Coordinated mitochondrial quality control underlies oxidative stress resilience in MUSE stem cells

BACKGROUND: Reactive oxygen species (ROS) regulate stem-cell function, but sustained exposure causes oxidative damage, mitochondrial dysfunction and exhaustion. Multilineage-differentiating Stress-Enduring (MUSE) cells, a rare SSEA-3⁺ MSC subset, tolerate ROS-rich environments, although the mechanisms remain unclear. METHODS: We compared MUSE, Non-MUSE (SSEA-3⁻) and MSCs after H₂O₂ exposure, assessing ROS clearance, mtDNA integrity, 8-oxo-dG, antioxidant and BER responses, mitochondrial morphology/function, mitophagy and biogenesis, with focus on the PGC-1α/NRF2 axis. Three independent biological replicates were analyzed by imaging, qPCR, flow cytometry and biochemical assays. RESULTS: MUSE cells showed greater resistance to oxidative stress than MSCs and Non-MUSE cells. After H₂O₂, they displayed lower ROS accumulation (~15-25%), preserved mtDNA integrity, reduced 8-oxo-dG, rapid induction of antioxidant and BER-related genes, and maintenance of mitochondrial morphology, membrane potential and respiratory activity. MUSE cells also showed enhanced mitophagy, with >2-fold increased LAMP1-MitoTracker colocalization and induction of PINK1/phospho-Ub-S65, together with increased biogenesis, including ~45% higher COX-I/SDHA ratio, TFAM induction and PGC-1α activation at 48 h. CONCLUSION: MUSE cells coordinate antioxidant defense, DNA repair, mitophagy and biogenesis through a remove-and-replace program that preserves mitochondrial function during oxidative stress.