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NeuroScience Associates

Approach to Selected Diseases: Alzheimer Disease (AD)

Overview

The hallmark pathological features of Alzheimer Disease (AD) in humans are amyloid plaques and neurofibrillary tangles. Over the past decade, an increasing number of genetically engineered mouse models for AD research have been developed to exhibit classic Alzheimer features. The timeline for development of disease features ranges from a few months to ~18 months. NSA has processed hundreds of human AD tissues and thousands of brains from AD mouse models.

Mouse Tissue:

NSA typically receives one hemisphere of each mouse brain for AD neurohistology while the other hemisphere is often held by the client for enzyme-linked immunosorbent assay (ELISA) analysis. NSA can process up to 40 mouse brain hemispheres coronally or 20 mouse brain hemispheres sagittally in each MultiBrain® Block (or 25 if the area of interest is the cerebrum). Alternatively, when both hemispheres are made available to NSA, 20 or 25 whole mouse brains can be processed sagittally in each block. The preference of the researcher determines which alignment is chosen.

Human Tissue:

With human tissue, NSA is capable of processing human brain and other large format sections, as in the image below, providing a unique opportunity to assess large contiguous cross-sections of tissue. More often however, NSA is asked to process multiple smaller samples from one or more brains using MultiBrain® Technology.

The standard NSA practice of encasing the brain tissue in gelatin provides a significant aid in the handling of tissue sections resulting in an improved final product.

Primary AD Endpoints: Amyloid Plaques and Neurofibrillary Tangles

The hallmark features of AD are amyloid plaques and neurofibrillary tangles. Amyloid-laden plaques exist as a diffuse form and as a more dense/mature form (congophilic). Amyloid is also found as deposits in vessels. Neurofibrillary tangles are present in cell bodies and in the neuropil as “neuropil threads.”

The choice of which stain(s) to use is based on the specific needs of the study. The Campbell-Switzer Alzheimer pathology stain, developed by NSA, is capable of showing all of the hallmark features of Alzheimer pathology, while other stains/antibody methods are capable of revealing more specific features. Please note that the Campbell-Switzer stain does not work on monkey tissue.

Strategic Approach to Amyloid Detection: Different approaches yield unique features

At specific times during an R&D cycle, different approaches to amyloid detection may be most useful. Each of the methods described has its own strengths and specialized advantage:

Campbell-Switzer Method: Dr. Bob Switzer and his former associate, Shannon Campbell, developed the Campbell-Switzer Alzheimer Pathology stain in the early 1980’s. Over the years, this unique stain has become a “work horse” tool for researchers, particularly in the earlier phases of R&D. Diffuse plaques are stained black and the more dense fibrillar amyloid forms are stained amber. Neurofibrillary tangles typically stain black.

Immunohistochemistry for Amyloid Plaque Detection: The antibody methods are intended to be very specific and reveal amyloid peptides that have been cleaved at a specific location. On the basis of a particular mouse model, treatment approach and other factors, a specific antibody can be more useful than others in revealing a specific measure of efficacy.

Some examples of antibody methods include:

Abeta Amyloid (plaques)Tau (neurofibrillary tangles)
Aß (1-40)AT8 (pSer202+Thr205)
Aß (1-42)Tau 46 (Epitope 404-441)
Aß (1-28)Anti-Human Tau HT7 (Epitope 158-163)
4G8Anti-Human Tau (Epitope 243-441)
6E10phospho Tau Thr181
phospho Tau S396
phospho Tau S422

Congo Red: Congo Red specifically reveals the more dense, fibrillar amyloid plaques (hence, congophilic plaques). When isolating these types of plaques as an endpoint, Congo Red is an effective solution, as is Thioflavin S.

Thioflavin S: As with Congo Red, Thioflavin S specifically reveals the more dense, fibrillar amyloid plaques (congophilic plaques), but with a fluorescent signal. This is a useful option if double fluorescent labeling is desired.

Alzheimer Endpoint: Inflammation

Inflammation occurs in conjunction with the hallmark pathologic features of AD and can be detected by examining microglia (Iba1 IHC) or astrocytes (GFAP IHC).

Alzheimer Mouse Model Plaque Chemoarchitecture

AD Endpoint: Disintegrative Debris

Images taken from sections of the brain of an old, >12 months, PS-1/APP mouse

AD Endpoint: Increase in Iron

Endpoints Overview and Table of Stains for AD

This table depicts the most commonly used stains for detecting various categories of markers used in Alzheimers research.

StainPrimary Pathology: Plaques and TanglesInflammationOther Feature-Specific Endpoints
Campbell-Switzer Method
6E10 IHC
Aß 1-40 IHC
Aß 1-42 IHC
Aß 1-43 IHC
Aß 1-28 IHC
Congo Red
Thioflavin S
AT8 IHC
H & E
CD 11b IHC
CD68 IHC
GFAP IHC
Iba1 IHC
Disintegrative Degeneration
Ferrin IHC
Perls-DAB
ChAT IHC
NeuN IHC
Tau pSer396
Tau pSer 422
Anti-Human Tau
Anti-Human Tau HT7
Tau 46
Tau pThr181

If you would like further information about how NSA can assist you with Alzheimers Disease research, please contact us or refer to our catalog.