Scientists Grow Sperm in a Dish With Embryonic Stem Cells

Scientists grew sperm in a dish from embryonic stem cells that produced a healthy mouse offspring. Reuters

Approximately 15 percent of couples struggle to conceive. A third of these cases is due to male infertility. But in a pioneering experiment in reproductive technology, researchers in China believe they've developed a solution by creating functional sperm out of stem cells. The team then injected the engineered sperm into egg cells, which produced a healthy mouse offspring that was also able to reproduce.

Should the process work on human stem cells, the researchers say it could be a game-changer for couples that struggle to conceive due to male infertility. The details of their study were published Thursday in Cell Stem Cell.

There are several factors to explain the cause of male infertility, but one reason is that in some cases, germ cells in the testes are unable to attain a critical cell division process called meiosis to become fully formed and functional sperm. In meiosis, a single cell divides twice and then produces four cells that contain half the original genetic information.

However, a common struggle for scientists in the field of reproductive medicine has been to confirm or prove germ cells have gone through meiosis. The researchers solved this by exposing embryonic stem cells to certain chemicals in order to help them transform into sperm-like cells, called spermatids. Then they emulated the natural tissue environment by exposing the spermatids to testicular cells, testosterone and other sex hormones.

In the experiment, the researchers found the cells underwent meiosis and fully transformed into functional sperm-like cells. To show that the experiment had real-life potential, the researchers injected the spermatids into mouse egg cells. Those developed into embryos, which proved to be viable when transferred into female mice. The embryos eventually produced healthy offspring that were also able to reproduce.

In the future, the researchers plan to test out the technique on primates. However, they will need to identify the procedure's potential risks and any ethical concerns that may arise from using embryonic stem cells before they can try out the procedure on humans.

Ethics have become a growing concern, as reproductive medicine increasingly resembles a science fiction page-turner. For example, scientists using gene therapy to cut and replace faulty DNA in an embryo have faced some pushback, despite the fact that the technology could help prevent congenital conditions and other diseases in an offspring. It's controversial because it would, theoretically, produce a three-parent offspring.