PER2 Promotes Odontoblastic/Osteogenic Differentiation of Dental Pulp Stem Cells by Modulating Mitochondrial Metabolism

Human dental pulp stem cells (hDPSCs) possess remarkable self-renewal and multilineage differentiation ability. PER2, an essential circadian molecule, regulates various physiological processes. Evidence suggests that circadian rhythm and PER2 participate in physiological functions of DPSCs. However, the influence of PER2 on DPSCs' differentiation remains largely unknown. This study aimed to explore the effect and potential mechanism of PER2 on hDPSCs' differentiation. Dental pulp tissues were extracted, and hDPSCs were cultured for in vitro and in vivo experiments. Dorsal subcutaneous transplantation was performed in 6-week-old male BALB/c mice. The hDPSCs' odontoblastic/osteogenic differentiation was assessed, and mitochondrial metabolism was evaluated. The results indicated PER2 expression increasing during hDPSCs' odontoblastic/osteogenic differentiation. Gain- and loss-of function studies confirmed that PER2 promoted alkaline phosphatase (ALP) activity, mineralized nodules deposition, mRNA expression of DSPP, DMP1, COL1A1 and protein expression of DSPP and DMP1 in hDPSCs. Furthermore, PER2 enhanced collagen deposition, osteodentine-like tissue formation and DSPP expression in vivo. Mitochondrial metabolic evaluation aimed to investigate the mechanism of PER2-mediated hDPSC odontoblastic/osteogenic differentiation, which showed that PER2 increased ATP synthesis, elevated mitochondrial membrane potential and changed expression of proteins regulating mitochondrial dynamics. This study demonstrated that PER2 promoted hDPSCs' odontoblastic/osteogenic differentiation, which involved mitochondrial metabolic change.