A Snap Shot of Complement Gene Expression and Presence of Complement Proteins in Synovial Biopsies from Early Rheumatoid Arthritis Patients

The etiology of rheumatoid arthritis (RA) is unknown. Previous studies of mouse models of RA have strongly implicated the alternative and lectin pathways of the complement system in disease pathogenesis. Here we explored the Pathobiology of Early Arthritis Cohort (PEAC) tissue RNA sequencing (RNA-seq) database and identify correlations among complement gene expression, Fc receptor expression and clinical severity, measured as disease activity score 28 - erythrocyte sendimentation rate (DAS28-ESR), in both blood and synovium. We also evaluated the biodistribution of complement activation pathway proteins and inhibitors using Multispectral ImmunoHistoChemical (MIHC) staining. Ultrasound guided synovial biopsies (n = 23), obtained from Accelerating Medicines Partnership (AMP) studies, were subjected to MIHC for various complement proteins. Our analyses revealed that in the synovium, but not in blood, significant positive correlations existed between complement gene expression and DAS28-ESR for C2, CFB, FCN1, C3AR1, C5AR1, and CR1. Surprisingly, levels of MASP1, Colec12, C5 and C6 RNA inversely correlated with baseline DAS28-ESR. After 6 months therapy, baseline CFHR4 positively correlated with delta DAS28-ESR. In the synovium, there were also significant positive correlations between DAS28-ESR and FcγR1A, FcγR1B, FcγR2A and FcγR3A. In early RA (ERA) synovium, a significantly (p < 0.05) higher levels of cells expressed CFH compared with CFB and CFHR4. We also found regional imbalance between C3 and CFH in ERA synovial biopsies. ERA synovial biopsies implicate the complement system in early disease and reveal intriguing differences among factors in clinical relevance, outcome and localized tissue dysregulation.

Supported by R01AR51749-16

MCTR3 reprograms arthritic monocytes to upregulate Arginase-1 and exert pro-resolving and tissue-protective functions in experimental arthritis

BACKGROUND

Rheumatoid arthritis (RA) is a progressive degenerative disorder that leads to joint destruction. Available treatments only target the inflammatory component with minimal impact on joint repair. We recently uncovered a previously unappreciated family of pro-resolving mediators, the maresin conjugate in tissue regeneration (MCTR), that display both immunoregulatory and tissue-protective activities. Thus, we queried whether the production of these autacoids is disrupted in RA patients and whether they can be useful in treating joint inflammation and promoting joint repair.

METHODS

Using a highly phenotyped RA cohort we evaluated plasma MCTR concentrations and correlated these to clinical markers of disease activity. To evaluate the immunoregulatory and tissue reparative activities we employed both in vivo models of arthritis and organ culture models.

FINDINGS

Herein, we observed that plasma MCTR3 concentrations were negatively correlated with joint disease activity and severity in RA patients. Evaluation of the mechanisms engaged by this mediator in arthritic mice demonstrated that MCTR3 reprograms monocytes to confer enduring joint protective properties. Single cell transcriptomic profiling and flow cytometric evaluation of macrophages from mice treated with MCTR3-reprogrammed monocytes revealed a role for Arginase-1 (Arg-1) in mediating their joint reparative and pro-resolving activities. Arg-1 inhibition reversed both the anti-arthritic and tissue reparative actions of MCTR3-reprogrammed monocytes.

INTERPRETATION

Our findings demonstrate that circulating MCTR3 levels are negatively correlated with disease in RA. When administered to mice in vivo, MCTR3 displayed both anti-inflammatory and joint reparative activities, protecting both cartilage and bone in murine arthritis. These activities were, at least in part, mediated via the reprogramming of mononuclear phagocyte responses.

FUNDING

This work was supported by funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant no: 677542) and the Barts Charity (grant no: MGU0343) to J.D. J.D. is also supported by a Sir Henry Dale Fellowship jointly funded by the Wellcome Trust and the Royal Society (grant 107613/Z/15/Z).

EULAR points to consider for minimal reporting requirements in synovial tissue research in rheumatology

BACKGROUND

Synovial tissue research has become widely developed in several rheumatology centres, however, large discrepancies exist in the way synovial tissue is handled and, more specifically, how data pertaining to biopsy procedure, quality check and experimental results are reported in the literature. This heterogeneity hampers the progress of research in this rapidly expanding field. In that context, under the umbrella of European Alliance of Associations for Rheumatology, we aimed at proposing points to consider (PtC) for minimal reporting requirements in synovial tissue research.

METHODS

Twenty-five members from 10 countries across Europe and USA met virtually to define the key areas needing evaluation and formulating the research questions to inform a systematic literature review (SLR). The results were presented during a second virtual meeting where PtC were formulated and agreed.

RESULTS

Study design, biopsy procedures, tissue handling, tissue quality control and tissue outcomes (imaging, DNA/RNA analysis and disaggregation) were identified as important aspects for the quality of synovial tissue research. The SLR interrogated four databases, retrieved 7654 abstracts and included 26 manuscripts. Three OPs and nine PtC were formulated covering the following areas: description of biopsy procedure, overarching clinical design, patient characteristics, tissue handling and processing, quality control, histopathology, transcriptomic analyses and single-cell technologies.

CONCLUSIONS

These PtC provide guidance on how research involving synovial tissue should be reported to ensure a better evaluation of results by readers, reviewers and the broader scientific community. We anticipate that these PtC will enable the field to progress in a robust and transparent manner over the coming years.

The role of lymphoid tissue SPARC in the pathogenesis and response to treatment of multiple myeloma

Background

Despite the significant progress in the treatment of multiple myeloma (MM), the disease remains untreatable and its cure is still an unmet clinical need. Neoplastic transformation in MM is initiated in the germinal centers (GCs) of secondary lymphoid tissue (SLT) where B cells experience extensive somatic hypermutation induced by follicular dendritic cells (FDCs) and T-cell signals.

Objective

We reason that secreted protein acidic and rich in cysteine (SPARC), a common stromal motif expressed by FDCs at the origin (SLTs) and the destination (BM) of MM, plays a role in the pathogenesis of MM, and, here, we sought to investigate this role.

Methods

There were 107 BM biopsies from 57 MM patients (taken at different time points) together with 13 control specimens assessed for SPARC gene and protein expression and compared with tonsillar tissues. In addition, regulation of myeloma-promoting genes by SPARC-secreting FDCs was assessed in in vitro GC reactions (GCRs).

