Brain capillaries in Alzheimer's disease

Area of Science:

• Neuropathology
• Neuroscience
• Vascular Biology

Background:

• Alzheimer's disease (AD) is a leading cause of irreversible dementia, characterized by specific neuropathological hallmarks.
• Key features include tau pathology (neurofibrillary tangles) and amyloid-beta (Aβ) peptide deposits (neuritic plaques).
• Neurodegeneration in AD involves synaptic loss, dendritic alterations, and organelle dysfunction, exacerbated by oxidative stress and amyloid toxicity.

Purpose of the Study:

• To investigate the role of vascular factors, specifically brain capillary alterations and blood-brain barrier (BBB) disruption, in Alzheimer's disease pathogenesis.
• To explore the morphological changes in brain capillaries and their implications for neuronal function and AD progression.
• To assess the potential of targeting vascular pathology as a therapeutic approach for Alzheimer's disease.

Main Methods:

• Morphological analysis of brain capillaries using silver impregnation techniques and electron microscopy (EM) in AD patients compared to age-matched controls.
• Evaluation of capillary tortuosity, branch point density, basement membrane thickness, tight junction integrity, and mitochondrial morphology.
• Assessment of endothelial cell pinocytotic vesicles and pericyte degeneration.

Main Results:

• AD brains exhibit significant alterations in brain capillaries, including increased tortuosity, reduced branch point density, and thickened basement membranes.
• Electron microscopy revealed reduced tight junction length and number, and altered mitochondrial morphology in endothelial cells and pericytes.
• Increased pinocytotic vesicles in endothelial cells suggest impaired transport function and BBB disruption, potentially releasing neurotoxic factors and disrupting Aβ homeostasis.

Conclusions:

• Structural and functional damage to brain capillaries and the BBB is a significant component of Alzheimer's disease pathology.
• These vascular impairments contribute to neuroinflammation, neurotoxicity, and autonomic dysfunction, exacerbating AD progression.
• Protecting brain capillaries and maintaining BBB integrity early in the disease may represent a promising therapeutic strategy for Alzheimer's disease.