Jennifer McCormick

Synovial tissue hypoxia and inflammation in vivo

Introduction Hypoxia is a microenvironmental feature in the inflamed joint, which promotes survival advantage for cells. The aim of this study was to examine the relationship of partial oxygen pressure in the synovial tissue (tPO2) in patients with inflammatory arthritis with macroscopic/microscopic inflammation and local levels of proinflammatory mediators. Methods Patients with inflammatory arthritis underwent full clinical assessment and video arthroscopy to quantify macroscopic synovitis and measure synovial tPO2 under direct visualisation. Cell specific markers (CD3 (T cells), CD68 (macrophages), Ki67 (cell proliferation) and terminal deoxynucleotidyl transferase dUTP nick end labelling (cell apoptosis)) were quantified by immunohistology. In vitro migration was assessed in primary and normal synoviocytes (synovial fibroblast cells (SFCs)) using a wound repair scratch assay. Levels of tumour necrosis factor α (TNFα), interleukin 1β (IL1β), interferon γ (IFNγ), IL6, macrophage inflammatory protein 3α (MIP3α) and IL8 were quantified, in matched serum and synovial fluid, by multiplex cytokine assay and ELISA. Results The tPO2 was 22.5 (range 3.2–54.1) mm Hg and correlated inversely with macroscopic synovitis (r=−0.421, p=0.02), sublining CD3 cells (−0.611, p<0.01) and sublining CD68 cells (r=−0.615, p<0.001). No relationship with cell proliferation or apoptosis was found. Primary and normal SFCs exposed to 1% and 3% oxygen (reflecting the median tPO2 in vivo) induced cell migration. This was coupled with significantly higher levels of synovial fluid tumour necrosis factor α (TNFα), IL1β, IFNγ and MIP3α in patients with tPO2 <20 mm Hg (all p values <0.05). Conclusions This is the first study to show a direct in vivo correlation between synovial tPO2, inflammation and cell migration, thus it is proposed that hypoxia is a possible primary driver of inflammatory processes in the arthritic joint.

Human rheumatoid arthritis tissue production of IL-17A drives matrix and cartilage degradation: synergy with tumour necrosis factor-α, Oncostatin M and response to biologic therapies

IntroductionThe aim of this study was to examine IL-17A in patients, following anti-TNF-α therapy and the effect of IL-17A on matrix turnover and cartilage degradation.MethodsIL-17A expression was examined by ELISA and immunohistology in the rheumatoid arthritis (RA) joints. RA whole synovial tissue explant (RA ST), primary synovial fibroblasts (RASFC), human cartilage and chondrocyte cultures were stimulated with IL-17A +/- TNF-α and Oncostatin M (OSM). Matrix metalloproteinase (MMP) and tissue inhibitor (TIMP-1) were assessed by ELISA and zymography. Cartilage proteoglycan release was assessed histologically by Safranin-O staining. Clinical parameters, IL-17A, MMP/TIMP were assessed in patients pre/post biologic therapy.ResultsIL-17A levels were higher in RA vs osteoarthritis (OA)/normal joints (P < 0.05). IL-17A up-regulated MMP-1, -2, -9, and -13 in RA ST, RASFC, cartilage and chondrocyte cultures (P < 0.05). In combination with TNF-α and OSM, IL-17A shifted the MMP:TIMP-1 ratio in favor of matrix degradation (all P < 0.05). Cartilage proteoglycan depletion in response to IL-17A was mild; however, in combination with TNF-α or OSM showed almost complete proteoglycan depletion. Serum IL-17A was detected in 28% of patients commencing biologic therapy. IL-17A negative patients demonstrated reductions post therapy in serum MMP1/TIMP4, MMP3/TIMP1 and MMP3/TIMP4 ratios and an increase in CS846 (all P < 0.05). No significant changes were observed in IL-17A positive patients.ConclusionsIL-17A is produced locally in the inflamed RA joint. IL-17A promotes matrix turnover and cartilage destruction, especially in the presence of other cytokines, mimicking the joint environment. IL-17A levels are modulated in vivo, following anti-TNF therapy, and may reflect changes in matrix turnover.

