Immune aging - A mechanism in autoimmune disease.

Evidence is emerging that the process of immune aging is a mechanism leading to autoimmunity. Over lifetime, the immune system adapts to profound changes in hematopoiesis and lymphogenesis, and progressively restructures in face of an ever-expanding exposome. Older adults fail to generate adequate immune responses against microbial infections and tumors, but accumulate aged T cells, B cells and myeloid cells. Age-associated B cells are highly efficient in autoantibody production. T-cell aging promotes the accrual of end-differentiated effector T cells with potent cytotoxic and pro-inflammatory abilities and myeloid cell aging supports a low grade, sterile and chronic inflammatory state (inflammaging). In pre-disposed individuals, immune aging can lead to frank autoimmune disease, manifesting with chronic inflammation and irreversible tissue damage. Emerging data support the concept that autoimmunity results from aging-induced failure of fundamental cellular processes in immune effector cells: genomic instability, loss of mitochondrial fitness, failing proteostasis, dwindling lysosomal degradation and inefficient autophagy. Here, we have reviewed the evidence that malfunctional mitochondria, disabled lysosomes and stressed endoplasmic reticula induce pathogenic T cells and macrophages that drive two autoimmune diseases, rheumatoid arthritis (RA) and giant cell arteritis (GCA). Recognizing immune aging as a risk factor for autoimmunity will open new avenues of immunomodulatory therapy, including the repair of malfunctioning mitochondria and lysosomes.

New Therapeutic Approaches to Large-Vessel Vasculitis.

Giant cell arteritis (GCA) and Takayasu arteritis (TAK) are large-vessel vasculitides affecting the aorta and its branches. Arterial damage from these diseases may result in ischemic complications, aneurysms, and dissections. Despite their similarities, the management of GCA and TAK differs. Glucocorticoids are used frequently but relapses are common, and glucocorticoid toxicity contributes to significant morbidity. Conventional immunosuppressive therapies can be beneficial in TAK, though their role in the management of GCA remains unclear. Tumor necrosis factor inhibitors improve remission rates and appear to limit vascular damage in TAK; these agents are not beneficial in GCA. Tocilizumab is the first biologic glucocorticoid-sparing agent approved for use in GCA and also appears to be effective in TAK. A better understanding of the pathogenesis of both conditions and the availability of targeted therapies hold much promise for future management.

CTLA-4 Pathway Is Instrumental in Giant Cell Arteritis.

BACKGROUND: Giant cell arteritis (GCA) causes severe inflammation of the aorta and its branches and is characterized by intense effector T-cell infiltration. The roles that immune checkpoints play in the pathogenesis of GCA are still unclear. Our aim was to study the immune checkpoint interplay in GCA. METHODS: First, we used VigiBase, the World Health Organization international pharmacovigilance database, to evaluate the relationship between GCA occurrence and immune checkpoint inhibitors treatments. We then further dissected the role of immune checkpoint inhibitors in the pathogenesis of GCA, using immunohistochemistry, immunofluorescence, transcriptomics, and flow cytometry on peripheral blood mononuclear cells and aortic tissues of GCA patients and appropriated controls. RESULTS: Using VigiBase, we identified GCA as a significant immune-related adverse event associated with anti-CTLA-4 (cytotoxic T-lymphocyte-associated protein-4) but not anti-PD-1 (anti-programmed death-1) nor anti-PD-L1 (anti-programmed death-ligand 1) treatment. We further dissected a critical role for the CTLA-4 pathway in GCA by identification of the dysregulation of CTLA-4-derived gene pathways and proteins in CD4+ (cluster of differentiation 4) T cells (and specifically regulatory T cells) present in blood and aorta of GCA patients versus controls. While regulatory T cells were less abundant and activated/suppressive in blood and aorta of GCA versus controls, they still specifically upregulated CTLA-4. Activated and proliferating CTLA-4+ Ki-67+ regulatory T cells from GCA were more sensitive to anti-CTLA-4 (ipilimumab)-mediated in vitro depletion versus controls. CONCLUSIONS: We highlighted the instrumental role of CTLA-4 immune checkpoint in GCA, which provides a strong rationale for targeting this pathway.

