Establishment of a method to evaluate the dynamics of highly chemotactic THP-1 cells during differentiation into monocyte-M1 macrophage-like cells.

Differentiation of the human monocytic leukemia cell line THP-1 is widely used to analyze the function of monocyte/macrophage-like cells in vitro. Although chemotaxis, a critical function of monocytes/macrophages enabling tissue accumulation, has been extensively studied, methods to evaluate sustained, long-distance chemotaxis remain underexplored. Therefore, we aimed to evaluate macrophage-like cells in vitro by differentiating THP-1 cells into monocyte/macrophage-like cells exhibiting sustained, strong chemotaxis over long distances (up to 260 μm). Using various reagents, we identified the combination of vitamin D, panobinostat, and granulocyte-macrophage-colony-stimulating factor as optimal for achieving high directionality and velocity in cell migration, as analyzed using the TAXIScan cell dynamics assay device. The differentiated cells matured into M1 macrophage-like cells and displayed reduced migratory capacity post-maturation, along with enhanced phagocytosis and reactive oxygen species production. Collectively, our differentiation and analysis methods provide a reliable platform for basic research into cellular maturation processes and drug development targeting the regulation of monocyte/macrophage dynamics.