Downregulation of lncRNA TUG1 is involved in ankylosing spondylitis and is related to disease activity and course of treatment.

Long non-coding RNA taurine-upregulated gene 1 (lncRNA TUG1) promotes osteosarcoma, while its involvement in other bone diseases, such as ankylosing spondylitis (AS) is unknown. Expression of TUG1 in serum and open sacroiliac biopsies of AS patents and healthy controls was detected by real-time quantitative PCR (qRT-PCR). Ankylosing spondylitis disease activity score (ASDAS) system was used to evaluate disease activity. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic value of lncRNA TUG1 for AS. Chi-square test was performed to analyze the correlations between TUG1 expression and patients' clinicopathological data. Patients were divided into 2 groups (high and low expression groups) according to the median expression level of TUG1 and were followed-up for 5 years after discharge. Treatment courses and rehospitalization rate were compared between two groups. It was observed that TUG1 expression level was significantly lower in AS patients than in healthy controls in both serum and biopsies. Reduced expression level of TUG1 distinguished AS patients from controls. LncRNA TUG1 expression was significantly correlated with patients' smoking habits, disease activity, and course of disease. Patients in high expression group showed longer hospitalization time and higher rehospitalization rate. We therefore conclude that expression of lncRNA TUG1 was inhibited in AS patients and downregulation of lncRNA TUG1 is related to higher disease activity, longer course of treatment and higher rehospitalization rate.