Hypothesis

Enhancing central nervous system plasticity via vagal efferent stimulation reverses age‑related decline in intestinal stem cell (ISC) function, Paneth cell antimicrobial output, and barrier integrity, thereby establishing the brain as an upstream regulator of gut longevity.

Rationale

Recent work shows that gut‑derived signals dominate brain aging phenotypes via afferent vagal pathways [1]. Conversely, descending vagal output from the nucleus tractus solitarius (NTS) to the enteric nervous system (ENS) can modulate motility, secretion, and epithelial renewal, yet no study has causally linked brain‑targeted interventions to downstream intestinal rejuvenation. Psilocybin‑induced cortical plasticity extends cellular lifespan in vitro [3] and reshapes microbiome composition [2], suggesting a bidirectional loop that remains untested at the mechanistic level.

We propose that sustained efferent vagal firing releases acetylcholine onto ENS cholinergic neurons, which in turn upregulates Wnt/β‑catenin signaling in intestinal crypts. This cascade promotes ISC proliferation, Paneth cell maturation, and mucin‑2 secretion, collectively tightening the epithelial barrier and reducing luminal endotoxin translocation.

Predictions

1. Aged mice receiving chronic, low‑frequency vagal nerve stimulation (VNS) will show increased ISC markers (Lgr5+, Ki67+) compared with sham‑stimulated controls.
2. VNS will elevate Paneth cell lysozyme secretion and reduce bacterial translocation to mesenteric lymph nodes.
3. Pharmacological blockade of vagal efferents (via subdiaphragmatic vagotomy or nicotinic antagonists) will abolish the VNS‑induced intestinal improvements.
4. Microbiota shifts secondary to VNS will correlate with restored barrier function but will not be necessary for the primary ISC rescue.

Experimental Design

• Subjects: 20‑month‑old C57BL/6J mice (n=10 per group).
• Groups: (1) Sham VNS, (2) Active VNS (0.5 Hz, 0.5 mA, 30 min/day for 4 weeks), (3) VNS + subdiaphragmatic vagotomy, (4) VNS + methyllycaconitine (α7‑nAChR antagonist).
• Readouts:
  • ISC quantification via immunohistochemistry for Lgr5 and Ki67 in isolated crypts.
  • Paneth cell function measured by lysozyme ELISA in intestinal lavage and crypt‑isolated granule counts.
  • Barrier integrity assessed by FITC‑dextran permeability assay and zonulin‑like protein levels.
  • Bacterial translocation quantified by 16S rRNA copy number in mesenteric lymph node DNA.
  • Microbiome profiling (16S sequencing) to evaluate secondary changes.
• Controls: Age‑matched young (3‑month) mice receiving sham VNS to establish baseline.

Potential Outcomes

• Support: VNS‑treated aged mice exhibit ISC and Paneth cell metrics indistinguishable from young controls, with reduced permeability and bacterial translocation; vagotomy or α7‑nAChR blockade prevents these effects.
• Refute: VNS fails to alter ISC or Paneth cell readouts despite confirmed efferent activation (measured by c‑Fos in dorsal motor nucleus of the vagus), indicating that central vagal tone alone is insufficient to drive intestinal rejuvenation.

Implications

If validated, this framework would reposition the CNS as a manipulable lever for gut‑centric longevity strategies, prompting combinatorial approaches that pair neuroplasticity‑enhancing compounds (e.g., psychedelics, exercise, cognitive training) with targeted vagal modulation. Conversely, a negative result would reinforce the prevailing bottom‑up view and redirect resources toward microbiota‑focused interventions.