Alzheimer's disease model

Alzheimer's Disease (AD) Model Construction

Alzheimer's disease is a neurodegenerative disease characterized by amyloid β (Aβ) deposition, tau protein pathology, and synaptic dysfunction. The following are the construction methods, evaluation indicators, and applicable scenarios of commonly used AD animal models.

I. Model Types and Core Methods

1. Transgenic Mouse Model

principle : Overexpression of human AD-related mutant genes (such as APP, PS1, tau) through gene editing to simulate Aβ deposition or neurofibrillary tangles (NFTs).

Common strains :

I. Aβ-induced model

principle : Acute Aβ toxicity is simulated by injecting Aβ oligomers or fragments into the brain.

Procedure :

Stereotaxic injection : After anesthesia, the hippocampus or cortex was located and Aβ1-42 oligomers were injected (mice: 2-5 μg/side; rats: 5-10 μg/side).

Time Node : Synaptic damage and cognitive impairment occur 7-14 days after injection.

Applicable scenarios : Short-term study of the mechanism of Aβ toxicity or the effect of drug intervention.

3. Drug-induced model

Scopolamine Model :

principle ：Scopolamine is a cholinergic antagonist that induces acute cognitive impairment.

method : Intraperitoneal injection of 1-2 mg/kg (mice) or 2-4 mg/kg (rats), behavioral testing was performed 30 minutes later.

Features ：It is simple to operate and suitable for cholinergic drug screening, but it has no AD pathological characteristics.

4. Natural Aging Model

SAM-P8 mice : Rapidly aging mice showed Aβ deposition and cognitive decline at 12 months of age.

Aged rats : 18-24 month old Sprague-Dawley rats, with Aβ accumulation and decreased synaptic plasticity.

5. Gene Editing Model (CRISPR/Cas9)​

Building a Strategy : Knock-in human AD-related mutations (such as APP Swedish mutation, PS1 M146V) or knock-out Aβ clearance genes (such as TREM2).

Advantages : More accurate simulation of hereditary AD (such as familial AD), and the pathological progression can be controlled.

II. Model Evaluation Indicators

1. Behavioral testing

Morris water maze : Assess spatial learning and memory abilities (escape latency, time spent in target quadrant).

Novel Object Recognition (NOR)​ : Test short-term memory (recognition index = new object exploration time/total exploration time).

Y-maze spontaneous alternation : Reflects working memory (alternation rate > 70% is normal).

Nesting behavior : Assess executive function (score 1-5, the lower the score, the more severe the cognitive impairment).

2. Pathological Analysis

Aβ deposition detection :

Immunohistochemistry/Immunofluorescence ：6E10 antibody labeled Aβ plaques, Thioflavin S stained senile plaques.

ELISA : Quantification of the ratio of Aβ1-40 to Aβ1-42 in brain homogenate (AD model Aβ42/Aβ40＞1).

Tau pathology detection :

AT8 Antibody : Labeling of phosphorylated tau (Ser202/Thr205).

Gallyas silver stain : Shows neurofibrillary tangles.

Synaptic markers ：Western blot detected the decreased expression of PSD95 and Synaptophysin.

3. Neuroinflammation Assessment

Microglial activation ：Morphology observed by Iba1 immunostaining (activated state: enlarged cell body and shortened processes).

Inflammatory factors : qPCR was used to detect the mRNA levels of IL-1β, TNF-α, and IL-6.

4. Brain imaging technology

Micro PET/MRI : In vivo detection of brain glucose metabolism (FDG-PET) or Aβ deposition (PiB-PET).

III. Comparison of Model Advantages and Disadvantages

IV. Application Scenarios

Drug Development :

Testing Aβ antibodies (such as Aducanumab), BACE1 inhibitors, or tau aggregation inhibitors.

Evaluate the neuroprotective effects of natural products (e.g., curcumin, resveratrol).

Pathological mechanism research :

Aβ and tau synergistic toxicity mechanism.

The causal relationship between neuroinflammation and synapse loss.

Gene therapy :

AAV-mediated gene silencing (e.g. targeting APP or tau).

CRISPR/Cas9 repairs disease-causing mutations.

Behavioral interventions :

The improving effect of environmental enrichment on cognitive decline.

V. Notes

Model Validation :

The transgenic model needs to be verified by PCR and Western blot to verify gene expression and pathological phenotype.

The Aβ injection model requires confirmation of the accuracy of the injection site (postoperative MRI verification).

Behavioral interference :

Avoid circadian rhythm reversal or stress (such as frequent grasping) that may affect test results.

Elderly animals should be free of visual or motor impairments that may interfere with the water maze.

Code of Ethics :

Stereotaxic surgery requires strict anesthesia and postoperative analgesia (eg, ibuprofen).

Animals with severe cognitive impairment (e.g., inability to forage for food) should be euthanized promptly.

VI. Sample Data