Arteries In Giant Cell Arteritis Research Articles

Visualization of the Internal Thoracic Arteries in Giant Cell Arteritis on 18 F-FDG Semiconductor PET/CT.

A 72-year-old woman presented with the fever and the pain of skull and face for 2 weeks. 18 F-FDG PET/CT equipped with semiconductor detectors revealed strong uptake not only in the temporal, cervical, subclavian arteries, and aorta, but also in the bilateral internal thoracic arteries. The diagnosis of giant cell arteritis was made. Semiconductor PET can visualize small arteries such as the internal thoracic artery. The patients with giant cell arteritis are at a high risk of ischemic heart disease, and inflammatory involvement of the internal thoracic arteries may affect the outcome of coronary artery bypass grafting.

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-1β, 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.

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

ObjectivesAge 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...

Cytokine producing B-cells and their capability to polarize macrophages in giant cell arteritis

ObjectiveThe lack of disease-specific autoantibodies in giant cell arteritis (GCA) suggests an alternative role for B-cells readily detected in the inflamed arteries. Here we study the cytokine profile of tissue infiltrated and peripheral blood B-cells of patients with GCA. Moreover, we investigate the macrophage skewing capability of B-cell-derived cytokines. MethodsThe presence of various cytokines in B-cell areas in temporal artery (n = 11) and aorta (n = 10) was identified by immunohistochemistry. PBMCs of patients with GCA (n = 11) and polymyalgia rheumatica (n = 10), and 14 age- and sex-matched healthy controls (HC) were stimulated, followed by flow cytometry for cytokine expression in B-cells. The skewing potential of B-cell-derived cytokines (n = 6 for GCA and HC) on macrophages was studied in vitro. ResultsThe presence of IL-6, GM-CSF, TNFα, IFNγ, LTβ and IL-10 was documented in B-cells and B-cell rich areas of GCA arteries. In vitro, B-cell-derived cytokines (from both GCA and HC) skewed macrophages towards a pro-inflammatory phenotype with enhanced expression of IL-6, IL-1β, TNFα, IL-23, YKL-40 and MMP-9. In vitro stimulated peripheral blood B-cells from treatment-naïve GCA patients showed an enhanced frequency of IL-6+ and TNFα+IL-6+ B-cells compared to HCs. This difference was no longer detected in treatment-induced remission. Erythrocyte sedimentation rate positively correlated with IL-6+TNFα+ B-cells. ConclusionB-cells are capable of producing cytokines and steering macrophages towards a pro-inflammatory phenotype. Although the capacity of B-cells in skewing macrophages is not GCA specific, these data support a cytokine-mediated role for B-cells in GCA and provide grounds for B-cell targeted therapy in GCA.

Use of high-plex data provides novel insights into the temporal artery processes of giant cell arteritis.

To identify the key coding genes underlying the biomarkers and pathways associated with giant cell arteritis (GCA), we performed an in situ spatial profiling of molecules involved in the temporal arteries of GCA patients and controls. Furthermore, we performed pharmacogenomic network analysis to identify potential treatment targets. Using human formalin-fixed paraffin-embedded temporal artery biopsy samples (GCA, n = 9; controls, n = 7), we performed a whole transcriptome analysis using the NanoString GeoMx Digital Spatial Profiler. In total, 59 regions of interest were selected in the intima, media, adventitia, and perivascular adipose tissue (PVAT). Differentially expressed genes (DEGs) (fold-change > 2 or < -2, p-adjusted < 0.01) were compared across each layer to build a spatial and pharmacogenomic network and to explore the pathophysiological mechanisms of GCA. Most of the transcriptome (12,076 genes) was upregulated in GCA arteries, compared to control arteries. Among the screened genes, 282, 227, 40, and 5 DEGs were identified in the intima, media, adventitia, and PVAT, respectively. Genes involved in the immune process and vascular remodeling were upregulated within GCA temporal arteries but differed across the arterial layers. The immune-related functions and vascular remodeling were limited to the intima and media. This study is the first to perform an in situ spatial profiling characterization of the molecules involved in GCA. The pharmacogenomic network analysis identified potential target genes for approved and novel immunotherapies.

