Distinct fibroblast subsets drive inflammation and damage in arthritis

Navigating the diverse immune landscapes of psoriatic arthritis

The goal of remission in psoriatic arthritis (PsA) has remained elusive despite the influx of a range of new therapies over the last 20 years. In contrast, therapeutic responses to agents that inhibit IL-23 or IL-17 have demonstrated impressive efficacy in psoriasis. In part, the divergent responses in these two disorders are likely related to the heterogeneity of tissue involvement in PsA and the interplay of multiple different cell populations and molecular pathways. In this narrative review, we will examine the plasticity of the immune response in PsA from the perspective of the Th17 cell and monocyte and discuss recent findings regarding the importance of CD8+ T resident cells in disease pathogenesis. We will then examine the effects of cytokines on epithelial cell and stromal populations and finally discuss new data regarding immune cell and tissue resident cell cross-talk in entheses and bone. Lastly, the potential therapeutic targets that have emerged from these investigations will be discussed.

A Trifunctional Theranostic Ligand Targeting Fibroblast Activation Protein-α (FAPα)

PURPOSE

Fibroblast activation protein-α (FAPα) is uniquely expressed in activated fibroblasts, including cancer-associated fibroblasts that populate tumor stroma and contribute to proliferation and immunosuppression. Radiolabeled FAPα inhibitors enable imaging of multiple human cancers, but time-dependent clearance from tumors currently limits their utility as FAPα-targeted radiotherapeutics. We sought to increase the area under the curve (AUC) by constructing a trifunctional ligand that binds FAPα with high affinity and also binds albumin and theranostic radiometals.

PROCEDURES

RPS-309 comprised a FAPα-targeting moiety, an albumin-binding group, and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA). Inhibition of recombinant human FAPα (rhFAPα) was determined by colorimetric assay. Affinity for human serum albumin (HSA) was determined by high-performance affinity chromatography. The tissue distribution of [⁶⁸Ga]Ga-RPS-309 in SW872 tumor xenograft-bearing mice was imaged by microPET/CT and quantified by biodistribution studies performed from 30 min to 3 h post injection (p.i.). The biodistribution of [¹⁷⁷Lu]Lu-RPS-309 was determined at 4, 24, and 96 h p.i.

RESULTS

RPS-309 inhibits rhFAPα with IC₅₀ = 7.3 ± 1.4 nM. [⁶⁸Ga]Ga-RPS-309 is taken up specifically by FAPα-expressing cells and binds HSA with K_d = 4.6 ± 0.1 μM. Uptake of the radiolabeled ligand in tumors was evident from 30 min p.i. (> 5 %ID/g) and was significantly reduced by co-injection of RPS-309. Specific skeletal uptake was also observed. Activity in tumors was constant through 4 h p.i., but cleared significantly by 24 h. The AUC in this period was 127 (%ID/g) × h.

CONCLUSIONS

RPS-309 is a high-affinity FAPα inhibitor with prolonged plasma residence. Introduction of the albumin-binding group did not compromise FAPα binding. Although initial tumor uptake was high and FAPα-specific, RPS-309 also progressively cleared from tumors. Nevertheless, RPS-309 incorporates multiple sites in which structural diversity can be introduced, and therefore serves as a platform for future structure-activity relationship studies.

Targeting synovial fibroblast proliferation in rheumatoid arthritis (TRAFIC): an open-label, dose-finding, phase 1b trial

Background

Current rheumatoid arthritis therapies target immune inflammation and are subject to ceiling effects. Seliciclib is an orally available cyclin-dependent kinase inhibitor that suppresses proliferation of synovial fibroblasts—cells not yet targeted in rheumatoid arthritis. Part 1 of this phase 1b/2a trial aimed to establish the maximum tolerated dose of seliciclib in patients with active rheumatoid arthritis despite ongoing treatment with TNF inhibitors, and to evaluate safety and pharmacokinetics.

Methods

Phase 1b of the TRAFIC study was a non-randomised, open-label, dose-finding trial done in rheumatology departments in five UK National Health Service hospitals. Eligible patients (aged ≥18 years) fulfilled the 1987 American College of Rheumatology (ACR) or the 2010 ACR–European League Against Rheumatism classification criteria for rheumatoid arthritis and had moderate to severe disease activity (a Disease Activity Score for 28 joints [DAS28] of ≥3·2) despite stable treatment with anti-TNF therapy for at least 3 months before enrolment. Participants were recruited sequentially to a maximum of seven cohorts of three participants each, designated to receive seliciclib 200 mg, 400 mg, 600 mg, 800 mg, or 1000 mg administered in 200 mg oral capsules. Sequential cohorts received doses determined by a restricted, one-stage Bayesian continual reassessment model, which determined the maximum tolerated dose (the primary outcome) based on a target dose-limiting toxicity rate of 35%. Seliciclib maximum concentration (C_max) and area under the plasma concentration time curve 0–6 h (AUC_0–6) were measured. This study is registered with ISRCTN, ISRCTN36667085.

Findings

Between Oct 8, 2015, and Aug 15, 2017, 37 patients were screened and 15 were enrolled to five cohorts and received seliciclib, after which the trial steering committee and the data monitoring committee determined that the maximum tolerated dose could be defined. In addition to a TNF inhibitor, ten (67%) enrolled patients were taking conventional synthetic disease modifying antirheumatic drugs. The maximum tolerated dose of seliciclib was 400 mg, with an estimated dose-limiting toxicity probability of 0·35 (90% posterior probability interval 0·18–0·52). Two serious adverse events occurred (one acute kidney injury in a patient receiving the 600 mg dose and one drug-induced liver injury in a patient receiving the 400 mg dose), both considered to be related to seliciclib and consistent with its known safety profile. 65 non-serious adverse events occurred during the trial, 50 of which were considered to be treatment related. Most treatment-related adverse events were mild; 20 of the treatment-related non-serious adverse events contributed to dose-limiting toxicities. There were no deaths. Average C_max and AUC_0–6 were two-times higher in participants developing dose-limiting toxicities.

Interpretation

The maximum tolerated dose of seliciclib has been defined for rheumatoid arthritis refractory to TNF blockade. No unexpected safety concerns were identified to preclude ongoing clinical evaluation in a formal efficacy trial.

Funding

UK Medical Research Council, Cyclacel, Research into Inflammatory Arthritis Centre (Versus Arthritis), and the National Institute of Health Research Newcastle and Birmingham Biomedical Research Centres and Clinical Research Facilities.

Insights Into Leukocyte Trafficking in Inflammatory Arthritis - Imaging the Joint

The inappropriate accumulation and activation of leukocytes is a shared pathological feature of immune-mediated inflammatory diseases (IMIDs), such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Cellular accumulation is therefore an attractive target for therapeutic intervention. However, attempts to modulate leukocyte entry and exit from the joint have proven unsuccessful to date, indicating that gaps in our knowledge remain. Technological advancements are now allowing real-time tracking of leukocyte movement through arthritic joints or in vitro joint constructs. Coupling this technology with improvements in analyzing the cellular composition, location and interactions of leukocytes with neighboring cells has increased our understanding of the temporal dynamics and molecular mechanisms underpinning pathological accumulation of leukocytes in arthritic joints. In this review, we explore our current understanding of the mechanisms leading to inappropriate leukocyte trafficking in inflammatory arthritis, and how these evolve with disease progression. Moreover, we highlight the advances in imaging of human and murine joints, along with multi-cellular ex vivo joint constructs that have led to our current knowledge base.

The autoimmune response as a potential target for tolerance induction before the development of rheumatoid arthritis

Rheumatoid arthritis is a chronic inflammatory disease that affects the synovial joints. Although treatment options and efficacy have increased substantially in the past two decades, the disease cannot be cured or prevented. Therefore, rheumatoid arthritis still has a considerable effect on the quality of life of patients, not only because life-long medication is often required, but also because residual disease activity leads to progressive loss of function in the musculoskeletal system and extra-articular morbidity. Key future goals in the management of rheumatoid arthritis are the ability to induce long-lasting drug-free remission in patients with the disease (ie, to achieve a cure), and to prevent disease before it emerges. To reach these goals, it is pivotal to understand the autoimmune response underlying rheumatoid arthritis pathogenesis and to develop ways to permanently silence it (ie, to induce tolerance). For preventive studies, the identification of markers (clinical, immunological, and biological) predictive of future disease is crucial, as prevention of disease will not be feasible without the ability to identify relevant at-risk target populations. In this Series paper, we review the autoimmune response underlying rheumatoid arthritis, how rheumatoid arthritis-specific autoimmunity develops and evolves during the transition from health to disease, and how tolerance studies could be designed to achieve prevention or cure of the disease.

