Dynamic remodeling of fiber networks with stiff inclusions under compressive loading

Tissue response to mechanical strain is important to biological processes like tissue development and maintenance; however, this relationship is not fully understood. Tissue mechanics are thought to be dominated by the extracellular matrix (ECM) consisting of a fibrous polymer network. However, these ECM polymer networks do not exhibit the compression stiffening response seen in real tissues. A model tissue system consisting of a fibrin network imbedded with inert stiff beads replicates this compression stiffening behavior. We employ bulk rheology and a custom imaging device to investigate the response of these fibrin-bead networks to uniaxial compression. The custom imaging device allows dynamic capture of network deformation at the mesoscale, a regime not previously well characterized. We find that the compression of fibrin-bead networks produces a series of remodeling processes, including the formation of a densified front, lateral stretching in the network, and fluid flow out the network. We argue the lateral network stretching is critical to the compression stiffening seen in these fibrin-bead networks. These findings are important to resolving challenges in tissue engineering at the intersection of physics, engineering, and medicine.