Cysteine metabolism dysregulation promotes ferroptosis in osteoarthritis: Insights from multi-species bioinformatics and experimental validation.

Objective: Osteoarthritis (OA) was traditionally viewed as a mechanically driven disorder. However, emerging evidence implicated metabolic dysregulation in its pathogenesis. This study investigated the novel interaction among cysteine metabolism, ferroptosis, and OA progression, while evaluating the therapeutic efficacy of L-cysteine supplementation. Methods: Integrated transcriptomic analyses of murine (GSE112641), rat (GSE118559), and human (GSE114007) OA cartilage datasets identified conserved metabolic perturbations. Proteomic and metabolomic profiling of human OA cartilage validated pathway-level dysregulation. Mechanistic validation employed IL-1β-stimulated inflammatory chondrocytes under cysteine-depleted conditions, with parallel assessment of ferroptosis markers, including expression of GPX4, SLC7A11 and TFRC, glutathione metabolism, iron accumulation, and lipid peroxidation. Therapeutic potential was further tested in a surgery-induced OA murine model receiving L-cysteine administration. Results: Cross-species analysis revealed cysteine/glutathione metabolism as the most consistently dysregulated pathway in OA. Multi-omics profiling demonstrated dysregulation of cysteine/glutathione metabolism and ferroptosis in OA. Conclusion: This study establishes cysteine metabolism as a master regulator of ferroptosis in OA pathogenesis. The mechanistic chain from cysteine depletion to glutathione collapse, iron overload, and lipid peroxidation explains chondrocyte loss patterns observed clinically. L-cysteine supplementation emerges as a dual-action therapy, simultaneously addressing oxidative stress and ferroptosis. Translational potential: This study underscores the translational potential of L-cysteine supplementation as a novel therapy for OA. By targeting the dysregulated cysteine/glutathione metabolism and its role in ferroptosis, L-cysteine presents a dual-action approach to mitigate cartilage degeneration. Future clinical trials should evaluate its efficacy and safety in diverse patient populations, focusing on both clinical outcomes and metabolic markers. This research paves the way for a redefined management strategy for OA as a metabolically driven disorder.