Novel insights into macrophage diversity in rheumatoid arthritis synovium

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease affecting joints and causing progressive damage and disability. Macrophages are of critical importance in the initiation and perpetuation of synovitis in RA, they can function as antigen presenting cells leading to T-cell dependent B-cell activation, assume a variety of inflammatory cell states with the production of destructive cytokines, but also contribute to tissue homeostasis/repair. The recent development of high-throughput technologies, including bulk and single cells RNA-sequencing, has broadened our understanding of synovial cell diversity, and opened novel perspectives to the discovery of new potential therapeutic targets in RA. In this review, we will focus on the relationship between the synovial macrophage infiltration and clinical disease severity and response to treatment. We will then provide a state-of-the-art picture of the biological roles of synovial macrophages and distinct macrophage subsets described in RA. Finally, we will review the effects of approved conventional and biologic drugs on the synovial macrophage component and highlight the therapeutic potential of future strategies to re-program macrophage phenotypes in RA.

Why remission is not enough: underlying disease mechanisms in RA that prevent cure

Cure is the aspirational aim for the treatment of all diseases, including chronic inflammatory conditions such as rheumatoid arthritis (RA); however, it has only been during the twenty-first century that remission, let alone cure, has been a regularly achievable target in RA. Little research has been carried out on how to cure RA, and the term 'cure' still requires definition for this disease. Even now, achieving a cure seems to be a rare occurrence among individuals with RA. Therefore, this Review is aimed at addressing the obstacles to the achievement of cure in RA. The differences between remission and cure in RA are first defined, followed by a discussion of the underlying factors (referred to as drivers) that prevent the achievement of cure in RA by triggering sustained immune activation and effector cytokine production. Such drivers include adaptive immune system activation, mesenchymal tissue priming and so-called 'remote' (non-immune and non-articular) factors. Strategies to target these drivers are also presented, with an emphasis on the development of strategies that could complement currently used cytokine inhibition and thereby improve the likelihood of curing RA.

68Ga-FAPI-04 PET-CT for molecular assessment of fibroblast activation and risk evaluation in systemic sclerosis-associated interstitial lung disease: a single-centre, pilot study

BACKGROUND

Interstitial lung disease (ILD) is the most common cause of death in systemic sclerosis. To date, the progression of systemic sclerosis-associated ILD is judged by the accrual of lung damage on CT and pulmonary function tests. However, diagnostic tools to assess disease activity are not available. Here, we tested the hypothesis that quantification of fibroblast activation by PET-CT using a 68Ga-labelled selective inhibitor of prolyl endopeptidase FAP (68Ga-FAPI-04) would correlate with ILD activity and disease progression in patients with systemic sclerosis-associated ILD.

METHODS

Between Sept 10, 2018, and April 8, 2020, 21 patients with systemic sclerosis-associated ILD confirmed by high-resolution CT (HRCT) within 12 months of inclusion and with onset of systemic sclerosis-associated ILD within 5 years or signs of progressive ILD and 21 controls without ILD were consecutively enrolled. All participants underwent 68Ga-FAPI-04 PET-CT imaging and standard-of-care procedures, including HRCT and pulmonary function tests at baseline. Patients with systemic sclerosis-associated ILD were followed for 6 months with HRCT and pulmonary function tests. We compared baseline 68Ga-FAPI-04 PET-CT uptake with standard diagnostic tools and predictors of ILD progression. The association of 68Ga-FAPI-04 uptake with changes in forced vital capacity was analysed using mixed-effects models. Follow-up 68Ga-FAPI-04 PET-CT scans were obtained in a subset of patients treated with nintedanib (follow-up between 6-10 months) to assess change over time.

FINDINGS

68Ga-FAPI-04 accumulated in fibrotic areas of the lungs in patients with systemic sclerosis-associated ILD compared with controls, with a median standardised uptake value (SUV) mean over the whole lung of 0·80 (IQR 0·60-2·10) in the systemic sclerosis-ILD group and 0·50 (0·40-0·50) in the control group (p<0·0001) and a mean whole lung maximal SUV of 4·40 (range 3·05-5·20) in the systemic sclerosis-ILD group compared with 0·70 (0·65-0·70) in the control group (p<0·0001). Whole-lung FAPI metabolic active volume (wlFAPI-MAV) and whole-lung total lesion FAPI (wlTL-FAPI) were not measurable in control participants, because no 68Ga-FAPI-04 uptake above background level was observed. In the systemic sclerosis-ILD group the median wlFAPI-MAV was 254·00 cm3 (IQR 163·40-442·30), and the median wlTL-FAPI was 183·60 cm3 (98·04-960·70). 68Ga-FAPI-04 uptake was higher in patients with extensive disease, with previous ILD progression, or high EUSTAR activity scores than in those with with limited disease, previously stable ILD, or low EUSTAR activity scores. Increased 68Ga-FAPI-04 uptake at baseline was associated with progression of ILD independently of extent of involvement on HRCT scan and the forced vital capacity at baseline. In consecutive 68Ga-FAPI-04 PET-CTs, changes in 68Ga-FAPI-04 uptake was concordant with the observed response to the fibroblast-targeting antifibrotic drug nintedanib.

INTERPRETATION

Our study presents the first in-human evidence that fibroblast activation correlates with fibrotic activity and disease progression in the lungs of patients with systemic sclerosis-associated ILD and that 68Ga-FAPI-04 PET-CT might improve risk assessment of systemic sclerosis-associated ILD.

FUNDING

German Research Foundation, Erlangen Anschubs-und Nachwuchsfinanzierung, Interdisziplinäres Zentrum für Klinische Forschung Erlangen, Bundesministerium für Bildung und Forschung, Deutsche Stiftung Systemische Sklerose, Wilhelm-Sander-Foundation, Else-Kröner-Fresenius-Foundation, European Research Council, Ernst-Jung-Foundation, and Clinician Scientist Program Erlangen.

Multiomics landscape of synovial fibroblasts in rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune disease characterized by tumor-like hyperplasia and inflammation of the synovium, which causes synovial cell invasion into the bone and cartilage. In RA pathogenesis, various molecules in effector cells (i.e., immune cells and mesenchymal cells) are dysregulated by genetic and environmental factors. Synovial fibroblasts (SFs), the most abundant resident mesenchymal cells in the synovium, are the major local effectors of the destructive joint inflammation and exert their effects through the pathogenic production of molecules such as interleukin-6.

MAIN BODY

To date, more than 100 RA susceptibility loci have been identified in genome-wide association studies (GWASs), and finding novel therapeutic targets utilizing genome analysis is considered a promising approach because some candidate causal genes identified by GWASs have previously been established as therapeutic targets. For further exploration of RA-responsible cells and cell type-specific therapeutic targets, integrated analysis (or functional genome analysis) of the genome and intermediate traits (e.g., transcriptome and epigenome) is crucial.

CONCLUSION

This review builds on the existing knowledge regarding the epigenomic abnormalities in RASFs and discusses the recent advances in single-cell analysis, highlighting the prospects of SFs as targets for safer and more effective therapies against RA.

Etiologies of Rheumatoid Arthritis: Update on Mucosal, Genetic, and Cellular Pathogenesis

Purpose of Review

Over the last few years, the scientific community has made significant progress in understanding the etiology of rheumatoid arthritis (RA). In this review, we summarize those key findings and trends.

Recent Findings

New data strongly implicates respiratory exposures, obesity, diet and microbiome, genetics, and their interactions in the etiology of RA. Furthermore, anti-posttranslationally modified protein antibodies (AMPAs) and abnormal glycosylation may be additional biomarkers for RA. Finally, functional genomics techniques implicate loss of certain macrophage populations and proliferation of synovial fibroblasts in RA.

Summary

These findings support the notion that RA originates at mucosal sites, augmented by genetic predisposition, and mediated by certain cell types including macrophages and fibroblasts. Weight loss, physical activity, and diet are additional modifiable factors beyond smoking cessation that can reduce risk of RA. Future epidemiologic and translational studies leveraging multi-omics approaches will help map the precise sequence of events in RA pathogenesis.

Epigenomic and transcriptomic analysis of chronic inflammatory diseases

Chronic inflammatory diseases (CIDs) have complex pathologies that result from aberrant and persistent immune responses. However, the precise triggers and mechanisms remain elusive. An important aspect of CID research focuses on epigenetics modifications, which regulate gene expression and provide a dynamic transcriptional response to inflammation. In recent years, mounting evidence has demonstrated an association between epigenomic and transcriptomic dysregulation and the phenotypes of CIDs. In particular, epigenetic changes at cis-regulatory elements have provided new insights for immune cell-specific alterations that contribute to disease etiology. Furthermore, the advancements in single-cell genomics provide novel solutions to cell type heterogeneity, which has long posed challenges for CID diagnosis and treatment. In this review, we discuss the current state of epigenomics research of CID and the insights derived from single-cell transcriptomic and epigenomic studies.

