Prolonged bioluminescence monitoring in mouse ex vivo bone culture revealed persistent circadian rhythms in articular cartilages and growth plates.
The bone is a metabolically active organ which undergoes repeated remodeling cycles of bone resorption and formation. In this study, we revealed a robust and extremely long-lasting circadian rhythm in ex vivo culture maintained for over six months from the femoral bone of a PERIOD2(Luciferase) mouse. Furthermore, we also identified robust circadian clocks in flat bones. High- or low-magnification real-time bioluminescence microscopic imaging revealed that the robust circadian rhythms emanated from the articular cartilage and the epiphyseal cartilage within the growth plate of juvenile animals. Stimulation by forskolin or dexamethasone treatment caused type 0 phase resetting, indicating canonical entraining properties of the bone clock. Together, our findings from long-term ex vivo culture revealed that "tissue-autonomous" circadian rhythm in the articular cartilage and the growth plate of femoral bone functions for several months even in an organ culture condition, and provided a useful in vitro assay system investigating the role of the biological clock in bone formation or development.
Department of Physiology and Systems Bioscience, Kyoto Prefectural University of Medicine, Kyoto, Japan ; Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan ; Department of Musculoskeletal Chronobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Naoki
N
Okubo
Yoichi
Y
Minami
Hiroyoshi
H
Fujiwara
Yasuhiro
Y
Umemura
Yoshiki
Y
Tsuchiya
Toshiharu
T
Shirai
Ryo
R
Oda
Hitoshi
H
Inokawa
Toshikazu
T
Kubo
Kazuhiro
K
Yagita
D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects / Q000378:metabolism; D057906:Circadian Clocks / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D005576:Colforsin / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D005260:Female; D005269:Femur / Q000187:drug effects / Q000378:metabolism*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006132:Growth Plate / Q000187:drug effects / Q000378:metabolism*; D008156:Luciferases / Q000235:genetics* / Q000378:metabolism; D008163:Luminescent Measurements; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D057054:Molecular Imaging; D056950:Period Circadian Proteins / Q000235:genetics* / Q000378:metabolism; D046509:Tissue Culture Techniques
D056950:Period Circadian Proteins; D005576:Colforsin; D003907:Dexamethasone; D008156:Luciferases