Circadian Clock and Bone Biology

Publication date: Available online 1 July 2017
Source:Journal of Oral Biosciences
Author(s): Takao Hirai
BackgroundMany metabolic and physiological processes display circadian oscillations that are controlled by the internal circadian clock system. A molecular clock system is generated by the transcriptional-translational feedback loops of clock genes. Circadian oscillators reside in peripheral tissues where they receive timing cues from the central clock in the suprachiasmatic nucleus (SCN). Circadian rhythms have also been identified in bone and cartilage.HighlightRecent findings demonstrated that bone metabolic functions of the major cell types namely osteoblasts, chondrocytes, and osteoclasts, are closely related to an intrinsic biological rhythm, named the circadian clock. Several studies have also shown that clock genes play significant roles in bone formation and resorption. Adrenergic receptor signaling in osteoblasts was previously reported to synchronize clock genes as well as genes that are important for osteoblast function such as Ptgs2 gene encoding prostaglandin G/H synthetase 2, which is a late-limiting enzyme for prostaglandin synthesis. Since the circadian clock regulates key molecules in cellular functions of osteoblasts and osteoclasts, this system may be closely involved in the cellular functions associated with bone remodeling.ConclusionThis review focuses on the latest knowledge on the molecular mechanisms of biological clocks and their roles in bone biology, indicating the potential of this clock system in the treatment of bone disorders.



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