Dominique Baeten

Synovial histopathology of psoriatic arthritis, both oligo- and polyarticular, resembles spondyloarthropathy more than it does rheumatoid arthritis

At present only few biological data are available to indicate whether psoriatic arthritis (PsA) is part of the spondyloarthropathy (SpA) concept, whether it is a separate disease entity or a heterogeneous disease group with oligoarticular/axial forms belonging to SpA and polyarticular forms resembling rheumatoid arthritis (RA). To address this issue with regard to peripheral synovitis, we compared the synovial characteristics of PsA with those of ankylosing spondylitis (AS)/undifferentiated SpA (USpA) and RA, and compared the synovium of oligoarticular versus polyarticular PsA. Synovial biopsies were obtained from patients with RA, nonpsoriatic SpA (AS + USpA), and oligoarticular and polyarticular PsA. The histological analysis included examination(s) of the lining layer thickness, vascularity, cellular infiltration, lymphoid aggregates, plasma cells and neutrophils. Also, we performed immunohistochemical assessments of CD3, CD4, CD8, CD20, CD38, CD138, CD68, CD163, CD83, CD1a, CD146, αVβ3, E-selectin, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, S100A12, intracellular citrullinated proteins and major histocompatibility complex (MHC)–human cartilage (HC) gp39 peptide complexes. Comparing SpA (PsA + AS + USpA) with RA, vascularity, and neutrophil and CD163+ macrophage counts were greater in SpA (P < 0.05), whereas lining layer thickness and the number of CD83+ dendritic cells were greater in RA (P < 0.05). In RA, 44% of samples exhibited positive staining for intracellular citrullinated proteins and 46% for MHC–HC gp39 peptide complexes, whereas no staining for these markers was observed in SpA samples. We excluded influences of disease-modifying antirheumatic drug and/or corticosteroid treatment by conducting systematic analyses of treated and untreated subgroups. Focusing on PsA, no significant differences were observed between PsA and nonpsoriatic SpA. In contrast, vascularity (P < 0.001) and neutrophils were increased in PsA as compared with RA (P = 0.010), whereas staining for intracellular citrullinated proteins and MHC–HC gp39 peptide complexes was exclusively observed in RA (both P = 0.001), indicating that the same discriminating features are found in PsA and other SpA subtypes compared with RA. Exploring synovial histopathology between oligoarticular and polyarticular PsA, no significant differences were noted. Moreover, intracellular citrullinated proteins and MHC–HC gp39 peptide complexes, which are specific markers for RA, were observed in neither oligoarticular nor polyarticular PsA. Taken together, these data indicate that the synovial histopathology of PsA, either oligoarticular or polyarticular, resembles that of other SpA subtypes, whereas both groups can be differentiated from RA on the basis of these same synovial features, suggesting that peripheral synovitis in PsA belongs to the SpA concept.

Immunomodulatory effects of anti-tumor necrosis factor alpha therapy on synovium in spondylarthropathy: histologic findings in eight patients from an open-label pilot study.

OBJECTIVE To assess the effects of treatment with anti-tumor necrosis factor alpha (anti-TNFalpha) on synovial histology in patients with spondylarthropathy (SpA) in order to confirm the effect on peripheral synovitis and to investigate the immunologic mechanisms involved in anti-TNFalpha therapy. METHODS Patients with treatment-resistant SpA were treated with infliximab (5 mg/kg) at weeks 0, 2, and 6 in an open-label pilot study. In 8 patients, synovial biopsy tissues obtained at baseline, week 2, and week 12 were used for histologic and immunohistochemical evaluation. RESULTS In all 8 patients (3 with ankylosing spondylitis, 1 with undifferentiated SpA, and 4 with psoriatic arthritis), there was a clear clinical improvement in the peripheral arthritis after anti-TNFalpha therapy. Histologic analysis of the synovial biopsy tissues indicated that the synovial lining layer thickness tended to decrease, with a significant reduction of CD55+ synoviocytes, at week 12. In the sublining layer, vascularity was reduced at week 12, with a decreased endothelial expression of vascular cell adhesion molecule 1 but not intercellular adhesion molecule 1, platelet endothelial cell adhesion molecule 1, and E-selectin. Although at week 2 and week 12, the number of neutrophils and CD68+ macrophages in the sublining layer was decreased, the overall degree of inflammatory infiltration remained unchanged. This could be related to the lymphocyte infiltration since at week 12, only CD4+ cells (but not CD3+, CD45RO+, and CD8+ cells) tended to decrease, while CD20+ lymphocytes and plasma cells were clearly increased. CONCLUSION The reduction in lining layer thickness, vascularity, and infiltration with neutrophils and macrophages paralleled the beneficial effect of anti-TNFalpha therapy on peripheral synovitis in 8 patients with different subtypes of SpA. The adhesion molecule expression, T cell infiltration, and, most important, B cell infiltration seemed to contrast with previous observations in RA. Although these preliminary data need to be confirmed in a larger cohort, they suggest distinct immunomodulatory mechanisms of anti-TNFalpha in SpA.

