Expression of TET2 enzyme indicates enhanced epigenetic modification of cells in periodontitis

DNA methylation is an important epigenetic mechanism involved in the regulation of gene expression, and a reduction in DNA methylation influences cell-cycle progression and cell differentiation in inflammatory cells. The aim of the present study was to analyze the DNA-methylation pattern at local and global/systemic levels in patients with periodontitis and gingivitis. Twenty-one subjects with generalized, severe periodontitis and 17 subjects with gingival inflammation but no attachment loss were recruited. Gingival biopsies and peripheral blood samples were collected and prepared for immunohistochemical analysis of 5-methylcytosine (5mC), 5-hydroxymethylcytosine (5hmC), ten-eleven translocation 2 (TET2), and DNA methyltransferase 1 (DNMT1). Whilst a similar pattern for 5mC and 5hmC DNA methylation was found in both types of lesions, a significantly larger proportion of TET2-positive cells was found in periodontitis lesions than in gingivitis lesions. Quantitative real-time PCR analysis showed no differences between gingivitis and periodontitis lesions regarding expression of TET2 and isocitrate dehydrogenase (IDH) genes, while the global level of 5hmC was significantly higher in blood than in tissue in patients with periodontitis. It is suggested that epigenetic changes are more common in periodontitis lesions than in gingivitis lesions and that such changes are tissue specific.