In addition, FLSs can promote various processes in RA by secreting different types of inflammatory cytokines, such as IL-6, IL-8, IL-1β, TNF-α and MCP-1, as well as matrix metalloproteinases (MMPs), such as MMP-1 and MMP-13 [10,11,12,13]. The gene discussed is CCL2; the disease is rheumatoid arthritis.