Effect of low intensity monochromatic light therapy (890 nm) on a radiation-impaired, wound-healing model in murine skin.
BACKGROUND AND OBJECTIVE: The use of low intensity laser and monochromatic light diodes as a therapeutic modality has become popular in a variety of clinical applications, including the promotion of wound repair. Despite this, the clinical evidence base for such application remains sparse; in contrast, recent studies have demonstrated a number of quantifiable photobiological effects associated with such therapy. In the present study, the effect of low intensity monochromatic light irradiation (MLI) at various radiant exposures upon a radiation-impaired wound model in murine skin was investigated. STUDY DESIGN/MATERIALS AND METHODS: Male Balb/c mice (n = 50; age matched at 10 weeks) were randomly allocated to five experimental groups (n = 10 each group). In Group 1, mice were left untreated; in Groups 2-5, a well-defined area on the dorsum was exposed to 20 Gy X-ray irradiation. At 72 hours postirradiation, all mice were anaesthetised and a 7-mm-square area wound was made on the dorsum. All wounds were videotaped alongside a marker scale until closure was complete. In Groups 3-5, mice were treated with MLI (0.18, 0.54, and 1.45 J/cm2, respectively) three times weekly using a GaAlAs 890 nm multidiode (n = 60) array unit (270 Hz; maximum rated output, 300 mW; Anodyne, Denver, CO). Subsequently, the area of each wound was measured from video using an image analysis system (Fenestra 2.1), and results were analysed using repeated measure and one-factor ANOVA statistical tests. RESULTS: X-ray irradiation caused a significant delay (P = 0.0122) in healing by day 7. MLI at 0.18 J/cm2 and 0.54 J/cm2 had no effect upon the rate of wound closure. However, a highly significant (P = 0.0001) inhibition occurred following MLI irradiation at 1.45 J/cm2 by day 16. CONCLUSION: These findings provide little evidence of the putative stimulatory effects of monochromatic light irradiation in vivo, but, rather, reveal the potential for an inhibitory effect at higher radiant exposures.