Comparison of the photostimulatory effects of visible He-Ne and infrared Ga-As lasers on healing impaired diabetic rat wounds

Background and Objectives: In this study, the ability of photostimulation to promote healing of impaired wounds was investigated using a Ga-As laser in rats with experimental diabetes and the results were compared with previously reported findings of the effects of a He-Ne laser on the repair of healing-impaired diabetic rat wounds [1]. Study Design/Materials and Methods: Diabetes was induced in male rats by streptozotocin injection following which two full thickness punch wounds of 6-mm diameter were created in the skin, one on either side of the spine of each animal. The left wound of each animal was treated with infrared radiation at 904 nm produced by a Ga-As laser at an energy density of 1.0 J/cm(2). The right wound of each animal served as the control. The wounds were treated with a laser 5 days a week for 3 weeks. Following animal sacrifice, the strips of skin containing the wound sites were collected and analyzed. Results: The results from the biomechanical analysis indicated that the Ga-As laser used in this study significantly increased wound tensile strain and toughness compared to the control wounds. Marginal increases in wound tensile strength (9%) and stress (7%) were observed in the Ga-As laser-treated wounds compared to the controls. No significant changes were found in Young's modulus and energy absorption capacity between the control and laser-treated wounds. Analysis of wound collagen revealed a significant increases in total collagen (14%), salt soluble collagen (31%), acid soluble (14%), and insoluble collagen (50%) with simultaneous decrease in pepsin soluble collagen (19%) in the Ga-As laser-treated wounds compared to controls. Comparisons of these results with the earlier findings revealed that the He-Ne laser appears to be superior to the Ga-As laser, at the parameters of treatment tested, in promoting the wound healing in diabetic rats. Conclusions: The differences in stimulatory effects noted between the He-Ne and Ga-As lasers suggest that the photochemical response the cells for each laser may depend on the wavelength and coherent properties of the electromagnetic radiation. (C) 2003 Wiley-Liss, Inc.