Healthy mice born from first lab-grown eggs
Oct 21, 2016
The Japanese team, Prof Katsuhiko Hayashi and colleagues, took cells from a mouse tail and reprogrammed these adult cells back into immature ones.
Then, they coaxed these immature stem cells to become an egg.
Not all of the eggs that they made in the lab were healthy or viable.
But the ones that were could be fertilised by sperm in a dish.
When these fertilised eggs were put into the wombs of adult female mice, they developed into apparently healthy babies.
Experts warn there are many barriers to using the same method in humans.
Some are technical, but arguably the biggest ones are about safety and ethics.
Flaws in artificial eggs might be passed on to future generations, for example.
The technique the Japanese researchers used still required harvesting some tissue from embryos to support the artificial eggs as they matured in lab dishes.
Prof Richard Anderson, from the MRC Centre for Reproductive Health at the University of Edinburgh, said: "One day this approach might be useful for women who have lost their fertility at an early age, as well as for improvements in more conventional infertility treatments.
"But the very careful analyses in this paper show the complexity of the process and how it is a long way from being optimised."
Prof Azim Surani has been studying how to turn human skin cells into the precursors of sperm and eggs in his lab.
He said: "As far as humans are concerned, we are way behind.
"We can't be sure the same will apply with human cells."
The many hurdles that scientists will have to solve to perfect the procedure. Tests on the artificial eggs found that many had unusual patterns of gene expression, suggesting they had not developed in the same way as natural eggs.
But with stem cell science progressing so fast, some researchers are keen to thrash out the potential implications for humans now. “Ethically, this issue has yet to be discussed fully by scientists and society,” said Azim Surani, a stem cell scientist at the Gurdon Institute at Cambridge University, who was not involved in the latest work. “This indeed is the right time to start a debate and involve the wider public in these discussions, long before, and in case, the procedure becomes feasible in humans.”
Labs around the world are now expected to repeat the experiments before attempting the same procedure in larger animals, such as pigs, sheep and cows. Before it can help humans to multiply, it might benefit other animals. “With such technology we might be able to rewind the process of mammalian extinction,” said Dusko Ilic at stem cell scientist at King’s College London.