| Objective: Ankylosing spondylitis (AS) was a kind of chronic autoimmune disease, which was agnogenic yet, and sacroiliitis was characteristic clinical performance that had diagnostic significance. Arthromeningitis, bone and cartilage damage were essential pathological performance, and could lead to deformity, activity limitations. In addition, osteopenia and osteoporosis were common in AS, and influence daily life seriously. However, the mechanism was not fully identified yet. Recently, the research about AS was focus on bone and cartilage metabolism. The aim of this study was to investigate the bone and cartilage metabolism in AS through measuring the levels of cartilage oligomeric matrix protein (COMP), osteopontin (OPN), bone alkaline phosphatase (BALP) and tartrate resistant acid phosphatase 5b (TRACP-5b) in serum, and analyzing the correlationship between these parameters and the clinical indicates such as ESR, CRP, bone mineral density (BMD) and so on , to discuss therapeutic action of bisphosphonates (BPs) in AS and provide certain basis for treatment of AS.Methods: 34 patients of AS and 30 normal controls aged over 20 were chosen. All of the patients corresponded the modified criteria for AS by American College Of Rheumatology (ACR), without any other bone diseases, tumors, angiocardiopathies, liver and kidney diseases. They had been not given glucocorticoid and biologics. 34 patients were divided into BPs treatment group (16 patients) and non-BPs treatment group (18 patients), and the course of treatment was about 9 months. The levels of serum COMP, OPN, BALP and TRACP-5b were determined by avidin biotin peroxidase complex enzyme-linked immunosorbent assay (ABC-ELISA). The BMD of lumbar, femoral neck, greater trochanter and inter trochanter of AS patients were measured through dual-energy X-ray absorptiometry (DEXA). The clinical data of AS patients were collected such as age, disease duration, body mass index (BMI), erythrocyte sedimentation rate (ESR), c-reactive protein (CRP), immunoglobulin (Ig) A, M, G, complement 3, 4, platelet( PLT), serum levels of calcium (Ca), phosphorus (P), white blood cell (WBC), globulin (GLOB), alkaline phosphatase (ALKP) and sacroiliac joint CT grading (SICT) of AS patients, etc. The bone and cartilage metabolism indicates of AS patients were compared with normal controls. The correlation between above mentioned bone and cartilage metabolism indicates in AS patients and clinic indicates such as ESR, CRP were analyzed. Besides, the variation in indicates related to bone and cartilage prior and post treatment was statistically analyzed.All the data were analyzed by SPSS13.0 for Windows statistical software. The mean number±standard deviation ( x±s) was used to express the measurement data. The t or t'test was adopted for comparison between groups. Chi-square test was used for the comparison of the enumeration data. Linear correlation analysis was performed for correlationship. P value<0.05 was considered significant.Results:1 The demographic details in AS: In the group of 34 patients with AS, the mean disease duration at presentation was (5.00±1.98)yr, with a mean age of (26.12±4.97)yr. There were 16 cases in BPs treatment group, including 4 females, and the mean disease duration at presentation was (6.06±2.08)yr, with a mean age of (27.00±5.48)yr. There were 18 cases in non-BPs treatment group, including 2 females, and the mean disease duration at presentation was (4.06±1.72)yr, with a mean age of (25.00±4.5)yr. 30 normal controls included 6 females, with a mean age of (26.83±3.49)yr. There was no significant difference between the AS group and control group in age and gender (P>0.05). So was between BPs group and non-BPs group in age, gender and disease duration (P>0.05).2 Results of bone density measurement:In AS group, the incidence of normal bone mass, osteopenia and OP were 23.53%, 35.29% and 41.18% respectively. The incidence of osteopenia in lumbar, femoral neck, greater trochanter and inter trochanter were 23.53%, 17.65%, 29.41% and 29.41% respectively. The incidence of OP in lumbar, femoral neck, greater trochanter and inter trochanter were 17.65%, 11.76%, 35.29% and 0.00% respectively. There were different incidences of osteopenia and OP in different measurement sites (χ2=8.659, P=0.034), and the highest site was greater trochanter (64.70%).3 The levels of indicates related to bone and cartilage metabolism in serum3.1 The serum level of COMP