Results

SPARC gene expression was confirmed in both human primary (BM) and secondary (tonsils) lymphoid tissues, and the expression was significantly higher in the BM. Sparc was detectable in the BM and tonsillar lysates, co-localized with the FDC markers in both tissues, and stimulation of FDCs in vitro induced significantly higher levels of SPARC expression than unstimulated controls. In addition, SPARC inversely correlated with BM PC infiltration, ISS staging, and ECOG performance of the MM patients, and in vitro addition of FDCs to lymphocytes inhibited the expression of several oncogenes associated with malignant transformation of PCs.

Conclusion

FDC-SPARC inhibits several myelomagenic gene expression and inversely correlates with PC infiltration and MM progression. Therapeutic induction of SPARC expression through combinations of the current MM drugs, repositioning of non-MM drugs, or novel drug discovery could pave the way to better control MM in clinically severe and drug-resistant patients.

Role of synovial fibroblast subsets across synovial pathotypes in rheumatoid arthritis: a deconvolution analysis

OBJECTIVES

To integrate published single-cell RNA sequencing (scRNA-seq) data and assess the contribution of synovial fibroblast (SF) subsets to synovial pathotypes and respective clinical characteristics in treatment-naïve early arthritis.

METHODS

In this in silico study, we integrated scRNA-seq data from published studies with additional unpublished in-house data. Standard Seurat, Harmony and Liger workflow was performed for integration and differential gene expression analysis. We estimated single cell type proportions in bulk RNA-seq data (deconvolution) from synovial tissue from 87 treatment-naïve early arthritis patients in the Pathobiology of Early Arthritis Cohort using MuSiC. SF proportions across synovial pathotypes (fibroid, lymphoid and myeloid) and relationship of disease activity measurements across different synovial pathotypes were assessed.

RESULTS

We identified four SF clusters with respective marker genes: PRG4+ SF (CD55, MMP3, PRG4, THY1neg ); CXCL12+ SF (CXCL12, CCL2, ADAMTS1, THY1low ); POSTN+ SF (POSTN, collagen genes, THY1); CXCL14+ SF (CXCL14, C3, CD34, ASPN, THY1) that correspond to lining (PRG4+ SF) and sublining (CXCL12+ SF, POSTN+ + and CXCL14+ SF) SF subsets. CXCL12+ SF and POSTN+ + were most prominent in the fibroid while PRG4+ SF appeared highest in the myeloid pathotype. Corresponding, lining assessed by histology (assessed by Krenn-Score) was thicker in the myeloid, but also in the lymphoid pathotype + the fibroid pathotype. PRG4+ SF correlated positively with disease severity parameters in the fibroid, POSTN+ SF in the lymphoid pathotype whereas CXCL14+ SF showed negative association with disease severity in all pathotypes.

CONCLUSION

This study shows a so far unexplored association between distinct synovial pathologies and SF subtypes defined by scRNA-seq. The knowledge of the diverse interplay of SF with immune cells will advance opportunities for tailored targeted treatments.

Follicular dendritic cell differentiation is associated with distinct synovial pathotype signatures in rheumatoid arthritis

Follicular dendritic cells (FDCs) fundamentally contribute to the formation of synovial ectopic lymphoid-like structures in rheumatoid arthritis (RA) which is associated with poor clinical prognosis. Despite this critical role, regulation of FDC development in the RA synovium and its correlation with synovial pathotype differentiation remained largely unknown. Here, we demonstrate that CNA.42⁺ FDCs distinctively express the pericyte/fibroblast-associated markers PDGFR-β, NG2, and Thy-1 in the synovial perivascular space but not in established follicles. In addition, synovial RNA-Seq analysis revealed that expression of the perivascular FDC markers was strongly correlated with PDGF-BB and fibroid synovitis, whereas TNF-α/LT-β was significantly associated with lymphoid synovitis and expression of CR1, CR2, and FcγRIIB characteristic of mature FDCs in lymphoid follicles. Moreover, PDGF-BB induced CNA.42⁺ FDC differentiation and CXCL13 secretion from NG2⁺ synovial pericytes, and together with TNF-α/LT-β conversely regulated early and late FDC differentiation genes in unsorted RA synovial fibroblasts (RASF) and this was confirmed in flow sorted stromal cell subsets. Furthermore, RASF TNF-αR expression was upregulated by TNF-α/LT-β and PDGF-BB; and TNF-α/LT-β-activated RASF retained ICs and induced B cell activation in in vitro germinal center reactions typical of FDCs. Additionally, FDCs trapped peptidyl citrulline, and strongly correlated with IL-6 expression, and plasma cell, B cell, and T cell infiltration of the RA synovium. Moreover, synovial FDCs were significantly associated with RA disease activity and radiographic features of tissue damage. To the best of our knowledge, this is the first report describing the reciprocal interaction between PDGF-BB and TNF-α/LT-β in synovial FDC development and evolution of RA histological pathotypes. Selective targeting of this interplay could inhibit FDC differentiation and potentially ameliorate RA in clinically severe and drug-resistant patients.

Galectin-9 mediates neutrophil capture and adhesion in a CD44 and β2 integrin-dependent manner

Neutrophil trafficking is a key component of the inflammatory response. Here, we have investigated the role of the immunomodulatory lectin Galectin-9 (Gal-9) on neutrophil recruitment. Our data indicate that Gal-9 is upregulated in the inflamed vasculature of RA synovial biopsies and report the release of Gal-9 into the extracellular environment following endothelial cell activation. siRNA knockdown of endothelial Gal-9 resulted in reduced neutrophil adhesion and neutrophil recruitment was significantly reduced in Gal-9 knockout mice in a model of zymosan-induced peritonitis. We also provide evidence for Gal-9 binding sites on human neutrophils; Gal-9 binding induced neutrophil activation (increased expression of β2 integrins and reduced expression of CD62L). Intra-vital microscopy confirmed a pro-recruitment role for Gal-9, with increased numbers of transmigrated neutrophils following Gal-9 administration. We studied the role of both soluble and immobilized Gal-9 on human neutrophil recruitment. Soluble Gal-9 significantly strengthened the interaction between neutrophils and the endothelium and inhibited neutrophil crawling on ICAM-1. When immobilized, Gal-9 functioned as an adhesion molecule and captured neutrophils from the flow. Neutrophils adherent to Gal-9 exhibited a spread/activated phenotype that was inhibited by CD18 and CD44 neutralizing antibodies, suggesting a role for these molecules in the pro-adhesive effects of Gal-9. Our data indicate that Gal-9 is expressed and released by the activated endothelium and functions both in soluble form and when immobilized as a neutrophil adhesion molecule. This study paves the way for further investigation of the role of Gal-9 in leukocyte recruitment in different inflammatory settings.

