[The role of promoter CpG islands methylation of leptin gene in osteoarthritis].

ABSTRACT

OBJECTIVE: To investigate the effects of 5-Aza-CdR (methylation transferase inhibitor)on the expression levels of leptin gene in chondrocytes and methylation states of leptin promoter region between osteoarthritis (OA) group and control. METHODS: The chondrocytes in osteoarthritis group were treated with 5-Aza-CdR with different doses and time-points, and the expression level of leptin was detected by real-time polymerase chain reaction for picking up the optimum dose and time-point. Next, the chondrocytes in 5 osteoarthritis patients and 5 control patients (amputation due to severe trauma) were treated with 5-Aza-CdR. Lastly, leptin mRNA expression levels in the four groups osteoarthritis and control chondrocytes treated with/without 5-Aza-CdR were measured by real-time PCR and the methylation state of promoter region (-280 - +79) was detected by epitope quantitative DNA methylation analysis. RESULTS: (1) After treating the chondrocytes in OA groups with 10 µmol/L 5-Aza-CdR for 72 h, the mRNA expression levels of leptin were increased significantly. (2) The mRNA expression levels of leptin were significantly different among the four groups (P < 0.05), and the chondrocytes in osteoarthritis groups treated with 5-Aza-CdR showed a marked induction of leptin mRNA expression. (3) Analysis of quantitative methylation data using an unsupervised hierarchical clustering algorithm, showed that methylation patterns of leptin promoter was different between control and osteoarthritis chondrocyte treated with/without 5-Aza-CdR. CONCLUSION: Demethylation of leptin promoter might up-regulate leptin gene expression level and it might contribute to osteoarthritis.