Synovial Immunohistological Biomarkers of the Classification of Undifferentiated Arthritis Evolving to Rheumatoid or Psoriatic Arthritis.

Background: Undifferentiated arthritis (UA) is defined as an inflammatory arthritis that does not fulfill criteria for a definite diagnosis. Delay in reaching a specific diagnostic and therapy may lead to impaired functional outcomes. Our aim was to identify synovial biomarkers associated with definitive diagnostic classification in patients with UA. Methods: DMARD-naïve UA patients with available initial synovial tissue (ST) and a final diagnosis of rheumatoid arthritis (RA) or psoriatic arthritis (PsA) during follow-up were included and compared with patients with well-defined disease (RA or PsA). Clinical, arthroscopic, and pathological data were compared between groups. Pathology included quantitative immunohistochemical (IHC) analysis of cell types and human interferon-regulated MxA. Principal component analysis (PCA) was performed to extract disease patterns. Results: One hundred and five patients were included: 31 patients with DMARD-naïve UA (19 evolving to RA and 12 to PsA during a median follow up of 7 years), 39 with established RA, and 35 with established PsA. ST from the UA group showed higher macrophage density compared with the established RA and PsA groups. Patients with UA evolving to RA (UA-RA) showed higher MxA expression and CD3+ T-cell density compared with established RA. UA patients evolving to PsA (UA-PsA) showed increased vascularity and lining synovial fibroblast density compared with established PsA. Synovitis of UA-PsA patients showed more mast cells and lining fibroblasts compared with UA-RA. No between-group differences in local or systemic inflammation markers were found. Conclusions: Our results show differences in the cellular composition of UA synovium compared with RA and PsA, with higher density of the cellular infiltrate in the UA groups. Initial expression of the interferon inducible gene MxA could be a biomarker of progression to RA, while higher mast cell and fibroblastic density may be associated with PsA progression.

Immunopathologic characterization of ultrasound-defined synovitis in rheumatoid arthritis patients in clinical remission.

BACKGROUND: Patients with rheumatoid arthritis (RA) in clinical remission may have ultrasound-defined synovitis according to the presence of power Doppler (PD) signal. The objective was to describe the immunopathologic characteristics of ultrasound-defined synovitis compared with synovitis in patients with clinically active RA. METHODS: We included between 6 and 8 ultrasound-guided synovial biopsies per patient from 20 patients with RA in clinical remission (DAS28-ESR <2.6) with PD signal, 22 synovial tissue samples (ST) from patients with clinically active RA (swollen joint with confirmed inflammatory synovial fluid) as inflammatory controls, and 10 ST from non-inflammatory controls. Immunostaining for CD3 (T lymphocytes), CD20 (B lymphocytes), CD68 (macrophages), CD117 (mast cells), hsp47 (fibroblasts), bFGF and CXCL12 (angiogenic factors) was made and quantified by digital image analysis. The number of CD31 vessels/mm(2) was quantified. RESULTS: RA patients in remission with PD signal had significantly reduced synovial T-cell, B-cell, mast cell and fibroblast density, but similar macrophage infiltration compared with patients with clinically active RA. Vascularity, bFGF and CXCL12 were partially reduced in RA patients in remission with PD signal compared to those with active RA, but were significantly higher compared with ST from non-inflammatory controls. During the 12-month follow up, 8/20 RA patients (40 %) lost remission: all had synovial hypertrophy grade ≥2 and significantly more synovial B cells and mast cells than patients maintaining remission. CONCLUSIONS: Asymptomatic ultrasound-defined synovitis and clinically active arthritis differ in the degree of infiltrating lymphoid, mast cells and fibroblast density, but are similar with respect to macrophage infiltration. Persistently increased angiogenic factor expression and vascularity may explain the persistence of a PD signal.

CD271(+) stromal cells expand in arthritic synovium and exhibit a proinflammatory phenotype.

