Stress relaxation amplitude of hydrogels determines migration, proliferation, and morphology of cells in 3-D

Abstract

The viscoelastic behavior of hydrogel matrices sensitively influences the cell behavior in 3D culture and biofabricated tissue model systems. Previous reports have demonstrated that cells tend to adhere, spread, migrate and proliferate better in hydrogels with pronounced stress relaxation. However, it is currently unknown if cells respond more sensitively to the amplitude of stress relaxation, or to the relaxation time constant. To test this, we compare the behavior of fibroblasts cultured for up to 10 days in alginate and oxidized alginate hydrogels with similar Young’s moduli but diverging stress relaxation behavior. We find that fibroblasts elongate, migrate and proliferate better in hydrogels that display a higher stress relaxation amplitude. By contrast, the cells’ response to the relaxation time constant was less pronounced and less consistent. Together, these data suggest that it is foremost the stress relaxation amplitude of the matrix that determines the ability of cells to locally penetrate and remodel the matrix, which subsequently leads to better spreading, faster migration, and higher cell proliferation. We conclude that the stress relaxation amplitude is a central design parameter for optimizing cell behavior in 3-D hydrogels.

Unravelling cell migration: defining movement from the cell surface

“…The cell phenotype and the profile of the substrate determine which of these mechanisms are activated. For example, hydrogels with higher stress relaxation amplitudes seem to promote cell penetration and ECM remodeling [ 35 ]. This would enhance cell elongation, migration, and proliferation [ 35 ].…”

“…For example, hydrogels with higher stress relaxation amplitudes seem to promote cell penetration and ECM remodeling [ 35 ]. This would enhance cell elongation, migration, and proliferation [ 35 ].…”

“…For instance, if we focus on the mechanical response of in vivo environments, they have been identified as viscoelastic [ 32 , 33 ] (they present properties observed in solids and fluids) and exhibit stress relaxation [ 34 ]. Interestingly, the impact of stress relaxation speed on 3D cell migration may be modulated by the material’s steric hindrance [ 35 ]. Still, hydrogels used as synthetic substrates for 3D culture and tissue engineering in vitro are typically elastic.…”