强直性脊柱炎继发骨质疏松及相关因素分析

目的 测定强直性脊柱炎(AS)患者骨密度(BMD)、血清骨保护素(OPG)、可溶性核因子κB受体活化因子配体(sRANKL)等骨代谢指标及外周血T细胞表面RANKL表达情况,研究RANKI/RANK/OPG系统在AS骨代谢中的作用.方法 双能X线吸收法(DEXA)测定AS患者BMD;酶联免疫吸附试验(ELISA)法检测血清OPG、sRANKL、抗酒石酸酸性磷酸酶异构体5b(TRACP-5b)、骨特异性碱性磷酸酶(BALP)水平;分析BMD、上述骨代谢指标及临床指标间相关性;流式细胞术(FC)检测外周血CD4+/RANKL+及CD8+/RANKL+细胞表达率;分析它们与红细胞沉降率(ESR)、C反应蛋白(CRP)相关性.计量资料采用成组设计的t检验,计数资料采用x2检验,相关性采用直线相关分析.结果 ①AS患者骨量减少、骨质疏松(OP)发生率分别为47%、37%.②AS组血清sRANKL、TRACP-5b水平及sRANKL/OPG比值均高于对照组(P<0.05);2组血清OPG、BALP水平差异无统计学意义.③AS组血清sRANKL水平与OPG呈正相关,两者均与TRACP-5b呈正相关(P<0.01.④AS组外周血CD4+/RANKL+细胞表达率高于对照组(P<0.05).结论 AS存在较高的骨量丢失率,其骨代谢特点以骨吸收增强为主,RANKL/RANK/OPG系统在其中起着重要作用,该系统失衡可能是AS骨量丢失机制之一;CD4+T细胞可能通过上调RANKL表达参与AS破骨细胞分化成熟及骨吸收机制.

Analysis of related factors for osteoporosis in ankylosing spondylitis

Objective To investigate the role of RANKL/RANK/OPG system in bone metabolism of ankylosing spondylitis (AS) by detecting bone mineral density, bone metabolism factors such as osteoprotegerin (OPG), soluble receptor activator of nuclear factors-κB ligand (sRANKL) and the expression of membrane-bound (mb) RANKL in the peripheral blood T lymphocytes. Methods Bone mineral density of AS patients were measured by dual-energy X-ray absorptiometry (DEXA) and serum levels of OPG, sRANKL,tartrate resistant acid phosphatase 5b (TRACP-5b) and bone alkaline phosphatase (BALP) were determined by enzyme-linked immunosorbent assay (ELISA). The percentages of CD4+/RANKL+ and CD8+/RANKL+ in the peripheral blood were detected with flow cytometry. T-test, x2-test were used for statisical analysis. Results ① The incidence of osteopenia and osteoporosis in AS was 47% and 37% respectively. ② Serum RANKL,TRACP-5b levels and RANKL/OPG ratio were higher in AS patients than those in normal controls (P<0.05).But there was no significant difference in OPG and BALP between AS patients and normal controls. ③There were positive linear correlation between serum levels of RANKL and OPG, sRANKL and TRACP-5b, OPG and TRACP-5b in AS (P<0.01). ④ The prevalence of CD4+/RANKL+ cells in the peripheral blood of AS patients was significantly higher than that in the normal controls (P<0.05). Conclusion There is a high incidence of bone loss in AS patients. Increased bone resorbtion is the feature of bone metabolism in AS.RANKL/RANK/OPG system may play an important role. The imbalance of RANKL/RANK/OPG system may be one of the bone loss mechanisms of AS. CD4 + T lymphocyte may play an important role in osteoclasts differentiation and bone resorption in AS by up-regulating the expression of RANKL.