Cellular and molecular diversity in Rheumatoid Arthritis

Rheumatoid Arthritis (RA) is a chronic systemic autoimmune disease. RA mainly affects synovial joints, with inflammation of the synovial membrane (synovitis), characterised by neo-angiogenesis, hyperplasia of lining layer, and immune cell infiltration that drive local inflammation and, if untreated, can lead to joint destruction and disability. In parallel to the well-known clinical heterogeneity, the underlying synovitis can also be significantly heterogeneous, both at cellular and molecular level, which can at least in part explain why despite the availability of highly effective treatment options, a large proportion of patients are resistant to some individual treatments. The assimilation of recent high-throughput data from analysis at the single-cell level with rigorous and high-quality clinical outcomes obtained from large randomised clinical trials support the definition of disease and treatment response endotypes. Looking ahead, the integration of histological and molecular signatures from the diseased tissue into clinical algorithms may help decision making in the management of patients with Rheumatoid Arthritis in clinical practice.

Stepwise changes in the murine salivary gland immune response during virally-induced ectopic lymphoid structure formation

OBJECTIVES

Sjögren's syndrome (SS) is a chronic autoimmune disease characterised by lymphocytic infiltration into the salivary glands (SG) and, in a subset of patients, formation of ectopic lymphoid structures (ELS) in the glands. However, the mechanisms of how ELS form ectopically are not fully elucidated. Here we used a viral inducible murine model of ELS formation in the SG to elucidate the key immunological steps regulating the formation of ELS in the SG.

METHODS

We have utilised an inducible murine model of sialadenitis whereby retrograde cannulation of the submandibular SG with a replication-deficient adenovirus 5 leads to the formation of ELS. Flow cytometry, immunofluorescence and gene expression was performed on the SGs at regular time points after cannulation to follow the organisation of ELS.

RESULTS

Innate immune cells (neutrophils, eosinophils and monocytes) rapidly infiltrated the SG by 3 days post cannulation (dpc) whereby monocytes started to differentiate into resident macrophages. Myeloid dendritic cells accumulated inside leukocytic aggregates whereas macrophages were excluded from the developing ELS. Meanwhile, CD11b+ cells upregulated Il18, Cxcl13, Ltb, April and other lymphoid genes stimulating the influx of T cells by 12 days and B cells shortly after. Infiltration of T-follicular helper (Tfh) cells correlated with an increase in GL7+ germinal centre B cells, which peaked at 19 dpc.

CONCLUSIONS

Immune cell infiltration in virally-infected murine SG follows a highly reproducible step-wise process whereby early innate immune cells reshape the SG myeloid compartment leading to upregulation of genes involved in the ectopic lymphoid neogenesis process. This in turns leads to T and B cell recruitment, differentiation and activation, culminating in the organization of ELS and localised germinal centres responses.

NKp30 Receptor Upregulation in Salivary Glands of Sjögren's Syndrome Characterizes Ectopic Lymphoid Structures and Is Restricted by Rituximab Treatment

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease resulting from the inflammatory infiltration of exocrine glands, mainly salivary and lacrimal glands, leading to secretory dysfunction and serious complications including debilitating fatigue, systemic autoimmunity, and lymphoma. Like other autoimmune disorders, a strong interferon (IFN) signature is present among subsets of pSS patients, suggesting the involvement of innate immunity in pSS pathogenesis. NCR3/NKp30 is a natural killer (NK) cell-specific activating receptor regulating the cross talk between NK and dendritic cells including type II IFN secretion upon NK-cell activation. A genetic association between single-nucleotide polymorphisms (SNPs) in the NCR3/NKp30 promoter gene and a higher susceptibility for pSS has been previously described, with pSS patients most frequently carrying the major allele variant associated with a higher NKp30 transcript and IFN-γ release as a consequence of the receptor engagement. In the present study, we combined RNA-sequencing and histology from pSS salivary gland biopsies to better characterize NKp30 (NCR3) and its ligand B7/H6 (NCR3LG1) in pSS salivary gland tissues. Levels of NCR3/NKp30 were significantly increased both in salivary glands and in circulating NK cells of pSS patients compared with sicca controls, especially in salivary glands with organized ectopic lymphoid structures. In line with this observation, a strong correlation between NCR3/NKp30 levels and salivary gland infiltrating immune cells (CD3, CD20) was found. Furthermore, NCR3/NKp30 levels also correlated with higher IFN-γ, Perforin, and Granzyme-B expression in pSS SGs with organized ectopic lymphoid structures, suggesting an activation state of NK cells infiltrating SG tissue. Of note, NKp30+ NK cells accumulated at the border of the inflammatory foci, while the NKp30 ligand, B7/H6, is shown to be expressed mainly by ductal epithelial cells in pSS salivary glands. Finally, immunomodulatory treatment, such as the B-cell depleting agent rituximab, known to reduce the infiltration of immune cells in pSS SGs, prevented the upregulation of NCR3/NKp30 within the glands.

Robust optimization of SWATH-MS workflow for human blood serum proteome analysis using a quality by design approach

Background

It is not enough to optimize proteomics assays. It is critical those assays are robust to operating conditions. Without robust assays, proteomic biomarkers are unlikely to translate readily into the clinic. This study outlines a structured approach to the identification of a robust operating window for proteomics assays and applies that method to Sequential Window Acquisition of all Theoretical Spectra Mass Spectroscopy (SWATH-MS).

Methods

We used a sequential quality by design approach exploiting a fractional screening design to first identify critical SWATH-MS parameters, then using response surface methods to identify a robust operating window with good reproducibility, before validating those settings in a separate validation study.

Results

The screening experiment identified two critical SWATH-MS parameters. We modelled the number of proteins and reproducibility as a function of those parameters identifying an operating window permitting robust maximization of the number of proteins quantified in human serum. In a separate validation study, these settings were shown to give good proteome-wide coverage and high quantification reproducibility.

Conclusions

Using design of experiments permits identification of a robust operating window for SWATH-MS. The method gives a good understanding of proteomics assays and greater data-driven confidence in SWATH-MS performance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12014-021-09323-z.

Circulating and Synovial Pentraxin-3 (PTX3) Expression Levels Correlate With Rheumatoid Arthritis Severity and Tissue Infiltration Independently of Conventional Treatments Response

Aims

To determine the relationship between PTX3 systemic and synovial levels and the clinical features of rheumatoid arthritis (RA) in a cohort of early, treatment naïve patients and to explore the relevance of PTX3 expression in predicting response to conventional-synthetic (cs) Disease-Modifying-Anti-Rheumatic-Drugs (DMARDs) treatment.

Methods

PTX3 expression was analyzed in 119 baseline serum samples from early naïve RA patients, 95 paired samples obtained 6-months following the initiation of cs-DMARDs treatment and 43 healthy donors. RNA-sequencing analysis and immunohistochemistry for PTX3 were performed on a subpopulation of 79 and 58 synovial samples, respectively, to assess PTX3 gene and protein expression. Immunofluorescence staining was performed to characterize PTX3 expressing cells within the synovium.