Damage to extracranial arteries in giant cell arteritis according to PET/CT

The aim of the study was to assess the incidence of arterial lesions of various localizations in patients with giant cell arteritis (GCA) according to positron emission and computed tomography (PET/CT) with 18F-fluorodeoxyglucose (18F-FDG).Methods. Patients over 50 years of age diagnosed with GCA (with or without polymyalgia rheumatica) were included in a retrospective study. Damage to extracranial arteries was assessed based on the accumulation of 18F-FDG in the walls of large vessels according to PET/CT data.Results. The study included 47 patients, 14 (30%) men and 33 (70%) women, with a median age of 65 [57; 68] years. In 32 (68%) patients, 18F-FDG-PET/CT was performed before the start of therapy with glucocorticosteroids (GCS), in 15 (32%) after the start of treatment. In 40 (91%) patients, signs of damage to extracranial vessels of various localization were revealed, most often in the thoracic and abdominal aorta (72% and 64%, respectively).Conclusions. According to 18F-FDG-PET/CT data, in most patients with GCA, not only the arteries of the head and neck, but also vessels of other localization are involved in the pathological process.

Diagnostic validity of ultrasound including extra-cranial arteries in giant cell arteritis.

Color Doppler ultrasound (CDUS) of the temporal arteries (TA) is becoming the first test to be performed for suspected giant cell arteritis (GCA). Our aim was to assess the added value of including CDUS of large vessels (LV) in the diagnosis of GCA. We performed an observational and retrospective study of consecutive patients with suspected GCA. Baseline CDUS of the TA and LV (axillary, subclavian, and carotid) were conducted. We defined the CDUS finding as positive if the halo sign was present. Of 198 patients with suspected GCA, 87 were eventually diagnosed with GCA: 45 (51.7%) had a cranial pattern exclusively, 31 (35.6%) had both a cranial and an LV pattern, and 11 (12.6%) had an isolated LV pattern. CDUS of the TA had a sensitivity of 83.9%, specificity of 97.3%, and positive and negative predictive values (PPV, NPV) of 96.1% and 88.5%, respectively. When LV was added, sensitivity increased to 96.6% and NPV to 98.2%. Specificity was 97.3% and PPV was 96.6%. As for LVs, the axillary, subclavian, and carotid arteries were involved in 87.8%, 77.4%, and 34.4%, respectively. Isolated axillary examination resulted in a loss of 12.2% of patients with LV involvement; however, inclusion of the axillary and subclavian arteries retained 100% of patients with LV involvement. Detection of GCA by ultrasound should routinely include examinations of the TA and LV (at least the axillary and subclavian arteries) to improve diagnostic accuracy. More than 12% of patients in our cohort had isolated LV involvement. Key Points • Extracranial involvement in GCA is very common: half of patients have extracranial vasculitis and more than 12% isolated LV involvement that can be demonstrated with CDUS. • Adding a CDUS examination of LV to TA increased sensitivity (from 83.9 to 96.6%) and the negative predictive value (from 88.5 to 98.2%) for diagnosis of GCA. • In our cohort, if we only examined the axillary arteries, 12.2% of the CGA with LV involvement would not have been diagnosed. • We propose a CDUS protocol that includes examination of the TA and LV (at least the axillary and subclavian arteries) routinely in cases of suspected GCA.

