Tuning the Microenvironment: Click-Crosslinked Hyaluronic Acid-Based Hydrogels Provide a Platform for Studying Breast Cancer Cell Invasion

A big challenge in cell culture is the non-natural environment in which cells are routinely screened, making in vivo phenomena, such as cell invasion, difficult to understand and predict. To study cancer cell invasion, extracellular matrix (ECM) analogs with decoupled mechanical and chemical properties are required. Hyaluronic acid (HA)-based hydrogels crosslinked with matrix-metalloproteinase (MMP)-cleavable peptides are developed to study MDA-MB-231 breast cancer cell invasion. Hydrogels are synthesized by reacting furan-modifi ed HA with bismaleimide peptide crosslinkers in a Diels–Alder click reaction. This new hydrogel takes advantage of the biomimetic properties of HA, which is overexpressed in breast cancer, and eliminates the use of nonadhesive crosslinkers, such as poly(ethylene glycol) (PEG). The crosslink (mechanical) and ligand (chemical) densities are varied independently to evaluate the effects of each parameter on cell migration. Increased crosslink density correlates with decreased MDAMB-231 cell invasion whereas incorporation of MMP-cleavable sequences within the peptide crosslinker enhances invasion. Increasing the ligand density of pendant GRGDS groups induces cell proliferation, but has no signifi cant impact on invasion. By independently tuning the mechanical and chemical environment of ECM mimetic hydrogels, a platform is provided that recapitulates variable tissue properties and elucidates the role of the microenvironment in cancer cell invasion.