Single-cell RNA sequencing: An overview for the ophthalmologist

Understanding the molecular composition of pathogenic tissues is a critical step in understanding the pathophysiology of disease and designing therapeutics. First described in 2009, single cell RNA sequencing (scRNAseq) is a methodology whereby thousands of cells are simultaneously isolated into individual micro-environments that can be altered experimentally and the genome-wide RNA expression of each cell is captured. It has undergone significant technological improvement over the last decade and gained tremendous popularity. scRNAseq is an improvement over prior pooled RNA analyses which cannot identify the cellular composition and heterogeneity of a tissue of interest. This new approach offers new opportunity for new discovery, as tissue samples can now be sub-categorized into groups of cell types based on genome-wide gene expression in an unbiased fashion. As ophthalmologists, we are uniquely positioned to obtain pathologic samples from the eye for further study. ScRNAseq has already been applied in ophthalmology to characterize retinal tissue, and it may offer the key to understanding various pathological processes in the future.

Mini-Review: The Administration of Apoptotic Cells for Treating Rheumatoid Arthritis: Current Knowledge and Clinical Perspectives

Rheumatoid arthritis (RA) is a chronic immune-mediated disease managed by conventional synthetic drugs, such as methotrexate (MTX), and targeted drugs including biological agents. Cell-based therapeutic approaches are currently developed in RA, mainly mesenchymal stroma cell-based approaches. Early-stage apoptotic cells possess direct and indirect anti-inflammatory properties. During the elimination of dying cells (a process called efferocytosis), specific mechanisms operate to control immune responses. There are compelling evidences in experimental models of arthritis indicating that apoptotic cell administration may benefit joint inflammation, and may even have therapeutic effects on arthritis. Additionally, it has been demonstrated that apoptotic cells could be administered with standard treatments of RA, such as MTX or TNF inhibitors (TNFi), given even a synergistic response with TNFi. Interestingly, apoptotic cell infusion has been successfully experienced to prevent acute graft-vs.-host disease after hematopoietic cell transplantation in patients with hematologic malignancies, with a good safety profile. In this mini-review, the apoptotic cell-based therapy development in arthritis is discussed, as well as its transfer in the short-term to an innovative treatment for patients with RA. The use of apoptotic cell-derived factors, including secretome or phosphatidylserine-containing liposomes, in RA are also discussed.

Multipotent Mesenchymal Stromal Cells in Rheumatoid Arthritis and Systemic Lupus Erythematosus; From a Leading Role in Pathogenesis to Potential Therapeutic Saviors?

The pathogenesis of the autoimmune rheumatological diseases including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) is complex with the involvement of several immune cell populations spanning both innate and adaptive immunity including different T-lymphocyte subsets and monocyte/macrophage lineage cells. Despite therapeutic advances in RA and SLE, some patients have persistent and stubbornly refractory disease. Herein, we discuss stromal cells' dual role, including multipotent mesenchymal stromal cells (MSCs) also used to be known as mesenchymal stem cells as potential protagonists in RA and SLE pathology and as potential therapeutic vehicles. Joint MSCs from different niches may exhibit prominent pro-inflammatory effects in experimental RA models directly contributing to cartilage damage. These stromal cells may also be key regulators of the immune system in SLE. Despite these pro-inflammatory roles, MSCs may be immunomodulatory and have potential therapeutic value to modulate immune responses favorably in these autoimmune conditions. In this review, the complex role and interactions between MSCs and the haematopoietically derived immune cells in RA and SLE are discussed. The harnessing of MSC immunomodulatory effects by contact-dependent and independent mechanisms, including MSC secretome and extracellular vesicles, is discussed in relation to RA and SLE considering the stromal immune microenvironment in the diseased joints. Data from translational studies employing MSC infusion therapy against inflammation in other settings are contextualized relative to the rheumatological setting. Although safety and proof of concept studies exist in RA and SLE supporting experimental and laboratory data, robust phase 3 clinical trial data in therapy-resistant RA and SLE is still lacking.

Dermal Drivers of Injury-Induced Inflammation: Contribution of Adipocytes and Fibroblasts

Irregular inflammatory responses are a major contributor to tissue dysfunction and inefficient repair. Skin has proven to be a powerful model to study mechanisms that regulate inflammation. In particular, skin wound healing is dependent on a rapid, robust immune response and subsequent dampening of inflammatory signaling. While injury-induced inflammation has historically been attributed to keratinocytes and immune cells, a vast body of evidence supports the ability of non-immune cells to coordinate inflammation in numerous tissues and diseases. In this review, we concentrate on the active participation of tissue-resident adipocytes and fibroblasts in pro-inflammatory signaling after injury, and how altered cellular communication from these cells can contribute to irregular inflammation associated with aberrant wound healing. Furthering our understanding of how tissue-resident mesenchymal cells contribute to inflammation will likely reveal new targets that can be manipulated to regulate inflammation and repair.

Insights of rheumatoid arthritis biomarkers

Rheumatoid arthritis is a chronic, autoimmune connective tissue disease. In addition to joint involvement, extra-articular changes and organ complications also occur in the course of the disease. Untreated disease leads to disability and premature death. Therefore, it is important to recognise and begin treatment early. Based on the presence of rheumatoid factor and antibodies against citrullinated peptides, we can distinguish two forms of the disease: seropositive and seronegative. Research continues to elucidate the mechanisms of the onset of the disease, as well as to uncover factors that induce and influence the activity of the disease. The presence of markers that initially appear and affect the course of the disease can potentially aid in patient treatment. In this article, we have collected biomarkers of rheumatoid arthritis that are well understood as well as those that have been recently described.

Key opinion leaders - a critical perspective

Enormous progress has been made in the field of rheumatology in the past several decades, historically led by publicly funded academic innovators but in more recent times with much greater involvement of the pharmaceutical industry. This shift in resources has created a complex new model for reinvestment in the medical community in which the vast majority of private funds are redirected towards influencing the prescription behaviour of practitioners through 'key opinion leaders', with the main purpose of enhancing and perpetuating profit rather than innovation and critical thinking, and often at the expense of partnerships with scientists (that is, basic and translational researchers) and academic collaborations. This new episteme brings multiple opportunities to rethink approaches to sustaining long-term critical research in the field, ultimately maximizing the return on investment: scientific knowledge for the benefit of patients and society. Central to such strategies should be the rebalancing of academia-industry partnerships towards academic research and the involvement of 'innovation and knowledge leaders', rather than mostly key opinion leaders.

Fibroblast-like synoviocytes in rheumatoid arthritis: Surface markers and phenotypes

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease that mainly affects synovial joints. During the course of RA, the synovium transforms into hyperplastic invasive tissue, leading to cartilage and bone destruction. Fibroblast-like synoviocytes (FLS) in the synovial lining develop aggressive phenotypes and produce pathogenic mediators that lead to the occurrence and progression of disease, playing a major role in RA pathophysiology. Therefore, research on FLS has become the main focus within the RA field. With technical advances and the development of multi-omics comprehensive analysis approaches, it has become possible to identify different FLS subsets via high-throughput sequencing and investigate differences between FLS phenotypes, allowing for the detailed study of RA pathogenesis. This review summarizes recent works on FLS subtypes and the surface marker proteins identified for different subtypes, providing a theoretical basis and reference for future studies on FLS in RA. The current work also addresses the clinical potential of FLS surface markers in RA based on related research from other fields.

Targeted photodynamic therapy selectively kills activated fibroblasts in experimental arthritis

Objective

In RA, synovial fibroblasts become activated. These cells express fibroblast activation protein (FAP) and contribute to the pathogenesis by producing cytokines, chemokines and proteases. Selective depletion in inflamed joints could therefore constitute a viable treatment option. To this end, we developed and tested a new therapeutic strategy based on the selective destruction of FAP-positive cells by targeted photodynamic therapy (tPDT) using the anti-FAP antibody 28H1 coupled to the photosensitizer IRDye700DX.

Methods

After conjugation of IRDye700DX to 28H1, the immunoreactive binding and specificity of the conjugate were determined. Subsequently, tPDT efficiency was established in vitro using a 3T3 cell line stably transfected with FAP. The biodistribution of [¹¹¹In]In-DTPA-28H1 with and without IRDye700DX was assessed in healthy C57BL/6N mice and in C57BL/6N mice with antigen-induced arthritis. The potential of FAP-tPDT to induce targeted damage was determined ex vivo by treating knee joints from C57BL/6N mice with antigen-induced arthritis 24 h after injection of the conjugate. Finally, the effect of FAP-tPDT on arthritis development was determined in mice with collagen-induced arthritis.

