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Notch signalling drives synovial fibroblast identity and arthritis pathology.

ABSTRACT: The synovium is a mesenchymal tissue composed mainly of fibroblasts, with a lining and sublining that surround the joints. In rheumatoid arthritis the synovial tissue undergoes marked hyperplasia, becomes inflamed and invasive, and destroys the joint^1,2. It has recently been shown that a subset of fibroblasts in the sublining undergoes a major expansion in rheumatoid arthritis that is linked to disease activity^3-5; however, the molecular mechanism by which these fibroblasts differentiate and expand is unknown. Here we identify a critical role for NOTCH3 signalling in the differentiation of perivascular and sublining fibroblasts that express CD90 (encoded by THY1). Using single-cell RNA sequencing and synovial tissue organoids, we found that NOTCH3 signalling drives both transcriptional and spatial gradients-emanating from vascular endothelial cells outwards-in fibroblasts. In active rheumatoid arthritis, NOTCH3 and Notch target genes are markedly upregulated in synovial fibroblasts. In mice, the genetic deletion of Notch3 or the blockade of NOTCH3 signalling attenuates inflammation and prevents joint damage in inflammatory arthritis. Our results indicate that synovial fibroblasts exhibit a positional identity that is regulated by endothelium-derived Notch signalling, and that this stromal crosstalk pathway underlies inflammation and pathology in inflammatory arthritis.

SUBMITTER: Wei K

PROVIDER: S-EPMC7841716 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Notch signalling drives synovial fibroblast identity and arthritis pathology.

Wei Kevin K Korsunsky Ilya I Marshall Jennifer L JL Gao Anqi A Watts Gerald F M GFM Major Triin T Croft Adam P AP Watts Jordan J Blazar Philip E PE Lange Jeffrey K JK Thornhill Thomas S TS Filer Andrew A Raza Karim K Donlin Laura T LT Siebel Christian W CW Buckley Christopher D CD Raychaudhuri Soumya S Brenner Michael B MB

Nature 20200422 7811

The synovium is a mesenchymal tissue composed mainly of fibroblasts, with a lining and sublining that surround the joints. In rheumatoid arthritis the synovial tissue undergoes marked hyperplasia, becomes inflamed and invasive, and destroys the joint<sup>1,2</sup>. It has recently been shown that a subset of fibroblasts in the sublining undergoes a major expansion in rheumatoid arthritis that is linked to disease activity<sup>3-5</sup>; however, the molecular mechanism by which these fibroblasts ...[more]

PMID: 32499639

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Project description:ObjectivesThe mammalian target of Rapamycin (mTOR) is a metabolic master regulator of both innate and adaptive immunity; however, its exact role in stromal cell biology is unknown. In this study we explored the role of the mTOR pathway on Rheumatoid Arthritis synovial fibroblast (RASF) metabolism and activation and determined if crosstalk with the Hippo-YAP pathway mediates their effects.MethodsPrimary RA synovial fibroblasts (RASF) were cultured with TNFα alone or in combination with the mTOR inhibitor Rapamycin or YAP inhibitor Verteporfin. Chemokine production, matrix metalloproteinase (MMP) production, and adhesion marker expression were quantified by real-time PCR, ELISA, and/or Flow Cytometry. Invasion assays were performed using Transwell invasion chambers, while wound repair assays were used to assess RASF migration. Cellular bioenergetics was assessed using the Seahorse XFe96 Analyzer. Key metabolic genes (GLUT-1, HK2, G6PD) were measured using real-time PCR. Reanalysis of RNA-Seq analysis was performed on RA (n = 151) and healthy control (HC) (n = 28) synovial tissue biopsies to detect differential gene and pathway expression. The expression of YAP was measured by Western Blot.ResultsTranscriptomic analysis of healthy donor and RA synovial tissue revealed dysregulated expression of several key components of the mTOR pathway in RA. Moreover, the expression of phospho-ribosomal protein S6 (pS6), the major downstream target of mTOR is specifically increased in RA synovial fibroblasts compared to healthy tissue. In the presence of TNFα, RASF display heightened phosphorylation of S6 and are responsive to mTOR inhibition via Rapamycin. Rapamycin effectively alters RASF cellular bioenergetics by inhibiting glycolysis and the expression of rate limiting glycolytic enzymes. Furthermore, we demonstrate a key role for mTOR signaling in uniquely mediating RASF migratory and invasive mechanisms, which are significantly abrogated in the presence of Rapamycin. Finally, we report a significant upregulation in several genes involved in the Hippo-YAP pathway in RA synovial tissue, which are predicted to converge with the mTOR pathway. We demonstrate crosstalk between the mTOR and YAP pathways in mediating RASF invasive mechanism whereby Rapamycin significantly abrogates YAP expression and YAP inhibition significantly inhibits RASF invasiveness.ConclusionmTOR drives pathogenic mechanisms in RASF an effect which is in part mediated via crosstalk with the Hippo-YAP pathway.

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Notch signalling drives synovial fibroblast identity and arthritis pathology.

Publications

Notch signalling drives synovial fibroblast identity and arthritis pathology.

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