The profiling and imaging of sterol molecules in the human brain

Abstract

For this project we had a unique opportunity to truly explore sterol molecules within the human brain of healthy and disease individuals. Cholesterol, and its derivative oxysterols, are quickly becoming an important topic within neurodegenerative diseases, with published literature suggesting altered sterol profiles from the peripheral fluid in individuals with these disorders. The main aims of this work were to analyse oxysterols and cholesterol in neurodegenerative disease human brain tissue and corresponding controls using homogenisation to look whether the sterol profiles differ in Alzheimer’s disease, multiple sclerosis and cerebrotendinous xanthomatosis. We also aimed to develop and optimise a method to image cholesterol across intact brain tissue sections and quantify the cholesterol in regions of interest using mass spectrometry imaging. We successfully achieved the quantification of oxysterols in all neurological disorders named above and identified some significant differences in specific sterol pathways and metabolites in Alzheimer’s and multiple sclerosis homogenate tissue samples. Notably, we optimised a method to quantify and visualise cholesterol across intact tissue sections using isotope-labelled standards and matrix-assisted laser desorption/ ionisation (MALDI) - mass spectrometry imaging (MSI) and found significant changes in cholesterol in several regions of interest, including the lesions of human multiple sclerosis brain tissue and the inflammatory edge of white matter lesions using this method. We also observed differences in white matter brain stem regions of Huntington’s disease mouse brain tissue. These results highlight the importance of our optimised MALDI-MSI cholesterol method, identifying important changes in tissue that cannot be seen with standard immunohistochemical staining techniques. These changes could be telling of pathologies and mechanisms at play in neurodegenerative diseases and could help target biomarkers for future treatments.