Abstract
BackgroundAlthough many studies have focused on the association of the MMP-9 promoter −1562 C/T polymorphism with the susceptibility and/or severity of chronic periodontitis (CP), results have been inconsistent. Therefore, a meta-analysis of all eligible studies was performed to derive a more precise estimation of the association between this polymorphism and CP risk.MethodsAll relevant studies were identified through a database search in PubMed, Medline, and Web of Science. All the full-text studies with appropriate analytical design, published in English, which evaluated the association of MMP-9 promoter −1562C/T polymorphism with CP risk using validated genotyping methods, and with non-duplicated data were selected for this study. A fixed-effect model was used to calculate pooled ORs in the absence of heterogeneity across included trials (P > 0.1 and I2 < 50 %), otherwise the random-effect model was applied.ResultsIn an overall meta-analysis, pooled ORs revealed that T variant in the MMP-9 promoter −1562 C/T polymorphism was associated with a significantly decreased risk for CP under all comparison models. In subgroup analyses by ethnicity, pooled ORs showed that a significant association of the MMP-9 promoter −1562 C/T polymorphism with CP risk was only detected in Caucasians and Asians but not in mixed population. In the subgroup analysis by severity of CP, pooled ORs indicated that T allele of the MMP-9 promoter −1562 C/T polymorphism was associated with decreased susceptibility to severe CP while there was no significant association between this polymorphism and moderate CP.ConclusionsOur meta-analysis showed that T allele in the MMP-9 promoter −1562 C/T polymorphism might be a protective factor for CP, especially in Caucasians and Asians. Moreover, there was a significant association of the MMP-9 promoter −1562 C/T polymorphism with decreased susceptibility to severe CP, while the allelic and/or genotype distributions of this polymorphism were not associated with moderate CP.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-2135-3) contains supplementary material, which is available to authorized users.
Highlights
Many studies have focused on the association of the Matrix metalloproteinase-9 (MMP-9) promoter −1562 C/T polymorphism with the susceptibility and/or severity of chronic periodontitis (CP), results have been inconsistent
Following full-text retrieval of the articles, two studies were eliminated as they investigated the association of the Matrix metalloproteinases (MMPs)-9 promoter −1562 C/T polymorphism with aggressive periodontitis (Chen et al 2007; Gurkan et al 2007)
Pooled odds ratios (ORs) revealed that T variant in the MMP-9 promoter −1562 C/T polymorphism was associated with a significantly decreased risk for CP under all comparison models
Summary
Many studies have focused on the association of the MMP-9 promoter −1562 C/T polymorphism with the susceptibility and/or severity of chronic periodontitis (CP), results have been inconsistent. Matrix metalloproteinase-9 (MMP-9) or gelatinase B, involved in the breakdown of various connective tissue proteins, including types IV, V and XI collagen, proteoglycans as well as elastin, is abundantly expressed in CP (Bildt et al 2008; Rai et al 2008). Various cell lines such as polymorphonuclear leukocytes, macrophages, keratinocytes, fibroblasts, osteoclasts, eosinophils and neutrophils have been connected with the expression of MMP-9 gene, located on chromosome 20q11.2-13.1 (Seguier et al 2001). Genetic variations in the promoter region of MMP-9 gene may have an effect on its transcription and protein synthesis (Chang et al 2002; Soder et al 2009), which may influence connective tissue degradation of the protein and contributing to genetic susceptibility to CP
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