Impact of Viscosity on Human Hepatoma Spheroids in Soft Core-Shell Microcapsules

Extracellular environment regulates structures and functions of cells, from molecular up to the tissue level. However, underlying mechanisms that influence organization and adaptation of cancer in 3D environments are not yet fully understood. In this study, we investigate the influence of viscosity of the environment on the mechanical adaptability of human hepatoma cell (HepG2) spheroids in vitro, using hybrid 3D microcapsule reactors formed with droplet-based microfluidics. To mimic the environment with different mechanical properties, HepG2 cells are encapsulated in hybrid alginate core- shell microcapsules with tunable core viscosities achieved by incorporating carboxymethylcellulose. The significant changes in cell and spheroid distribution, proliferation, and cytoskeleton are observed and quantified. Importantly, changes in expression and distribution of F-actin and keratin 8 indicate that the spheroid stiffness varies with viscosity of the surrounding medium. The increase in F-actin levels in viscous medium can be indicative of enhanced tumor cell ability to traverse dense tissue. These results demonstrate that cancer cell assemblies (scale ca. 200-300μm) are able to dynamically adapt to the changes of extracellular viscosity, which holds promise for advancing our understanding of the mechanical characteristics of cancer entities development.