Regulatory Mechanisms of IL-19 Modulated Pathways in Osteoarthritis Progression: A Combined Analysis of Differential Gene Expression and WGCNA

Abstract

Background: Osteoarthritis (OA) is a common chronic degenerative disease, and its incidence has risen in recent years. However, the specific pathogenesis of OA remains unclear. Studies have shown that interleukin-19 (IL-19) has an inhibitory effect on inflammation caused by colitis, psoriasis, and myocardial infarction. However, whether IL-19 has an inhibitory effect on OA caused by excessive inflammatory mediators is still unknown. This study aimed to investigate the downstream pathway regulation mechanism of IL-19 affecting OA progression by bioinformatics methods. Methods: Differentially expressed genes (DEGs) were identified using R language. Three OA synovial datasets (GSE55235, GSE55457, GSE55584) were downloaded from the Gene Expression Omnibus (GEO) database, including 20 normal and 26 OA synovial tissue samples. After the screening of DEGs, Gene Set Enrichment Analysis (GSEA) was performed. The effects of IL-19 on chondrocytes were detected by real-time fluorescence quantitative polymerase chain reaction (qPCR) and Western blot (WB), respectively, to investigate the gene and protein expression of apoptosis and inflammation factors. And weighted gene co-expression network analysis (WGCNA) was performed, followed by functional analysis. The improved Hulth modeling method was used to construct an OA rats model, and the expression levels of IL-19 and Janus kinase 3 (JAK3) mRNA and protein in synovial tissue were detected using qPCR and Western blot. Results: The immune infiltration of DEGs suggested the primary component of M2 macrophages in immune cells, IL-19 was markedly downregulated in OA, and immunofluorescence indicated the co-localization of IL-19 and M2 macrophages. Furthermore, the results revealed that the inhibition of IL-19 on IL-1β induced chondrocyte apoptosis and the expression of inflammatory cytokines. Following, the WGCNA analysis identified 8 distinct gene modules, among which the MEturquoise module showed a significant correlation with OA and was associated with IL-19 expression. Based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, the PI3K-Akt signaling pathway and Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway, well-known upstream signal pathways of IL-19 were associated with the MEturquoise module. Western blot and qPCR results showed a significant decrease in IL-19 and JAK3 mRNA and protein expression in OA rats. Conclusions: This study revealed the potential role of IL-19 and its upstream JAK3 regulatory pathways in the development of OA using bioinformatics methods.