Results

28H1-700DX was able to efficiently induce FAP-specific cell death in vitro. Accumulation of the anti-FAP antibody in arthritic knee joints was not affected by conjugation with the photosensitizer. Arthritis development was moderately delayed in mice with collagen-induced arthritis after FAP-tPDT.

Conclusion

Here we demonstrate the feasibility of tPDT to selectively target and kill FAP-positive fibroblasts in vitro and modulate arthritis in vivo using a mouse model of RA. This approach may have therapeutic potential in (refractory) arthritis.

Cartilage Targets of Knee Osteoarthritis Shared by Both Genders

As the leading cause of disability, osteoarthritis (OA) affects people of all ages, sexes, and races. With the increasing understanding of OA, the sex differences have attracted specific attention as the burden of OA is greater in women. There is no doubt that gender-specific OA management has great potential for precision treatment. On the other hand, from the marketing aspect, a medication targeting the OA-responsive biomarker(s) shared by both genders is more favorable for drug development. Thus, in the current study, a published transcriptome dataset of knee articular cartilage was used to compare OA and healthy samples for identifying the genes with the same significantly different expression trend in both males and females. With 128 genes upregulated and 143 genes downregulated in both OA males and females, 9 KEGG pathways have been enriched based on the current knowledge, including 'renal cell carcinoma,' 'ECM-receptor interaction,' 'HIF-1 signaling pathway,' 'MicroRNAs in cancer,' 'focal adhesion,' 'Relaxin signaling pathway,' 'breast cancer,' 'PI3K-Akt signaling pathway,' and 'human papillomavirus infection.' Here, we explore the potential impacts of these clusters in OA. We also analyze the identified 'cell plasma membrane related genes' in-depth to identify the potential chondrocyte cell surface target(s) of OA management.

Defining human mesenchymal and epithelial heterogeneity in response to oral inflammatory disease

Human oral soft tissues provide the first barrier of defence against chronic inflammatory disease and hold a remarkable scarless wounding phenotype. Tissue homeostasis requires coordinated actions of epithelial, mesenchymal, and immune cells. However, the extent of heterogeneity within the human oral mucosa and how tissue cell types are affected during the course of disease progression is unknown. Using single-cell transcriptome profiling we reveal a striking remodelling of the epithelial and mesenchymal niches with a decrease in functional populations that are linked to the aetiology of the disease. Analysis of ligand–receptor interaction pairs identify potential intercellular hubs driving the inflammatory component of the disease. Our work establishes a reference map of the human oral mucosa in health and disease, and a framework for the development of new therapeutic strategies.

Electrospun Scaffold Micro-Architecture Induces an Activated Transcriptional Phenotype within Tendon Fibroblasts

Biomaterial augmentation of surgically repaired rotator cuff tendon tears aims to improve the high failure rates (∼40%) of traditional repairs. Biomaterials that can alter cellular phenotypes through the provision of microscale topographical cues are now under development. We aimed to systematically evaluate the effect of topographic architecture on the cellular phenotype of fibroblasts from healthy and diseased tendons. Electrospun polydioxanone scaffolds with fiber diameters ranging from 300 to 4000 nm, in either a highly aligned or random configuration, were produced. Healthy tendon fibroblasts cultured for 7 days on scaffolds with highly aligned fibers demonstrated a distinctive elongated morphology, whilst those cultured on randomly configured fibers demonstrated a flattened and spread morphology. The effect of scaffold micro-architecture on the transcriptome of both healthy and diseased tendon fibroblasts was assessed with bulk RNA-seq. Both healthy (n = 3) and diseased tendon cells (n = 3) demonstrated a similar transcriptional response to architectural variants. Gene set enrichment analysis revealed that large diameter (≥2000 nm) aligned scaffolds induced an upregulation of genes involved in cellular replication and a downregulation of genes defining inflammatory responses and cell adhesion. Similarly, PDPN and CD248, markers of inflammatory or "activated" fibroblasts, were downregulated during culture of both healthy and diseased fibroblasts on aligned scaffolds with large (≥2000 nm) fiber diameters. In conclusion scaffold architectures resembling that of disordered type III collagen, typically present during the earlier phases of wound healing, resulted in tendon fibroblast activation. Conversely, scaffolds mimicking aligned diameter collagen I fibrils, present during tissue remodelling, did not activate tendon derived fibroblasts. This has implications for the design of scaffolds used during rotator cuff repair augmentation.

Diversity and Biology of Cancer-Associated Fibroblasts

Efforts to develop anti-cancer therapies have largely focused on targeting the epithelial compartment, despite the presence of non-neoplastic stromal components that substantially contribute to the progression of the tumor. Indeed, cancer cell survival, growth, migration, and even dormancy are influenced by the surrounding tumor microenvironment (TME). Within the TME, cancer-associated fibroblasts (CAFs) have been shown to play several roles in the development of a tumor. They secrete growth factors, inflammatory ligands, and extracellular matrix proteins that promote cancer cell proliferation, therapy resistance, and immune exclusion. However, recent work indicates that CAFs may also restrain tumor progression in some circumstances. In this review, we summarize the body of work on CAFs, with a particular focus on the most recent discoveries about fibroblast heterogeneity, plasticity, and functions. We also highlight the commonalities of fibroblasts present across different cancer types, and in normal and inflammatory states. Finally, we present the latest advances regarding therapeutic strategies targeting CAFs that are undergoing preclinical and clinical evaluation.

Relationship Between Inflammation and Metabolism in Patients With Newly Presenting Rheumatoid Arthritis

Background

Systemic inflammation in rheumatoid arthritis (RA) is associated with metabolic changes. We used nuclear magnetic resonance (NMR) spectroscopy-based metabolomics to assess the relationship between an objective measure of systemic inflammation [C-reactive protein (CRP)] and both the serum and urinary metabolome in patients with newly presenting RA.

Methods

Serum (n=126) and urine (n=83) samples were collected at initial presentation from disease modifying anti-rheumatic drug naïve RA patients for metabolomic profile assessment using 1-dimensional ¹H-NMR spectroscopy. Metabolomics data were analysed using partial least square regression (PLS-R) and orthogonal projections to latent structure discriminant analysis (OPLS-DA) with cross validation.

Results

Using PLS-R analysis, a relationship between the level of inflammation, as assessed by CRP, and the serum (p=0.001) and urinary (p<0.001) metabolome was detectable. Likewise, following categorisation of CRP into tertiles, patients in the lowest CRP tertile and the highest CRP tertile were statistically discriminated using OPLS-DA analysis of both serum (p=0.033) and urinary (p<0.001) metabolome. The most highly weighted metabolites for these models included glucose, amino acids, lactate, and citrate. These findings suggest increased glycolysis, perturbation in the citrate cycle, oxidative stress, protein catabolism and increased urea cycle activity are key characteristics of newly presenting RA patients with elevated CRP.

Conclusions

This study consolidates our understanding of a previously identified relationship between serum metabolite profile and inflammation and provides novel evidence that there is a relationship between urinary metabolite profile and inflammation as measured by CRP. Identification of these metabolic perturbations provides insights into the pathogenesis of RA and may help in the identification of therapeutic targets.

The immunology of rheumatoid arthritis

The immunopathogenesis of rheumatoid arthritis (RA) spans decades, beginning with the production of autoantibodies against post-translationally modified proteins (checkpoint 1). After years of asymptomatic autoimmunity and progressive immune system remodeling, tissue tolerance erodes and joint inflammation ensues as tissue-invasive effector T cells emerge and protective joint-resident macrophages fail (checkpoint 2). The transition of synovial stromal cells into autoaggressive effector cells converts synovitis from acute to chronic destructive (checkpoint 3). The loss of T cell tolerance derives from defective DNA repair, causing abnormal cell cycle dynamics, telomere fragility and instability of mitochondrial DNA. Mitochondrial and lysosomal anomalies culminate in the generation of short-lived tissue-invasive effector T cells. This differentiation defect builds on a metabolic platform that shunts glucose away from energy generation toward the cell building and motility programs. The next frontier in RA is the development of curative interventions, for example, reprogramming T cell defects during the period of asymptomatic autoimmunity.

Rheumatology in the era of precision medicine: synovial tissue molecular patterns and treatment response in rheumatoid arthritis

PURPOSE OF REVIEW

A critical unmet need in rheumatoid arthritis (RA) is the identification of biomarkers that predict which of the available medications will be most effective for an individual in order to lower disease activity sooner than is afforded by the current treat-to-target approach. Here we will discuss recent reports examining the potential for synovial tissue molecular, cellular, and spatial profiling in defining objective measures of treatment response and therein developing personalized medicine for RA.

