. "Was is it the evolutionary divergence of mice and men, or was there a developmental explanation, reflecting different stages of growth?"
This question spurred Pedersen and his team to challenge conventional wisdom and see whether the bio-chemical conditions used to maintain human embryo stem cells might work for mice too.
Previous attempts had failed. But when the researchers applied the human-specific molecular cocktail to a later stage of the mouse embryo rather than the three-day old blastocyst stage from which stem cells had always been drawn, suddenly it worked.
"Comparative analyses suggest that the new cells may have more in common with human embryo stem cells" than the ones taken earlier in the life cycle from mice, commented Ian Chambers, the head of embryonic stem cell biology at the University of Edinburgh, in an e-mail.
"These are exciting findings that hint at ways in which it may be possible to alter the culture conditions for human embryo stem cells in order to make their maintenance more straightforward and malleable," he said after reviewing the studies.
Kevin Eggan, a researcher at the Harvard Stem Cell Institute, also welcomed the studies, saying they could "shed light on the origin and nature of human embryonic stem cells."
The discovery of the epiblast stem cells in mice should make it easier to isolate stem cells in other species, livestock, as well as mice genetically modified to express a disease so that it can be studied, the authors of the studies said.
The growth factor -- called activin/Nodal -- that is now known to work for humans and mice may also unlock access to stem cells in these other species, said Pedersen.
One persistent problem in trying to use stem cells to produce specialised cells for treatment -- to make insulin in the pancreas or beating-heart cells, for example -- is an extremely low efficiency.
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