DNA Methylation of MMP9 Is Associated with High Levels of MMP-9 Messenger RNA in Periapical Inflammatory Lesions

•This is the first study that shows epigenetic modulation of the MMP2 and MMP9 gene in periapical granulomas and radicular cysts.•Methylation, particularly of the MMP9 gene, may contribute to the pathogenesis of these pathologic conditions.

IntroductionMatrix metalloproteinases (MMPs) are the major class of enzymes responsible for degradation of extracellular matrix components and participate in the pathogenesis of periapical inflammatory lesions. MMP expression may be regulated by DNA methylation. The purpose of the present investigation was to analyze the expression of MMP2 and MMP9 in periapical granulomas and radicular cysts and to test the hypothesis that, in these lesions, their transcription may be modulated by DNA methylation.MethodsMethylation-specific polymerase chain reaction was used to evaluate the DNA methylation pattern of the MMP2 gene in 13 fresh periapical granuloma samples and 10 fresh radicular cyst samples. Restriction enzyme digestion was used to assess methylation of the MMP9 gene in 12 fresh periapical granuloma samples and 10 fresh radicular cyst samples. MMP2 and MMP9 messenger RNA transcript levels were measured by quantitative real-time polymerase chain reaction.ResultsAll periapical lesions and healthy mucosa samples showed partial methylation of the MMP2 gene; however, periapical granulomas showed higher MMP2 mRNA expression levels than healthy mucosa (P = .014). A higher unmethylated profile of the MMP9 gene was found in periapical granulomas and radicular cysts compared with healthy mucosa. In addition, higher MMP9 mRNA expression was observed in the periapical lesions compared with healthy tissues.ConclusionsThe present study suggests that the unmethylated status of the MMP9 gene in periapical lesions may explain the observed up-regulation of messenger RNA transcription in these lesions.