CCL2 and rheumatoid arthritis: Remarkably, in non-stimulated RA synoviocytes, cultured in the absence of IL-17 or TNF-α, the expression of IL-6, GM-CSF, and IL-8 was reduced by 50–70 % by the presence of BMP6, and to a lesser extent CCL2, MMP-3, and MMP-13 expression was reduced by 40 % (Fig. 6a).