Ligand Anchorage and Materials Stiffness to Modulate Cell Adhesion Signals
Final Report Abstract
Adherent cells are tightly regulated in their behavior by the mechanical characteristics of their environment. Different substrate and cell parameters are convoluted in the regulation of the mechanical cell response leading to controversies on underlying mechanisms, like the regulation on the level of biochemical reactions of signaling molecules or generic biophysical characteristics of elastic media. Our studies aimed on time resolved studies of biophysical as well as biochemical responses of cells during early cell adhesion in dependence on the elasticity of the substrate and the affinity of attached adhesion ligands. Our biophysical analysis of traction force evolution on elastic substrates support the idea that cell adhesion can be described by generic biophysical mechanisms. During cell spreading two sequential substrate independent regimes of considerable force generation could be distinguished. While the second regime with saturated traction force can be well described within linear elastic models, the first one, characterized by fast spreading and force increase, is suggested to be additionally affected by non-linear or dissipative contributions. Substrate parameters, in particular elasticity and ligand affinity, only affect kinetics and absolute levels of traction force quantities implying specific regulation on a biochemical level besides the underlying biophysical principles. In terms of a time resolved analysis of downstream biochemical events of the adhesion signaling cascade we were not successful owing to inherent technical hurdles in the analysis of small amounts of activated proteins of single cells on elastic substrates. We were only able to reveal minor insights in the time resolved assembly of signaling proteins of intracellular adhesion sites in dependence on substrate parameters. However, this analysis already showed that it is indeed possible to correlate intracellular biochemical events to distinct biophysical responses in dependence on specific substrate parameters. In this context we envision newly developed intracellular protein sensors, based on FRET analysis, to become a tool to finally achieve insights in a time resolved analysis of the adhesion signaling pathway. In that way, our somewhat non-successful biochemical analysis should help for a better dissecting possible approaches for signaling pathway analysis of single cells on elastic media. Altogether, we believe that our biophysical experimental findings will stimulate further progress in the theoretical description of the dynamic cell behavior in viscoelastic environments. We are confident that we demonstrated the biomaterials properties of substrate elasticity and ligand affinity are both relevant parameters in designing functional materials for a controlled cell response.
Publications
- Dissipative Interactions in Cell-Matrix Adhesion. Soft Matter 9:6207-6216, 2013
Müller C, Müller A, Pompe T
(See online at https://doi.org/10.1039/c3sm50803j) - Modulating Cell Adhesion by Non-Covalent Ligand Attachment in: Cuerrier CM and Pelling AE (eds) Cells, Forces and the Microenvironment; Pan Stanford Publishing, 2014
M¨ller A, M¨ller C, Pompe T
- Distinct impacts of substrate elasticity and ligand affinity on traction force evolution. Soft Matter, 2016, 12, 272-280. First published on 30th September 2015
Müller C, Pompe T
(See online at https://doi.org/10.1039/c5sm01706h)
