The new scaffold resembles an ultrafine carpet of "microposts," hair-like projections made of the elastic polymer polydimethylsiloxane---a key component in Silly Putty, Fu said. By adjusting the height of the microposts, the researchers were able to adjust the rigidity of the matrix.
In this experiment, the engineers used human mesenchymal stem cells, which are found in bone marrow and other connective tissues such as fat. The stem cells differentiated into bone when grown on stiffer scaffolds, and into fat when grown on more flexible scaffolds.
Once the researchers observed the cells differentiating according to the mechanical stiffness of the substrate, they decided to measure the cellular traction forces throughout the culturing process to see if they could predict how the cells would differentiate.
Using a technique called fluorescent microscopy, the researchers measured the bending of the microposts in order to quantify the traction forces.
"Our study shows that if the stem cells determine to differentiate into one cell type then their traction forces can be much greater than the ones that do not differentiate, or that differentiate into another cell type," Fu said. "We prove that we can use the evolution of the traction force as early indicators for stem cell differentiation."
The new matrix---manufactured through an inexpensive molding process---is so cheap to make that the researchers are giving it away to any interested scientists or engineers.
"We think this toolset provides a newly accessible, practical methodology for the whole community," Fu said.
|Contact: Nicole Casal Moore|
University of Michigan