Scientists are closing in on a way to help young boys undergoing cancer treatment to preserve their future fertility — and the proof is the first monkey born from the experimental technology.

More and more people are surviving childhood cancer, but nearly one in three will be left infertile from the chemotherapy or radiation that helped save their life. When young adults are diagnosed with cancer, they can freeze sperm, eggs or embryos ahead of treatment. But children diagnosed before puberty can't do that because they're not yet producing mature eggs or sperm.

"Fertility issues for kids with cancer were ignored" for years, said University of Pittsburgh reproductive scientist Kyle Orwig.

Orwig's team reported a key advance yesterday: First, they froze a bit of testicular tissue from a monkey that hadn't yet reached puberty. Later, they used it to produce sperm that, through a monkey version of IVF, led to the birth of a healthy female monkey named Grady.

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The technique worked well enough that human testing should begin in the next few years, Orwig said.

"It's a huge step forward" that should give hope to families, said Susan Taymans of the National Institute of Child Health and Human Development, which helped fund the research published in the journal Science. "It's not like science fiction."

University of Pittsburgh Medical Centre and a handful of other hospitals already freeze immature testicular tissue from young cancer patients, in hopes of knowing how to use it once they're grown and ready to have their own children.

Orwig's team froze tissue from young male monkeys, and then sterilised them. Once the monkeys approached puberty, the researchers thawed those tissue samples and gave them back to the original animal — implanting them just under the skin.

Boosted by hormones, the little pieces of tissue grew. Months later, the researchers removed them. Sure enough, inside was sperm they could collect and freeze.

Colleagues at the Oregon National Primate Research Centre injected some of that sperm into eggs from female monkeys and implanted the resulting embryos. Last April, Grady was born, and "she plays and behaves just like every other monkey that was grown the normal way", Orwig said.

The technique is similar to a female option. Girls' eggs are in an immature state before puberty. Researchers have removed and frozen strips of ovarian tissue harbouring egg follicles from young women before cancer treatment, in hopes that when transplanted back later the immature eggs would resume development. It's considered experimental even for young adults but some births have been reported. Now some hospitals bank ovarian tissue from girls, too.

- AP

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