Mitochondria serve as a source of mineral precursors initiating early cartilage calcification in osteoarthritis

Cartilage calcification actively contributes to osteoarthritis progression by generating mineral depositions that disrupt joint homeostasis and amplify matrix degradation. Previous studies found that chondrocyte-derived matrix vesicles provide the minerals orchestrating pathological cartilage calcification. However, the intracellular origin of minerals in osteoarthritic cartilage remains elusive, significantly impeding the development of targeted therapies. This study identified mitochondria as subcellular reservoirs of mineral precursors containing calcium and phosphorus. At the early stage of osteoarthritis, chondrocyte mitochondrial DNA (mtDNA) is transformed into an intertwined state that enables them to stabilize minerals into amorphous precursors. The stabilized amorphous mineral precursors are then transported via vesicles to the mineralization site. Targeting mtDNA distribution by modulating coiled-coil-helix, coiled-coil-helix-domain containing 6 (CHCHD6) can inhibit cartilage calcification and impair osteoarthritis progression. Our findings provide mechanistic insights into mitochondrial orchestration of incipient pathological cartilage calcification in osteoarthritis. Elucidating the mitochondrial-driven calcification cascade redefines therapeutic paradigms, enabling rational design of mineralization-inhibitory strategies for early management of osteoarthritis.