RECENT FINDINGS

Recent high-dimensional molecular profiling of RA synovium has provided unprecedented resolution of the cell types and pathways in tissues affected by rheumatic diseases. Heightened attention to tissue architecture is also emerging as a means to classify individual disease variation that may allow patients to be further stratified by therapeutic response. Although this wealth of data may have already pinpointed promising biomarkers, additional studies, likely including tissue-based functional drug response assays, will be required to demonstrate how the complex tissue environment responds.

SUMMARY

Molecular, cellular, and more recently spatial profiling of the RA synovium are uncovering fundamental features of the disease. Current investigations are examining whether this information will provide meaningful biomarkers for individualized medicine in RA.

Distinct Glucocorticoid Receptor Actions in Bone Homeostasis and Bone Diseases

Glucocorticoids (GCs) are steroid hormones that respond to stress and the circadian rhythm. Pharmacological GCs are widely used to treat autoimmune and chronic inflammatory diseases despite their adverse effects on bone after long-term therapy. GCs regulate bone homeostasis in a cell-type specific manner, affecting osteoblasts, osteoclasts, and osteocytes. Endogenous physiological and exogenous/excessive GCs act via nuclear receptors, mainly via the GC receptor (GR). Endogenous GCs have anabolic effects on bone mass regulation, while excessive or exogenous GCs can cause detrimental effects on bone. GC-induced osteoporosis (GIO) is a common adverse effect after GC therapy, which increases the risk of fractures. Exogenous GC treatment impairs osteoblastogenesis, survival of the osteoblasts/osteocytes and prolongs the longevity of osteoclasts. Under normal physiological conditions, endogenous GCs are regulated by the circadian rhythm and circadian genes display oscillatory rhythmicity in bone cells. However, exogenous GCs treatment disturbs the circadian rhythm. Recent evidence suggests that the disturbed circadian rhythm by continuous exogenous GCs treatment can in itself hamper bone integrity. GC signaling is also important for fracture healing and rheumatoid arthritis, where crosstalk among several cell types including macrophages and stromal cells is indispensable. This review summarizes the complexity of GC actions via GR in bone cells at cellular and molecular levels, including the effect on circadian rhythmicity, and outlines new therapeutic possibilities for the treatment of their adverse effects.

Metabolic Reprogramming of Fibroblasts as Therapeutic Target in Rheumatoid Arthritis and Cancer: Deciphering Key Mechanisms Using Computational Systems Biology Approaches

Fibroblasts, the most abundant cells in the connective tissue, are key modulators of the extracellular matrix (ECM) composition. These spindle-shaped cells are capable of synthesizing various extracellular matrix proteins and collagen. They also provide the structural framework (stroma) for tissues and play a pivotal role in the wound healing process. While they are maintainers of the ECM turnover and regulate several physiological processes, they can also undergo transformations responding to certain stimuli and display aggressive phenotypes that contribute to disease pathophysiology. In this review, we focus on the metabolic pathways of glucose and highlight metabolic reprogramming as a critical event that contributes to the transition of fibroblasts from quiescent to activated and aggressive cells. We also cover the emerging evidence that allows us to draw parallels between fibroblasts in autoimmune disorders and more specifically in rheumatoid arthritis and cancer. We link the metabolic changes of fibroblasts to the toxic environment created by the disease condition and discuss how targeting of metabolic reprogramming could be employed in the treatment of such diseases. Lastly, we discuss Systems Biology approaches, and more specifically, computational modeling, as a means to elucidate pathogenetic mechanisms and accelerate the identification of novel therapeutic targets.

The Lipid Paradox as a Metabolic Checkpoint and Its Therapeutic Significance in Ameliorating the Associated Cardiovascular Risks in Rheumatoid Arthritis Patients

While the most common manifestations associated with rheumatoid arthritis (RA) are synovial damage and inflammation, the systemic effects of this autoimmune disorder are life-threatening, and are prevalent in 0.5–1% of the population, mainly associated with cardiovascular disorders (CVDs). Such effects have been instigated by an altered lipid profile in RA patients, which has been reported to correlate with CV risks. Altered lipid paradox is related to inflammatory burden in RA patients. The review highlights general lipid pathways (exogenous and endogenous), along with the changes in different forms of lipids and lipoproteins in RA conditions, which further contribute to elevated risks of CVDs like ischemic heart disease, atherosclerosis, myocardial infarction etc. The authors provide a deep insight on altered levels of low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TGs) in RA patients and their consequence on the cardiovascular health of the patient. This is followed by a detailed description of the impact of anti-rheumatoid therapy on the lipid profile in RA patients, comprising DMARDs, corticosteroids, anti-TNF agents, anti-IL-6 agents, JAK inhibitors and statins. Furthermore, this review elaborates on the prospects to be considered to optimize future investigation on management of RA and treatment therapies targeting altered lipid paradigms in patients.

TGFβ-blockade uncovers stromal plasticity in tumors by revealing the existence of a subset of interferon-licensed fibroblasts

Despite the increasing interest in targeting stromal elements of the tumor microenvironment, we still face tremendous challenges in developing adequate therapeutics to modify the tumor stromal landscape. A major obstacle to this is our poor understanding of the phenotypic and functional heterogeneity of stromal cells in tumors. Herein, we perform an unbiased interrogation of tumor mesenchymal cells, delineating the co-existence of distinct subsets of cancer-associated fibroblasts (CAFs) in the microenvironment of murine carcinomas, each endowed with unique phenotypic features and functions. Furthermore, our study shows that neutralization of TGFβ in vivo leads to remodeling of CAF dynamics, greatly reducing the frequency and activity of the myofibroblast subset, while promoting the formation of a fibroblast population characterized by strong response to interferon and heightened immunomodulatory properties. These changes correlate with the development of productive anti-tumor immunity and greater efficacy of PD1 immunotherapy. Along with providing the scientific rationale for the evaluation of TGFβ and PD1 co-blockade in the clinical setting, this study also supports the concept of plasticity of the stromal cell landscape in tumors, laying the foundation for future investigations aimed at defining pathways and molecules to program CAF composition for cancer therapy.

Persistent inflammatory and non-inflammatory mechanisms in refractory rheumatoid arthritis

Despite nearly three decades of advances in the management of rheumatoid arthritis (RA), a substantial minority of patients are exposed to multiple DMARDs without necessarily benefitting from them; a group of patients variously designated as having 'difficult to treat', 'treatment-resistant' or 'refractory' RA. This Review of refractory RA focuses on two types of patients: those for whom multiple targeted therapies lack efficacy and who have persistent inflammatory pathology, which we designate as persistent inflammatory refractory RA (PIRRA); and those with supposed refractory RA who have continued disease activity that is predominantly independent of objective evidence of inflammation, which we designate as non-inflammatory refractory RA (NIRRA). These two types of disease are not mutually exclusive, but identifying those individuals with predominant PIRRA or NIRRA is important, as it informs distinct treatment and management approaches. This Review outlines the clinical differences between PIRRA and NIRRA, the genetic and epigenetic mechanisms and immune pathways that might contribute to the immunopathogenesis of recalcitrant synovitis in PIRRA, and a possible basis for non-inflammatory symptomatology in NIRRA. Future approaches towards the definition of refractory RA and the application of single-cell and integrated omics technologies to the identification of refractory RA endotypes are also discussed.

Synovial biopsies in clinical practice and research: current developments and perspectives

Synovial biopsy techniques have developed and widely expanded over the past few years, in particular due to the development of ultrasound-guided procedures. This article reviews the different techniques, clinical applications, and the latest advances in translational research as well as current challenges and perspectives. The first part focuses on different techniques available for biopsy, along with their feasibility, success rate, tolerance, and training requirements. In the second part, clinical applications are described. Data on diagnostic performances are reported, especially regarding septic arthritis. Translational research applications are described and explained in the final part, from the early histological studies and the first description of pathotype to more recent technologies involving -omics. Latest developments involving single-cell RNA sequence analysis have allowed the discovery of new cell subpopulations with remarkable roles in RA pathophysiology. These studies pave the ground for the discovery of new therapeutic targets and the implementation of personalized therapy in RA.

Key Point •This review provides an overview of synovial biopsy techinques and applications especially in clinical and translational research.

Comparison of similar cells: Mesenchymal stromal cells and fibroblasts

Almost from all organs, both mesenchymal stromal cells and fibroblasts can be isolated. Mesenchymal stromal cells (MSCs) are the most preferred cellular therapeutic agents with the regenerative potential, and fibroblasts are one of the most abundant cell types with the ability to maintain homeostasis. Because of the promising properties of MSCs, they have been well studied and their differentiation potentials, immunomodulatory potentials, gene expression profiles are identified. It has been observed that fibroblasts and mesenchymal stromal cells have similar morphology, gene expression patterns, surface markers, proliferation, differentiation, and immunomodulatory capacities. Thus, it is hard to distinguish these two cell types. Epigenetic signatures, i.e., methylation patterns of cells, are the only usable promising difference between them. Such significant similarities show that these two cells may be related to each other.