Results

Circulating levels of PTX3 were significantly higher in early RA compared to healthy donors and correlated with disease activity at baseline and with the degree of structural damages at 12-months. Six-months after commencing cs-DMARDs, a high level of PTX3, proportional to the baseline value, was still detectable in the serum of patients, regardless of their response status. RNA-seq analysis confirmed that synovial transcript levels of PTX3 correlated with disease activity and the presence of mediators of inflammation, tissue remodeling and bone destruction at baseline. PTX3 expression in the synovium was strongly linked to the degree of immune cell infiltration, the presence of ectopic lymphoid structures and seropositivity for autoantibodies. Accordingly, PTX3 was found to be expressed by numerous synovial cell types such as plasma cells, fibroblasts, vascular and lymphatic endothelial cells, macrophages, and neutrophils. The percentage of PTX3-positive synovial cells, although significantly reduced at 6-months post-treatment as a result of global decreased cellularity, was similar in cs-DMARDs responders and non-responders.

Conclusion

This study demonstrates that, early in the disease and prior to treatment modification, the level of circulating PTX3 is a reliable marker of RA activity and predicts a high degree of structural damages at 12-months. In the joint, PTX3 associates with immune cell infiltration and the presence of ectopic lymphoid structures. High synovial and peripheral blood levels of PTX3 are associated with chronic inflammation characteristic of RA. Additional studies to determine the mechanistic link are required.

ROR2 blockade as a therapy for osteoarthritis

Osteoarthritis is characterized by the loss of the articular cartilage, bone remodeling, pain, and disability. No pharmacological intervention can currently halt progression of osteoarthritis. Here, we show that blocking receptor tyrosine kinase-like orphan receptor 2 (ROR2) improves cartilage integrity and pain in osteoarthritis models by inhibiting yes-associated protein (YAP) signaling. ROR2 was up-regulated in the cartilage in response to inflammatory cytokines and mechanical stress. The main ligand for ROR2, WNT5A, and the targets YAP and connective tissue growth factor were up-regulated in osteoarthritis in humans. In vitro, ROR2 overexpression inhibited chondrocytic differentiation. Conversely, ROR2 blockade triggered chondrogenic differentiation of C3H10T¹/₂ cells and suppressed the expression of the cartilage-degrading enzymes a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5. The chondrogenic effect of ROR2 blockade in the cartilage was independent of WNT signaling and was mediated by down-regulation of YAP signaling. ROR2 signaling induced G protein and Rho-dependent nuclear accumulation of YAP, and YAP inhibition was required but not sufficient for ROR2 blockade-induced chondrogenesis. ROR2 silencing protected mice from instability-induced osteoarthritis with improved structural outcomes, sustained pain relief, and without apparent side effects or organ toxicity. Last, ROR2 silencing in human articular chondrocytes transplanted in nude mice led to the formation of cartilage organoids with more and better differentiated extracellular matrix, suggesting that the anabolic effect of ROR2 blockade is conserved in humans. Thus, ROR2 blockade is efficacious and well tolerated in preclinical animal models of osteoarthritis.

AB0039 AGRIN REPAIRS BONE AND CARTILAGE IN VIVO

Background:

Cartilage defects in the joints are reported in 61% of all arthroscopies1&2. The size of the cartilage repair market is estimated to be $2.195 million by 20253. Cartilage defects can evolve into osteoarthritis, in which abnormal load results in cartilage breakdown, joint pain and reduced mobility. Osteoarthritis is the leading cause of permanent disability and absenteeism and affects up to 1/3 of the people over 60yrs. In western countries osteoarthritis costs 1.5-2% of the GDP4. Joint replacement with a prosthesis restores some degree of independence but in up to 20% of patients it does not meet expectations 5 and has a limited life span. There is no pharmacological intervention that arrests or reverts the course of osteoarthritis, despite the desperate need.

We previously published that agrin plays an important role in cartilage homeostasis6. The addition of agrin to chondrocytes in vivo resulted in enhanced cartilage formation, suggesting a potential role for agrin in cartilage repair.

Objectives:

Investigate the potential of agrin for use in cartilage repair.

Methods:

Critical size osteochondral defects were generated in mice and sheep and injected intraarticularly with type I collagen gel containing agrin or vehicle. Animals were monitored for 8 weeks or 6 months respectively. MicroCT, histological analysis, qPCR, linage tracking, reporter assays, chondrogenesis assay, immunohistochemistry were performed.

Results:

A single intraarticular administration of agrin induced regeneration of critical-size osteochondral defects in mice, restoring the tissue architecture and bone-cartilage interface. Agrin stem cells to the site of injury and, through simultaneous activation of CREB and suppression of canonical WNT signalling, induced GDF5 expression and differentiation into stable articular chondrocytes, forming stable articular cartilage. In sheep, agrin treatment resulted in regeneration of bone and cartilage, which promoted increased ambulatory activity.

Conclusion:

Agrin orchestrates repair morphogenesis at the joint surface by modulating multiple signalling pathways, supporting the therapeutic use of agrin for joint surface regeneration.

References:

[1]Curl, W. W. et al. Cartilage injuries: a review of 31,516 knee arthroscopies. Arthrosc. J. Arthrosc. Relat. Surg. Off. Publ. Arthrosc. Assoc. N. Am. Int. Arthrosc. Assoc. 13, 456–460 (1997).

[2]Hjelle, K., Solheim, E., Strand, T., Muri, R. & Brittberg, M. Articular cartilage defects in 1,000 knee arthroscopies. Arthrosc. J. Arthrosc. Relat. Surg. Off. Publ. Arthrosc. Assoc. N. Am. Int. Arthrosc. Assoc. 18, 730–734 (2002).

[3]Cartilage Repair Market Size, Share, Industry Analysis 2018-2025 | AMR. Allied Market Research https://www.alliedmarketresearch.com/cartilage-repair-market.

[4]Hiligsmann, M. et al. Health economics in the field of osteoarthritis: an expert’s consensus paper from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO). Semin. Arthritis Rheum. 43, 303–313 (2013).

[5]Dieppe, P., Lim, K. & Lohmander, S. Who should have knee joint replacement surgery for osteoarthritis? Int. J. Rheum. Dis. 14, 175–180 (2011).

[6]Eldridge, S., et al. Agrin mediates chondrocyte homeostasis and requires both LRP4 and α-dystroglycan to enhance cartilage formation in vitro and in vivo. Annals of the rheumatic diseases 75 (6), 1228-1235 (2016).

