Tension and Elasticity Contribute to Fibroblast Cell Shape in Three Dimensions

Abstract

The shape of animal cells is an important regulator for many essential processes such as cell migration or division. It is strongly determined by the organization of the actin cytoskeleton, which is also the main regulator of cell forces. Quantitative analysis of cell shape helps to reveal the physical processes underlying cell shape and forces, but it is notoriously difficult to conduct it in three dimensions. Here we use direct laser writing to create 3D open scaffolds for adhesion of connective tissue cells through well-defined adhesion platforms. Due to actomyosin contractility in the cell contour, characteristic invaginations lined by actin bundles form between adjacent adhesion sites. Using quantitative image processing and mathematical modeling, we demonstrate that the resulting shapes are determined not only by contractility, but also by elastic stress in the peripheral actin bundles. In this way, cells can generate higher forces than through contractility alone.

Mechanical stimulation of single cells by reversible host-guest interactions in 3D microscaffolds

“…The deviation between 2D and 3D can be explained by the restricted number of adhesions sites, which are limited to the four FN-coated beams in our case. Another important factor is the roundish 3D cell shape, which leads to more distributed forces than the strongly pinned and flattened cell shapes in 2D (32). Thus, if compared to cells adhering to a substrate and an atomic force microscope cantilever, our values for NIH 3T3 cells are in good agreement with the resulting force of 117 ± 21 nN measured by Webster et al (6).…”

Bimodal sensing of guidance cues in mechanically distinct microenvironments

“…1 , Supplementary Figure 1 ). Quantifying the free cell edge radii, R , provides a metric of linear tension ( λ ) in the arc relative to overall 2D normal tension ( σ ) within the cells following R = λ / σ 35 , 36 that has been used to accurately predict traction forces 37 . Force balance model analysis reveals that increased contractile forces scale with increasing R 28 , following R = ( F M / σ ) × ( L /( L − L 0 )), where F M is the average myosin-generated stress in the actomyosin assembly cross-section and relates to the linear tension following λ = ( F M ) × ( L /( L − L 0 )), where L relates to the actomyosin assembly length, and L 0 is a parameter that depends on the effective friction and viscosity of actin filaments resistance to shear.…”

“…Thus R increases linearly with myosin contractile forces that directly influence traction forces at the cell–matrix interface, particularly for our grid architecture that is specifically suited for formation of free cell edges between adhesions on two adjacent orthogonal lines, similar to adhesion on fiber networks, and consistent with reports demonstrating correlation between larger forces at adhesion sites and increased peripheral actin fibers with larger R 37 . In addition, the data shows a linear correlation between R and spanning distance, d 28 , 35 , 36 , thus we also calculated the R / d metric since our system allows for adhesion at different distances (i.e., different spanning distances; Fig. 1b ).…”

Distinct roles of nonmuscle myosin II isoforms for establishing tension and elasticity during cell morphodynamics

“…We produced cross-shaped FN-micropatterns via microcontact printing, which restrict FA formation to the pattern but still provide a sufficient adhesive area for the spreading of U2OS cells (see methods section for details). U2OS WT and all KO cell lines adapted their shape to the pattern and gained a striking phenotype with concave, inward bent actin arcs that line the cell contour as previously described for various cell types (Figure 2) (Bischofs et al, 2008;Brand et al, 2017;Kassianidou et al, 2019;Labouesse et al, 2015;Tabdanov et al, 2018;Thery et al, 2006). These arcs bridge passivated substrate areas and have a circular shape.…”