Acute Serum Amyloid A Induces Migration, Angiogenesis, and Inflammation in Synovial Cells In Vitro and in a Human Rheumatoid Arthritis/SCID Mouse Chimera Model

Serum amyloid A (A-SAA), an acute-phase protein with cytokine-like properties, is expressed at sites of inflammation. This study investigated the effects of A-SAA on chemokine-regulated migration and angiogenesis using rheumatoid arthritis (RA) cells and whole-tissue explants in vitro, ex vivo, and in vivo. A-SAA levels were measured by real-time PCR and ELISA. IL-8 and MCP-1 expression was examined in RA synovial fibroblasts, human microvascular endothelial cells, and RA synovial explants by ELISA. Neutrophil transendothelial cell migration, cell adhesion, invasion, and migration were examined using transwell leukocyte/monocyte migration assays, invasion assays, and adhesion assays with or without anti–MCP-1/anti–IL-8. NF-κB was examined using a specific inhibitor and Western blotting. An RA synovial/SCID mouse chimera model was used to examine the effects of A-SAA on cell migration, proliferation, and angiogenesis in vivo. High expression of A-SAA was demonstrated in RA patients (p < 0.05). A-SAA induced chemokine expression in a time- and dose-dependent manner (p < 0.05). Blockade with anti-scavenger receptor class B member 1 and lipoxin A4 (A-SAA receptors) significantly reduced chemokine expression in RA synovial tissue explants (p < 0.05). A-SAA induced cell invasion, neutrophil–transendothelial cell migration, monocyte migration, and adhesion (all p < 0.05), effects that were blocked by anti–IL-8 or anti–MCP-1. A-SAA–induced chemokine expression was mediated through NF-κB in RA explants (p < 0.05). Finally, in the RA synovial/SCID mouse chimera model, we demonstrated for the first time in vivo that A-SAA directly induces monocyte migration from the murine circulation into RA synovial grafts, synovial cell proliferation, and angiogenesis (p < 0.05). A-SAA promotes cell migrational mechanisms and angiogenesis critical to RA pathogenesis.

Blockade of Toll-like receptor 2 prevents spontaneous cytokine release from rheumatoid arthritis ex vivo synovial explant cultures

IntroductionThe aim of this study was to examine the effect of blocking Toll-like receptor 2 (TLR2) in rheumatoid arthritis (RA) synovial cells.MethodsRA synovial tissue biopsies, obtained under direct visualization at arthroscopy, were established as synovial explant cultures ex vivo or snap frozen for immunohistology. Mononuclear cell cultures were isolated from peripheral blood and synovial fluid of RA patients. Cultures were incubated with the TLR1/2 ligand, Pam3CSK4 (200 ng, 1 and 10 μg/ml), an anti-TLR2 antibody (OPN301, 1 μg/ml) or an immunoglobulin G (IgG) (1 μg/ml) matched control. The comparative effect of OPN301 and adalimumab (anti-tumour necrosis factor alpha) on spontaneous release of proinflammatory cytokines from RA synovial explants was determined using quantitative cytokine MSD multiplex assays or ELISA. OPN301 penetration into RA synovial tissue explants cultures was assessed by immunohistology.ResultsPam3CSK4 significantly upregulated interleukin (IL)-6 and IL-8 in RA peripheral blood mononuclear cells (PBMCs), RA synovial fluid mononuclear cells (SFMCs) and RA synovial explant cultures (P < 0.05). OPN301 significantly decreased Pam3CSK4-induced cytokine production of tumour necrosis factor alpha (TNF-α), IL-1β, IL-6, interferon (IFN)-γ and IL-8 compared to IgG control in RA PBMCs and SFMCs cultures (all P < 0.05). OPN301 penetration of RA synovial tissue cultures was detected in the lining layer and perivascular regions. OPN301 significantly decreased spontaneous cytokine production of TNF-α, IL-1β, IFN-γ and IL-8 from RA synovial tissue explant cultures (all P < 0.05). Importantly, the inhibitory effect of OPN on spontaneous cytokine secretion was comparable to inhibition by anti-TNFα monoclonal antibody adalimumab.ConclusionsThese findings further support targeting TLR2 as a potential therapeutic agent for the treatment of RA.

