In a recent breakthrough, researchers have managed to grow eggs in a lab dish using skin cells from mice. Some of these eggs even produced six healthy mice.  The research was published on October 17th in the journal Nature, by Katsuhiko Hayashi of Kyushu University in Fukuoka, Japan and colleagues. This new development could allow scientists to study the little understood process involved in the formation of gametes, eggs and sperm, which normally takes place inside fetuses. If scientists are able to make this process work with human cells, it could allow them to supply eggs to be readily available for research. In turn, this could lead to more advanced treatments for infertility.

Scientists cautioned that repeating this work with humans is still most likely a long way off.

Using stem cells to produce eggs is a much more difficult process than producing the variety of cells scientists have managed to create from stem cells. Eggs are even more flexible in their ability to create the various parts of an organism from raw DNA. The researchers found that even using stem cells, the process needed the help of the ovary cells that support the growth of eggs in nature. While the team had managed to create primordial germ cells using stem cells, they had to put those cells into the ovaries of mice for them to continue their development into eggs.

Hayashi has said it is not yet clear how ovaries facilitate the development of egg cells, but the presence of the ovary’s support cells seems to be necessary for the egg to reach maturity. Since researchers are still unable to create these support cells in a lab setting, they must be taken from actual embryos, which may present an obstacle to reproducing these results in humans.

In this research, Hayashi and his team created artificial ovaries by taking ovarian support cells from mouse embryos.  They then inserted the cells created from the skin cells, which functioned as primordial germ cells. In a period of 11 days, the cells had matured into eggs, ready for fertilization. 11 days is roughly the time it takes for them to mature in an actual mouse ovary, meaning that it could be a 9 to 12-month process with human cells, according to scientists.

The eggs were fertilized and then transferred into the varies of female mice, who gave birth to six healthy mice who produced offspring of their own.

Other experiments indicated that about one in 20 lab-grown eggs is actually viable, according to Hayashi. “This means that it is too preliminary to use artificial oocytes for clinical purposes. We cannot exclude a risk of having a baby with a serious disease. We still need to do basic research to refine the culture conditions,” he says.

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