Fertility landmark as scientists make sperm from stem cells

Scientists have made sperm in a laboratory from converting stem cells, and used them to produce healthy offspring in mice, in technology that could be adapted to help infertile men.

It is believed to the the first time that sperm cells made in the laboratory with stem-cell techniques have been used to generate offspring free of any obvious physical or genetic defects that have grown up and reproduced normally, the researchers said.

Scientists took stem cells from the embryos of laboratory mice and converted them into mature sperm cells, then used them to fertilise eggs and produced the healthy, fertile offspring.

The technology may one day form the basis of a new approach to treating infertile women incapable of making their own egg cells, the scientists said.

One possibility is that skin cells taken from infertile men or women could be turned into stem cells and then converted into the "germline" cells that give rise to sperm and eggs. These sperm and egg cells could then be used in standard IVF procedures.

"This is the first study to create health and fertile offspring from germline cells generated from embryonic stem cells. Previous studies have not demonstrated the generation of such offspring," said Professor Mitinori Saitou, of Kyoto University, Japan, who led the study published in the journal Cell.

"In the future, it may be possible to treat infertile men with a reproductive technology based on our contribution, but there are still a lot – really a lot – of issues that need to be resolved for this purpose," Professor Saitou said.

The Japanese scientists used embryonic stem cells from mice to make primordial germ cells, which are present in the testes and produce a steady flow of sperm cells in fertile males. The scientists also made primordial germ cells from another type of embryonic cell that was converted into a stem cell by a genetic technique called induced pluripotent stem cells. "Primordial germ cells are the precursors both for oocytes [eggs] in females and sperm in males," Professor Saitou said.

Allan Pacey, a male fertility expert at the University of Sheffield, said: "This is a quite a step forward in developing a process by which sperm could be made for infertile men, perhaps by taking as a starting point a cell from their skin or from something like bone marrow. Clearly more work needs to be done, but it's hugely exciting."