title: The effects of laser irradiation on osteoblast and osteosarcoma cell proliferation and differentiation in vitro.
abstract: OBJECTIVE
  The aim of this study was to investigate the effects of 670-nm, 780-nm, and 830-nm laser irradiation on cell proliferation of normal primary osteoblast (MC3T3) and malignant osteosarcoma (MG63) cell lines in vitro.
  
  
  BACKGROUND
  Some studies have shown that laser phototherapy is able to stimulate the osteogenesis of bone tissue, increasing osteoblast proliferation and accelerating fracture consolidation. It has been suggested that laser light may have a biostimulatory effect on tumor cells. However, the mechanism by which the laser acts on cells is not fully understood.
  
  
  METHODS
  Neonatal, murine, calvarial, osteoblastic, and human osteosarcoma cell lines were studied. A single laser irradiation was performed at three different wavelengths, at the energies of 0.5, 1, 5, and 10 J/cm(2). Twenty-four hours after laser irradiation, cell proliferation and alkaline phosphatase assays were assessed.
  
  
  RESULTS
  Osteoblast proliferation increased significantly after 830-nm laser irradiation (at 10 J/cm(2)) but decreased after 780-nm laser irradiation (at 1, 5, and 10 J/cm(2)). Osteosarcoma cell proliferation increased significantly after 670-nm (at 5 J/cm(2)) and 780-nm laser irradiation (at 1, 5, and 10 J/cm(2)), but not after 830-nm laser irradiation. Alkaline phosphatase (ALP) activity in the osteoblast line was increased after 830-nm laser irradiation at 10 J/cm(2), whereas ALP activity in the osteosarcoma line was not altered, regardless of laser wavelength or intensity.
  
  
  CONCLUSIONS
  Based on the conditions of this study, we conclude that each cell line responds differently to specific wavelength and dose combinations. Further investigations are required to investigate the physiological mechanisms responsible for the contrasting outcomes obtained when using laser irradiation on cultured normal and malignant bone cells.
authors.affiliation: Physical Therapy Department, Federal University of Sao Carlos, Sao Carlos, Brazil. a.renno@unifesp.br
authors.forename: A C M
authors.initials: AC
authors.lastname: Renno
authors.forename: P A
authors.initials: PA
authors.lastname: McDonnell
authors.forename: N A
authors.initials: NA
authors.lastname: Parizotto
authors.forename: E-L
authors.initials: EL
authors.lastname: Laakso
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation / Q000528:radiation effects*; D002460:Cell Line; D049109:Cell Proliferation / Q000528:radiation effects*; D002471:Cell Transformation, Neoplastic; D006801:Humans; D066298:In Vitro Techniques; D028022:Low-Level Light Therapy / Q000379:methods*; D051379:Mice; D010006:Osteoblasts / Q000378:metabolism / Q000528:radiation effects*; D010012:Osteogenesis / Q000528:radiation effects*; D012516:Osteosarcoma / Q000473:pathology / Q000532:radiotherapy*; D012886:Skull / Q000528:radiation effects; D014407:Tumor Cells, Cultured