Background/Purpose: The association between inflammation and spinal damage in Ankylosing Spondylitis (AS) remains unclear. Tumor necrosis factor-α (TNF- α) plays pivotal role in inflammatory process of AS. However current cytokine inhibitor strategies in AS fail to halt new bone formation. This condition propounds that the structural damage of AS patients might be affected by noninflammatory processes or non-TNF- α inflammatory pathways. The aim of this study is to investigate the effects of some markers with possible contributions to structural damage in AS and their relationship with radiographic progression.

Methods:  The study included 238 AS patients and age and sex-matched 150 healthy controls. All AS patients met Modified New York criteria or ASAS axial spondyloarthritis criteria. When patients applied for their routine follow ups, demographic data (age, gender, disease duration, mediacations), ESR, CRP, and total blood count were recorded. Along with the radiographic evaluation (mSASSS), serum levels of DKK-1, BMP-2, BMP-4, Sclerostin (SOST), IL-17, and IL-23 were analyzed.

Results: DKK, SOST, IL17, and IL23 were significantly higher in AS group while bm2 level was significantly lower among AS patients (p<0.001). (table-1) When the association between biomarker levels and disease activity parameters was investigated, bm2 concentration was significantly higher and bm4 concentration was lower among patients with higher BASDAI scores ( >4) (p:0.046, p:0.033 respectively). No statistically significant difference was found between antiTNF and NSAID groups in terms of marker levels ( p>0.05). Variance analyses showed that none of the factors solely affected the mSASSS. However, if bm2, bm4, and IL 17 levels were greater than median values, the mSASSS was affected by 3.3% (p=0.017). DKK, SOST, bmp2 and IL17 affected mSASSS by 2.6% if they exceeded median values (p=0.029). (table-2). These correlations were significant but weak.

Conclusion: The mechanism of new bone formation in AS seem to be complicated and a consequence of inextricable processes. As a manifestation of this confusion, DKK-1 and SOST, with inhibitory effect on bone formation were found to be higher, and BMP-2, a bone formation marker was found to be lower among AS patients. These results propound the importance of local factors (enthesis sites) and possible disease-specific effects of biomarkers.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-association-between-radiologic-progression-and-serum-levels-of-potential-markers-of-bone-formation-in-ankylosing-spondylitis-patients/