Multi‐Technique Integration Identifies O‐GlcNAc Transferase in Fibroblast‐Like Synoviocytes as a Therapeutic Target for Rheumatoid Arthritis

Rheumatoid arthritis (RA) progression is driven by the pathogenic transformation of stromal fibroblast‐like synoviocytes (FLSs). Using artificial intelligence‐guided analysis of a synovial single‐cell transcriptomic dataset, we identify O‐GlcNAc transferase (OGT) as a key regulator enriched in RA‐FLSs. Gain‐ and loss‐of‐function studies demonstrate that OGT is necessary to drive aggressive FLS phenotypes and exacerbate experimental arthritis. Mechanistically, OGT‐mediated O‐GlcNAcylation stabilizes SAP130, promoting histone deacetylation at the BTG2 promoter. This facilitates the deposition of repressive histone methylation marks, leading to BTG2 epigenetic silencing and ultimately fueling FLS aggression. To translate this mechanistic insight, we develop an FLS‐targeted proteolysis‐targeting chimera (PROTAC) by conjugating the OGT inhibitor OSMI‐1 to the AS1411 aptamer, which selectively binds surface nucleolin (NCL) overexpressed on pathogenic FLSs and, upon internalization, employs NCL as a molecular bridge to recruit the E3 ligase MDM2 for cell‐selective OGT degradation. This PROTAC suppresses FLS pathogenicity, attenuates arthritis in mice, and demonstrates additive therapeutic benefit when combined with the TNF‐α inhibitor etanercept. Collectively, our work establishes a translational paradigm that progresses from AI‐driven target discovery and mechanistic elucidation to the rational design of a cell‐type‐specific degradation therapy, offering a strategy to overcome the stromal‐driven therapeutic barrier in RA. AI‑guided single‑cell transcriptomics identifies OGT as a key regulator enriched in rheumatoid arthritis fibroblast‑like synoviocytes (RA‐FLSs). Inflammatory stimuli activate the OGT–SAP130 axis, which modulates the H3K27ac/H3K27me3 balance and epigenetically silences BTG2, promoting aggressive transformation of RA‑FLSs. A targeted PROTAC is developed to selectively degrade OGT in pathogenic FLSs, suppressing their aggressive phenotypes for RA therapy.