Mapping of Microvascular Architecture in the Brain of an Alzheimer’s Disease Mouse Model using MRI
Abstract Purpose Growing evidence suggests that alterations of the cerebral microvasculature play a critical role in the pathogenesis of Alzheimer’s disease (AD). The objective of this study was to characterize and evaluate the cerebral microvascular architecture in the AD transgenic (Tg) mice model compared with non-Tg mice using brain microvascular indices obtained by MRI.Methods Seven non-Tg mice and ten 5xFAD Tg mice were scanned using a 7-T animal MRI system to measure the transverse relaxation rates of R2 and R2* before and after injection of the monocrystalline iron oxide nanoparticle contrast agent. After calculation of the relaxation rate difference of ΔR2* and ΔR2, the microvascular indices of the vessel size index (VSI), mean vessel diameter (mVD), mean vessel density (Q), mean vessel-weighted image (MvWI), and blood volume fraction (BVf) were mapped. The voxel-based analyses and regions-of-interest (ROIs)-based analyses were performed to compare the indices between the non-Tg and Tg groups.Results The BVf, mVD, VSI, and MvWI were greater in the Tg group than in the non-Tg group based on voxel comparisons. Additionally, the ROIs-based analysis showed that ΔR2*, BVf, mVD, MvWI, and VSI were increased in the Tg group compared to the non-Tg group in several brain regions. Most ROIs defined by the mouse brain atlas were not significantly different between the two groups.Conclusion We found increased microvascular indices of VSI and mVD in the Tg mice, reflecting microvascular disruption in the brain, which may be related to damages of the neurovascular unit in AD caused by cerebral amyloid angiopathy.Clinical Relevance / Application: To date, few studies have investigated the microvascular injuries of the AD brain using MRI. We suggest that investigation of cerebral microvasculature using a high-field MRI in AD would be worthwhile to elucidate the pathophysiology of cerebral amyloid angiopathy in this disease. Indeed, microvascular MRI can be a promising imaging tool for investigating early diagnosis and monitoring treatment in AD.