Clonal haematopoiesis across the age spectrum of vasculitis patients with Takayasu's arteritis, ANCA-associated vasculitis and giant cell arteritis.

OBJECTIVES: Ageing and inflammation are associated with clonal haematopoiesis (CH), the emergence of somatic mutations in haematopoietic cells. This study details CH in patients with systemic vasculitis in association with clinical, haematological and immunological parameters. METHODS: Patients with three forms of vasculitis were screened for CH in peripheral blood by error-corrected sequencing. Relative contributions of age and vasculitis on CH prevalence were calculated using multivariable logistic regression. Clonal hierarchies were assessed by proteogenomic single-cell DNA sequencing, and functional experiments were performed in association with CH status. RESULTS: Patients with Takayasu's arteritis (TAK; n=70; mean age=33.2 years), antineutrophil cytoplasmic antibody-associated vasculitis (AAV; n=47; mean age=55.3 years) and giant cell arteritis (GCA; n=59; mean age=71.2 years) were studied. CH, most commonly in DNMT3A and TET2, was detected in 34% (60/176) of patients versus 18% (28/151) of age-matched controls (p<0.01). Prevalence of CH was independently associated with age (standardised B=0.96, p<0.01) and vasculitis (standardised B=0.46, p<0.01), occurring in 61%, 32% and 13% of patients with GCA, AAV and TAK, respectively. Both branched and linear clonal trajectories showed myeloid-lineage bias, and CH was associated with markers of cellular activation. In GCA, mutations were detected in temporal artery biopsies, and clinical relapse correlated with CH in a dose-dependent relationship with clone size. CONCLUSIONS: Age was more strongly associated with CH prevalence than inflammation in systemic vasculitis. Clonal profile was dominated by DNMT3A mutations which were associated with relapse in GCA. CH is not likely a primary causal factor in systemic vasculitis but may contribute to inflammation.

Vascular disease persistence in giant cell arteritis: are stromal cells neglected?

Giant cell arteritis (GCA), the most common systemic vasculitis, is characterised by aberrant interactions between infiltrating and resident cells of the vessel wall. Ageing and breach of tolerance are prerequisites for GCA development, resulting in dendritic and T-cell dysfunction. Inflammatory cytokines polarise T-cells, activate resident macrophages and synergistically enhance vascular inflammation, providing a loop of autoreactivity. These events originate in the adventitia, commonly regarded as the biological epicentre of the vessel wall, with additional recruitment of cells that infiltrate and migrate towards the intima. Thus, GCA-vessels exhibit infiltrates across the vascular layers, with various cytokines and growth factors amplifying the pathogenic process. These events activate ineffective repair mechanisms, where dysfunctional vascular smooth muscle cells and fibroblasts phenotypically shift along their lineage and colonise the intima. While high-dose glucocorticoids broadly suppress these inflammatory events, they cause well known deleterious effects. Despite the emerging targeted therapeutics, disease relapse remains common, affecting >50% of patients. This may reflect a discrepancy between systemic and local mediators of inflammation. Indeed, temporal arteries and aortas of GCA-patients can show immune-mediated abnormalities, despite the treatment induced clinical remission. The mechanisms of persistence of vascular disease in GCA remain elusive. Studies in other chronic inflammatory diseases point to the fibroblasts (and their lineage cells including myofibroblasts) as possible orchestrators or even effectors of disease chronicity through interactions with immune cells. Here, we critically review the contribution of immune and stromal cells to GCA pathogenesis and analyse the molecular mechanisms by which these would underpin the persistence of vascular disease.

Plasma proteome profiling in giant cell arteritis.

