Effects of BMAL1 on dentinogenic differentiation of dental pulp stem cells via PI3K/Akt/mTOR pathway

This study aimed to investigate the effect of the circadian clock gene Bmal1 on dentinogenic differentiation of dental pulp stem cells (DPSCs) under inflammatory conditions.Dental pulp stem cells were isolated from the pulp tissue of the healthy donor and were then stimulated with different concentrations of lipopolysaccharide (LPS) to mimic inflammatory conditions. Real-time polymerase chain reaction was used to detect the gene expression of circadian clock genes Bmal1, Clock, Per1, Per2, Cry1, and Cry2. Western blot (WB) was applied to analyse the protein expression of circadian clock proteins (BMAL1, CLOCK) and dentinogenic differentiation-related proteins (DSPP, DMP1). In addition, the apoptosis and osteogenic differentiation of DPSCs were also analysed in the presence of different concentrations of LPS.The expression of circadian clock genes of DPSCs significantly changed in an inflammatory environment. WB analysis shows that BMAL1 is relevant to the dentinogenic differentiation of DPSCs. In low concentrations of LPS-mimicked inflammatory conditions, the expression of BMAL1 increased and promoted the dentinogenic differentiation of DPSCs. However, under high concentrations of LPS-mimicked inflammatory conditions, the expression of BMAL1 decreased and inhibited the dentinogenic differentiation of DPSCs. Moreover, the effects of BMAL1 on dentinogenic differentiation of DPSCs may be through PI3K/Akt/mTOR pathway.This study showed that the circadian clock gene Bmal1 affected dentinogenic differentiation of DPSCs, providing a new insight for clinical stem cell-based restorative dentinogenesis therapies.