Acknowledgements:

We thank the technical staff in the ARM Lab and Staff at the University of Aberdeen’s Animal Facility and Microscopy and Histology Facility for support. Funding: We gratefully acknowledge funding support of this work by the MRC (MR/L022893/1, MR/N010973/1,and MR/P026362/1), Versus Arthritis (19667, 21515, 20886, and 21621), Rosetrees Trust (A1205), the Medical College of St Bartholomew’s Hospital Trust, and the William Harvey Research Foundation.

Disclosure of Interests:

Suzanne Eldridge: None declared, Aida Barawi: None declared, Hui Wang: None declared, Anke Roelofs: None declared, Magdalena Kaneva: None declared, Zeyu Guan: None declared, Helen Lydon: None declared, Bethan Thomas: None declared, Anne-Sophie Thorup: None declared, Beatriz F Fernandez: None declared, Sara Caxaria: None declared, Danielle Strachan: None declared, Ahmed Ali: None declared, Kanatheepan Shanmuganathan: None declared, Costantino Pitzalis: None declared, James Whiteford: None declared, Fran Henson: None declared, Andrew McCaskie: None declared, Cosimo De Bari: None declared, Francesco Dell’Accio Consultant of: F.D. has received consultancy fees from Samumed and UCB.

OP0200 BLOCKING ROR2 IMPROVES CARTILAGE INTEGRITY AND PROVIDES PAIN RELIEF IN OSTEOARTHRITIS

Background:

Osteoarthritis (OA) is the leading cause of chronic disability worldwide, affecting 12% of the population, and yet we still do not have a disease-modifying treatment. Cartilage breakdown is the hallmark of OA, and patients suffer from pain and loss of joint function/independence, severely affecting quality of life. Therefore, there is a huge unmet clinical need.

Receptor tyrosine kinase–like orphan receptor 2 (ROR2) is a non-canonical WNT receptor that regulates the planar cell polarity pathway, controlling limb outgrowth during development. During skeletal development, chondrocytes require ROR2 to undergo hypertrophy throughout the process of endochondral bone formation1. Loss of function mutations in humans causes Recessive Robinow Syndrome, leading to limb shortening and brachydactyly2,3.

Although absent from healthy adult articular cartilage, our initial studies identified high expression levels of ROR2 in chondrocytes from patients with OA, suggesting a role in the disease process

Objectives:

To test the potential of ROR2 blockade as a disease-modifying treatment for OA.

Methods:

Human cartilage organoid model in nude mice, menisco-ligament injury (MLI) model of OA in mice, behavioural studies, in vitro studies in cells.

Results:

ROR2/WNT5A signaling was increased in osteoarthritic cartilage. Blocking ROR2 was sufficient to induce articular chondrogenesis and suppress expression of aggrecanases in a mesenchymal stem cell line, and to support cartilage formation in a human cartilage organoid model in nude mice using primary chondrocytes from patients with OA.

In the MLI model of OA, blocking ROR2 in therapeutic regime using atelocollagen-conjugated siRNA resulted in reduced cartilage destruction and in rapid and sustained pain relief. Due to the limited expression pattern of ROR2 in adulthood, no systemic or local toxicity were expected, nor were any observed4.

With the current technology, ROR2 blockade requires intra-articular (IA) injections of siRNA conjugated to atelocollagen every 5 days. Preliminary efficacy data of potentially longer-acting ROR2 blockers are promising.

The mechanism of action of ROR2 blockade was independent of modulation of canonical WNT signaling.

ROR2/WNT5A promoted nuclear localization of YAP, which required both Rho and G-proteins. YAP signaling downstream of ROR2 also required Rho, but not G-proteins. YAP and TEAD inhibition was required, but not sufficient, for the chondrogenic effect of blocking ROR2. Therefore, additional, yet unknown mechanisms must be involved downstream of ROR2.

Conclusion:

ROR2 blockade has potential as a disease-modifying treatment for OA, resulting in cartilage protection and rapid and sustained pain relief in a murine model. This will be crucial for clinical success of any treatment for OA and promote patient compliance.

Our current siRNA-atelocollagen based technology requires IA injections too frequently to be acceptable for patients. We are developing ROR2 blockade which can be administered systemically or IA not more often than every 3 months - work funded by FOREUM.

References:

[1]DeChiara, T. M. et al. Ror2, encoding a receptor-like tyrosine kinase, is required for cartilage and growth plate development. Nat. Genet.24, 271–4 (2000).

[2]Bokhoven, H. Van, Celli, J. & Kayserili, H. Mutation of the gene encoding the ROR2 tyrosine kinase causes autosomal recessive Robinow syndrome. Nature25, 423–426 (2000).

[3]Afzal, A., Rajab, A., Fenske, C. & Oldridge, M. Recessive Robinow syndrome, allelic to dominant brachydactyly type B, is caused by mutation of ROR2. Nature25, 419–422 (2000).

[4]Thorup, A.-S. et al. ROR2 blockade as a therapy for osteoarthritis. Sci. Transl. Med.12, eaax3063 (2020).

Acknowledgements:

We gratefully acknowledge funding support of this work by the Medical College of St Bartholomew’s Hospital Trust, the William Harvey Research Foundation, FOREUM foundation for research in rheumatology (1016807), the MRC (MR/L022893/1, MR/N010973/1, MR/P026362/1, MR/K013076/1), Versus Arthritis (21515, 20886, 21621, 20859), and the DFG Emmy-Noether program (BE4328/5-1).

Disclosure of Interests:

Anne-Sophie Thorup: None declared, Danielle Strachan: None declared, Sara Caxaria: None declared, Blandine Poulet: None declared, Bethan Thomas: None declared, Suzanne Eldridge: None declared, Giovanna Nalesso: None declared, James Whiteford: None declared, Costantino Pitzalis: None declared, Thomas Aigner: None declared, Roger Corder: None declared, Jessica Bertrand: None declared, Francesco Dell’Accio Consultant of: Samumed and UCB

POS0206 DESIGN AND CHARACTERISATION OF A THERAPEUTIC BISPECIFIC TANDEM scFv-Fc FUSION PROTEIN WITH ANTI-TNF AND SYNOVIUM-TARGETING SPECIFICITY FOR THE TREATMENT OF RHEUMATOID ARTHRITIS

Background:

Rheumatoid Arthritis (RA) is a systemic autoimmune disease with a prevalence of 0.5-1% worldwide1. Anti-cytokine antibodies, especially anti-Tumor Necrosis Factor (TNF) antibodies are considered the gold standard for RA therapy. However, there are some concerns regarding their lack of therapeutic efficacy in a significant proportion of patients2 and their potential systemic implications such as the risk of serious infections3. Developing novel agents with synovial targeting specificity might help to increase the therapeutic index while reducing systemic side effects of RA therapeutics.

