Pathologically distinct fibroblast subsets drive inflammation and tissue damage in arthritis
Ontology highlight
ABSTRACT: The identification of lymphocyte subsets with non-overlapping effector functions has been pivotal to the development of targeted therapies in immune mediated inflammatory diseases (IMIDs). Yet, despite their key role in disease, it remains unclear whether fibroblast subclasses with non-overlapping functions also exist and are responsible for the wide variety of tissue driven pathologies observed in IMIDs such as inflammation and damage . Here we identify and describe the biology of distinct subsets of fibroblasts responsible for mediating either inflammation or tissue damage in arthritis. We show that deletion of FAPa+ synovial cells suppressed both inflammation and bone erosions in murine models of resolving and persistent arthritis. Single cell transcriptional analysis identified two distinct fibroblast subsets: FAPa+ THY1+ immune effector fibroblasts located in the synovial sub-lining, and FAPa+ THY1- destructive fibroblasts restricted to the synovial lining. When adoptively transferred into the joint, FAPa+ THY1- fibroblasts selectively mediate bone and cartilage damage with little effect on inflammation whereas transfer of FAPa+ THY1+ fibroblasts resulted in a more severe and persistent inflammatory arthritis, with minimal effect on bone and cartilage. Our findings describing anatomically discrete, functionally distinct fibroblast subsets with non-overlapping functions have important implications for cell based therapies aimed at modulating inflammation and tissue damage.
Project description:The identification of lymphocyte subsets with non-overlapping effector functions has been pivotal to the development of targeted therapies in immune mediated inflammatory diseases (IMIDs). Yet, despite their key role in disease, it remains unclear whether fibroblast subclasses with non-overlapping functions also exist and are responsible for the wide variety of tissue driven pathologies observed in IMIDs such as inflammation and damage . Here we identify and describe the biology of distinct subsets of fibroblasts responsible for mediating either inflammation or tissue damage in arthritis. We show that deletion of FAPa+ synovial cells suppressed both inflammation and bone erosions in murine models of resolving and persistent arthritis. Single cell transcriptional analysis identified two distinct fibroblast subsets: FAPa+ THY1+ immune effector fibroblasts located in the synovial sub-lining, and FAPa+ THY1- destructive fibroblasts restricted to the synovial lining. When adoptively transferred into the joint, FAPa+ THY1- fibroblasts selectively mediate bone and cartilage damage with little effect on inflammation whereas transfer of FAPa+ THY1+ fibroblasts resulted in a more severe and persistent inflammatory arthritis, with minimal effect on bone and cartilage. Our findings describing anatomically discrete, functionally distinct fibroblast subsets with non-overlapping functions have important implications for cell based therapies aimed at modulating inflammation and tissue damage.
Project description:<p>Droplet-based single-cell RNA-seq has emerged as a powerful technique for massively parallel cellular profiling. While these approaches offer the exciting promise to deconvolute cellular heterogeneity in diseased tissues, the lack of cost-effective, reliable, and user-friendly instrumentation has hindered widespread adoption of droplet microfluidic techniques. To address this, we have developed a microfluidic control instrument that can be easily assembled from 3D printed parts and commercially available components costing approximately $575. We adapted this instrument for massively parallel scRNA-seq and deployed it in a clinical environment to perform single-cell transcriptome profiling of disaggregated synovial tissue from 5 rheumatoid arthritis patients. We sequenced 20,387 single cells from synovectomies, revealing 13 transcriptomically distinct clusters. These encompass a comprehensive and unbiased characterization of the autoimmune infiltrate, including inflammatory T and NK subsets that contribute to disease biology. Additionally, we identified fibroblast subpopulations that are demarcated via THY1 (CD90) and CD55 expression. Further experiments confirm that these represent synovial fibroblasts residing within the synovial intimal lining and subintimal lining, respectively, each under the influence of differing microenvironments. We envision that this instrument will have broad utility in basic and clinical settings, enabling low-cost and routine application of microfluidic techniques, and in particular single-cell transcriptome profiling.</p> <p>Reprinted from [Stephenson et al., Nature Communications, 2018], with permission from the Nature Publishing Group.</p>
Project description:Inflammatory arthritis is associated with bone loss and fractures due to abnormal bone remodelling. Bone remodelling is 'uncoupled' with bone resorption increased and bone formation suppressed. These changes resemble those seen in patients treated with therapeutic glucocorticoids, and in both of these situations, altered wnt signalling is implicated. Recent studies have highlighted the importance of the synovial fibroblast in mediating abnormal bone remodelling during inflammation. The wnt antagonist dickkopf-1 (DKK1) is secreted by synovial fibroblasts in response to inflammation, and this protein has been proposed to be a master regulator of bone remodelling in inflammatory arthritis. Here we show that DKK1 expression by primary human synovial fibroblasts is more potently regulated by glucocorticoids than pro-inflammatory cytokines. Glucocorticoids, but not TNF-alpha, regulated expression of multiple wnt agonists and antagonists in favour of inhibition of wnt signalling. In vitro TNF-alpha and IL1-beta indirectly regulate DKK1 production through increased expression of the glucocorticoid activating enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). These results demonstrate that the links between synovial inflammation, altered wnt signalling and bone remodelling may not be direct but are dependent on local activation of endogenous glucocorticoids. Human fibroblast-like synoviocytes isolated from patients with rheumatoid arthritis treated with either vehicle, TNF or dexamethasone (dex). Gene arrays for control, TNF and dexamethasone treatments were performed on three separate synovial fibroblast cell lines isolated from three rheumatoid arthritis patients. All fold changes displayed are the combined results of the three separate fibroblast lines.
