Changes in gene expression profiles of the hip joint ligament of patients with ankylosing spondylitis revealed by DNA chip.

To investigate the pathogenesis of abnormal ossification of the hip ligament in patients with ankylosing spondylitis (AS) by comparing gene expression profiles of the hip ligament in patients with AS to those in normal persons using DNA microarray technology, we studied 18 patients with AS (case group) who underwent total hip arthroplasty in our department from March 1, 2009 to January 31, 2010 and compared them with 6 patients with femoral neck fracture (control group) who underwent total hip replacement. We screened the first five patients in each group with the HumanWG-6 v3.0 Expression BeadChip. Compared to the control group, 519 genes in the case group showed statistically significant differences. Among these, there were 238 upregulated genes and 196 downregulated genes. Gene Ontology (GO) classification showed that differential genes in the hip joint ligaments of patients with AS were involved in immunity, cell adhesion, membrane transport, sugar metabolism, polysaccharide synthesis and metabolism, and cell motility. The Kyoto Encyclopedia of Genes and Genomes classification showed that these differential genes were involved in B cell receptor signaling pathways, adherens junction, protein export, fructose and mannose metabolism, T cell receptor signaling pathways, keratin sulfate biosynthesis, N-glycan biosynthesis, and regulation of the actin cytoskeleton. We tested 2 genes from the screened differential genes in 18 case patients and 6 control cases using real-time polymerase chain reaction. The results demonstrated that the expression of the B4GALT3 gene in the case group was 15.32 times higher than that in the control group (P < 0.01), and the expression of the RBP5 gene in the case group was 4.09 times higher than that in the control group (P < 0.01). This conformed to the microarray analysis. Our preliminary data suggest that differential gene expression in patients with AS includes the immune system, intracellular or extracellular signaling pathway, and bone matrix biosynthesis pathway, which might play important roles in hip joint ligament ossification.