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BP: Fachverband Biologische Physik

BP 16: Posters: Cell adhesion, mechanics and migration

BP 16.8: Poster

Montag, 16. März 2015, 17:30–19:30, Poster A

Traction Force Microscopy during Phagocytosis — •Wolfgang Groß and Holger Kress — Department of Physics, University of Bayreuth, Bayreuth, Germany

In the process of phagocytosis, cells internalize micrometer-sized objects like bacteria and dead cells, thus being a main function of innate immunity. After the detection of foreign particles, the membrane starts to wrap around the phagocytic target. This so-called phagocytic cup is mechanically supported by the polymerization of actin filaments in combination with myosin motors. Even though the molecular players have been identified, there is only few quantitative data describing the dynamics of the major regulators. Using the technique of traction force microscopy (TFM), we measure cellular forces during phagocytosis in a spatially and temporally resolved manner. As a substrate, we use thin polyacrylamide films with a thickness of a few tens of micrometers. To characterize the rheology of these films, we put millimeter sized steel spheres on the surface which are indenting the substrate. Our results suggest linear elasticity and a poisson value close to 0.5 for most gels, depending on the polymerization conditions. The results are consistent for multiple sphere radii and were verified by bulk tensile tests for different elastic moduli from 5 to 20 kPa. TFM allowed us to quantify forces, which J774-A1 macrophages exert when adhering to a fibronectin-coated gel. Preliminary data regarding phagocytosis shows the distribution of contractile forces in direct vicinity of the phagocytic target. We anticipate our results to pave the way for a more quantitative understanding of phagocytosis.