Abstract:

Objective To find the biomarkers of rheumatoid arthritis（RA） through bioinformatics analysis and experimental verification. Methods Transcriptome microarray data（GSE12021 and GSE55235）of RA and osteoarthritis（OA） were downloaded from Gene Expression Omnibus（GEO） database，and differentially expressed genes（DEG） were screened. Enrichment analysis was conducted using Kyoto Encyclopedia of Genes and Genomes（KEGG） and Gene Ontology（GO） pathways，and the protein-protein interaction（PPI） network was constructed to identify hub genes. Peripheral blood mononuclear cell（PBMC） samples of 30 patients with RA（RA group），30 patients with OA（OA group） and 30 healthy subjects（healthy control group） who were admitted to Wuxi Ninth People's Hospital from March 2023 to September 2023 were collected to verify the expression level of hub genes，and receiver operating characteristic（ROC） curve was constructed to evaluate the diagnostic efficiency of the hub genes. Spearman correlation analysis was used to evaluate the correlation between hub genes and clinical RA symptom evaluation indicators，including tender joint count（TJC），swollen joint count（SJC） and 28-joint disease activity score-erythrocyte sedimentation rate（DAS28-ESR） score. Results A total of 120 DEG were screened，of which 56 were up-regulated and 64 were down-regulated. The results of GO and KEGG pathway enrichment analysis indicated that the DEG mostly enriched in biological processes such as immune regulation，leukocyte proliferation，adaptive immunity，signal pathway mediated by cytokines and chemokines and so on. Three hub genes [C-X-C motif chemokine ligand（CXCL） 9，CXCL11 and guanylate binding protein 1（GBP1）] were identified by PPI network. The relative expression of CXCL9 in PMBC in RA group was higher than those in OA group and healthy control group（P<0.01），and the relative expression of CXCL11 in PMBC in RA group was higher than that in healthy control group（P<0.05）. There was no statistical significance in the relative expression of GBP1 among the 3 groups（P>0.05）. ROC curve analysis showed that the areas under curves（AUC） of relative expression of CXCL9 in diagnosing RA were 0.890 and 0.660，respectively，compared with healthy control group and OA group. Correlation analysis showed that the relative expression of CXCL9 was positively correlated with TJC，SJC and DAS28-ESR score（r values were 0.604 6，0.752 6 and 0.789 6，respectively，P<0.001）. Conclusions The expression of CXCL9 in PMBC of RA patients is increased，which was related to the severity of RA. CXCL9 may be a potential diagnostic marker of RA.

Key words: C-X-C motif chemokine ligand 9, Rheumatoid arthritis, Bioinformatics, Diagnostic marker, Clinical specimen