Association of interleukin-1 receptor antagonist gene polymorphisms with early onset periodontitis in Japanese

Background/Aims: Early onset periodontitis (EOP), newly ‘aggressive periodontitis’, is considered to have genetic basis, which have not been clearly defined. The interleukin‐1 (IL‐1) gene cluster polymorphism as one of genetic factors may influence the expression of several chronic inflammatory diseases. The aim of this study is to investigate the frequency of single nucleotide polymorphisms (SNPs) in the genes encoding IL‐1α, IL‐1β and a variable number of tandem repeat (VNTR) polymorphisms in the IL‐1 receptor antagonist gene (IL‐1RN) in 47 generalized EOP (G‐EOP) patients and 97 periodontally healthy controls. Material and methods: All subjects were of Japanese descent and systemically healthy. They were identified according to established clinical criteria. SNPs in the IL‐1α (+ 4845) and IL‐1β (− 511, + 3954) genes were analyzed by amplifying the polymorphic region using polymerase chain reaction (PCR), followed by restriction‐enzyme digestion and agarose gel electrophoresis. IL‐1RN (VNTR) polymorphisms were then detected by PCR amplification and fragment size analysis. Results: There was no significant difference in the IL‐α (+ 4845) and IL‐1β (− 511, + 3954) genotypes and allele frequencies between G‐EOP patients and healthy controls. However, the frequency of IL‐1RN (VNTR) polymorphic alleles was found to be significantly increased in G‐EOP patients (χ2 test, P = 0.007; odds ratio = 3.40). Additionally, the carriage rate of IL‐1RN (VNTR) polymorphisms was significantly higher in G‐EOP patients than in healthy controls (χ2 test, P = 0.005; odds ratio = 3.81). Conclusion: These findings suggest that IL‐1RN (VNTR) polymorphisms are associated with G‐EOP in Japanese.