The most investigated MMPs in RA are collagenases (MMP-1, MMP-8 and MMP-13), gelatinases (MMP-2 and MMP-9), MMP-3 from stromelysins and MMP-14 from membrane-type (MT) MMPs (Rose and Kooyman, 2016). Here, MMP9 is linked to rheumatoid arthritis.