Aβ seeds resist inactivation by formaldehyde

Area of Science:

• Neuroscience
• Biochemistry
• Pathology

Background:

• Cerebral beta-amyloidosis, a hallmark of Alzheimer's disease (AD), can be induced by injecting aggregated beta-amyloid (Aβ) into APP-transgenic mice.
• This induction process follows a prion-like seeding mechanism, where aggregated Aβ acts as the infectious agent.

Purpose of the Study:

• To investigate the stability and infectivity of Aβ seeds after formaldehyde fixation.
• To determine if strain-like conformational properties of Aβ aggregates are retained in fixed tissues.

Main Methods:

• Intracerebral injection of formaldehyde-fixed AD or aged APP-transgenic mouse brain extracts into young APP-transgenic mice.
• Amyloid conformation-sensitive luminescent conjugated oligothiophene dye spectral analysis.

Main Results:

• Formaldehyde fixation partially preserves the Aβ-inducing activity of brain extracts.
• Spectral analysis confirmed that strain-like properties of aggregated Aβ are maintained in fixed tissues.
• Aβ seeds demonstrate significant resistance to inactivation and structural alteration by formaldehyde.

Conclusions:

• Formaldehyde-fixed Aβ seeds retain their biological activity and structural characteristics.
• The remarkable durability of Aβ seeds may explain their persistence and spread in vivo.
• These findings enable the study of Aβ aggregate structure-disease relationships in archived formalin-fixed autopsy samples.