BACKGROUND: CD271(+) stromal cells (SCs) with multipotent stem cell capacity have been identified in synovial tissues, but their functional significance is unknown. We analyzed the distribution of CD271(+) cells in inflammatory synovial tissues as well as their ex vivo immunomodulatory and inflammatory phenotypes. METHODS: CD271 expression was analyzed by immunohistochemistry in synovial tissues and by flow cytometry in primary adherent synovial cell cultures from rheumatoid arthritis (RA), osteoarthritis (OA), and non-inflammatory control tissues. Isolation of CD271(+) synovial SCs was carried out by magnetic cell sorting. Allogeneic T-cell/SC cocultures were performed to analyze the regulatory capacity of these cells on T-cell proliferation and cytokine production. The production of inflammatory mediators was analyzed in cultures of sorted CD271(+)/(-) SCs. The capacity of CD271(+)/(-) SCs to induce inflammatory cell recruitment in vivo was evaluated in subcutaneous implants in immunodeficient mice. RESULTS: CD271(+) SC were detected in non-inflammatory as well as in arthritic synovial tissues with a specific perivascular distribution. CD271(+) SC density was increased in RA and OA compared with normal synovial tissues. T-cell proliferation and cytokine synthesis were similarly modified by CD271(+) and CD271(-) SCs. Sorted CD271(+) SCs from OA synovial tissues released significantly more interleukin (IL)-6, matrix metalloproteinase (MMP)-1, and MMP-3 than CD271(-) SCs. In immunodeficient mice, implants of CD271(+) SCs induced significantly higher myeloid cell infiltration than CD271(-) SCs. CONCLUSIONS: Our results demonstrate that CD271(+) perivascular SCs expand in RA and OA synovial tissues. CD271(+) cells showed enhanced proinflammatory properties ex vivo and in vivo, whereas immunoregulatory properties were equivalent in CD271(+) and CD271(-) SC.

Clinicopathological correlations of podoplanin (gp38) expression in rheumatoid synovium and its potential contribution to fibroblast platelet crosstalk.

INTRODUCTION: Synovial fibroblasts (SF) undergo phenotypic changes in rheumatoid arthritis (RA) that contribute to inflammatory joint destruction. This study was undertaken to evaluate the clinical and functional significance of ectopic podoplanin (gp38) expression by RA SF. METHODS: Expression of gp38 and its CLEC2 receptor was analyzed by immunohistochemistry in synovial arthroscopic biopsies from RA patients and normal and osteoarthritic controls. Correlation between gp38 expression and RA clinicopathological variables was analyzed. In patients rebiopsied after anti-TNF-α therapy, changes in gp38 expression were determined. Platelet-SF coculture and gp38 silencing in SF were used to analyze the functional contribution of gp38 to SF migratory and invasive properties, and to SF platelet crosstalk. RESULTS: gp38 was abundantly but variably expressed in RA, and it was undetectable in normal synovial tissues. Among clinicopathologigal RA variables, significantly increased gp38 expression was only found in patients with lymphoid neogenesis (LN), and RF or ACPA autoantibodies. Cultured synovial but not dermal fibroblasts showed strong constitutive gp38 expression that was further induced by TNF-α. In RA patients, anti-TNF-α therapy significantly reduced synovial gp38 expression. In RA synovium, CLEC2 receptor expression was only observed in platelets. gp38 silencing in cultured SF did not modify their migratory and invasive properties but reduced the expression of IL-6 and IL-8 genes induced by SF-platelet interaction. CONCLUSIONS: In RA, synovial expression of gp38 is strongly associated to LN and it is reduced after anti-TNF-α therapy. Interaction between gp38 and CLEC2 platelet receptor is feasible in RA synovium in vivo and can specifically contribute to gene expression by SF.

Topical vitamin D analogue calcipotriol reduces skin fibrosis in experimental scleroderma.

Vitamin D analogues can reduce TGF-ß pro-fibrotic signaling in dermal fibroblasts, but they may also induce a potentially pro-fibrotic thymic stromal lymphopoietin (TSLP)-dependent Th2 cytokine local response. We have analyzed the net effect of topical vitamin D analogue calcipotriol (CPT) on the cytokine profile and the development of fibrosis in experimental model of bleomycin-induced fibrosis. Mice were simultaneously treated with topical CPT or vehicle cream and skin fibrosis was measured by collagen deposition, Masson's trichrome staining and hydroxyproline content. Cytokine and TSLP gene expression was evaluated by quantitative RT-PCR. We showed that in bleomycin injected skin, CPT administration significantly enhanced TSLP and IL-13 gene expression, but did not modify the expression of other cytokines. Skin fibrosis and hydroxyproline content were significantly reduced in CPT compared to vehicle-treated mice. In normal skin, topical administration of CPT lacked a direct pro-fibrotic effect. Our results demonstrate that topical CPT superinduces the expression of the TSLP/IL-13 Th2 axis in fibrotic skin, but it has a net anti-fibrotic effect. These data support the therapeutic use of topical vitamin D analogues for skin fibrosis.