Scientists in Japan have successfully created viable offspring in infertile mice using synthesized sperm, according to a study that could lead to advances in curing infertility in men.
A research team from Kyoto University has used stem cells, the specific type known as epiblast cells, in order to create germ cells, which are the building blocks to the male and female reproductive cells.
Upon developing the germ cells, the scientists inserted them into the testes of infertile male mice that went on to produce healthy sperm. The sperm was in turn was used to fertilize female egg cells and were implanted into female mice.
Of the 214 embryos that were created, sixty-five mice were born and survived their first year of life. The team findings have been published in the Cell journal.
"The mouse babies are just fine and they've had normal, fertile babies of their own," Dr. Mitinori Saitou, senior author of the study, told the Wall Street Journal.
He explained that the occurrence of pregnancy in the inseminated mice was about the same as is seen in artificial insemination that uses naturally-produced sperm.
"It's a brilliant set of experiments," Dr. George Daley, director of the stem-cell transplantation program at Children's Hospital Boston, told WSJ upon reading the study in Cell. "They restored fertility in the mice. It lays the groundwork for major insights into sperm development and fertility."
While the overall goal is to be able to translate these findings into practical use for humans, much continued study needs be done, according to Saitou.
Scientists note that mouse cells and human cells are extremely different, but Saitou said in a phone interview with Reuters that with these "huge materials to work with," scientists can begin to study the origin of infertility in humans.
The premise also provokes the ethical debate of whether or not it is permissible to destroy a human embryo in order to extract its stem cells. Further study by the Kyoto University team has developed a possible alternative to embryonic stem cell conversion, by reprogramming adult stem cells to act like embryonic stem cells and then converting them into sperm cells.
This method however has not yielded promising results due to a 20 percent mortality rate in the pups born using reprogrammed cells. Many of the pups died from cancerous tumors that have been connected to the reprogramming process.
Saitou said that he and other scientists will continue to experiment with the less controversial method in order to extricate the deathly side effect.
And also mentioned in other fertility research, Saitou plans to create functioning egg cells from embryonic stem cells -a feat which Daley, comments may be much more difficult to execute.
"It would be a monumental achievement since there's currently no method for restoring female fertility," said Daley.