CXCR4 and osteoarthritis: RASFsn-stimulated chondrocytes showed an increased expression of CXCL1–3 (growth-related oncogene α-γ; Groα-γ), CXCL8 (IL8), CCL20 (macrophage inflammatory protein-β; MIP-1β) and the chemokine receptor CXCR4. CXCL1 has been described to initiate apoptosis in osteoarthritis chondrocytes and induces MMP-3 secretion acting through CXCR2 [53]; CXCL8 has powerful neutrophil chemotactic properties [54], and CXCR4 and CCL20 enhance the release of matrix-degrading enzymes [50,55,56].