Transcriptional signature in microglia isolated from an Alzheimer's disease mouse model treated with scanning ultrasound

Transcranial scanning ultrasound combined with intravenously injected microbubbles (SUS^+MB) has been shown to transiently open the blood–brain barrier and reduce the amyloid-β (Aβ) pathology in the APP23 mouse model of Alzheimer's disease (AD). This has been accomplished through the activation of microglial cells; however, their response to the SUS treatment is incompletely understood. Here, wild-type (WT) and APP23 mice were subjected to SUS^+MB, using nonsonicated mice as sham controls. After 48 h, the APP23 mice were injected with methoxy-XO4 to label Aβ aggregates, followed by microglial isolation into XO4⁺ and XO4⁻ populations using flow cytometry. Both XO4⁺ and XO4⁻ cells were subjected to RNA sequencing and transcriptome profiling. The analysis of the microglial cells revealed a clear segregation depending on genotype (AD model vs. WT mice) and Aβ internalization (XO4⁺ vs. XO4⁻ microglia), but interestingly, no differences were found between SUS^+MB and sham in WT mice. Differential gene expression analysis in APP23 mice detected 278 genes that were significantly changed by SUS^+MB in the XO4⁺ cells (248 up/30 down) and 242 in XO⁻ cells (225 up/17 down). Pathway analysis highlighted differential expression of genes related to the phagosome pathway and marked upregulation of cell cycle-related transcripts in XO4⁺ and XO4- microglia isolated from SUS^+MB-treated APP23 mice. Together, this highlights the complexity of the microglial response to transcranial ultrasound, with potential applications for the treatment of AD.