Spatial patterning of fibroblast TGFβ signaling underlies treatment resistance in rheumatoid arthritis

Treatment-refractory rheumatoid arthritis (RA) is a major unmet need, and the underlying mechanisms are poorly understood. To identify molecular determinants of refractory RA, we performed spatial transcriptomic profiling on synovial tissue biopsy samples taken 6 months before and after treatment. In the baseline biopsy samples of non-remitting patients, we identified increased fibrogenic signaling within vascular tissue niches, marked by high fibroblast COMP expression. We uncovered a role of endothelial-derived Notch signaling as an upstream regulator of fibroblast transforming growth factor beta (TGF beta) signaling via its opposing ability to induce TGF beta isoform expression while suppressing TGF beta receptors, generating a proximal-to-distal gradient of TGF beta sensitivity that can be altered with disruption of steady-state Notch signaling. In posttreatment biopsy samples, we observed significant immune depletion with expansion of fibrogenic niches, a process that can be reversed by inhibition of Notch and TGF beta signaling in RA patient-derived organoids. Collectively, our data implicate targeting of TGF beta signaling to prevent exuberant synovial tissue fibrosis as a potential therapeutic strategy for refractory RA.