CARS microscopy of Alzheimer's diseased brain tissue

Paper in proceeding, 2014

Alzheimera's disease (AD) is a progressive neurodegenerative disorder currently without cure, characterized by the presence of extracellular plaques surrounded by dystrophic neurites. In an effort to understand the underlying mechanisms, biochemical analysis (protein immunoblot) of plaque extracts reveals that they consist of amyloid-beta (Aβ) peptides assembled as oligomers, protofibrils and aggregates. Their spatial distribution has been confirmed by Thioflavin-S or immuno-staining with fluorescence microscopy. However, it is increasingly understood that the protein aggregation is only one of several mechanism that causes neuronal dysfunction and death. This raises the need for a more complete biochemical analysis. In this study, we have complemented 2-photon fluorescence microscopy of Thioflavin-S and Aβ immuno-stained human AD plaques with CARS microscopy. We show that the chemical build-up of AD plaques is more complex and that Aβ staining does not provide the complete picture of the spatial distribution or the molecular composition of AD plaques. CARS images provide important complementary information to that obtained by fluorescence microscopy, motivating a broader introduction of CARS microscopy in the AD research field.