Abstract
A core group of circadian genes regulate the circadian rhythms in mammalian cells. However, the mammalian cellular circadian rhythm in photobiomodulation remains unknown. A lot of evidence has shown that >20% of expressed mRNAs in bone stissues oscillate in a circadian manner. The aim of this paper is to investigate the mRNA expression of period 1 (per 1) in murine bone marrow-derived mesenchymal stem cells (BMSCs) which were irradiated by 635 nm red laser light. The cells were seeded in 35mm tissue-culture dishes at a density of 8 × 104 cells/dish and cultured in Dulbecco’s modi?ed Eagle’s medium (DMEM). BMSCs were irradiated once by 635 nm red light with radiation energies 0 J/cm2, 1 J/cm2, 4 J/cm2. mRNA expression of per 1 via Semi-Quantitative Real-time RT-PCR at 0h, 6 h, 12 h, 18 h, 24 h. The genes displayed a oscillatory period of nearly 24 hours. And 635 m laser light changed the mRNA expression of per 1. We conclude that red light irradiation can affect the circadian rhythm of BMSCs.
Highlights
Low-level laser therapy (LLLT) was introduced by the work of Mester et al [1] more than 30 years ago
Both the ends of mice femurs and tibias were cut away from the epiphysis and the bone marrow was flushed out with a syringe with 0.5 mL of Dulbecco’s modified Eagle minimal essential medium (DMEM)/low glucose supplemented with 10% fetal calf serum (FCS) (Hyclone, UT, USA), 100U/Ml was placed into T-25 tissue (Greiner, Frickenhausen, Germany) culture flasks at 37 ̊C in a 5% CO2 atmosphere
Kushibiki et al in their study showed that laser irradiated mesenchymal stem cells (MSCs) altered the intracellular localization of the circadian rhythm protein CRY1 [12]
Summary
Low-level laser therapy (LLLT) was introduced by the work of Mester et al [1] more than 30 years ago. It has been shown to modulate cellular proliferation [2]-[5], in a recent study by Abramovitch-Gottlib et al [6], a low-energy laser was found to stimulate the osteogenic phenotype of mesenchymal stem cells (MSCs) in a three-dimensional biomatrix. The core circadian rhythms genes include two cryptochrome genes (Cry and Cry2), three homologs of the period genes (Per, Per, and Per3), and the transcriptional activator genes Clock and Bmal (brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1) [8]. This oscillator is thought to be composed of interlocking auto regulatory feedback loops, the transcription/translation feedback loop. The PER1 and PER2 and CRY1 and CRY2 act as negative regulators of transcription driven by the BMAL1-CLOCK heterodimer
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