IL-17A Expression Is Localised to Both Mononuclear and Polymorphonuclear Synovial Cell Infiltrates

Introduction This study examines the expression of IL-17A-secreting cells within the inflamed synovium and the relationship to in vivo joint hypoxia measurements. Methods IL-17A expression was quantified in synovial tissue (ST), serum and synovial fluid (SF) by immunohistochemistry and MSD-plex assays. IL-6 SF and serum levels were measured by MSD-plex assays. Dual immunofluorescence for IL-17A was quantified in ST CD15+ cells (neutrophils), Tryptase+ (mast cells) and CD4+ (T cells). Synovial tissue oxygen (tpO2) levels were measured under direct visualisation at arthroscopy. Synovial infiltration was assessed using immunohistochemistry for cell specific markers. Peripheral blood mononuclear and polymorphonuclear cells were isolated and exposed to normoxic or 3% hypoxic conditions. IL-17A and IL-6 were quantified as above in culture supernatants. Results IL-17A expression was localised to mononuclear and polymorphonuclear (PMN) cells in inflamed ST. Dual immunoflourescent staining co-localised IL-17A expression with CD15+ neutrophils Tryptase+ mast cells and CD4+T cells. % IL-17A positivity was highest on CD15+ neutrophils, followed by mast cells and then CD4+T-cells. The number of IL-17A-secreting PMN cells significantly correlated with sublining CD68 expression (r = 0.618, p<0.01). IL-17A SF levels correlated with IL-6 SF levels (r = 0.675, p<0.01). Patients categorized according to tp02< or >20mmHg, showed those with low tp02<20mmHg had significantly higher IL-17A+ mononuclear cells with no difference observed for PMNs. Exposure of mononuclear and polymorphonuclear cells to 3% hypoxia, significantly induced IL-6 in mononuclear cells, but had no effect on IL-17A expression in mononuclear and polymorphonuclear cells. Conclusion This study demonstrates IL-17A expression is localised to several immune cell subtypes within the inflamed synovial tissue, further supporting the concept that IL-17A is a key mediator in inflammatory arthritis. The association of hypoxia with Il-17A expression appears to be indirect, probably through hypoxia-induced pro-inflammatory pathways and leukocyte influx within the joint microenvironment.

Toll-Like Receptor 2 Induced Angiogenesis and Invasion Is Mediated through the Tie2 Signalling Pathway in Rheumatoid Arthritis

Background Angiogenesis is a critical early event in inflammatory arthritis, facilitating leukocyte migration into the synovium resulting in invasion and destruction of articular cartilage and bone. This study investigates the effect of TLR2 on angiogenesis, EC adhesion and invasion using microvascular endothelial cells and RA whole tissue synovial explants ex-vivo. Methods Microvascular endothelial cells (HMVEC) and RA synovial explants ex vivo were cultured with the TLR2 ligand, Pam3CSK4 (1 µg/ml). Angiopoietin 2 (Ang2), Tie2 and TLR2 expression in RA synovial tissue was assessed by immunohistology. HMVEC tube formation was assessed using Matrigel matrix assays. Ang2 was measured by ELISA. ICAM-1 cell surface expression was assessed by flow cytometry. Cell migration was assessed by wound repair scratch assays. ECM invasion, MMP-2 and -9 expression were assessed using transwell invasion chambers and zymography. To examine if the angiopoietin/Tie2 signalling pathway mediates TLR2 induced EC tube formation, invasion and migration assays were performed in the presence of a specific neutralising anti-Tie2mAb (10 ug/ml) and matched IgG isotype control Ab (10 ug/ml). Results Ang2 and Tie2 were localised to RA synovial blood vessels, and TLR2 was localised to RA synovial blood vessels, sub-lining infiltrates and the lining layer. Pam3CSK4 significantly increased angiogenenic tube formation (p<0.05), and upregulated Ang2 production in HMVEC (p<0.05) and RA synovial explants (p<0.05). Pam3CSK4 induced cell surface expression of ICAM-1, from basal level of 149±54 (MFI) to 617±103 (p<0.01). TLR-2 activation induced an 8.8±2.8 fold increase in cell invasion compared to control (p<0.05). Pam3CSK4 also induced HMVEC cell migration and induced MMP-2 and -9 from RA synovial explants. Neutralisation of the Ang2 receptor, Tie2 significantly inhibited Pam3CSK4-induced EC tube formation and invasion (p<0.05). Conclusion TLR2 activation promotes angiogenesis, cell adhesion and invasion, effects that are in part mediated through the Tie2 signalling pathway, key mechanisms involved in the pathogenesis of RA.

Hypoxia and STAT3 signalling interactions regulate pro-inflammatory pathways in rheumatoid arthritis.