Reprogramming of synovial macrophage metabolism by synovial fibroblasts under inflammatory conditions

Background

Macrophages adapt to microenvironments, and change metabolic status and functions to regulate inflammation and/or maintain homeostasis. In joint cavities, synovial macrophages (SM) and synovial fibroblasts (SF) maintain homeostasis. However, under inflammatory conditions such as rheumatoid arthritis (RA), crosstalk between SM and SF remains largely unclear.

Methods

Immunofluorescent staining was performed to identify localization of SM and SF in synovium of collagen antibody induced arthritis (CAIA) model mice and normal mice. Murine arthritis tissue-derived SM (ADSM), arthritis tissue-derived SF (ADSF) and normal tissue-derived SF (NDSF) were isolated and the purity of isolated cells was examined by RT-qPCR and flow cytometry analysis. RNA-seq was conducted to reveal gene expression profile in ADSM, NDSF and ADSF. Cellular metabolic status and expression levels of metabolic genes and inflammatory genes were analyzed in ADSM treated with ADSM-conditioned medium (ADSM-CM), NDSF-CM and ADSF-CM.

Results

SM and SF were dispersed in murine hyperplastic synovium. Isolations of ADSM, NDSF and ADSF to analyze the crosstalk were successful with high purity. From gene expression profiles by RNA-seq, we focused on secretory factors in ADSF-CM, which can affect metabolism and inflammatory activity of ADSM. ADSM exposed to ADSF-CM showed significantly upregulated glycolysis and mitochondrial respiration as well as glucose and glutamine uptake relative to ADSM exposed to ADSM-CM and NDSF-CM. Furthermore, mRNA expression levels of metabolic genes, such as Slc2a1, Slc1a5, CD36, Pfkfb1, Pfkfb3 and Irg1, were significantly upregulated in ADSM treated with ADSF-CM. Inflammation marker genes, including Nos2, Tnf, Il-1b and CD86, and the anti-inflammatory marker gene, Il-10, were also substantially upregulated by ADSF-CM. On the other hand, NDSF-CM did not affect metabolism and gene expression in ADSM.

Conclusions

These findings suggest that crosstalk between SM and SF under inflammatory conditions can induce metabolic reprogramming and extend SM viability that together can contribute to chronic inflammation in RA.

The Application of Single-Cell RNA Sequencing in Studies of Autoimmune Diseases: a Comprehensive Review

Complex composition is one of the most important features of the immune system, involving many types of organs, tissues, cells, and molecules that perform immune functions. The normal function of each component of the immune system is the guarantee for maintaining the relatively stable immune function of the body. When the self-immune tolerance mechanism of the body is unregulated or destroyed, the immune system reacts to autoantigens, resulting in damage to self-tissues and organs or an immunopathological state with abnormal functions. Autoimmune diseases are diverse, and their pathogenesis is complicated. Various immune cells and their interactions play significant roles in the occurrence and development of diseases. The solution to heterogeneity of immune cells is the basic science and translational understanding of how genes and the environment interact to induce disease so that we can develop personalized medicine, a goal that has to this point eluded scientists. Single-cell RNA sequencing (scRNA-Seq) refers to a new technique allowing high-throughput sequencing analysis of the whole transcriptome to reveal the gene expression status of individual cells. It has emerged as an indispensable tool in the field of life science research, and can help identify the complex mechanism of cell heterogeneity, discover new cell subsets, and help uncover the molecular mechanisms of pathogenesis, the evolution of disorders, and drug resistance. This information can provide us with new strategies for diagnosis and prognostic evaluation, as well as monitoring treatment responses. In this review, we summarize the crucial experimental procedures used for single-cell RNA sequencing, and the current applications of this technique to study autoimmune diseases are described in detail. This technique will be widely used in more in-depth studies of autoimmune diseases and will contribute to the diagnosis and therapies of these disorders.

A biopolymer-based and inflammation-responsive nanodrug for rheumatoid arthritis treatment via inhibiting JAK-STAT and JNK signalling pathways

Rheumatoid arthritis (RA) is a common chronic autoimmune disease associated with progressive disability, systemic complications, and poor prognosis. The improved understanding of the roles of immune signaling pathway inhibitors has shed light on designing new and more effective approaches for RA treatment. In this work, an inflammation-responsive and molecularly targeted drug system has been developed for RA therapy. The drug carrier was synthesized by covalently grafting hydrophobic cholesterol (Chol) molecules onto a hydrophilic chondroitin sulfate (CS) chain via the inflammation-responsive diselenide bonds (SeSe). The resultant amphiphilic polymer CSSeSeChol readily forms nanoparticles (NPs) and encapsulates two kinase inhibitors tofacitinib and SP600125 in aqueous media. Upon administration into the RA mouse model, the nanodrug accumulates in RA lesions and releases the inhibitors for regulating the JAK-STAT and JNK pathways. As a result, the nanodrug exhibits satisfactory efficacy in RA treatment by suppressing the expression of relevant pro-inflammatory cytokines, blocking the activation of osteoclasts and providing protection for cartilage and joints.

Fibrosis: from mechanisms to medicines

Fibrosis can affect any organ and is responsible for up to 45% of all deaths in the industrialized world. It has long been thought to be relentlessly progressive and irreversible, but both preclinical models and clinical trials in various organ systems have shown that fibrosis is a highly dynamic process. This has clear implications for therapeutic interventions that are designed to capitalize on this inherent plasticity. However, despite substantial progress in our understanding of the pathobiology of fibrosis, a translational gap remains between the identification of putative antifibrotic targets and conversion of this knowledge into effective treatments in humans. Here we discuss the transformative experimental strategies that are being leveraged to dissect the key cellular and molecular mechanisms that regulate fibrosis, and the translational approaches that are enabling the emergence of precision medicine-based therapies for patients with fibrosis.

Paired Rheumatoid Arthritis Synovial Biopsies From Small and Large Joints Show Similar Global Transcriptomic Patterns With Enrichment of Private Specificity TCRB and TCR Signaling Pathways

Objectives

We explored histological and transcriptomic profiles of paired synovial biopsies from rheumatoid arthritis (RA) patients, in order to assess homogeneity in synovial tissue at the individual level.

Methods

Synovial biopsies were performed simultaneously in one small and one large joint per patient using needle-arthroscopy for the knee and ultrasound-guided biopsy for the hand or wrist. Synovium from individuals with osteoarthritis was used as controls. Paraffin-embedded samples were stained for CD3, CD20, and CD68. Total RNA was hybridized on high-density microarrays. TCRB variable sequences were obtained from synovial and blood RNA samples.

Results

Twenty paired biopsies from 10 RA patients with active disease were analyzed. Semi-quantification of histological markers showed a positive correlation for synovial hyperplasia, inflammatory infiltrates and CD3-positive T cells between pairs. Pairwise comparison of transcriptomic profiles showed similar expression of RA-related molecular pathways (TCR signaling, T cell costimulation and response to TNFα). T cells clonotypes were enriched in all but one joints compared to blood, regardless of the magnitude of T cell infiltration. Enriched clonotypes were shared between pairs (23-100%), but this was less the case in pairs of joints displaying weaker T cell signatures and more pronounced germinal center-like transcriptomic profiles.

Conclusion

Cellular and molecular alterations in RA synovitis are similar between small and large joints from the same patient. Interindividual differences in magnitude of T cell infiltrates and distribution of enriched T cell clonotypes support the concept of distinct synovial pathotypes in RA that are associated with systemic versus local antigen-driven activation of T cells.

Efficacy, patient-reported outcomes, and safety of the anti-granulocyte macrophage colony-stimulating factor antibody otilimab (GSK3196165) in patients with rheumatoid arthritis: a randomised, phase 2b, dose-ranging study

BACKGROUND

The human monoclonal antibody otilimab inhibits granulocyte-macrophage colony-stimulating factor (GM-CSF), a key driver in immune-mediated inflammatory conditions. We aimed to evaluate the efficacy, safety, and key patient-reported outcomes related to pain in patients with active rheumatoid arthritis receiving otilimab.

