TREM2 Agonist Therapy for Parkinson's Disease — Experimental Design

TREM2 Agonist Therapy for Parkinson's Disease

Experimental Rationale

This experiment tests the TREM2-Alpha-Synuclein Clearance Hypothesis by evaluating whether TREM2 agonism enhances [microglial](/cell-types/microglia) phagocytosis of [alpha-synuclein](/proteins/alpha-synuclein) aggregates and protects [dopaminergic neurons](/cell-types/dopaminergic-neurons) in [Parkinson's Disease](/diseases/parkinsons-disease) models.

Hypothesis Tested

Enhanced TREM2 signaling will:

Experimental Design

In Vitro Arm

Primary Microglia Culture

| Parameter | Specification |
|-----------|---------------|
| Source | Human iPSC-derived microglia or primary mouse microglia |
| Genotypes | TREM2 wild-type, TREM2 knockout, TREM2 R47H variant |
| Treatment | Alpha-synuclein preformed fibrils (PFF) ± TREM2 agonist |

Co-Culture System

• Format: Transwell coculture of microglia + dopaminergic neurons ( Lund human mesencephalic cells or iPSC-derived DA neurons)
• Treatment: TREM2 agonist at 0.1, 1, 10 µg/mL
• Duration: 14 days
• Controls: IgG isotype, vehicle, untremed PFF

Endpoint Analysis

TREM2 Agonist Therapy for Parkinson's Disease

Experimental Rationale

This experiment tests the TREM2-Alpha-Synuclein Clearance Hypothesis by evaluating whether TREM2 agonism enhances [microglial](/cell-types/microglia) phagocytosis of [alpha-synuclein](/proteins/alpha-synuclein) aggregates and protects [dopaminergic neurons](/cell-types/dopaminergic-neurons) in [Parkinson's Disease](/diseases/parkinsons-disease) models.

Hypothesis Tested

Enhanced TREM2 signaling will:

Experimental Design

In Vitro Arm

Primary Microglia Culture

| Parameter | Specification |
|-----------|---------------|
| Source | Human iPSC-derived microglia or primary mouse microglia |
| Genotypes | TREM2 wild-type, TREM2 knockout, TREM2 R47H variant |
| Treatment | Alpha-synuclein preformed fibrils (PFF) ± TREM2 agonist |

Co-Culture System

• Format: Transwell coculture of microglia + dopaminergic neurons ( Lund human mesencephalic cells or iPSC-derived DA neurons)
• Treatment: TREM2 agonist at 0.1, 1, 10 µg/mL
• Duration: 14 days
• Controls: IgG isotype, vehicle, untremed PFF

Endpoint Analysis

| Endpoint | Method | Readout |
|----------|--------|---------|
| Alpha-synuclein uptake | pSER129 immunostaining, flow cytometry | Phagocytic index |
| Phagocytic capacity | pHrodo-labeled alpha-synuclein | Fluorescence intensity |
| Neuronal survival | TH+ neuron counting, MAP2 | % survival vs. control |
| Neuroinflammation | IL-1β, TNF-α ELISA | Inflammatory cytokines |
| TREM2 expression | qPCR, Western blot | mRNA/protein levels |

In Vivo Arm

Animal Model

| Parameter | Specification |
|-----------|---------------|
| Species | C57BL/6J mice |
| Model | Alpha-synuclein preformed fibril (PFF) model |
| Age | 10-12 weeks at study start |
| Sex | Both males and females |

Treatment Groups

| Group | n | Treatment |
|-------|---|------------|
| 1 | 12 | Vehicle (PBS) |
| 2 | 12 | TREM2 agonist (5 mg/kg) |
| 3 | 12 | TREM2 agonist (10 mg/kg) |
| 4 | 12 | IgG isotype control |
| 5 | 12 | Alpha-synuclein PFF + TREM2 agonist |
| 6 | 12 | Alpha-synuclein PFF + vehicle |

Dosing Protocol

• Route: Intraperitoneal injection
• Frequency: Twice weekly
• Duration: 12 weeks
• Timing: Started 2 weeks post-PFF injection (established pathology)

Behavioral Assessment

| Test | Timepoint | Readout |
|------|-----------|---------|
| Rotarod | Baseline, Wk 6, Wk 12 | Latency to fall (seconds) |
| Cylinder test | Baseline, Wk 6, Wk 12 | Forelimb use asymmetry |
| Gait analysis | Wk 12 | Stride length, swing speed |
| Open field | Wk 12 | Total distance, time in center |

Tissue Collection and Analysis

Terminal endpoint: Week 12

| Tissue | Analysis |
|--------|----------|
| Substantia nigra | TH+ neuron counting (stereology) |
| Striatum | Dopamine content (HPLC), TH fiber density |
| Motor cortex | pSER129+ aggregates (IHC) |
| Midbrain | Microglial TREM2 expression (ISH) |
| CSF | sTREM2 levels (ELISA) |

Biomarker Analysis

| Biomarker | Sample | Method | Purpose |
|----------|--------|--------|---------|
| sTREM2 | CSF, serum | ELISA | Target engagement |
| NF-L | Serum | Simoa | Neurodegeneration marker |
| Alpha-synuclein RT-QuIC | CSF | Seed amplification | Pathology burden |
| IL-1β, TNF-α | CSF, tissue | ELISA | Neuroinflammation |

Statistical Analysis

Power Calculation

• Alpha: 0.05
• Power: 0.80
• Expected effect size: 30% improvement in motor function
• Calculated n: 10-12 per group

Primary Endpoints

Secondary Endpoints

• Biomarker correlation (Pearson correlation)
• Neuroinflammation scores (Kruskal-Wallis)
• Survival analysis (log-rank test)

Expected Outcomes

Positive Results

• TREM2 agonist improves motor performance in PFF model
• Reduced pSER129+ aggregates in substantia nigra
• Enhanced microglial phagocytosis in vitro
• sTREM2 elevation correlates with improved outcomes

Negative Results

• No motor improvement despite target engagement
• TREM2 agonist increases neuroinflammation
• Limited translation from in vitro to in vivo

Ethical Considerations

• All procedures approved by IACUC
• Minimize animal suffering
• Use of both sexes to identify sex-specific effects
• Endpoints designed to detect therapeutic benefit