title: Time-dependent responses of wounded human skin fibroblasts following phototherapy.
abstract: OBJECTIVE
  The penetration and distribution of laser light in target tissue is dependent on the wavelength of the light. One problem with most of the published data on laser irradiation is that most studies do not record the duration between the exposure and the evaluation. This study aimed to establish if the dose, wavelength or duration of effect (1h or 24h) influences the biological responses of irradiated fibroblasts.
  
  
  METHODS
  The study established cellular responses of normal and wounded human skin fibroblasts to helium-neon (632.8 nm), diode (830 nm) and Nd:YAG (1064 nm) laser irradiation using one exposure of 5 J/cm(2) or 16 J/cm(2) on day 1 and again on day 4. Cellular responses to laser irradiation were evaluated by measuring changes in cell viability (ATP viability and caspase 3/7 activity) and cell proliferation (ALP enzyme activity and bFGF expression), 1h and 24h post irradiation.
  
  
  RESULTS
  Wounded cells exposed to 5 J/cm(2) using 632.8 nm showed an increase in ATP viability after 1h, a decrease in caspase 3/7 activity after 24h and an increase in cell proliferation after 24h. The results suggest that changes in parameters such as ATP viability should be observed directly after laser irradiation (1h) whereas other parameters such as caspase 3/7 activity, bFGF expression and ALP enzyme activity should be measured at least 24h after the final exposure.
  
  
  CONCLUSIONS
  This study confirms that the duration of effect should be included as one of the main laser parameters when reporting on the effects of laser irradiation. It is important to establish time-dependent responses as the results may provide an understanding of the cellular responses following laser irradiation.
authors.affiliation: Laser Research Group, Faculty of Health Sciences, University of Johannesburg, P.O. Box 17011, Doornfontein, Johannesburg 2028, South Africa. dhawkins@uj.ac.za
authors.forename: Denise H
authors.initials: DH
authors.lastname: Hawkins
authors.forename: Heidi
authors.initials: H
authors.lastname: Abrahamse
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D049109:Cell Proliferation / Q000528:radiation effects*; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000528:radiation effects*; D006371:Helium; D006801:Humans; D053685:Laser Therapy; D007834:Lasers / Q000009:adverse effects; D008027:Light; D009354:Neodymium; D009356:Neon; D010789:Phototherapy / Q000009:adverse effects*; D013997:Time Factors; D014945:Wound Healing / Q000502:physiology / Q000528:radiation effects*
chemical_list: D006371:Helium; D009354:Neodymium; D009356:Neon; D000255:Adenosine Triphosphate; D020169:Caspases