title: Low-intensity pulsed laser irradiation affects RANKL and OPG mRNA expression in rat calvarial cells.
abstract: OBJECTIVE
  This study aimed to investigate the effect of low-intensity pulsed laser (LIPL; 650 nm, 2 mW) irradiation on mRNA expression of receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG) in rat calvarial cells.
  
  
  METHODS
  Cultured cells were treated with LIPL irradiation of 1.14 J/cm(2) (group A) or 2.28 J/cm(2) (group B), and non-irradiated cells (group C) were used as controls. The changes in cell numbers, alkaline phosphatase (ALP) activity, RANKL, and OPG mRNA expression in the three study groups was determined using MTT, UV/VIS spectrophotometry, and RT-PCR analyses.
  
  
  RESULTS
  The cell numbers in groups A and B increased significantly (7.52% and 8.80%, respectively), as did ALP activity (71.95% and 88.20%, respectively), compared with group C (p < 0.001). Meanwhile, RANKL and OPG mRNA expression in group A were 51.06% lower and 3.35 times higher, respectively, than those seen in the controls (p < 0.05), and the RANKL:OPG mRNA ratio in group A was 81.82% lower than that in group C (p < 0.005).
  
  
  CONCLUSIONS
  LIPL irradiation may directly promote osteoblast proliferation and differentiation, and indirectly inhibit osteoclast differentiation, by downregulating the RANKL:OPG mRNA ratio in osteoblasts. Thus LIPL irradiation may play an important role in bone remodeling, and should be valuable for the treatment of bone diseases such as osteoporosis.
authors.affiliation: School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China. xumin@hkbu.edu.hk
authors.forename: Min
authors.initials: M
authors.lastname: Xu
authors.forename: Tietao
authors.initials: T
authors.lastname: Deng
authors.forename: Feizhi
authors.initials: F
authors.lastname: Mo
authors.forename: Bin
authors.initials: B
authors.lastname: Deng
authors.forename: Wingho
authors.initials: W
authors.lastname: Lam
authors.forename: Pingxiang
authors.initials: P
authors.lastname: Deng
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Zhang
authors.forename: Songhao
authors.initials: S
authors.lastname: Liu
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D007834:Lasers; D028022:Low-Level Light Therapy; D023421:Models, Animal; D053244:Osteoprotegerin / Q000096:biosynthesis*; D053245:RANK Ligand / Q000096:biosynthesis*; D012333:RNA, Messenger; D051381:Rats; D017207:Rats, Sprague-Dawley; D012886:Skull / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects*
chemical_list: D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger