Seeab3: a novel method for volumetric analysis of amyloid plaques

One of the main neuropathological hallmarks of Alzheimer’s disease (AD) is the presence of plaques which consist of aggregated extracellular amyloid beta (Aβ) protein. Patients with early onset or familial AD (FAD) often harbor genetic mutations that bias processing towards this amyloidogenic outcome, accelerating disease onset and worsening disease severity. Elevated levels of Aβ peptides are thought to be a key component of the disease state; thus, characterizing the spatial and temporal profile of amyloid plaque deposition may yield important insights into the mechanisms that cause and exacerbate AD pathology. Therefore, we have developed a new method which permits high throughput, detailed analysis of plaque deposition on entire intact brain regions. In order to more easily and precisely quantify amyloid plaque deposition, we have developed a new method which permits high throughput, detailed analysis on entire intact brain regions. This method relies on the use of the lipophilic dye BTA-1, which was developed as an in vivo biomarker to detect amyloid plaques with PET imaging, combined with an optical clearing method called SeeDB in which the refractive index of the sample is altered to minimize light scatter during imaging. As a result, amyloid plaques can be visualized throughout significanlty thicker sections of tissue (up to 1 mm), and because SeeDB does not cause sample swelling, z-stack images rendered in 3D yield much more accurate size, shape, and volume measurements. In addition, vascular architecture can be analyzed in the same sections by using a fluorescently conjugated (Dylight 594) form of Lycopersicon Esculentum (tomato lectin) which is injected iv prior to sacrifice. Our preliminary studies demonstrate that this approach provides high resolution detection of amyloid plaques as well as quantitative analysis of vascular networks in the 5xFAD mouse model of AD. We anticipate that the use of this method will afford a more complete and accurate characterization of amyloid plaque deposition throughout the progression of AD.