Assessment of ankylosing spondylitis by serum cytokine profile

Ankylosing spondylitis (AS) is characterized by new bone formation at sites of inflammation in ankylosis. The aim of this study was to differentiate the cytokines that results in poor outcomes and the major bone turnover cytokines that lead to new bone formation and, paradoxically, to osteoporosis. Thirty-seven selected cytokines were detected using a highly sensitive multiplex system in 46 AS patients and 20 healthy controls (HC) to identify specific profiles that could discriminate inflammatory activity, syndesmophyte formation and changes in bone mineral density. A clinical questionnaire, dual energy x-ray absorptiometry (DEXA) and spinal x-ray radiography were assessed simultaneously. Multiple logistic regressions were performed to confirm the characteristic risk cytokines. Based on Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) scores, 24 patients (52.17%) had active disease stage. Overall, 24 patients (52.17%) showed the presence of syndesmophytes, and 13 patients (28.26%) met the Osteoporosis (OP) criteria. Multivariate analysis of the serum cytokine profile showed that AS patients had higher concentrations of Osteopontin (odd ratio [OR]=0.99; P=0.024) and thymic stromal lymphopoietin (TSLP) (OR=0.842; P=0.032) than controls. Patients with active disease score presented a higher concentration of Chitinase-3 (OR=1.007; P=0.011). The concentration of Chitinase-3 also strongly correlated with total hipbone bone mineral density (BMD), expressed as g/cm2. The presence of syndesmophytes was related to a lower level of Osteocalcin (OCN) (P=0.026). In conclusions, a specific cytokine profile of AS could be identified in patients with AS for the assessment of disease. Chitinase-3 combined with OCN may be an integrality predictive biomarker of AS activity, new bone formation and BMD loss.