The association of MMP-9 and IL-18 gene promoter polymorphisms with gingivitis in adolescents

Objective: Interleukin 18 (IL-18) is shown to be a proinflammatory cytokine that regulates the expression of matrix metalloproteinase 9 (MMP-9). The aim of this study was to test for differences between Czech adolescents with and without gingivitis in relation to MMP-9 and IL-18 polymorphisms. Design: A total of 298 Caucasian children, aged 11-13 years, were examined to assess gingival health. DNA for genetic analysis was obtained from buccal epithelial cells, and the MMP-9 -1562C/T and IL-18 -607A/C variants were identified with PCR-RFLP. Results: Gingivitis was present in 49.3% of the adolescents examined, the rest of the group was considered healthy. The IL-18 -607C and MMP-9 -1562T alleles were found in 58.9% and 8.3% of the healthy subjects, and in 62.2% and 15.0% of the patients with gingivitis, respectively. Although differences in allele frequencies were not significant for IL-18 variant, they were significant for MMP-9 polymorphism (p = 0.01, p(corr) < 0.05). Furthermore, a highly significant association of the composite genotype (formed by the variants of the both genes) with gingivitis was found (p = 0.004, p(corr) < 0.05). Conclusions: The -1562 T allele of MMP-9 gene could have a role in gingivitis in adolescents. In addition, interaction of the MMP-9 and IL-18 genes could be considered a risk factor for the development of gingivitis in children. (c) 2008 Elsevier Ltd. All rights reserved.