Giant Cell and Takayasu Arteritiss

Many diseases cause inflammatory large vessel vasculitis. However, giant cell arteritis (GCA) and Takayasu arteritis (TA) are the most common large vessel vasculitides. Vascular surgeons should be aware of the workup and management of these two large vessel vasculitides as they are often involved in the care of these patients. Medical management is the primary therapy for both GCA and TA. However, surgical or endovascular therapy may be necessary in certain circumstances. This review explores all of the above aspects of both GCA and TA. Tables highlight inflammatory large vessel vasculitides, major differences between GCA and TA, criteria for the classification of GCA and TA, the distribution of arterial lesions in GCA and TA, and clinical presentation in TA patients by symptom. Figures show occlusive or aneurysmal disease of the aorta and its branches; pallid and sectoral edema; external carotid artery, superficial temporal artery, and facial nerve anatomy; frequency of arterial involvement in GCA and TA; the placement of incision for superficial temporal artery biopsy; right subclavian and axillary arteries in TA; and histology of the superficial temporal artery and a superficial temporal artery in GCA. This review contains 12 figures, 6 tables, and 89 references.

Giant Cell Arteritis: Updates and Controversies.

Giant cell arteritis (GCA) is a systemic granulomatous vasculitis affecting the medium and large-size arteries, and may present with a range of ophthalmic findings. This review will cover GCA epidemiology, pathophysiology, clinical presentation, diagnostic workup, and treatment. GCA is commonly found in elderly patients and individuals of Scandinavian descent. Recent publications suggest it may be more common in African Americans and Hispanics than previously thought. It is very rare in Asian and Middle-Eastern populations, and there is little data regarding African populations. Genetic studies have identified increased risk associated with HLA-DRB1*04. Rather than a response to a specific antigen such as varicella zoster virus, current immunology research suggests that GCA results from changes associated with the aging immune system. Arteritic anterior ischemic optic neuropathy is the most common ophthalmic manifestation of GCA, but central or branch retinal artery occlusion, ophthalmic artery occlusion, cranial neuropathies causing diplopia, and more rarely anterior segment ischemia and anisocoria may also occur. Clinical testing including visual field testing, OCT, OCT-A, ICG and fluorescein angiography can be helpful in suggesting a diagnosis in addition to the clinical exam. GCA is ultimately a clinical diagnosis, but it is usually supported with lab results, pathology, and/or imaging. Temporal artery biopsy (TAB) remains the gold standard diagnostic test although its sensitivity is debated and practice patterns still vary with respect to sample length and whether unilateral or simultaneous bilateral biopsies are performed. Some studies have reported higher sensitivity of ultrasounds over TAB, with added benefits of time efficiency and cost effectiveness, promoting the diagnostic use of ultrasounds. MRI and even PET CT protocols offer additional options for less invasive diagnostic testing. Vision-threatening GCA is treated acutely with emergent admission for intravenous methylprednisolone, and long-term high dose oral corticosteroids remain the standard of care, despite common and sometimes serious side effects. The use of steroid-sparing alternatives such as tocilizumab is becoming more common and additional agents are being investigated.

Blocking GM-CSF receptor α with mavrilimumab reduces infiltrating cells, pro-inflammatory markers and neoangiogenesis in ex vivo cultured arteries from patients with giant cell arteritis

BackgroundEffective and safe therapies are needed for the treatment of patients with giant cell arteritis (GCA). Emerging as a key cytokine in inflammation, granulocyte-macrophage colony stimulating factor (GM-CSF) may play...

Inflammatory Cell Composition and Immune-Related microRNA Signature of Temporal Artery Biopsies From Patients With Giant Cell Arteritis.

