Objective: The aim of present study was to evaluate whether low-level laser therapy (LLLT) can reverse the impaired wound healing process in diabetic rats. Background data: Impaired wound healing in diabetic patients represents a major health problem. Recent studies have indicated that LLLT may improve wound healing in diabetic rats, but the optimal treatment parameters are still unknown. Materials and methods: Male SpragueDawley rats (n = 21) were randomly divided into three groups: a healthy control group, a diabetic sham-treated group, and a diabetic LLLT-treated group. Diabetes mellitus was then induced by streptozotocin administration to the two diabetic groups. One 4 cm long full thickness skin incision and one full thickness circular excision (diameter = 4 mm) were performed on the back of each rat. An infrared 810 nm laser with an output of 30 mW, a power density of 30 mW/cm 2 , and a spot size of 1 cm 2 was used to irradiate each wound for 30 sec (daily dose of 0.9 J/cm 2 /wound/day). Results: In diabetic rats, the histology of LLLT-treated excisions revealed a similar healing response to that in nondiabetic controls, with significantly more mature granulation tissue than in the sham-treated diabetic control group. LLLT reduced the loss of tensile strength, and increased the incision wound stiffness significantly compared with sham-irradiated rats, but this did not achieve the same level as in the nondiabetic controls. Conclusions: Our study demonstrates that infrared LLLT can improve wound healing in diabetic rats. Nevertheless, further research needs to be performed to evaluate the exact underlying mechanism and to further optimize LLLT parameters for clinical use.

ABSTRACT:The complexity of the wound healing process, which is still poorly understood, prompted us to perform an immunohistochemical investigation using rat skin as an in vivo model. Fifteen Sprague-Dawley rats were included in the experiment. Two round full thickness wounds, 4 mm in diameter, were made on the backs of all rats. Haematoxylin and eosin basic staining as well as antibodies against wide spectrum keratin, keratin 10, keratin 14, α-smooth muscle actin, vimentin, fibronectin, collagens Type 1 and 3, and the transcription factor Sox-2 were applied to paraffin and frozen sections of skin wound specimens two, six and fourteen days after surgery, respectively. New hair follicles with Sox-2-positive cells were present after fourteen days; keratin/vimentin positivity was restricted to specimens of day two. Collagen-3 expression prevailed over collagen-1 expression at all evaluated time intervals, except in the uninjured part of the dermis. In conclusion, rat skin wound healing is a dynamic process which can serve as a model for studying phenomena such as cell-cell interactions and transitions in vivo.