SDF-1 is a chemokine that is upregulated in response to hypoxia in RA (Hitchon et al., 2002; Santiago et al., 2011), and is involved in a number of pathogenic events such as increased synovitis, angiogenesis, bone erosion, and cartilage destruction (Villalvilla et al., 2014). Here, CXCL12 is linked to rheumatoid arthritis.