Cells adapt to shape-changing substrates

A research team at Syracuse University has used shape memory polymers to create a dynamic, shape-changing substrate on which cells can be grown.

This substrate, which can switch in texture from grooved to smooth, better mimics conditions found in the body and is expected to have many medical and research applications.

In the body, cells grow on the dynamic, changing surfaces of tissue and bone. Cellular interactions with substrate are known to have significant influence on processes such as embryogenesis, tissue development, intercellular communication and the progression of illness.

However, laboratory studies of cell biomechanics have so far been mostly limited to unchanging, flat surfaces.

“We sought to develop a new tool for cell culture that could actively change its properties under typical cell culture conditions,” Kevin Davis, the study’s first author, wrote in an e-mail to The News-Letter.

“It is known that cells are able to respond to surface topographies in culture, but previously there have been a limited number of tools available that could actually change their properties while cells were growing on them, making it difficult to study how cells respond to substrate changes or to use substrate changes to direct cell behaviors,” he wrote.

The research team took advantage of a type of molecule called shape memory polymers, which could be manipulated to permanently alter their shape by simply changing the temperature.

“These polymers have the ability to be deformed into a stable temporary shape and then later be triggered by an increase in temperature to return to a permanent, memorized shape,” Davis wrote. “We programmed our polymer to transition from a surface with micron scale grooves to a flat surface.”

The researchers first allowed the cells to attach onto the grooved surface. Then, after the cells had grown for nine and a half hours, they increased the temperature from 30 to 37 degrees Celsius. This temperature increase triggered the shape memory polymers to change to a flat surface.

After allowing the cells to grow another 19 hours on the flat surface, the researchers used fluorescence microscopy to analyze how the morphology of the cells had changed.

“We found that the cells were able to feel the two different topographies,” Davis wrote. “The cells oriented with the direction of the grooves when on the grooved surface. After increasing the temperature, the surface lost the grooves and transitioned to a flat surface. Cells on this surface were randomly oriented.”

To achieve this change in orientation, cells significantly remodelled their actin cytoskeletons.

Neither the temperature increase, nor the substrate’s shape change, decreased the survival of the cells themselves.

The methods developped in the current study are expected to have applications in medical devices, such as the scaffolding used during surgical procedures and in tissue engineering.

Shape memory polymers also have many potential applications in cell biology research. Cell movement, interactions between cells, cell differentiation and cell traction are all processes which are affected by the shape and texture of the substrate.

“In the future, we hope to use the substrates to study the mechanisms by which a cell feels the change in surface topography and to use these changes to direct cell behaviors for tissue engineering and regenerative medicine purposes,” Davis wrote.