Hypothesis

Age‑associated decline in enteric glial cell‑derived extracellular vesicles (EVs) that transport specific microRNAs (miR‑124‑3p, miR‑138‑5p, miR‑9‑5p) disrupts vagal afferent signaling, causing a measurable fragmentation of coordinated gut‑brain transcriptional modules. This EV‑mediated miRNA deficit predicts increased persistent H1 loops (disconnected co‑expression circuits) and decreased H0 connectivity in paired gut‑brain transcriptomic persistence diagrams, thereby linking mucosal glial dysfunction to inflammaging and cognitive decline.

Mechanistic Basis

The research context highlights that aging disrupts bidirectional gut‑brain signaling via LPS‑driven cytokine cascades and progressive enteric nervous system (ENS) neuronal loss, yet it does not address how glial‑derived EVs might preserve transcriptional coupling. Enteric glia secrete EVs enriched in neuronal‑protective miRNAs that cross the gut barrier, reach the portal circulation, and influence vagal afferent nuclei and downstream brain regions (e.g., nucleus tractus solitarius, prefrontal cortex). With age, enteric glial hypertrophy and reduced nNOS/ChAT signaling correlate with diminished EV release (observed in vitro models of glial senescence). Loss of these miRNAs in the brain leads to derepression of pro‑inflammatory transcripts (NFKBIA, CXCL10) and dampening of vagal‑associated genes (CHAT, SNAP25), creating a discordance between gut and brain co‑expression networks. Topological data analysis (TDA) of paired gut‑brain transcriptomes would capture this discordance as increased 1‑dimensional holes (H1) representing lost cyclic co‑ordination and reduced 0‑dimensional connectivity (H0) reflecting module disintegration.

Testable Predictions

1. EV miRNA Quantification – Isolate EVs from portal blood of young (3 mo) and aged (24 mo) mice; quantify miR‑124‑3p, miR‑138‑5p, miR‑9‑5p via qPCR. Prediction: aged mice show >50 % reduction vs. young.
2. Correlation with ENS Markers – Correlate EV miRNA levels with colonic nNOS and ChAT protein levels (immunofluorescence) in the same animals. Prediction: strong positive Pearson r (>0.7).
3. Topological Signature – Perform dual RNA‑seq on colonic ENS microdissections and prefrontal cortex from the same aged mice; construct joint gene‑co‑expression matrices and compute persistence diagrams. Prediction: aged samples exhibit significantly higher H1 persistence entropy and lower H0 Betti numbers than young (p<0.01, permutation test).
4. Rescue Experiment – administer purified young‑mouse enteric glial EVs (or synthetic miRNA‑loaded EVs) to aged mice via intraperitoneal injection weekly for 8 weeks. Prediction: restored EV miRNA normalizes portal cytokine levels (TNFα, IL‑6), improves vagal tone (heart‑rate variability), reduces H1 persistence entropy, and rescues performance in the Morris water maze.
5. Human Translation – In a cross‑sectional human cohort (n=120, ages 20‑80), measure circulating EV miR‑124‑3p in serum, colonic biopsy nNOS expression (via sigmoidoscopy), and CSF inflammatory markers. Prediction: multivariate model shows EV miRNA mediates 30‑40 % of the effect of age on CSF IL‑6 and on Mini‑Mental State Examination scores.

Potential Refutation

If EV miRNA levels do not differ with age, or if restoring EVs fails to alter topological metrics or inflammaging phenotypes, the hypothesis would be falsified. Similarly, if TDA shows no significant change in H1/H0 between young and old gut‑brain pairs despite evident microglial activation, the proposed link between glial EV loss and transcriptional topology would be unsupported.