Comparative study of the synovial histology in rheumatoid arthritis, spondyloarthropathy, and osteoarthritis: influence of disease duration and activity

OBJECTIVES To compare the macroscopic and microscopic characteristics of synovial tissue in rheumatoid arthritis (RA), spondyloarthropathy (SpA), and osteoarthritis (OA) after exclusion of possible biases induced by disease duration or activity, or both. METHODS Synovial biopsy specimens were obtained by needle arthroscopy in patients with early RA (n=16), late RA (n=14), early SpA (n=23), and OA (n=12). Macroscopic and microscopic features were scored on a four point scale and analysed as a function of disease duration (early versus late RA), local and systemic disease activity, and diagnosis. RESULTS Except for the maximal synovial lining thickness, no significant differences were seen between early and late RA. For disease activity, synovial histology was only weakly correlated with C reactive protein in RA, but seemed to be strongly dependent on effusion of the biopsied joint in all disease groups. After stratification for local disease activity, no disease related differences were found in patients without joint effusion. In contrast, important differences were found between patients with RA and SpA with active joint effusion. Synovial vascularity was macroscopically increased in SpA versus RA (p=0.017). A straight vessel pattern was only seen in RA, while tortuous vessels were preferentially seen in SpA. Vascularity was also microscopically increased in SpA compared with RA (p=0.031), and correlated with the macroscopic vascularity (rs =0.36, p=0.036). CD3+ (p=0.008), CD4+ (p=0.008), and CD20+ (p=0.024) lymphocytes were overrepresented in RA compared with SpA. The integrin expression in RA was characterised by a decrease of αVβ3 in the synovial lining (p=0.006) and an increase of αVβ5 in the sublining (p<0.001). CONCLUSIONS The immune architecture of the synovial membrane is more dependent on local disease activity than on disease duration. Synovium obtained from clinically affected joints shows important histological differences between RA and SpA.

Modulation of CCR2 in rheumatoid arthritis: a double-blind, randomized, placebo-controlled clinical trial.

OBJECTIVE CCR2 is a chemokine receptor expressed by monocytes, macrophages, and a subset of T cells. Its ligand, CCL2 (monocyte chemotactic protein 1), is abundantly present in the synovium of patients with rheumatoid arthritis (RA). Blocking CCR2 prevents CCL2-mediated chemotaxis in vitro and modulates arthritis in animal models of RA. In this study we examined the effects of CCR2 blockade on synovial inflammation in RA. METHODS The study was designed as a phase IIa clinical trial with a human CCR2 blocking antibody (MLN1202) in patients with active RA. Thirty-two patients received 3 infusions, over a period of 6 weeks, with either placebo (n = 9) or anti-CCR2 monoclonal antibody at 0.5 mg/kg (n = 7), 1.5 mg/kg (n = 7), or 4.0 mg/kg (n = 9). Safety was monitored with laboratory tests, immunotoxicity assessments, and documenting of adverse events, and European League Against Rheumatism and American College of Rheumatology response criteria were used to assess clinical improvement. Synovial tissue was obtained at baseline and after 43 days of treatment, for pharmacodynamic analysis using immunohistochemistry and digital image analysis. The Kruskal-Wallis test was used to compare groups, and the Wilcoxon signed rank test was used to assess changes within the groups. RESULTS All patients completed the study. Treatment with CCR2 blocking antibody reduced the levels of free CCR2 on CD14+ monocytes by at least 57% and up to 94% (P < 0.001), demonstrating the biologic activity of the compound. However, there was no reduction in the levels or expression of any of the synovial biomarkers. Accordingly, no clinical improvement was observed. CONCLUSION Treatment with anti-CCR2 blocking antibody did not result in amelioration of synovial inflammation in active RA. The results do not support the notion that blockade of CCR2 may be sufficient to induce clinical improvement in RA.

Macrophages expressing the scavenger receptor CD163: a link between immune alterations of the gut and synovial inflammation in spondyloarthropathy.

