Screening of Differentially Expressed Genes in Rat Synovitis by Transcriptome Sequencing and in Vitro Verification of Therapeutic Target of Fraxetin

Abstract

ObjectiveUsing transcriptome sequencing to screen the differentially expressed genes between the synovial tissue of rats with knee osteoarthritis (KOA) induced by monosodium iodoacetate (MIA) and that of normal rats, and then screen the target of fraxetin in the treatment of synovitis.MethodsSD rats were divided into KOA group and the negative control (NC) group. Rat right knee KOA model was prepared by MIA knee joint injection in KOA group and none treatments in NC group. Four weeks after modeling, the right knee synovial tissue of rats in each group was taken for transcriptome sequencing. Then the differential gene expression analysis, GO enrichment analysis, KEGG function enrichment analysis and PPI protein network interaction analysis were performed. The synovial macrophage Raw264.7 cells were divided into the control group, lipopolysaccharide (LPS) intervention group and LPS+60 μmol/L fraxetin intervention group, then RNA-sequencing results were verified by qRT-PCR in the three groups.ResultsThe results of differential gene-expression analysis showed that there were 1 730 up-regulated genes and 1 546 down-regulated genes in the KOA group compared with the control group, among which the significantly up-regulated genes were mmp12, Acod1, Acan, Col2a1, Atp6v0d2 (|log2(FoldChange)|≥1, adjusted P<0.01). KEGG cluster analysis and GO cluster analysis showed that differential genes were mainly involved in the regulation of inflammation and immune metabolism, such as tricarboxylic acid cycle and mitochondrial function. The expressions of Acod1 and Atp6v0d2 in Raw264.7 cells after LPS intervention were significantly higher. Compared with the LPS intervention group, the expression level of Atp6v0d2 in Raw264.7 cells after LPS+fraxetin combined intervention was significantly lower.ConclusionAfter modeling KOA induced by MIA, macrophage-related genes mmp12, Acod1 and Atp6v0D2, which mediate inflammation and immune metabolism, were highly expressed in the synovial tissue of rats, suggesting that there might be immune metabolism changes mediated by synovial macrophages during the occurrence and development of KOA. The increased expression of Acod1 and Atp6v0d2 in macrophages Raw264.7 after LPS intervention can preliminarily confirm this result. Among them, Atp6v0d2 may be a potential target of fraxetin in the treatment of synovitis, which provides a new idea for KOA treatment.

Keywords

• osteoarthritis
• transcriptome sequencing
• immunometabolism
• synovial macrophage
• fraxetin