Objectives:

Our work aims to develop a novel bispecific tandem single-chain variable fragment (scFv)-Fc fusion protein combining synovium specificity with anti-TNFα activity. The potential advantage of this construct is a reduced systemic TNF-binding activity and increase delivery and activation of the TNF-neutralising capacity at the inflamed joints.

Methods:

The therapeutic tandem scFv-Fc fusion protein comprises two external arms with synovium specific targeting ability linked through a metalloproteinase (MMP) cleavable linker to the anti-TNFα variable fragments of Adalimumab fused to the CH2 and CH3 domains of IgG1 (Figure 1). The external scFv regions with synovium specificity were previously identified by in vivo phage display using a SCID mouse model transplanted with human synovium4. The construct was tested for its ability to bind and neutralize in vitro and ex vivo targets.

Results:

The fusion protein was tested by immunohistochemistry staining on RA synovium biopsies and an array of non-inflamed human tissues showing specific targeting of synovial microvasculature without no reactivity to the non-inflamed tissues. The TNFα binding and blocking capacity of the fusion protein was measured respectively by ELISA and cell assays measuring NF-κB activation, and it showed a two-fold decreased activity compared to the control antibody Adalimumab prior to detachment of the cleavable targeting fragment shielding the active anti-TNF fragment. Human synovial fluid and recombinant human MMP-1 efficiently cleaved the external arms of the antibody, releasing the anti-TNF scFv-Fc. The cleaved construct, detached from the synovium targeting arms, showed the same binding and anti-TNF inhibitory capacity/potency as Adalimumab.

Conclusion:

The novel bispecific tandem scFv-Fc demonstrated specific synovium targeting ability and intended reduced anti-TNF activity in its intact form prior to reaching the joint. Following MMPs-induced cleavage present in RA synovial fluid the therapeutic activity was restored to the same level as Adalimumab. Overall, this construct has the potential of decreasing the anti-TNF off-site activity and consequently, reduce systemic toxicity while maintaining high on-site activity. Also, the presence of a synovium targeting domain has the advantage of increasing the delivery and retention within the inflamed synovium and possibly increase the therapeutic index of this anti-TNF therapeutics.

Figure 1.

Schematic diagram of the bispecific tandem scFv-Fc fusion protein.

References:

[1]Silman, A. J. & Pearson, J. E. Epidemiology and genetics of rheumatoid arthritis. 265–272 (2002).

[2]Balogh, E. et al. Comparison of remission criteria in a tumour necrosis factor inhibitor treated rheumatoid arthritis longitudinal cohort: patient global health is a confounder. Arthritis Res. Ther.15, R221 (2013).

[3]Galloway, J. B. et al. Anti-TNF therapy is associated with an increased risk of serious infections in patients with rheumatoid arthritis especially in the first 6 months of treatment: updated results from the British Society for Rheumatology Biologics Register with special emp. Rheumatology (Oxford).50, 124–131 (2011).

[4]Kamperidis, P. et al. Development of a novel recombinant biotherapeutic with applications in targeted therapy of human arthritis. Arthritis Rheum.63, 3758–3767 (2011).

Disclosure of Interests:

None declared

OP0136 RITUXIMAB PREVENTS THE PROGRESSION OF B-CELL DRIVEN INFLAMMATORY INFILTRATE IN THE MINOR SALIVARY GLANDS OF PRIMARY SJOGREN’S SYNDROME BY DOWNREGULATING IMMUNOLOGICAL PATHWAYS KEY IN ECTOPIC GERMINAL CENTRE ORGANIZATION: RESULTS FROM THE TRACTISS TRIAL

Background:

The pathogenic role of B-cells in primary Sjögren’s Syndrome (pSS) is well established and B cell abnormalities. Because of the substantial role of B-cells, rituximab (RTX), a chimeric anti-CD20 monoclonal antibody, has been considered as a potential biologic disease modifying drug to reduce disease activity in pSS. To date, the TRial for Anti-B-Cell Therapy In patients with pSS (TRACTISS) is the largest multi-centre, placebo-controlled trial with RTX. Despite the unmet primary endpoints (30% reduction in fatigue or oral dryness, measured by visual analogue scale), RTX treated patients showed an improvement in unstimulated whole salivary flow (Bowman et al. Arthritis Rheumatol 2017;69:1440–1450).

Objectives:

To provide the first longitudinal transcriptomic and histological analysis at 3 time points over 48 weeks of labial SGs of pSS patients treated with RTX, in comparison to placebo, from the TRACTISS cohort.

Methods:

26 pSS patients randomised to RTX or placebo arm consented for labial SG biopsies at baseline, weeks 16 and 48. Patients received two 1000mg cycles of RTX or placebo at baseline and week 24. SG focus score, inflammatory aggregate area fraction, B-cells (CD20+), T-cells (CD3+), follicular dendritic cells (FDCs) (CD21+) and plasma cells (CD138+) density were assessed by H&E and immunofluorescence staining. The histological analysis was performed by digital imaging using QuPath software. RNA was extracted from matched labial SG lobules and sequenced with Illumina platform. A Principal Component Analysis (PCA) and features driving the PCA were investigated along with the most influential gene loadings. The limma-voom R pipeline was used to extract Differential Expressed Genes (DEGs) between placebo and RTX group at week 48, and gene ontology (GO) enrichment analysis performed through EnrichR to derive GO terms and pathways associated with DEGs.

Results:

Placebo-treated labial SGs showed a worsening of inflammation highlighted by the increment of B-cell density, development of new FDC networks, and a higher ectopic GC prevalence at week 48, compared to RTX-treated patients. No difference in total T-cells and plasma cell infiltration was observed. RTX downregulated genes involved in immune cell recruitment and inflammatory aggregate organisation (e.g. CCR7, CCL19, CD52, and PDCD1) and gene signature-based analysis of 64 immune cell types highlighted how RTX preferentially blocked class-switched- and memory-B-cells infiltration in SGs at week 48. Pathway analyses confirmed the downregulation of leukocyte migration, MHC class II antigen presentation, and T-cell co-stimulation immunological pathways, such as the CD40 receptor complex pathway. The analysis of placebo SGs transcriptomic at week 48 showed a higher expression of genes linked to ectopic GC organisation, such as CXCL13, CCL19, LTβ, in female compared to male subjects. Gender was confirmed as a key co-variate responsible for most of the variation in the PCA, together with the SG focus score and the foci area fraction.

Conclusion:

Treatment with RTX showed beneficial effects on labial SG inflammatory infiltration in pSS, by downregulating genes involved in immune cell recruitment, activation and organisation in ectopic GCs. Class-switched-B-cells, memory-B-cells and FDC network development were primarily affected appearing to be responsible for the lack of progression in SG B cell infiltration in the RTX compared to the placebo arm in which clear worsening of SG immunopathology over 48 weeks was detected in female patients. Although a clear association with the clinical improvement in unstimulated salivary flow observed at week 48 in RTX-treated patients could not be established given the low number of patients consenting to 3 longitudinal biopsies it is conceivable that RTX is responsible for preserving exocrine function.

