A Dynamic Gradient Stiffness Material Platform to Manipulate Cardiac Fibroblasts' Spatio-Temporal Behavior

After myocardial infarction, there exists a spatiotemporal variation of cardiac tissue stiffness across the infarcted border region outward to remote regions, influencing adverse remodeling and cardiac fibrosis, and this stiffness gradient changes over time. Here, a platform with dynamic, tunable, and reversible gradient stiffness can recapitulate in vitro the time-dependent stiffness range across the infarction border that occurs as part of the remodeling process is presented. This platform enables the observation of time-dependent interaction between cardiac fibroblasts and their mechanical microenvironment in a spatiotemporal manner. Specifically, the competition and cooperation of a chemical cue (antifibrotic drug) and mechanical cue (gradient softening) in tandem to attenuate the fibrotic responses of cardiac fibroblasts is examined. Applying a combined intervention showed either additive or antagonistic effects on fibrosis-related gene regulation compared to separate interventions of drug or softening. This work reveals the spatiotemporal variation of fibrotic response in cardiac fibroblasts as well as the complexity of antifibrotic drug dosing with stiffness changes and their combinatory effect on cardiac fibroblasts. This platform provides a unique in vitro tool to study disease progression mechanisms in a more clinically relevant microenvironment and also serves as a cost-effective model for potential therapeutic screening. Unique engineering approaches to in vitro systems are needed to mimic infarcted myocardium, with spatiotemporally varying stiffness, to study heart tissue remodeling. A substrate with dynamic stiffness gradients is engineered to temporally modulate stiffness representing the infarcted and remote regions, separately and simultaneously. These dynamic materials allow for investigating spatiotemporal cardiac fibroblast responses to stiffness gradient variations over time. image