Spontaneous hydrogen-releasing nanoenzyme alleviates osteoarthritis via oxidative stress reduction and mitochondrial dysfunction reversal.

Osteoarthritis (OA), a chronic and degenerative joint disease, has become increasingly prevalent due to the aging population, posing a significant societal burden. However, despite progress, effective therapeutic options for osteoarthritis remain limited. In OA, chronic inflammation mediates a hypoxic microenvironment, leading to increased cellular energy demands. Over time, this causes mitochondrial dysfunction, favoring the accumulation of ROS, thereby perpetuating inflammation. Furthermore, reduced autophagy in aging chondrocytes hinder the clearance of damaged mitochondria, exacerbating oxidative stress. Herein, we have developed a simple and environmentally friendly strategy to fabricate hydrogen-releasing nanozymes (Se-HMPB@AB@COS) that spontaneously release hydrogen gas, effectively treating osteoarthritis through antioxidant, anti-inflammatory, and mitochondrial dysfunction reversal mechanisms. During the process of hydrogen therapy, small hydrogen molecules can readily penetrate mitochondria, specifically reducing the levels of •OH thereby protecting mitochondrial function. Our research further unveils that hydrogen therapy can effectively enhance mitophagy and delay chondrocyte senescence. In vivo, Se-HMPB@AB@COS encapsulated with chondroitin sulfate significantly promotes the synthesis of collagen II, inhibits the degradation of extracellular matrix, and reduces inflammatory factors. Overall, this study innovatively synthesized a hydrogen-releasing nanozyme, demonstrating its effectiveness in inhibiting oxidative stress, inflammation, promoting mitophagy and extracellular matrix synthesis, thereby reducing cartilage and mitochondrial damage, and delaying OA progression.