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IRTG / Soft Matter Science
Freiburger Materialforschungszentrum
Stefan-Meier-Str. 21
79104 Freiburg, Germany

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You are here: Home Events PD Dr. Clemens Franz "Studying cell-matrix interactions using atomic force microscopy"

PD Dr. Clemens Franz "Studying cell-matrix interactions using atomic force microscopy"

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Young Scientist Group Nanobiology, DFG-Center for Functional Nanostructures Karlsruhe Institute of Technology, Germany

What
  • Seminar
When Jun 25, 2014
from 02:15 PM to 03:00 PM
Where Seminarraum A, FMF, Stefan-Meier-Str. 21
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The dual function as an imaging and force spectroscopy device makes AFM an extremely versatile tool in life science research. Here I describe several current applications of AFM as part of our effort to better understand biochemical, structural and mechanical aspects of cell adhesion to the extracellular matrix.

With AFM cell-matrix interactions can be visualized at the nanoscale. However, in adherent cells matrix these interactions occur primarily on the basal cell side, making them inaccessible to high-resolution, surface-scanning imaging techniques. Using a novel cell inverting technique, we have been able to expose the basal cell membrane for direct analysis by AFM in combination with fluorescence microscopy. Cells including their matrix adhesion sites remain intact during the inversion process and are transferred together with the complete array of basally associated matrix proteins. Molecular features of ECM proteins, such as the characteristic 67 nm collagen Dperiodicity, are preserved after inversion. Using this technique we also show distinct differences in the cellular remodeling of different matrix components. The presented cell inversion technique thus provides novel insight into nanoscale cell–matrix
interactions at the basal cell side.

Differential adhesion of individual cells to different matrix components governs a wide range of cellular functions. To elucidate differential adhesion processes on the single cell level, we prepared bifunctional adhesion substrates featuring adjacent laminin and collagen stripes, two major matrix components, and alternatingly measured CHO cell adhesion forces on both components by single-cell force spectroscopy. In repeated measurements (≥60) individual cells showed a stable and ECM typespecific adhesion response. All tested cells bound laminin more strongly, but the scale of laminin over collagen binding varied between cells. Together, this demonstrates that adhesion levels to different ECM components are tightly yet differently set in each cell of the population. Adhesion variability to laminin was nongenetic and cell cycle-independent but scaled with the range of integrin receptor expression on the cell surface. Adhesive cell-to-cell variations due to varying receptor expression levels thus appear to be an inherent feature of cell populations and should to be considered when fully characterizing population adhesion. In this approach, SCFS performed on multifunctional adhesion substrates can provide quantitative single-cell information not obtainable from population-averaging measurements on homogeneous adhesion substrates.

During tissue invasion, cells need to deform strongly to move through small pores in the extracellular matrix. Using artificial 3D porous cell culture matrices and AFM cell indentation measurements, we have studied the contribution of cell elasticity in this process. We show that factors decreasing cell nucleus stiffness positively regulate matrix invasion. Together, these applications demonstrate the versatility of AFM in studying cell-matrix interactions on the nanoscale.

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