The Micromechanics of Cellularized Extracellular Matrix

Abstract

Collagen gels are widely used in experiments on cell mechanics because they mimic the extracellular matrix in physiological conditions. Collagen gels are often characterized by their bulk rheology; however, variations in the gel microstructure and cell adhesion forces cause the mechanical properties to be inhomogeneous at the cellular scale. We study the mechanics of type I collagen on the scale of tens to hundreds of microns by using holographic optical tweezers (HOT) to apply pN forces to microparticles embedded in the collagen network. We find that in response to optical forces particle displacements are inhomogeneous, anisotropic and asymmetric. Gels prepared at 21C and 37C show qualitative difference in their micromechanical characteristics. We also demonstrate that contracting cells remodel the micromechanics of their surrounding extracellular matrix in a strain- and distance- dependent manner.