Sclerostin rather than Dickkopf-1 is associated with mSASSS but not with disease activity score in patients with ankylosing spondylitis.

Objective: To determine the serum levels of Dickkopf-1 (DKK-1) and sclerostin, as well as their correlations with the structural damage assessed by modified stoke ankylosing spondylitis spine score (mSASSS) and the disease activity evaluated by ankylosing spondylitis disease activity score (ASDAS) in patients with ankylosing spondylitis (AS).

Methods: Eighty-eight AS patients, 26 rheumatoid arthritis (RA) patients, and 26 age- and gender-matched healthy controls (HC) were collected from rheumatic clinic of the Second Affiliated Hospital of Zhejiang University, School of Medicine, between March 2015 and July 2015. Demographic data, parameters of ASDAS, and image evaluations of spine (i.e., mSASSS) were collected. The serum levels of DKK-1 and sclerostin were measured using commercially available ELISA kits.

Results: Both DKK-1 and sclerostin were significantly higher in the AS patients than in the controls (1855 ± 84.58 vs. 1406 ± 99.76 pg/ml and 106 ± 6.75 vs. 62.78 ± 6.39 pmol/l, respectively, P < 0.05). The correlation analysis suggested a negative correlation between serum sclerostin and mSASSS (P = 0.019, r = 0.062). DKK-1 had a trend of positive correlation with mSASSS, but was not statistically significant (P > 0.05). There was no association between the serum levels of DKK-1 or sclerostin and disease activity assessed by ASDAS (P > 0.05). DKK-1 and sclerostin had a negative correlation (P = 0.013, r = 0.07).

Conclusion: In the present study, the expressions of serum DKK-1 and sclerostin were independent of disease activity. Sclerostin was negatively correlated with the mSASSS, which suggests that sclerostin may be a potential marker indicating the spine ossification process in AS. The specific mechanism remains to be investigated.