Identification of specific gene expression in peri-implant tissue by microarray analysis

Objectives: Implant placement entails disruption of the epithelial continuity and it can lead to various complications. Therefore, the area of mucosal penetration is particular interest clinically. The peri-implant soft tissue in this area comprises peri-implant epithelium (PIE) and peri-implant connective tissue. PIE, which interfaces with the body of the implant, originates in oral mucosal epithelium (OME) during the process of wound healing and has a similar environment of junctional epithelium (JE) of the natural tooth. The aim of this study is to compare gene expression in PIE with OME and JE using microarray analysis, and to identify specific genes in PIE.
Methods: The maxillary first molars (M1) were extracted from 4 week old rats and titanium alloy implants immediately placed in the extraction sockets and 4 weeks after surgery, PIE were extracted. OME at M1 area after 4 weeks tooth extraction and JE of M1 at 8 week old were harvested as control groups. Total RNA were isolated from each three samples and hybridized with GeneChip rat genome 230 2.0 array for microarray analysis. The comparison of comprehensive gene expression among PIE, OME and JE were performed by Genespring software. All experiments were performed according to the Guidelines for the Treatment of Animals at Tokyo Dental College (approval number, 243007).
Results: Up-regulated genes (fold change >2.0) in PIE based on OME were 324, and on JE were 320. On the other hand, down-regulated genes (fold change >2.0) in PIE compared to OME were 117, and to JE were 100. Furthermore, 142 genes (fold change >2.0) was identified as specific gene in PIE by comparison with both control group. The pathway analysis of them were detected “IL-5 signaling pathway”, “Statin pathway” and “Integrin-mediated cell adhesion” (p <0.01). The significantly up-regulated genes in PIE were contained Ifitm1, Sepinb3, S100a9, Aif1 and Psmb9 (fold change compared to both control group >4.0).
Conclusions: More than a hundred genes were recognized as specifically expressed gene in PIE, and they were suggested to relate tumor cell invasion (Ifitm1, Serpinb3), natural immunity (S100a9) and allograft inflammatory (Aif1). These results have a possibility to be a useful data base for the research to improve defensive mechanism of peri-implant soft tissue.