Influence of Two Different Fluences on Laser Photobiomodulation of Wound Healing in Diabetic and Nondiabetic Mice

Abstract

Background: Laser irradiation of wounds in mice and rats was shown in previous studies to stimulate healing but in almost all the studies the wounds were not covered.Purpose: To compare the healing of covered wounds in diabetic and nondiabetic mice and the effect of laser irradiation 660 nm at two different fluences (energy densities).Method: A single wound 5‐mm diameter was made on the left flank of forty‐seven diabetic and twenty nondiabetic mice and covered with Tegaderm HP dressing (day 1). Wounds were irradiated 660 nm 20 s using a low power (18 mW) or high power (80 mW) laser starting immediately post‐wounding for 7 consecutive days, with non‐irradiated wounds as controls. Mice were euthanized on day 8, 10 or 14. Wound specimens were cut and stained with haematoxylin and eosin, and examined by light microscopy.Results: Wound healing was impaired in diabetic mice. Tegaderm HP dressing had retarded contraction in a large proportion of diabetic mice (splinted the wounds) and to a lesser extent in nondiabetic mice. Healing of splinted wounds was delayed compared to unsplinted wounds, but laser irradiation at high power stimulated healing by re‐epithelization and granulation tissue formation. The fluence of low power laser was estimated to be about 1 J/cm2, while that of the high power laser was 3.7 to 5.0 J/cm2.Conclusion: Laser irradiation of wounds 660 nm with 1 J/cm2 had little effect on healing of wounds in diabetic and nondiabetic mice, whereas irradiation with 3.7 to 5.0 J/cm2 stimulated healing of wounds in diabetic mice most of which were splinted by the dressing.