ObjectivesThe aim of this study was to quantitatively assess distinct immune cell subsets comprising inflammatory infiltrate in temporal artery biopsies (TABs) from patients with giant cell arteritis (GCA), and to link the obtained histopathological data with expression profiles of immune-related microRNAs (miRNAs).MethodsThe study included 68 formalin-fixed, paraffin-embedded TABs from treatment-naïve patients, including 30 histologically positive GCA and 16 negative GCA TABs, and 22 control non-GCA TABs. Quantitative assessment of histological parameters was performed using histopathological and immunohistochemical techniques. miRNA expression analysis was performed by quantitative real-time PCR.ResultsIntense transmural mononuclear inflammatory infiltrates in TAB-positive GCA arteries were predominantly composed of CD3+, CD4+ and CD8+ T lymphocytes, and CD68+ macrophages, accompanied by a strong nuclear overexpression of the nuclear factor of activated T cells, cytoplasmic 1 (NFATC) in the lymphocyte infiltrate fraction. Furthermore, TAB-positive GCA arteries were characterized by significant overexpression of nine pro-inflammatory miRNAs (miR-132-3p/-142-3p/-142-5p/-155-5p/-210-3p/-212-3p/-326/-342-5p/-511-5p) and a significant under-expression of six regulatory immune-related miRNAs (miR-30a-5p/-30b-5p/-30c-5p/-30d-5p/-30e-5p/-124-3p), whose expression levels significantly associated with most evaluated histopathological parameters. Notably, we revealed miR-132-3p/-142-3p/-142-5p/-155-5p/-212-3p/-511-5p as major promoters of arterial inflammation and miR-30a-5p/-30c-5p/-30d-5p as putative regulators of NFATC signaling in TAB-positive GCA arteries.ConclusionOverall, we demonstrated that an altered arterial tissue-specific pro-inflammatory miRNA signature favors enhanced T cell-driven inflammation and macrophage activity in TAB-positive GCA arteries. Moreover, dysregulation of several immune-related miRNAs seems to contribute crucially to GCA pathogenesis, through impairing their regulatory activity towards T cell-mediated immune responses driven by the calcineurin (CaN)/NFAT signaling pathway, indicating their therapeutic, diagnostic and prognostic potential.

Development and Proof of Concept of a Low-Cost Ultrasound Training Model for Diagnosis of Giant Cell Arteritis Using 3D Printing.

Objectives: Currently, ultrasound (US) is widely used for the diagnosis of giant cell arteritis (GCA). Our aim was to develop a low-cost US training model for diagnosis of GCA of the temporal and axillary artery using a modern 3D printing system. Methods: We designed an US training model, which enables measurement of the intima-media thickness (IMT) of temporal and axillary arteries using Autodesk Fusion360. This model was printed using a modern 3D printer (Formlabs Form3) and embedded in ballistic gelatine. The ultrasound images including measurement of the IMT by ultrasound specialists in GCA were compared to ultrasound images in acute GCA and healthy subjects. Results: Our ultrasound training model of the axillary and temporal artery displayed a very similar ultrasound morphology compared to real US images and fulfilled the OMERACT ultrasound definitions of normal and pathological temporal and axillary arteries in GCA. The IMT measurements were in line with published cut-off values for normal and pathological IMT values in GCA and healthy individuals. When testing the models on blinded US specialists in GCA, they were identified correctly in all test rounds with an intra-class coefficient of 0.99. Conclusion: The production of low-cost ultrasound training models of normal and pathological temporal and axillary arteries in GCA, which fulfil the OMERACT ultrasound definitions and adhere to the published IMT cut-off values in GCA, is feasible. Ultrasound specialists identified each respective model correctly in every case.

OMERACT definition and reliability assessment of chronic ultrasound lesions of the axillary artery in giant cell arteritis

ObjectivesTo define chronic ultrasound lesions of the axillary artery (AA) in long-standing giant cell arteritis (GCA) and to evaluate the reliability of the new ultrasound definition in a web-based exercise. MethodsA structured Delphi, involving an expert panel of the Large Vessel Vasculitis subgroup of the Outcome Measures in Rheumatology (OMERACT) Ultrasound Working Group was carried out. The reliability of the new definition was tested in a 2-round web-based exercise involving 23 experts and using 50 still images each from AA of long-standing and acute GCA patients, as well as 50 images from healthy individuals. ResultsThe final OMERACT ultrasound definition of chronic changes was based on measurement and appearance of the intima-media complex. The overall reliability of the new definition for chronic ultrasound changes in longstanding GCA of the AA was good to excellent with Light's kappa values of 0.79-0.80 for inter-reader reliability and mean Light's-kappa of 0.88 for intra-reader reliability. The mean inter-rater and intra-rater agreements were 86-87% and 92%, respectively. Good reliabilities were observed comparing the vessels with longstanding versus acute GCA with a mean agreement and kappa values of 81% and 0.63, respectively. ConclusionThe new OMERACT ultrasound definition for chronic vasculitis of the AA in GCA revealed a good to excellent inter- and intra-reader reliability in a web-based exercise of experts.

