Elevated MMP-9/TIMP-1 ratio reflects net proteolytic activity against the BBB, causing degradation of tight junction proteins (claudin-5, occludin, ZO-1) and increased permeability. This imbalance precedes measurable cognitive decline and represents a blood-accessible biomarker. The hypothesis has the strongest evidence base with the additional advantage of having clinically plausible interventions available for repurposing (anti-MMP-9 antibodies such as anrukinzumab and GS-5745). Primary limitation is the lack of specificity for neurodegeneration versus systemic inflammation.
Curated pathway from expert analysis
flowchart TD A["Elevated MMP-9/TIMP-1 ratio"] B["Increased net proteolytic activity"] C["Degradation of tight junction proteins"] D["BBB tight junction proteolysis"] E["Increased BBB permeability"] F["Blood-accessible biomarker detection"] G["Early cognitive decline"] H["Anrukinzumab (anti-MMP-9 antibody)"] I["GS-5745 (anti-MMP-9 antibody)"] J["Inhibition of MMP-9 activity"] A -->|"causes"| B B -->|"targets"| C C -->|"cleaves"| D D -->|"results in"| E E -->|"enables"| F E -->|"precedes"| G H -->|"blocks"| J I -->|"blocks"| J J -->|"reduces"| A A -->|"elevated in"| F
No linked papers recorded for this hypothesis yet.
No curated PDB or AlphaFold mapping for MMP-9 yet. Search RCSB →
Median TPM across 13 brain regions for MMP-9 (Matrix Metallopeptidase 9) / TIMP-1 ratio from GTEx v10.
No clinical trials data linked to this hypothesis yet.
No curated ClinVar variants loaded for this hypothesis.
Run scripts/backfill_clinvar_variants.py to fetch P/LP/VUS variants.
No DepMap CRISPR Chronos data found for MMP-9 (Matrix Metallopeptidase 9).
Run python3 scripts/backfill_hypothesis_depmap.py to populate.
No resource usage or linked notebooks recorded for this hypothesis yet.
| Prediction | Predicted | Observed | Status | Conf |
|---|---|---|---|---|
| If MMP-9/TIMP-1 ratio specifically reflects brain-derived MMP-9 activity rather than systemic neutrophils, then ratio will correlate with CSF MMP-9 activity and with MRI measures of BBB leakage but no | Paired plasma/CSF samples (n≥80) show plasma MMP-9/TIMP-1 ratio correlates with CSF MMP-9 activity (r>0.55), with DCE-MRI Ktrans (r>0.45), but not with blood ne | — no observation — | pending | 0.71 |
| If MMP-9/TIMP-1 ratio in peripheral blood identifies early BBB tight junction degradation before clinical symptoms, then elevated MMP-9/TIMP-1 ratio will predict conversion from cognitively normal to | In CN subjects followed for 3 years (n≥150), those with baseline MMP-9/TIMP-1 ratio in top tertile show 3-4x higher MCI conversion rate, elevated CSF t-tau/p-ta | — no observation — | pending | 0.75 |