DNA Methylation Changes In Localized Aggressive Periodontitis

Objectives: In previous studies we have demonstrated that Localized Aggressive Periodontitis (LAP) patients exhibit a hyper-inflammatory response to lipopolysaccharide (LPS). However, little is known about epigenetic changes associated with this hyper-responsiveness. Thus, the objective of this study is to evaluate the role of DNA methylation changes in this disease, as well as in susceptible family members, and the influence of LPS stimulation and periodontal treatment in these changes.
Methods: Four genes (MAP3k7, RIPK2, FADD, IRAKBP1) involved in the TLR inflammatory pathway were evaluated for methylation status in the peripheral blood of 25 LAP patients at baseline, 3, 6, and 12 months post therapy, as well as 22 healthy siblings and 33 healthy unrelated controls. Genomic DNA was extracted from buffy coat, after stimulation (control unstimulated) with purified E. coli LPS for 24 hrs. DNA methylation pyrosequencing analysis of different CpG positions of the promoter regions of these 4 genes was performed.
Results: LAP presented high methylation of pro-inflammatory genes MAP3k7 and a mixed methylation status for RIPK2, also showing a high methylation for anti-inflammatory genes FADD and IRAK. Interestingly, siblings showed high methylation of all these genes and LPS stimulation significantly increased their methylation status. LAP treatment resulted in de-methylation of all genes at 3 months with rebound after 6 months post-treatment.
Conclusions: LAP patients and their siblings present high levels of DNA methylation of pro-and anti-inflammatory genes, and LPS stimulation seems to increase these levels in siblings, which could contribute to a lower expression of these genes and explain the higher susceptibility of siblings to periodontal breakdown. Treatment seemed to reverse the methylation status in the genes short term after treatment. Further studies are needed to correlate these findings to the actual expression of these genes to confirm these findings for LAP disease and susceptibility.