Epigenetic brain reprogramming rejuvenates neuro-immune circuits to reverse Alzheimer's disease pathology and systemic bone loss.

Alzheimer's disease (AD) is characterized by progressive neurodegeneration, neuroinflammation, and systemic comorbidities, yet disease-modifying therapies remain elusive. Here, we show that partial epigenetic reprogramming via brain-restricted expression of Oct4, Sox2, and Klf4 (OSK) restores neuronal and neuroimmune homeostasis without loss of cellular identity. In APP/PS1 mice, OSK reprogramming improves cognitive performance across disease stages, reduces amyloid-β deposition, attenuates microglial activation, preserves synaptic integrity, and limits neuronal apoptosis. Mechanistically, reduced representation bisulfite sequencing reveals widespread reversal of AD-associated DNA methylation patterns, which is dependent on Tet2-mediated demethylation, establishing epigenetic rejuvenation as a key driver of functional recovery. Unexpectedly, brain-restricted OSK reprogramming also ameliorates systemic bone loss by reshaping brain-derived extracellular vesicle signaling, including modulation of miR-483-5p, thereby restoring osteogenic capacity. Together, these findings identify partial epigenetic reprogramming as a strategy to rewire neuro-immune circuits and link central nervous system rejuvenation to peripheral tissue homeostasis, providing a conceptual framework for targeting both neurodegeneration and its systemic consequences in AD.