Preliminary Analysis Of Gene Expression Profiles On The Hip Joint Ligament Of Ankylosing Spondylitis Patients

PremiseAnkylosing spondylitis is a kind of rheumatoid factor-negative, chronic, progressive inflammatory disease which initially involves the sacroiliac joints, violate the axial joints, and get ligaments and tendon inflamed in the attachment points of bone. It also can affect internal organs and other organizations. It has been thought a complex disease, but also a multi-gene genetic disease. The disease is inflammatory arthritis in second place. Due to erosion and destruction of articular cartilage and bone and pathologic new bone formation, the axial joints such as the spine, hip joints make fused and stiff, eventually leading to loss of joint function. The loss of labor and independent living ability make it a higher disability disease. According to epidemiological survey, the disease occurs in the young adults (10～40 years old), especially the peak incidence of age (20 to 30years old). The prevalence of different races is different and in our country it is 0.22%. The ligament ossification occurs in advanced stage, resulting in spine and hip joint ankylosis and deformities.Particularly ligament ossification in the hip joint will cause serious dysfunction, giving the patient's life and work great suffering. At present, there is no fundamentally effective drugs for the AS except only controlling the inflammation.The anti-rheumatic drugs and immunodepressant are used frequently, but abnormal ossification process is powerless to control and ultimately only depends on surgery. Therefore, to explore the pathogenesis of ankylosing spondylitis, especially study of the hip ligament ossification mechanism, is great significant to search for the clinical treatment of AS and target inhibition of ligament ossification.ObjectiveWe make use of gene chip technology to study the hip ligament gene expression profiles of ankylosing spondylitis patients and normal person to find the difference between the two groups'genes, especially differential genes related to ossification. Through this study, we preliminary approach the pathological mechanism of abnormal bone formation of ankylosing spondylitis patient ligament.Method18 cases of AS patients treated with hip arthroplasty in our department in 2008-2009 are acted as a AS group. All patients are in line with New York revised diagnostic criteria of ankylosing spondylitis in1984.7 cases of femoral neck fractures patients with hip arthroplasty (to exclude other types of bone and joint diseases) are acted as a healthy control group. Among the AS group and healthy control group, five objects are selected respectively, and the ten ligaments of the hip joint are used to screen with HumanWG-6 v3.0 Expression BeadChip for differential gene. To filter out some of the differential genes, 18 cases of AS group and 6cases of healthy control group are validated by real-time fluorescence quantitative PCR.ResultsGene chip results of AS group and healthy control group show that among the known functional genes:P<0.05, there are different in 519 genes, of which 301 up-regulated genes, down-regulated genes 218; P<0.01, there are different in gene 43, of which 31 up-regulated genes, of which 12 down-regulated genes; differenct functional genes involve in B cell receptor signaling pathway, cell adhesion signaling pathway, protein export signaling pathway, fructose and mannose metabolic pathways, T cell receptor signaling pathway, keratan sulfate biosynthetic pathway, N-glycans biosynthesis pathway and actin regulation pathway. Real-time fluorescence quantitative PCR results showed that B4GALT3 gene expression in the AS group is 15.32 times the healthy control group, and RBP5 gene expression in the AS group is 4.09 times the healthy control group, so that both the two genes expression in the AS patients are significantly higher.ConclusionHip joint ligaments of ankylosing spondylitis patients change in the aspect of immunity, cell adhesion, membrane transport, sugar metabolism, polysaccharide synthesis and metabolism, cell movement. Of all differential genes, the 43 more significant differential expression genes mainly related to the cell proliferation and differentiation, cell adhesion, mediated angiogenesis, lysosome synthesis, cytoskeleton and so on. In ankylosing spondylitis patients, B4GALT3 gene stimulates the excessive synthesis of keratin sulfate in their ligaments to promote calcium deposition in the extracellular matrix, so that hip joint ligament abnormally ossify; RBP5 gene of ankylosing spondylitis patients may play an important role in the process of hip ligament ossification. Both of them are not reported, but the exact mechanism remains to be further study.