2013 Volume 56 Issue 1 Pages 9-16
Purpose: To investigate in vivo responses of macrophages and dendritic cells to mineral trioxide aggregate (MTA), the expression of molecules associated with macrophages/dendritic cells was examined in MTA-implanted rat subcutaneous tissue by means of immunohistochemistry and quantitative gene expression analysis. Methods: Silicone tubes containing mixed MTA (ProRoot MTA) or a calcium hydroxide-based cement (Life) were subcutaneously implanted into the back of male Wistar rats. Solid silicone rods of similar size served as controls. At 14 days after the implantation, connective tissue surrounding the implants was retrieved and processed for double immunoperoxidase staining using ED1 (reactive to macrophages and dendritic cells) and OX6 (reactive to major histocompatibility complex class II molecules), and the number of ED1+/OX6+ and ED1+/OX6- cells was enumerated. Real-time polymerase chain reaction (PCR) analysis was also carried out to quantify the mRNA expression levels of CD163 (a marker for tissue repair (M2) macrophages) and CD34 (expressed in endothelial cells and subpopulation of dermal dendritic cells) in the subcutaneous connective tissue. Statistical differences were analyzed by the Mann-Whitney U-test with Bonferroni correction. Results: In the MTA-implanted tissue, ED1+/OX6+ cells showed a significantly higher density compared with the other groups (p<0.05), and ED1+/OX6- cells showed a significantly higher density compared with the Life-implanted tissue (p<0.05). The expression levels of CD34 and CD163 mRNAs in the MTA-implanted tissue were significantly higher than those in the Life-implanted and control tissues (p<0.05). Conclusion: In the subcutaneous connective tissue of rats, MTA induced the infiltration of a significantly higher density of CD68+ cell subpopulations (ED1+/OX6+ and ED1+/OX6- cells) and significantly higher levels of CD34 and CD163 mRNAs, as compared with Life. These results suggest that wound healing/tissue repair processes involving macrophages participate in the biological tissue reaction to MTA.
