Mitochondrial transplantation for osteoarthritis: from molecular mechanisms to clinical translation

Osteoarthritis (OA) is the most prevalent chronic degenerative joint disorder worldwide, characterized by progressive cartilage degradation, subchondral bone remodeling, synovial inflammation, and impaired mobility. Growing evidence has established mitochondrial dysfunction-including impaired oxidative phosphorylation (OXPHOS), excessive reactive oxygen species (ROS) generation, disrupted mitochondrial dynamics, and dysregulated mitophagy-as an early and pivotal driver of OA pathogenesis. These bioenergetic failures not only disrupt chondrocyte metabolism but also amplify inflammation, matrix degradation, and cell death. In recent years, mitochondrial transplantation has emerged as a revolutionary therapeutic paradigm, aiming to restore cellular homeostasis by delivering functional mitochondria into damaged chondrocytes. This review systematically summarizes the molecular mechanisms of mitochondrial dysfunction in OA and highlights three major therapeutic strategies: (1) cell-based approaches, particularly mesenchymal stem cell (MSC)-mediated mitochondrial transfer via tunneling nanotubes (TNTs) or extracellular vesicles (EVs); (2) cell-free approaches, utilizing purified mitochondria or MitoEVs for direct transplantation; and (3) engineered mitochondrial transplantation, integrating bioengineering, nanotechnology, and genetic modification to enhance mitochondrial quality, delivery efficiency, and therapeutic persistence. We further discuss opportunities and challenges in clinical translation, including standardization of mitochondrial preparation, optimization of delivery systems, immunological safety, and regulatory classification. Collectively, mitochondrial transplantation represents a disruptive strategy that directly addresses the bioenergetic collapse of chondrocytes and offers a promising avenue for disease-modifying therapy in OA. Future advances in mechanistic elucidation, technological optimization, and multicenter clinical trials will be crucial to transform "mitochondrial medicine" from experimental concept to clinical reality.