Colloquium Series: Dr. Claire Dessalles, Université de Genève Switzerland

Join us on Zoom for our Colloquium Series. Dr. Claire Dessalles, postdoctoral fellow from Université de Genève Switzerland will be joining us to present “Active viscoelasticity of endothelial monolayers under anisotropic tension”.

Biography:

I started my postdoc in January 2022 in the Roux lab. Prior to coming to Geneva, I did my PhD in the Hydrodynamics laboratory at Ecole Polytechnique (France). My thesis is entitled Forces in a microvessel-on-chip: system development, poroelasticity mechanics and cellular response (see link below). I hold a Mechanical Engineering degree from Ecole Polytechnique  in France (2016) and an MSc in Bioengineering from EPFL in Switzerland (2018). I did my first master thesis in the Biophysics group at FAU in Erlangen (Germany) on cardiomyocytes mechanics and my second master thesis in the Microbs group at EPFL in Lausanne (Switzerland) on microactuators mechanics.

Research Synopsis: Cells in complex organisms are constantly subjected to tensile stresses due to tissue deformation. A prominent example of tension in the adult body is found in blood vessels that cyclically dilate as a result of the periodic pulsations of the heart. These traction forces are a key regulator of blood vessel development and stabilization, and abnormalities in the mechanical environment play critical roles in the development of vascular disease.
We developed a collagen hydrogel-based microvessel-on-chip that uses hydraulic actuation to generate controlled stretching of a confluent endothelial cell monolayer. Most systems for stretching impose a change in sample length (generating strain), while our platform directly controls the tension. Normal forces induced by the luminal pressure compress the surrounding soft hydrogel, dilate the channel, and create circumferential tension. Rigorous characterization of the system revealed the crucial role played by the poroelastic behavior of the hydrogel in determining the magnitudes of the strain and tension. Longitudinal and circumferential laser ablations of the monolayer confirmed the tension to be anisotropic.
This novel device was used to investigate the response of endothelial cells as a connective tissue to static traction forces. Over the course of 24 hours, the monolayer underwent a viscoelastic extension. Anisotropic tissue elongation was driven by cell elongation and alignment in the direction of the stress. The magnitude-dependent cell reorientation was accompanied by cytoskeletal reorganization from cortical actin to ventral stress fibers. The adherens junctions remodeled towards comb-like configurations that enabled transendothelial actin cables. These collective structural responses were highly dynamic and depended on the presence of adherens junctions.
In summary, we show that cytoskeletal and junctional remodeling enable viscoelastic extension in response to anisotropic tissue tension. This organ-on-chip was also shown to be compatible with epithelial cell culture, which opens up the possibility of investigating the role of anisotropic tension in the context of the gut, lungs or even during morphogenesis.

To register, please contact Melissa Gammon at mkgammon@email.UNC.edu.