Amyloid structure exhibits polymorphism on multiple length scales in human brain tissue

Area of Science:

• Neuroscience
• Biochemistry
• Pathology

Background:

• Alzheimer's Disease (AD) is characterized by amyloid-beta (Aβ) plaque aggregation in the brain.
• The structural uniformity of these amyloid plaques across individuals and within the brain is largely unknown.
• Structural variations in amyloid fibrils could influence AD pathogenesis.

Purpose of the Study:

• To investigate the structural heterogeneity of amyloid plaques in human brain tissue.
• To map the abundance, orientation, and structural variations of amyloid fibrils.
• To determine if different clinical histories correlate with distinct amyloid structures.

Main Methods:

• Utilized X-ray microdiffraction on histological sections of human brain tissue.
• Analyzed the structural properties, abundance, and orientation of amyloid fibrils.
• Examined tissue from subjects with varying clinical histories.

Main Results:

• Identified distinct ensembles of fibrillar structures in tissues from subjects with different clinical histories.
• Observed coexistence of plaques with different amyloid structures within the same tissue section.
• Found a gradient of fibrillar structure from the core to the margins within individual plaques.

Conclusions:

• Amyloid plaque structure is not uniform, exhibiting significant polymorphism.
• Structural heterogeneity of amyloid fibrils may play a role in Alzheimer's Disease inception and progression.
• Findings challenge existing theories on AD pathogenesis by highlighting structural diversity.