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Longitudinal In Vivo Imaging of the Cerebrovasculature: Relevance to CNS Diseases
Published on: December 6, 2016
Vascular Microbleeds Without Brain Atrophy: A Microvascular Signature of Mid-Stage 5xFAD Pathology
Xiuli Yang1, Yuguo Li1,2, Adnan Bibic2
1Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Abstract:
Cerebral microbleeds are increasingly recognized as a downstream manifestation of vascular injury in Alzheimer's disease (AD), arising secondary to cerebral amyloid angiopathy (CAA). Here, we examined the pathological specificity of microbleeds by comparing an amyloidosis mouse model (5xFAD) with a small-vessel disease (SVD) model characterized by vascular smooth-muscle cell loss. In vivo multimodal MRI, including gradient-echo, spin-echo, and diffusion-weighted imaging, was complemented by ex vivo high-resolution anatomical scans for validation. Both in vivo and ex vivo gradient-echo MRI consistently revealed hippocampal microbleeds in the 5xFAD model without macroscopic atrophy or ventricular enlargement, whereas no microbleeds or blood-brain barrier disruption were detected in the SVD model. Diffusion-weighted MRI further showed region-specific alterations in apparent diffusion coefficient within the midbrain of 5xFAD mice, but not in other regions or in the SVD cohort. These findings indicate that microbleeds are a pathology-specific marker of amyloid-related vascular injury. The imaging evidence underscores the potential of microbleeds as a disease-specific biomarker for detecting amyloid-driven vascular fragility and refining diagnostic and therapeutic strategies for AD.
Insights
Cerebral microbleeds specifically indicate vascular injury from amyloid in Alzheimer's disease (AD). This finding highlights microbleeds as a key biomarker for diagnosing AD-related vascular fragility.
Area of Science:
- Neurology
- Neuroimaging
- Vascular Biology
Background:
- Cerebral microbleeds are linked to vascular injury in Alzheimer's disease (AD).
- Cerebral amyloid angiopathy (CAA) is a primary cause of microbleeds in AD.
- Distinguishing microbleed causes is crucial for AD diagnosis and treatment.
Purpose of the Study:
- To determine if microbleeds are specific to amyloid-related vascular injury.
- To compare microbleed pathology in an AD mouse model (5xFAD) versus a small-vessel disease (SVD) model.
- To validate imaging findings with ex vivo scans.
Main Methods:
- Utilized multimodal MRI (gradient-echo, spin-echo, diffusion-weighted imaging) in vivo.
- Employed high-resolution ex vivo anatomical scans for validation.
- Compared the 5xFAD amyloidosis model with an SVD model featuring smooth-muscle cell loss.
Main Results:
- Gradient-echo MRI detected hippocampal microbleeds in 5xFAD mice, absent in the SVD model.
- No blood-brain barrier disruption was observed in the SVD cohort.
- Diffusion-weighted MRI revealed region-specific changes in the midbrain of 5xFAD mice.
Conclusions:
- Microbleeds are a pathology-specific marker of amyloid-related vascular injury.
- Imaging evidence supports microbleeds as a biomarker for amyloid-driven vascular fragility in AD.
- Microbleeds can refine diagnostic and therapeutic strategies for Alzheimer's disease.
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