Active Giant Cell Vasculitis Diagnosis with 68Ga PSMA PET/CT Imaging.

Vasculitis is a multisystem disease characterized by inflammation with infiltration of leukocytes into the blood vessels. Giant cell arteritis (GCA) is the most common form of vasculitis that mostly affects medium- and large-sized arteries. 18Fluorine-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) is increasingly used to diagnose inflammation of large arteries in GCA. Galium-68 prostate-specific membrane antigen (PSMA) PET/CT has a vital role in the assessment of patients with prostate cancer for recurrence and metastasis of the disease. Various benign and non-prostate malignant conditions may give rise to increased PSMA uptake. Herein, we demonstrate that PSMA uptake can be seen in GCA.

FRI0010 GM-CSFR PATHWAY IS IMPLICATED IN PATHOGENIC INFLAMMATORY MECHANISMS IN GIANT CELL ARTERITIS

Background:Giant Cell Arteritis (GCA) is characterized by inflammation of large and medium arteries. Classic symptoms include headaches, malaise and, in severe cases, blindness and aortic aneurysms. Corticosteroids (CS) are the first line of treatment. Relapsing disease patients undergo multiple courses of CS therapy increasing their CS exposure and toxicity. A significant unmet need for disease-modifying CS-sparing therapy remains in GCA as the efficacy of current treatment options, including tocilizumab have limitations.We have previously reported elevated expression of granulocyte-macrophage colony stimulating factor (GM-CSF) pathway transcriptomic signature in GCA vessels. GM-CSF may contribute to underlying disease mechanisms by regulating inflammatory macrophages, dendritic cells (DCs) and T helper (TH1/TH17) cells which are involved in GCA pathogenesis. GM-CSF produced by T cells1can promote polarization of inflammatory macrophages2and recruitment and differentiation of monocytes into inflammatory DCs2that can in turn recruit T cells and stimulate TH1/TH17 differentiation creating a feedback loop. GM-CSF may also exert direct effects on angiogenesis3and vessel wall remodeling4.Objectives:To demonstrate the contributing role of GM-CSF pathway to inflammation in GCA arteries.Methods:Immunostaining was used to examine expression of GM-CSF and GM-CSF-Rα proteins in temporal artery biopsies (TABs) from GCA and controls (patients with suspected but not confirmed GCA and a negative TAB). Costaining with cell markers such as CD31, CD3, and CD68 allowed visualization of cells expressing GM-CSF and GM-CSF-Rα. Expression of GM-CSF pathway molecules such as phospho-JAK2 and PU.1 proteins was detected by immunohistochemical staining of GCA and control TABs.Ex vivocultured GCA arteries treated (10 each) with mavrilimumab (anti-GM-CSF-Rα) or placebo for 5 days were assayed for gene expression by qPCR, and culture supernatants were analyzed by ELISA.Results:Endothelial cells and macrophages were the main cell types expressing GM-CSF and GM-CSF-Rα. Increased expression of phospho-JAK2 (activated signaling molecule) and nuclear-localized PU.1 (transcription factor) in GCA TABs compared to controls indicated the presence of active GM-CSF signaling pathway in GCA.Inhibition of PU.1 mRNA expression inex vivocultures of GCA arteries treated with mavrilimumab indicated blockade of GM-CSFR signaling pathway. Mavrilimumab induced decrease in mRNA expression of key cell type markers including DC and macrophage activation markers CD83 and HLA-DRA, monocyte markers CD14 and CD16, T cell marker CD3ε, and B cell marker CD20 in these GCA artery cultures. Expression of inflammatory TH1/TH17 factors IFNγ (mRNA), TNFα, CXCL10 (IFNγ-stimulated chemokine) and IL-6 (mRNA and protein) was also inhibited by mavrilimumab in GCA artery cultures.Conclusion:Increased GM-CSF, GM-CSF-Rα, and downstream pathway-associated protein levels in GCA biopsies were consistent with previously-observed increased transcriptome signature. Expression of genes associated with inflammatory cells was suppressed by mavrilimumab in cultured GCA arteries. These data implicate the GM-CSF pathway in GCA pathophysiology and increase confidence in rationale for targeting the GM-CSF pathway in GCA.

