THE ANALYSIS OF GENE EXPRESSION ASSOCIATED WITH ALVEOLAR BONE RESORPTION

Abstract

Alveolar bone resorption after tooth extraction is one of the problems that causes the difficulty in prosthetic treatment especially in mandible. Imbalance of gene expression plays an important role in bone remodeling process that leads to the atrophic mandible. RANKL, OPG, MMP9 CtsK TRAP and RUNX2 are known as the gene associated with the bone remodeling process. To examine the expression of the genes associated with the mandibular bone resorption, and to explore the differences in expression between the resorption levels and the alveolar bone of the impacted tooth, the bone samples were collected from the edentulous areas of the patients who underwent dental implant placement (n=18) and from the impacted tooth areas of the patient who had lower third molar surgical removal (n=7). The bone was homogenized then mRNA was isolated before converting to cDNA. cDNA was used with the specific primers for our interested genes in quantitative RT-PCR. The bone dimensions were measured in CT scan at the implant site of the edentulous areas (n=18). The edentulous bone resorption levels were classified by the ratio of total bone height to basal bone height: <3.0 = high resorption bone (n = 9) and >3.0 = low resorption bone (n = 9). All target gene expressions were significantly different between the edentulous bone groups and the impacted tooth alveolar bone (Kruskal-Wallis test, p < 0.05). The highest median of RANKL, OPG, MMP9 CtsK TRAP and RUNX2 were in the impacted tooth alveolar bone followed by the low resorption bone and the high resorption bone, respectively. The ratio of RANKL to OPG expression was highest in alveolar bone of the impacted tooth which significantly higher than the low resorption bone (Mann-Whitney U test, p<0.05). The high resorption bone had the ratio of RANKL to OPG expression significantly higher than the low resorption bone (Mann-Whitney U test, p<0.05). The relationship between the CT measurement data and the gene expressions has shown the significant positive correlation between the crestal bone width and the RANKL/OPG ratio (Pearson’s correlation, p<0.01). Our analysis provided the data the might be useful to classify the patient who get risk of bone resorption to have the proper treatment procedures such as dental implant assisted removable denture.