TNF and rheumatoid arthritis: A KEGG pathway analysis of the upregulated genes group was also executed; the top pathways associated with the upregulated genes on chondrocytes cultured on HA are illustrated in Fig. 2B. Upregulated KEGG pathways include the Pl3K-Akt signaling pathway, glutathione metabolism, TNF signaling pathway, FoxO signaling pathway, as well as rheumatoid arthritis.