Cellular and molecular mechanobiology

Tissues in our body can be extremely soft such as breast or brain, or very stiff such as bone. Cells in our body constantly interact mechanically with such tissues, exerting, transmitting, withstanding, and detecting forces. This mechanical interaction with the environment regulates how cells proliferate, differentiate, and move, and regulates development, tumorigenesis or wound healing. 

Our research aims at unraveling – and re-engineering – the molecular mechanisms by which cells detect and respond to mechanical stimuli like forces or tissue rigidity, triggering downstream cell responses. 

Just like biochemical stimuli initiate signaling cascades, mechanical forces affect the links and conformation of a network of molecules connecting cells to the extracellular matrix. This molecular and cellular response to force constitutes the phenomenon of mechanotransduction. 

To study mechanotransduction, we combine biophysical techniques like magnetic and optical tweezers, Atomic Force Microscopy, traction microscopy, and microfabricated force sensors with molecular biology, advanced optical microscopy, and theoretical modelling. 

Sensing the environment: Using this multi-disciplinary approach, we have unveiled a molecular mechanism that cells employ to detect and respond to the rigidity of their environment, which could be crucial in breast tissue and breast cancer (Elosegui-Artola et al., 2016 Nat. Cell Biol., and Elosegui-Artola et al. 2014, Nature Mater.). This mechanism is mediated by what is known as a “molecular clutch”: in a surprising analogy with a car engine, cells can be understood as a molecular network that can engage and disengage from its environment, just as the clutch of a car. This affects force transmission from the environment to cells, and also within different cell components. We are also expanding on the idea of the molecular clutch, to explore how cell molecular engines sense not only mechanical rigidity, but other important parameters from their environment: for instance, the composition and distribution of ligands in the extracellular matrix, or other cells. In this regard, we uncovered that this concept can explain how cells sense the spatial distribution of ligands in the extracellular matrix (Oria et al., Nature 2017). We have also demonstrated that cell-cell force transmission, mediated by a molecular clutch, is essential for cells to sense gradients in stiffness (Sunyer et al., Science 2016, in collaboration with the group of Xavier Trepat).

Nuclear mechanotransduction: Forces applied to cells are transmitted all the way to the cell nucleus, where they affect its function. We are studying how this force transmission affects the dynamics of transcriptional regulators, such as YAP (Elosegui-Artola et al., 2017, Cell), and how this affects cell function.

The membrane as a mechanosensor: Due to its mechanical properties, the plasma membrane itself can respond to forces and act as a mechanosensor. Recently, we have shown that cell membranes can use purely physical principles to adapt their shape in response to mechanical forces (Kosmalska et al., 2015, Nat. Commun.). We are currently studying how cells harness this physical membrane behavior to respond to signals from their environment.

Ultimately, when we determine the molecular mechanisms that communicate cells with their environment, we will understand how forces determine development when things go right, and tumor formation when they go wrong.

Video: How tissue stiffness activates cancer