Quantitative descriptors for the effect of nature/mechanical properties of solid substrates on fibroblast morphology

Purpose: Cell shape is a powerful indicator of cell activity. This study aimed to validate the use of numeric descriptors for the assessment of the effect of substrate mechanical properties on the morphology of 2d cultured fibroblasts.
Methods: Two fibroblast cell types, the 3t3 murine cell line and primary Human dermal Fibroblasts (HDF) were cultured on substrates (fibrin, silicone, tissue culture PolyStyrene (TCPS)) with modulus values spanning more than six orders of magnitude (<1kPa - > 1 GPa), using cell area, circularity, aspect ratio and solidity (ratio between actual and convex area) as morphologic descriptors of cell shape. In order to reduce differences in chemical composition, silicones and TCPS were pre-treated with fibrinogen.
Results: Cell area and solidity appeared to be the most sensitive indicators of the differential dependency of the cell morphology on the nature of the substrate. They highlighted complex behavior, where the increase in modulus did not correspond to clear trends in cell shape over the complete range of moduli investigated.
Conclusions: The analysis of cell shape descriptors appears to indicate that chemical differences may overwhelm mechanical effects in 2d culture. These indications are partial and purely phenomenologic, but suggest that specific care should be paid to also consider the role of substrate chemistry in the analysis of the dependency of cell behavior on substrate mechanical properties.