The objective of this study was to investigate CD163+ macrophages in the synovial membrane of patients with spondyloarthropathy (SpA). Immunohistochemistry was performed on synovium of 17 SpA and 18 rheumatoid arthritis (RA) patients, on colonic biopsies of 16 SpA patients and ten healthy controls, and on paired synovial biopsies of eight SpA patients, before and after anti‐TNFα therapy. Phenotype and cytokine production were analysed by flow cytometry. CD163+ macrophages were increased in the synovial lining and sublining in SpA versus RA, as well as in colonic lamina propria in SpA versus controls. The number of CD163+ macrophages in the synovial sublining correlated with C‐reactive protein levels and erythrocyte sedimentation rate. Paralleling the increase of CD163, HLA‐DR was increased in the synovial lining and sublining of SpA. In contrast, the co‐stimulatory molecules CD80 and CD86 and the dendritic cell markers CD1a and CD83 were scarce in SpA synovium. Flow cytometry indicated that CD163+ macrophages expressed high levels of HLA‐DR and could produce in vitro tumour necrosis factor α (TNFα) but not interleukin‐10 (IL‐10). Finally, anti‐TNFα therapy in vivo induced a decrease of CD163+ macrophages in the synovial lining and sublining. In conclusion, macrophages expressing the scavenger receptor CD163 are increased in synovium and in colonic mucosa in SpA, highlighting the relationship between joint and gut in this disease. The correlation with inflammatory parameters, the expression of HLA‐DR, the production of TNFα but not IL‐10, and the reduction by anti‐TNFα therapy support a role for CD163+ macrophages in the synovial inflammation in SpA. Copyright

Human cartilage gp-39+,CD16+ monocytes in peripheral blood and synovium: correlation with joint destruction in rheumatoid arthritis.

OBJECTIVE To investigate the expression of human cartilage (HC) gp-39, a possible autoantigen in rheumatoid arthritis (RA), in peripheral blood and synovium, to characterize its cellular source, and to analyze correlations with clinical features. METHODS The expression of HC gp-39 in synovium and peripheral blood mononuclear cells (PBMC) was assessed by immunohistochemistry and flow cytometry. Synthesis and secretion were investigated by both reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. RESULTS PBMC expressing HC gp-39 were increased in RA patients compared with spondylarthropathy patients (P = 0.0029) and with healthy control subjects (P = 0.0013). HC gp-39+ cells were also slightly overrepresented in RA synovium (P = 0.01). In both blood and synovium, HC gp-39+ cells were identified as CD14dim,CD16+ monocytes, a phenotype which can differentiate from classic CD14++ monocytes by maturation in vitro. HC gp-39 messenger RNA was detected in RA synovium and PBMC, and PBMC secreted HC gp-39 in vitro. The number of HC gp-39+ PBMC correlated with serum levels of C-reactive protein (r = 0.39, P = 0.003) and HC gp-39 (r = 0.52, P = 0.014). HC gp-39 expression in RA synovial lining correlated with joint destruction (r = 0.77, P < 0.001). CONCLUSION CD16+ monocytes, a cellular source of HC gp-39 in vivo, are overrepresented in both RA peripheral blood and synovial tissue. The presence of HC gp-39+ cells in RA synovium is correlated with the degree of joint destruction. These data support a role of these cells in the local autoimmune response that leads to chronic inflammation and joint destruction.

Fibrin Deimination in Synovial Tissue Is Not Specific for Rheumatoid Arthritis but Commonly Occurs during Synovitides

Autoantibodies to deiminated (citrullinated) proteins are the most specific serological markers of rheumatoid arthritis (RA). Deimination is critical in generating the peptidic epitopes they recognize. In the synovial tissue (ST), deiminated forms of the α- and β-chains of fibrin are their major autoantigenic targets (anti-human fibrin(ogen) autoantibodies (AhFibA)). We investigated whether the presence of deiminated fibrin in the ST was specific for RA, because this could explain why AhFibA are RA specific. In 13 patients with RA and 19 patients with various other rheumatological disorders, knee ST biopsies were collected in macroscopically inflamed areas identified under arthroscopy. Synovitis was histopathologically confirmed in all of the biopsies. By immunoblotting, using antisera to fibrin, Abs to citrullyl residues, and AhFibA purified from RA sera, deiminated fibrin was evidenced in ST extracts from all of the patients. Moreover, variations in the degree of fibrin deimination were observed that were not related to the disease. Immunohistochemical analysis, using Abs to citrullyl residues and an antiserum to fibrin on adjacent serial sections of ST, confirmed the results because deiminated proteins colocalized with fibrin in RA as well as in control patients. Therefore, fibrin deimination in the ST is a general phenomenon associated to any synovitis, which does not necessarily induce a B autoimmune response with production of AhFibA.

