A medical breakthrough means boys who undergo fertility-destroying cancer treatment could still have children of their own later in life.
Scientists have frozen testicular tissue from monkeys too young to produce sperm before successfully using it to produce a pregnancy leading to healthy offspring.
More than 80 per cent of children with cancer will survive – but 30 per cent of survivors will be infertile as adults.
Researchers say the method, called cryopreservation, is an early step in the effort to maintain the fertility of childhood cancer patients.
The scientists removed and froze testicular tissue from five rhesus macaques too young to produce sperm.
When the animals approached puberty, the researchers thawed the tissue samples and implanted them, along with a comparison set of fresh, unfrozen samples, back into the animals they came from.
A few months later, they removed the tissue implants and found that both the fresh and frozen tissue had produced sperm.
The researchers then isolated sperm from the previously frozen implants and used it to fertilise 138 eggs – of these, 41 per cent developed into early-stage embryos.
The researchers then transferred 11 embryos into female macaques, resulting in one pregnancy and subsequent live birth.
Lead researcher Professor Kyle Orwig, of the University of Pittsburgh School of Medicine in the US, said: “The gold-standard proof of concept for any reproductive technology is the production of functional gametes and live offspring.
“In this study, we demonstrated that frozen and thawed prepubertal testicular tissue could be matured in vivo by grafting under the back skin or scrotal skin of the same animal to produce functional sperm and a healthy baby.
“One caveat to our study is that testicular tissues were grafted into castrated animals, which would not usually be the case with prepubertal cancer survivors.
“We castrated animals in this study because that is the only condition that produced sperm in previous nonhuman primate autologous testicular tissue grafting studies.
“Future studies are needed to confirm that graft development proceeds in a similar fashion in the scrotum or under the skin of individuals with intact testes.”
Prof Orwig said cryopreservation would not likely be appropriate for childhood leukaemia, lymphoma, or testicular cancer survivors in case cancerous cells were reintroduced to the survivor.
But it could be used for young patients with cancerous tumours or bone marrow, for example.
He said: “A second caveat is that testicular tissues collected before cancer treatment might harbour malignant cells.
“Therefore, the autologous grafting approach may not be appropriate for childhood leukaemia, lymphoma, or testicular cancer survivors.
“On the other hand, autologous testicular tissue grafting could be appropriate for patients receiving bone marrow transplants for nonmalignant conditions or patients with solid tumors, including sarcomas and neuroblastomas that do not metastasise to the testes.”
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The research team said although the study is small, it helps establish the concept of using immature testicular tissue to preserve fertility.
Prof Orwig added: “Human tissue studies as well as studies addressing the caveats outlined above are needed to understand the scope, safety, and feasibility of testicular tissue grafting in patients. ”
The findings were published in the journal Science.