Is radiographic progression in radiographic axial spondyloarthritis related to matrix metalloproteinase degradation of extracellular matrix?

Background Radiographic axial spondyloarthritis (r-axSpA) is associated with extracellular matrix (ECM) remodelling of affected tissues. We investigated whether there was a relationship between biomarkers of ECM remodelling and 2-year radiographic progression in r-axSpA. Methods Patients from the Outcome in Ankylosing Spondylitis International Study (OASIS) were included if they had serum, clinical and spinal radiographic assessments available at baseline and 2 years later. Two readers independently scored the radiographs according to the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). The average score was used. Type I, V and VI collagen metabolites (C1M, C5M and C6M) and citrullinated and matrix metalloproteinase-degraded vimentin (VICM) were assessed in serum by ELISAs. The relationship between serum biomarkers and 2-year radiographic progression was investigated using linear regression analyses adjusted for potential confounders. Interactions were tested. Results Patients included (n=122) had a mean age of 45 years (SD 12), 70% were male and 82% were human leucocyte antigen-B27 positive. The mean 2-year mSASSS progression was 2.1 (2.9) units. Only C1M was significantly associated with mSASSS progression (beta=0.01, 95%CI 0.00 to 0.03). The effect disappeared after adjustment for confounders. C5M, C6M and VICM showed no relationship with mSASSS progression. Conclusion We did not find evidence that degradation of ECM is related to radiographic progression in patients with r-axSpA.