Combination therapy prevents amyloid-dependent and -independent structural changes

Area of Science:

• Neuroscience
• Immunology
• Genetics

Background:

• Transgenic mouse models of Alzheimer's disease (AD) often exhibit ectopic transgene overexpression, complicating the study of disease pathogenesis.
• The APP/PS-1 double knock-in (DKI) mouse model offers a more physiologically relevant system for studying AD by producing mutant amyloid precursor protein (APP) and presenilin-1 (PS-1) at normal levels.

Purpose of the Study:

• To investigate the effects of amyloid-beta (Aβ) on brain structure and neuroplasticity in the APP/PS-1 DKI mouse model.
• To evaluate the efficacy of Aβ vaccination in preventing amyloid deposition and associated neuropathological changes.
• To assess the impact of combining Aβ vaccination with voluntary exercise on neurogenesis and brain repair.

Main Methods:

• APP/PS-1 DKI mice were vaccinated with amyloid-beta starting at 8 months of age.
• Cerebral amyloid deposition and microglial activation were assessed at 14 months.
• Neuropil integrity, including axons, dendrites, and synapses, was examined.
• Hippocampal neural progenitor and neuroblast populations were quantified.
• The effects of voluntary exercise, when combined with Aβ vaccination, were evaluated.

Main Results:

• Aβ vaccination effectively blocked cerebral amyloid deposition and reduced microglial activation.
• Neuropil abnormalities, including axonal and dendritic damage, were localized to amyloid plaques and resolved upon amyloid blockade.
• Amyloid removal did not restore reduced hippocampal neural progenitor populations.
• Combining Aβ vaccination with voluntary exercise significantly stimulated hippocampal neurogenesis.

Conclusions:

• Amyloid deposition in the DKI mouse model leads to both amyloid-dependent and -independent structural brain changes.
• Amyloid-directed immunotherapy can restore neuropil integrity.
• Exercise synergizes with Aβ immunotherapy to promote greater restoration of brain structure and neuroplasticity than either intervention alone.