Background

Aged peripheral nerves fail to regenerate due to two compounding failures: (1) senescent Schwann cells secrete SASP that suppresses neurotrophic factors (GDNF, BDNF, NGF, NT-3), and (2) c-Jun — the master regulator of the repair Schwann cell phenotype — fails to upregulate (dropping ~50% vs. young by day 4 post-injury). Current approaches target only one of these failures.

Hypothesis

A two-phase sequential therapy — first a senolytic pulse (dasatinib + quercetin) to clear irreversibly senescent Schwann cells and eliminate SASP, followed by localized c-Jun activation via Schwann-cell-specific AAV (Mpz/P0 or Sox10 promoter) — will restore peripheral nerve regeneration in aged mouse models more effectively than either intervention alone.

Mechanism

Phase 1 (Day 0-3): D+Q pulse eliminates p16INK4a-high senescent Schwann cells, removing the SASP-driven inhibitory microenvironment. A washout period (3-5 days) allows necessary pro-regenerative inflammation and macrophage recruitment to proceed unimpeded.

Phase 2 (Day 7+): Local AAV-mediated c-Jun overexpression under a Schwann-cell-specific promoter drives remaining non-senescent cells into the repair phenotype, restoring Bands of Bünger formation, neurotrophic secretion, and myelin debris phagocytosis.

Supporting Evidence

• Pain et al. (EMBO Mol Med, 2023; PMID:37860842) demonstrated D+Q restores nerve regeneration in aged mice
• Wagstaff et al. (eLife, 2021; PMID:33475496) showed c-Jun overexpression rescues repair in aged/chronically denervated nerves
• No study has tested the sequential combination

Key Risks and Mitigations

• c-Jun oncogenesis: Mitigated by Schwann-cell-specific promoters (Mpz/P0) in AAV, avoiding systemic activation
• SASP removal dampens inflammation: Mitigated by washout period allowing acute inflammatory phase
• No small-molecule c-Jun activators exist: AAV-based local gene therapy provides spatial specificity

Testable Predictions

1. Sequential D+Q → AAV-c-Jun will produce greater axon counts at 4 weeks vs. either alone in aged mouse sciatic nerve crush
2. Schwann cell p16INK4a+ fraction will decrease >70% after D+Q phase
3. c-Jun+ repair Schwann cells will increase >3-fold after AAV phase

Critical Controls

• Senolytic-only vs. combination in young mice
• Delayed c-Jun activation without prior senolytics
• Immune profiling (M1/M2 macrophage ratio) at each phase transition

Limitations

• AAV delivery to peripheral nerves is clinically early-stage
• Aged nerve microvascular rarefaction may limit metabolic support
• Preclinical mouse model — human translation requires further validation

Verified via mini-cos MCP pipeline: verification 75/100, bulldust PASS, novelty 0.95/1.0, zero prior art found.