METHODS

This phase 2b, dose-ranging, multicentre, placebo-controlled study was done at 64 sites across 14 countries. Patients aged 18 years or older with rheumatoid arthritis who were receiving stable methotrexate were randomly assigned (1:1:1:1:1:1) to subcutaneous placebo or otilimab 22·5 mg, 45 mg, 90 mg, 135 mg, or 180 mg, plus methotrexate, once weekly for 5 weeks, then every other week until week 50. The randomisation schedule was generated by the sponsor, and patients were assigned to treatment by interactive response technology. Randomisation was blocked (block size of six) but was not stratified. Investigators, patients, and the sponsor were blinded to treatment. An unblinded administrator prepared and administered the study drug. The primary endpoint was the proportion of patients who achieved disease activity score for 28 joints with C-reactive protein (DAS28-CRP) <2·6 at week 24. Patients who were not in the otilimab 180 mg group, without a good or moderate European League Against Rheumatism response (week 12) or with DAS28-CRP >3·2 (week 24) escaped to otilimab 180 mg. Patients who escaped were treated as non-responders in their original assigned group. Safety endpoints were incidence of adverse events and serious adverse events, infections, and pulmonary events. Efficacy and safety outcomes were assessed in the intention-to-treat population. This study is registered with ClinicalTrials.gov, NCT02504671.

FINDINGS

Between July 23, 2015, and Dec 29, 2017, 222 patients were randomly assigned (37 to each group). 86 (49%) of 175 escaped to otilimab 180 mg at week 12 and 57 (69%) of 83 at week 24. At week 24, the proportion of patients with DAS28-CRP <2·6 was two (5%) of 37 in the otilimab 22·5 mg group, six (16%) of 37 in the 45 mg group, seven (19%) of 37 in the 90 mg group, five (14%) of 37 in the 135 mg group, five (14%) of 37 in the 180 mg, and one (3%) of 37 in the placebo group. The largest difference was achieved with otilimab 90 mg (16·2%; odds ratio [OR] 8·39, 95% CI 0·98-72·14; p=0·053). Adverse events were reported pre-escape in 19-24 (51-65%) patients and post escape in 10-17 (40-61%) patients across otilimab dose groups and in 18 (49%) of 37 and 22 (67%) of 33 in the placebo group. The most common adverse event was nasopharyngitis: 3-9 (8-24%) in otilimab groups and one (3%) in the placebo group pre-escape and 1-3 (4-10%) in otilimab groups and seven (21%) in the placebo group post escape. Pre-escape serious adverse events were foot fracture (otilimab 45 mg); arthralgia, myocardial infarction, dizziness (otilimab 90 mg); oesophageal spasm, acute pyelonephritis (otilimab 22·5 mg), and uterine leiomyoma (otilimab 135 mg). Post-escape serious adverse events were ankle fracture (placebo) and rheumatoid arthritis (otilimab 135 mg). There were no deaths or pulmonary events of clinical concern, and rates of serious infection were low.

INTERPRETATION

Otilimab plus methotrexate was well tolerated and, despite not achieving the primary endpoint of DAS28-CRP remission, there were improvements compared with placebo in disease activity scores. Of note, patients reported significant improvement in pain and physical function, supporting further clinical development of otilimab in rheumatoid arthritis.

FUNDING

GlaxoSmithKline.

Disentangling inflammatory from fibrotic disease activity by fibroblast activation protein imaging

OBJECTIVES

To date, there is no valuable tool to assess fibrotic disease activity in humans in vivo in a non-invasive way. This study aims to uncouple inflammatory from fibrotic disease activity in fibroinflammatory diseases such as IgG4-related disease.

METHODS

In this cross-sectional clinical study, 27 patients with inflammatory, fibrotic and overlapping manifestations of IgG4-related disease underwent positron emission tomography (PET) scanning with tracers specific for fibroblast activation protein (FAP; 68Ga-FAP inhibitor (FAPI)-04), 18F-fluorodeoxyglucose (FDG), MRI and histopathological assessment. In a longitudinal approach, 18F-FDG and 68Ga-FAPI-04 PET/CT data were evaluated before and after immunosuppressive treatment and correlated to clinical and MRI data.

RESULTS

Using combination of 68Ga-FAPI-04 and 18F-FDG-PET, we demonstrate that non-invasive functional tracking of IgG4-related disease evolution from inflammatory towards a fibrotic outcome becomes feasible. 18F-FDG-PET positive lesions showed dense lymphoplasmacytic infiltration of IgG4+ cells in histology, while 68Ga-FAPI-04 PET positive lesions showed abundant activated fibroblasts expressing FAP according to results from RNA-sequencing of activated fibroblasts. The responsiveness of fibrotic lesions to anti-inflammatory treatment was far less pronounced than that of inflammatory lesions.

CONCLUSION

FAP-specific PET/CT permits the discrimination between inflammatory and fibrotic activity in IgG4-related disease. This finding may profoundly change the management of certain forms of immune-mediated disease, such as IgG4-related disease, as subtypes dominated by fibrosis may require different approaches to control disease progression, for example, specific antifibrotic agents rather than broad spectrum anti-inflammatory treatments such as glucocorticoids.

Contrasting contributions of TNF from distinct cellular sources in arthritis

OBJECTIVES

Neutralisation of tumour necrosis factor (TNF) is widely used as a therapy for rheumatoid arthritis (RA). However, this therapy is only effective in less than a half of patients and is associated with several side effects. We hypothesised that TNF may possess non-redundant protective and immunomodulatory functions in vivo that cannot be blocked without a cost. The present work aimed to identify cellular sources of protective and pathogenic TNF, and its molecular forms during autoimmune arthritis.

METHODS

Mice lacking TNF expression by distinct cell types, such as myeloid cells and T or B lymphocytes, were subjected to collagen-induced arthritis (CIA) and collagen antibody-induced arthritis. Mice lacking soluble TNF production were also employed. The severity and incidence of the disease, as well as humoral and cellular responses were assessed.

RESULTS

Myeloid cell-derived TNF contributes to both induction and pathogenesis of autoimmune arthritis. Conversely, T cell-derived TNF is protective during the induction phase of arthritis via limiting of interleukin-12 production by dendritic cells and by subsequent control of autoreactive memory T cell development, but is dispensable during the effector phase of arthritis. B cell-derived TNF mediates severity of CIA via control of pathogenic autoantibody production.

CONCLUSIONS

Distinct TNF-producing cell types may modulate disease development through different mechanisms, suggesting that in arthritis TNF ablation from restricted cellular sources, such as myeloid cells, while preserving protective TNF functions from other cell types may be superior to pan-anti-TNF therapy.

ASP5094, a humanized monoclonal antibody against integrin alpha-9, did not show efficacy in patients with rheumatoid arthritis refractory to methotrexate: results from a phase 2a, randomized, double-blind, placebo-controlled trial

Background

Rheumatoid arthritis (RA) is a chronic, debilitating autoimmune condition characterized by joint synovial inflammation. Current treatments include methotrexate (MTX), biologic agents, and Janus kinase (JAK) inhibitors. However, these agents are not efficacious in all patients and there are concerns regarding side effects and risk of infection as these treatments target immune-related pathways. Overexpression and activation of integrin alpha-9 (α9) on fibroblast-like synoviocytes are associated with RA disease onset and exacerbation. The humanized immunoglobulin G1 monoclonal antibody ASP5094 was designed to inhibit human α9 and is currently under investigation for the treatment of RA.

Methods

This phase 2a, multicenter, randomized, placebo-controlled, double-blind, parallel-group study (NCT03257852) evaluated the efficacy, safety, and biological activity of intravenous ASP5094 10 mg/kg in patients with moderate to severe RA that was refractory to MTX. Patients received ASP5094 or placebo every 4 weeks for a total of three administrations. Both treatment groups used concomitant MTX. The primary efficacy endpoint was the proportion of patients who responded per American College of Rheumatology 50% improvement using C-reactive protein (ACR50-CRP) after 12 weeks of treatment. Biological activity of ASP5094 was assessed via pharmacokinetics and pharmacodynamics of known downstream effectors of α9. Safety was also assessed.

Results

Sixty-six patients were enrolled and randomized to placebo (n = 33) or ASP5094 (n = 33). In the primary efficacy analysis, ACR50-CRP response rates were 6.3% and 18.2% at week 12 in the ASP5094 and placebo groups, respectively; a difference of − 11.9, which was not significant (2-sided P value = 0.258). No trends in ACR50 response rates were observed in subgroups based on demographics or baseline disease characteristics, and no significant differences between placebo and ASP5094 were identified in secondary efficacy or pharmacodynamic endpoints, despite achievement of target serum concentrations of ASP5094. Most treatment-emergent adverse events were mild to moderate in severity, and ASP5094 was considered safe and well tolerated overall.

Conclusion

Although no notable safety signals were observed in this study, ASP5094 was not efficacious in patients with moderate to severe RA with an inadequate response to MTX.

