RNA sequencing analysis reveals differential gene expression of CXCL2 in ACPA-positive and ACPA-negative rheumatoid arthritis

Abstract

Background. Anti-citrullinated protein/peptide antibodies (ACPA) play important roles in the pathogenesis of rheumatoid arthritis (RA), and are associated with RA severity. It has been suggested that ACPA-positive (ACPA+) and ACPA-negative (ACPA-) RA are different disease subsets with distinct differences in genetic variation and clinical outcomes. The aims of the present study were to compare gene expression profiles in ACPA + and ACPA- RA and identify novel candidate gene signatures that might serve as therapeutic targets. Methods. Comprehensive transcriptome analysis of peripheral blood mononuclear cells (PBMCs) from ACPA + and ACPA- RA patients, and healthy controls was performed via RNA sequencing. Genes with significantly different expressions were analyzed by cluster analysis, Gene Ontology analysis and Ingenuity Pathway analysis. A validation cohort was used to further investigate differentially expressed genes via real-time PCR and enzyme-linked immunosorbent assay. Spearman's correlation test was used to evaluate the correlation of differentially expressed genes and the clinical and laboratory data of the patients. The role of differentially expressed genes in osteoclastogenesis was further investigated. Results. There were significant differences in the expression levels of both genes and gene isoforms between ACPA + and ACPA- RA samples. Expression of C-X-C motif chemokine ligand 2 (CXCL2) was significantly increased in ACPA + RA patients than in ACPA- RA patients and healthy controls. Validation of candidate genes expression showed that CXCL2 levels in PBMCs and serum were higher in ACPA + RA patients than in ACPA- RA patients and healthy controls. CXCL2 promoted the migration of CD14 + monocytes and increased osteoclast differentiation in RA patients. RAW264.7 macrophages were used to investigate specific mechanisms, and the results suggested that CXCL2 stimulated osteoclastogenesis via ERK MAPK and NFκB pathways. Conclusion. Novel pathways associated with ACPA + RA were identified via RNA sequencing, and CXCL2 was highly expressed in ACPA + RA than in ACPA- RA. These results reveal a previously unreported role of CXCL2 during osteoclastogenesis in RA, and suggest that the blockade of CXCL2 might be a novel strategy for the treatment of RA.