Mouse Eggs being made from skin cells in a dish and the what that means for the future of human eggs being created

Mouse Eggs being made from skin cells in a dish and the what that means for the future of human eggs being created

These eleven-month-old mice were born from eggs made entirely in a dish.

In a tour de force of reproductive biology, scientists in Japan have transformed mouse skin cells into eggs in a dish, and used those eggs to birth fertile pups. The report marks the first creation of eggs entirely outside a mouse. If the process could be made to work for humans, researchers could produce artificial eggs without needing to implant immature cells into ovaries to complete their development.

 

Katsuhiko Hayashi, a reproductive biologist at Kyushu University in Fukuoka, led the group that announced the breakthrough on 17 October in Nature1. In 2012, when at the University of Kyoto, he and stem-cell biologist Mitinori Saitou reported taking skin cells down the pathway towards eggs: reprogramming them to embryonic-like stem cells and then into primordial germ cells (PGCs)2. These early cells emerge as an embryo develops, and later give rise to sperm or eggs. But to get the PGCs to form mature eggs, the researchers had to transfer them into the ovaries of living mice.

 

The next advance came in July 2016, when a team led by Yayoi Obata, at the Tokyo University of Agriculture, reported transforming PGCs extracted from mouse fetuses into oocytes (egg cells) without using a live mammal3. Working with Obata, Hayashi and Saitou have now completed the cycle: from skin cells to functional eggs in a dish. With the use of in-vitro fertilization (IVF) techniques, 26 healthy pups were born (some originally from embryonic stem cells and some from reprogrammed skin cells). Hayashi says some of these animals gave birth to a second generation of mice.

 

“This is truly amazing,” says Jacob Hanna, a stem cell biologist at the Weizmann Institute of Science in Rehovot, Israel.  “To be able to make robust and functional mouse oocytes over and over again entirely in a dish, and see the entire process without the ‘black box’ of having to do any of the steps in host animals, is most exciting.”

 

“Parts of this work were done before — here they are put together in completeness. It’s impressive that they got pups that way,” says Dieter Egli, a stem cell biologist at the New York Stem Cell Foundation Research Institute.