A study by the University of Michigan (U-M) shows that the sponginess of the environment where human embryonic stem cells grow affects the type of specialized cells they eventually become. The researchers made human embryonic stem cells turn into working spinal cord cells more efficiently by growing the cells on a soft, ultrafine carpet made of a key ingredient in Silly Putty. Their study is published online in Nature Materials.
This research links physical signals to human embryonic stem cell differentiation. Jianping Fu, U-M assistant professor of mechanical engineering, says the findings show a more efficient way to guide stem cells to differentiate and may provide therapies for diseases such as Lou Gehrig’s disease, Huntington’s, or Alzheimer’s.
Microscopic posts of the Silly Putty component polydimethylsiloxane serve as the threads in the ‘carpets’ of the specially designed system. The researchers varyied the post height to adjust the stiffness of the surface they grew the cells on. The study showed that stem cells grown on the tall, softer micropost carpets turned into nerve cells much faster and more often than those grown on the 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.
In addition, the researchers verified that the new motor neurons they obtained on soft micropost carpets showed electrical behaviors comparable to those of neurons in the human body. They also identified a signaling pathway involved in regulating the mechanically sensitive behaviors. The pathway they studied, called Hippo/YAP, is also involved in controlling organ size, which can both cause and prevent tumor growth.
Source: University of Michigan