Unknown,Transcriptomics,Genomics,Proteomics

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Serum Follistatin-Like Protein 1 Is a Biomarker for Macrophage Activation Syndrome and May Predict Disease Course in Systemic Juvenile Idiopathic Arthritis

ABSTRACT: Objective. Follistatin-like protein 1 (FSTL-1) is a secreted glycoprotein that is over-expressed in certain inflammatory diseases. Our objective in this study was to correlate FSTL-1 levels with measures of clinical disease activity in systemic juvenile idiopathic arthritis (sJIA), including macrophage activation syndrome (MAS). Methods. FSTL-1 serum levels were measured by ELISA in 28 patients with sJIA, including 7 patients who developed MAS, as well as in 30 normal controls. Levels were correlated with erythrocyte sedimentation rate (ESR), ferritin and sIL-2Rα expression. Differential gene expression based on FSTL-1 levels was analyzed in peripheral blood mononuclear cells (PBMCs). Results. FSTL-1 serum levels were elevated at time of presentation (pre-treatment) of sJIA (mean 200.7 ng/ml) and decreased to normal (mean 133.7 ng/ml) over 24 months (p<0.01). FSTL-1 levels were markedly elevated during acute MAS (mean 279.8 ng/ml) and decreased to normal (mean 120.3 ng/ml) following treatment (p<0.001). FSTL-1 levels correlated with serum markers of inflammation, including sIL-2Rα and ferritin, in patients with MAS. PBMCs from patients with FSTL-1 levels >200 ng/ml showed an increase in expression of genes related to innate immunity and erythropoiesis, and decrease in NK cell function. Patients with the highest FSTL-1 levels at disease onset (>300 ng/ml) ultimately required cyclosporine treatment. Conclusion. In patients with sJIA, serum FSTL-1 is a biomarker for MAS and FSTL-1 levels at presentation may predict subsequent disease course. Patients with FSTL-1 levels >200 ng/ml had altered gene expression patterns suggestive of subclinical MAS and may represent a subgroup of sJIA with more severe disease. FSTL-1 serum levels were measured by ELISA in 28 patients with sJIA, including 7 patients who developed MAS, as well as in 30 normal controls. Levels were correlated with erythrocyte sedimentation rate (ESR), ferritin and sIL-2Rα expression. Differential gene expression based on FSTL-1 levels was analyzed in peripheral blood mononuclear cells (PBMCs). Only 11 patients were run on microarray.

ORGANISM(S): Homo sapiens

SUBMITTER: Michael Barnes

PROVIDER: E-GEOD-38849 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Systemic juvenile idiopathic arthritis (SJIA) is a chronic childhood arthropathy with features of autoinflammation. Early inflammatory SJIA is associated with expansion and activation of neutrophils with a sepsis-like phenotype, but neutrophil phenotypes present in longstanding and clinically inactive disease (CID) are unknown. The objective of this study was to examine activated neutrophil subsets, S100 alarmin release, and gene expression signatures in children with a spectrum of SJIA disease activity. Methods: Highly-purified neutrophils were isolated using a two-step procedure of density-gradient centrifugation followed by magnetic-bead based negative selection prior to flow cytometry or cell culture to quantify S100 protein release. Whole transcriptome gene expression profiles were compared in neutrophils from children with both active SJIA and CID. Results: Patients with SJIA and active systemic features demonstrated a higher number of CD16+CD62Llo neutrophil population compared to controls. This neutrophil subset was not seen in patients with CID or patients with active arthritis not exhibiting systemic features. Using imaging flow cytometry, CD16+CD62Llo neutrophils from patients with active SJIA and features of macrophage activation syndrome (MAS) had increased nuclear hypersegmentation compared to CD16+CD62L+ neutrophils. Serum levels of S100A8/A9 and S100A12 were strongly correlated with peripheral blood neutrophil counts. Neutrophils from active SJIA patients did not show enhanced resting S100 protein release; however, regardless of disease activity, neutrophils from SJIA patients did show enhanced S100A8/A9 release upon PMA stimulation compared to control neutrophils. Furthermore, whole transcriptome analysis of highly purified neutrophils from children with active SJIA identified 214 differentially expressed genes compared to neutrophils from healthy controls. The most significantly upregulated gene pathway was Immune System Process, including AIM2, IL18RAP, and NLRC4. Interestingly, this gene set showed intermediate levels of expression in neutrophils from patients with long-standing CID yet persistent serum IL-18 elevation. Indeed, all patient samples regardless of disease activity demonstrated elevated inflammatory gene expression, including inflammasome components and S100A8. Conclusion: We identify features of neutrophil activation in SJIA patients with active disease and CID, including a proinflammatory gene expression signature, reflecting persistent innate immune activation. Taken together, these studies expand understanding of neutrophil function in chronic autoinflammatory disorders such as SJIA.

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Serum Follistatin-Like Protein 1 Is a Biomarker for Macrophage Activation Syndrome and May Predict Disease Course in Systemic Juvenile Idiopathic Arthritis

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