For children undergoing cancer treatment, having children of their own someday may be the furthest thing from their young minds. Just surviving into adulthood is their main concern, even if it means undergoing nauseating chemotherapy and radiation that can leave them sterile.

With the childhood cancer survival rate now approaching 80 percent, many children—boys and girls—grow up without the ability to reproduce. But a new study from the School of Veterinary Medicine may have found a way to preserve the fertility of boys after they receive cancer care.   

Ralph Brinster, the Richard King Mellon Professor of Reproductive Physiology at Penn Vet, has spent half a century researching the inner workings of the cells involved in reproduction, a career’s worth of work that last year garnered him the National Medal of Science.

Cells that give rise to sperm are known as spermatogonial stem cells, or SSCs. They are present in males from birth, but only start producing sperm when a boy reaches puberty.

A small number of hospitals, including the Children’s Hospital of Philadelphia, have extracted SSCs with the hope of re-implanting them in young boys after successful cancer treatment. The techniques for transferring these cells have been well established, but it was unknown how long the cells could be frozen while remaining viable.         

“A logical question for these patients to ask is, ‘How do we know that, after 10 years or more of being stored, these cells are any good?’” Brinster explains. “That’s what our study addresses.”

Beginning in 1995, Brinster began storing a large number of SSCs from mice, as well as a small number of rat, rabbit, and baboon SSCs, in a freezer. Fourteen years later, Brinster and his colleagues set to work thawing out the SSCs and showing that they would implant themselves in the correct niche in mice testes.

Brinster’s research also showed that the SSCs that came from mice produced sperm naturally and that this sperm, through in vitro fertilization and natural mating, produced offspring that appeared free from genetic defects.

With the major questions about this technique answered in animal models, medical professionals are one step closer to restoring fertility to young boys who have beaten cancer.