Abstract: We performed experiments involving indentation-retraction/relaxation to observe the viscoelastic properties of epithelial cells undergoing shape alterations. MDCK II cells cultured on flexible polydimethylsiloxane substrates underwent lateral stretching, resulting in increased cortex contractility and reduced excess surface area. Consequently, cells maintained their fluidity but became inherently stiffer. This behavior was consistent across demixed cell monolayers of ZO-1/2 double knockdown (dKD) cells, cells exposed to varying temperatures, and following cholesterol removal from the plasma membrane. Conversely, individually tested cells adhered to differently sized patches showed no significant rheological changes. By sacrificing excess surface area, cells gained the ability to respond to mechanical challenges without compromising their fluidity, thus acquiring newfound flexibility that elucidates the fluidity-stiffness relationship.

MDCK cells also form multicellular cysts like acini or spheroids, comprised of a closed polarized cell monolayer enclosing a liquid. Tissue tension of these cysts is typically determined using Laplace's law by measuring internal pressure. We conducted force-relaxation experiments on MDCK II cysts and developed a theoretical framework to explain their response to external deformation, considering the potential super-viscoelasticity of the spheroids and volume leakage. Our findings showed that cells reduce tension upon deformation by thinning the cell monolayer, thus providing excess tissue area. This mechanism, which also protects individual cells from lysis, serves as a universal strategy on larger scales to withstand external stress.

Most human body organs consist of epithelial sheets, which are layers of cells exhibiting intricate and dynamic behaviors not observable in individual cells and challenging to predict by studying isolated cells. In this study, we investigate how the dynamics of cell sheets change concerning the integrity of cell-cell junctions, particularly focusing on cell-cell junctions and single cell contractility.

Biography:

1987-1989 Studies of Biology at the University of Münster

1989-1994 Studies of Chemistry at the University of Münster, with honor

1994-1997 PhD thesis under supervision of Prof. Dr. H.-J. Galla

1997-1998 Postdoctoral Researcher at the Scripps Research Institute (La Jolla, CA, USA)

1999-2001 Habilitation in Biochemistry at the University of Münster in the group of Prof. Dr.

H.-J. Galla and Prof. Dr. H. Fuchs

2001-2006 Associate Professor (C3) for Physical Chemistry at the University of Mainz

2006-2008 Full Professor (W3) for Biophysical Chemistry at the University of Mainz

since 2008 Full Professor (W3) for Biophysical Chemistry at the University of Göttingen

2011-2018 Vice-Speaker CRC 937

2013 - 2015 Dean of the Faculty of Chemistry in Göttingen

2022 – Director of the Institute of Physical Chemistry in Göttingen

2022- Vice Speaker RTG CYTA