Untangling Hyaluronan-Protein Networks and Function

Abstract

Hyaluronan (HA), a polysaccharide present in the extracellular matrix (ECM) and attached to the plasma membrane of many cell types, is suspected to mediate a surprising number of biological functions. Researchers have puzzled over how such a relatively simple polysaccharide influences so many physiological processes. It is suspected that the wide array of hyaluronan binding proteins helps to modify the structure and activity of HA. These hyaluronan binding proteins are located in hyaluronan-rich tissues throughout the body: neurocan in the brain, versican in the skin, aggrecan in cartilage, TSG-6 in inflammatory processes. However, very little is understood about how these proteins interact with hyaluronan and lead to a restructuring of the local matrix. We employ video-based Particle Tracking Microrheology (PTMR) and Fluorescence Recovery After Photobleaching (FRAP) to characterize the mechanical and structural properties of hyaluronan-protein solutions. We have started by measuring the dependency of the viscoelastic shear moduli on frequency (1-1000 kHz) for highly-monodisperse HA solutions at four different molecular weights (160kDA, 500kDa, 1000kDa, 2500kDa). The HA concentration was varied to explore the scaling laws of the mechanical properties as predicted by polymer theory. FRAP is applied as a complimentary method to determine the mesh size and transport properties of the networks. These control studies of monodisperse HA prepare us for a detailed PTMR and FRAP study of hyaluronan-protein networks, particularly those formed with hyaluronan binding protein (HABP), the G1-domain of versican, and the link domain of TSG-6.