OBJECTIVE To examine the effect of hypoxia on Signal Transducer and Activator of Transcription 3 (STAT3)-induced pro-inflammatory pathways in rheumatoid arthritis (RA). METHODS Detection of phospho-STAT3 was assessed in RA synovial tissue and fibroblasts (RASFC) by immunohistology/immunofluorescence. Primary RASFCs and a normal synoviocyte cell line (K4IM) were cultured under hypoxic and normoxic conditions±Stat3-siRNA, HIF-siRNA or WP1066 (JAK2-inhibitor). HIF1α, p-STAT3, p-STAT1 and Notch-1IC protein expression were analysed by western blot. Functional mechanisms were quantified by invasion chamber, matrigel and migration assays. IL-6, IL-8, IL-10 and matrixmetalloproteinases (MMP)-3 were quantified by ELISA. Notch-1 receptor, its DLL-4 ligand and downstream target genes (hrt-1, hrt-2) were quantified by real-time PCR. The effect of WP1066 on spontaneous secretion of pro/anti-inflammatory cytokines and Notch signalling was examined in RA synovial explants ex vivo. RESULTS p-STAT3 was increased in RA synovium compared with control (p<0.05). Hypoxia induced p-STAT3, p-STAT1 and HIF1α expression, an effect blocked by Stat3-siRNA and WP1066. Hypoxia-induced cell invasion, migration and cytokine production were inhibited by Stat3-siRNA (p<0.05) and WP1066 (p<0.05). While HIF1α siRNA inhibited hypoxia-induced p-STAT3 detection, Stat3-siRNA also inhibited hypoxia-induced HIF1α. Furthermore, hypoxia-induced Notch-1IC, DLL4, hrt-1 and -2 expression were significantly inhibited by WP1066 (p<0.05). Finally, in RA synovial explant cultures ex vivo, WP1066 decreased spontaneous secretion of IL-6, IL-8 and MMP3 (p<0.05), Notch-1 mRNA (p<0.05) and induced IL-10 (p<0.05). CONCLUSIONS This is the first study to provide evidence of a functional link between HIF1α, STAT3 and Notch-1 signalling in the regulation of pro-inflammatory mechanisms in RA, and further supports a role for STAT blockade in the treatment of RA.

Acute‐phase serum amyloid A regulates tumor necrosis factor α and matrix turnover and predicts disease progression in patients with inflammatory arthritis before and after biologic therapy

OBJECTIVE To investigate the relationship between acute-phase serum amyloid A (A-SAA) and joint destruction in inflammatory arthritis. METHODS Serum A-SAA and C-reactive protein (CRP) levels, the erythrocyte sedimentation rate (ESR), and levels of matrix metalloproteinase 1 (MMP-1), MMP-2, MMP-3, MMP-9, MMP-13, tissue inhibitor of metalloproteinases 1 (TIMP-1), vascular endothelial growth factor (VEGF), and type I and type II collagen-generated biomarkers C2C and C1,2C were measured at 0-3 months in patients with inflammatory arthritis commencing anti-tumor necrosis factor α (anti-TNFα) therapy and were correlated with 1-year radiographic progression. The effects of A-SAA on MMP/TIMP expression on RA fibroblast-like synoviocytes (FLS), primary human chondrocytes, and RA/psoriatic arthritis synovial explant cultures were assessed using real-time polymerase chain reaction, enzyme-linked immunosorbent assay, antibody protein arrays, and gelatin zymography. RESULTS Serum A-SAA levels were significantly (P < 0.05) correlated with MMP-3, the MMP-3:TIMP-1 ratio, C1,2C, C2C, and VEGF. The baseline A-SAA level but not the ESR or the CRP level correlated with the 28-joint swollen joint count and was independently associated with 1-year radiographic progression (P = 0.038). A-SAA increased MMP-1, MMP-3, MMP-13, and MMP/TIMP expression in RA FLS and synovial explants (P < 0.05). In chondrocytes, A-SAA induced MMP-1, MMP-3, and MMP-13 messenger RNA and protein expression (all P < 0.01), resulting in a significant shift in MMP:TIMP ratios (P < 0.05). Gelatin zymography revealed that A-SAA induced MMP-2 and MMP-9 activity. Blockade of the A-SAA receptor SR-B1 (A-SAA receptor scavenger receptor-class B type 1) inhibited MMP-3, MMP-2, and MMP-9 expression in synovial explant cultures ex vivo. Importantly, we demonstrated that A-SAA has the ability to induce TNFα expression in RA synovial explant cultures (P < 0.05). CONCLUSION A-SAA may be involved in joint destruction though MMP induction and collagen cleavage in vivo. The ability of A-SAA to regulate TNFα suggests that A-SAA signaling pathways may provide new therapeutic strategies for the treatment of inflammatory arthritis.

Interleukin-17A induction of angiogenesis, cell migration, and cytoskeletal rearrangement.

