Stretch regulated surface roughness controls macrophage inflammatory polarization through adhesion-chromatin coupling

Macrophages are early responders to biomaterial interfaces, but the specific role of surface roughness in regulating macrophage inflammatory phenotypes remains difficult to distinguish from the effects of substrate stiffness and other material properties. This study aimed to isolate the effect of surface roughness and clarify its role in macrophage-material interactions and inflammatory programming.

We developed a magnetic stretching device to impose controlled deformation on a thin polydimethylsiloxane (PDMS) membrane, thereby tuning its surface roughness. Atomic force microscopy was used to characterize surface topography and Young's modulus. RAW264.7 macrophages were cultured on stretched low-roughness membranes to evaluate cell morphology, cytoskeletal organization, focal adhesion kinase signaling, chromatin features, inflammatory marker expression, cytokine secretion, phagocytic activity, and adhesion force. NaOH-treated glass was further used as an independent material platform to validate the effects of roughness modulation.

Stretching significantly reduced PDMS surface roughness without measurably altering Young's modulus. Macrophages cultured on stretched low-roughness membranes showed increased spreading, reduced roundness, decreased F-actin intensity, and enhanced focal adhesion kinase signaling, suggesting altered cytoskeletal organization and stronger cell-material interactions. These changes were accompanied by increased chromatin density and decreased chromatin accessibility, while nuclear area remained unchanged. Functionally, stretched membranes promoted a pro-inflammatory phenotype, as indicated by increased TNF and IL-1 expression, elevated TNF-α secretion, enhanced phagocytic activity, and increased adhesion force measured by single-cell force spectroscopy. Validation experiments on NaOH-treated glass further confirmed that roughness modulation affected macrophage adhesion, chromatin accessibility, and inflammatory output across material platforms.

These findings identify surface roughness as a mechanically tunable regulator of macrophage inflammatory polarization. The results further suggest that roughness-dependent changes in cell-material adhesion may influence chromatin organization and accessibility, providing a potential adhesion-associated chromatin mechanism underlying macrophage inflammatory programming at biomaterial interfaces.