Background Dickkopf-1 (Dkk-1) and sclerostin (Scl) are likely to play important roles in the process of ankylosis in Spondyloarthritis (SpA) . Their serum levels are associated with the formation of new syndesmophytes . But the relationship between these biomarkers and disease activity including active inflammatory lesions in sacroiliac joints (SIJ) on magnetic resonance imaging (MRI) still not clear.
Objectives To estimate the relationship between the Scl and Dkk-1serum levels and active inflammatory MRI lesionsin SIJ, disease activity and functional status in SpA patients (pts).
Methods Serum levels of Scl and Dkk-1 (pmol/l; ELISA) were measured at baseline in 79 pts with SpA. Mean age of pts (63.3% male) was 37.5±11.3, mean disease duration – 10.7±9.44 yrs. Radiological sacroiliitis defined according to Kellgren grade was: 0 – 1.6%, I – 22%, II – 49.2%, III – 13.6% and IV – 13.6%. Active inflammatory lesions in SIJ were evaluated with Spondyloarthritis Research Consortium of Canada (SPARCC) MRI SIJ score (0–72, n=46). Disease activity was measured by Ankylosing Spondylitis Disease Activity Score (ASDAS) using C-reactive protein (CRP), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI, mm), CRP (mg/l) and erythrocyte sedimentation rate (ESR, mm/hr). Functional status estimated using Bath Ankylosing Spondylitis Functional Index (BASFI, mm). For correlation the Spearman correlation coefficient was calculated.
Results Mean value (M±σ) of biomarkers in all SpA pts were: Scl – 19.2±11.63, Dkk-1 – 30.7±19.5. The mean value of indices and laboratory parameters in all SpA pts were: ASDAS-CRP – 3.01±1.09, BASDAI – 4.36±1.88, CRP – 20.3±33.0, ESR – 25.8±20.7, BASFI – 3.01±2.33. SPARCC score was 24.6±10.9.
Scl level was significantly higher in pts with lower activity by SPARCC score (23.1±12.7) vs higher activity (16.6±7.63), p=0.043, in pts with moderate disease activity by ASDAS-CRP (22.3±15.6) vs very high disease activity (14.6±9.89), p=0.031, and in women (23.1±12.6) vs men (16.9±10.5), p=0.014. Its level didn't depend on CRP, ESR, BASDAI, BASFI and HLA B27 positivity.
Scl showed significantly negative correlation with BASDAI (r=-0.381, p=0.041) only in women.
There was no difference in Dkk-1 serum level depending on the gender, disease activity (by ASDAS-CRP), functional status, the presence of HLA B27 and inflammatory changes in SIJ (with quartile distribution). But the correlation analysis showed significant relationship of Dkk-1 with CRP (r=0.243, p=0.031) and SPARCC MRI SIJ score (r=0.351, p=0.017). The strength of the correlation between Dkk-1 and CRP was slightly higher in HLA B27 positive pts (90%; r=0.334, p=0.018).
In SpA pts with lower activity by SPARCC score significant correlation between Dkk-1 and inflammatory lesions in SIJ (r=0.400, p=0.043) and a negative correlation between Dkk-1 and BASDAI (r=-0.513, p=0.017) were found.
There was no correlation between Scl and Dkk-1 levels among all pts and different subgroups.
Conclusions Scl level is significantly higher in pts with lower disease activity by SPARCC MRI SIJ score and ASDAS-CRP. Dkk-1 significantly positively correlates with disease activity due to CRP level and SPARCC score, but not to BASDAI.
Xie W. Ann N Y Acad Sci. 2016 Jan; 1364: 25–31.
Song I-H. Ann Rheum Dis. 2011 Jul 1; 70(7): 1257–1263.
Disclosure of Interest None declared