Trial registration

ClinicalTrials.gov, NCT03257852. Registered on 22 Aug. 2017

Antioxidant Carbon Nanoparticles Inhibit Fibroblast-Like Synoviocyte Invasiveness and Reduce Disease Severity in a Rat Model of Rheumatoid Arthritis

Reactive oxygen species have been involved in the pathogenesis of rheumatoid arthritis (RA). Our goal was to determine the effects of selectively scavenging superoxide (O2•-) and hydroxyl radicals with antioxidant nanoparticles, called poly(ethylene glycol)-functionalized hydrophilic carbon clusters (PEG-HCCs), on the pathogenic functions of fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA) and on the progression of an animal model of RA. We used human FLS from patients with RA to determine PEG-HCC internalization and effects on FLS cytotoxicity, invasiveness, proliferation, and production of proteases. We used the pristane-induced arthritis (PIA) rat model of RA to assess the benefits of PEG-HCCs on reducing disease severity. PEG-HCCs were internalized by RA-FLS, reduced their intracellular O2•-, and reduced multiple measures of their pathogenicity in vitro, including proliferation and invasion. In PIA, PEG-HCCs caused a 65% reduction in disease severity, as measured by a standardized scoring system of paw inflammation and caused a significant reduction in bone and tissue damage, and circulating rheumatoid factor. PEG-HCCs did not induce lymphopenia during PIA. Our study demonstrated a role for O2•- and hydroxyl radicals in the pathogenesis of a rat model of RA and showed efficacy of PEG-HCCs in treating a rat model of RA.

T helper cells in synovial fluid of patients with rheumatoid arthritis primarily have a Th1 and a CXCR3+Th2 phenotype

Background

The majority of CD4⁺ T helper (Th) cells found in the synovial fluid (SF) of patients with rheumatoid arthritis (RA) express CXCR3, a receptor associated with Th1 cells. In blood, subsets of Th2 and Th17 cells also express CXCR3, but it is unknown if these cells are present in RA SF or how cytokines from these subsets affect cytokine/chemokine secretion by fibroblast-like synoviocytes (FLS) from patients with RA.

Methods

We examined the proportions of Th1, Th2, CXCR3⁺Th2, Th17, CXCR3⁺Th17, Th1Th17, peripheral T helper (TPh) and T follicular helper (TFh) cells in paired SF and blood, as well as the phenotype of TPh and TFh cells in RA SF (n = 8), by the use of flow cytometry. We also examined the cytokine/chemokine profile in paired SF and plasma (n = 8) and in culture supernatants of FLS from patients with chronic RA (n = 7) stimulated with Th-associated cytokines, by the use of cytometric bead arrays and ELISA. Cytokine receptor expression in FLS (n = 3) were assessed by the use of RNA sequencing and qPCR.

Results

The proportions of Th1 and CXCR3⁺Th2 cells were higher in SF than in blood (P < 0.05). TPh and PD-1^highTFh in RA SF were primarily of a Th1 and a CXCR3⁺Th2 phenotype. Moreover, the levels of CXCL9, CXCL10, CCL20, CCL2, CXCL8, IL-6 and IL-10 were higher in SF than in plasma (P < 0.05). Lastly, IL-4, IL-13 and IL-17A induced RA FLS to secrete proinflammatory IL-6, CCL2, CXCL1 and CXCL8, while IFNγ mainly induced CXCL10.

Conclusion

These findings indicate that not only Th1 but also CXCR3⁺Th2 cells may have a pathogenic role in RA synovial inflammation.

Gene Expression Signatures of Synovial Fluid Multipotent Stromal Cells in Advanced Knee Osteoarthritis and Following Knee Joint Distraction

Osteoarthritis (OA) is the most common musculoskeletal disorder. Although joint replacement remains the standard of care for knee OA patients, knee joint distraction (KJD), which works by temporarily off-loading the joint for 6–8 weeks, is becoming a novel joint-sparing alternative for younger OA sufferers. The biological mechanisms behind KJD structural improvements remain poorly understood but likely involve joint-resident regenerative cells including multipotent stromal cells (MSCs). In this study, we hypothesized that KJD leads to beneficial cartilage-anabolic and anti-catabolic changes in joint-resident MSCs and investigated gene expression profiles of synovial fluid (SF) MSCs following KJD as compared with baseline. To obtain further insights into the effects of local biomechanics on MSCs present in late OA joints, SF MSC gene expression was studied in a separate OA arthroplasty cohort and compared with subchondral bone (SB) MSCs from medial (more loaded) and lateral (less loaded) femoral condyles from the same joints. In OA arthroplasty cohort (n = 12 patients), SF MSCs expressed lower levels of ossification- and hypotrophy-related genes [bone sialoprotein (IBSP), parathyroid hormone 1 receptor (PTH1R), and runt-related transcription factor 2 (RUNX2)] than did SB MSCs. Interestingly, SF MSCs expressed 5- to 50-fold higher levels of transcripts for classical extracellular matrix turnover molecules matrix metalloproteinase 1 (MMP1), a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5), and tissue inhibitor of metalloproteinase-3 (TIMP3), all (p < 0.05) potentially indicating greater cartilage remodeling ability of OA SF MSCs, compared with SB MSCs. In KJD cohort (n = 9 patients), joint off-loading resulted in sustained, significant increase in SF MSC colonies’ sizes and densities and a notable transcript upregulation of key cartilage core protein aggrecan (ACAN) (weeks 3 and 6), as well as reduction in pro-inflammatory C–C motif chemokine ligand 2 (CCL2) expression (weeks 3 and 6). Additionally, early KJD changes (week 3) were marked by significant increases in MSC chondrogenic commitment markers gremlin 1 (GREM1) and growth differentiation factor 5 (GDF5). In combination, our results reveal distinct transcriptomes on joint-resident MSCs from different biomechanical environments and show that 6-week joint off-loading leads to transcriptional changes in SF MSCs that may be beneficial for cartilage regeneration. Biomechanical factors should be certainly considered in the development of novel MSC-based therapies for OA.

Applying precision medicine to unmet clinical needs in psoriatic disease

Psoriatic disease (PsD) is a heterogeneous condition that can affect peripheral and axial joints (arthritis), entheses, skin (psoriasis) and other structures. Over the past decade, considerable advances have been made both in our understanding of the pathogenesis of PsD and in the treatment of its diverse manifestations. However, several major areas of continued unmet need in the care of patients with PsD have been identified. One of these areas is the prediction of poor outcome, notably radiographic outcome in patients with psoriatic arthritis, so that stratified medicine approaches can be taken; another is predicting response to the numerous current and emerging therapies for PsD, so that precision medicine can be applied to rapidly improve clinical outcome and reduce the risk of toxicity. In order to address these needs, novel approaches, including imaging, tissue analysis and the application of proteogenomic technologies, are proposed as methodological solutions that will assist the dissection of the critical immune-metabolic pathways in this complex disease. Learning from advances made in other inflammatory diseases, it is time to address these unmet needs in a multi-centre partnership aimed at improving short-term and long-term outcomes for patients with PsD.

Induced, but not natural, regulatory T cells retain phenotype and function following exposure to inflamed synovial fibroblasts

Aberrant number and/or dysfunction of CD4⁺Foxp3⁺ Regulatory T cells (T_regs) are associated with the pathogenesis of rheumatoid arthritis (RA). A previous study has demonstrated that thymus-derived, natural T_regs (nT_regs) prefer to accumulate in inflamed joints and transdifferentiate to T_H17 cells under the stimulation of inflamed synovial fibroblasts (SFs). In this study, we made a head-to-head comparison of both T_reg subsets and demonstrated that induced T_regs (iT_regs), but not nT_regs, retained Foxp3 expression and regulatory function on T effector cells (T_effs) after being primed with inflamed SFs. In addition, iT_regs inhibited proliferation, inflammatory cytokine production, migration, and invasion ability of collagen-induced arthritis (CIA)-SFs in vitro and in vivo. Moreover, we noted that iT_regs directly targeted inflamed SFs to treat autoimmune arthritis, while nT_regs failed to do this. Thus, manipulation of the iT_reg subset may have a greater potential for prevention or treatment of patients with RA.

Adipocytic Progenitor Cells Give Rise to Pathogenic Myofibroblasts: Adipocyte-to-Mesenchymal Transition and Its Emerging Role in Fibrosis in Multiple Organs

Purpose of Review

Adipocytes have recently been shown to be able to reprogram to a myofibroblastic phenotype in a process termed adipocyte mesenchymal transition (AMT). This review seeks to discuss the relevance of this process to disease and explore its mechanisms.

Recent Findings

AMT occurs in multiple organs and diseases, transdifferentiation goes through a precursor cell and there is a reversible process that can be influenced by metabolic stress, myeloid cells, immune dysregulation, and pharmacological intervention.

Summary

AMT is a newly appreciated and highly relevant process in multiple forms of fibrosis. Targeting AMT may serve as a novel method of treating fibrosis.