Poster abstracts

Poster number 30 submitted by Kevin Walsh

Magnetic Mapping of Iron in Brain Tissue from Alzheimer’s Disease

Kevin Walsh (Biophysics Program, The Ohio State University), Stavan Shah (Department of Biomedical Engineering, The Ohio State University), Ping Wei (Department of Neuroscience, The Ohio State University), Sam Oberdick (Physics Department, University of Colorado, Boulder), Dana McTigue (Department of Neuroscience, The Ohio State University), Gunjan Agarwal (Department of Mechanical and Aerospace Engineering, The Ohio State University)

Abstract:
Iron (Fe) is an essential metal involved in a wide spectrum of physiological functions in the body, such as oxygen transport and enzymatic reactions. The oxidation state, mineral composition and storage of iron play a crucial role in health and disease. Several neurodegenerative diseases, including Alzheimer’s Disease (AD), are characterized by tissue iron deposits which can differ in size and composition from physiological iron deposits. Histochemical staining, the routinely used approach to characterize iron distribution, offers limited insight into the chemical environment and composition of tissue iron. One of the properties of iron which has not been adequately exploited in histology is the magnetic behavior of tissue iron. In this study, coronal slices the left hemisphere of AD brain samples were examined by magnetic resonance imaging (MRI) to determine magnetic signatures (T2 and T2*) of aggregated iron to certain regions of the brain. Perl’s histochemical staining and immunohistochemical staining for microglia were used to map the spatial distribution of ferric iron (Fe3+) in highly effected areas associated with AD, namely the hippocampus, subiculum and putamen. Adjacent, unstained sections were analyzed via magnetic force microscopy (MFM). MFM, an atomic force microscopy (AFM)-based technique, was utilized for magnetic mapping of iron in histological sections. Finally, hippocampus samples that underwent MFM analysis, were subjected to scanning electron microscopy with electron dispersion x-ray spectroscopy (SEM-EDS) to correlate the physical characteristics and chemical composition of iron deposits found in MFM. These results will allow for insight into the physiological and pathological state of iron oxide deposits in AD, ferrihydrite and magnetite/maghemite, respectively. This in turn will allow for better interpretation of the quantity and quality of iron allowing for better clinical interpretations commonly found using MRI.

References:
Walsh, K. J., Shah, S. V., Wei, P., Oberdick, S. D., Dickson-Karn, N. M., McTigue, D. M., & Agarwal, G. (2020). Effects of fixatives on histomagnetic evaluation of iron in rodent spleen. Journal of Magnetism and Magnetic Materials, 521(P1), 167531.
Blissett, A. R., Deng, B., Wei, P., Walsh, K. J., Ollander, B., Sifford, J., Sauerbeck, A. D., McComb, D. W., McTigue, D. M., & Agarwal, G. (2018). Sub-cellular In-situ Characterization of Ferritin(iron) in a Rodent Model of Spinal Cord Injury. Scientific Reports, 8(1), 3567.

Keywords: magnetic force microscopy, iron, Alzheimers disease