Abstract
BACKGROUND: Heterotopic ossification (HO) pathogenesis involves ROS-driven stem cell differentiation. Carnosic acid (CA), a natural antioxidant, remains unexplored for HO. METHODS: In vitro, tendon-derived stem cells (TDSCs) were stimulated with IL-1β, and CA was used for intervention to assess its effects on differentiation and ROS production via real-time quantitative PCR (qPCR), western blotting (WB), and immunofluorescence. Additionally, a burn and Achilles tendon transection-induced mouse model of traumatic HO was established to evaluate the therapeutic potential of CA. RESULTS: In vitro, CA activated nuclear factor erythroid 2-related factor 2 (Nrf2) and inhibited nicotinamide adenine dinucleotide phosphate oxidase 1 (NOX1), leading to increased antioxidant enzyme activity and reduced intracellular ROS levels. CA also regulated the PTEN/AKT signaling pathway, suppressing osteogenic and chondrogenic differentiation of TDSCs. In vivo, micro-computed tomography (Micro-CT) and histological analyses demonstrated that CA activated Nrf2 and enhanced antioxidant enzyme expression, thereby inhibiting osteogenic and chondrogenic factor expression in Achilles tendon tissue and reducing HO formation. CONCLUSIONS: CA is a novel HO therapeutic by dual targeting of oxidative stress and differentiation pathways.