Disruption of CTCF-mediated IGF2 repression promotes AKT-dependent mitochondrial oxidative stress and chondrocyte senescence in osteoarthritis.

AIMS: The upstream epigenetic mechanisms linking chronic inflammation to mitochondrial dysregulation and chondrocyte senescence in osteoarthritis (OA) remain incompletely defined. This study investigated whether inflammation-associated loss of CTCF occupancy at the IGF2-H19 intergenic region contributes to IGF2 upregulation, AKT-dependent mitochondrial oxidative stress, and chondrocyte senescence. MATERIALS AND METHODS: Integrative transcriptomic analysis of GSE114007 was performed using DESeq2, WGCNA, and protein-protein interaction network analysis. Key findings were examined in human OA cartilage and mechanistically investigated in cytokine-stimulated C28/I2 chondrocytes using chromatin immunoprecipitation, mitochondrial functional profiling, and senescence assays. Mechanistic studies combined CTCF gain- and loss-of-function approaches with pharmacological targeting of IGF2, AKT, and mitochondrial ROS. IGF2 neutralization was further evaluated in an ACLT murine model. KEY FINDINGS: IGF2 emerged as a transcriptomic hub gene associated with mitochondrial and senescence-related networks in OA. Inflammatory stimulation reduced CTCF expression and occupancy at the IGF2-H19 intergenic region, accompanied by increased IGF2 expression, AKT activation, mitochondrial respiratory activity, ROS production, matrix catabolism, and senescence-associated phenotypes. CTCF overexpression attenuated IGF2 upregulation and oxidative/senescence-associated phenotypes, whereas CTCF knockdown elicited complementary changes. Targeting IGF2, AKT, or mitochondrial ROS reduced oxidative stress and senescence-associated changes. In vivo, IGF2 neutralization attenuated cartilage degeneration, matrix catabolism, AKT activation, and senescence-associated alterations. SIGNIFICANCE: These findings support a functional regulatory framework linking CTCF-IGF2 dysregulation with AKT-dependent mitochondrial oxidative stress and chondrocyte senescence in OA, highlighting IGF2 signaling as a potential therapeutic target.