose testicular tissue was frozen before chemotherapy as a child is now able to produce sperm after a re-transplant, according to reports on a new fertility trial. The tissue was collected when he was 10 and preserved in preparation for possible future fertility preservation. He later received potent chemotherapy for sickle cell disease, which the sources say left him infertile. The study is described as the first demonstration that a transplant of cryopreserved prepubertal testicular tissue can restore sperm production in an adult patient. Media coverage characterizes the approach as a “world-first” and highlights the potential for boys who become infertile due to cancer treatment to have biological children later in life. The accounts specify that the man produces sperm following the re-implantation, with follow-up continuing as researchers evaluate the outcomes of this technique. The reports do not provide additional details on sample size or long-term results beyond sperm production.