A Notch-mediated fibrogenic program drives treatment failure in rheumatoid arthritis

Brigham And Women'S Hospital, Boston MA

Investigators

Abstract

Project Summary/Abstract: A key unmet need in the treatment of rheumatoid arthritis (RA) is to understand the cellular mechanism underlying treatment failure. Recent studies have implicated joint fibroblast activation and fibrosis in treatment- resistance RA, yet the mechanism underlying synovial fibrogenesis in RA remains poorly understood. We now have data that indicates Notch signaling controls a fibrogenic program through regulation of transforming growth factor beta (TGF-β) signaling. Single-cell and spatial transcriptomic profiling of RA synovia revealed expansion of fibrogenic programs around Notch-activated stroma. The immediate goal of this project is to define the origin of synovial fibrogenesis and its impact on joint inflammation and treatment response in RA. The long-term goal of the project is to define targeting fibroblasts as a novel adjuvant therapy in RA. In pursuit of these findings, we propose 3 complementary aims to define the role of Notch-driven fibrogenesis in treatment failure in RA. Aim 1. Define a Notch-driven fibrogenic transcriptional program in synovial fibroblasts. This aim seeks to elucidate the molecular sequence of the fibrogenic program in synovial fibroblasts. Our goal is to demonstrate the molecular mechanism by which Notch signaling regulates TGF-β signaling in synovial fibroblasts. We will employ genetic perturbation via CRISPR/cas9 and transcriptomics to define the role of TGFB1 and TGFB3 in the Notch-mediated fibrogenic program. Next, we will apply high-resolution transcript mapping to define the spatial regulation of the fibrogenic program. Aim 2. Determine the consequence of a Notch-driven fibrogenic program on treatment outcomes. We hypothesize that a Notch-mediated fibrogenic program is associated with a poor treatment outcome in RA. We will apply spatial transcriptomics to pre- and post-treatment synovial biopsies to characterize baseline fibroblast phenotypes and evaluate for correlation between longitudinal shifts in fibroblast phenotypes and treatment response. We will validate our findings using an independent cohort of treatment- naive RA biopsies. We hypothesize fibrogenic fibroblasts predict treatment failure. Aim 3. Define the effect of Notch levels on inflammatory and fibrotic niche formation. The focus of this aim is to gain insights into how differing levels of Notch signaling lead to distinct stromal environments and their impact on inflammatory phenotypes in RA. We hypothesize a low stromal Notch level facilitates lymphocyte aggregation while a high stromal Notch level induces fibrinogenesis (Fig. 1). We will test this hypothesis by utilizing two synovial organoid systems we developed: 1) a cellular reconstitution, micromass- based organoids, and 2) RA patient-derived organoids.