OBJECTIVES: This study aimed to identify plasma proteomic signatures that differentiate active and inactive giant cell arteritis (GCA) from non-disease controls. By comprehensively profiling the plasma proteome of both patients with GCA and controls, we aimed to identify plasma proteins that (1) distinguish patients from controls and (2) associate with disease activity in GCA. METHODS: Plasma samples were obtained from 30 patients with GCA in a multi-institutional, prospective longitudinal study: one captured during active disease and another while in clinical remission. Samples from 30 age-matched/sex-matched/race-matched non-disease controls were also collected. A high-throughput, aptamer-based proteomics assay, which examines over 7000 protein features, was used to generate plasma proteome profiles from study participants. RESULTS: After adjusting for potential confounders, we identified 537 proteins differentially abundant between active GCA and controls, and 781 between inactive GCA and controls. These proteins suggest distinct immune responses, metabolic pathways and potentially novel physiological processes involved in each disease state. Additionally, we found 16 proteins associated with disease activity in patients with active GCA. Random forest models trained on the plasma proteome profiles accurately differentiated active and inactive GCA groups from controls (95.0% and 98.3% in 10-fold cross-validation, respectively). However, plasma proteins alone provided limited ability to distinguish between active and inactive disease states within the same patients. CONCLUSIONS: This comprehensive analysis of the plasma proteome in GCA suggests that blood protein signatures integrated with machine learning hold promise for discovering multiplex biomarkers for GCA.

Senescent cells in giant cell arteritis display an inflammatory phenotype participating in tissue injury via IL-6-dependent pathways.

OBJECTIVES: Age is the strongest risk factor of giant cell arteritis (GCA), implying a possible pathogenetic role of cellular senescence. To address this question, we applied an established senescence specific multimarker algorithm in temporal artery biopsies (TABs) of GCA patients. METHODS: 75(+) TABs from GCA patients, 22(-) TABs from polymyalgia rheumatica (PMR) patients and 10(-) TABs from non-GCA/non-PMR patients were retrospectively retrieved and analysed. Synovial tissue specimens from patients with inflammatory arthritis and aorta tissue were used as disease control samples. Senescent cells and their histological origin were identified with specific cellular markers; IL-6 and MMP-9 were investigated as components of the senescent associated secretory phenotype by triple costaining. GCA or PMR artery culture supernatants were applied to fibroblasts, HUVECs and monocytes with or without IL-6R blocking agent to explore the induction of IL-6-associated cellular senescence. RESULTS: Senescent cells were present in GCA arteries at higher proportion compared with PMR (9.50% vs 2.66%, respectively, p<0.0001) and were mainly originated from fibroblasts, macrophages and endothelial cells. IL-6 was expressed by senescent fibroblasts, and macrophages while MMP-9 by senescent fibroblasts only. IL-6(+) senescent cells were associated with the extension of vascular inflammation (transmural inflammation vs adventitia limited disease: 10.02% vs 4.37%, respectively, p<0.0001). GCA but not PMR artery culture supernatant could induce IL-6-associated senescence that was partially inhibited by IL-6R blockade. CONCLUSIONS: Senescent cells with inflammatory phenotype are present in GCA arteries and are associated with the tissue inflammatory bulk, suggesting a potential implication in disease pathogenesis.

Age, anticoagulants, hypertension and cardiovascular genetic traits predict cranial ischaemic complications in patients with giant cell arteritis.

OBJECTIVES: This project aimed to determine whether cranial ischaemic complications at the presentation of giant cell arteritis (GCA) were associated with pre-existing cardiovascular (CV) risk factors, CV disease or genetic risk of CV-related traits. METHODS: 1946 GCA patients with clinicodemographic data at GCA presentation were included. Associations between pre-existing CV-related traits (including Polygenic Risk Scores (PRS) for CV traits) and cranial ischaemic complications were tested. A model for cranial ischaemic complications was optimised using an elastic net approach. Positional gene mapping of associated PRS was performed to improve biological understanding. RESULTS: In a sample of 1946 GCA patients (median age=71, 68.7% female), 17% had cranial ischaemic complications at presentation. In univariable analyses, 10 variables were associated with complications (likelihood-ratio test p≤0.05). In multivariable analysis, the two variables with the strongest effects, with or without PRS in the model, were anticoagulant therapy (adjusted OR (95% CI)=0.21 (0.05 to 0.62), p=4.95×10-3) and age (adjusted OR (95% CI)=1.60 (0.73 to 3.66), p=2.52×10-3, for ≥80 years versus <60 years). In sensitivity analyses omitting anticoagulant therapy from multivariable analysis, age and hypertension were associated with cranial ischaemic complications at presentation (hypertension: adjusted OR (95% CI)=1.35 (1.03 to 1.75), p=0.03). Positional gene mapping of an associated transient ischaemic attack PRS identified TEK, CD96 and MROH9 loci. CONCLUSION: Age and hypertension were risk factors for cranial ischaemic complications at GCA presentation, but in this dataset, anticoagulation appeared protective. Positional gene mapping suggested a role for immune and coagulation-related pathways in the pathogenesis of complications. Further studies are needed before implementation in clinical practice.

