Evaluation of PD-1 Gene Expression Profile and Methylation of the Regulatory Regions in Patients with Ankylosing Spondylitis.

BACKGROUND

Ankylosing spondylitis (AS) is a chronic autoimmune disorder characterized by the fusion of vertebral joints and axial arthritis. The programmed death-1 (PD-1) inhibitory receptor has a pivotal role in controlling T cell function and may have a significant impact on the pathogenesis of autoimmune diseases such as AS pathogenesis.

OBJECTIVE

To investigate PD-1 gene expression and its epigenetic regulation by detecting methylated CpG islands in the regulatory sites of the gene. This will provide insight into the mechanisms involved in the disease.

METHODS

30 AS patients and 30 healthy individuals were examined to detect the 16 CpG islands in intron 1 using bisulfite conversion and methylation-specific PCR technique. In addition, RNA samples were isolated from fresh peripheral blood mononuclear cells (PBMCs), and after complementary DNA (cDNA) synthesis, the expression level of the PD-1 gene was evaluated using Real-Time PCR.

RESULTS

The CpG islands located in the intronic zone of the PD-1 gene were hyper-methylated in both the patients with AS and the healthy controls. The gene expression of PD-1 was significantly downregulated in AS patients compared with the controls (p=0.017). A negative correlation between the Bath Ankylosing Spondylitis Disease Activity Index and PD-1 gene expression was also revealed.

CONCLUSION

The low level of PD-1 gene expression is implicated in the pathogenesis of AS. However, in both groups, the methylation level of the intron 1 CpG islands of the PD-1 gene suggests that other regulatory mechanisms are more relevant to PD-1 gene expression than methylation in the intron.