PRKN and Parkinson disease: Pu-Exos enhance mitophagy via the PINK1-Parkin pathway, restore mitochondrial respiratory chain complexes I and V, and increase ATP production in SH-SY5Y cells. In PD mice, Pu-Exos-PR (engineered exosomes with DSPE-PEG-RVG) improved motor coordination, reduced neuronal degeneration, and enhanced survival of dopaminergic neuron survival.