in AS group (7.49±2.92)μg/L prior treatment was significantly higher (P<0.05) than normal controls (3.92±1.66)μg/L. There was no significant difference between the AS group post treatment (5.64±2.12)μg/L and normal controls (P>0.05).The level of COMP in AS group post treatment was significantly decreased (P<0.05) than prior treatment.3.2 The serum level of OPN in AS group prior (33.65±11.71)μg/L and post treatment (32.38±11.01)μg/L were significantly higher (P<0.05) than normal controls (23.44±5.28)μg/L. There was no significant difference between prior and post treatment in AS group.3.3 The serum level of BALP in AS group prior treatment (2.92±0.86)μg/L was significantly higher (P<0.05) than normal controls (2.08±0.61)μg/L. There was no significant difference (P>0.05) between AS group post treatment (2.64±1.30)μg/L and normal controls. There was no significant difference between prior and post treatment in AS group either.3.4 The serum level of TRACP-5b in AS group prior treatment (45.51±17.15) ng/L and post treatment (43.14±16.55) ng/L were both significantly higher (P<0.05) than normal controls (33.62±3.92) ng/L. The level in AS group post treatment was significantly decreased (P<0.05) than prior treatment.4 The serum level of OPN was positively correlated with TRACP-5b (r=0.625, P=0.007).Except the positive correlation between COMP and CRP, BMI, sacroiliac joint CT grading (r=0.643, P=0.005; r=0.488, P=0.047; r=0.748, P=0.001), the positive correlation between OPN and ESR (r=0.578, P=0.015), the positive correlation between BALP and CRP, ALKP, the BMD of lumbar (r=0.511, P=0.036; r=0.489, P=0.047; r=0.590, P=0.013), and the positive correlation between TRACP-5b and ESR, CRP (r=0.615, P=0.009; r=0.574, P=0.016), there was no linear correlation between the four indicates related to bone and cartilage metabolism and clinical data, such as PLT, P, Ca, IgG, IgA, IgM, C3, C4, age and disease duration.5 The comparision between BPs group and non-BPs group in the indicates related to bone and cartilage metabolism5.1 The level of serum COMP post treatment (4.31±1.39)μg/L was lower than prior (7.50±3.19)μg/L (P<0.05) in BPs group, but no significant difference in non-BPs group (6.72±2.24)μg/L vs (7.49±2.86)μg/L (P>0.05). The range of changes of BPs group was higher than non-BPs group, but there was no significant difference (P>0.05).5.2 The serum level of OPN post treatment (30.83±11.76)μg/L was significantly lower (P<0.05) than prior (33.52±12.67)μg/L in BPs group, but no significant difference in non-BPs group (P>0.05). The range of changes of BPs group was significantly higher than non-BPs group (P<0.05).5.3 The serum levels of BALP post treatment in BPs group (2.51±1.36)μg/L and non-BPs group (2.76±1.40)μg/L were all significantly lower (P<0.05) than prior treatment (2.98±0.87)μg/L & (2.86±0.90)μg/L. The range of changes was not significantly different (P>0.05).5.4 The serum level of TRACP-5b post treatment (43.24±13.50) ng/L was significant lower (P<0.05) than prior (47.08±13.07) ng/L in BPs group, but no significant difference in non-BPs group (P>0.05). The range of changes of BPs group was significantly higher than non-BPs group (P<0.05).6 Both of the levels of ESR and CRP decreased significantly through treatment (P<0.05). But there were no significant difference (P>0.05) in levels of PLT, WBC, IgA, IgM, IgG, C3, C4, GLOB, Ca, P, ALKP and SICT. The range of changes of ESR in BPs group was higher than non-BPs group, but no significantly different (P>0.05). The range of changes of CRP in BPs group was significantly higher than non-BPs group (P<0.05).7 During the study period, no severe complications were observed such as gastrointestinal intolerance, severe allergy, hypotension, liver and kidney damage, and so on.Conclusions:1 AS patients showed osteoporosis and osteopenia more frequently than healthy controls.2 AS patients showed abnormality in cartilage metabolism. COMP might be an early activity indicate of AS.3 The abnormal bone metabolism of AS might be caused by multiply factors. It showed both bone resorption and bone formation enhancing at the same time, especially the bone resorption, and correlated with inflammation activities.4 The abnormality of bone and cartilage metabolism in AS patients could obtain certain improvement through comprehensive therapy.5 Bisphosphonate was an effective and well-tolerated agent for the treatment of AS.
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