Mesenchymal stromal cells (MSCs) are metabolically active and redox-sensitive therapeutic cells, with their therapeutic potency tightly linked to mitochondrial integrity and function. Beyond paracrine and immunomodulatory actions, MSCs can transfer functional mitochondria to damaged cells, restoring bioenergetics, maintaining redox homeostasis via ROS regulation, and facilitating tissue repair and regeneration. This review summarizes recent progress in MSC mitochondrial biology, highlighting how metabolic reprogramming, mitochondrial biogenesis, fusion-fission dynamics and mitophagy coordinately regulate MSC stemness, differentiation, senescence and therapeutic capacity. It outlines core redox regulatory networks covering mitochondrial ROS production (ETC Complexes I/III and reverse electron transport), non-mitochondrial oxidases (NADPH oxidases), and canonical antioxidant signaling (Nrf2/Keap1, thioredoxin/peroxiredoxin and glutathione/glutaredoxin). Redox-dependent post-translational modifications governing mitochondrial transfer machinery are emphasized, including cysteine oxidation of connexin 43, redox-regulated Drp1 phosphorylation, and oxidative modulation of Miro1-mediated mitochondrial trafficking. Major intercellular mitochondrial transfer routes, such as tunneling nanotubes, connexin 43-based intercellular communication and extracellular vesicles, are discussed under inflammatory, hypoxic and metabolic stress conditions. Preclinical studies across pulmonary, cardiovascular, neurological, renal, hepatic and immune-mediated diseases validate that MSC-derived mitochondrial transfer preserves ATP production, mitigates oxidative injury and remodels recipient cell immunometabolic phenotypes. Emerging engineering strategies to improve mitochondrial delivery and therapeutic outcomes are also reviewed, alongside translational bottlenecks including cell source heterogeneity, mitochondrial quality control, in vivo tracking, dosage optimization and long-term biosafety. Overall, MSC mitochondrial dynamics and intercellular transfer bridge redox biology, metabolism and regenerative medicine, offering mechanistic insights for next-generation precision regenerative therapies.
