Rigidity of the Substrate

How are the mechanical properties of the ECM probed by cells In other words, what cellular machinery is used to sense and respond to the local substrate rigidity This active molecular rheometer is essentially composed of two modules a probe and a transducer The probe is required to generate traction forces and convey them to the substrate. The second module generates intracellular signals based on the mechanical response of the matrix. 

Experimentally different approaches have been used to produce substrates with controlled stiffness. A partial summary of the quantitative results obtained is reported in Table 12.3. 

The lack of focal adhesion reinforcement results in the dispersal of the focal adhesion site. 

Cell type Material Mechanical properties Effect on FAs Cell response Ref. 

I coating of the micropillars array is visualized by immunofluorescence labeling and confocal imaging (c). From the insert where bent pillars are imaged, it is clearly seen that the protein layer (shown in green) is restricted only to the top of the pillars, which were visualized in reflection (courtesy of Dr. Jens Ulmer). 

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The commercial finite element program, Abaqus [17], was used to calculate the stress distribution in an edge delamination sample. A fully three-dimensional model of the combinatorial edge delamination specimen was constructed for the finite element analyses (FEA). For clarity, some of the FEA results and schematics are presented as two-dimensional configurations in this paper (e.g.. Fig. 1). The film and substrate were assumed to be linearly elastic. The ratio of the film stiffness to the substrate stiffness was assumed to be 1/100 to reflect the relative rigidity of the substrate. This ratio also represents a typical organic... 

Rigidity of the substrate - Cells apply force to the developing adhesions through acto-myosin contractility. The mechanical response of the matrix controls the... 

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