Evaluating the Effects of Chondroitin Sulfate and Hyaluronic Acid in Modifying the Properties of Collagen-Based Matrices.

The extracellular matrix (ECM) enveloping cells in living tissue is comprised of signaling and structural support molecules. The ECM is vital to maintenance of normal tissue as it controls cell signaling and is a semiporous barrier to interstitial fluid flow. Two important types of ECM molecules are fibrillar collagen (e.g. type I) and glycosaminoglycans (GAGs). In certain solid tumors, hyaluronic acid (HA) and chondroitin sulfate (CS) are two types of GAG molecules that are known to be unusually abundant. These GAGs are negatively charged with the propensity to imbibe aqueous fluid and promote tissue swelling. While many studies have described the effect each molecule has on shaping ECM properties, studies describing how the CS and HA interact with each other are much less common. This study uses an integrated approach to characterize the effects of HA and CS on fluid transport (hydraulic permeability), stiffness (indentation modulus), collagen polymerization kinetics (turbidity), and matrix microarchitecture (pore size and fiber radius). Utilizing a microfluidic approach to study hydraulic permeability observed that the addition of GAGs decreased convective fluid transport. Indenting the hydrogels with a macroscale indenter demonstrated no changes in stiffness when adding CS, while HA, and CS/HA increased hydrogel stiffness. Analysis of confocal reflectance microscopy images showed increases in both pore size and fiber radius with the addition of both GAG molecules. Finally, turbidity measurements concluded that adding GAGs to a collagen gel accelerated its polymerization, with the change in fiber radius being the primary determinant in enhanced fibril formation. This study provides additional evidence that GAGs play an important role in defining physical properties of the ECM and demonstrates further ways into controllably modifying collagen based hydrogels via the addition of native ECM molecules.