Men facing cancer treatment may not have to rely on a limited supply of frozen sperm to have children, as doctors hail the success of putting testicle tissue in storage instead.
By Martin Hutchinson
BBC News Online health staff in Madrid
The new technique preserves the "germ cells" which make sperm, which are frozen and then transplanted back into the man when he is given the all-clear from the disease.
Remarkably, the frozen cells then "re-colonise" the testicle, and start producing enough sperm to allow fertility doctors to extract it from semen.
The Greek scientist behind the advance has already managed to grow these germ cells within the testicle of a rat, and says that storing testicle tissue instead of sperm will be a much better idea for would-be fathers.
Dr Nikalaos Sofikitis, from the Laboratory for Molecular Urology in Ioannina, Greece, recruited 22 men for a pioneering trial into the technique.
All had testicular cancer, and six had the affected testicle removed by surgeons, and were about to be given the same combination of chemotherapy drugs that would kill all their sperm-producing cells.
Tissue was taken and stored from all six, and three were selected to have these germ cells transplanted back into their bodies.
All three showed signs that the germ cells had taken hold in the body, started dividing and "recolonising" the testicle - and started to make sperm again.
Although one had a very low concentration of normal-looking sperm, the other two had reasonable concentrations which would make it feasible for viable sperm to be extracted from their semen and used in IVF.
Dr Sofikitis said that one of the men was already trying for a baby using fertility techniques.
He said: "The technique is much better because the main maintains a larger amount of genetic information than if he had simply frozen his sperm."
He said that there were a variety of uses for the technique, including the preservation of endangered species.
It is not only patients with testicular cancer who might benefit, but also those with any type of cancer that requires fertility-wrecking chemotherapy treatment.