Project description:Synovial inflammation is associated with pain severity in patients with knee osteoarthritis (OA). The aim here was to determine in a population with knee OA, whether synovial tissue from areas associated with pain exhibited different synovial fibroblast subsets, compared to synovial tissue from sites not associated with pain. A further aim was to compare differences between early and end-stage disease synovial fibroblast subsets. Parapatellar synovitis was significantly associated with the pattern of patient-reported pain in knee OA patients. Synovial tissue from sites of patient-reported pain exhibited a differential transcriptomic phenotype, with distinct synovial fibroblast subsets in early OA and end-stage OA. Functional pathway analysis revealed that synovial tissue and fibroblast subsets from painful sites promoted fibrosis, inflammation and the growth and activity of neurons. The secretome of fibroblasts from early OA painful sites induced neurite outgrowth in dorsal root ganglion neurons. Sites of patient-reported pain in knee OA is associated with a different synovial tissue phenotype and distinct synovial fibroblast subsets. Further interrogation of these fibroblast pathotypes will increase our understanding of the role of synovitis in OA joint pain and provide a rationale for the therapeutic targeting of fibroblast subsets to alleviate pain in patients.
Project description:Synovial fibroblasts critically contribute to the pathogenesis of rheumatoid arthritis (RA) by acquiring either a pro-inflammatory or tissue-destructive phenotype. To explore the molecular mechanisms underlying the tissue-destructive fibroblast phenotype in arthritis, we performed bulk RNA-sequencing analysis on the synovial fibroblasts which were isolated from Col6a1-Cre-Ets1-flox/flox (Ets1ΔFib) and Ets1-flox/flox (Ets1flox) mice.
Project description:The role of synovial tissue fibroblasts and macrophages interactions in driving chronic inflammation and resolution of arthritis is unknown. In this project, we used bulk RNAseq to investigate the impact of different phenotypes of macrophages on activation of synovial fibroblasts.
Project description:The destruction of bone and cartilage results in a loss of joint functionality, critically impairing the quality of life in arthritis patients. Synovial fibroblasts (SFs) critically contribute to the pathogenesis of rheumatoid arthritis (RA) by acquiring either a pro-inflammatory or tissue-destructive phenotype. To explore the molecular mechanisms underlying the pathogenic fibroblast phenotype in arthritis, we performed single-cell RNA sequencing (scRNA-seq) on the synovial cells which were isolated from collagen-induced arthritis (CIA) mice.
Project description:Synovial fibroblasts in persistent inflammatory arthritis have been suggested to have parallels with cancer growth and wound healing, both of which involve a stereotypical serum response program. We tested the hypothesis that a serum response program can be used to classify diseased tissues, and investigated the serum response program in fibroblasts from multiple anatomical sites and two diseases. To test our hypothesis we utilized a bioinformatics approach to explore a publicly available microarray dataset including RA, OA and normal synovial tissue, then extended those findings in a new microarray dataset representing matched synovial, bone marrow and skin fibroblasts cultured from RA and OA patients undergoing arthroplasty. The classical fibroblast serum response program discretely classified RA, OA and normal synovial tissues. Analysis of low and high serum treated fibroblast microarray data revealed a hierarchy of control, with anatomical site the most powerful classifier followed by response to serum and then disease. In contrast to skin and bone marrow fibroblasts, exposure of synovial fibroblasts to serum led to convergence of RA and OA expression profiles. Pathway analysis revealed three inter-linked gene networks characterising OA synovial fibroblasts: Cell remodelling through insulin-like growth factors, differentiation and angiogenesis through ?3 integrin, and regulation of apoptosis through CD44. We have demonstrated that Fibroblast serum response signatures define disease at the tissue level, and that an OA specific, serum dependent repression of genes involved in cell adhesion, extracellular matrix remodelling and apoptosis is a critical discriminator between cultured OA and RA synovial fibroblasts. Fibroblasts were isolated from synovium, bone marrow and skin tissue samples taken at the time of knee or hip replacement surgery from 12 rheumatoid arthritis patients meeting the 1987 ACR criteria and 6 osteoarthritis patients diagnosed on the basis of characteristic x-ray findings and the absence of features suggestive of inflammatory arthritis. Only one hip sample was present in either disease group. Fibroblasts were maintained in fibroblast medium (consisting of 81.3% RPMI 1640, 10% FCS, 0.81x MEM non-essential amino acids, 0.81mM sodium orthopyruvate, 1.62mM glutamine, 810U/ml penicillin and 81?g/ml streptomycin) at 37°C in a humidified 5% CO2 atmosphere.