Simvastatin Enhances Differentiation of Human Dental Pulp Stem Cells

Objectives: Statin, HMG-CoA reductase inhibitor, is known to promote osteogenesis. However, it is not clear whether statin promotes dentinogenesis, as well. The purpose of this study was to investigate the effects of statin on the behavior of human dental pulp stem cells (DPSCs). Methods: DPSCs were isolated from human third molars under approved guidelines and informed consent. DPSCs at 3 - 6 passages were used in this study and cultured with 1 µM simvastatin (statin), one of the commonly used statins. Cell proliferation was evaluated with MTS assay, and cell cycle was analyzed with FACS. Differentiation of DPSCs was confirmed with quantitative RT-PCR through the expression levels of osteocalcin(OCN)and dentin sialophosphoprotein (DSPP). Furthermore, DPSCs treated by statin was transplanted into immunocompromised mice to evaluate their hard tissue formation in vivo. BMP-2 (100 ng/ml) was used as a positive control. Statistical differences were analyzed by one-way ANOVA, followed by post-hoc test. Results: Statin suppressed cell proliferation significantly (p <0.0001, at day-5 culture against PBS), but BMP-2 did not. It is confirmed with FACS that this suppression was the result from accumulation in the sub-G1 phase of cell cycle. Gene expression analysis revealed that both OCN and DSPP were upregulated significantly when DPSCs were cultured for 14 days with statin (p <0.0001, against PBS). The upregulation caused by statin was much effective compared to that by BMP-2. From the results of in vivo transplantation, it is revealed that statin accelerated hard tissue formation. Conclusion: These results indicate that statin is a candidate for enhancer of DPSCs ¸ differentiation, possibly lead to acceleration of dentinogenesis. Supported by JSPS grant (17209062) and MEXT grant (19689038).