Contributed Talk

Cell-generated forces and matrix remodelling in 3-D disease models

David Böhringer^1,2, Andreas Bauer¹, Christoph Mark¹, Ivana Moravec², Richard Gerum^1,3, Thomas Grundy⁴, Geraldine O'Neill⁴, Nadine Grummel¹, Pamela Strissel⁵, Reiner Strick⁵, Martin Steinmann², Jasmin Raufer⁶, Nico Reid⁶, Muhannad Alkassar⁶, Phuong A. Ngo⁷, Rocio Lopez-Posadas⁷, Ekkehard Goerlach², Martin Rausch², Ben Fabry¹

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Diseases such as fibrosis and cancer are often associated with disordered matrix remodeling and altered force generation. We developed and compared methods to quantify force generation of individual cells and cell assemblies (spheroids, organoids, tumoroids) in 3-D biopolymer matrices. To speed-up the computation time for 3-D force reconstruction, which can be prohibitively large in the case of cell assemblies, we introduced simplifications to exploit certain symmetrical constraints. For example, by exploiting the near-cylindrical symmetry of cardiac and skeletal muscle cells, we can simplify the force reconstruction algorithm to an algebraic expression that allows us to compute the contractility of individual muscle fibers in real-time. Similarly, by exploiting the approximately spherical symmetry in the far-field of the matrix displacements around contractile cells and cell assemblies, we measure the collective force generation of spheroids and organoids in real-time. We demonstrate that this technique can be applied to study the progression of intestinal inflammation and to explore the force-generation behavior of breast cancer-associated mesenchymal cells. Further, we demonstrate that cell-generated forces are tightly linked to matrix remodeling that we quantify by analyzing collagen fiber orientation and collagen intensity around individual cells and cell assemblies. This approach only requires imaging of the cell outline and of the fiber structure, and it can be applied without further knowledge of material properties or of the deformation-free equilibrium state. Together, these methods for quantifying force reconstruction and matrix remodeling are robust, user-friendly, and provide sufficiently high throughput to make them useful for other research questions focusing on the complex interplay between cells and their micro-environment.