Decreased Local And Systeatic Matrix Gla Protein (MGP) Expression And Its Link To Radiographic Progression In Ankylosing Spondylitis Patients

Objective:Decreased serum levels of uncarboxylated matrix Gla-protein (ucMGP) have been detected in Ankylosing Spondylitis (AS) patients. The current study was to investigate the expression of MGP in AS tissues as well as the relationship between serum ucMGP (an inactive form of MGP) levels and radiographic severity in AS patients.Methods:From July 2012 to June 2014,62 patients fulfilling the modified New York criteria visiting our hospital were enrolled in this study. A total of 68 age and gender matched subjects receiving regular body check were recruited as healthy controls. Local MGP expression were assessed by Western blot and RT-PCR in hip synovial tissues from patients with AS and control subjects.In addition, the serum level of ucMGP was assessed by enzyme-linked immunosorbent assay in 68 healthy subjects and 62 patients with AS. The radiographic progression of AS was classified according to the radiographic events of modified New York Criteria for sacroiliac joint evaluation and changes in radiographic pictures were evaluated according to the modified Stoke AS Spine Score (mSASSS), and serum level of ucMGPwas measured by a competitive ELISA. The relationship between ucMGP and clinical indexes, radiographic scoring, indices in bone metabolism or inflammation was estimated by SPSS software, and the diagnostic value of ucMGP was analyzed by receiver operator characteristic (ROC) curve.Results:MGP expression was downregulated in AS patients compared to controls in hip tissues. Decreased levels of ucMGP in serum were found in AS patients compared with healthy controls. ucMGP levels in serum of AS patients were significantly negatively correlated with the disease radiographic severity evaluated by modified New York grading criteria (r=-0.293, p= 0.045) and mSASSS system (r=-0.361, p= 0.03). Conclusions:MGP expression is impaired in patients with AS. A low serum level of ucMGP in the setting of AS is linked to increased structural damage, emphasizing the role of MGP in the suppression of new bone formation. Serum ucMGP may serve as a diagnostic biomarker of AS and progression index of ossifi cation, especially in late stage of AS.