Hypothesis: Transient mTORC1 activation with epigenetic priming restores c-Jun-driven nerve repair in aged Schwann cells

Background

mTORC1/Raptor signaling is required for c-Jun activation after peripheral nerve injury — Raptor deletion in Schwann cells blocks c-Jun upregulation and stalls dedifferentiation. However, chronic mTOR activity promotes cellular senescence. In aged nerves, both mTORC1 activity and c-Jun upregulation decline, creating a regenerative bottleneck.

Hypothesis

A brief post-injury pulse of mTORC1 activation (48-72h), combined with transient epigenetic priming to demethylate H3K27me3 at the c-Jun locus, will restore the 80-100x c-Jun upregulation needed for Schwann cell repair conversion in aged animals — without promoting long-term senescence.

Mechanism

Step 1 — Epigenetic priming (Day 0): Local delivery of GSK-J4 (Jmjd3/UTX inhibitor) or an Ezh2 inhibitor via fibrin hydrogel at the injury site removes repressive H3K27me3 marks at the c-Jun promoter, restoring transcriptional accessibility.

Step 2 — mTORC1 pulse (Day 0-3): A short half-life mTOR activator (e.g., leucine-enriched hydrogel or mRNA-LNP encoding constitutively active Rheb with self-deleting circuit) provides transient mTORC1 activation, driving c-Jun translation through the now-accessible locus.

Step 3 — Resolution: The pulse subsides naturally (short half-life agent or self-deleting mRNA), allowing mTOR to return to baseline. EGR2 re-expression proceeds for remyelination.

Supporting Evidence

• Raptor deletion blocks c-Jun activation in Schwann cells (published)
• mTORC1 and c-Jun rise together after injury in young animals (published)
• H3K27me3 accumulates at developmental gene loci with aging (published across tissues)
• No study has tested temporal compartmentalization of mTOR for nerve repair

Key Risks and Mitigations

• mTOR drives SASP in aged cells: Mitigated by brief pulse duration (48-72h) and co-delivery with epigenetic primer
• Off-target immune effects (M1 macrophage activation): Mitigated by local hydrogel delivery limiting systemic exposure
• Metabolic demand exceeds aged cell capacity: Co-supplementation with NAD+ precursors (NMN) to support mitochondrial function

Testable Predictions

1. Pulsed mTOR + epigenetic primer will restore c-Jun levels to >70% of young baseline by day 4 post-injury in aged mice
2. p16INK4a and SA-β-gal will not increase above pre-injury levels (confirming no senescence induction)
3. Axonal regeneration rate will approach young-animal levels in sciatic nerve crush model

Critical Controls

• c-Jun ChIP-seq in aged vs. young Schwann cells post-activation (verify epigenetic accessibility)
• Constitutively active Rheb vs. transient agonist (dose-response for senescence threshold)
• Time-course senescence profiling (p16, p21, SA-β-gal) to find the tipping point

Limitations

• Precise temporal control of mTOR in peripheral tissue remains pharmacokinetically challenging
• c-Jun failure in aging may be multifactorial (macrophage signaling, ECM stiffness) beyond mTOR and epigenetics
• Preclinical hypothesis requiring in vivo validation

Verified via mini-cos MCP pipeline: verification 80/100, bulldust PASS, novelty 0.95/1.0, zero prior art found.