Infiltration of the synovial membrane with macrophage subsets and polymorphonuclear cells reflects global disease activity in spondyloarthropathy

Considering the relation between synovial inflammation and global disease activity in rheumatoid arthritis (RA) and the distinct but heterogeneous histology of spondyloarthropathy (SpA) synovitis, the present study analyzed whether histopathological features of synovium reflect specific phenotypes and/or global disease activity in SpA. Synovial biopsies obtained from 99 SpA and 86 RA patients with active knee synovitis were analyzed for 15 histological and immunohistochemical markers. Correlations with swollen joint count, serum C-reactive protein concentrations, and erythrocyte sedimentation rate were analyzed using classical and multiparameter statistics. SpA synovitis was characterized by higher vascularity and infiltration with CD163+ macrophages and polymorphonuclear leukocytes (PMNs) and by lower values for lining-layer hyperplasia, lymphoid aggregates, CD1a+ cells, intracellular citrullinated proteins, and MHC–HC gp39 complexes than RA synovitis. Unsupervised clustering of the SpA samples based on synovial features identified two separate clusters that both contained different SpA subtypes but were significantly differentiated by concentration of C-reactive protein and erythrocyte sedimentation rate. Global disease activity in SpA correlated significantly with lining-layer hyperplasia as well as with inflammatory infiltration with macrophages, especially the CD163+ subset, and with PMNs. Accordingly, supervised clustering using these synovial parameters identified a cluster of 20 SpA patients with significantly higher disease activity, and this finding was confirmed in an independent SpA cohort. However, multiparameter models based on synovial histopathology were relatively poor predictors of disease activity in individual patients. In conclusion, these data indicate that inflammatory infiltration of the synovium with CD163+ macrophages and PMNs as well as lining-layer hyperplasia reflect global disease activity in SpA, independently of the SpA subtype. These data support a prominent role for innate immune cells in SpA synovitis and warrant further evaluation of synovial histopathology as a surrogate marker in early-phase therapeutic trials in SpA.

Needle Arthroscopy of the Knee with Synovial Biopsy Sampling: Technical Experience in 150 Patients

Abstract: Needle arthroscopy is an office-based technique allowing direct visualisation of the knee cavity and selective sampling of the synovial membrane. We performed needle arthroscopy in 150 patients with synovitis of the knee (1) to evaluate the diagnostic potential in early arthritis, (2) to perform therapeutic lavage in persistent inflammatory synovitis and (3) to assess the balance between technical feasibility, safety and patient comfort on the one hand, and the relevance of the obtained macro- and microscopic information for diagnosis and research purposes on the other. After disinfection of the leg and local anaesthesia of the skin and joint, a 1.8–2.7 mm needle arthroscope was introduced into the knee. Synovial fluid was aspirated and lavage of the joint cavity was performed to allow macroscopic evaluation of hyperaemia and hypertrophy of the synovial membrane. Biopsies were taken at inflamed sites, followed by another lavage to remove blood and debris. Needle arthroscopy of the knee is a simple and easy to perform technique made particularly attractive by the local anaesthesia and the ambulatory setting. It allows good macroscopic evaluation of synovial inflammation and selective sampling of the synovial membrane. Biopsies are suitable for RNA and DNA extraction, bacterial or lymphocyte culture, and cell isolation. Because samples were sometimes too small for representative histology, we switched from a 1.8 mm to a 2.7 mm biopsy forceps with good results. In nearly all cases the arthroscopy was well tolerated. Moreover, some patients reported relief of symptoms and even improvement of mobility after lavage of the inflamed joint. No major complications were noted. It was concluded that needle arthroscopy of the knee is a simple, safe and well-tolerated technique, with promising perspectives as a diagnostic, scientific and possibly therapeutic tool in rheumatic diseases.

Differential expression and response to anti‐TNFα treatment of infiltrating versus resident tissue macrophage subsets in autoimmune arthritis

Synovial macrophages play a pivotal role in the pathogenesis of chronic autoimmune arthritis by contributing to local inflammation and tissue damage and are therefore a primary target for therapeutic intervention. The aim of the present study was to investigate in more detail the relative contribution of different synovial macrophage subsets with potentially different inflammatory or anti‐inflammatory functions by analysing the two most frequent forms of human autoimmune arthritis, spondyloarthropathy (SpA) and rheumatoid arthritis (RA). Both infiltrating macrophages from peripheral blood expressing myeloid‐related proteins (MRP) 8 and 14, and resident tissue macrophages expressing CD163 were abundant in inflamed synovium. Whereas the global number of synovial macrophages was similar in both diseases, infiltrating macrophages were increased in the RA lining layer in contrast with resident tissue macrophages, which were more frequently observed in SpA. Soluble MRP8/MRP14 complexes, which were secreted locally in the joint during the infiltration process, were increased in the serum of arthritis patients and, in contrast with soluble CD163 shed from resident tissue macrophages, correlated well with global inflammatory parameters. Treatment in vivo with anti‐TNFα had a rapid and pronounced effect on the infiltration of MRP‐positive macrophages into tissues, as evidenced by histopathological analysis and serum MRP8/MRP14 levels. Taken together, these data support an important role for infiltrating versus resident tissue macrophages in human autoimmune synovitis and indicate that macrophage products such as soluble MRP8/MRP14 complexes are valuable biomarkers for the experimental and clinical monitoring of specific disease mechanisms in vivo. Copyright