Should all patients with polymyalgia rheumatica have a vascular ultrasound assessment?

There is a growing appreciation that both giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are closely interrelated conditions that have significant overlap in aetiology, clinical characteristics and treatment regimens. Subclinical GCA in PMR is becoming increasingly recognised, and there is evolving evidence that this may be a more aggressive disease phenotype than PMR. Ultrasound (US) lends itself well as a screening tool for GCA in PMR; it is inexpensive, non-invasive, widely available, lacks ionising radiation, may be performed at the bedside and is recommended by EULAR as a first-line investigation for suspected GCA. There is insufficient evidence to currently recommend that all patients with PMR should have a US assessment for vascular involvement. However, as clinical and laboratory parameters alone do not accurately diagnose patients with subclinical GCA, we suggest that vascular US will be increasingly performed by rheumatologists in practice to identify these patients with PMR, preferably as part of larger prospective outcome studies.

Treat-to-target recommendations in giant cell arteritis and polymyalgia rheumatica.

OBJECTIVES: To develop treat-to-target (T2T) recommendations in giant cell arteritis (GCA) and polymyalgia rheumatica (PMR). METHODS: A systematic literature review was conducted to retrieve data on treatment targets and outcomes in GCA/PMR as well as to identify the evidence for the effectiveness of a T2T-based management approach in these diseases. Based on evidence and expert opinion, the task force (29 participants from 10 countries consisting of physicians, a healthcare professional and a patient) developed recommendations, with consensus obtained through voting. The final level of agreement was provided anonymously. RESULTS: Five overarching principles and six-specific recommendations were formulated. Management of GCA and PMR should be based on shared decisions between patient and physician recognising the need for urgent treatment of GCA to avoid ischaemic complications, and it should aim at maximising health-related quality of life in both diseases. The treatment targets are achievement and maintenance of remission, as well as prevention of tissue ischaemia and vascular damage. Comorbidities need to be considered when assessing disease activity and selecting treatment. CONCLUSION: These are the first T2T recommendations for GCA and PMR. Treatment targets, as well as strategies to assess, achieve and maintain these targets have been defined. The research agenda highlights the gaps in evidence and the need for future research.

Subclinical giant cell arteritis increases the risk of relapse in polymyalgia rheumatica.

OBJECTIVE: The aim of the present study was to determine the clinical significance of subclinical giant cell arteritis (GCA) in polymyalgia rheumatica (PMR) and ascertain its optimal treatment approach. METHODS: Patients with PMR who fulfilled the 2012 European Alliance of Associations for Rheumatology/American College of Rheumatology Provisional Classification Criteria for PMR, did not have GCA symptoms and were routinely followed up for 2 years and were stratified into two groups, according to their ultrasound results: isolated PMR and PMR with subclinical GCA. The outcomes (relapses, glucocorticoid use and disease-modifying antirheumatic drug treatments) between groups were compared. RESULTS: We included 150 patients with PMR (50 with subclinical GCA) with a median (IQR) follow-up of 22 (20-24) months. Overall, 47 patients (31.3 %) had a relapse, 31 (62%) in the subclinical GCA group and 16 (16%) in the isolated PMR group (p<0.001). Among patients with subclinical GCA, no differences were found in the mean (SD) prednisone starting dosage between relapsed and non-relapsed patients (32.4±15.6 vs 35.5±12.1 mg, respectively, p=0.722). Patients with subclinical GCA who relapsed had a faster prednisone dose tapering in the first 3 months compared with the non-relapsed patients, with a mean dose at the third month of 10.0±5.2 versus 15.2±7.9 mg daily (p<0.001). No differences were found between relapsing and non-relapsed patients with subclinical GCA regarding age, sex, C reactive protein and erythrocyte sedimentation rate. CONCLUSIONS: Patients with PMR and subclinical GCA had a significantly higher number of relapses during a 2-year follow-up than patients with isolated PMR. Lower starting doses and rapid glucocorticoid tapering in the first 3 months emerged as risk factors for relapse.

