These human eggs (oocytes) can now be made from adult ovaries; Credit: Shutterstock

Yvonne A R White, Dori C Woods, Yasushi Takai, Hiroyuki Seki and Jonathan L Tilly worked hard in 2004. When this intrepid team revealed that some mammals (eg. mice) can produce eggs into their adult life, there was hope that stem cells could now become a staple of medical ideas. That hope has been fully justified. Published in the March issue of Nature Medicine, the same team have explored human female ovary capabilities and performed what was thought the impossible.

We may all know that female babies are born with their full and finite complement of oocytes or eggs, but we are only partly correct. Now the possibilities have enlarged. The proof that you could find egg-producing stem cells in the ovary of adult women was paramount for this team of scientists.

Dr. Jonathan Tilly directs the Vincent Center in Massachusetts General Hospital: "The discovery of oocyte precursor cells in adult human ovaries, coupled with the fact that these cells share the same characteristic features of their mouse counterparts that produce fully functional eggs, opens the door for development of unprecedented technologies to overcome infertility in women and perhaps even delay the timing of ovarian failure." Presumably, stem cell researchers will read much more into this.

Shanghai mouse research provided support with proof of egg-producing stem cells in 2009 and then the Vincent team developed a more precise green fluorescence-activated cell-sorting technique(GFP), whereby no possibility of contamination from other cells was possible. The verified eggs they produced could then be fertilised and developed into blastocysts. Now for human tissues. The resultant oocytes (eggs) not only looked like and grew like those in human ovaries, but some had the required haploid number of chromosomes, presumably after meiosis (all true eggs of course have to double up their DNA later, when fertilised.)

This cross-section of a human ovary shows potential areas for stem cells -which can now be converted to oocytes - even in adult women; Credit: Shutterstock

The final step, to date, involved using mouse recipients for the human tissue. Immature human follicles and oocytes were found after 7-14 days, and possibly were present before the mouse skin graft. Dr. Tilly and the team are now exploring the freezing of these cells in human OSC banks, as human eggs cannot be frozen and thawed without damage.

Likewise, factors such as hormones that influence the marvellous transformation from OSC to oocyte need to be identified with IVF and other infertility possibilities become let us say, "improved" spectacularly by these discoveries. Women's health generally could also be improved by maintaining some functions in the ovary throughout life. Let us be clear that with even more from these particular stem cells, a fascinating transformation of the whole of medicine lies ahead.

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Eggs from Stem Cells excite the imagination