Background: Cellular senescence spreads through tissues via the SASP, but the mechanistic link between paracrine senescence signaling and stem cell functional decline remains incompletely characterized. Autophagy—a critical longevity pathway—declines with age in tissue-resident stem cells, yet the upstream triggers are poorly defined.

Hypothesis: Senescent cells release extracellular vesicles (EVs) enriched in miR-34a that are preferentially internalized by neighboring tissue-resident stem cells. miR-34a directly suppresses AMPK and TSC1, leading to constitutive mTORC1 activation and autophagy inhibition in recipient stem cells. This creates a feed-forward loop: autophagy-deficient stem cells accumulate damaged mitochondria, increase ROS, and themselves undergo premature senescence, generating self-amplifying aging niches that expand radially from initial senescent foci at a rate governed by EV diffusion kinetics.

Testable Predictions:

1. Conditioned media from senescent fibroblasts will reduce LC3-II/LC3-I ratio and increase p-S6K1 in mesenchymal stem cells; abolished by miR-34a antagomirs or EV depletion via ultracentrifugation
2. Single-cell spatial transcriptomics of aged murine tissues will reveal radial gradients of autophagy gene suppression centered on p16-INK4a-high senescent foci, with gradient slopes correlating with local EV concentration
3. Dasatinib-loaded nanoparticles targeted via beta-galactosidase-cleavable linkers will reduce tissue miR-34a-EV burden by >60% and restore stem cell autophagy flux within 4 weeks in aged mice
4. Horvath epigenetic clock measurements on stem cells adjacent to cleared senescent niches will show 2-4 year biological age reversal versus untreated controls at 8 weeks

Significance: This model unifies senescence, autophagy decline, and epigenetic aging through a single EV-mediated mechanism, proposing a targeted therapeutic strategy that avoids systemic senolytic toxicity. If validated, it shifts the geroscience paradigm from eliminating senescent cells to interrupting their paracrine aging signal propagation.