Nuclear binding SET domain 1 alleviates cartilage ferroptosis in knee osteoarthritis by upregulating the krüppel-like factor 9/autophagy-related 14 pathway via H3K36me2 modification.

Knee osteoarthritis (KOA) is a progressive disease featured by cartilage damage. This study attempts to explore the role of nuclear binding SET domain 1 (NSD1) in KOA cartilage ferroptosis, thereby finding a new target for KOA treatment. Pathological changes, cartilage damage, and inflammatory cytokine levels in the established KOA mouse model were assessed. Primary mouse knee chondrocytes were separated, cultured, and challenged with IL-1β to establish in vitro KOA models. Cell viability was determined, Reactive oxygen species levels and ferroptosis-related factors were measured after interventions with NSD1, krüppel-like factor 9 (KLF9), and acyl-CoA synthetase long-chain family member 4 (ATG14). Furthermore, the enrichment of NSD1 and H3K36me2 on the KLF9 promoter as well as the enrichment of KLF9 on the ATG14 promoter was analyzed. Binding site between KLF9 and ATG14 promoter was assessed. NSD1 was downregulated in KOA mouse cartilage tissues and IL-1β-challenged chondrocytes. KOA severity was alleviated, chondrocyte viability was promoted, and ferroptosis was quenched after NSD1 overexpression. NSD1 strengthened H3K36me2 to upregulate KLF9 expression, and KLF9 transcriptionally activated ATG14 expression. KLF9 or ATG14 knockdown could both partially reverse the protective role of NSD1 overexpression on KOA cartilage ferroptosis. NSD1 enhanced KLF9 expression to improve ATG14 expression via H3K36me2 modification, thus relieving KOA cartilage ferroptosis.