Effects of cold laser therapy on infected wound healing in mice

Despite a lot of researchers were suggested that cold laser therapy can enhance healing by reducing inflammation, increase cells proliferation, enhanced collagen synthesis, its use still controversial .The optimum parameters have been still not defined .we aimed to study the effect of cold laser therapy at a constant power density (Irradiance) at different illumination time (5,15minutes) on healing of noninfectedand infected wounds. Ninety animals with cutaneous incisional wound were divided into 12 irradiation groups, six groups for each noninfected and infected animal, and 30 animals as nonirradiated controls divided into noninfected and infected groups. All groups irradiated with red Laser light 635nm with constant irradiance 9.0 mw/cm2, power= 60mw, continuous wave started immediately after surgery and repeated every day for 3,5,10 days using lens expander to cover the wound area (2.7J/cm2) for 5 minutes and (8 J/cm2) for 15 minutes. Wound healing was studied by calculating the percentage of wound closure and histological evaluation. The animals were killed either at 3, 5, or 10 days after irradiation. Specimen were taken, embedded in paraffin and sectioned, stained for histological analysis. Cold laser therapy clearly stimulates wound contraction, granulation tissue, collagen formation and reduces inflammation in both irradiated groups (infected and noninfected) groups .Polymorph nuclear infiltrate was lower in both noninfected irradiated groups at (2.7J/cm2, 8.0J/cm2) compared with the control. The synthesis of collagen was enhanced in both noninfected groups compared with noninfected controls. Significant difference in the newly formed granulation tissue in the irradiated groups was recorded on five days after injury compared to noninfectedcontrols. On five days, the response of non infected wounds at (8.0J/cm2) was more than the group exposed at (2.7J/ cm2). On day 10, good response was noted in both irradiated noninfected groups compared to controls. On day 5, the irradiated groups were more responsive at (8.0J/cm2) compared to infected controls. At day10, infected irradiated groups had complete healing compared to incomplete healing in infected control group. We concluded that the most important parameter in determining theoptimal light delivering regimen is irradiated or illuminated time.