Mineral Trioxide Aggregate Induces Bone Morphogenetic Protein-2 Expression and Calcification in Human Periodontal Ligament Cells

Abstract Introduction Mineral trioxide aggregate (MTA) is a therapeutic, endodontic repair material that is reported to exhibit calcified tissue-conductive activity although the mechanisms remain unclear. We hypothesize that the dissolution of calcium from MTA into the surrounding environment may play an important role in the osteoblastic/cementoblastic differentiation of human periodontal ligament cells (HPLCs). Methods Two populations of HPLCs were obtained from two patients, respectively, and were cultured in the presence or absence of MTA discs and/or CaCl2 in order to investigate calcium release, calcification activity, calcium-sensing receptor (CaSR) gene expression and bone morphogenetic protein-2 (BMP-2), and BMP-2 receptor protein and gene expression. Results MTA released a substantial accumulation of calcium (4 mmol/L) within 14 days into culture media. After 4 weeks, the two populations of HPLCs independently exhibited calcification as well as BMP-2 distribution in the vicinity of MTA. HPLCs inherently expressed genes encoding for the CaSR and BMP-2 receptors. Exogenous CaCl2 media supplementation induced CaSR gene expression in HPLCs and calcification and BMP-2 synthesis throughout the entire HPLC cultures, whereas MgCl2 had no effect. Both MTA and CaCl2 stimulated BMP-2 gene expression above that of baseline levels. Conclusion Here we show the first report showing that HPLCs cocultured directly with MTA up-regulated BMP2 expression and calcification. These results may be through CaSR interactions that were potentially activated by the release of calcium from MTA into the culture environment.