Microglia show differential transcriptomic response to Aβ peptide aggregatesex vivoandin vivo

Aggregation and accumulation of amyloid-β (Aβ) is a defining feature of Alzheimer’s disease (AD) pathology. To study microglial responses to Aβ, we applied exogenous Aβ peptide, in either oligomeric or fibrillar conformation, to primary mouse microglial cultures and evaluated system level transcriptional changes and then compared these to transcriptomic changes in the brains of CRND8 APP mice. We find that primary microglial cultures have rapid and massive transcriptional change to in response to Aβ. Transcriptomic responses to oligomeric or fibrillar Aβ in primary microglia, though partially overlapping, are distinct and are not recapitulated in vivo where Aβ progressively accumulates. Furthermore, though classic immune mediators show massive transcriptional changes in the primary microglial cultures, these changes are not observed in the mouse model. Together, these data extend previous studies which demonstrate that microglia responses ex vivo are poor proxies for in vivo responses. Finally, these data demonstrate the potential utility of using microglia as biosensors of different aggregate conformation, as the transcriptional responses to oligomeric and fibrillar Aβ can be distinguished.