Polymyalgia rheumatica shows metabolomic alterations that are further altered by glucocorticoid treatment: Identification of metabolic correlates of fatigue.

OBJECTIVE: In polymyalgia rheumatica (PMR), glucocorticoids (GCs) relieve pain and stiffness, but fatigue may persist. We aimed to explore the effect of disease, GCs and PMR symptoms in the metabolite signatures of peripheral blood from patients with PMR or the related disease, giant cell arteritis (GCA). METHODS: Nuclear magnetic resonance spectroscopy was performed on serum from 40 patients with untreated PMR, 84 with new-onset confirmed GCA, and 53 with suspected GCA who later were clinically confirmed non-GCA, and 39 age-matched controls. Further samples from PMR patients were taken one and six months into glucocorticoid therapy to explore relationship of metabolites to persistent fatigue. 100 metabolites were identified using Chenomx and statistical analysis performed in SIMCA-P to examine the relationship between metabolic profiles and, disease, GC treatment or symptoms. RESULTS: The metabolite signature of patients with PMR and GCA differed from that of age-matched non-inflammatory controls (R2 > 0.7). There was a smaller separation between patients with clinically confirmed GCA and those with suspected GCA who later were clinically confirmed non-GCA (R2 = 0.135). In PMR, metabolite signatures were further altered with glucocorticoid treatment (R2 = 0.42) but did not return to that seen in controls. Metabolites correlated with CRP, pain, stiffness, and fatigue (R2 ≥ 0.39). CRP, pain, and stiffness declined with treatment and were associated with 3-hydroxybutyrate and acetoacetate, but fatigue did not. Metabolites differentiated patients with high and low fatigue both before and after treatment (R2 > 0.9). Low serum glutamine was predictive of high fatigue at both time points (0.79-fold change). CONCLUSION: PMR and GCA alter the metabolite signature. In PMR, this is further altered by glucocorticoid therapy. Treatment-induced metabolite changes were linked to measures of inflammation (CRP, pain and stiffness), but not to fatigue. Furthermore, metabolite signatures distinguished patients with high or low fatigue.

Impaired IL-6-induced JAK-STAT signaling in CD4+ T cells associates with longer treatment duration in giant cell arteritis.

INTRODUCTION: The IL-12-IFNγ-Th1 and the IL-6-IL-23-Th17 axes are considered the dominant pathogenic pathways in Giant Cell Arteritis (GCA). Both pathways signal via activation of the downstream JAK/STAT proteins. We hypothesized that phosphorylated STAT (pSTAT) signatures in circulating immune cells may aid to stratify GCA-patients for personalized treatment. METHODS: To investigate pSTAT expression, PBMCs from treatment-naive GCA-patients (n = 18), infection controls (INF, n = 11) and age-matched healthy controls (HC, n = 15) were stimulated in vitro with IL-6, IL-2, IL-10, IFN-γ, M-CSF or GM-CSF, and stained with CD3, CD4, CD19, CD45RO, pSTAT1, pSTAT3, pSTAT5 antibodies, and analyzed by flow cytometry. Serum IL-6, sIL-6-receptor and gp130 were measured by Luminex. The change in percentages of pSTAT3+CD4+T-cells was evaluated at diagnosis and at 3 months and 1-year of follow-up. Kaplan-Meier analyses was used to asses prognostic accuracy. RESULTS: Analysis of IL-6 stimulated immune cell subsets revealed a significant decrease in percentages of pSTAT3+CD4+T-cells of GCA-patients and INF-controls compared to HCs. Following patient stratification according to high (median>1.5 pg/mL) and low (median<1.5 pg/mL) IL-6 levels, we observed a reduction in the pSTAT3 response in GCA-patients with high serum IL-6. Percentages of pSTAT3+CD4+T-cells in patients with high serum IL-6 levels at diagnosis normalized after glucocorticoid (GC) treatment. Importantly, we found that patients with low percentages of pSTAT3+CD4+T-cells at baseline require longer GC-treatment. CONCLUSION: Overall, in GCA, the percentages of in vitro IL-6-induced pSTAT3+CD4+T-cells likely reflect prior in vivo exposure to high IL-6 and may serve as a prognostic marker for GC-treatment duration and may assist improving personalized treatment options in the future.

