In a finding that can pave the way for growing replacement organs in the lab, researchers have for the first time succeeded in coaxing embryonic stem cells into becoming specialised cells.
About seven days after conception, cells start to specialise.
They take on characteristics that begin to hint at their ultimate fate as part of the skin, brain, muscle or any of the roughly 200 cell types that exist in people, and they start to form distinct layers.
"Understanding what happens in this moment, when individual members of this mass of embryonic stem cells begin to specialise for the very first time and organise themselves into layers, will be a key to harnessing the promise of regenerative medicine," said lead researcher Ali Brivanlou from Rockefeller University in the US.
Although scientists have studied this process in animals, and have tried to coax human embryonic stem cells into taking shape by flooding them with chemical signals, until now the process has not been successfully replicated in the lab.
But Brivanlou and colleagues found out that the missing ingredient is geometrical, not chemical.
"It brings us closer to the possibility of replacement organs grown in petri dishes and wounds that can be swiftly healed," Brivanlou added.
In the uterus, human embryonic stem cells receive chemical cues from the surrounding tissue that signal them to begin forming layers - a process called gastrulation.
Brivanlou and his colleagues confined human embryonic stem cells to tiny circular patterns on glass plates that had been chemically treated to form "micropatterns" that prevent the colonies from expanding outside a specific radius.
When the researchers introduced chemical signals spurring the cells to begin gastrulation, they found the colonies that were geometrically confined in this way proceeded to organise themselves just as they would have under natural conditions.
Cells that were not confined did not.
"At the fundamental level, what we have developed is a new model to explore how human embryonic stem cells first differentiate into separate populations with a very reproducible spatial order just as in an embryo," the researchers noted.
The findings were published in the journal Nature Methods.
