Researchers Shed Light on How Cells Keep Moving Without Sticking to Surfaces

The speed of cell movement - called cell velocity - has long been speculated to be affected by the adhesive potential of the surface underneath it, although the exact mechanisms remain unknown. Now, a new study has answered this decades-long question.

A research team from the Max Delbrück Center (MDC) for Molecular Medicine in the Helmholtz Association (MDC) together with the Ludwig Maximilians Universität München (LMU) have discovered the mechanics behind cell velocity and developed a mathematical model that describes the forces involved in this aspect of cell mechanics. Researchers submitted their report in the journal Proceedings of the National Academy of Sciences (PNAS).

Cell Movement and Its Potential Applications

In biology and medicine, cell movement is a basic process that is particularly important during developmental stages when cells start differentiating into specialized cell types and start moving to the correct tissues where they will be working. Cells are also deployed to repair wounds and damaged tissues. On the other hand, cancer cells tend to crawl to the closest blood vessel that will carry it to other parts of the body.

"The mathematical model we developed can now be used by researchers to predict how different cells will behave on various substrates," shares Martin Falcke, head of MDC Mathematical Cell Physiology Lab and co-author of the study, from an MDC news article.

He adds that understanding of the mechanisms behind cell movement could help to advance studies against tumor metastasis, with potential applications in developmental biology and cancer treatment.

Collaborative Effort to Understand Cell Movement

The discovery was made possible with help from LMU experimental physicists who worked with MDC's theoretical physicists.

From the experimentalists' side, under the leadership of LMU professor Joachim Rädler, monitored the movement of more than 15,000 cancer cells moving along narrow lanes on a sticky surface, with the adhesion moving between low and high.

This setup allowed researchers to observe cell transitions under varying adhesion levels, simulating the changing environment inside the body.

The large dataset from this experiment was collated by Falcke and Benham Amiri, PhD student in Falcke's lab and co-first author of the paper, developing a mathematical model that captures the forces involved in the process.

"Previous mathematical models trying to explain cell migration and motility are very specific, they only work for one feature or cell type," Amiri notes, adding that they only try to keep it "simple and general as possible."

The mathematical equation derived matched the LMU experimental data gathered and remained accurate across different cell types observed over the last three decades.

Effect of Friction on Cell Velocity

Cells move by pushing the membrane toward the direction of movement, expanding and contracting its internal filament before peeling off its back end. The speed at which this process occurs depends largely on adhesion bonds between the cell membrane and the surface in contact underneath it. Without these bonds, the cell can't move because it can't push against the surface under it.

More bonds create more friction, allowing the cells to push harder, generate force, and move faster. However, too much adhesion with the surface would cause the cell to experience a slowing down in its movement - too much stickiness makes it difficult for the cell to pull off its back end.