Improve and Validate Amyloid Pathology Visualization and Analysis in Intact Brain Samples - Project Summary Alzheimer's disease (AD) represents a profound clinical and scientific challenge, with its pathogenesis still unsettled and with no curative treatment available to date. Amyloid β protein (Aβ), the primary component of the extracellular plaques of AD, plays an important role in disease progression and forms the basis of the amyloid cascade hypothesis. Consequently, decades of intensive research have focused on the molecular and cellular physiology of Aβ, leading to numerous insights into its local neurotoxic effects and its role in AD-related pathology. However, despite these advances, how Aβ pathology evolves across the whole brain throughout the different stages of AD remains insufficiently understood. Particularly, it remains unclear whether the spread of Aβ is influenced by factors such as neuronal connectivity, cerebrospinal fluid flow, or intercellular transmission mechanisms. Recently, with the advancement of tissue clearing techniques, growing optical imaging efforts have been made to investigate the whole brain Aβ distribution to deepen our understanding of AD pathogenesis. Nevertheless, current whole-brain fluorescence imaging approaches face two fundamental limitations. First, due to the inherently slow diffusion rate of antibodies, uniform immunolabeling in intact mammalian brains requires prolonged incubation times, making it virtually infeasible for intact human brains. Second, the limited quantum yield of fluorescent molecules fundamentally constrains imaging throughput. These challenges significantly hinder the adoption of fluorescence imaging for whole-brain and large-cohort studies of Aβ mapping. In contrast, elastic scattering conserves both photon and system energies, fundamentally overcoming the limitations imposed by finite fluorescence yield. This enables the detection of coherently scattered photons with throughput up to three orders of magnitude higher. Lately, we developed such a prototype scattering imaging system, termed Clearing-Assisted Scattering Tomography (CAST), which provides high-throughput, label-free imaging of Aβ pathology in intact mouse brains. In this project, we aim to further enhance and validate the scattering contrast of amyloid pathology in optically cleared AD brain samples. By optimizing tissue clearing and comparing with various ground- truth staining, the scattering contrast of amyloid pathology, such as amyloid plaques, will be comprehensively examined across various AD mouse brain regions and human AD brain specimens. Moreover, we will develop a new data processing workflow to enable automated, large-scale neuroinformatic analysis and attempt to distinguish various Aβ aggregation types based on their intrinsic signatures.
