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

Abstract

Aim: 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.Methodology: 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. Results: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 LPSmimicked 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. Conclusions: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.

Circadian clock—A promising scientific target in oral science

“…Odontoblasts are the target cells of various hormones, and these hormones are regulated by clock genes, indicating that odontogenesis is regulated by the circadian clock from the perspective of hormone levels ( Zheng et al, 2014 ). In the three different embryonic phases of murine dental pulp cells, only Clock, Pers, and Bmal1 at low but variable levels were detected ( Xu et al, 2022 ). Rev-erbαshowed oscillated expression in a 24 h cycle in cementoblast cell line OCCM-30, which suggested the circadian rhythms exist in cementoblasts.…”

“…Dental pulp-derived stem cells show rhythmic oscillations of Bmal1, Rer-erbα, and Per2 under mechanical stretching ( Tao et al, 2016 ). Dysfunction of the circadian clock affects dentin apposition and mineralization, the effects of BMAL1 on dentinogenic differentiation of DPSCs via PI3K/Akt/mTOR pathway ( Xu et al, 2022 ), but the additional specific mechanisms underlying differential expression of circadian clock genes on tooth development needs to be further studied ( Figure 2 ).…”

Effect of lipoxin A4 on the osteogenic differentiation of periodontal ligament stem cells under lipopolysaccharide‐induced inflammatory conditions

“…PI3K/AKT pathway has been demonstrated to play a positive role in migration and proliferation of stem cells by mediating actin cytoskeleton reorganization [33] and upregulating the expression of proteins that regulate cellular processes like cyclin D1 [34]. Additionally, PI3K/AKT pathway is involved in the differentiation of stem cells by regulating downstream signals including SOX2 [35], mTOR [36] and GSK3β [37]. Accumulating evidence suggests that activating the PI3K/AKT pathway can contribute to osteogenesis [38][39][40][41].…”

Role of alpha smooth muscle actin in odontogenic differentiation of dental pulp stem cells

“…Xu et al. reported that the PI3K/Akt/mTOR pathway regulates odontogenic differentiation of DPSCs via the effect of Bmal [47]. Al‐Habib et al.…”

“…Furthermore, the mTOR signaling pathway modulates the lineage differentiation of mesenchymal stem cells, including osteogenesis, adipogenesis, and myogenesis [46]. Xu et al reported that the PI3K/Akt/mTOR pathway regulates odontogenic differentiation of DPSCs via the effect of Bmal [47]. Al-Habib et al reported that inhibition of the mTOR pathway diminishes odontogenic/osteogenic, adipogenic, and neurogenic differentiation of DPSCs [48].…”