High-Resolution 3D Reconstruction Reveals Intra-Synaptic Amyloid Fibrils

beta-Amyloid (A beta) accumulation and aggregation are hallmarks of Alzheimer's disease (AD). High-resolution three-dimensional (HR-3D) volumetric imaging allows for better analysis of fluorescence confocal microscopy and 3D visualization of All pathology in brain. Early intraneuronal A beta pathology was studied in AD transgenic mouse brains by HR-3D volumetric imaging. To better visualize and analyze the development of A beta pathology, thioflavin S staining and immunofluorescence using antibodies against A beta, fibrillar A beta, and structural and synaptic neuronal proteins were performed in the brain tissue of Tg19959, wild-type, and Tg19959-YFP mice at different ages. Images obtained by confocal microscopy were reconstructed into three-dimensional volumetric datasets. Such volumetric imaging of CA1 hippocampus of AD transgenic mice showed intraneuronal onset of A beta 42 accumulation and fibrillization within cell bodies, neurites, and synapses before plaque formation. Notably, early fibrillar A beta was evident within individual synaptic compartments, where it was associated with abnormal morphology. In dendrites, increasing intraneuronal thioflavin S correlated with decreases in neurofilament marker SMI32. Fibrillar A beta aggregates could be seen piercing the cell membrane. These data support that A beta fibrillization begins within AD vulnerable neurons, leading to disruption of cytoarchitecture and degeneration of spines and neurites. Thus, HR-3D volumetric image analysis allows for better visualization of intraneuronal A beta pathology and provides new insights into plaque formation in AD. (Am J Pathol 2011, 170:2551-2558. DOI: 10.1016/j.ajpath.2011.07.045)