Neointimal myofibroblasts contribute to maintaining Th1/Tc1 and Th17/Tc17 inflammation in giant cell arteritis.

Vascular smooth muscle cells (VSMCs) have been shown to play a role in the pathogenesis of giant cell arteritis (GCA) through their capacity to produce chemokines recruiting T cells and monocytes in the arterial wall and their ability to migrate and proliferate in the neointima where they acquire a myofibroblast (MF) phenotype, leading to vascular stenosis. This study aimed to investigate if MFs could also impact T-cell polarization. Confocal microscopy was used to analyze fresh fragments of temporal artery biopsies (TABs). Healthy TAB sections were cultured to obtain MFs, which were then treated or not with interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) and analyzed by immunofluorescence and RT-PCR. After peripheral blood mononuclear cells and MFs were co-cultured for seven days, T-cell polarization was analyzed by flow cytometry. In the neointima of GCA arteries, we observed a phenotypic heterogeneity among VSMCs that was consistent with a MF phenotype (α-SMA+CD90+desmin+MYH11+) with a high level of STAT1 phosphorylation. Co-culture experiments showed that MFs sustain Th1/Tc1 and Th17/Tc17 polarizations. The increased Th1 and Tc1 polarization was further enhanced following the stimulation of MFs with IFN-γ and TNF-α, which induced STAT1 phosphorylation in MFs. These findings correlated with increases in the production of IL-1ß, IL-6, IL-12 and IL-23 by MFs. Our study showed that MFs play an additional role in the pathogenesis of GCA through their ability to maintain Th17/Tc17 and Th1/Tc1 polarizations, the latter being further enhanced in case of stimulation of MF with IFN-γ and TNF-α.

Decoding CD4+ T cell transcriptome in giant cell arteritis: Novel pathways and altered cross-talk with monocytes.

BACKGROUND: Giant cell arteritis (GCA) is an immune-mediated large-vessels vasculitis with complex etiology. Although the pathogenic mechanisms remain poorly understood, a central role for CD4+ T cells has been demonstrated. In this context, understanding the transcriptome dysregulation in GCA CD4+ T cells will yield new insights into its pathogenesis. METHODS: Transcriptome analysis was conducted on CD4+ T cells from 70 patients with GCA with different disease activity and treatment status (active patients before treatment and patients in remission with and without glucocorticoid treatment), and 28 healthy controls. The study also evaluated potential impacts of DNA methylation on gene expression alterations and assessed cross-talk with CD14+ monocytes. RESULTS: This study has uncovered a substantial number of genes and pathways potentially contributing to the pathogenicity of CD4+ T cells in GCA. Specifically, CD4+ T cells from GCA patients with active disease exhibited altered expression levels of genes involved in multiple immune-related processes, including various interleukins (IL) signaling pathways. Notably, IL-2, a decisive interleukin for regulatory T cells homeostasis, was among the most significant. Additionally, impaired apoptotic pathways appear crucial in GCA development. Our findings also suggest that histone-related epigenetic pathways may be implicated in promoting an inflammatory phenotype in GCA active patients. Finally, our study observed altered signaling communication, such as the Jagged-Notch signaling, between CD4+ T cells and monocytes that could have pathogenic relevance in GCA. CONCLUSIONS: Our study suggests the participation of novel cytokines and pathways and the occurrence of a disruption of monocyte-T cell crosstalk driving GCA pathogenesis.

miR-146a and miR-146b regulate the expression of ICAM-1 in giant cell arteritis.

