Scientists have successfully restored fertility to sterile mice by growing sperm cells from stem cells in a lab.
The research, while still early, could be promising for men who struggle with infertility. The study was recently published in the journal Cell.
Researcher Dr. Mitinori Saitou, of Kyoto University in Japan, and his research team first transformed mouse embryonic stem cells into cells that originate sperm or egg cells, called germ cells, TIME reported.
Then, those germ cells were transferred into the testes of sterile mice. The mice produced normal-looking sperm from those germ cells, that were also functional -- they were able to fertilize mice egg cells, from which 214 mouse embryos were created, according to TIME.
Those embryos were then implanted into female mice, which bred 65 healthy mouse pups. And those pups went on grow up and breed pups of their own.
"We have huge materials to work with now and ... we can accelerate our study into the cause of human infertility," Saitou told Reuters. And now that researchers know how to create mouse germ cells from mouse stem cells, they could apply the knowledge to doing the same for human cells, he said.
Infertility is a common problem, affecting roughly 15 percent of couples. Male infertility plays a role in half these cases, according to the Mayo Clinic.
Depending on the cause of the infertility, treatments can include surgery, treating infections that could have caused the infertility in the first place and treating sexual problems like erectile dysfunction. Other treatments include hormone medications and assisted reproductive technology, like in vitro fertilization.
Earlier this year, we reported that researchers from Yokohama City University also announced success at growing functioning mouse sperm from stem cells. Like in this new study, those sperm were able to fertilize the eggs of female mice, which produced live and fertile mice. However, in that study, researchers used testicular stem cells to grow the sperm, whereas in this new study, the sperm came from embryonic stem cells.
British scientists said they made human sperm cells from stem cells back in 2009, but other experts challenged their claim, saying the sperm they had created was abnormal, MSNBC reported.