LncRNA XIST inhibits mitophagy and increases mitochondrial dysfunction by promoting BNIP3 promoter methylation to facilitate the progression of KBD

The primary mechanisms underlying cartilage destruction in Kashin-Beck disease (KBD) involve excessive chondrocyte death and extracellular matrix (ECM) degradation. While long non-coding RNA XIST (lncRNA XIST) has been implicated in promoting chondrocyte injury in osteoarthritis (OA), its role in KBD-related chondrocyte injury remains poorly understood. In this study, joint tissues were collected from four healthy and four KBD-affected children, as well as five healthy and five KBD-affected adults, to assess the expression of lncRNA XIST. The results revealed a significant upregulation of lncRNA XIST in the cartilage tissues of KBD patients. To model KBD-induced chondrocyte damage in vitro, hypertrophic ATDC5 cells were exposed to 10 ng/ml T-2 toxin for 24 hours, which resulted in increased lncRNA XIST expression. Silencing lncRNA XIST was found to mitigate T-2 toxin-induced ECM degradation and chondrocyte apoptosis by alleviating defects in mitochondrial autophagy and dysfunction. Mechanistically, lncRNA XIST promoted the methylation of the BNIP3 promoter by recruiting DNA methyltransferases (DNMTs) to the BNIP3 promoter region, thereby suppressing BNIP3-mediated mitophagy and exacerbating mitochondrial dysfunction. To establish a KBD rat model, rats were fed a low-selenium diet supplemented with T-2 toxin for four weeks. Knockdown of lncRNA XIST in these rats attenuated articular cartilage damage and apoptosis, while enhancing collagen II expression. In conclusion, lncRNA XIST accelerates KBD progression by inhibiting mitophagy and promoting mitochondrial dysfunction through increased BNIP3 promoter methylation.