Manipulating the mechanics of extracellular matrix to study effects on the nucleus and its structure

Tissues such as brain, muscle, and bone differ greatly not only in their biological functions but also in their mechanical properties. Brain is far softer than muscle while bone is the stiffest tissue. Stiffness of extracellular microenvironments affects fundamental cell biological processes such as polarization and DNA replication, which affect nuclear size, shape, and levels of nuclear proteins such as the lamins that modulate gene expression. Reductionist approaches have helped dissect the effects of matrix mechanics away from confounding biochemical signals. Here, we summarize materials and methods for synthesizing and characterizing soft and stiff synthetic hydrogels widely used for mechanobiological studies. Such gels are also easily made to mimic the mechanical heterogeneity of fibrotic tissues. We further describe a nano-thin collagen fiber system, which enables control of anisotropy in addition to stiffness. With the different systems, we illustrate the effects of matrix mechanics on nuclear size, shape, and proteins including the lamins.