DOT1L-mediated H3K79me3 of ITCH promotes AURKA ubiquitination to suppress ECM degradation in osteoarthritis.

Abstract

As a prevalent chronic joint disorder, osteoarthritis (OA) is characterized by degenerative changes, primarily driven by the pathological degradation of the chondrocyte extracellular matrix (ECM). Current therapies lack efficacy in halting ECM degradation, making elucidation of its regulatory mechanisms crucial for developing novel OA treatments. This study investigated the role of the DOT1L/ITCH/AURKA axis in ECM degradation during OA development. An in vitro OA model was established by treating rat chondrocytes with 10 ng/mL IL-1β for 24 h. TNF-α and IL-6 secretion was measured by ELISA. ECM content was assessed via alcian blue staining. RT-qPCR, western blot, and immunofluorescence staining analyzed associated molecule expression. Co-IP verified ITCH-AURKA interaction and AURKA ubiquitination. ChIP detected DOT1L and H3K79me3 enrichment at the ITCH promoter. An anterior cruciate ligament transection (ACL-T)-induced OA rat model with intra-articular injection of DOT1L-overexpressing lentivirus was further established, followed by HE staining, safranin O-fast green staining, and IHC analysis. IL-1β stimulation upregulated AURKA but downregulated DOT1L and ITCH expression in rat chondrocytes. ITCH promoted AURKA ubiquitination and degradation, thereby attenuating IL-1β-stimulated degradation of ECM in rat chondrocytes. DOT1L upregulated ITCH expression by mediating H3K79me3 modification at its promoter. DOT1L-dependent H3K79me3 enrichment at the ITCH promoter downregulated AURKA, ultimately inhibiting IL-1β-induced ECM degradation in rat chondrocytes. In vivo, DOT1L overexpression alleviated ACL-T-induced cartilage degeneration and reversed the ACL-T-induced downregulation of ITCH and upregulation of AURKA and ADAMTS5. Collectively, our findings identify the DOT1L/ITCH/AURKA axis as a key epigenetic and post-translational regulatory mechanism that protects against ECM degradation in OA.