title: A novel combination treatment to stimulate bone healing and regeneration under hypoxic conditions: photobiomodulation and melatonin.
abstract: Melatonin has anabolic effects on the bone, even under hypoxia, and laser irradiation has been shown to improve osteoblastic differentiation. The aim of this study was to investigate whether laser irradiation and melatonin would have synergistic effects on osteoblastic differentiation and mineralization under hypoxic conditions. MC3T3-E1 cells were exposed to 1% oxygen tension for the hypoxia condition. The cells were divided into four groups: G1-osteoblast differentiation medium only (as the hypoxic condition), G2-treatment with 50 μM melatonin only, G3-laser irradiation (808 nm, 80 mW, GaAlAs diode) only, and G4-treatment with 50 μM melatonin and laser irradiation (808 nm, 80 mW, GaAlAs diode). Immunoblotting showed that osterix expression was markedly increased in the melatonin-treated and laser-irradiated cells at 48 and 72 h. In addition, alkaline phosphatase activity significantly increased and continued to rise throughout the experiment. Alizarin Red staining showed markedly increased mineralized nodules as compared with only melatonin-treated or laser-irradiated cells at day 7, which significantly increased by day 14. Moreover, when melatonin-treated cells were laser-irradiated, the differentiation and mineralization of cells were found to involve p38 MAPK and PRKD1 signaling mechanisms. However, the enhanced effects of laser irradiation with melatonin were markedly inhibited when the cells were treated with luzindole, a selective melatonin receptor antagonist. Therefore, we concluded that laser irradiation could promote the effect of melatonin on the differentiation and mineralization of MC3T3-E1 cells under hypoxic conditions, and that this process is mediated through melatonin 1/2 receptors and PKRD/p38 signaling pathways.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, South Korea.
authors.forename: Jang-Ho
authors.initials: JH
authors.lastname: Son
authors.affiliation: Department of Oral Anatomy, School of Dentistry, Pusan National University, Yangsan, South Korea.
authors.forename: Bong-Soo
authors.initials: BS
authors.lastname: Park
authors.affiliation: Department of Oral Anatomy, School of Dentistry, Pusan National University, Yangsan, South Korea.
authors.forename: In-Ryoung
authors.initials: IR
authors.lastname: Kim
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, South Korea.
authors.forename: Iel-Yong
authors.initials: IY
authors.lastname: Sung
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, South Korea.
authors.forename: Yeong-Cheol
authors.initials: YC
authors.lastname: Cho
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, South Korea.
authors.forename: Jung-Soo
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Department of Oral and Maxillofacial Surgery, School of Dentistry, Pusan National University, Yangsan, South Korea. ydkimdds@pusan.ac.kr.|Dental Research Institute and Institute for Translational Dental Sciences, Pusan National University Dental Hospital, Pusan National University, Yangsan, South Korea. ydkimdds@pusan.ac.kr.|Department of Oral and Maxillofacial Surgery, Pusan National University Dental Hospital, Beomeori, Mulgeum, Yangsan, Kyoungnam, 626-770, South Korea. ydkimdds@pusan.ac.kr.
authors.forename: Yong-Deok
authors.initials: YD
authors.lastname: Kim
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001861:Bone Regeneration / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D002454:Cell Differentiation / Q000528:radiation effects; D003131:Combined Modality Therapy; D000860:Hypoxia / Q000503:physiopathology*; D054023:Lasers, Semiconductor / Q000627:therapeutic use*; D028022:Low-Level Light Therapy / Q000379:methods*; D008550:Melatonin / Q000627:therapeutic use*; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D010012:Osteogenesis / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D048051:p38 Mitogen-Activated Protein Kinases; D000469:Alkaline Phosphatase; D008550:Melatonin
keywords: Bone; Cell membrane; Cytokines; Differentiation; Receptor