In a revolutionary first for science and medicine, human eggs have successfully been grown in a laboratory in the United Kingdom. A similar venture has previously been achieved with mouse eggs, even using the lab-grown eggs to create live mice offspring.
Researchers have now managed to turn immature human eggs into the fully developed version in the lab for the first time, but as of now, it's still unclear whether the mature eggs are normal and can actually combine with sperm to make an embryo.
According to experts the research could be especially relevant for girls who have not gone through puberty.
But the approach has drawbacks.
That process raises concerns that re-implanting tissue taken prior to cancer treatment might reintroduce cancer cells into an individual's body. The technique will also need further development to boost efficiency - out of dozens of eggs harvested, only a few could be pushed to full maturity during the study.
Scientists were able to remove eggs from the ovary tissue at their earliest stage of development and then grow them to the point at which they were ready for fertilisation. Of the 48 eggs that reached the penultimate step of the process, nine reached full maturity. In the third step the cells developed over a nutrient rich membrane and they matured fully in the fourth step.
Decades of work have finally shown that scientists can grow eggs to maturity outside of the ovary, under strict laboratory conditions such as controlled oxygen levels, hormones, proteins that mimic growth, and the substance in which eggs are cultivated.
"The ability to develop human oocytes from the earliest follicular stages in vitro through to maturation and fertilization would benefit fertility preservation practice", the researchers wrote. Researchers must prove that the eggs cannot only mature, but do so without any abnormalities that could pose a risk to women. "With this [new] procedure, you could potentially get thousands or hundreds of eggs".
The research has given new understanding into how human eggs develop at various stages, they say.
There has been a cautious welcome for the news from one of Ireland's leading fertility experts. Here, they have, through meticulous experimentation, worked out how to complete the third and final stage. "We are now working on optimizing the conditions that support egg development in this way and studying how healthy they are", said Evelyn Telfer, who co-led the work.
Currently, women facing cancer treatment - which can destroy fertility - have two options.