CCL4 and intervertebral disk degenerative disorder: Previous investigations have shown that expression levels of IL-6, IL-8, CCL3 and CCL4 increase in degenerate IVDs where they appear to play pivotal roles in disc tissue remodelling and nerve sensitisation [55,56,57]; furthermore, serum levels of IL-6, IL-8 and CCL3 are elevated in patients with disc degeneration, and the release of a cytokine cocktail from disc cells can also activate a pro-inflammatory response from bone marrow cells, which could potentially lead to the development of Modic changes [45,58,59].