Stem cells grown on 'soft carpets' function better

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The fluffiness of the medium of which human embryonic stem cells are growing affects the type of specialised cells they eventually become, a study shows.

The researchers coaxed human embryonic stem cells to turn into working spinal cord cells more efficiently by growing the cells on a soft, ultra fine carpet made of a key ingredient in Silly Putty.

"To realise promising clinical applications of human embryonic stem cells, we need a better culture system that can reliably produce more target cells that function well," said Jianping Fu, an assistant professor of mechanical engineering at University of Michigan.

"Our approach is a big step in that direction, by using synthetic micro-engineered surfaces to control mechanical environmental signals," he added.

This research is the first to directly link physical, as opposed to chemical, signals to human embryonic stem cell differentiation.

Differentiation is the process of the source cells morphing into the body's more than 200 cell types that become muscle, bone, nerves and organs.

Fu said the findings raise the possibility of a more efficient way to guide stem cells to differentiate and potentially provide therapies for diseases such as amyotrophic lateral sclerosis (Lou Gehrig's disease), Huntington's or Alzheimer's.

In the specially engineered growth system - the 'carpets' Fu and his colleagues designed - microscopic posts of the Silly Putty component polydimethylsiloxane serve as the threads.

The team found that stem cells they grew on softer carpets turned into nerve cells much faster and more often than those they grew on stiffer surfaces.

After 23 days, the colonies of spinal cord cells that grew on the softer micropost carpets were four times more pure and 10 times larger than those growing on either traditional plates or rigid carpets.

The researchers verified that the new motor neurons they obtained on soft micropost carpets showed electrical behaviours comparable to those of neurons in the human body.

"This is extremely exciting," Fu said.

Researchers believe stem cell therapies might help patients grow new nerve cells.

The study was published online in Nature Materials.