Distinct impacts of syndesmophyte formation on male and female patients with ankylosing spondylitis

Aim:  Ankylosing spondylitis (AS), a chronic inflammatory autoimmune disease, mainly affects the axial skeleton, leading to sacroiliitis and rigidity of the spine. Both spinal rigidity and syndesmophyte development can affect bone formation and resorption. In addition, inflammatory cytokines and cell adhesion molecules are correlated with bone metabolism. The aim of this study was to investigate the effects of gender difference and syndesmophyte formation on cytokines, adhesion molecules and bone metabolism markers in AS patients. Method:  Eighty-seven AS patients (68 males, 19 females) were enrolled in this study. Electrochemiluminescence immunoassay and enzyme-linked immunosorbent assay were performed to measure studied parameters. Results:  Regarding gender, the serum levels of C-terminal crosslinking telopeptide of type I collagen (CTX), vascular endothelial growth factor, soluble vascular cell adhesion molecule-1, tumor necrosis factor alpha and interleukin (IL)-18 in male patients were all significantly higher than those in female patients. The serum levels of osteocalcin and type I procollagen N-terminal propeptide showed downward trends, whereas CTX and parathyroid hormone concentrations were remarkably lower and IL-18 levels were significantly higher in male AS patients with syndesmophytes compared to those without syndesmophytes. In female patients, CTX and IL-6 levels in those with syndesmophytes were significantly higher than in those without syndesmophytes. Cytokines, adhesion molecules and bone metabolism markers were all positively related with syndesmophyte formation and gender differences. Conclusion:  AS patients with syndesmophytes experienced imbalance of bone metabolism due to inflammatory cytokine release. Male AS patients had high levels of bone resorption markers, cytokines and adhesion molecules, reflecting a disorder of bone metabolism.