Acknowledgements:

SJB receives a salary contribution from the NIHR Birmingham Biomedical Research Centre.

Disclosure of Interests:

Elena Pontarini: None declared, Farzana Chowdhury: None declared, Elisabetta Sciacca: None declared, Sofia Grigoriadou: None declared, Felice Rivellese: None declared, Davide Lucchesi: None declared, Katriona Goldmann: None declared, Liliane Fossati-Jimack: None declared, Paul Emery: None declared, Wan Fai Ng: None declared, Nurhan Sutcliffe: None declared, Colin Everett: None declared, Catherine Fernandez: None declared, Anwar Tappuni: None declared, Myles Lewis: None declared, Costantino Pitzalis: None declared, Simon J. Bowman Consultant of: SJB In 2020 I have received consultancy fees from Novartis, Abbvie and Galapagos., Michele Bombardieri: None declared

OP0011 INTEGRATION OF FLOW AND DIGITAL CYTOMETRY IN EARLY TREATMENT-NAÏVE RHEUMATOID ARTHRITIS IDENTIFIES DISTINCT IMMUNOPHENOTYPES IN PERIPHERAL BLOOD AND DISEASE TISSUE

Background:

The study of synovial tissue in patients with Rheumatoid Arthritis (RA) has led to the identification of synovial patterns of immune cell infiltration and specific cellular subsets associated that have been disease activity and clinical outcomes(1–3). However, the relationship of circulating and synovial immune cell sub-sets with histopathological features and clinical outcomes remains to be defined.

Objectives:

To assess the relationship of peripheral blood and synovial immune cells with RA histopathology and clinical outcomes, by performing flow and digital cytometry in matched peripheral blood and synovial samples from patients with early RA.

Methods:

70 patients with early (<12 months) untreated RA (2010 criteria) recruited in the pathobiology of early Arthritis Cohort (PEAC) at the Barts Health NHS Trust were included(1). Peripheral blood mononuclear cells (n=70) were analysed by flow cytometry. Matched synovial tissues (n=70) obtained by minimally invasive ultrasound-guided synovial biopsy underwent semi-quantitative scoring (0-4) of immune cell infiltration and classification into lympho-myeloid (LM), diffuse-myeloid (DM) and pauci-immune (PI) pathotypes, as previously described(1). 49 synovial and 36 matched peripheral blood samples underwent RNA-sequencing and were analysed by digital cytometry (Xcell) (4) and Singular Value Decomposition (SVD).

Results:

Circulating B cells and their subsets showed significant inverse correlations with inflammatory markers (ESR, CRP), disease activity (swollen joints, four components and two components(5) DAS28) and ultrasound scores (Fig 1A). Among T cell subsets, CXCR5-PD1hiICOS+CD4+ T cells (T peripheral helper cells, Tph) had strong positive correlations with inflammatory markers (ESR and CRP), disease activity (DAS28) and ultrasound scores (Fig 1B). Tph in the peripheral blood also correlated with immune cell infiltration in synovia (Fig 1C) and were significantly higher in patients with a LM pathotype (Fig 1D). Accordingly, circulating Tph were associated with synovial LM pathotype independently of clinical features such as DAS28, ACPA positivity, Body Mass Index (BMI) and age (AUC 0.821). By applying digital cytometry in matched synovial and peripheral blood samples, synovial B and T cells were significantly higher in patients with a LM pathotype, in line with the histological definition of the LM pathotype – rich in B and T cells. On the contrary, circulating B cells and total CD4 and CD8 T cells were significantly lower in patients with a synovial LM pathotype (Fig 1E). The Tph signature in synovia derived by Singular Value Decomposition (SVD) correlated with baseline ESR (R 0.38, p<0.0001) and DAS28 (R 0.35, p <0.0001) and with delta-DAS28 after 6 months of treatment with conventional synthetic DMARDs (R 0.27, p 0.026). Finally, the baseline synovial Tph signature was significantly higher in patients who progressed to the use of biologics and was predictive of future biologic DMARDs use, independently of baseline DAS28, ACPA positivity, BMI and age (AUC 0.703).

Conclusion:

By combining conventional flow cytometry in the peripheral blood and digital cytometry on matched synovial and peripheral blood samples, we highlight diverging associations of circulating immune cell subsets with synovial inflammation and pathotypes. Tph cells, in particular, emerge as predictors of lympho-myeloid synovial inflammation and disease progression.

References:

[1]F. Humby et al., Ann. Rheum. Dis. 78, 761–772 (2019), doi:10.1136/annrheumdis-2018-214539. [2]M. J. Lewis et al., Cell Rep. 28, 2455-2470.e5 (2019), doi:10.1016/j.celrep.2019.07.091.[3]D. a Rao et al., Nat. Publ. Gr. 542, 110–114 (2017), doi:10.1038/nature20810.[4]D. Aran et al., Genome Biol. 18, 220 (2017), doi:10.1186/s13059-017-1349-1.[5]E. M. A. Hensor et al., Rheumatology. 58, 1400–1409 (2019), doi:10.1093/rheumatology/kez049.

Figure 1.

Acknowledgements:

The Pathobiology of Early Arthritis Cohort (PEAC) was supported by the MRC (grant 36661). Versus Arthritis provided funding infrastructure support (grant 20022). F. Rivellese is funded by an NIHR Transitional Research Fellowship (TRF-2018-11-ST2-002). We would like to thank the patients and the clinical and laboratory team (core team) at Queen Mary University of London.

Disclosure of Interests:

None declared

IL-23 skin and joint profiling in psoriatic arthritis: novel perspectives in understanding clinical responses to IL-23 inhibitors

OBJECTIVES

To determine the relationship between synovial versus skin transcriptional/histological profiles in patients with active psoriatic arthritis (PsA) and explore mechanistic links between diseased tissue pathology and clinical outcomes.

METHODS

Twenty-seven active PsA patients were enrolled in an observational/open-label study and underwent biopsies of synovium and paired lesional/non-lesional skin before starting anti-tumour necrosis factor (TNF) (if biologic-naïve) or ustekinumab (if anti-TNF inadequate responders). Molecular analysis of 80-inflammation-related genes and protein levels for interleukin (IL)-23p40/IL-23p19/IL-23R were assessed by real-time-PCR and immunohistochemistry, respectively.

