Dresden 2009 – scientific programme

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BP: Fachverband Biologische Physik

BP 4: Cell Mechanics

BP 4.3: Talk

Monday, March 23, 2009, 15:00–15:15, HÜL 186

The compaction of gels by cells: a case of collective mechanical activity — •Pablo Fernandez and Andreas R. Bausch — E27 Zellbiophysik, Technische Universität München, D-85748 Garching, Germany

With our growing understanding of force generation and transduction in biological systems, mechanics is acquiring the status of an organising principle connecting tissue architecture to single cell shape and phenotype. To understand mechanotransduction, purely mechanical phenomena resulting from the crosstalk between contractile cells and their elastic surroundings must be distinguished from adaptive responses to mechanical cues. Here, we revisit the compaction of freely suspended collagen gels by embedded cells (osteoblasts and fibroblasts), an amazing process where a small volume fraction of cells compacts the surrounding matrix by two orders of magnitude. We find it to be crucially determined by mechanical aspects. Gel compaction results from an anisotropic deformation following the mechanical anisotropy at the gel boundaries. The existence of a critical cell density shows the effect to be cooperative, revealing a mechanical interaction between cells. As a consequence of the nonlinear properties of biopolymer gels, the large deformations imposed by the cells irreversibly compact the matrix and render it anisotropic. This intricate interplay between contractility and matrix mechanics provides a robust structure-follows-shape principle with implications for the formation of tissues, and raises questions as to the nature of adaptive cytomechanical responses.