(Wired) – In an advance for treating male infertility, researchers transplanted a patient with his own sperm-forming stem cells that were collected from testicular tissue when he was a child.

Jaiwen Hsu was an active 11-year-old when he developed pain in his left knee that forced him to sit out a few soccer games. What his parents thought was a sports injury turned out to be osteosarcoma, a type of bone cancer.

He started chemotherapy, which doctors warned could result in infertility. Hsu hadn’t reached puberty yet, so sperm banking wasn’t an option. His parents enrolled him in a study that was collecting and storing immature testicular tissue, and the sperm-forming stem cells in them, from young patients with the goal of eventually giving them a way to have biological children. (Read More)