This novel way of creating sperm cells could bring about new therapies for male infertility, which is thought to be the problem in roughly half of couples who have trouble conceiving.
'This research provides an exciting and important step for the promise of stem cell therapy in the treatment of azoospermia, the most severe form of male factor infertility', said Dr Michael Eisenberg, director of male reproductive medicine at Stanford University, where the study was conducted. 'Being able to efficiently convert skin cells into sperm would allow this group to become biologic fathers'.
The team took skin samples from five men, three of whom had azoospermia and two of whom were fertile. They transformed them into induced pluripotent stem cells, and when these were transplanted into mouse testes, they developed into early-stage sperm cells. These may have become fully mature sperm cells if the stem cells had been transplanted into the men's testes, the researchers believe.
'We saw better germ-cell differentiation in this transplantation model than we've ever seen', said Dr Renee Reijo Pera, who led the study. 'We were amazed by the efficiency. Our dream is to use this model to make a genetic map of human germ-cell differentiation, including some of the very earliest stages'.
Dr Allan Pacey from the University of Sheffield commented to the Telegraph: 'The received wisdom is that if you have a Y chromosome defect like this you don't make sperm. Until I read this paper I would have said if you take skin cells from an infertile guy it won't work. But what this seems to suggest is that it could'.
Warning that sons born using such a procedure would be at risk of inheriting infertility, Dr Pacey added: 'Obviously the outcome is poorer than if you don't have the defect, but the fact that they could do this at all is quite exciting. At the moment the door is closed to these men'.
Azoospermia is thought to affect one percent of men worldwide, but the team hopes that other men affected by infertility could one day be treated using this technique.
'[This study] provides very intriguing possibilities for men rendered sterile after cancer treatments', said Dr Eisenberg. 'Infertility is one of the most common and devastating complications of cancer treatments, especially for young boys and men'.