Effect of Cell Environment on ECM Production and Gene Expression in Poly ( ethylene glycol ) / Chondroitin Sulfate Hydrogels

Introduction A common approach to engineer cartilaginous tissue is to encapsulate chondrocytes in hydrogels that provide a three-dimensional environment to regulate cell function and guide extra-cellular matrix production. Cell environment can be controlled through gel chemistries and exposure to soluble factors. Our group has been particularly interested in poly(ethylene glycol) (PEG) based hydrogels; however, we recently synthesized chondroitin sulfate (ChSA) based macromers that can be systematically copolymerized with PEG macromers to form copolymer networks. The rationale behind incorporating ChSA into the networks is multifold. First, ChSA is the principle proteoglycan in cartilage. The presence of ChSA in gels provides a more natural environment for the chondrocytes and might stimulate cartilage production. Second, chondrocytes should recognize ChSA and be able to degrade and reorganize it as needed. Thirdly, the negative charge on ChSA imparts a high degree of swelling while simultaneously improving their mechanical properties. The goal of this work was to investigate the effect on gel mechanics, extracellular matrix production, and gene expression of incorporating ChSA into PEG based hydrogels.