Monkey semen, monkey do

Scientists have taken frozen testicular tissue sourced from a prepubescent monkey, thawed it, and inserted it in a castrated adult male of the same species – which then successfully fathered a baby.

The work is an important step forward in research aimed at rectifying the lifelong infertility that is often a cruel side-effect for human boys who receive chemical and radiation treatment for cancer.

Adult men undergoing such therapies have the option of cryopreserving sperm before treatment begins, but this approach, by definition, is not available for the young.

Research carried out by geneticist Adetunji Fayomi from the University of Pittsburgh, US, and colleagues, suggests that preservation of immature testicular tissue – which contains sperm stem cells – might overcome the problem.

Fayomi’s team removed the tissue and subjected it to cryopreservation, before later reviving it and grafting it into either back or scrotal tissue of castrated adult rhesus macaques (Macaca mulatta).

The grafts then grew and successfully produced robust viable sperm. Some of this was extracted and mated with an egg, in vitro, then transferred into a female, resulting, somewhat later, in the birth of a healthy young girl, whom the researchers named Grady. Ten other attempts, using five other females, failed.

The researchers say further work is needed – in particular, using the technique in uncastrated males – before any recommendations for clinical relevance in humans can be made.

The research is published in the journal Science. In a related editorial in the same issue, Nina Neuhaus and Stefan Schlatt of Germany’s Centre of Reproductive Medicine and Andrology downplay the high failure rate in the experiment, saying the processes involved are much better understood in humans than in other primates.

Future research, they predict, “will be more efficient with human material”. As a consequence, they recommend that “clinical trials testing this strategy on patient material should now be performed”.