Collagen is a protein found within tissue that provides both structure and stability to tissues and their cells. This protein is able to not only suppor,t but provide a cushion of sorts to surrounding cells, easily transitioning between being elastic and fluid – hence why it is known often compared to ‘Silly Putty’. Researchers at Stanford have finally discovered just how the protein is able to alter between two very contradictory properties.

Researchers discovered that in response to deformation, collagen networks stiffen. The stiffer they become, the faster they then soften. The team hopes their findings will provide more insight into the creation of new techniques for bioengineering tissue used in regenerative medicine. Scientist may be able to target the forces that direct cells, in turn nudging them to grow in a specific way.

Stanford assistant professor of mechanical engineering and associate member of the Standford Cancer Institute, Bio-X, ChEM-H and the Standford Biophysics Program, Ovijit Chaudhuri says that uncommon to popular belief, cells respond to more than just chemical cues. They are also known to respond to mechanical cues. He uses this knowledge to take a deeper look at the natural progression of breast cancer and how mechanical properties can be engineered in order to regenerate tissues. Chaudhuri says that by increasing tissue stiffness, the breast cancer actually spreads much faster. Because of this, he claims that physical force plays a major role in how cells function just as much as the microenvironment does. Researchers have applied these findings to collagen networks by using something known as atomic force microscopy to apply forces on a molecular level.

Co-author Sungmin Nam, a mechanical engineering graduate student says that collagen biopolymers are connected together very similar to a fishing net. They are not very strong and have a high likelihood of becoming weak. Nam says the latest research suggests weak cross-links contain a unique quality that causes unbinding in the event of applied force. In simpler terms, the most important findings of the entire study is the fact that the more strain you put on the collagen, the quicker it will retract to its normal state upon release.

This work implies that collagen mechanics may directly control how cells behave and monitor such behavior. Nam says that now that it is known how strongly cells interact with their microenvironments and that polymers directly manipulate these environments which will help gain better insights into exactly how cells and collagen interact with one another. This will assist in the future development of new 3D technologies that focus on tissue regeneration as well as cell cultures.

All research for the study was in support by the Jeongsong Cultural Foundation, the Samsung Scholarship for S.N. and the the Standford Child Health Research Institute.

Their latest study, Strain-Enhanced Stress Relaxation Impacts Nonlinear Elasticity in Collagen Gels, was published on May 2nd, 2016 in the Proceedings of the National Academy of Sciences.