Noninvasive imaging of rat-derived microglia and its reactivity to inflammatory molecules via acoustic impedance microscopy

• Published in: Journal of medical ultrasonics (2001) 2024-01, Vol.51 (1), p.29-37
• Main Authors: Lee, Christine Li Mei, Yap, Pey Shin, Umemura, Kiyoshi, Shintani, Taichi, Kobayashi, Kazuto, Hozumi, Naohiro, Yoshida, Sachiko
• Format: Article
• Language: English
• Subjects: Acoustics; Adenosine Triphosphate - pharmacology; Animals; Electric Impedance; Imaging; Inflammation - diagnostic imaging; Medicine; Medicine & Public Health; Microglia; Microscopy, Acoustic - methods; Original Article–Physics & Engineering; Original –Physics & Engineering; Radiology; Rats; Ultrasound
• ISSN: 1346-4523; 1613-2254; 1613-2254
• DOI: 10.1007/s10396-023-01379-8

Purpose Microglia, the brain's immune cells, play important roles in neuronal differentiation, survival, and death. The function of microglia is deeply related to the morphologies; however, it is too complex to observe conventionally and identify the condition of living microglia using optical microscopes. Herein, we proposed a new method to observe living cultured microglia and their reactivity to inflammation via the acoustic impedance mode of a scanning acoustic microscope. Methods Primary cultured microglia collected from rat pups exposed to acetamiprid, an insecticide, in utero were observed with both acoustic interface impedance mode (C-mode) and transparent three-dimensional impedance mode (B-mode). Results We characterized microglia into four types based on the results obtained from acoustic impedance, cytoskeletal information, and laser confocal imaging. Biphasic acoustic observation using B-mode and C-mode gave us information regarding the dynamic morphologies of living microglia treated with adenosine triphosphate (ATP) (600 μmol/L), which reflects distress signals from inflamed neurons. Acetamiprid exposure induced microglia response even in the neonatal period. ATP stimulus altered the shape and thickness of microglia with a change in the bulk modulus of the cell. Three-dimensional alteration with ATP stimulus could be observed only after biphasic acoustic observation using B-mode and C-mode. This acoustic observation was consistent with confocal observation using anti-Iba-1 and P2Y12 immunocytochemistry. Conclusion This study demonstrated the adequacy of using a scanning acoustic microscope in analyzing microglia's shape, motility, and response to inflammation.