Giant cell arteritis (GCA) is an inflammatory disease of large/medium-sized arteries. MiRNAs are small, non-coding RNAs that inhibit gene expression at post-transcriptional level. Several miRNAs have been shown to be dysregulated in temporal artery biopsies (TABs) from GCA patients, but their role is unknown. The aims of the present work were: to gain insight into the link between inflammation and miRNA up-regulation in GCA; to identify the role of miR-146a and miR-146b. Primary cultures from TABs were treated with IL-1ß, IL-6, soluble IL-6R (sIL6R), IL-17, IL-22, IFNγ, LPS and PolyIC. Correlations between cytokine mRNA and miRNA levels were determined in inflamed TABs. Primary cultures from TABs, human aortic endothelial and smooth muscle cells and ex-vivo TAB sections were transfected with synthetic miR-146a and miR-146b to mimic miRNA activities. Cell viability, target gene expression, cytokine levels in culture supernatants were assayed. Treatment of primary cultures from TABs with IL-1ß and IL-17 increased miR-146a expression while IL-1ß, IL-6+sIL6R and IFNγ increased miR-146b expression. IFNγ and IL-1ß mRNA levels correlated with miR-146a/b levels. Following transfection, cell viability decreased only in primary cultures from TABs. Moreover, transfection of miR-146a/b mimics increased ICAM-1 gene expression and production of the soluble form of ICAM-1 by primary cultures from TABs and by ex-vivo TABs. ICAM-1 expression was higher in inflamed than normal TABs and ICAM-1 levels correlated with miR-146a/b levels. Expression of miR-146a and miR-146b in GCA appeared to be driven by inflammatory cytokines (e.g. IL-1ß, IFNγ). miR-146a and miR-146b seem responsible for the increase of soluble ICAM-1.

Single-cell transcriptomic profiling reveals a pathogenic role of cytotoxic CD4+ T cells in giant cell arteritis.

Giant cell arteritis (GCA) is a systemic vasculitis mediated by an aberrant immunological response against the blood vessel wall. Although the pathogenic mechanisms that drive GCA have not yet been elucidated, there is strong evidence that CD4+ T cells are key drivers of the inflammatory process occurring in this vasculitis. The aim of this study was to further delineate the role of CD4+ T cells in GCA by applying single-cell RNA sequencing and T cell receptor (TCR) repertoire profiling to 114.799 circulating CD4+ T cells from eight GCA patients in two different clinical states, active and in remission, and eight healthy controls. Our results revealed an expansion of cytotoxic CD4+ T lymphocytes (CTLs) in active GCA patients, which expressed higher levels of cytotoxic and chemotactic genes when compared to patients in remission and controls. Accordingly, differentially expressed genes in CTLs of active patients were enriched in pathways related to granzyme-mediated apoptosis, inflammation, and the recruitment of different immune cells, suggesting a role of this cell type in the inflammatory and vascular remodelling processes occurring in GCA. CTLs also exhibited a higher clonal expansion in active patients with respect to those in remission. Drug repurposing analysis prioritized maraviroc, which targeted CTLs, as potentially repositionable for this vasculitis. In addition, effector regulatory T cells (Tregs) were decreased in GCA and showed lower expression of genes involved in their suppressive activity. These findings provide further insights into the pathogenic role of CD4+ T cells in GCA and suggest targeting CTLs as a potential therapeutic option.

Follow-up ultrasound examination in patients with newly diagnosed giant cell arteritis.

