The acoustic parameter by acoustic microscopy reveals the physiological transition of brain immune cells

Abstract Microglia (MG) is the innate brain immune cell that plays a vital role in inflammation and infection by releasing neurotoxins to sustain immunity. After encountering immune challenges, MG develops immune memory, influencing its responses to subsequent inflammatory stimuli. However, the dynamic and three-dimensional changes of MG to lipopolysaccharide (LPS) stimulation and memorizing process are unknown. This study investigates the morphological changes of MG to repeated LPS stimulation using the scanning acoustic microscopy (SAM) approach, a non-invasive acoustic visualizing device. Furthermore, we can observe cell adhesion in two-dimensional and three-dimensional analyses. We observed a significant decrease in acoustic impedance (AI) value in LPS-treated MG following the first hit, which was not replicated with subsequent hits. In contrast, the AI value in control MG exhibited continuous oscillations after all four hits. These results indicate that MG develops tolerance to LPS after initial exposure. We successfully characterized the morphology of MG using SAM.