Profiling of Differentially Expressed Genes in Peri-implantitis and Periodontitis in vivo by Microarray Analysis

The purpose of this study was to compare gene expression profiles of peri-implantitis and periodontitis to elucidate potential differences at the molecular level. With the help of microarray analysis, genome-wide gene expression of inflamed peri-implant granulation tissue, inflamed and healthy periodontal tissues (n=48 patients) were compared and the data were validated by real-time reverse transcription polymerase chain reaction. After highlighting different gene classes, we focused on the extracellular matrix-receptor interaction pathway and gene expression of extracellular matrix molecules, their receptors and matrix degrading enzymes. Only genes of non-fibril-forming collagens (types IV, VI, VII, and Q) were increased in peri-implantitis compared to periodontitis, whereas the expressions of two fibril-forming collagens (types III and K) were decreased in peri-implantitis, which suggested that peri-implant tissue re-models faster than periodontal tissue in vivo. Furthermore, cathepsin D and cathepsin S seem to participate in the destruction of peri-implant connective tissue. Despite their clinical similarities, the present investigation demonstrated that peri-implantitis and periodontitis are two different disease entities at least at the messanger ribonucleic acid level. The data provide insight for future studies aimed at dissecting the pathogenesis of peri-implant inflammation.