OBJECTIVE To examine the ability of interleukin-17A (IL-17A) to stimulate angiogenesis, cell migration, and cytoskeletal rearrangement. METHODS The effect of IL-17A on microvascular tube formation and extracellular matrix invasion by human dermal endothelial cells (HDECs) was assessed using Matrigel matrix and Transwell Matrigel invasion chambers. IL-17A-induced growth-related oncogene α (GROα) and monocyte chemotactic protein 1 (MCP-1) production in rheumatoid arthritis synovial fibroblasts (RASFs) and HDECs was measured by enzyme-linked immunosorbent assay. IL-17A-induced migration was assessed using peripheral blood mononuclear cell (PBMC) migration assays and wound-repair scratch assays, with or without anti-GROα and anti-MCP-1 antibodies. Binding of β1 integrin receptors was assessed using integrin binding assays. Cytoskeletal assembly/disassembly in RASFs and HDECs were assessed by immunofluorescence staining for F-actin. IL-17A-induced cell migration and cytoskeletal disassembly were assessed in the presence of a Rac1 inhibitor (NSC23766). Rac1 activation following IL-17 stimulation in the presence or absence of anti-GROα, anti-MCP-1, or IgG control was assessed by Rac GTPase pull-down assays and Western blotting. RESULTS IL-17A significantly up-regulated angiogenesis and endothelial cell invasion. It significantly induced GROα and MCP-1 expression in RASFs. Migration of PBMCs, RASFs, and HDECs was induced by IL-17A; these effects were blocked by anti-GROα or anti-MCP-1 antibodies. IL-17A significantly up-regulated β1 integrin receptor binding and induced cytoskeletal disassembly in RASFs and HDECs. Rac1 activation was directly induced by IL-17A. IL-17A-induced wound repair and actin rearrangement were inhibited by a pharmacologic inhibitor of Rac1 (NSC23766). Anti-GROα or anti-MCP-1 antibodies had no effect on IL-17A-induced Rac1 activation. CONCLUSION IL-17A induces angiogenesis, cell migration, and cell invasion, all of which are key processes in the pathogenesis of rheumatoid arthritis and ones that are mediated in part through chemokine- and cytoskeleton-dependent pathways.

Notch signalling pathways mediate synovial angiogenesis in response to vascular endothelial growth factor and angiopoietin 2

Objective Notch signalling pathways are critical for angiogenesis and endothelial cell (EC) fate; however the mechanisms regulating these processes in the inflamed joint remain to be elucidated. Here, we examine whether Notch signalling mediates vascular endothelial growth factor (VEGF) and angiopoietin 2 (Ang2)-induced vascular function. Methods Notch-1 intracellular domain (Notch-1 IC), Notch-4 IC, Delta-like-ligand 4, Hes-related transcriptional repressors-1 and 2 (Hrt-1, Hrt-2) mRNA and/or protein expression was measured by Real-time PCR and/or western blot. VEGF/Ang2 induced EC function was assessed using transwell invasion chambers, matrigel tube formation assays and wound repair scratch assays ± Notch-1 siRNA or an γ-secretase inhibitor N-(N-(3,5-Difluorophenacetyl-L-alanly))-S-phenylglycine-t-Butyl Ester (DAPT) in RA synovial explants or human microvascular EC. Interleukin (IL)-6 and IL-8 were measured by ELISA and MMP2 and 9 by gelatine zymography. Results Notch-1 IC and Notch-4 IC protein expressions were demonstrated in RA and psoriatic arthritis synovial biopsies, with minimal expression observed in Osteoarthritis (OA). VEGF and Ang2 induced Notch-1 IC/ Notch-4 IC protein expression in synovial explant cultures and human microvascular EC levels were further potentiated by VEGF/Ang2 stimulation in combination. Notch-1, Delta-like-ligand 4, and Hrt-2 mRNA expression were significantly induced by VEGF and Ang2 alone and in combination. Furthermore VEGF/Ang2-induced EC invasion, angiogenesis and migration were inhibited by Notch-1 siRNA or DAPT. Conditioned media from VEGF/Ang2 stimulated RA synovial explants induced EC tube formation, an effect that was inhibited by DAPT. Finally, DAPT significantly decreased VEGF/Ang2 induced IL-6, IL-8, MMP2 and 9 expressions in RA synovial explants. Conclusions Notch-1 mediates VEGF/Ang2-induced angiogenesis and EC invasion in inflammatory arthritis.