Microarray-analysis of Pulpal Gene Expression in Response to Cavity Preparation

Objectives: Reparative dentin is deposited in reaction to various stimuli such as caries or restorative procedures. However, molecular mechanisms of reparative dentin formation have not yet been clarified, and a detailed analysis of genes involved in pulpal healing may help to elucidate regulatory pathways of reparative dentinogenesis. The aim of this study was to investigate the gene expression in response to cavity preparation in rat pulp comprehensively using a microarray analysis. Methods: Cavities were prepared on the coronary part of maxillary first molars of 9-week-old Wistar rats and restored with glass-ionomer cements. The teeth were extracted immediately (day 0), or 1 or 3 days after cavity preparation, and total RNA obtained from the pulp was subjected to GeneChip expression analysis system (Rat Genome 230 2.0, Affymetrix, USA). The expression levels of genes were compared between the experimental groups and the pulp of intact teeth served as the control, and up- and down-regulated genes with at least two-fold change were determined using DNA MicroArray Viewer Software (Kurabo, Japan). Results: A total of 308, 329, and 337 transcripts were up-regulated, and 203, 123, and 169 transcripts were down-regulated on day 0, 1, and 3, respectively. The up-regulated transcripts included those related to inflammatory response, differentiation, and development depending on the Biological Process in Gene Ontology. Fifty-nine transcripts were continuously up-regulated at the two or three consecutive time points, and 10 transcripts were continuously down-regulated. Conclusion: The comprehensive and serial analysis of gene expression in vivo demonstrated involvement of many consecutively up- and down-regulated transcripts in the healing process after cavity preparation. The candidate genes responsible for induction of reparative dentin formation may be included among them. Supported by a Grant-in-aid for Scientific Research (19791397) from the Ministry of Education, Culture, Sports, Science and Technology.