A Novel Core–Shell Hydrogel 3D Model for Studying Macrophage Mechanosensing and Foreign Body Giant Cell Formation

The foreign body response (FBR) to biomaterials is primarily driven by macrophages. At implant sites, macrophages often fuse into destructive foreign body giant cells (FBGCs), yet FBGC-targeted treatments for FBR remain elusive. To fill this knowledge gap, a novel microscale core-shell hydrogel 3D model is developed using heterogeneous alginate-collagen microcapsules with varying matrix stiffness to culture macrophages. This 3D model more closely replicates in vivo conditions. This model is further used to investigate the effects of stiffness and TRPV4 (transient receptor potential vanilloid 4) on FBGC formation. Stiffer 3D hydrogel robustly enhances FBGC formation and F-actin production in wild-type macrophages compared to softer hydrogel, with IL4 and GMCSF priming amplifying these effects. Crucially, TRPV4-null macrophages exhibit reduced FBGC formation and F-actin production, underscoring TRPV4's role in mechanosensing. Further, the N-terminal residues 1-130 of TRPV4 are identified as critical for FBGC formation and F-actin generation. RNA-seq data reveal that TRPV4 modulates inflammatory, fibrotic, and mechanosensitive gene expression in macrophages in 3D environments, offering insights into how TRPV4 governs FBR. Overall, the data establish this 3D model as a powerful tool for biomaterials research and highlight TRPV4 as a key player in macrophage mechanosensing and FBGC formation in 3D condition.