Identification of Characteristic Gene Expressions in Peri-implant Connective Tissue

Objectives: Recently, identification of characteristic gene has been required understanding of pathological mechanisms and establishment a new therapy for some diseases. Peri-implantitis caused by weak soft tissue integration is known as one of the major complication in implant treatment. Characteristic gene expressions in peri-implant connective tissue (PICT) has not been clarified. The purpose of this study is to identify characteristic gene expression in PICT by comparing periodontal connective tissue (PCT) and oral mucosal connective tissue (OMCT) using microarray analysis.
Methods: Five-week-old male rats were used in this experiment. The upper first molars were extracted and titanium implants were placed in extraction socket for PICT groups or waiting closure of wound for OMCT groups. Four weeks after surgery, these samples were harvested. Sample for PCT groups were extracted from upper first molars of 9-weeks old rats. All samples of connective tissue area were microdissected by laser microdissection and total RNA extracted from them were hybridized with GeneChip Rat Genome 230 2.0 Arrays.
Results: The number of up-regulated genes with more than 2-fold change in PICT compared with PCT was 1190, and with OMCT was 1391. On the other hand, down-regulated genes (fold change>2.0) in PICT compared to PCT were 676, and to OMCT were 1099.Mmp13, Spp1 and Cybb were recognized as significantly up-regulated genes in PICT compared with PCT. Defb4, Stfa3 and Gjb6 were extracted as significantly up-regulated genes in PICT compared with OMCT.
Conclusions: More than a thousand genes were recognized as specifically up-regulated gene in PICT compared with PCT and OMCT. Furthermore, significantly up-regulated genes were suggested to relate extracellular matrix degradation (Mmp13), superoxide metabolic process (Cybb), defense response to bacterium (Defb4) and apoptosis process (GJB6).There is a possibility that these characteristic gene expressions are maintained structure homeostasis and defense mechanism in peri-implant soft tissue.