title: DNA damage in bone marrow cells induced by ultraviolet femtosecond laser irradiation.
abstract: BACKGROUND
  Research on the damaging effect of ultraviolet (UV) laser irradiation on the DNA of live organisms is still scarce, although UV lasers are increasingly being used in therapeutics and surgical treatment.
  
  
  OBJECTIVE
  In this study we investigated the effect of new-generation 205-nm femtosecond solid-state laser irradiation on the DNA of murine bone marrow cells in vitro.
  
  
  METHODS
  Mouse bone marrow cells in distinct plates were exposed to different doses of 205-nm femtosecond laser irradiation. Single-cell gel electrophoresis, or comet, assay was used for DNA damage measurement.
  
  
  RESULTS
  Our study revealed intensity-dependent genotoxic, genotoxic-cytotoxic, or cytotoxic impact of laser irradiation. The lowest doses we used (0.0175-0.105 J/cm(2)) induced DNA photodamage in irradiated cells directly, medial doses (0.175 and 0.35 J/cm(2)) caused both direct damage of genetic material and irreversible injury of cell's structure whereas the highest doses (1.05-4.2 J/cm(2)) caused the death of most irradiated cells. It is worrisome that even comparatively low doses of irradiation were genotoxic. Exposure to the lowest-intensity irradiation (0.0175 J/cm(2)) caused a highly significant (p < 0.0001) increase in DNA strand breaks of bone marrow cells: the mean ± SEM %DNA score in the comet tail was 9.96 ± 0.56 compared with 3.58 ± 0.80 for controls. Investigation of the effects of low and medial intensities of irradiation showed a dosage-effect relationship of R(2) = 0.84, P < 0.01.
  
  
  CONCLUSIONS
  New-generation 205-nm femtosecond laser irradiation produced a genotoxic effect by inducing strand breaks in the DNA of murine bone marrow cells in vitro. Research on the possible genotoxic effects of this laser on corneal and skin epithelial cells in vivo is needed.
authors.affiliation: Department of Botany and Genetics, Vilnius University, Vilnius, Lithuania. vaidotas.morkunas@gf.vu.lt
authors.forename: Vaidotas
authors.initials: V
authors.lastname: Morkunas
authors.forename: Osvaldas
authors.initials: O
authors.lastname: Ruksenas
authors.forename: Mikas
authors.initials: M
authors.lastname: Vengris
authors.forename: Egle
authors.initials: E
authors.lastname: Gabryte
authors.forename: Egle
authors.initials: E
authors.lastname: Danieliene
authors.forename: Romas
authors.initials: R
authors.lastname: Danielius
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000528:radiation effects*; D020552:Comet Assay; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D005260:Female; D066298:In Vitro Techniques; D053844:Lasers, Solid-State; D051379:Mice; D008807:Mice, Inbred BALB C; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D004247:DNA