Laser Photobiostimulation of Wound Healing: Defining a Dose Response for Splinted Wounds in Diabetic Mice

Background and Objectives: We have used a 660 nm, 80 mW laser diode in genetic diabetic mice to stimulate the healing of wounds covered with a Tegaderm HP dressing that causes a retardation of contraction (splinted wounds). The purpose of our study was to examine the effects of irradiating the wounds for different time intervals in order to determine a dose response relationship. Materials and Methods: A circular excisional wound was made on the left flank of diabetic mice using a 5-mm skin punch, and covered with a Tegaderm HP dressing. Mice were allocated to four groups in which wounds were irradiated 660 nm, 80 mW for 0, 10, 20, or 40 seconds each day for 7 days. In total, 51 mice were used. Wounds were harvested on day 14 and the healing assessed from hematoxylin-eosin stained sections examined by light microscopy. Results: The wounds were splinted in 40 of the mice, and splinting caused a retardation of healing. The findings for the four treatments showed that irradiation for 20 second/day for 7 days brought about the greatest extent of healing. The wounds healed mainly by re-epithelization and granulation tissue formation. This duration of irradiation represents an energy dose of 1.6 J per irradiation and, for an estimated area of irradiation of 32-43 mm(2), corresponds to an energy density of 3.7-5.0 J/cm(2). Conclusion: Irradiation with 660 nm, 80 mW at an energy density of 3.7-5.0 J/cm(2) each day for 7 days caused the maximal stimulation of healing in splinted wounds of diabetic mice. Lasers Surg. Med. 42:656-664, 2010. (C) 2010 Wiley-Liss, Inc.