Immune-integrated cardiac fibrosis-on-a-chip: a 3D microfluidic device for region–specific immune–cardiac crosstalk in the fibrotic heart

Cardiac fibrosis following myocardial infarction (MI) is driven by complex interactions among cardiomyocytes (CMs), cardiac fibroblasts (CFs), and immune cells, particularly macrophages. Current <i>in vitro</i> models often fail to capture the spatial heterogeneity and dynamic immune-cardiac crosstalk that are central to post-MI remodeling. Therefore, we aimed to develop a physiologically relevant cardiac fibrosis-on-a-chip model that integrates spatially patterned cardiac tissue architecture with region-specific immune cell delivery and mimic post-MI fibrosis. We engineered a three-layer microfluidic device seeded with human iPSC-derived CMs and CFs at defined ratios to replicate scar, border, and healthy regions. A valve-actuation system enabled the controlled introduction of iPSC-derived macrophages (iMacs) in a gradient pattern, mimicking their spatial distribution <i>in vivo</i>. TGF-β was used as a comparative biochemical stimulus to establish baseline fibrotic signaling. Immunostaining and computational modeling confirmed the spatial patterning of CM/CF and macrophage gradient distribution. This cardiac fibrosis-on-a-chip model provides an innovative and physiologically relevant system to investigate immune-mediated fibrosis. It enables region-specific analysis of immune-cardiac interactions and serves as a valuable model for therapeutic screening in fibrotic heart disease.