Osteoclast Precursors In Peripheral Blood Of Patients With Ankylosing Spondylitis

Object:To investigate the osteoclast (OC) precursor number in peripheral blood of patients with ankylosing spondylitis (AS) and its relationship with serum receptor activator of nuclear factorκB-ligand (RANKL) and Osteoprotegerin (OPG) concentration as well as the disease activity.Method: The peripheral blood mononuclear cells from 8 cases of AS patients and 5 healthy controls were cultured in the medium [0] containing macrophage colony-stimulating factor (M-CSF) (25 ng/ml) and RANKL (40 ng/ml). After being cultured for 14 days, immuocytochemistry was applied to detect tartrate-resistant acid phosphatase[0] (TRAP) expression[0] and the cells with TRAP expression and≥3 nuclei were counted and defined as OC. Bone resorption assay was used to demonstrate OC function. ELISA was used to measure serum RANKL and OPG concentration in 23 cases of AS and 17 healthy controls. The relationship was analyzed in AS patients between OC precursor number and serum RANKL and OPG concentration as well as the disease activity. The indicators of the disease activity were Bath ankylosing spondylitis disease activity index (BASDAI), Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and X ray of sacroiliac joints.Results:1. Significantly higher OC production was observed in peripheral blood of AS patients than that of healthy control group. The OC number per ten fields were 10.88±3.40 (±SD) and 6.20±1.30 respectively, (p<0.05) ; 2. Significantly positive correlation was observed[0] between the OC number and the serum concentration of RANKL (r=0.692, p=0.009) , the ratio of RANKL/OPG (r=0.813, p=0.001) , and X ray of sacroiliac joint destruction (r=0.866, p=0.005) ; 3. There were significant differences between AS patients and healthy controls in serum concentration of OPG and RANKL and the ratio of RANKL/OPG. OPG was significantly higher in AS patients (157.39±49.19 pg/ml) than in healthy controls (105.41±19.85 pg/ml) (P<0.01). RANKL was significantly higher in AS patients (5.40±3.82 pg/ml) than in healthy controls (1.61±0.76 pg/ml) (P<0.01) . [0]The ratio of RANKL/OPG was significantly higher in AS patients (0.037175±0.025794) than in healthy controls (0.016046±0.008605) (P<0.01) . 4. In AS patients, serum concentration of OPG was found to have significantly negative correlation with X ray of sacroiliac joint[0] destruction (r= -0.500, p=0.015) and BASDAI (r= -0.444, p=0.044). Serum RANKL concentration was found to have significantly positive correlation with [0]X ray of sacroiliac joint[0] destruction (r=0.603, p=0.002) and BASDAI (r=0.543, p=0.011) . The ratio of RANKL/OPG was found to have significantly positive correlation with [0]X ray of sacroiliac joint[0] destruction (r=0.753, p=0.000) and BASDAI (r=0.672, p=0.001).Conclusion: 1. More OC precursors exist in peripheral blood of AS patients, these cells might differentiat into osteoclasts , which might take a role in joints destruption in AS; 2. The mechanism of higher OC production is likely to be higher RANKL concentration which is caused by inflammatory reaction.