Time-dependent responses of wounded human skin fibroblasts following phototherapy

Background and objectiveThe 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 (1 h or 24 h) influences the biological responses of irradiated fibroblasts.Materials and methodsThe 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/cm2 or 16 J/cm2 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), 1 h and 24 h post irradiation.ResultsWounded cells exposed to 5 J/cm2 using 632.8 nm showed an increase in ATP viability after 1 h, a decrease in caspase 3/7 activity after 24 h and an increase in cell proliferation after 24 h. The results suggest that changes in parameters such as ATP viability should be observed directly after laser irradiation (1 h) whereas other parameters such as caspase 3/7 activity, bFGF expression and ALP enzyme activity should be measured at least 24 h after the final exposure.ConclusionThis 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.