Soluble markers of B cell activation suggest a role of B cells in the pathogenesis of systemic sclerosis-associated pulmonary arterial hypertension.

Introduction: Soluble markers of B cell activation are interesting diagnostic and prognostic tools in autoimmune diseases. Data in systemic sclerosis (SSc) are scarce and few studies focused on their association with disease characteristics. Methods: 1. Serum levels of 14 B cell biomarkers (ß2-microglobulin, rheumatoid factor (RF), immunoglobulins (Ig) G, IgA, IgM, BAFF, APRIL, soluble (s)TACI, sBCMA sCD21, sCD23, sCD25, sCD27, CXCL13) were measured in SSc patients and healthy controls (HC). 2. Associations between these biomarkers and SSc characteristics were assessed. 3. The pathophysiological relevance of identified associations was explored by studying protein production in B cell culture supernatant. Results: In a discovery panel of 80 SSc patients encompassing the broad spectrum of disease manifestations, we observed a higher frequency of RF positivity, and increased levels of ß2-microglobulin, IgG and CXCL13 compared with HC. We found significant associations between several biomarkers and SSc characteristics related to disease phenotype, activity and severity. Especially, serum IgG levels were associated with pulmonary hypertension (PH); ß2-microglobulin with Nt-pro-BNP and DLCO; and BAFF with peak tricuspid regurgitation velocity (TRV). In a validation cohort of limited cutaneous SSc patients without extensive ILD, we observed lower serum IgG levels, and higher ß2-microglobulin, sBCMA, sCD23 and sCD27 levels in patients with pulmonary arterial hypertension (PAH). BAFF levels strongly correlated with Nt-pro-BNP levels, FVC/DLCO ratio and peak TRV in SSc-PAH patients. Cultured SSc B cells showed increased production of various angiogenic factors (angiogenin, angiopoietin-1, VEGFR-1, PDGF-AA, MMP-8, TIMP-1, L-selectin) and decreased production of angiopoietin-2 compared to HC. Conclusion: Soluble markers of B cell activation could be relevant tools to assess organ involvements, activity and severity in SSc. Their associations with PAH could plead for a role of B cell activation in the pathogenesis of pulmonary microangiopathy. B cells may contribute to SSc vasculopathy through production of angiogenic mediators.

Passages in culture and stimulation conditions influence protein expression of primary fibroblasts.

Fibroblasts (Fb) are key effector cells in systemic sclerosis (SSc). Fb stimulation with transforming growth factor beta 1 (TGF-ß1) is considered as a positive control in studies assessing fibrogenesis. The lack of standardization of TGF-ß1 stimulation might be responsible for discrepancies in experiments performed in different conditions. Using quantitative proteomics analysis, we evaluated the impact of changes in experimental conditions on proteomic profiles of primary Fb. Principal component analysis (PCA) identified several groups of differentially expressed proteins influenced by cell passage, culture medium, and both concentration and duration of exposure to TGF-ß1 stimulation. Bioinformatics analysis revealed that late passages expressed proteins involved in senescence. TGF-ß1 concentration and time of stimulation were correlated with the expression of proteins involved in the fibrogenesis and inflammatory processes. These data underline the need for standardization of culture conditions to allow inter-data comparisons in future in vitro studies, especially when using "omics" approaches.

Extended myositis-specific and -associated antibodies profile in systemic sclerosis: A cross-sectional study.

OBJECTIVE: In systemic sclerosis (SSc) and idiopathic inflammatory myopathies (IIM), auto-antibodies are used in daily practice as potent biomarkers of clinical phenotypes. This study aimed at estimating the prevalence of myositis-specific (MSA) and myositis-associated (MAA) auto-antibodies in a well-characterised SSc patients cohort using two different immunoblot assays, and studying their clinical associations. METHODS: In this cross-sectional study, the sera of 300 consecutive patients were tested at the same time with myositis antibodies Euroimmun® and D-tek® immunoblot assays. RESULTS: Prevalence of MSA/MAA, MSA and MAA were 17.0%, 8.0% and 9.7%, respectively. When combining results of both tests, anti-PM/Scl 100 were found in 5.0% (95% confidence interval 2.8; 8.1); anti-PM/Scl 75 and anti-TIF1γ in 3.7% (1.8; 6.5); anti-Ku 3.0% (1.4; 5.6); anti-MDA5 in 1.3% (0.4; 3.4); anti-Mi-2 ß, anti-NXP2, anti-PL-7 and anti-SRP in 0.7% (0.08; 2.4); anti-EJ and anti-PL-12 in 0.3% (0.01; 1.8) of patients. No reactivity against SAE1, Jo-1 or OJ was observed. Anti-PM/Scl 75 antibodies were associated with interstitial lung disease (80% vs. 42%) and myositis (27% vs. 3%); anti-Ku antibodies were associated with myositis (33% vs. 3%). CONCLUSION: In this cross-sectional study of 300 SSc patients, the prevalence of MSA/MAA, MSA and MAA using immunoblot assays were 17.0%, 8.0% and 9.7%, respectively. MAA positivity was associated with ILD and myositis, but this study did not highlight any clinical associations with MSA positivity.