OBJECTIVES: Ultrasound is a standard tool to diagnose giant cell arteritis (GCA). Until now, only few studies investigated the role of ultrasound in the follow-up of GCA. The aim of this study was to assess the changes in the intima media thickness (IMT), total number of affected arteries and provisional OMERACT GCA ultrasonography score (OGUS) in a 12-months follow-up period. METHODS: Patients with newly diagnosed GCA were prospectively enrolled. Ultrasound examinations of facial, temporal, carotid, vertebral and axillary arteries were performed at baseline, after three, six, nine and 12 months. Changes of IMT, total number of affected arteries, and OGUS values were evaluated. In a subgroup of patients, exams were conducted weekly in the first 100 days. RESULTS: Fifty patients were enrolled, 36 completed the follow-up. Significant reductions in IMT, total number of affected arteries and OGUS were observed. Eighteen patients presented to weekly exams. The mean IMT of the axillary artery normalized after seven days, while IMT of the common temporal artery normalized after 50 days. The mean OGUS values were below one after six months. There were no differences in IMT changes between GCA patients with or without PMR or between those with and without additional tocilizumab treatment. A relapse occurred in 4 patients. At relapse, mean IMT and OGUS were higher as compared with the preceding assessment. No predictive values indicating a relapse were identified. CONCLUSION: Vascular ultrasound is sensitive to change in GCA. The presence of PMR or treatment with tocilizumab did not affect IMT decrease.

Vessel wall MRI in giant cell arteritis: standardized protocol and scoring approach developed by an international working group.

OBJECTIVES: There are an increasing number of centers performing research on high-resolution vessel wall magnetic resonance imaging (VW-MRI) in giant cell arteritis (GCA). However, harmonized approaches to VW-MRI in GCA are lacking and are essential to performing multicentre studies. Using a data-driven, consensus-based approach, an international expert group developed a standardized MRI protocol and scoring system to advance multi-centered research in cranial GCA. METHODS: A targeted literature review of VW-MRI in cranial GCA was conducted. A working group comprised of radiologists, rheumatologists, and ophthalmologists with expertise in VW-MRI and GCA reviewed the results of the literature search, presented relevant data and images from their respective centers, and then reached consensus on recommendations related to key MRI structures, MRI sequences, scoring system, and other important considerations. RESULTS: A total of 21 relevant articles were identified and reviewed. Based on published literature, structures to be evaluated on MRI were categorized based on anatomic location (extradural cranial, intradural cranial, and orbits) and prioritization (core vs elective). Essential and elective sequences to comprehensively image cranial and orbital structures while minimizing scan time were determined along with scoring systems to grade contrast enhancement. CONCLUSION: This report describes a standardized approach to facilitate research of VW-MRI in cranial GCA that is the result of a multi-disciplinary, international collaboration of experts in VW-MRI and/or GCA.

MRVAS-introducing a standardized magnetic resonance scoring system for assessing the extent of inflammatory burden in giant cell arteritis.

OBJECTIVES: Our aim was to introduce a standardized system for assessing the extent of GCA on MRI, i.e. the Magnetic Resonance Vasculitis Activity Score (MRVAS). To obtain a comprehensive view, we used an extensive MRI protocol including cranial vessels and the aorta with its branches. To test reliability, MRI was assessed by four readers with different levels of experience. METHODS: A total of 80 patients with suspected GCA underwent MRI of the cranial arteries and the aorta and its branches (20 vessel segments). Every vessel was rated dichotomous [inflamed (coded as 1) or not (coded as 0)], providing a summed score of 0-20. Blinded readers [two experienced radiologists (ExR) and two inexperienced radiologists (InR)] applied the MRVAS on an individual vessel and an overall level (defined as the highest score of any of the individual vessel scores). To determine interrater agreement, Cohen's κ was calculated for pairwise comparison of each reader for individual vessel segments. Intraclass correlation coefficients (ICCs) were used for the MRVAS. RESULTS: Concordance rates were excellent for both subcohorts on an individual vessel-based (GCA: ICC 0.95; non-GCA: ICC 0.96) and overall MRVAS level (GCA: ICC 0.96; non-GCA: ICC 1.0). Interrater agreement yielded significant concordance (P < 0.001) for all pairs (κ range 0.78-0.98). No significant differences between ExRs and InRs were observed (P = 0.38). CONCLUSION: The proposed MRVAS allows standardized scoring of inflammation in GCA and achieved high agreement rates in a prospective setting.