RESULTS

At baseline, all patients had persistent active disease as per inclusion criteria. At primary end-point (16-weeks post-treatment), skin responses favoured ustekinumab, while joint responses favoured anti-TNF therapies. Principal component analysis revealed distinct clustering of synovial tissue gene expression away from the matched skin. While IL12B, IL23A and IL23R were homogeneously expressed in lesional skin, their expression was extremely heterogeneous in paired synovial tissues. Here, IL-23 transcriptomic/protein expression was strongly linked to patients with high-grade synovitis who, however, were not distinguishable by conventional clinimetric measures.

CONCLUSIONS

PsA synovial tissue shows a heterogeneous IL-23 axis profile when compared with matched skin. Synovial molecular pathology may help to identify among clinically indistinguishable patients those with a greater probability of responding to IL-23 inhibitors.

WNT3A-loaded exosomes enable cartilage repair

Cartilage defects repair poorly. Recent genetic studies suggest that WNT3a may contribute to cartilage regeneration, however the dense, avascular cartilage extracellular matrix limits its penetration and signalling to chondrocytes. Extracellular vesicles actively penetrate intact cartilage. This study investigates the effect of delivering WNT3a into large cartilage defects in vivo using exosomes as a delivery vehicle. Exosomes were purified by ultracentrifugation from conditioned medium of either L-cells overexpressing WNT3a or control un-transduced L-cells, and characterized by electron microscopy, nanoparticle tracking analysis and marker profiling. WNT3a loaded on exosomes was quantified by western blotting and functionally characterized in vitro using the SUPER8TOPFlash reporter assay and other established readouts including proliferation and proteoglycan content. In vivo pathway activation was assessed using TCF/Lef:H2B-GFP reporter mice. Wnt3a loaded exosomes were injected into the knees of mice, in which large osteochondral defects were surgically generated. The degree of repair was histologically scored after 8 weeks. WNT3a was successfully loaded on exosomes and resulted in activation of WNT signalling in vitro. In vivo, recombinant WNT3a failed to activate WNT signalling in cartilage, whereas a single administration of WNT3a loaded exosomes activated canonical WNT signalling for at least one week, and eight weeks later, improved the repair of osteochondral defects. WNT3a assembled on exosomes, is efficiently delivered into cartilage and contributes to the healing of osteochondral defects.

Effects of targeting the transcription factors Ikaros and Aiolos on B cell activation and differentiation in systemic lupus erythematosus

Objective

To evaluate the effects of targeting Ikaros and Aiolos by cereblon modulator iberdomide on the activation and differentiation of B-cells from patients with systemic lupus erythematosus (SLE).

Methods

CD19⁺ B-cells isolated from the peripheral blood of patients with SLE (n=41) were cultured with TLR7 ligand resiquimod ±IFNα together with iberdomide or control from day 0 (n=16). Additionally, in vitro B-cell differentiation was induced by stimulation with IL-2/IL-10/IL-15/CD40L/resiquimod with iberdomide or control, given at day 0 or at day 4. At day 5, immunoglobulins were measured by ELISA and cells analysed by flow cytometry. RNA-Seq was performed on fluorescence-activated cell-sorted CD27^-IgD⁺ naïve-B-cells and CD20^lowCD27⁺CD38⁺ plasmablasts to investigate the transcriptional consequences of iberdomide.

Results

Iberdomide significantly inhibited the TLR7 and IFNα-mediated production of immunoglobulins from SLE B-cells and the production of antinuclear antibodies as well as significantly reducing the number of CD27⁺CD38⁺ plasmablasts (0.3±0.18, vehicle 1.01±0.56, p=0.011) and CD138⁺ plasma cells (0.12±0.06, vehicle 0.28±0.02, p=0.03). Additionally, treatment with iberdomide from day 0 significantly inhibited the differentiation of SLE B-cells into plasmablasts (6.4±13.5 vs vehicle 34.9±20.1, p=0.013) and antibody production. When given at later stages of differentiation, iberdomide did not affect the numbers of plasmablasts or the production of antibodies; however, it induced a significant modulation of gene expression involving IKZF1 and IKZF3 transcriptional programmes in both naïve B-cells and plasmablasts (400 and 461 differentially modulated genes, respectively, false discovery rate<0.05).

Conclusion

These results demonstrate the relevance of Ikaros and Aiolos as therapeutic targets in SLE due to their ability to modulate B cell activation and differentiation downstream of TLR7.

Calcium calmodulin kinase II activity is required for cartilage homeostasis in osteoarthritis

WNT ligands can activate several signalling cascades of pivotal importance during development and regenerative processes. Their de-regulation has been associated with the onset of different diseases. Here we investigated the role of the WNT/Calcium Calmodulin Kinase II (CaMKII) pathway in osteoarthritis. We identified Heme Oxygenase I (HMOX1) and Sox-9 as specific markers of the WNT/CaMKII signalling in articular chondrocytes through a microarray analysis. We showed that the expression of the activated form of CaMKII, phospho-CaMKII, was increased in human and murine osteoarthritis and the expression of HMOX1 was accordingly reduced, demonstrating the activation of the pathway during disease progression. To elucidate its function, we administered the CaMKII inhibitor KN93 to mice in which osteoarthritis was induced by resection of the anterior horn of the medial meniscus and of the medial collateral ligament in the knee joint. Pharmacological blockade of CaMKII exacerbated cartilage damage and bone remodelling. Finally, we showed that CaMKII inhibition in articular chondrocytes upregulated the expression of matrix remodelling enzymes alone and in combination with Interleukin 1. These results suggest an important homeostatic role of the WNT/CaMKII signalling in osteoarthritis which could be exploited in the future for therapeutic purposes.

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.

Novel Bispecific Antibody for Synovial-Specific Target Delivery of Anti-TNF Therapy in Rheumatoid Arthritis

Biologic drugs, especially anti-TNF, are considered as the gold standard therapy in rheumatoid arthritis. However, non-uniform efficacy, incidence of infections, and high costs are major concerns. Novel tissue-specific agents may overcome the current limitations of systemic administration, providing improved potency, and safety. We developed a bispecific antibody (BsAb), combining human arthritic joint targeting, via the synovial-specific single-chain variable fragment (scFv)-A7 antibody, and TNFα neutralization, via the scFv-anti-TNFα of adalimumab, with the binding/blocking capacity comparable to adalimumab -immunoglobulin G (IgG). Tissue-targeting capacity of the BsAb was confirmed on the human arthritic synovium in vitro and in a synovium xenograft Severe combined immune deficient (SCID) mouse model. Peak graft accumulation occurred at 48 h after injection with sustained levels over adalimumab-IgG for 7 days and increased therapeutic effect, efficiently decreasing tissue cellularity, and markers of inflammation with higher potency compared to the standard treatment. This study provides the first description of a BsAb capable of drug delivery, specifically to the disease tissue, and a strong evidence of improved therapeutic effect on the human arthritic synovium, with applications to other existing biologics.