Magnetic Resonance Imaging Abnormalities of the Optic Nerve Sheath and Intracranial Internal Carotid Artery in Giant Cell Arteritis.

Giant cell arteritis (GCA) is an important diagnostic consideration in elderly patients with vision changes. Superficial temporal artery biopsy (TAB) has long been considered the gold standard diagnostic approach for GCA, but MRI has gained interest as an alternative diagnostic modality. Although most of the literature has focused on imaging abnormalities of branches of the external carotid artery, there have been a few reports of GCA-related inflammatory involvement of the orbit and internal carotid arteries (ICAs) on MRI. This was a retrospective cross-sectional study of patients undergoing TAB at a single tertiary referral center over a 5-year period. Patients who had undergone contrast-enhanced MRI of the brain and orbits within 1 month of biopsy were included. Fifty-four TAB-positive and 78 TAB-negative patients were reviewed, with the MRI studies of 7 TAB-positive and 6 TAB-negative patients deemed adequate for interpretation. MRI studies were reviewed by 2 masked neuroradiologists, and the findings were correlated with biopsy results and clinical findings. Intracranial ICA vessel wall enhancement was identified in 6 of 7 TAB-positive patients (sensitivity 86%), compared with 2 of 6 TAB-negative patients (specificity 67%). Optic nerve sheath enhancement was identified in 5 of 7 TAB-positive patients (sensitivity 71%) and in 2 of 6 TAB-negative patients (specificity 67%), bilateral in all such cases. The combination of both abnormal imaging findings was observed in 5 of 7 TAB-positive patients (sensitivity 71%) and in none of the 6 TAB-negative patients (specificity 100%). Intracranial ICA and optic nerve sheath enhancement were observed in a majority of patients with TAB-proven GCA, and the combination of these findings was highly specific for GCA. Identification of these abnormalities on MRI should raise concern for GCA and prompt a thorough review of systems, laboratory testing, and consideration of TAB in patients with ocular complaints potentially consistent with ischemia.

The Microbiome of Temporal Arteries.

Objective:A role for microorganisms in giant cell arteritis (GCA) has long been suspected. We describe the microbiomes of temporal arteries from patients with GCA and controls.Methods:Temporal artery biopsies from patients suspected to have GCA were collected under aseptic conditions and snap-frozen. Fluorescence in situ hybridization (FISH) and long-read 16S rRNA-gene sequencing was used to examine microbiomes of temporal arteries. Taxonomic classification of bacterial sequences was performed to the genus level and relative abundances were calculated. Microbiome differential abundances were analyzed by principal coordinate analysis (PCoA) with comparative Unifrac distances and predicted functional profiling using PICRUSt.Results:Forty-seven patients, including 9 with biopsy-positive GCA, 15 with biopsy-negative GCA and 23 controls without GCA, were enrolled. FISH for bacterial DNA revealed signal in the arterial media. Beta, but not alpha, diversity differed between GCA and control temporal arteries (P = 0.042). Importantly, there were no significant differences between biopsy-positive and biopsy-negative GCA (P > 0.99). The largest differential abundances seen between GCA and non-GCA temporal arteries included Proteobacteria (P), Bifidobacterium (g), Parasutterella (g), and Granulicatella (g) [Log 2-fold change ≥ 4].Conclusion:Temporal arteries are not sterile, but rather are inhabited by a community of bacteria. We have demonstrated that there are microbiomic differences between GCA and non-GCA temporal arteries, but not between biopsy-positive and biopsy-negative GCA.

Expression and Function of IL12/23 Related Cytokine Subunits (p35, p40, and p19) in Giant-Cell Arteritis Lesions: Contribution of p40 to Th1- and Th17-Mediated Inflammatory Pathways.

