Mechanism by which NCOA4 promotes osteoarthritis progression through iron overload-induced mitochondrial dysfunction in chondrocytes

Background： Preventing and delaying the onset of osteoarthritis (OA) is more important than surgical treatment in its terminal stages.Current research indicates that nuclear receptor coactivator 4 (NCOA4) may accelerate the progression of osteoarthritis, but its underlying mechanisms remain unclear. Purpose: This study aims to investigate the role of NCOA4 in OA, providing novel therapeutic insights for the prevention and delay of OA progression. Methods: An OA rat model was established by injecting sodium iodate (SI). Behavioral assessment was first conducted via mechanical foot-withdrawal reflex threshold and gait analysis. Safranin O-fast green staining evaluated articular cartilage degeneration, while Western Blot (WB) detected extracellular matrix (ECM)-related proteins to analyze the effects of NCOA4 on the OA rat model. Subsequently, chondrocytes were established with NCOA4 knockdown and overexpression and grouped accordingly. CCK8, TUNEL, Western blot, and qPCR to analyze the effects of NCOA4 knockdown and overexpression on chondrocyte damage, iron overload, and mitochondrial dysfunction. Additionally, chondrocytes stimulated with IL-1β were used to screen for active compounds. The effects on mitochondrial function were validated by measuring Fe²⁺, ROS, mitochondrial membrane potential, ATP, and GPX4 levels. Results： This study employed animal models and in vitro cell experiments to conduct NCOA4 knockdown and overexpression experiments. Results revealed significantly elevated NCOA4 expression in both OA rat models and IL-1β-stimulated chondrocytes. Knocking down NCOA4 effectively reduced joint swelling and pain, improved gait, and mitigated cartilage histological damage and extracellular matrix degradation. At the cellular level, NCOA4 knockdown inhibited chondrocyte apoptosis, reduced intracellular Fe²⁺ levels and lipid ROS accumulation, upregulated GPX4 (a key ferroptosis inhibitor), and improved mitochondrial function (manifested as restored membrane potential, elevated ATP levels, and reduced Cyt C release). Crucially, application of ferroptosis inhibitors (Fer-1 or Lip-1) significantly reverses NCOA4 overexpression-induced decreases in chondrocyte activity, increased apoptosis, and mitochondrial dysfunction. Conclusion： NCOA4 levels increase in osteoarthritic chondrocytes. NCOA4 can cause mitochondrial dysfunction by inducing iron overload, thereby impairing chondrocyte type II collagen production, reducing extracellular matrix accumulation, and inducing apoptosis, which collectively promote OA progression. Knocking down NCOA4 can partially delay and alleviate OA symptoms, potentially serving as a future therapeutic target and providing new theoretical basis for clinical OA treatment.