Expression of circadian clock genes during differentiation of rat dental papilla cells in vitro

The circadian clock is involved in many physiological processes including teeth development. The expression of circadian core clock genes was observed in various tissues, but their role in odontoblasts is unclear. The aim of this study was to investigate the circadian core clock gene expressions of dental papilla cells (DPCs) during the odontogenic differentiation. Primary DPCs were obtained from the first molar dental papilla of neonatal rats and cultured in osteogenic (OS) medium for differentiation in vitro. Reverse transcription and quantitative PCR was performed to assess the mRNA levels of the circadian core clock genesBmal1, Per2, Cry1, Clock, Rev-erb alpha andRor alpha. Western blotting was performed to assess the protein levels of BMAL1 and PER2. The results showed that apparent oscillatory expression patterns ofPer2, Cry1, Rev-erb alpha could be observed in DPCs, whether differentiated or not. The protein level of BMAL1 was significantly increased and PER2 was decreased during odontogenic differentiation. Taken together, these findings demonstrate that circadian rhythmicity of known core clock genes exist in cultured DPCs in vitro, and the expression of genes change during differentiation process.