Giant-cell arteritis (GCA) is considered a T helper (Th)1- and Th17-mediated disease. Interleukin (IL)-12 is a heterodimeric cytokine (p35/p40) involved in Th1 differentiation. When combining with p19 subunit, p40 compose IL-23, a powerful pro-inflammatory cytokine that maintains Th17 response. The aims of this study were to investigate p40, p35, and p19 subunit expression in GCA lesions and their combinations to conform different cytokines, to assess the effect of glucocorticoid treatment on subunit expression, and to explore functional roles of p40 by culturing temporal artery sections with a neutralizing anti-human IL-12/IL-23p40 antibody. p40 and p19 mRNA concentrations measured by real-time RT-PCR were significantly higher in temporal arteries from 50 patients compared to 20 controls (4.35 ± 4.06 vs 0.51 ± 0.75; p < 0.0001 and 20.32 ± 21.78 vs 4.17 ± 4.43 relative units; p < 0.0001, respectively). No differences were found in constitutively expressed p35 mRNA. Contrarily, p40 and p19 mRNAs were decreased in temporal arteries from 16 treated GCA patients vs those from 34 treatment-naïve GCA patients. Accordingly, dexamethasone reduced p40 and p19 expression in cultured arteries. Subunit associations to conform IL-12 and IL-23 were confirmed by proximity-ligation assay in GCA lesions. Immunofluorescence revealed widespread p19 and p35 expression by inflammatory cells, independent from p40. Blocking IL-12/IL-23p40 tended to reduce IFNγ and IL-17 mRNA production by cultured GCA arteries and tended to increase Th17 inducers IL-1β and IL-6. IL-12 and IL-23 heterodimers are increased in GCA lesions and decrease with glucocorticoid treatment. p19 and p35 subunits are much more abundant than p40, indicating an independent role for these subunits or their potential association with alternative subunits. The modest effect of IL-12/IL-23p40 neutralization may indicate compensation by redundant cytokines or cytokines resulting from alternative combinations.

New insights into the pathogenesis of giant cell arteritis.

Giant cell arteritis (GCA) is an inflammatory chronic disease occurring exclusively in elderly individuals. Until recently, the disease has been considered a unique disease resulting from the interaction in the walls of susceptible arteries, between an unknown infectious agents with local dendritic cells (DCs), activated CD4 T cells and effector macrophages. Recent evidence has shown that this view was too simplistic and has clarified many of the pathogenetic aspects of the disease. Many genetic studies recently published have identified different new genes, including cytokines, adhesion molecules and regulators of innate immunity, as crucial players in the development and progression of GCA. Recent evidence suggests that there is heterogeneity of histological lesions in GCA, that are correlated with different immunological Th9 and Th17 signature. The recent demonstration that Varicella-zoster virus (VZV) antigen is present in the 64% of GCA-negative TAs and in the 73% of GCA-positive TAs could represent an important point of arrival in the search for a causative agent in the pathogenesis of a metameric disease such as GCA. In this context, cytokines such as IL-32 and IL-33 that act as a danger signal following tissue damage and infection are over-expressed in GCA arteries. Artery tertiary lymphoid organs, present in up to 50% of GCA-positive arteries, could represent the sites were primary immune responses and T- and B-cell autoimmune responses against viral antigens are organized. The recently demonstrated disturbed distribution of B cells in GCA could be also relevant in the pathogenesis of the disease, possibly contributing to the enhanced IL-6 response. Altogether, these evidences may clarify many pathogenetic aspect of the disease, also suggesting complexity greater than first imagined.

Blocking interferon γ reduces expression of chemokines CXCL9, CXCL10 and CXCL11 and decreases macrophage infiltration in ex vivo cultured arteries from patients with giant cell arteritis

BackgroundInterferon γ (IFNγ) is considered a seminal cytokine in the pathogenesis of giant cell arteritis (GCA), but its functional role has not been investigated. We explored changes in infiltrating cells...