Xavier Trepat (IBEC)
We discovered that several types of cells are attracted to the most rigid areas of tissues. The discovery questions the traditional view that cell movement is guided primarily by variations in the chemical concentration of proteins and ions.
In 2000, researchers at Boston University and the University of Massachusetts first proposed that the stiffness of a tissue could guide the movement of isolated cells. However, subsequent studies showed that this experimental mechanism was very inefficient. Here we found that when cells cooperate with each other, they are able to respond to variations in tissue stiffness much more efficiently than when they are isolated.
It is an example of what is often called collective intelligence: a group can carry out a task that their isolated individuals are unable to perform. The key is not in any property of the individual, but in their interaction with their peers. In this case, the interaction is physical, cells transmit information between them by means of forces.
To reach our conclusions, we developed new techniques to create biomaterials with variations in stiffness, and used these to observe which cell groups preferentially moved to the more rigid areas. The larger the group, the more efficient the movement; and individual cells were unable to find their way to the most rigid areas.
We developed a theory explaining the phenomenon, which we named collective durotaxis. In the theory, each cell applies a force to its environment that allows it to measure the surrounding stiffness. But cells need to physically interact with each other to transmit this information collectively in order to move.
Tumors are more rigid than their surroundings, so collective durotaxis might contribute to explain the mechanisms by which tumor cells move to initiate the metastatic process. Similarly, scars are also more rigid than their surrounding tissues. As such, collective durotaxis might also explain how cells move to heal wounds.