Characterization and comparative analysis of a new mouse microglial cell model for studying neuroinflammatory mechanisms during neurotoxic insults

Microglia are the first responders of the central nervous system, acting as the key modulators of neuroinflammation observed during neurotoxic insults as well as in the pathophysiology of several neurodegenerative disorders including Alzheimer's (AD), Parkinson's (PD), and Huntington's diseases (HD). The number of publications on microglia has increased steadily throughout the past decade because of immense interests in the neuroinflammation that precedes the neurodegenerative process. To study microglial biology and its role in modulating neuroinflammation, immortalized microglial cell lines derived from mice, rats, and humans have been developed. Among these, the BV2 mouse microglial cell line is the most well characterized and widely used cell culture model. However, even unstimulated BV2 cells exhibit an amoeboid, hypertrophied morphology, indicating a highly activated and inflammatory state compared to primary microglia, thus making them less than ideal for studying the low-dose effects of toxicants on microglial activation. Therefore, we performed an in-depth characterization of a recently developed mouse microglial cell (MMC) line, which we compared with primary mouse microglia (PMG) and BV2s to identify which cell line was best suited for studying the microglial response to neurotoxicants. Comparative analyses reveal that MMCs are strikingly more similar to PMGs in basal activity, morphology, and sensitivity, than are BV2s. Furthermore, basal nitrite and inflammatory cytokine levels are significantly higher in BV2s compared to MMCs. BV2 cells are also less reactive to the inflammagen LPS compared to MMCs, due to the higher basal activation state of BV2s. Collectively, our in-depth analyses of morphology, basal activity, and responsivity to two different stimuli (LPS, aggregated α-synuclein) demonstrate that MMCs closely mimic neonatal PMGs, and are discernibly more suitable than BV2s for studying the neuroinflammatory mechanisms of neurotoxicants.