The researchers wondered if the way the cells are normally grown in culture could be the problem. After all, as Blau pointed out, cells are used to rubbing shoulders comfortably with their neighbors on all sides rather than being splayed out and anchored on a rigid plastic culture dish that is 100,000-fold less elastic than true muscle.
To find out if the cells would be happier on a softer, more giving surface, they had to develop an entirely new culture system. They turned to a material called hydrogel, which is made up of a latticework of polyethylene glycol polymers filled with water. Decreasing the percentage of polymer molecules in the mix makes the resulting matrix more elastic and wobbly; increasing it makes it more dense and rigid.
Hydrogel is often used as scaffolding to grow cells in two- and three-dimensional arrays useful in tissue engineering. But because it can swell over time, it was not possible to accurately calibrate the amount of proteins and other components needed to maintain the cells in this type of experiment. Gilbert and Havenstrite tinkered with the system until they came up with a version that maintains a constant volume, making it possible to test the effects of gels of different elasticity that all contained the same amount of protein. They then patterned the gel into hundreds of tiny wells and added one freshly isolated muscle stem cell per well.
After letting the cells grow for one week, the researchers found that the softer, or more pliant, g
|Contact: Krista Conger|
Stanford University Medical Center