Background Ankylosing spondylitis (AS) is a common inflammatory rheumatic disease which preferentially affects the axial structures causing spinal ankylosis, AS is more common in young adults aged 10–40, but the onset age can also be childhood. It was grouped according to onset age: those with onset symptoms before the age of 16 years were classified as Juvenile-onset Ankylosing Spondylitis (JAS), and patients with onset symptoms older than 16 at onset were classified as Adult-onset Ankylosing Spondylitis (AAS). Clinical phenotype and prognosis of JAS is different from AAS,but up to now scarce information about JAS was reported, especially the related bone metabolism mechanism.
Objectives To analyse bone metabolic index (BMI) changes on patients with Juvenile-onset Ankylosing Spondylitis (JAS) and their relations with clinical index.
Methods To collect the clinical data of JAS,such as C-reactive protein (CRP), blood sedimentation (ESR),the disease activity index (BASDAI),functional index (BASFI) and bone mineral density (BMD), detect the serum bone metabolism index,such as Wnt-3a, BMP-2, Dkk-1, 25 (OH) D and ICTP, then group these data and do statistical analysis.
Results Osteopenia and VitD lack were widespread in JAS. Compared with controls, The elevated Wnt-3a and reduced Dkk-1 levels were not significant in JAS (P>0.05), and there was no significant correlation between the two indexes and other BMI, course, clinical inflammation index, BASDAI and BASFI. However,the serum ICTP and BMP-2 were increased significantly in JAS, and both the CRP and BMP-2 were positive related with serum Wnt-3a (r was 0.271 and 0.250 respectively, P<0.05).Correlation analysis shew there was positive correlation between serum 25 (OH) D and hip BMD in JAS (r=0.383, P<0.01), and there was negatively correlation between ICTP and BASDAI (r=-0.405 and -0.273 respectively, P<0.05).Besides,regression analysis shew that both serum 25 (OH) D and the disease course were independent prognostic factors of patients' hip BMD decreasing, where as CRP and ICTP were also independent prognostic factors of patients' BASDAI. BMI in JAS with different clinical phenotypes were compared, BMP-2 level was much higher in JAS with hip joint involvement than other groups (P=0.032), while there was no significant difference in serum 25(OH)D,ICTP,Wnt-3a and Dkk-1 level in all groups (P<0.05).
Conclusions There is bone metabolism imbalance in JAS,and BMI can indirectly reflect the disease activity and bone loss,among which BMP pathway played an important role in the JAS with hip lesions and deserves further research.
Khan MA: Update on spondyloarthropathies. Ann Intern Med 2002, 136:896–907.
Lories RJ, Luyten FP, de Vlam K. Progress in spondylarthritis. Mechanisms of new bone formation in spondyloarthritis.Arthritis Res Ther. 2009;11(2):221.
Fujita K, Janz S,DAttenuation of WNT signaling by Dkk-1 and -2 regulatesBMP2-induced osteoblast differentiation and expression of OPG, RANKL and M-CSF. Mol Cancer,2007,6: 71.
Zhang M, Yan Y, Lim YB, et al. BMP-2 modulates beta-catenin signalingthrough stimulation of Lrp5 expression and inhibition of beta-TrCP expression inosteoblastsJ Cell Biochem,2009,108(4): 896–905.
Fischer L, Boland G, Tuan RS. Wnt signaling during BMP-2 stimulation of mesenchymal chondrogenesis. J Cell Biochem. 2002;84(4):816–31.
Disclosure of Interest None declared