A non-toxic ligand for voxel-based MRI analysis of plaques in AD transgenic mice

Amyloid plaques are a characteristic feature in Alzheimer's disease (AD). A novel non-toxic contrast agent is presented, Gd-DTPA-K6Aβ1–30, which is homologous to Aβ, and allows plaque detection in vivo. μMRI was performed on AD model mice and controls prior to and following intracarotid injection with Gd-DTPA-K6Aβ1–30 in mannitol solution, to transiently open the blood–brain barrier. A gradient echo T2*-weighted sequence was used to provide 100μm isotropic resolution with imaging times of 115min. The scans were examined with voxel-based analysis (VBA) using statistical parametric mapping, for un-biased quantitative comparison of ligand-injected mice and controls. The results indicate that: (1) Gd-DTPA-K6Aβ1–30 is an effective, non-toxic, ligand for plaque detection when combined with VBA (p≤0.01–0.001), comparing pre and post-ligand injection scans. (2) Large plaques can be detected without the use of a contrast agent and this detection co-localizes with iron deposition. (3) Smaller, earlier plaques require contrast ligand for MRI visualization. Our ligand when combined with VBA may be useful for following therapeutic approaches targeting amyloid in transgenic mouse models.