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BP: Fachverband Biologische Physik

BP 1: Cell Migration and Tissue Dynamics

BP 1.5: Vortrag

Montag, 25. Februar 2008, 11:15–11:30, C 243

Strain Energy during Cell Invasion in Three-Dimensional Collagen Gels — •Thorsten M. Koch¹, Stefan Münster¹, Claudia T. Mierke¹, Philip Kollmannsberger¹, James P. Butler², and Ben Fabry¹ — ¹Department of Physics, University of Erlangen-Nuremberg, Germany — ²Physiology Program, Harvard School of Public Health, Boston, USA

Cell invasion through a dense 3-dimensional matrix is believed to sensitively depend on the ability of cells to generate traction forces. To quantify cell tractions, we measured the strain energy of MDA-MB-231 breast carcinoma cells that invaded into a reconstituted collagen gel (G′=80 Pa, 500µm thickness, average mesh size 1µm). Alternatively, we also suspended cells in the collagen solution prior to polymerization. In both cases, cells assumed an elongated spindle-like morphology and locally contracted the gel. The undeformed state of the gel was measured after addition of the actin-disrupting drug cytochalasin-D. Gel deformations were quantified by tracking the spatial positions of fluorescent beads (⊘ 1 µm) embedded in the gels. The bead positions served as nodes for a finite element tessellation. From the local strain of each element and the elasticity of the collagen, we computed the local strain energy stored in the collagen gel surrounding the cell. This technique was verified by indenting the surface of the gel with a steel sphere (⊘ 100 µm, gravitational force 35.4nN). The strain energy of invaded cells was 14pJ, compared to only 1.01pJ of cells on a 2-D planar surface. These results demonstrate that tumor cells exert substantial traction forces during invasion.